Browsing by Subject "Drug resistance"

Now showing 1 - 14 of 14

Open Access
Deciphering IKBKE involvement in hepatocellular cancer HEPG2 cells
(2020-06) Xhafa, Erta
Hepatocellular 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.
Open Access
Effects of PI3K/AKT/MTOR and VEGFR pathway inhibitors on liver cancer stem cells and bioactivities of novel pyrazolic chalcone derivatives on liver cancer
(2017-12) Kahraman, Deniz Cansen
Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related mortality, such that it the second most frequent cause of cancer death worldwide. Due to its heterogeneous composition and aggressive behavior, it is resistant to conventional therapies and also Sorafenib and Regorafenib which are FDA-approved multikinase inhibitors targeting pathways involved in angiogenesis and proliferation. The mechanisms behind the acquired resistance to Sorafenib were described as activation of compensatory pathways such as PI3K/Akt/mTOR, JAK-STAT, epithelial to mesenchymal transition (EMT), microenvironment and presence of cancer stem cells. Liver cancer stem cells originate from damaged and transformed hepatic progenitor cells (HPCs) which are found responsible for chemo-resistance, tumor relapse, and metastasis. For this reason, the effects of PI3K/Akt/mTOR inhibitors, Sorafenib and DNA intercalators on the enrichment of LCSCs were investigated. CD133+/EpCAM+ population from HCC cells were analyzed by flow cytometry after treatment with inhibitors, and effective inhibitors against LCSCs were further tested for their potential combinatorial effects together with Sorafenib. It was shown that upon treatment with Sorafenib or DNA intercalators the LCSCs were enriched, whereas Rapamycin (mTOR inhibitor), LY294002 (PI3K inhibitor) were able to inhibit the enrichment of LCSCs and reduced the CD133+/EpCAM+ population ratio. Combination studies revealed that when cells are treated initially with Rapamycin and then with Sorafenib, both the LCSC ratio and the sphere formation capacity of cells were reduced compared to cells treated with Sorafenib alone. To understand the alterations in gene expression induced by the inhibitors, a large panel of genes involved in regulation of cancer pathways were analyzed using Nanostring nCounter Technology. Systematic pathway analysis using Cytoscape Score Flow algorithm application allowed us to identify differential response genes involved in stemness. It was shown that genes involved in regulation of stem cells (Wnt and Notch pathway) were downregulated upon treatment with Rapamycin and DAPT (Notch pathway inhibitor), yet Sorafenib treatment resulted in differential regulation of these pathways, where JAG1 gene was found to be up-regulated. Interestingly, IL-8 expression was upregulated dramatically upon treatment with Sorafenib, but downregulated upon DAPT or Rapamycin treatment. Inhibition of IL-8 signaling resulted in reduction in both LCSC ratio and sphere formation capacity of HCC cells, which could be indicating the role of IL-8 signaling in the conservation of stemness features of LCSCs. For this reason, blockade of IL-8 signaling was suggested to be a promising therapeutic approach for HCC. Another topic in this thesis focuses on the potential of VEGFR2 TKIs and quinoids to inhibit both liver cancer cells and liver cancer stem cells. VEGFR TKIs such as Sorafenib, are widely studied for the treatment of many cancers, yet as mentioned above, there are many clinical studies providing the evidence that anti-VEGF or anti-VEGFR therapies lead to stable disease, which is then followed by disease progression in different cancer types. In recent years it has also been shown that antiangiogenic agents are increasing cancer stem cell population via generation of tumor hypoxia. Quinoids, on the other hand, are compounds that are selectively active in hypoxic conditions. Thus, the main aim of this study was to evaluate the bioactivities of compounds from each group on liver cancer cells and also to analyze their effects on the enrichment of LCSCs. Our results have shown that VEGFR2 TKIs were cytotoxic at lower concentrations compared to quinoids. However, it was shown that VEGFR2 TKIs are more likely to enrich LCSC population whereas some of the quinoids were able to reduce this ratio. With this information, a new concept called “aggressiveness factor”, which defines the potential of a compound to cause more aggressive cancer, was introduced. In the last part of this thesis, bioactivities of pyrazolic chalcone derivatives on HCC cell lines and their mechanism of action were investigated. Chalcones and pyrazolic structures are well known for their anti-cancer activities. Newly synthesized pyrazolic chalcone derivatives were tested against different cancer cells, and selection based on the IC50 values of compounds was made to analyze their effect on a panel of HCC cells. Results have shown that, compounds 39, 42, 49 and 52 were the most effective derivatives which had anti-proliferative activities in less than 5 μM concentrations. Further investigation of cell cycle progression and cell death mechanisms have revealed that compounds 42 and 52 caused cell cycle arrest at the G2/M phase and induced apoptotic cell death. Also, levels of cell cycle proteins, p21, CDK1, and phospho-CyclinB1 were shown to decrease upon treatment with these compounds.
Open Access
Elucidating the mechanisms of T-DM1 resistance in in vitro models of HER2 overexpressing breast cancer
(2016-09) Saatci, Özge
Despite the presence of plethora of anti-cancer therapeutics with a variety of different mechanisms of action, it is still not possible to completely eradicate cancer due largely to the occurrence of refractory tumors even years after completion of the treatment. Such “resistant” tumors are formed over time as few cells, which have gained some advantageous genomic alterations eventually populate the entire organ. A lot of in vitro and in vivo studies are currently being done in order to identify the ways by which cancer cells become resistant to given therapy. This would decipher the weaknesses of the resistant tumors and would provide a means to combat drug resistance. T-DM1 is an anti-HER2 therapeutics, being used in refractory HER2-positive breast cancer patients since 2013. It initially generated a huge excitement owing to the highly favorable clinical findings; however, resistance was developed rapidly after 5-6 months following the initial treatment. Currently; very little is known about the mechanisms of acquired resistance against T-DM1, and therefore, identification of novel targets for the treatment of T-DM1 refractory patients would be highly beneficial. In this thesis, I have developed and characterized the acquired T-DM1 resistance phenotypically, and demonstrated abrogation of drug induced mitotic arrest and apoptosis as two novel mechanisms of resistance. I have further analyzed the genomic landscape of resistance in terms of the enrichment of cancer related processes. Cell cycle was found to be the most significantly enriched process among genes deregulated in T-DM1 resistance as identified by next-generation RNA sequencing. Cell cycle was also shown to be activated in TCGA patients expressing high levels of the TDM1 resistance signature and further supported the importance of rewiring cell cycle for the acquisition of T-DM1 resistance in patients as well. I have further identified two important mitotic genes; PLK1 and TACC3 as the common mediators of resistance in different HER2-overexpressing models by a targeted siRNA screen. I have showed that their genomic or pharmacological inhibition confers sensitization to T-DM1 induced growth inhibition, partially through re-induction of apoptotic cell death. I further uncovered a BCL2 dependency in T-DM1 resistant models which was also found to be associated with T-DM1 resistance as inhibition of Bcl2 enhanced T-DM1 induced growth inhibition. Since T-DM1 refractory HER2-positive breast cancer patients are currently not curable, these pre-clinical findings might guide the future clinical test to improve the survival of this patient subgroup via the usage of PLK1 or BCL2 inhibitors in combination with T-DM1.
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
Identification of long non-coding RNAs overcoming tamoxifen resistance in estrogen receptor alpha positive breast cancer
(2017-09) Bal, Hilal
Most of the breast cancer incidences all over the world fall into Estrogen Receptor alpha (ERα)-positive breast cancer subtype, which are treated with endocrine therapy. Tamoxifen, a selective ER modulator drug, is the most prescribed endocrine therapy option for the patients, providing a decreased mortality rate. Although patients respond to tamoxifen well initially they may lose their sensitivity to tamoxifen and develop resistance which is a major obstacle when tackling ERα-positive breast cancer. Global transcriptome analyses performed in recent years demonstrated that most parts of the genomic DNA that are transcribed into RNA are not further translated into proteins. RNA molecules that are not converted into proteins and are therefore called non-coding RNAs (ncRNA) were found to be involved in cellular processes like sequence-specific chromosome modifications, gene silencing and regulation of protein signaling pathways. While the roles of protein and microRNA (miRNA) regulators in the tamoxifen resistance have been identified, the roles of long non-coding RNAs in tamoxifen resistance are still elusive. To elucidate the impact of the long non-coding transcripts in tamoxifen resistance, I have developed acquired tamoxifen resistant ERα-positive cell line models and examined alterations in their transcriptome with respect to long non-coding RNA expression. The results of whole genome RNA-Seq analysis showed that 330 long non-coding transcripts were differentially expressed in the tamoxifen resistant cell line compared to its parental counterpart. I filtered-out ncRNAs according to criteria based on fold change, cancer association, and being a validated lncRNA, and I ended up with two candidate lncRNAs. Here, I continued with the upregulated candidate lncRNA and confirmed its elevated expression by qRT-PCR in both of the in vitro acquired tamoxifen resistant cell line models I used. Moreover, I showed that knockdown of the candidate lncRNA using antisense oligonucleotide (ASO) re-sensitizes resistant cells to tamoxifen. This sensitization effect of candidate lncRNA was achieved via induction of autophagy shown by increased LC3 II/LC3 I ratio followed by apoptosis evidenced by cleaved Caspase 7 when the lncRNA was targeted. Finally, analysis of tamoxifen-treated, ERα-positive breast cancer patient data sets suggested that higher expression of the candidate lncRNA was associated with poor overall, relapse-free and disease-free survival of the patients. Overall, in this thesis, I identified a novel lncRNA regulator of tamoxifen resistance and a potential biomarker of therapy response.
Open Access
Identifying TBK1-specific roles in colorectal cancer
(2022-06) Bagheralmoosavi, Servin
Colorectal 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.
Open Access
Investigation of novel RNAi and nanoparticle approaches for their anti-proliferative and drug-sensitizing effects in breast cancer
(2017-08) Jahja, Ermira
Drug resistivity remains a major challenge in treating different cancer types. Among several strategies adapted to increase drug sensitivity in breast cancer cells, in the present thesis I studied an RNAi molecule targeting cholinergic receptor nicotinic alpha 5 subunit (CHRNA5) and a red-emitting oligomer nanoparticle, the two agents which I experimentally identified as negative regulators of cell proliferation. Cholinergic signaling is implicated in several different pathologies including cancer. Nicotinic acetylcholine receptors (nAChRs) are shown to be involved in regulation of cell proliferation, however they are mainly studied as mediators of nicotinic activity. CHRNA5 subunit has been shown to have roles in acetylcholine (ACh) production/stability, drug addiction and susceptibility to lung cancer. Few studies of lung and gastric cancers as well as high throughput RNAi screens show CHRNA5 as a modulator of cell proliferation. In the present study multiple CHRNA5 isoforms were cloned from MCF7 breast cancer cells (ER positive, TP53 positive) as in the case of lung cancer; moreover, a significant antimitotic effect of CHRNA5 RNAi application was demonstrated in MCF7 breast cancer cells. Similar effect of CHRNA5 silencing was only partially observed in BT-20 and MDA-MB-231 cells (ER negative, P53 mutant), yet in a seeding density-dependent manner. For the first time in literature the transcriptomic changes associated with CHRNA5 RNAi in the MCF7 cells were studied by microarrays from which differentially expressed gene lists were used to obtain the affected pathways. Additional assays confirmed the reduction in cell viability, DNA synthesis, G1 growth arrest, and changes in cytoskeleton complementing the microarray studies. Use of camptothecin (CPT) and doxorubicin (DOXO) in the absence or presence of CHRNA5 siRNA in MCF7, led to identification of CHRNA5’s role in drug sensitivity. Comparisons between CHRNA5 siRNA and public microarray datasets revealed common genes/networks between topoisomerase (TOPO)/cyclin-dependent kinase (CDK) inhibitors and CHRNA5 depletion profile in MCF7 cells. mRNA-miRNA network analysis of differentially expressed common gene sets between TOPO inhibitors and CHRNA5 RNAi treatment identified potential common regulatory miRNAs. In an independent study the anti-cancer as well as drug sensitivity associated effects of a novel CB7-capped, red-emitting conjugated oligomer nanoparticle (Red-CON) were characterized in MCF7 and MDA-MB-231 cells. Red-CON in its encapsulated form exhibited low toxicity and good efficacy as a drug delivery system. This nanoparticle formulation might serve well for future clinical and less toxic chemotherapeutic regimens.
Open Access
Investigation of PI3K functional compensation VIA activated tyrosine kinases
(2020-12) Demir, Melike
Protein tyrosine kinases and serine-threonine kinases have crucial functions in cell signaling, differentiation, motility, and proliferation. PI3K is the most deregulated pathway in human cancers and an essential regulator of cellular proliferation. PI3K pathway is activated via oncogenic Ras/receptor tyrosine kinases (RTKs), PTEN loss, or activating mutations in PI3Ks. Moreover, PI3K is one of the most promising pathways for targeted therapies. Thus, many serine-threonine or tyrosine kinases contribute to drug resistance elicited by PI3K inhibition. In order to identify an individual tyrosine kinase that contributes to PI3K functional compensation, the activated tyrosine kinase library was screened and found out that ZAP70 can compensate growth upon PI3K abrogation. This study suggests a mechanism of activated ZAP70 mediated partial resistance in MEFs lines. Moreover, we demonstrated the role of activated tyrosine kinase, ZAP70, in cancer cells as a tumorinitiating factor. Activated ZAP70 is able to enhance the growth ability of untransformed cells. Also in these cells, activated ZAP70 can develop partial resistance to PI3K inhibition. This resistance occurs via activated downstream targets of tyrosine kinase signaling such as STAT3/MAPK axis. Furthermore, we showed that activated ZAP70 has a high transformation capability associated with the formation of malignant phenotype in untransformed cells. Overall, ZAP70 may be a potent driver of proliferation and transformation in untransformed cells as well as in cancer cells.
Open Access
Investigation of resistance mechanisms in response to PIK3CA inhibition in breast cancer
(2020-12) Tarman, İbrahim Oğuzhan
Breast cancer is the most frequently diagnosed cancer type, accounting for 25% of total cancer cases. PI3K pathway is the most deregulated pathway in breast cancer. Therefore, many inhibitors have been developed for druggable pathway constituents. PIK3CA, which codes for p110α catalytic domain of PI3K, is often found to be mutated in breast cancer patients, resulting in overactivation of PI3K signaling. Recent FDA approval of Alpelisib (BYL719), a p110α-specific small molecule inhibitor, has proven to be effective in hormone receptor positive advanced or metastatic breast cancer patients with activating PIK3CA mutations. Despite its superior efficacy compared to pan-PI3K inhibitors, therapy resistance is still the major problem. AKT has been viewed as the main kinase that relays oncogenic PI3K signal further downstream. Recent studies have revealed readily known kinases that function independent of AKT to be involved in PIK3CA resistance in a PI3K-dependent manner. In this study, we aimed to identify novel molecular targets within the PI3K pathway, but signal in an AKT-independent manner that can confer resistance to PIK3CA inhibition. Our bioinformatical analyses identified STK10 as a potential candidate. STK10 knockdown was able to sensitize breast cancer cells to BYL-719 and induce cell growth in untransformed cell. Moreover, we developed BYL-719 resistant Luminal A subtype breast cancer cell lines to further study additional mechanisms of resistance. Our resistant cell line models had sustained AKT, S6 and 4EBP1 phosphorylation compared to wild-type counterparts under BYL-719 inhibition. Future transcriptomic and proteomic analyses to be performed on these cell lines will provide new insights on BYL-719 resistance mechanisms and help identify novel molecular targets for new therapeutic approaches in combatting BYL-719 resistance in patients.
Open Access
MicroRNas: master regulators of drug resistance, stemness and metastasis
(Springer Berlin Heidelberg, 2014-04) Raza, U.; Zhang, J. D.; Şahin, Ö.
MicroRNAs (miRNAs) are 20-22 nucleotides long small non-coding RNAs that regulate gene expression post-transcriptionally. Last decade has witnessed emerging evidences of active roles of miRNAs in tumor development, progression, metastasis, and drug resistance. Many factors contribute to their dysregulation in cancer, such as chromosomal aberrations, differential methylation of their own or host genes' promoters and alterations in miRNA biogenesis pathways. miRNAs have been shown to act as tumor suppressors or oncogenes depending on the targets they regulate and the tissue where they are expressed. Because miRNAs can regulate dozens of genes simultaneously and they can function as tumor suppressors or oncogenes, they have been proposed as promising targets for cancer therapy. In this review, we focus on the role of miRNAs in driving drug resistance and metastasis which are associated with stem cell properties of cancer cells. Furthermore, we discuss systems biology approaches to combine experimental and computational methods to study effects of miRNAs on gene or protein networks regulating these processes. Finally, we describe methods to target oncogenic or replace tumor suppressor miRNAs and current delivery strategies to sensitize refractory cells and to prevent metastasis. A holistic understanding of miRNAs' functions in drug resistance and metastasis, which are major causes of cancer-related deaths, and the development of novel strategies to target them efficiently will pave the way towards better translation of miRNAs into clinics and management of cancer therapy. © 2014 Springer-Verlag Berlin Heidelberg.
Open Access
miR-200c: a versatile watchdog in cancer progression, EMT, and drug resistance
(Springer Verlag, 2016-06) Mutlu, M.; Raza, U.; Saatci, Ö.; Eyüpoğlu, E.; Yurdusev, E.; Şahin, Ö.
MicroRNAs (miRNAs) are 20–22-nucleotide small endogenous non-coding RNAs which regulate gene expression at post-transcriptional level. In the last two decades, identification of almost 2600 miRNAs in human and their potential to be modulated opened a new avenue to target almost all hallmarks of cancer. miRNAs have been classified as tumor suppressors or oncogenes depending on the phenotype they induce, the targets they modulate, and the tissue where they function. miR-200c, an illustrious tumor suppressor, is one of the highly studied miRNAs in terms of development, stemness, proliferation, epithelial-mesenchymal transition (EMT), therapy resistance, and metastasis. In this review, we first focus on the regulation of miR-200c expression and its role in regulating EMT in a ZEB1/E-cadherin axis-dependent and ZEB1/E-cadherin axis-independent manner. We then describe the role of miR-200c in therapy resistance in terms of multidrug resistance, chemoresistance, targeted therapy resistance, and radiotherapy resistance in various cancer types. We highlight the importance of miR-200c at the intersection of EMT and chemoresistance. Furthermore, we show how miR-200c coordinates several important signaling cascades such as TGF-β signaling, PI3K/Akt signaling, Notch signaling, VEGF signaling, and NF-κB signaling. Finally, we discuss miR-200c as a potential prognostic/diagnostic biomarker in several diseases, but mainly focusing on cancer and its potential application in future therapeutics.
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.
Open Access
Non-coding RNAs as emerging players in the development, diagnosis, and treatment of cancer
(Frontiers Research Foundation, 2024-07-23) Golla, Upendarrao; Chachoua, Ilyas
Open Access
Predictive gene signature for pyrazolopyrimidine derivative c-Src inhibitor 10a sensitivity in melanoma cells
(American Chemical Society, 2020-02) Kücükkaraduman, Barış; Türk, C.; Fallacara, A. L.; Şenses, K. M.; Ayyıldız, Z. O.; Akbar, Muhammad W.; Lotem, Michal; Botta, M.; İşbilen, M.; Güre, Ali O.
Melanoma is a highly aggressive cancer with poor prognosis. Although more than 80% of melanomas harbor an activating mutation in genes within the MAPK pathway, which are mutually exclusive, usefulness of therapies targeting MAPK pathway are impeded by innate and/or acquired resistance in most patients. In this study, using melanoma cells, we report the efficacy of a recently developed pyrazolo[3,4-d]pyrimidine derived c-Src inhibitor 10a and identify a molecular signature which is predictive of 10a chemosensitivity. We show that the expression of TMED7, PLOD2, XRCC5, and NSUN5 are candidate biomarkers for 10a sensitivity. Although an undifferentiated/mesenchymal/invasive status of melanoma cells is associated with resistance to 10a, we show here for the first time that melanoma cells can be sensitized to 10a via treatment with valproic acid, a histone deacetylase inhibitor.