Browsing by Subject "EMT"
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Item 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 IlgımATAD2 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.Item Open Access Analysis of the effect of Erbin on the epithelial to mesenchymal transition related genes in breast cancer(2022-09) Şahin, FilizBreast 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.Item Open Access Deciphering IKBKE involvement in hepatocellular cancer HEPG2 cells(2020-06) Xhafa, ErtaHepatocellular carcinoma (HCC) is the second leading cause of cancer related deaths worldwide. The reasons behind high mortality in HCC patients include late diagnosis and lack of therapeutic option. Sorafenib is the only FDA approved systemic therapy for advanced HCC patients but it improves patients’ survival with only 4 months. For this reason, better understanding of the mechanisms of tumor initiation, development and drug resistance in HCC would create new treatment opportunities for HCC patients. In this study, the role of IKKε in HCC tumorigenesis is analysed. HCC development is tightly related to inflammation and IKKε is an inflammation related kinase with very well-known roles in regulating NF-κb and interferon signalling upon viral infection. However, it has also been linked to tumorigenesis of multiple cancers including breast cancer, pancreatic cancer and ovarian cancer. Loss of function models via shRNA or CRISPR/Cas9 are used to study the role of IKKε in HCC tumorigenesis. Depletion of IKKε in HepG2 cells improves the proliferation and anchorageindependent growth of the cells in vitro and it induces a decrease in the expression of EMT markers. Similarly, IKKε depleted HepG2 cells withstand higher doses of Sorafenib, hence, supporting a tumor suppressive potential of IKKε in tumor initiation stages. However, IKKε appears to be involved in EMT and upregulated in EGF and TGFβ1 signalling, two important signalling inducing EMT in HepG2 cells. IKKε is also shown to be upregulated in Sorafenib resistant HepG2 cells where its pharmacological inhibition sensitized Sorafenib resistant HepG2 cells to Sorafenib. These finding show an oncogenic potential of IKKε in later stages of tumor development including metastasis and drug resistance. The results presented in this study suggests a dual role of IKKε in HCC development and drug resistance. Therefore, further mechanistic analysis on this involvement could reveal IKKe inhibition as a potential therapeutic strategy for overcoming Sorafenib resistance in HCC patients.Item Open Access Identification of the roles played by IKKε in hepatocellular and colorectal carcinogenesis(2018-07) Kahya, UğurHepatocellular carcinomas (HCC) and colorectal carcinomas (CRC) are among the most common cancers worldwide with high mortality rates. While HCC affecting mostly underdeveloped countries, CRC is a disease that mainly occur in more developed countries. As is known, CRC is the third most common cancer and the surgical removal of tumors upon early diagnosis is still the best tool in our hands, developing better strategies to cure patients with an advanced CRC has utmost importance. Furthermore, survival rates of HCC patients are very low as a result of poor prognosis and the most efficient therapy for HCC is organ transplantation. Sorafenib, a multikinase inhibitor, is the most effective chemotherapeutic agent in use for HCC leading drug resistance in HCC cells. Thus, alternative strategies should be developed to extend disease-free survival and to treat this cancer. One of the major risk factor for cancer is chronic inflammation and HCC is a good example of inflammation related cancer due to the fact that 90% of HCC cases are stem from inflammation and hepatic injury. As a result of unresolved chronic inflammation, sequential development of HCC occurs from fibrosis and cirrhosis. Moreover, tumor-associated inflammation can encourage tumor development in the gut, indicating central role for inflammation in the development of both sporadic CRC and CAC. In this thesis, our aim was to understand the roles played by IKKε in hepatocellular and colorectal carcinogenesis. Our preliminary bioinformatics analysis with publicly available data has shown high amplification of IKKε in HCC patients in silico. Also, we showed that IKKε plays important roles in HCC cell proliferation and viability. Specifically, upon IKKε depletion, we observed reductions in HCC cell proliferation both in vivo and in vitro. Furthermore, increase epithelial markers upon IKKε loss was suggesting reversed EMT process in HEP3B cells. Consequently, IKKε could be a valuable prognostic biomarker and targeting IKKε may be a potential therapeutic strategy against HCC tumors. On the other hand, in CRC, we demonstrated that IKKε depletion conferred a growth advantage to IKKε depleted DLD1 and SW480 cells and resulted in an increased proliferation in vivo and in vitro, and induced formation of partial-EMT like features in DLD1 cells. Therefore, IKKε complementation may be a valuable potential therapeutic strategy against CRC tumors.Item Open Access Identifying and targeting coding/non-coding molecular switches regulating drug resistance and metastasis in breast cancer(2017-09) Raza, UmarBreast cancer is the second most common cancer and the leading cause of cancer associated deaths in women worldwide. Despite the availability of large number and various types of therapy agents which are effective in limiting tumor burden at initial stages, cancer cells still manage to resist to therapy treatment and exhibit re-growth of existing tumor or metastasize to distant organs. Therefore, there is a dire need to identify underlying molecular mechanisms to enhance therapy response and to block metastasis. In addition to coding genome, non-coding RNAs have also play active role in controlling proliferation, apoptosis, invasion and drug resistance in cancer. Therefore, I aimed to identify novel coding/non-coding molecular switches regulating drug resistance and metastasis in breast cancer. In the first part of this dissertation, I identified miR-644a as a novel tumor suppressor inhibiting both cell survival and epithelial mesenchymal transition (EMT) whereby acting as pleiotropic therapy-sensitizer in breast cancer. Both miR-644a expression and its gene signature are associated with tumor progression and distant metastasis-free survival. Mechanistically, miR-644a directly targets the transcriptional co-repressor C-terminal binding protein 1 (CTBP1) whose knock-outs by the CRISPR-Cas9 system inhibit tumor growth, metastasis, and drug resistance, mimicking the phenotypes induced by miR-644a. Furthermore, miR-644a/CTBP1-mediated upregulation of wild type- or mutant-p53 acts as a ‘molecular switch’ between G1-arrest and apoptosis by inducing p21 or Noxa, respectively. Interestingly, an increase in mutant-p53 by either overexpression of miR- 644a or downregulation of CTBP1 was enough to shift the balance between cell cycle arrest and apoptosis in favor of apoptosis through the upregulation of Noxa. Notably, p53-mutant patients, but not p53-wild type ones, with high CTBP1 level have a shorter survival suggesting that CTBP1 could be a potential prognostic factor for breast cancer patients with p53 mutations. Overall, modulation of the miR-644a/CTBP1/p53 axis may represent a new strategy for overcoming both therapy resistance and metastasis. In the second part of this dissertation, I performed whole transcriptome sequencing with downstream pathway analysis in the chemoresistant triple negative breast cancer (TNBC) tumors we developed in vivo. This suggested a potential role of integrins and hypoxia in chemoresistance. Mechanistically, we showed that our candidate gene is hypoxia-induced and is overexpressed in resistant tumors, and activates integrin subunit alpha 5 (ITGA5). In the meantime, hypoxia-mediated downregulation of a miRNA targeting our candidate gene, leads to further activation of the ITGA5. This culminates in the activation of FAK/Src signaling thereby mediating resistance. Importantly, higher expression of our candidate gene, or lower expression of miRNA was associated with poorer relapse-free survival only in chemotherapy-treated TNBC patients. Finally, inhibition of candidate gene increased the efficacy of chemotherapy in highly aggressive TNBC models in vivo providing pre-clinical evidence for testing inhibitors against our candidate gene to overcome chemoresistance in TNBC patients.Item Open Access Identifying TBK1-specific roles in colorectal cancer(2022-06) Bagheralmoosavi, ServinColorectal cancer (CRC) is the second most lethal cancer type, with a high incidence rate among adults. The CRC is a highly heterogenic disease with a high rate of mutations in different molecular pathways. Moreover, resistance to standard treatment options is seen frequently among CRC patients. Therefore, a better understanding of the mechanisms behind the initiation, progression, and drug resistance allows us to increase the life quality of CRC patients. TBK1 is a kinase protein with central roles in most cellular signaling pathways. This protein has been reported to be an oncogene in some cancer types. However, the role of TBK1 in colorectal cancer is not yet established. In this study, we generated stable TBK1 knockdown CRC cell lines and mainly focused on the role of TBK1 in colorectal cancer pathogenesis. Upon TBK1 depletion in CRC, we observed increased cell proliferation and migration in vitro. The role of TBK1 in cell proliferation is further confirmed in xenograft models in vivo. Moreover, a shift in EMT and resistance to Gefitinib, an EGFR inhibitor, is indicated in TBK1 knockdown cells. TBK1 is also diminished in our Gefitinib-resistant CRC cell lines, suggesting a role for this protein in drug resistance. The findings of this study suggest a tumor-suppressive role for TBK1 in CRC. Hence, further investigations on the mechanisms behind this tumor-suppressive role of TBK1 in CRC will pave the way for developing novel therapeutic options for CRC treatment.Item Open Access IKKs and tumor cell plasticity(Wiley-Blackwell Publishing Ltd., 2018) Göktuna, Serkan İsmail; Diamanti, M. A.; Chau, T. L.Nuclear factor κB (NF-κB) transcription factors are the central hubs of signaling pathways connecting proinflammatory signals to cell survival, proliferation and cytokine production. In cancers, NF-κB signaling influences many aspects of tumor development, from initiation to metastasis. These functions are mediated by tumor-induced plasticity that allows tumor cells to adapt and survive in changing conditions within the tumor microenvironment. Tumor cell plasticity is shaped by the inflammatory microenvironment in tumors. This review focuses on inhibitor of NF-κB kinases, the direct upstream elements of NF-κB regulation, specifically on their conventional and non-conventional functions in animal models of tumorigenesis from the recent literature.Item Open Access The miR-644a/CTBP1/p53 axis suppresses drug resistance by simultaneous inhibition of cell survival and epithelialmesenchymal transition in breast cancer(Impact Journals LLC, 2016) Raza, U.; Saatci, O.; Uhlmann, S.; Ansari, S. A.; Eyüpoglu, E.; Yurdusev, E.; Mutlu, M.; Ersan, P. G.; Altundağ, M. K.; Zhang, J. D.; Dogan, H. T.; Güler, G.; Şahin, Ö.Tumor cells develop drug resistance which leads to recurrence and distant metastasis. MicroRNAs are key regulators of tumor pathogenesis; however, little is known whether they can sensitize cells and block metastasis simultaneously. Here, we report miR-644a as a novel inhibitor of both cell survival and EMT whereby acting as pleiotropic therapy-sensitizer in breast cancer. We showed that both miR-644a expression and its gene signature are associated with tumor progression and distant metastasis-free survival. Mechanistically, miR-644a directly targets the transcriptional co-repressor C-Terminal Binding Protein 1 (CTBP1) whose knock-outs by the CRISPRCas9 system inhibit tumor growth, metastasis, and drug resistance, mimicking the phenotypes induced by miR-644a. Furthermore, downregulation of CTBP1 by miR-644a upregulates wild type- or mutant-p53 which acts as a 'molecular switch' between G1-arrest and apoptosis by inducing cyclin-dependent kinase inhibitor 1 (p21, CDKN1A, CIP1) or pro-apoptotic phorbol-12-myristate-13-acetate-induced protein 1 (Noxa, PMAIP1), respectively. Interestingly, an increase in mutant-p53 by either overexpression of miR-644a or downregulation of CTBP1 was enough to shift this balance in favor of apoptosis through upregulation of Noxa. Notably, p53- mutant patients, but not p53-wild type ones, with high CTBP1 have a shorter survival suggesting that CTBP1 could be a potential prognostic factor for breast cancer patients with p53 mutations. Overall, re-activation of the miR-644a/CTBP1/p53 axis may represent a new strategy for overcoming both therapy resistance and metastasis.Item Open Access Multiomics approaches to overcome drug resistance in cancer(2021-09) Küçükkaraduman, BarışChemotherapy resistance remains one of the major challenges in cancer treatment. Most of the studies on drug resistance have focused on genetic evolution of cancer cells; however, this focus has shifted to non-genetic and epigenetic mechanisms. There is accumulating evidence that mechanisms of drug resistance are not mutually exclusive but instead coexist within a given cancer to develop resistance and therapy failure. Hence, overcoming resistance requires the comprehension of these complex biological processes. Here, we aimed to characterize drug resistance mechanisms by performing both single omics interrogations and multi-omics integrative analysis. For this purpose, we conducted Gene Set Enrichment Analysis (GSEA), functional enrichment analysis on protein-protein interaction (PPI) networks and miRNA-target networks for interpreting gene and miRNA expression data. To gain further biological insights on resistance mechanisms, we focused on identifying a multi-omics molecular signature that discriminates cancer cells based on their drug response profiles. Collectively, these in silico analyses suggested the epithelial-to mesenchymal transition (EMT) as a mediator of 5-FU/irinotecan resistance in colon cancer and irinotecan/gemcitabine resistance in pancreatic cancer. Drug sensitive cancer cells exhibited a more epithelial phenotype with increased cell proliferation. Multi-omics integration analysis revealed some EMT-related genes such as TGM2 and FOSL1, to contribute differential drug response in cancer cells. On the other hand, response of breast cancer cells to doxorubicin exhibited an opposite profile in which mesenchymal phenotype is sensitive while resistant cells have epithelial phenotype. Secondly, we aimed to induce mesenchymal-to-epithelial transition to overcome EMT-mediated drug resistance. We selected eight natural compounds and two re-purposed agents that have been shown to reverse EMT in various studies. We noted transcriptional changes suggesting a shift towards a more epithelial phenotype in 4 out of the 6 cell lines upon treatment with at least one compound tested. None of the natural compounds or re-purposed agents triggered MET in all cancer cells screened. In addition, compounds with clear or slight MET induction did cause these effects in a specific cell line or only in specific cancer type. We investigated next whether the treatment with natural compounds would result in chemosensitization. MET induction by natural compounds is not uniformly related to increased sensitivity to chemotherapeutics but can result in occasional synergistic or additive effects. Lastly, based on cytotoxic activity of a novel c-Src inhibitor 10a in 15 melanoma cells, we report the identification of a new gene signature that can predict chemosensitivity to 10a. Two distinct phenotypes of cells, defined as sensitive and resistant, were further analyzed to reveal an underlying mechanism for this differential response to 10a. We found that proliferative or mesenchymal features of the cells are associated with distinct sensitivity of 10a. Through a protein−chemical interaction network analysis, we identified that three histone deacetylase inhibitors, valproic acid, entinostat, and trichostatin A, were predicted to synergize with 10a. The synergizing effect of valproic acid was validated in vitro. We also aimed to define a minimal number of genes that could be used as biomarkers of 10a sensitivity. We show that the expression level of four genes can be used to predict drug sensitivity against 10a.Item Open Access Prediction of prognosis and chemosensitivity in gastrointestinal cancers(2017-12) Demirkol, SeçilColon and gastric cancers are the third and fifth cancer types with the poorest survival. Surgery is considered the primary treatment option, which can be curative. However the decision as to whether chemotherapy administration after surgery is needed, is critical for especially stage 2 colon cancer; since a group of patients who receive chemotherapy do not have significantly improved clinical outcome. For this purpose, clinical risk factors are currently evaluated to determine patients with a high risk of progression. However this is not standardized by guidelines yet. Therefore, in this thesis my first aim was to ex vivo validate two novel independent mRNA based biomarkers, ULBP2 and SEMA5A, which have been previously identified in our lab, and to generate a prognostic signature which could stratify colon cancer patients with differential prognostic profiles using the best stratification method. I showed that a 3-group prognostic signature, SU-GIB, based on expression of these two genes is associated with cancer-specific, disease-free, and overall survival independent of clinical confounding factors in colon cancer. I performed in silico analysis in order to understand the biological details of the prognostic distinction, and revealed that patients with poorer prognosis show higher expression of pro-inflammatory cytokines and a more mesenchymal profile. Patients with better clinical outcome exhibit a more epithelial profile with higher levels of phosphorylated EGFR and Shc proteins. Analysis of high-throughput drug cytotoxicity databases also showed that colon cancer cell lines with „Bad‟ SU-GIB signature are more sensitive to a dual PI3K-MTOR inhibitor, BEZ235. In this thesis, my second goal was to define prognostic and molecular sub-groups for gastric cancer and characterize the specific biology of each sub-group. Utilizing an unsupervised approach on publicly available microarray data, I identified 3 biological groups, which harbor differential characteristics related to ECM involvement, EMT, proliferation and cell cycle. Moreover I identified distinct prognostic groups which are related to this molecular classification which can further stratify patients with known pathologic subtypes (diffuse and intestinal). I found that EMT was an important parameter for molecular and prognostic classifications for both types of cancers. I therefore, studied high-throughput drug cytotoxicity databases in order to identify selective compounds with selective growth inhibition on epithelial or mesenchymal cancer cells. I identified EGFR inhibitors as being significantly more effective on epithelial cancer cells regardless of the tissue type. My future plans include the large scale validation of SU-GIB, ex vivo validation of the gastric prognostic signature, and in vitro studies that would demonstrate effectivity of EGFR inhibitors on epithelial cancer cells and combination of EGFR inhibitors with MET inducers.Item Open Access Systems-level analysis reveals multiple modulators of epithelial-mesenchymal transition and identifies DNAJB4 and CD81 as novel metastasis inducers in breast cancer(American Society for Biochemistry and Molecular Biology, 2019) Üretmen-Kagıalı, Z. C.; Sanal, E.; Karayel, Ö.; Polat, A. N.; Saatci, Ö.; Ersan, Pelin Gülizar; Trappe, K.; Renard, B. Y.; Önder, T. T.; Tunçbağ, N.; Şahin, Özgür; Özlü, N.Epithelial-mesenchymal transition (EMT) is driven by complex signaling events that induce dramatic biochemical and morphological changes whereby epithelial cells are converted into cancer cells. However, the underlying molecular mechanisms remain elusive. Here, we used mass spectrometry based quantitative proteomics approach to systematically analyze the post-translational biochemical changes that drive differentiation of human mammary epithelial (HMLE) cells into mesenchymal. We identified 314 proteins out of more than 6,000 unique proteins and 871 phosphopeptides out of more than 7,000 unique phosphopeptides as differentially regulated. We found that phosphoproteome is more unstable and prone to changes during EMT compared with the proteome and multiple alterations at proteome level are not thoroughly represented by transcriptional data highlighting the necessity of proteome level analysis. We discovered cell state specific signaling pathways, such as Hippo, sphingolipid signaling, and unfolded protein response (UPR) by modeling the networks of regulated proteins and potential kinase-substrate groups. We identified two novel factors for EMT whose expression increased on EMT induction: DnaJ heat shock protein family (Hsp40) member B4 (DNAJB4) and cluster of differentiation 81 (CD81). Suppression of DNAJB4 or CD81 in mesenchymal breast cancer cells resulted in decreased cell migration in vitro and led to reduced primary tumor growth, extravasation, and lung metastasis in vivo. Overall, we performed the global proteomic and phosphoproteomic analyses of EMT, identified and validated new mRNA and/or protein level modulators of EMT. This work also provides a unique platform and resource for future studies focusing on metastasis and drug resistance.Item Open Access Unmasking of epigenetically silenced genes and identification of transgelin as a potential methylation biomarker in breast cancer(2015-11) Sayar, NilüferTumor suppressor genes (TSG) are frequently silenced in cancer by epigenetic mechanisms, including promoter DNA hypermethylation and repressive chromatin formation by means of histone deacetylation. 5-aza-2'-deoxycytidine (AZA) and Trichostatin A (TSA) are DNA methyl-transferase and histone deacetylase inhibitors, respectively, and are used as anti-cancer agents for induction of epigenetically suppressed genes. In this study, in an attempt to unmask epigenetically suppressed potential TSGs in breast cancer, two breast carcinoma cells and one non-tumorigenic breast cell line were treated with AZA and TSA, either separately or in combination, and with DMSO as control. Afterwards, highthroughput expression profiling revealed significantly affected genes and pathways in response to epigenetic induction in each cell line. Analysis of 32 candidate genes highlighted Transgelin (TAGLN) as a putative TSG that is frequently downregulated by promoter DNA hypermethylation in breast cancer cell lines, and in 61.9% of normal-paired breast tumors according to bisulfite sequencing; and in 63.02% of unpaired breast tumor tissues as determined by bioinformatics analyses of public microarray data. Both relapse-free and overall survivals of patients were more favorable with lower TAGLN methylation. Moreover, TAGLN promoter methylation levels diagnosed tumors tissues with 83.14% sensitivity and 100% specificity. qRTPCR and IHC experiments demonstrated that, TAGLN was persistently downregulated in breast cancer cell lines in comparison to non-tumorigenic cells; and in three independent sets of breast tumor tissues, compared to normal tissues. Furthermore, TAGLN expression was associated with good prognostic factors. Functional analyses in breast cancer cells revealed negative effect of transgelin on colony formation abilities of cells, and analyses with epithelial-to-mesenchymal (EMT) markers implicate an association of transgelin with EMT status of breast cancer. In short, TAGLN downregulation by promoter DNA hypermethylation in breast cancer could serve as a growth advantage to the breast cancer cells, while it could be used as a diagnostic or prognostic biomarker for breast cancer.