Browsing by Subject "Breast cancer"

Now showing 1 - 20 of 55

Open Access
Analysis of CHRNA5 expression in breast cancer cell lines in response to serum starvation and estrogen treatment
(2013) Açıkgöz, Azer Aylin
Breast cancer is a complex disease that can be classified into distinct molecular subtypes including Basal, Luminal A, Luminal B and HER2 positive. These molecular subtypes mainly differ in their hormone receptor expression and response to treatment. This makes the discovery of new molecular markers for further classification important. Cholinergic nicotinic acetylcholine receptors are ion channels involved in smoking behavior, neurodegenerative diseases and cancer. Cholinergic nicotinic receptor alpha 5 (CHRNA5) has been associated with nicotine addiction and recently with lung cancer yet its importance in breast cancer remains relatively unexplored. In the present study, a panel of 10 breast cancer cell lines were used for quantification of isoform-specific CHRNA5 expression using qPCR. Changes in CHRNA5 expression in response to serum starvation and estrogen treatment were assessed. qPCR showed that CHRNA5 was alternatively spliced, with at least five different isoforms in breast cancer cell lines. qPCR analysis for CHRNA5 expression in serum treated and serum starved cells were analyzed after outlier detection and exclusion; and statistical tests included ANCOVA using geometric mean of TPT1 and SDHA, as reference genes. Our results demonstrated that, CHRNA5 expression differed between different subtypes of breast cancer cell lines. CHRNA5 expression significantly responded to serum starvation in ZR75-1 and MDA-MB-157 cell lines, isoform specifically. Isoform expression of CHRNA5 exhibited significant alterations upon estrogen treatment in a dose and time-dependent manner. Expression of 1000bp variant, isoform2 and isoform3 of CHRNA5 significantly increased upon E2 treatment and total CHRNA5 and isoform2 CHRNA5 increased in expression at 24 hours when compared with 12 hours of treatment. Our findings show that CHRNA5 has multiple isoforms in breast cancer, with potential to be modulated by serum starvation and estrogen treatment in a cell-specific manner.
Open Access
Analysis of the ATAD2 gene effect on the genes involved in epithelial mesenchymal transition in estrogen positive and negative breast cancers
(2021-02) Özerk, Zeynep Ilgım
ATAD2 is overexpressed in many distinct cancer types including breast cancer. Its elevated expression is an indicator of poor prognosis. High ATAD2 expression correlates with short overall survival, disease-free survival as well as shorter recurrence-free survival. Moreover, ATAD2 is associated with migration and invasion in some cancer types such as hepatocellular carcinoma and cervical cancer. In breast cancer, ATAD2 expression is higher in invasive tumors. ATAD2 is coactivator of steroid hormone receptor ERα. It directly interacts with ERα and enhances its target genes expressions. ERα is also a regulator of EMT in breast carcinomas. Based on our current knowledge it is proposed that ATAD2 may have a role in EMT and migration capacity of breast cancer cells and this role may be ER dependent as both ATAD2 and EMT are associated with ERα. Bioinformatics analysis revealed that siATAD2 silencing decreased mesenchymal gene expressions significantly in MCF7 and T47D cells. To investigate the possible mesenchymal inducing role of ATAD2, ATAD2 was silenced with shRNA transfection in ER+ MCF7 and T47D cells and ER- mda-mb-231 and sk-br-3 cells. ATAD2 silencing decreased mesenchymal markers expression at both the mRNA and protein level in ER- cells. In ER+ cells, no change in EMT marker proteins and mRNAs were observed with ATAD2 silencing. ER was silenced in ER+ cells and ER silencing introduced a mesenchymal phenotype to them. In this case, ATAD2 silencing reduced this mesenchymal phenotype introduced with ER loss. The EMT effect of the ATAD2 silencing on migration capacity of breast cancer cells was assessed with a scratch assay. Consistent with changes in the epithelial and mesenchymal markers, ATAD2 silencing reduced the migration capacity of mda-mb-231 cells. On the other hand, sk-br-3 migration did not change significantly. In ER+ cells ATAD2 silencing alone had no influence on migratory capacity. ER silencing increased their migration significantly while ATAD2 downregulation in ER-silenced cells suppressed this migration. Over all, this study suggests a possible involvement of ATAD2 in EMT and migration regulation in ER- cells. Targeting ATAD2 in ER- mesenchymal breast cancer cells could be a strategy to reduce their migration capacity.
Open Access
Analysis of the effect of Erbin on the epithelial to mesenchymal transition related genes in breast cancer
(2022-09) Şahin, Filiz
Breast cancer is a heterogeneous disease and has complex mechanisms, which brings the need to come up with different approaches for its various types. Erbin is a member of the LAP family and directly interacts with ErbB2 (HER2), which is a crucial component for breast cancer sub-typing and treatment. Research on the relationship between Erbin and breast cancer showed different results since Erbin was seen to be able to act as both a tumor suppressor and a tumor promoter. There are multiple findings that Erbin has a role in the epithelial to mesenchymal transition in different cancer types. The role of Erbin in EMT is said to be multi-faceted, it affects multiple pathways that act on EMT progress. However, like Erbin’s contradictory role in breast cancer, there are different findings that support the conflicting claims on whether Erbin is an EMT promoter or not. These findings in the literature lead us to analyze how Erbin affects EMT in breast cancer. To investigate if there is a role of Erbin in EMT regulation, we have overexpressed Erbin in MCF7 and silenced Erbin in MDA-MB-231 with MDA-66 cell lines. With this experimental setup, we aimed to see how Erbin plays a role in EMT in both epithelial and mesenchymal cells as well as Luminal A, TNBC, and ER positive breast cancer types. Our results showed that in TGFB induced EMT, Erbin levels are decreased in epithelial cells. Erbin overexpressed MCF7 cells show significant changes in the EMT markers compared to the control group. Experiments conducted with Erbin silenced MDA-MB-231 and MDA-66 cells also demonstrated significant changes in EMT marker levels. Our results suggest that Erbin has a role in EMT in breast cancer, and this role is not limited to one pathway and not streamlined, but possibly a big orchestration of different effects.
Open Access
BO-264: Highly potent TACC3 inhibitor as a novel anticancer drug candidate
(2021-01) Akbulut, Özge
Breast cancer has been consistently ranked to be the most common cancer and the second leading cause of cancer-related death in women worldwide for many years. Despite better understanding of tumor biology and the availability of plethora of anti-cancer therapeutics utilizing different strategies, complete response and/or long-term survival is achieved in only a small fraction of patients with aggressive disease. Since microtubule re-organization is an important step during cell division, drugs that interfere with this process have been a major focus of cancer research. Although anti-microtubule agents are widely used in clinic, cytotoxicity to non-tumorigenic cells and drug resistance are still the main obstacles. Therefore, development of alternative target molecules that selectively and efficiently target cancer cells, but restore normal cells are needed. Transforming acidic coiled-coil containing protein 3 (TACC3) is an important TACC family member, having both mitosis-related roles e.g. regulation of centrosomes and microtubule stability and interphase-related roles e.g. regulation of gene expression and cell migration. Being overexpressed in a broad spectrum of cancers and correlation of its expression with disease progression make TACC3 a highly attractive therapeutic target. Although the oncogenic role of TACC3 has been established albeit mostly in in vitro settings, there is currently no TACC3 inhibitor being tested in clinics. Therefore, by combining rational drug design and screening, we aimed to identify and characterize a novel TACC3 inhibitor hit molecule with high potency and minimum toxicity in in vitro and in vivo systems that is amenable for future drug development. BO-264 was identified as a novel inhibitor targeting TACC3 by direct binding validated by using several biochemical methods, including drug affinity responsive target stability, cellular thermal shift assay, and isothermal titration calorimetry. Compared to two other available TACC3 inhibitors, it showed superior inhibition of mitotic progression and cell viability, especially in aggressive basal and HER2+ breast cancer cell lines. Notably, BO-264 had remarkable cytotoxicity effect on several cancer cell lines in NCI-60 human cancer cell line panel (≥ 90% have less than 1 µM GI50 value) and inhibited the proliferation of FGFR3-TACC3 fusion protein-harboring cells, an oncogenic driver in several malignancies. Importantly, BO-264 did not cause any cytotoxicity to non-cancerous cell lines. Noteworthy, its oral administration significantly suppressed tumor growth in both breast and colon cancer syngeneic and xenograft models, and prolonged survival with no major toxicity. Finally, TACC3 expression level has been identified as a strong independent prognostic factor in breast cancer. Collectively, our preclinical findings suggest that BO-264 is a potent and non-toxic anti-cancer agent targeting TACC3 in breast and colon cancer and can be developed further to obtain better drug-like properties.
Open Access
Characterization of chemosensitivity profiles of breast cancer cell lınes, with and without stem cell like features = Kök-hücre özelliği olan ve olmayan meme kanseri hücre hatlarının ilaç hassasiyet profillerinin tanımlanması
(2014) Akbar, Muhammad Waqas
Breast cancer is the second most common cause of death worldwide from cancer due to complications with its diagnosis and resistance to therapy. Recent studies have shown that breast tumors when compared with other solid tumors also contain a subpopulation termed as cancer stem cells (CSCs). CSCs are hard to kill due to their therapy resistant capacities. These unharmed cells then result into relapse of tumor after treatment. Some established breast cancer cell lines also behave in similar fashion to CSCs in overall manner thus termed as CSC like cell lines. This study primarily focuses on characterizing CSC like cell lines from non CSC like cell lines based upon their gene expression and prediction of drugs which can target these groups separately. In this study two databases, Cancer Cell Line Encyclopedia (CCLE) and Cancer Genome Project (CGP), were used which contain gene expression data and drugs cytotoxicity data for most of the established cancer cell lines. Breast cancer cell lines gene expression data was used to predict two gene lists which can separate breast cancer cell lines into CSC like and non CSC like cell lines by in silico analysis. These gene lists were named as Patentable and Non Patentable. Additionally four drugs were predicted which can target CSC like group (Midostaurin and Elesclomol) and non CSC like group (Panobinostat and Lapatinib) separately. Later these findings were validated in vitro. Non Patentable gene list could not be validated due to low concordance with microarray data. On the other hand, Patentable gene list was validated and was found concordant with microarray data. Out of four selected drugs, Panobinostat and Lapatinib showed increased toxicity to non CSC like cell lines while only Midostaurin showed toxicity to CSC like cell lines. To investigate further that cell lines were grown in 3D cell culture conditions, to increase their stem cell like properties (stemness). But only one cell line MDA-MB-157 which was found as CSC like, showed expected behavior. Additionally this cell line increased resistance to Lapatinib and Panobinostat and became more sensitive to Midostaurin. Correlation analysis showed some genes as potential biomarkers for selected drugs. In conclusion, in this study various genes are proposed to differentiate CSC like cell lines from non CSC like cell lines. And Midostaurin can be potential drug to treat CSC like cells while Lapatinib and Panobinostat showed increased activity against non CSC like cell lines.
Open Access
CHRNA5 belongs to the secondary estrogen signaling network exhibiting prognostic significance in breast cancer
(Springer, 2021-04) Shehwana, Huma; Keskus, Ayse Gokce; Ozdemir, E. Sila; Acikgöz, Azer Aylin; Biyik-Sit, Rumeysa; Cagnan, I.; Gunes, Damla; Jahja, Ermira; Cingir-Koker, Sahika; Olmezer, Gizem; Sucularli, Ceren; Konu, Ozlen
Cholinergic signals can be important modulators of cellular signaling in cancer. We recently have shown that knockdown of nicotinic acetylcholine receptor subunit alpha 5, CHRNA5, diminishes the proliferative potential of breast cancer cells. However, modulation of CHRNA5 expression in the context of estrogen signaling and its prognostic implications in breast cancer remained unexplored.
Open Access
Combinatorial targeting of PI3K and MAPK pathways by miR-564 to inhibit proliferation and invasion in breast cancer
(2016-07) Mutlu, Merve
Breast cancer is among most common malignant tumors worldwide and one of the deadliest cancer types among women. Like other cancer types, dysregulation of signaling pathways is the major cause of uncontrolled cell proliferation, inhibition of apoptosis and eventually metastasis of breast cancer. PI3K and MAPK signaling pathways are among top most deregulated pathways promoting proliferation and invasion in cancer. Clinically approved kinase inhibitors targeting main regulators of these pathways have limited success due to cross-talks between these cascades and creating potential bypass mechanisms. MiRNAs (miRNAs) are 18-22 nucleotides long small non-coding RNAs, functioning by targeting one or more genes simultaneously. The extensive studies on miRNAs showed that they are highly associated with the control of cancer-related processes such as proliferation, migration and invasion. In this thesis, my aim was to identify a potential miRNA functioning as a dual inhibitor of both PI3K and MAPK pathways regulating oncogenic processes in breast cancer. Our previous miRNA mimic screen with reverse phase protein array (RPPA) has been reanalyzed regarding PI3K, MAPK and cell cycle protein regulations. Among top 50 candidate miRNAs, miR-564 was shown to act as a dual inhibitor of PI3K and MAPK pathways in breast cancer cells and inhibiting proliferation through G1 cell cycle arrest. Furthermore, I showed that miR-564 reduces migration and invasion of aggressive breast cancer cells via blocking epithelial-mesenchymal transition (EMT). Direct targeting of AKT2, GNA12, GYS1 and SRF genes in combination may play role in miR-564 being a dual inhibitor of these pathways. Moreover, both high miR-564 expression and low expression of miR-564 target genes were shown to be associated with reduced invasiveness of tumors as well as distant relapse-free survival of breast cancer patients. Overall, I showed that, in addition to being a dual inhibitor of PI3K and MAPK pathways by combinatorial targeting network of genes, miR-564 is a prognostic marker for breast cancer and a promising druggable target.
Open Access
A comprehensive methodology for determining the most informative mammographic features
(2013) Wu, Y.; Alagoz O.; Ayvaci, M.U.S.; Munoz Del Rio, A.; Vanness, D.J.; Woods, R.; Burnside, E.S.
This study aims to determine the most informative mammographic features for breast cancer diagnosis using mutual information (MI) analysis. Our Health Insurance Portability and Accountability Act-approved database consists of 44,397 consecutive structured mammography reports for 20,375 patients collected from 2005 to 2008. The reports include demographic risk factors (age, family and personal history of breast cancer, and use of hormone therapy) and mammographic features from the Breast Imaging Reporting and Data System lexicon. We calculated MI using Shannon's entropy measure for each feature with respect to the outcome (benign/malignant using a cancer registry match as reference standard). In order to evaluate the validity of the MI rankings of features, we trained and tested naïve Bayes classifiers on the feature with tenfold cross-validation, and measured the predictive ability using area under the ROC curve (AUC). We used a bootstrapping approach to assess the distributional properties of our estimates, and the DeLong method to compare AUC. Based on MI, we found that mass margins and mass shape were the most informative features for breast cancer diagnosis. Calcification morphology, mass density, and calcification distribution provided predictive information for distinguishing benign and malignant breast findings. Breast composition, associated findings, and special cases provided little information in this task. We also found that the rankings of mammographic features with MI and AUC were generally consistent. MI analysis provides a framework to determine the value of different mammographic features in the pursuit of optimal (i.e., accurate and efficient) breast cancer diagnosis. © 2013 Society for Imaging Informatics in Medicine.
Open Access
Concomitant inactivation of p53 and Chk2 in breast cancer
(Nature Publishing Group, 2002) Sullivan, A.; Yuille, M.; Repellin, C.; Reddy, A.; Reelfs, O.; Bell, A.; Dunne, B.; Gusterson, B. A.; Osin, P.; Farrell, P. J.; Yulug, I.; Evans, A.; Ozcelik, T.; Gasco, M.; Crook, T.
Open Access
Cytotoxic activity of resveratrol in different cell lines evaluated by MTT and NRU assays
(Turkish Pharmacists Association, 2016) Anlar, H. G.; Bacanli, M.; Kutluk, B.; Başaran, A. A.; Başaran, N.
Oxidative stress is the state of imbalance between the level of antioxidant defence system and production of reactive oxygen species (ROS) and is involded in the progression of several diseases such as inflammation, cancer, neurodegenerative disorders and cardiovascular diseases. It is suggested that plant polyphenols may act as antioxidants and therefore it has anti-cancer activities. Resveratrol (RV), is a naturally occuring polyphenolic compound which is found in many plant species including grapes, nuts, blueberries and raspberries. Data indicated that it has anti-oxidant, anti-inflamatory and anti-cancer activities. But there are also some studies reported that RV has not protective effects aganist cancer. In this study, the cytotoxicity of RV in human breast adenocarcinoma (MDA-MB 231), human cervical cancer (HeLa) and Chinese hamster lung fibroblast (V79) cells were evaluated by Neutral Red uptake assay (NRU) and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assays after incubation at 24 h. We obtained more or the less same results by two cytotoxicity assays. In the concentrations between 2-400 μM, RV seemed not to induce a pronounced cytotoxicity in all cell types. Even at highest concentrations, it showed almost no cytotoxic effects. So the IC50 values were not calculated at the studied concentrations.
Open Access
Detection of microcalcifications in mammograms using local maxima and adaptive wavelet transform analysis
(The Institution of Engineering and Technology, 2002-10-24) Bagci, A. M.; Çetin, A. Enis
A method for computer-aided diagnosis of microcalcification clusters in mammogram images is presented. Microcalcification clusters which are an early sign of breast cancer appear as isolated bright spots in mammograms. Therefore they correspond to local maxima of the image. The local maxima of the image is first detected and they are ranked according to a higher-order statistical test performed over the subband domain data.
Open Access
Development of a shiny application for comparative transcriptomics and differential gene expression analysis
(2022-09) Leka, Ronaldo
RNA sequencing has proven to be an effective technique for divulging information about the transcriptome in molecular biology research. Compared to microarrays and early methods of cDNA sequencing, high-throughput RNA sequencing has better resolution, low background noise, a higher range to quantify gene expression, and relatively lower cost. The development of sequencing technique has led to the development of tools for analyzing the high volume of data that is generated. Statistical methods for normalizing, filtering, performing exploratory and differential analysis, and other functional analyses based on RNA sequencing count data have made RNA sequencing one of the most popular techniques in genomics. To help facilitate the use of such statistical tools, web applications developed in R using the shiny package offer an advantageous environment where researchers can use a graphical interface to give inputs and instructions to the underlying server-side libraries that analyze and generate results in tables and plots. This thesis presents a new tool that has been developed for exploratory analysis, data normalization and filtering, differential gene expression analysis (DGEA), correlation analysis, principal component analysis, and functional analysis such as over-representation analysis and gene set enrichment analysis. When compared to other available applications, this new application offers the ability to run multiple methods for DGEA and compare results between them, leading to the output of gene sets that are discovered as DEGs in multiple tests. Here I present the features of this application in detail where I aim to improve upon the applications that are available in the literature. An example dataset from our lab was also investigated by this RNA-seq tool leading to a better understanding of Mineralocorticoid Receptor (MR) signaling in breast cancer.
Open Access
Development of novel tools for cancer diagnosis, prognosis and treatment using intra- or inter-species transcriptome metaanalysis
(2017-08) Shehwana, Huma
In the past decades, a considerable number of studies have performed meta-analysis on large data collections to prioritize sets of genes, pathways or types/categories of disease focusing on either differential expression, survival analysis, or co-expression networks. However, not many web applications or databases have been developed from these studies thus findings largely remained restricted to the addressed questions and it was not possible for other researchers to use the collected data for the evaluation of novel hypotheses. In this thesis, transcriptomic meta-analysis strategies have been applied to untangle complexities in multiple aspects of cancer research including treatment, diagnosis, and prognosis. Furthermore, three different web-tools have been developed which are not limited to a single type of meta-analysis. In this context, in addition to interesting cancer related findings, novel methodologies have been proposed and tested in the field of meta-analysis and cancer research. First chapter of the thesis presented a general introduction on the concepts of the thesis. Second chapter focused on a pathway comparison strategy based on meta-analysis that was used to reveal concordant/discordant aspects of rapamycin-mediation on transcriptomes of zebrafish and mouse. Analysis has shown that ribosomal terms were significantly upregulated while proteasome was downregulated in both species. Zebrafish has undergone a whole-genome duplication event; I also found out that rapamycin treatment resulted in largely concordant behavior of duplicated gene pairs. In addition, an online database, CompariZome, was developed to evaluate the duplicate zebrafish gene pairs in multiple GEO datasets in zebrafish in comparison to respective human expression datasets. In the third chapter of this thesis, I focused on identification of correlation between a trio of genes, CDH1, HNF4A, and GRHL3, using Cancer Cell Line Encyclopedia (CCLE) dataset to reveal the significance of association between these genes in different cancers, including breast and other epithelial cancers. The findings indicated correlation within the module and has demonstrated the power of meta-analysis using CCLE dataset. In the fourth chapter of this thesis, I focused on understanding the association of CHRNA5, a subunit of cholinergic receptors, with epithelial-to-mesenchymal transition (EMT) as well as epithelial differentiation, TP53 induction, and estrogen (E2) signaling with respect to breast cancer. Meta-analysis of invitro and in-vivo microarray expression datasets showed that CHRNA5, itself, and its positively co-expressed neighbors, were likely secondary targets of E2-signaling; overexpressed in ER- breast cancer patients; and indicators of worse prognosis. Functional annotation revealed that CHRNA5 and its co-expression network was indeed associated with proliferation related pathways. Based on meta-analysis of different cohorts processed in the study, an online database E2S (Estrogen (E2) to Survival) was developed that can facilitate user to query any gene for evaluation of E2-mediated effects, regulation by estrogen receptor (ER), prognostic importance and co-expression network along with functional annotations. In the fifth chapter of this thesis I focused on deciphering the correlation and deregulation between a human parolog pair of genes, i.e., mineralocorticoid and glucocorticoid receptors (MR and GR, respectively) in breast cancer. Meta-analysis of a separate normal/tumor cohort revealed that both genes were downregulated in breast cancer and their expressions were highly positively correlated. However, deregulation analysis predicted that expression of MR and GR was more tightly regulated in normal breast hence its regulation might be lost with the onset of tumorigenesis. Another Shiny database, DualExpBC, was developed to evaluate differential expression of a gene in breast cancer as well as correlation and deregulation of expression between any two input genes in the breast normal/cancer expression cohort. With this thesis, I have developed novel tools and approaches for intra- and inter-species comparative transcriptomics and meta-analysis providing potential diagnostic, prognostic and therapeutic biomarkers.
Open Access
Effects of depletion of CHRNA5 and/or TP53, and transient and stable overexpression of wildtype or mutant TP53 on expression of DLK1-MEG3 locus in MCF7 cells
(2022-09) Arıcı, Burçin İrem
The expression of CHRNA5 has a prominent role in lung cancer and nicotine addiction. Besides, depletion of CHRNA5 has been identified as being tumour suppressive in breast cancer. Moreover, CHRNA5 depletion causes increases in CDKN1A expression, downregulates the 14q32.31 miRNAs and decreases DLK1 expression. This thesis examined the effects of CHRNA5 and/or TP53 downregulation, as well as TP53 overexpression, on the expression of the DLK1-DIO3 region. My findings demonstrated that CHRNA5 depletion decreased the expression of the protein-coding DLK1 and the non-protein coding MEG3 genes in this locus in the presence or absence of TP53. Since these two genes have a vital role in tumour suppression and tumorigenesis, this provided more evidence for the importance of CHRNA5 in the modulation of expression in this locus in breast cancer. Since there is a relation between CHRNA5 and TP53 induction, the expression of one of the main TP53 regulators, MDM2, was also studied. Accordingly, it was found that combining CHRNA5 depletion with TP53 depletion caused a significant decrease in expression in both the MDM2 and MDM2 sequestering elements, PDLIM7 and CDH18. Additionally, the effects of both wild-type and mutant TP53 expression levels on DLK1-MEG3 locus and CHRNA5 were investigated in stable MCF7 breast cancer cells that we have generated. I have found that even if CHRNA5 depletion induced p53 expression, TP53 overexpression did not have CHRNA5-inducing effects regardless of the functionality of TP53. However, wild-type TP53 overexpressing MCF7 cells behaved differently than mutant TP53 overexpressing cells in their DLK1 expression levels. Future research should clarify the effects of CHRNA5 depletion on DLK1-MEG3 region for a given TP53 mutation status.
Open Access
Effects of miR-376 family miRNAs on CHRNA5 depleted MCF7 cell line model and co-culture competition studies
(2019-07) Tiryaki, Rafed Said
Cholinergic receptor nicotinic alpha 5 (CHRNA5) is a ligand-gated ion channel and one of the subunits of nicotinic acetylcholine receptors. Role of CHRNA5 in tumorigenesis has been initially shown in the lung tissue in which higher CHRNA5 expression has been significantly correlated with worse prognosis in lung cancer. In addition, our laboratory members recently shown that CHRNA5 depletion in breast cancer cell line MCF7 is antiproliferative (TUBITAK 111T316). In present study, effects of CHRNA5 depletion on miRNA expression profile were investigated and a significant decrease in the expressions of two members of the miR-376 family miRNAs, miR-376a-3p and miR-376c-3p, were identified. To test the effects of these two miRNAs, mimics were used in combination with CHRNA5 depletion on MCF7 cell line model. To investigate the synergism and/or antagonism of miR-376a mimic with CHRNA5 siRNA treatment a microarray study was performed and the signaling pathways involved were identified. Expressions of genes of interest were tested with RT-qPCR for both miRNAs. In addition, the effects of rescue on the cell phenotype and viability were also studied by using phalloidin staining and MTT experiments, respectively. Next a co-culture-based competition assay was developed using MCF7 cell lines expressing different fluorescent molecules to assess competition by both flow cytometer and fluorescent imaging. In summary, the results revealed that combinational treatments of si-CHRNA5 together with the miRNA mimics of two members from miR-376 family revealed enhancement of the antitumor effects. This study has been supported by TUBITAK (grant no. 114S367).
Open Access
EGF-SNX3-EGFR axis drives tumor progression and metastasis in triple-negative breast cancers
(Nature Publishing Group, 2021-10-30) Çiçek, E.; Çırçır, A.; Öyken, M.; Akbulut Çalışkan, Özge; Dioken, D. N.; Güntekin Ergün, S.; Çetin-Atalay, R.; Sapmaz, A.; Ovaa, H.; Şahin, Ö.; Erson-Bensan, A. E.
Epidermal growth factor receptor (EGFR) has critical roles in epithelial cell physiology. Over-expression and over-activation of EGFR have been implicated in diverse cancers, including triple-negative breast cancers (TNBCs), prompting anti‐EGFR therapies. Therefore, developing potent therapies and addressing the inevitable drug resistance mechanisms necessitates deciphering of EGFR related networks. Here, we describe Sorting Nexin 3 (SNX3), a member of the recycling retromer complex, as a critical player in the epidermal growth factor (EGF) stimulated EGFR network in TNBCs. We show that SNX3 is an immediate and sustained target of EGF stimulation initially at the protein level and later at the transcriptional level, causing increased SNX3 abundance. Using a proximity labeling approach, we observed increased interaction of SNX3 and EGFR upon EGF stimulation. We also detected colocalization of SNX3 with early endosomes and endocytosed EGF. Moreover, we show that EGFR protein levels are sensitive to SNX3 loss. Transient RNAi models of SNX3 downregulation have a temporary reduction in EGFR levels. In contrast, long-term silencing forces cells to recover and overexpress EGFR mRNA and protein, resulting in increased proliferation, colony formation, migration, invasion in TNBC cells, and increased tumor growth and metastasis in syngeneic models. Consistent with these results, low SNX3 and high EGFR mRNA levels correlate with poor relapse-free survival in breast cancer patients. Overall, our results suggest that SNX3 is a critical player in the EGFR network in TNBCs with implications for other cancers dependent on EGFR activity.
Open Access
The exon 13 duplication in the BRCA1 gene is a founder mutation present in geographicaly diverse populations
(Cell Press, 2000) Mazoyer, S.; Leary, J.; Kirk, J.; Fleischmann, E.; Wagner, T.; Claes, K.; Messiaen, L.; Foulkes, W.; Desrochers, M.; Simard, J.; Phelan, C. M.; Kwan, E.; Narod, S. A.; Vahteristo, P.; Nevanlinna, H.; Durando, X.; Bignon, Y. J.; Peyrat, J. P.; Bonnardel, C.; Sinilnikova, O. M.; Puget, N.; Lenoir, G. M.; Audoynaud, C.; Goldgar, D.; Maugard, C.; Caux, V.; Gad, S.; Stoppa-Lyonnet, D.; Noguès, C.; Lidereau, R.; Machavoine, C.; Bressac-De Paillerets, B.; Kuschel, B.; Betz, B.; Niederacher, D.; Beckmann, M. W.; Hamann, U.; Ponder, B. A. P.; Robinson, M.; Taylor G. R.; Bishop, T.; Catteau, A.; Solomon, E.; Cohen, B.; Steel, M.; Collins, N.; Stratton, M.; Van Der Looij, M.; Oláh, E.; Miller, N. J.; Barton, D. E.; Sverdlov, R. S.; Friedman, E.; Radice P.; Montagna, M.; Sensi, E.; Caligo, M.; Van Eijk, R.; Devilee, P.; Van Der Luijt, R.; Heimdal, K.; Møller, P.; Borg, Å.; Diez, O.; Cortes, J.; Domenech, M.; Baiget, M.; Osorio, A.; Benítez, J.; Maillet, P.; Sappino, A. P.; Özdag, H.; Özçelik, T.; Ozturk, M.; Rohlfs, E. M.; Boyd, J.; McDermott, D.; Offit, K.; Unger, M.; Nathanson, K.; Weber, B. L.; Sellers, T. A.; Hampton, E.; Couch, F. J.; Neuhausen, S.; Gayther, S. A.
Recently, a 6-kb duplication of exon 13, which creates a frameshift in the coding sequence of the BRCA1 gene, has been described in three unrelated U.S. families of European ancestry and in one Portuguese family. Here, our goal was to estimate the frequency and geographic diversity of carriers of this duplication. To do this, a collaborative screening study was set up that involved 39 institutions from 19 countries and included 3,580 unrelated individuals with a family history of the disease and 934 early-onset breast and/or ovarian cancer cases. A total of 11 additional families carrying this mutation were identified in Australia (1), Belgium (1), Canada (1), Great Britain (6), and the United States (2). Haplotyping showed that they are likely to derive from a common ancestor, possibly of northern British origin. Our results demonstrate that it is strongly advisable, for laboratories carrying out screening either in English-speaking countries or in countries with historical links with Britain, to include within their BRCA1 screening protocols the polymerase chain reaction-based assay described in this report.
Open Access
Functional analysis of Erbin gene in breast cancer drug resistance
(2021-02) Sunar, Gizem
Erbin is an ERBB2 interacting protein with roles in many signaling pathways. Breast cancer is one of the types of cancer that is affected by Erbin regulation. However, it is unclear how Erbin regulates the biological behavior and drug resistance of breast cancer cells. Some studies have claimed that Erbin promotes tumorigenesis and demonstrates oncogenic features in breast cancer, whereas others have indicated that it inhibits breast cancer development. The main aim of this study was to explore the role of the Erbin gene in breast cancer drug resistance. Bioinformatic analyses of breast cancer patient datasets have shown that a high level of Erbin expression predicts better survival in breast cancer patients treated with chemotherapy or targeted therapies while the Erbin level does not change the survival rates of untreated breast cancer patients. These analyses lead us to hypothesize that the Erbin expression level could alter the effect of the drug treatment and a reduced level of Erbin expression could promote resistance against doxorubicin and tamoxifen. In vitro studies have demonstrated that the protein expressions were apparently lower in MDA-MB-231 doxorubicin resistant (DoxR) and MCF-7 tamoxifen resistant (TamR) cells compared to non-resistant cell line counterparts. When the expression level of Erbin was downregulated by si-RNA transfection, it was observed that the protein level of the anti-apoptotic markers increased whereas apoptotic markers decreased in MDA-MB-231 cells. Proteins that promote cell survival and proliferation increased in Erbin downregulated MDA-MB-231 and MCF-7 cells. Besides, when Erbin was reduced, the viability of the MDA-MB-231 cells against doxorubicin increased but there was no significant change for tamoxifen in MCF-7 cells. Lastly, breast cancer patients with high Erbin expression that were treated with tamoxifen, chemotherapy or trastuzumab have higher levels of DNA damage, apoptosis and cell cycle arrest-related genes. On the contrary, patients with low Erbin expression have higher levels of cyclins, CDKs and anti-apoptotic genes. In conclusion, Erbin could play an important role in the drug resistance of breast cancer cells since the reduction in Erbin expression can promote drug resistance in these cells.
Open Access
Functional effects of ATAD2 gene expression in breast cancer
(2016-08) Özel, Buse Nurten
The ATAD2 gene is a newly investigated gene of which the expression levels are associated with the disease prognosis in many types of cancer and especially breast cancer and that is known to be overexpressed usually through gene amplification and E2F/RB pathway activation. ATAD2 (ATPase family, AAA domain-containing 2) can be overexpressed due to amplification or other regulatory mechanisms in many cancers such as lung, breast, prostate and liver. The fact that ATAD2 has an AAA+ ATPase and bromodomain indicates that it may be a good target for anti-cancer therapy. However, it is necessary to clarify the role of the ATAD2 gene in tumorigenesis before strategies that target ATAD2 are developed. We evaluated a regulator that consistently shows high expression in breast cancer in this study. ATAD2 (ATPase family AAA domain-containing protein 2) is a gene that regulates important cellular activities such as cell proliferation and invasion. This study aimed to clarify the mechanism of action of ATAD2 in breast cancer. The ATAD2 expression of the MCF7 and T47D cell lines with high ATAD2 gene expression was silenced with siRNA and the expression levels of all genes were screened. Gene chip expression analyses revealed that the suppression of ATAD2 in breast cancer cells indicated a role in the regulation of microtubule organization, cell growth, cell adhesion and important signal pathways such as EGFR, FGFR, MAPK, and PI3K. Functional studies with breast cancer cells have supported the gene expression analysis results. Our study revealed that silencing of ATAD2 lead to suppression of ER(-) breast cancer cell migration but not ER(+) cancer cell migration. The same experiments causes a marked decrease in the colony formation capacity and proliferation potential of HCC1937 cells while there was no change in SKBR3 and ER(+) cells. ATAD2 silencing also lead to a senescence response in all breast cancer cells. We investigated the molecular mechanisms of action of ATAD2 to determine the factors underlying the biological effect. The MCF7 and HCC1937 cells were used to clarify its action on the main cellular signal pathways. We found that ATAD2 silencing induced an apoptosis response in both cell types. Intrinsic pathways are activated with caspase-9 cleavage in MCF7 cells while high Bcl2 and BclXL expression prevents caspase-9 cleavage in HCC1937 cells. Decreased ATAD2 did not cause a difference in the p53 protein level in either cells but while p21 expression was increased in just MCF7 cells, RB phosphorylation was inhibited in both cell lines. The results indicate that dysregulation of proteins involved in intracellular control pathways triggers the senescence mechanism. ERα gene expression has been shown to be suppressed as a result of siRNA suppression of ATAD2 gene expression in MCF7 cells. This result indicates that ATAD2 has a role in ERα regulation. ATAD2 gene expression has been found to decrease following Gefitinib suppression of EGFR signaling while EGF treatment of serum-starved MCF7 cells caused increased ATAD2 gene expression. These results indicate that EGFR could be a possible upstream activator of ATAD2. This gene expression pattern also points towards a positive feedback mechanism between ATAD2+ERα and EGFR. Although it is known that EGFR is frequently overexpressed in breast cancer and cross-talk with the estrogen receptor, we do not have detailed information on the mechanism of their interactions. ‘Pathway Enrichment’ analysis of microarray studies have revealed EGFR signaling as one of pathways enriched in the genes downregulated with decreased ATAD2 expression. The silencing of ATAD2 and ERα together prevents EGFR expression in MCF7 cells while silencing of ATAD2 by itself in HCC1937 cells does not cause a change in EGFR expression but prevents its phosphorylation in the Tyr1173 region of the receptor. The ATAD2-suppressed EGFR activity in HCC1937 cells did not lead any change in the Akt level or MEK/ERK activity. The down-stream signaling pathway analysis of the EGFR has revealed that Akt protein expression is suppressed when ATAD2 is silenced in MCF7 cells. The increase in the MEK/ERK signaling activity with decreased ERα expression in the same cells was suppressed with decreased ATAD2 expression. In conclusion, the high expression of the ATAD2 gene in breast cancer stimulates growth of cancer cells while its interaction with the EGFR signaling pathway could be one of the causes of the pro-oncogenic effects of the gene. Its suppression together with EGFR could provide an option for new therapeutic applications in breast cancer studies.
Open Access
Functional genomics in translational cancer research: focus on breast cancer
(Oxford University Press, 2008) Yulug, I. G.; Gur-Dedeoglu, B.
Conventional molecular and genetic methods for studying cancer are limited to the analysis of one locus at a time. A cluster of genes that are regulated together can be identified by DNA microarray, and the functional relationships can uncover new aspects of cancer biology. Breast cancer can be used to provide a model to demonstrate the current approaches to the molecular analysis of cancer. Meta-analysis is an important tool for the identification and validation of differentially expressed genes to increase power in clinical and biological studies across different sets of data. Recently, meta-analysis approaches have been applied to large collections of microarray datasets to investigate molecular commonalities of multiple cancer types not only to find the common molecular pathways in tumour development but also to compare the individual datasets to other cancer datasets to identify new sets of genes. Several investigators agree that microarray results should be validated. One commonly used method is quantitative reverse transcription PCR (qRT-PCR) to validate the expression profiles of the target genes obtained through microarray experiments. qRT-PCR is attractive for clinical use, since it can be automated and performed on fresh or archived formalin-fixed, paraffin-embedded tissue samples. The outcome of these analyses might accelerate the application of basic research findings into daily clinical practice through translational research and may have an impact on foreseeing the clinical outcome, predicting tumour response to specific therapy, identification of new prognostic biomarkers, discovering targets for the development of novel therapies and providing further insights into tumour biology. © The Author 2008. Published by Oxford University Press.