The target therapy of ovarian clear cell carcinoma

Review the progression of ovarian clear cell carcinoma from the perspective of genomics and epigenomics

Ovarian clear cell carcinoma (OCCC) is a rare subtype of epithelial ovarian cancer with unique molecular characteristics, specific biological and clinical behavior, poor prognosis and high resistance to chemotherapy. Pushed by the development of genome-wide technologies, our knowledge about the molecular features of OCCC has been considerably advanced. Numerous studies are emerging as groundbreaking, and many of them are promising treatment strategies. In this article, we reviewed studies about the genomics and epigenetics of OCCC, including gene mutation, copy number variations, DNA methylation and histone modifications.

Effective Disease Control After Combinatorial Treatment with a PD-1 Antibody and an mTOR Inhibitor for Recurrent Ovarian Clear Cell Carcinomas: A Case Report and Literature Review

Ovarian clear cell carcinoma (OCCC) is a rare type of epithelial ovarian cancer characterized by a chemoresistant phenotype and high-grade tumor. Conventional therapies for OCCC include surgery and chemotherapy. However, these OCCC treatment approaches are characterized by a high risk of relapse and drug resistance resulting in poor prognosis. Therefore, alternative therapeutic approaches are required to achieve better outcomes. In this study, a PIK3CA p.R88Q mutation and PD-L1 expression with a tumor proportion score of 10% was explored in a patient who presented with rapid recurrence after surgery and unsuccessful postoperative chemotherapy. Based on the clinical condition and the patient preference, she was administered a novel combinatorial therapy comprising mTOR inhibitor everolimus, which is a well-known and potent inhibitor of the PI3K/AKT signaling pathway, and the anti-PD-1 antibody toripalimab. Treatment with this combinatorial therapy showed good prognosis, with more than eight months of disease control, and no severe adverse events were observed. The findings of this study provide a novel and effective strategy for OCCC patients. To the best of our knowledge, this is the first study to report a new combination regimen of immunotherapy (everolimus plus toripalimab) for solid tumors. Everolimus is not only an antitumor targeted drug but also an immunosuppressant; it’s combination with immunotherapy is controversial. This is the first report to demonstrate that it has a synergistic effect.

Updates of Pathogenesis, Diagnostic and Therapeutic Perspectives for Ovarian Clear Cell Carcinoma

Ovarian clear cell carcinoma (OCCC) is a special pathological type of epithelial ovarian carcinoma (EOC) and has a high prevalence in Asia without specific molecular subtype classification. Endometriosis is a recognized precancerous lesion that carries 3-fold increased risk of OCCC. Ovarian endometrioid carcinoma, which also originates from endometriosis, shares several features with OCCC, including platinum resistance and younger age at diagnosis. Patients with OCCC have about a 2.5 to 4 times greater risk of having a venous thromboembolism (VTE) compared with other EOC, and OCCC tends to metastasize through lymphatic vesicular and peritoneal spread as opposed to hematogenous metastasis. There is only mild elevation of the conventional biomarker CA125. Staging surgery or optimal cytoreduction combined with chemotherapy is a common therapeutic strategy for OCCC. However, platinum resistance commonly portends a poor prognosis, so novel treatments are urgently needed. Targeted therapy and immunotherapy are currently being studied, including PARP, EZH2, and ATR inhibitors combined with the synthetic lethality of ARID1A-dificiency, and MAPK/PI3K/HER2, VEGF/bFGF/PDGF, HNF1β, and PD-1/PD-L1 inhibitors. Advanced stage, suboptimal cytoreduction, platinum resistance, lymph node metastasis, and VTE are major prognostic predictors for OCCC. We focus on update pathogenesis, diagnostic methods and therapeutic approaches to provide future directions for clinical diagnosis and treatment of OCCC.

Immunohistochemical Biomarkers as a Surrogate of Molecular Analysis in Ovarian Carcinomas: A Review of the Literature

The term "ovarian carcinoma" encompasses at least five different malignant neoplasms: high-grade serous carcinoma, low-grade serous carcinoma, endometrioid carcinoma, mucinous carcinoma, and clear cell carcinoma. These five histotypes demonstrated distinctive histological, molecular, and clinical features. The rise of novel target therapies and of a tailored oncological approach has demanded an integrated multidisciplinary approach in the setting of ovarian carcinoma. The need to implement a molecular-based classification in the worldwide diagnostic and therapeutic setting of ovarian cancer demanded a search for easy-to-use and cost-effective molecular-surrogate biomarkers, relying particularly on immunohistochemical analysis. The present review focuses on the role of immunohistochemistry as a surrogate of molecular analysis in the everyday diagnostic approach to ovarian carcinomas.

Current and future strategies for treatment of ovarian clear cell carcinoma

Ovarian clear cell carcinoma (OCCC) is one of the five histological types of epithelial ovarian cancer (EOC). OCCC comprises 23% of all EOC cases in Japan, whereas the rate of OCCC in North America and Europe is much lower. OCCC is generally categorized as a rare gynecologic malignancy, and there is limited evidence for specific treatment. The clinical basis for treatment of OCCC is mostly based on retrospective studies, many of which were performed in Japan. Until recently, most randomized clinical trials for EOC have included OCCC; therefore, current treatment for OCCC is basically the same as that for other histologic types of EOC. However, the clinical characteristics of OCCC differ from those of high-grade serous carcinoma, particularly for chemosensitivity, and there is a need to develop new treatment for OCCC. The molecular background of OCCC has unique features: tumors are usually negative for p53 mutations and positive for ARID1A and/or PIK3CA mutations, whereas p53 mutations are common in high-grade serous or endometrioid carcinomas. These features may help in development of new treatment for OCCC. In this review, we described the current evidence for treatment of OCCC, including surgery, radiotherapy, chemotherapy, molecular targeted therapy and immunotherapy, and we discuss ongoing clinical trials and preclinical studies of new treatment approaches for OCCC.

The Atypical Protein Kinase C Small Molecule Inhibitor ζ-Stat, and Its Effects on Invasion Through Decreases in PKC-ζ Protein Expression

Ovarian cancer is estimated to reach 22,530 diagnoses and cause 13,980 cancer deaths per year. The most common histology diagnosed of ovarian cancer is epithelial ovarian carcinomas (EOC). An aggressive epithelial subtype is clear cell ovarian carcinoma (CCOC) and is characterized as a non-serous ovarian cancer. Protein kinase C (PKC) is an enzymatic family of proteins that have been found to be a component in cancer progression, tissue invasion, and metastasis. The atypical PKC (aPKC) isoforms, PKC-ι and PKC-ζ, have been suggested to participate in the increased proliferation of ovarian cancers. Previous studies have indicated that novel aPKC inhibitors ICA-1S and ζ-Stat decreased the migratory behaviors of colorectal cancer cells and were selective for PKC-ι/λ and PKC-ζ, respectively. The aims of this investigation were to further determine the binding mechanisms of ζ-Stat, expand on the tissue range of these compounds, investigate the therapeutic potential of ζ-Stat in CCOC, and to illustrate the disruption of invasion via the PKC-ζ signaling cascade. The methods utilized were molecular docking and virtual target screening, Western blot analysis, end-point PCR, GST pull down, cell viability and invasion and migration assays. We discovered that the small molecule inhibitor, ζ-Stat, is a prospective drug candidate to investigate as a novel potential treatment for CCOC. We also found that the PKC-ζ/Ect2/Rac1 activation pathway was decreased by ζ-Stat, which in turn decreased invasive behavior of CCOC.

Clinicopathological parameters and survival of invasive epithelial ovarian cancer by histotype and disease stage

Aim: To investigate clinicopathological parameters and histotype-specific survival of epithelial ovarian cancer by stage using the 2014 WHO classification. Patients & methods: Patients were obtained from the SEER database. Multivariate and univariate Cox regression analyses were applied to assess survival outcomes. Results: Irrespective of stages, low-grade serous and endometrioid had the best survival rates. In localized and regional stages, the poorest survival rates were detected for carcinosarcoma and malignant Brenner tumors, but in distant stage, the worst prognoses were observed in mucinous, clear cell and carcinosarcoma (p < 0.05 for all). Conclusion: Our study displayed significant differences in clinicopathological parameters and histotype-specific survival by stages that reflected current consensus on histotype classification and pathogenesis of epithelial ovarian cancer.

Novel Small Molecule MEK Inhibitor URML-3881 Enhances Cisplatin Sensitivity in Clear Cell Ovarian Cancer

Advanced clear cell ovarian cancer (CCOC) is a highly fatal malignancy with a scarcity of effective treatment options. CCOC is inherently chemotherapy resistance, but the exact mechanism of this resistance has yet to be established. Prosurvival signaling, such as through the MAPK cascade, is one way in which cancer cells can evade chemotherapy. We have determined that CCOC exhibits baseline elevated levels of MAPK activity, which increase further upon cisplatin exposure. We have developed a novel MEK inhibitor, URML-3881, to test the effect of MAPK inhibition in CCOC. URML-3881 was found to reduce in vitro CCOC viability through apoptosis and proliferation inhibition, yet it failed to induce in vivo tumor regression. Similarly, cisplatin alone had minimal impact on tumor growth, but remarkably, the combination of MEK inhibition and cisplatin led to a significant and prolonged tumor regression. These studies confirm that the combination of MEK inhibition with URML-3881 and cisplatin is superior to either agent alone in CCOC. Our data support the design of future preclinical and clinical studies into the combination of MEK inhibition and platinum-based chemotherapy as a treatment strategy for CCOC.

Conceptual frameworks of synthetic lethality in clear cell carcinoma of the ovary

Targeting non-oncogenes may result in the selective death of cancer cells. Clear cell carcinoma of the ovary (CCC) may exhibit resistance against conventional chemotherapy and is associated with poor prognosis. The aim of the present report was to review synthetic lethality-based therapies for CCC. Previous English-language studies were reviewed to accumulate preclinical and clinical data on targeting synthetic lethal partners. Synthetic lethal interactions have a variety of types, involving components of a backup or parallel pathway with overlapping functions, components encoded by paralogous pairs, subunit components that form heteromeric complexes and components that are arranged in a single linear pathway. A set of candidate gene targets potentially resulting in synthetic lethality have been previously identified. HNF class homeobox, AT-rich interaction domain 1A, ATR serine/threonine kinase, ATM serine/threonine kinase, checkpoint kinase 1 and phosphatase and tensin homolog may be the key partner genes. A variety of loss of function genes in CCC are driver or passenger events and may function as synthetic lethal pairs under replication stress conditions. Further clinical studies will be required to investigate the safety and therapeutic effect of synthetic lethality pairs in CCC tumor types with replication stress.

Targeting STAT3 by HO3867 induces apoptosis in ovarian clear cell carcinoma

Advanced ovarian clear cell carcinoma (OCCC) carries a very poor prognosis in large part secondary to the extremely high rate of resistance to standard platinum and taxane chemotherapy. Signal transducer and activator of transcription 3(STAT3) expression and activation has been shown to regulate tumor progression in various human cancers, though has not been well studied in OCCC. Preliminary work in our lab has demonstrated constitutive activation of STAT3 (pSTAT3Tyr705 or pSTAT3727) in OCCC cell lines as well as human OCCC tumor tissue samples. Significantly, pSTAT3 is expressed in the absence of other forms of activated STAT (pSTAT1, 2, 6). Therefore, this work was planned to investigate the role of STAT3 and examine the efficacy of a novel anti-cancer compound -HO-3867, which is an inhibitor of STAT3, using known OCCC cell lines. Results demonstrate that treatment with HO-3867 decreased expression of pSTAT3 Tyr705 as well pSTAT3 Ser727, while total STAT3 remained constant. STAT3 overexpression increased the migration capability in OVTOKO cells in vitro and led to an increased tumor size when injected in vivo. The inhibitory effect of HO-3867 on cell proliferation and cell survival was accompanied by increased apoptosis, within 24 h post treatment. Treatment with HO-3867 resulted in a decrease in Bcl-2 and increase of cleavage of caspase 3, caspase 7, and PARP, confirming induction of apoptosis after treatment with HO-3867. In addition, HO-3867 significantly inhibited formation of human umbilical vein endothelial cells capillary-like structures and invasion at both 5 and 10 µM concentrations. STAT3 expression plays an important role in the spread of OCCC in vitro as well as in vivo. Thus, we can exploit the STAT3 pathway for targeted drug therapy. Inhibition of pSTAT3 using HO-3867in OCCC cell lines appears to be a promising therapy. This is of utmost importance given the poor response of OCCC to standard chemotherapy regimens.

The Therapeutic Potential of Targeting the HGF/cMET Axis in Ovarian Cancer

Survival rates for ovarian cancer have remained relatively stable for the past 2 decades despite advances in surgical techniques and cytotoxic chemotherapeutics, indicating a requirement for better therapies. One pathway currently proposed for targeting is the HGF/cMET pathway. Upregulated in a number of tumour types, cMET is a tyrosine kinase receptor expressed on epithelial cells. In ovarian cancer, it has been identified as highly expressed in the four major subtypes, with expression estimates ranging from 11 to 68 % of cases. HGF, the only known ligand for cMET, is found at high levels in both serum and ascites in women with ovarian cancer, and is proposed to induce both migration and metastasis. However, clinically validated biomarkers are not yet available for either HGF or cMET, preventing a clear understanding of the true rate of overexpression, or its correlation with prognosis. Despite this, a number of agents against HGF and cMET are currently being investigated in clinical trials for multiple tumour types, including ovarian. However, a lack of patient selection, biomarker usage, and post hoc analysis correlating response with expression has resulted in the majority of these trials showing little beneficial effect from these agents, indicating that additional research is required to determine their usefulness in patients with ovarian cancer.

Identification of novel mutations in Japanese ovarian clear cell carcinoma patients using optimized targeted NGS for clinical diagnosis

OBJECTIVE

Ovarian clear cell carcinoma (OCCC) is an aggressive ovarian cancer with a higher frequency in Japan and often becomes chemorefractory disease. Reliable genetic diagnosis is essential to affirm the success of precision medicine for OCCC treatment. The aim of this study is, therefore, to identify novel mutations in OCCCs and develop a feasible clinical next generation sequencing (NGS) approach using formalin-fixed paraffin-embedded (FFPE) rather than preferable but not always available fresh frozen (FF) samples.

METHODS

We optimized and evaluated exome analyses of 409 cancer-related genes using FFPE and FF DNA and analyzed NGS data to identify somatic mutations in Japanese OCCCs.

RESULTS

Sufficient and good quality DNAs from FFPE samples were extracted from 18 (FIGO Stage I: 12) out of 29 pairs of matched normal and OCCC for NGS (63%). The fine quality of extracted DNAs depended on the length of storage period (<2years storage). We also identified 45 somatic mutations in 34 genes including unreported variants from those FFPE DNA, in which somatic mutations in the PIK3CA gene was the most common (28%) as previously reported. Seven genes (PIK3CA, ARID1A, CTNNB1, CSMD3, LPHN3, LRP1B, and TP53) were mutated in at least two independent OCCCs. FF samples from 3 out of those 18 OCCCs were available and 13 out of 14 FFPE somatic mutations were confirmed.

CONCLUSIONS

We successfully identified novel genetic alterations in Japanese OCCCs and demonstrated a feasible clinical diagnostic procedure using targeted NGS for OCCC FFPE samples.

Role and mechanism of miR-222 in arsenic-transformed cells for inducing tumor growth

High levels of arsenic in drinking water, soil, and air are associated with the higher incidences of several kinds of cancers worldwide, but the mechanism is yet to be fully discovered. Recently, a number of evidences show that dysregulation of microRNAs (miRNAs) induces carcinogenesis. In this study, we found miR-222 was upregulated in arsenic-transformed human lung epithelial BEAS-2B cells (As-T cells). Anti-miR-222 inhibitor treatment decreased cell proliferation, migration, tube formation, and induced apoptosis. In addition, anti-miR-222 inhibitor expression decreased tumor growth in vivo. We also found that inhibition of miR-222 induced the expression of its direct targets ARID1A and phosphatase and tensin homolog deleted on chromosome 10 (PTEN), and activated apoptosis of As-T cells in part through ARID1A downregulation. These results indicate that miR-222 plays an important role in arsenic-induced tumor growth.

Coumestrol suppresses proliferation of ES2 human epithelial ovarian cancer cells

Coumestrol, which is predominantly found in soybean products as a phytoestrogen, has cancer preventive activities in estrogen-responsive carcinomas. However, effects and molecular targets of coumestrol have not been reported for epithelial ovarian cancer (EOC). In the present study, we demonstrated that coumestrol inhibited viability and invasion and induced apoptosis of ES2 (clear cell-/serous carcinoma origin) cells. In addition, immunoreactive PCNA and ERBB2, markers of proliferation of ovarian carcinoma, were attenuated in their expression in coumestrol-induced death of ES2 cells. Phosphorylation of AKT, p70S6K, ERK1/2, JNK1/2, and p90RSK was inactivated by coumestrol treatment in a dose- and time-dependent manner as determined in western blot analyses. Moreover, PI3K inhibitors enhanced effects of coumestrol to decrease phosphorylation of AKT, p70S6K, S6, and ERK1/2. Furthermore, coumestrol has strong cancer preventive effects as compared to other conventional chemotherapeutics on proliferation of ES2 cells. In conclusion, coumestrol exerts chemotherapeutic effects via PI3K and ERK1/2 MAPK pathways and is a potentially novel treatment regimen with enhanced chemoprevention activities against progression of EOC.

Delphinidin suppresses proliferation and migration of human ovarian clear cell carcinoma cells through blocking AKT and ERK1/2 MAPK signaling pathways

Delphinidin possesses the highest chemopreventive activity among the six components of anthocyanidin that are pigments from fruits and vegetables giving them blue, purple or red colors. Although delphinidin has anti-carcinogenic and apoptotic effects in various cancers, little is known about its functional roles in ovarian clear cell carcinoma (CCC) which shows poor prognosis with resistance to chemotherapy as compared with other subtypes of epithelial ovarian cancers (EOC). Results of present study revealed that cell survival rates of ES2 cells from ovarian CCC treated with delphinidin decreased in a dose-dependent manner. Also, delphinidin inhibited migration and induced apoptosis of ES2 cells. To investigate the molecular mechanisms responsible for biological effects of delphinidin, we analyzed the phosphorylation status of carcinogenic protein kinases related to development of CCC in a dose- and time-dependent manner. Phosphorylation of downstream targets of PI3K (AKT and p70S6K) and MAPKs (ERK1/2 and JNK) signaling was suppressed by treatment of ES2 cells with delphinidin. In addition, pharmacological inhibitors of PI3K/AKT and ERK1/2 MAPK pathway improved the anti-proliferative action of delphinidin on ES2 cells. Moreover, we compared the cancer preventive effects of delphinidin with traditional cisplatin- and paclitaxel-based chemotherapy on cell viability of ES2 cells. Results showed that delphinidin is as effective in its therapeutic activity against ES2 cells as cisplatin and placlitaxel. Collectively, these results indicated that delphinidin plays a critical role as a new chemotherapeutic agent to prevent development and progression of ES2 cells in CCC via inactivation of PI3K/AKT and ERK1/2 MAPK signal transduction cascades.

Potential targets for ovarian clear cell carcinoma: a review of updates and future perspectives

Advances in surgical and medical treatments for ovarian cancer have improved prognoses. Platinum drugs in particular are pivotal for the medical treatment of ovarian cancer. However, previous studies have revealed that some histological subtypes, such as clear cell carcinoma, are resistant to medical treatment, including that with platinum drugs. Consequently, the clinical prognosis of advanced clear cell carcinoma is remarkably inferior, primarily because of its chemoresistant behavior. The prevalence of clear cell carcinoma is approximately 5 % in the West, but in Japan, its prevalence is particularly high, at approximately 25 %. Current medical treatments for advanced clear cell carcinoma are difficult to administer, and they have poor efficacy, warranting the development of novel target-based therapies. In this review, we describe medical treatments for clear cell carcinoma and discuss future prospects for therapy. In particular, we focus on the mechanism of platinum resistance in clear cell carcinoma, including the role of annexin A4, one of the most investigated factors of platinum resistance, as well as the mutant genes and overexpressed proteins such as VEGF, PI3K/AKT/mTOR signaling pathway, ARID1A, hepatocyte nuclear factor-1β, ZNF217. We also review targeted molecular therapeutics for epithelial ovarian cancer and discuss their role in clear cell carcinoma treatment. We review the drugs targeting angiogenesis (bevacizumab, sorafenib, and pazopanib), growth factors (gefitinib, erlotinib, lapatinib, trastuzumab, and AMG479), and signaling pathways (temsirolimus, dasatinib, and imatinib), and other drugs (oregovomab, volociximab, and iniparib). This current review summarizes and discusses the clinical significance of these factors in ovarian clear cell carcinoma as well as their potential mechanisms of action. It may provide new integrative understanding for future studies on their exact role in ovarian clear cell carcinoma.

Ovarian cancer standard of care: are there real alternatives?

Ovarian cancer remains a major issue for gynecological oncologists, and most patients are diagnosed when the disease is already advanced with a poor chance of survival. Debulking surgery followed by platinum-taxane chemotherapy is the current standard of care, but based on several different strategies currently under evaluation, some encouraging data have been published in the last 4 to 5 years. This review provides a state-of-the-art overview of the available alternatives to conventional treatment and the most promising new combinations. For example, neoadjuvant chemotherapy does not seem to be inferior to primary debulking. Despite its outcome improvements, intraperitoneal chemotherapy struggles for acceptance due to the heavy toxicity. Dose-dense chemotherapy, after showing an impressive efficacy in Asian populations, has not produced equal results in a European cohort, and the results of alternative platinum doublets are not superior to those of carboplatin and paclitaxel. In this setting, adherence to a maintenance therapy after first-line treatment and multiple (primarily antiangiogenic) agents appears to be effective. Although many questions, including the duration of maintenance treatment and the use of bevacizumab beyond progression, remain unanswered, new biologic agents, such as poly(ADP-ribose) polymerase (PARP) inhibitors, nintedanib, and mitogen-activated protein/extracellular signal-regulated kinase (MEK) inhibitors, have emerged as potential therapeutic options in the very near future. Based on the multiplicity of available strategies, the histological and molecular features of the tumor, in addition to patient's clinical condition and disease state, continue to gain importance in guiding treatment choices.

Refining prognosis and identifying targetable pathways for high-risk endometrial cancer; a TransPORTEC initiative

This study aimed to investigate whether molecular analysis can be used to refine risk assessment, direct adjuvant therapy, and identify actionable alterations in high-risk endometrial cancer. TransPORTEC, an international consortium related to the PORTEC3 trial, was established for translational research in high-risk endometrial cancer. In this explorative study, routine molecular analyses were used to detect prognostic subgroups: p53 immunohistochemistry, microsatellite instability and POLE proofreading mutation. Furthermore, DNA was analyzed for hotspot mutations in 13 additional genes (BRAF, CDKNA2, CTNNB1, FBXW7, FGFR2, FGFR3, FOXL2, HRAS, KRAS, NRAS, PIK3CA, PPP2R1A, and PTEN) and protein expression of ER, PR, PTEN, and ARID1a was analyzed. Rates of distant metastasis, recurrence-free, and overall survival were calculated using the Kaplan-Meier method and log-rank test. In total, samples of 116 high-risk endometrial cancer patients were included: 86 endometrioid; 12 serous; and 18 clear cell. For endometrioid, serous, and clear cell cancers, 5-year recurrence-free survival rates were 68%, 27%, and 50% (P=0.014) and distant metastasis rates 23%, 64%, and 50% (P=0.001), respectively. Four prognostic subgroups were identified: (1) a group of p53-mutant tumors; (2) microsatellite instable tumors; (3) POLE proofreading-mutant tumors; and (4) a group with no specific molecular profile (NSMP). In group 3 (POLE-mutant; n=14) and group 2 (microsatellite instable; n=19) patients, no distant metastasis occurred, compared with 50% distant metastasis rate in group 1 (p53-mutant; n=36) and 39% in group 4 (NSMP; P<0.001). Five-year recurrence-free survival was 93% and 95% for group 3 (POLE-mutant) and group 2 (microsatellite instable) vs 42% (group 1, p53-mutant) and 52% (group 4, NSMP; P<0.001). Targetable FBXW7 and FGFR2 mutations (6%), alterations in the PI3K-AKT pathway (60%) and hormone receptor positivity (45%) were frequently found. In conclusion, molecular analysis of high-risk endometrial cancer identifies four distinct prognostic subgroups, with potential therapeutic implications. High frequencies of targetable alterations were identified and may serve as targets for individualized treatment.

Rapamycin enhanced the antitumor efficacy of oxaliplatin in cisplatin-resistant ovarian cancer cells A2780cis both in vitro and in vivo

OBJECTIVE

This study aimed to investigate the efficacy of combination of rapamycin, an mammalian target of rapamycin (mTOR) inhibitor for treating rejection after organ transplantation, and oxaliplatin, a third-generation of platinum drug usually used to treat chemoresistant or progressive ovarian cancer, in cisplatin-resistant ovarian carcinoma cells A2780cis.

METHODS/MATERIALS

Expressions of mTOR and its target molecules p70S6K and 4E-BP1 were determined in cisplatin-sensitive and -resistant cells A2780 and A2780cis, respectively, using Western blotting. Proliferation of A2780cis exposure to oxaliplatin or oxaliplatin plus rapamycin was examined using MTT assay in vitro as well as a nude mice model in vivo. Cell apoptosis and proapoptosis proteins including caspase-8 and -3 and PARP were determined using flow cytometry and Western blotting.

RESULTS

We found that A2780cis cells had partial cross-resistance between cisplatin and oxaliplatin. The levels of phosphorylated mTOR (p-mTOR), p70S6K, and 4E-BP1 were significantly increased in A2780cis cells compared to A2780 cells, which might be implicated in cisplatin-induced chemoresistance. Rapamycin obviously enhanced the inhibitory effect of oxaliplatin on the growth of A2780cis both in vitro and in vivo. Rapamycin slightly induced cell apoptosis but significantly enhanced the effect of oxaliplatin in soliciting apoptosis of A2780cis cells, which might be ascribed to its ability in further increasing the levels of cleaved caspase-8 and -3 and PARP induced by oxaliplatin.

CONCLUSION

These results suggested that combination of oxaliplatin and rapamycin enhanced the antitumour efficacy of oxaliplatin in A2780cis cells and therefore might have a role in treating cisplatin-resistant ovarian carcinoma.

The promise and challenge of ovarian cancer models

The complexity and heterogeneity of ovarian cancer cases are difficult to reproduce in in vitro studies, which cannot adequately elucidate the molecular events involved in tumor initiation and disease metastasis. It has now become clear that, although the multiple histological subtypes of ovarian cancer are being treated with similar surgical and therapeutic approaches, they are in fact characterized by distinct phenotypes, cell of origin, and underlying key genetic and genomic alterations. Consequently, the development of more personalized treatment methodologies, which are aimed at improving patient care and prognosis, will greatly benefit from a better understanding of the key differences between various subtypes. To accomplish this, animal models of all histotypes need to be generated in order to provide accurate in vivo platforms for research and the testing of targeted treatments and immune therapies. Both genetically engineered mouse models (GEMMs) and xenograft models have the ability to further our understanding of key mechanisms facilitating tumorigenesis, and at the same time offer insight into enhanced imaging and treatment modalities. While genetic models may be better suited to examine oncogenic functions and interactions during tumorigenesis, patient-derived xenografts (PDXs) are likely a superior model to assess drug efficacy, especially in concurrent clinical trials, due to their similarity to the tumors from which they are derived. Genetic and avatar models possess great clinical utility and have both benefits and limitations. Additionally, the laying hen model, which spontaneously develops ovarian tumors, has inherent advantages for the study of epithelial ovarian cancer (EOC) and recent work champions this model especially when assessing chemoprevention strategies. While high-grade ovarian serous tumors are the most prevalent form of EOC, rarer ovarian cancer variants, such as small cell ovarian carcinoma of the hypercalcemic type and transitional cell carcinoma, or non-epithelial tumors, including germ cell tumors, will also benefit from the generation of improved models to advance our understanding of tumorigenic mechanisms and the development of selective therapeutic options.