Micro-RNAs associated with the evolution of ovarian cancer cisplatin resistance

Investigation of role of CpG methylation in some epithelial mesenchymal transition gene in a chemoresistant ovarian cancer cell line

Ovarian cancer is one of the lethal gynecologic cancers. Chemoresistance is an essential reason for treatment failure and high mortality. Emerging evidence connects epithelial-mesenchymal transition (EMT) like changes and acquisition of chemoresistance in cancers. Including EMT, DNA methylation influences cellular processes. Here, EMT-like changes were investigated in cisplatin-resistant A2780 ovarian cancer cells (A2780cis), wherein role of DNA methylation in some EMT genes regulations was studied. Cell viability assay was carried out to test the sensitivity of A2780, and A2780cis human cancer cell lines to cisplatin. Differential mRNA expression of EMT markers using qPCR was conducted to investigate EMT like changes. CpG methylation role in gene expression regulation was investigated by 5-azacytidine (5-aza) treatment. DNA methylation changes in EMT genes were identified using Methylscreen assay between A2780 and A2780cis cells. In order to evaluate if DNA methylation changes are causally underlying EMT, treatment with 5-aza followed by Cisplatin was done on A2780cis cells. Accordingly, morphological changes were studied under the microscope, whereas EMT marker's gene expression changes were investigated using qPCR. In this respect, A2780cis cell line has maintained its cisplatin tolerance ability and exhibits phenotypic changes congruent with EMT. Methylscreen assay and qPCR study have revealed DNA hypermethylation in promoters of epithelial adhesion molecules CDH1 and EPCAM in A2780cis compared to the cisplatin-sensitive parental cells. These changes were concomitant with gene expression down-regulation. DNA hypomethylation associated with transcription up-regulation of the mesenchymal marker TWIST2 was observed in the resistant cells. Azacytidine treatment confirmed DNA methylation role in regulating gene expression of CDH1, EPCAM and TWIST2 genes. A2780cis cell line undergoes EMT like changes, and EMT genes are regulated by DNA methylation. To that end, a better understanding of the molecular alterations that correlate with chemoresistance may lead to therapeutic benefits such as chemosensitivity restoration.

Chemotherapy resistance in epithelial ovarian cancer: Mechanisms and emerging treatments

Ovarian cancer (OC) remains a fatal malignancy because most patients experience recurrent disease, which is resistant to chemotherapy. The outcomes for patients with platinum-resistant OC are poor, response rates to further chemotherapy are low and median survival is lower than 12 months. The complexity of platinum-resistant OC, which comprises a heterogeneous spectrum of diseases, is indeed far from being completely understood. Therefore, comprehending tumors' biological behaviour to identify reliable biomarkers, which may predict responses to therapies, is a demanding challenge to improve OC management. In the age of precision medicine, efforts to overcome platinum resistance in OC represent a dynamic and vast field in which innovative drugs and clinical trials rapidly develop. This review will present the exceptional biochemical environment implicated in OC and highlights mechanisms of chemoresistance. Furthermore, innovative molecules and new therapeutic opportunities are presented, along with currently available therapies and ongoing clinical trials.

Association of the Epithelial-Mesenchymal Transition (EMT) with Cisplatin Resistance

Therapy resistance is a characteristic of cancer cells that significantly reduces the effectiveness of drugs. Despite the popularity of cisplatin (CP) as a chemotherapeutic agent, which is widely used in the treatment of various types of cancer, resistance of cancer cells to CP chemotherapy has been extensively observed. Among various reported mechanism(s), the epithelial-mesenchymal transition (EMT) process can significantly contribute to chemoresistance by converting the motionless epithelial cells into mobile mesenchymal cells and altering cell-cell adhesion as well as the cellular extracellular matrix, leading to invasion of tumor cells. By analyzing the impact of the different molecular pathways such as microRNAs, long non-coding RNAs, nuclear factor-κB (NF-ĸB), phosphoinositide 3-kinase-related protein kinase (PI3K)/Akt, mammalian target rapamycin (mTOR), and Wnt, which play an important role in resistance exhibited to CP therapy, we first give an introduction about the EMT mechanism and its role in drug resistance. We then focus specifically on the molecular pathways involved in drug resistance and the pharmacological strategies that can be used to mitigate this resistance. Overall, we highlight the various targeted signaling pathways that could be considered in future studies to pave the way for the inhibition of EMT-mediated resistance displayed by tumor cells in response to CP exposure.

miR-548e Sponged by ZFAS1 Regulates Metastasis and Cisplatin Resistance of OC by Targeting CXCR4 and let-7a/BCL-XL/S Signaling Axis

Ovarian cancer (OC) is a severe malignancy featuring a poor prognosis due to rapid metastasis and chemotherapy resistance. In this study, we extensively investigated the upstream and downstream mechanisms of miR-548e in regulating OC progression and cisplatin resistance. Our results indicated that ZFAS1 was highly expressed and promoted OC cell proliferation, migration, invasion, and cisplatin resistance by directly suppressing miR-548e expression. ZFAS1 co-localized with miR-548e in the cytosols of OC cells. miR-548e repressed CXCR4 expression, and elevated CXCR4 expression promoted OC cell proliferation, migration, invasion, and cisplatin resistance. Cisplatin resistance induced by ZFAS1 and CXCR4 overexpression in OC cells was mediated by their suppression on let-7a and elevation of BCL-XL/S expression. ZFAS1 knockdown and miR-548e and let-7a overexpression impaired cisplatin resistance and suppressed lung metastatic nodule formation in nude mice. In conclusion, ZFAS1 binds with miR-548e to enhance CXCR4 expression to promote OC cell proliferation and metastasis, which also enhances cisplatin resistance by suppressing let-7a and elevating BCL-XL/S protein expression.

Interplay Between MicroRNAs and Oxidative Stress in Ovarian Conditions with a Focus on Ovarian Cancer and Endometriosis

Ovarian cancer and endometriosis are two distinct gynaecological conditions that share many biological aspects incuding proliferation, invasion of surrounding tissue, inflammation, inhibition of apoptosis, deregulation of angiogenesis and the ability to spread at a distance. miRNAs are small non-coding RNAs (19–22 nt) that act as post-transcriptional modulators of gene expression and are involved in several of the aforementioned processes. In addition, a growing body of evidence supports the contribution of oxidative stress (OS) to these gynaecological diseases: increased peritoneal OS due to the decomposition of retrograde menstruation blood facilitates both endometriotic lesion development and fallopian tube malignant transformation leading to high-grade serous ovarian cancer (HGSOC). Furthermore, as HGSOC develops, increased OS levels are associated with chemoresistance. Finally, continued bleeding within ovarian endometrioma raises OS levels and contributes to the development of endometriosis-associated ovarian cancer (EAOC). Therefore, this review aims to address the need for a better understanding of the dialogue between miRNAs and oxidative stress in the pathophysiology of ovarian conditions: endometriosis, EAOC and HGSOC.

The Role of Epithelial-to-Mesenchymal Plasticity in Ovarian Cancer Progression and Therapy Resistance

Ovarian cancer is the most lethal of all gynecologic malignancies and the eighth leading cause of cancer-related deaths among women worldwide. The main reasons for this poor prognosis are late diagnosis; when the disease is already in an advanced stage, and the frequent development of resistance to current chemotherapeutic regimens. Growing evidence demonstrates that apart from its role in ovarian cancer progression, epithelial-to-mesenchymal transition (EMT) can promote chemotherapy resistance. In this review, we will highlight the contribution of EMT to the distinct steps of ovarian cancer progression. In addition, we will review the different types of ovarian cancer resistance to therapy with particular attention to EMT-mediated mechanisms such as cell fate transitions, enhancement of cancer cell survival, and upregulation of genes related to drug resistance. Preclinical studies of anti-EMT therapies have yielded promising results. However, before anti-EMT therapies can be effectively implemented in clinical trials, more research is needed to elucidate the mechanisms leading to EMT-induced therapy resistance.

Circular RNA EIF6 (Hsa_circ_0060060) sponges miR-144-3p to promote the cisplatin-resistance of human thyroid carcinoma cells by autophagy regulation

Anaplastic thyroid carcinoma (ATC) responds for the majority of death of thyroid carcinoma and often causes chemotherapy resistance. We investigated the influence of circEIF6 (Hsa_circ_0060060) on the cisplatin-sensitivity in papillary thyroid carcinoma (PTC) and ATC cells, and explored its regulation to downstream molecules miR-144-3p and Transforming Growth Factor α (TGF-α). Differentially expressed circRNAs in PTC were analyzed using the GSE93522 data downloaded. Expressions of circEIF6, miR-144-3p, TGF-α, autophagy-related proteins and apoptosis-related proteins were determined using qRT-PCR or western blot. RNA pull-down assay and dual luciferase report assay were applied to reveal the target relationships. Autophagy marker LC3 and cell proliferation marker ki67 were evaluated by immunofluorescence and immunohistochemistry. Cell viability was evaluated with MTT assay and cell apoptosis was assessed by flow cytometric analysis. CircEIF6, could promote autophagy induced by cisplatin, thus inhibiting cell apoptosis and enhancing the resistance of PTC and ATC cells to cisplatin. Has-miR-144-3p was the target of circEIF6 and was regulated by circEIF6. Besides, circEIF6 promoted autophagy by regulating miR-144-3p/TGF-α axis, enhancing the cisplatin-resistance in PTC and ATC cells. CircEIF6 promoted tumor growth by regulating miR-144-3p/TGF-α and circEIF6 knock-down enhanced cisplatin sensitivity in vivo. CircEIF6 could provide a target for therapy of cisplatin-resistance in thyroid carcinoma.

MicroRNA-31-5p regulates chemosensitivity by preventing the nuclear location of PARP1 in hepatocellular carcinoma

BACKGROUND

MicroRNAs (miRNAs) posttranscriptionally regulate gene expression and thereby contribute to the modulation of numerous complex and disease-relevant cellular processes, including cell proliferation, cell motility, apoptosis and stress response. miRNA-31-5p is encoded on a genomic fragile site, 9p21.3, which is reportedly lost in many hepatocellular carcinoma (HCC) tumors. Based on previous findings, we hypothesized that miR-31-5p alters chemosensitivity and that miR-31-5p mimics may influence sensitivity to chemotherapeutics in HCC as well as in a variety of other cancers.

METHODS

MiR-31-5p and PARP1 in HCC tissues were tested by RT-PCR and histological analysis, respectively. Next, clonogenic assay and western blot were used to detect miR-31-5p and PARP1 to modulate sensitivity to OXA-based chemotherapy. The distribution of OXA in the nuclear and intracellular was detected by ICP-MS. Coimmunoprecipitation was used to characterize the protein-protein interaction between PARP1 and ABCB9. A xenograft nude mouse model was used to examine the in vivo effects of miR-31-5p.

RESULTS

Reintroduction of miR-31-5p into miR-31-5p-null Hep3B cells significantly enhanced clonogenic resistance to oxaliplatin. Although miR-31-5p re-expression increased chemoresistance, it paradoxically increased the relative intracellular accumulation of oxaliplatin. This effect was coupled with a significantly decreased intranuclear concentration of oxaliplatin by ICP-MS. miR-31-5p prevents the nuclear location of PARP1 detected by immunofluorescence, histological analysis and Western blotting analysis. We subsequently identified an indirect miR-31-5p-mediated upregulation of ABCB9, which is a transporter associated with drug accumulation in lysosomes, along with an increased uptake of oxaliplatin to lysosomes; these phenomena were associated with a downregulation of PARP1, a bipotential transcriptional regulator with multiple miR-31-5p binding sites. However, the indirect overexpression of ABCB9 promoted cellular chemosensitivity, suggesting that miR-31-5p promotes chemoresistance largely via an ABCB9-independent mechanism.

CONCLUSIONS

Overall, our data suggest that the loss of miR-31-5p from HCC tumors promotes chemosensitivity, and this knowledge may be prognostically beneficial in the context of therapeutic sensitivity.

IL-6R/STAT3/miR-204 feedback loop contributes to cisplatin resistance of epithelial ovarian cancer cells

Enhanced chemoresistance is, among other factors, believed to be responsible for treatment failure and tumor relapse in patients with epithelial ovarian cancer (EOC). Here, we exposed EOC cells to interleukin-6 (IL-6) to activate oncogenic STAT3, which directly repressed miR-204 via a conserved STAT3-binding site near the TRPM3 promoter region upstream of miR-204. Repression of miR-204 was required for IL-6-induced cisplatin (cDDP) resistance. Furthermore, we identified the IL-6 receptor (IL-6R), which mediates IL-6-dependent STAT3 activation, as a direct miR-204 target. Importantly, the resulting IL-6R/STAT3/miR-204 feedback loop was identified in patients with EOC, and its activity correlated with chemosensitivity. Moreover, exogenous miR-204 blocked this circuit and enhanced cDDP sensitivity both in vitro and in vivo by inactivating IL-6R/STAT3 signaling and subsequently decreasing the expression of anti-apoptotic proteins. Our findings illustrate the function of this feedback loop in cDDP-based therapy and may offer a broadly useful approach to improve EOC therapy.

Biomarkers of platinum resistance in ovarian cancer: what can we use to improve treatment

Ovarian cancer has poor survival rates due to a combination of diagnosis at advanced disease stages and disease recurrence as a result of platinum chemotherapy resistance. High-grade serous ovarian cancer (HGSOC), the most common ovarian cancer subtype, is conventionally treated with surgery and paclitaxel/carboplatin combination chemotherapy. Initial response rates are 60-80%, but eventually the majority of patients become platinum-resistant with subsequent relapses. Extensive research on individual biomarkers of platinum resistance has revealed many potential targets for the development new treatments. While this is ongoing, there are also epigenetic, DNA repair, genome and immune changes characterised in platinum-resistant HGSOC that can be targeted with current therapies. This review discusses biomarkers of platinum chemotherapy resistance in ovarian cancer with a focus on biomarkers that are targetable with alternative treatment combinations to those currently used. After decades of research focused on elucidating the biological cause of platinum resistance, future research needs to focus on using this knowledge to overcome resistance for patients with ovarian cancer.

Synergism of ursolic acid and cisplatin promotes apoptosis and enhances growth inhibition of cervical cancer cells via suppressing NF-κB p65

Objective

This study was designed to investigate the effect of combination of ursolic acid (UA) with cisplatin (DDP) on cervical cancer cell proliferation and apoptosis.

Methods

The mRNA and protein expressions of nuclear factor-kappa B (NF-κB) p65 in cervical cancer cells were examined using RT-PCR and western blot. MTT and colony formation assays were performed to examine the DDP toxicity and the proliferation ability of cervical cancer cells. Cell morphology was observed by means of Hoechst33258 and transmission electron microscopy (TEM). The apoptosis rate and cell cycle were assessed through flow cytometry assay. Western blot was used to detect the expression of apoptosis-related molecules.

Results

The mRNA and protein expressions of NF-κB p65 in cervical cancer cells were significantly higher than that in cervical epithelial cells. The combined treatment of UA and DDP inhibited cervical cancer cell growth and promoted apoptosis more effectively than DDP treatment or UA treatment alone (P < 0.05). Compared with the DDP group and UA group, the expressions of Bcl-2 and NF-κB p65 in DDP +UA group were decreased, while the expressions of Bax, Caspase-3 and PARP cleavage were observably increased. The expression of nuclear NF-κB p65 significantly reduced in UA group and DDP +UA group. si-p65 group displayed a decrease of cell proliferation ability and led to a significant reduction in the number of SiHa cell colony formation.

Conclusion

The combination of UA with DDP could more effectively inhibit SiHa cells proliferation and facilitate cell apoptosis through suppressing NF-κB p65.

MicroRNA-31 Regulates Chemosensitivity in Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) is associated with an extremely poor prognosis, and most patients initially are or rapidly become unresponsive to platinum-based chemotherapy. MicroRNA-31 (miR-31) is encoded on a genomic fragile site, 9p21.3, which is reportedly lost in many MPM tumors. Based on previous findings in a variety of other cancers, we hypothesized that miR-31 alters chemosensitivity and that miR-31 reconstitution may influence sensitivity to chemotherapeutics in MPM. Reintroduction of miR-31 into miR-31 null NCI-H2452 cells significantly enhanced clonogenic resistance to cisplatin and carboplatin. Although miR-31 re-expression increased chemoresistance, paradoxically, a higher relative intracellular accumulation of platinum was detected. This was coupled to a significantly decreased intranuclear concentration of platinum. Linked with a downregulation of OCT1, a bipotential transcriptional regulator with multiple miR-31 target binding sites, we subsequently identified an indirect miR-31-mediated upregulation of ABCB9, a transporter associated with drug accumulation in lysosomes, and increased uptake of platinum to lysosomes. However, when overexpressed directly, ABCB9 promoted cellular chemosensitivity, suggesting that miR-31 promotes chemoresistance largely via an ABCB9-independent mechanism. Overall, our data suggest that miR-31 loss from MPM tumors promotes chemosensitivity and may be prognostically beneficial in the context of therapeutic sensitivity.

A Feedback Loop Between miR-30a/c-5p and DNMT1 Mediates Cisplatin Resistance in Ovarian Cancer Cells

BACKGROUND

Many microRNAs (miRs) are dysregulated in cancers, and aberrant miR expression patterns have been suggested to correlate with chemo-resistance of cancer cells. We aim to study the role of miR-30 family members in cisplatin-resistance of ovarian cancer cells.

METHODS

qRT-PCR was used to compare differential expression levels of miR-30 family members in ovarian cancer cell line A2780 and its cisplatin-resistant derivative CP70. Changes of cisplatin-sensitivity in miR-30a-5p- and miR-30c-5p-overexpressed-CP70 cells and miR-30a-5p- and miR-30c-5p-inhibited-A2780 cells were examined by CCK8 assay and apoptosis analysis using flow cytometry; targets of miR-30a/c-5p were analyzed by western blotting and luciferase reporter assay; methylation regulation of pre-miR-30a/c-5p was examined by methylation specific PCR.

RESULTS

miR-30a-5p and miR-30c-5p, in contrast to other miR-30 family members, dramatically decreased in cisplatin-resistant CP70 cells due to overexpressed-DNMT1 induced aberrant methylation. miR-30a/c-5p in turn directly inhibited DNMT1 as well as Snail. Forced expression of miR-30a/c-5p or knocking down of DNMT1 and Snail promoted cisplatin susceptibility and partially reversed epithelial-mesenchymal transition (EMT) in CP70 cells, while inhibition of miR-30a/c-5p or ectopic expression of DNMT1 and Snail induced cisplatin resistance and partial EMT in cisplatin-sensitive A2780 cells.

CONCLUSIONS

A feedback loop between miR-30a/c-5p and DNMT1 is a potent signature for cisplatin-resistance and EMT in ovarian cancer, promising a potential target for improved anti-cancer treatment.

Downregulation of Foxo3 and TRIM31 by miR-551b in side population promotes cell proliferation, invasion, and drug resistance of ovarian cancer

Ovarian cancer (OVCa) stem cells are associated with tumor growth, metastasis, and recurrence, which are driving forces behind a majority of the OVCa-related mortality. This subpopulation of cancer cells are characterized by uncontrolled proliferation, high invasiveness, and resistance against the current platinum-based therapy. Thus, targeting OVCa cancer stem cells has been focused in recent therapeutic development. Isolation and purification of cancer stem cells are, however, challenging for the lack of sensitive and specific markers. In this study, we demonstrated that miR-551b was upregulated in OVCa stem cells, by using a quantitative PCR array, correlating with the pathological grades of this malignancy. In vitro experiments indicated that miR-551b promoted the proliferation, invasion, and chemoresistance of OVCa cells and cancer stem cells. Further analysis suggested that miR-551b functioned through the suppression of Foxo3 and TRIM31, two important tumor suppressors. In support of this, our in vivo experiments using mouse xenograft models showed that inhibiting miR-551b significantly increased the susceptibility of OVCa cells to cisplatin and prolonged the survival of the host mice. In conclusion, our study suggested miR-551b as a potential biomarker for OVCa stem cells and explored its functional mechanism, providing a potential therapeutic target for future drug development.

Epithelial-to-Mesenchymal Transition in Paclitaxel-Resistant Ovarian Cancer Cells Is Downregulated by Luteolin

Ovarian cancer (OVCA) is the deadliest of all gynecological cancers which is attributed to late presentation, persistence, and development of chemoresistance. The objectives were to evaluate the association between OVCA paclitaxel-resistance and epithelial-to-mesenchymal transition (EMT) and to determine the capability of luteolin to chemosensitize OVCA cells. X10 and X22 cells were 11.8-25.3-fold and 7.8-8.6-fold resistant to paclitaxel than 1AP cells. X10 and X22 cells exhibited a mesenchymal phenotype, while 1AP has an epithelial characteristics. Furthermore, the expression of the epithelial marker E-cadherin was downregulated, while mesenchymal markers Vimentin and N-cadherin were upregulated in X10 and X22 cells when compared to 1AP cells. Transcription factors Snail, Slug, and Twist1 were upregulated in X10 cells, while Twist1 was highly expressed in X22 cells. Luteolin treatment caused cytotoxicity being most potent to X10 OVCA cells. Treatment of non-cytotoxic dose of luteolin at 15.625 μM chemosensitized X10 and X22 OVCA cells to paclitaxel as evidenced by reduced ED₅₀ values from 11.8 to 0.2 μM and 8.6 to 3.6 μM for X10 and X22 cells, respectively. Moreover, luteolin treatment led to a more epithelial phenotype of X10 and X22 cells and modification of EMT markers indicating reversal of EMT. The mechanism involved is through reduction of phosphorylation of FAK and ERK leading to reduced nuclear translocation of p65. Our results highlight the significance of EMT in OVCA resistance to paclitaxel and warrant the investigation of luteolin as a potential therapeutic agent in chemoresistant OVCA. J. Cell. Physiol. 232: 391-401, 2017. © 2016 Wiley Periodicals, Inc.