A review of the current evidence for maintenance therapy in ovarian cancer

Hormone Receptor Expression in Primary and Recurrent High-Grade Serous Ovarian Cancer and Its Implications in Early Maintenance Treatment

Endocrine therapy is an effective treatment for low-grade serous ovarian cancer. However, the role of estrogen and progesterone receptors as biomarkers for high-grade serous ovarian cancer (HGSOC) is yet to be elucidated because not all estrogen and progesterone receptor-positive tumors benefit from anti-estrogen therapy. The degree of expression is presumed to play a vital role; however, that role is not well-defined in ovarian cancer. We aimed to determine the role of estrogen and progesterone receptor expression in primary and paired relapsed HGSOC. In this study, primary and matched relapsed tumor samples were collected from 80 patients with International Federation of Gynecology and Obstetrics Stage II-IV HGSOC. Tissue microarray was conducted and immunohistochemistry for estrogen and progesterone receptor expression was performed. Two independent pathologists performed the tissue microarray analysis with the Immunoreactive Score and Allred Total score. In the paired analysis, no significant difference in estrogen receptor expression was observed. However, progesterone receptor expression was significantly lower in patients with recurrent platinum-sensitive HGSOC. We conclude that anti-estrogen therapy targeting estrogen receptor positive HGSOC could be administered in primary and relapsed settings. The use of endocrine maintenance with an aromatase inhibitor in patients with estrogen receptor positive HGSOC needs to be further evaluated and validated in a randomized controlled trial.

RCC2, a regulator of the RalA signaling pathway, is identified as a novel therapeutic target in cisplatin-resistant ovarian cancer

Currently, cisplatin (DDP) is the first-line chemotherapeutic agent used for treatment of ovarian cancer, but gradually acquired drug resistance minimizes its therapeutic outcomes. We aimed to identify crucial genes associated with DDP resistance in ovarian cancer and uncover potential mechanisms. Two sets of gene expression data were downloaded from Gene Expression Omnibus, and bioinformatics analysis was conducted. In our study, the differentially expressed genes between DDP-sensitive and DDP-resistant ovarian cancer were screened in GSE15709 and GSE51373 database, and chromosome condensation 2 regulator (RCC2) and nucleoporin 160 were identified as 2 genes that significantly up-regulated in DDP-resistant ovarian cancer cell lines compared with DDP-sensitive cell lines. Moreover, RCC2, Ral small GTPase (RalA), and Ral binding protein-1 (RalBP1) expression was found to be significantly higher in DDP-resistant ovarian cancer tissues than in DDP-sensitive tissues. RCC2 plays a positive role in cell proliferation, apoptosis, and migration in DDP-resistant ovarian cancer cell lines in vitro and in vivo. Furthermore, RCC2 could interact with RalA, thus promoting its downstream effector RalBP1. RalA knockdown could reverse the effects of RCC2 overexpression on DDP-resistant ovarian cancer cell proliferation, apoptosis, and migration. Similarly, RalA overexpression could alleviate the effects of RCC2 knockdown in DDP-resistant ovarian cancer cells. Taken together, RCC2 may function as an oncogene, regulating the RalA signaling pathway, and intervention of RCC2 expression might be a promising therapeutic strategy for DDP-resistant ovarian cancer.-Gong, S., Chen, Y., Meng, F., Zhang, Y., Wu, H., Li, C., Zhang, G. RCC2, a regulator of the RalA signaling pathway, is identified as a novel therapeutic target in cisplatin-resistant ovarian cancer.

MicroRNA-20a contributes to cisplatin-resistance and migration of OVCAR3 ovarian cancer cell line

MicroRNAs (miRs) have been reported to be associated with the development of numerous types of cancer. However, the function of miRs in human ovarian carcinoma chemoresistance remains largely undefined. In the present study, cell chemotherapy combined with a Cell Counting Kit-8 assay demonstrated that miR-20a performed important roles in ovarian cancer cells chemoresistance. Flow cytometry, cellular proliferation assays and Transwell assays results revealed that the proliferation and migration rates of OVCAR3/DDP cells were increased in comparison with parental cells. Western blot analysis results suggested that epithelial-mesenchymal transition (EMT) activated by miR-20a contributed to OVCAR3/DDP cell migration. The present study highlighted the importance of miR-20a in regulating the chemoresistant properties of OVCAR3 cells and promoting cisplatin-resistant cell migration by activating EMT. The results of present study may therefore provide novel insights into reversing the chemoresistance of ovarian cancer and improving its treatment.

MiR-130a and MiR-374a Function as Novel Regulators of Cisplatin Resistance in Human Ovarian Cancer A2780 Cells

Chemoresistance remains a major obstacle to effective treatment in patients with ovarian cancer, and recently increasing evidences suggest that miRNAs are involved in drug-resistance. In this study, we investigated the role of miRNAs in regulating cisplatin resistance in ovarian cancer cell line and analyzed their possible mechanisms. We profiled miRNAs differentially expressed in cisplatin-resistant human ovarian cancer cell line A2780/DDP compared with parental A2780 cells using microarray. Four abnormally expressed miRNAs were selected (miR-146a,-130a, -374a and miR-182) for further studies. Their expression were verified by qRT-PCR. MiRNA mimics or inhibitor were transfected into A2780 and A2780/DDP cells and then drug sensitivity was analyzed by MTS array. RT-PCR and Western blot were carried out to examine the alteration of MDR1, PTEN gene expression. A total of 32 miRNAs were found to be differentially expressed in A2780/DDP cells. Among them, miR-146a was down-regulated and miR-130a,-374a,-182 were upregulated in A2780/DDP cells, which was verified by RT-PCR. MiR-130a and miR-374a mimics decreased the sensitivity of A2780 cells to cisplatin, reversely, their inhibitors could resensitize A2780/DDP cells. Furthermore, overexpression of miR-130a could increase the MDR1 mRNA and P-gp levels in A2780 and A2780/DDP cells, whereas knockdown of miR-130a could inhibit MDR1 gene expression and upregulate the PTEN protein expression .In a conclusion, the deregulation of miR-374a and miR-130a may be involved in the development and regulation of cisplatin resistance in ovarian cancer cells. This role of miR-130a may be achieved by regulating the MDR1 and PTEN gene expression.

CA-125 level as a prognostic indicator in type I and type II epithelial ovarian cancer

OBJECTIVE

Most patients with epithelial ovarian cancer achieve a complete clinical remission (CCR) with normal CA-125 but will still relapse and die from their disease. The present study was designed to determine whether CA-125 levels before, during, and after primary treatment provide prognostic information for both type I and type II ovarian cancer.

METHODS

In this retrospective study, we identified 410 patients with epithelial ovarian cancer who had achieved a CCR between 1984 and 2011. A Cox proportional hazards model and log-rank test were used to assess associations between the nadir CA-125, histotype, and prognosis.

RESULTS

The baseline serum CA-125 concentration was higher in patients with type II ovarian cancer than in those with type I ovarian cancer (P < 0.001). The nadir CA-125 was an independent predictor of progression-free survival (PFS; P < 0.001) and overall survival (OS; P = 0.035) duration. The PFS and OS durations were 21.7 and 79.4 months in patients with CA-125 of 10 U/mL or less and 13.6 and 64.6 months in those with CA-125 of 11 to 35 U/mL, respectively (P = 0.01 and P = 0.002, respectively). Histotype was an independent predictor of PFS (P = 0.041): the PFS and OS durations of the patients with type I ovarian cancer were longer than those of the patients with type II ovarian cancer (P < 0.001 and P < 0.001, respectively).

CONCLUSIONS

The nadir CA-125 and histotype are predictive of PFS and OS durations in patients with ovarian cancers who experienced a CCR. Progression-free survival and OS durations were shorter in the patients with CA-125 levels of 11 to 35 U/mL and type II disease than in those with CA-125 levels of 10 U/mL or less and type I ovarian cancer.

Altered microRNA expression in cisplatin-resistant ovarian cancer cells and upregulation of miR-130a associated with MDR1/P-glycoprotein-mediated drug resistance

microRNAs (miRNAs) are short non-coding RNA molecules which are involved in the regulation of various biological processes. Drug resistance has become a major obstacle to successful chemotherapy of ovarian cancer. The aim of this study was to investigate microRNA expression profiles in cisplatin-resistant ovarian cancer cells and the role of miR-130a in regulating drug resistance. Analysis of differentially expressed miRNAs between SKOV3 and SKOV3/CIS cells was assessed by miRNA microarrays. Target prediction of miRNAs was determined with the help of PicTar or TargetScan. Among these miRNAs, the expression of miR‑130a was verified using qRT-PCR. The expression of MDR1 mRNA and P-glycoprotein (P-gp) after cellular transfection was examined using qRT-PCR and western blotting, respectively. Cisplatin sensitivity was detected by the MTT assay. We indentified 35 downregulated and 54 upregulated miRNAs in SKOV3/CIS compared to those in SKOV3. We found that miR-130a was upregulated in SKOV3/CIS compared to the parental SKOV3 cells, and PTEN was predicted to be the potential target of miR-130a. Moreover, downregulation of miR-130a could inhibit MDR1 mRNA and P-gp expression and overcome the cisplatin resistance in SKOV3/CIS cells, which indicated that miR-130a may be associated with MDR1/P-gp-mediated drug resistance and plays the role of an intermediate in drug-resistance pathways of PI3K/Akt/PTEN/mTOR and ABC superfamily drug transporters in SKOV3/CIS cells. This study provides important information for the development of targeted gene therapy for reversing cisplatin resistance in ovarian cancer.

Optimizing molecular-targeted therapies in ovarian cancer: the renewed surge of interest in ovarian cancer biomarkers and cell signaling pathways

The hallmarks of ovarian cancer encompass the development of resistance, disease recurrence and poor prognosis. Ovarian cancer cells express gene signatures which pose significant challenges for cancer drug development, therapeutics, prevention and management. Despite enhancements in contemporary tumor debulking surgery, tentative combination regimens and abdominal radiation which can achieve beneficial response rates, the majority of ovarian cancer patients not only experience adverse effects, but also eventually relapse. Therefore, additional therapeutic possibilities need to be explored to minimize adverse events and prolong progression-free and overall response rates in ovarian cancer patients. Currently, a revival in cancer drug discovery is devoted to identifying diagnostic and prognostic ovarian cancer biomarkers. However, the sensitivity and reliability of such biomarkers may be complicated by mutations in the BRCA1 or BRCA2 genes, diverse genetic risk factors, unidentified initiation and progression elements, molecular tumor heterogeneity and disease staging. There is thus a dire need to expand existing ovarian cancer therapies with broad-spectrum and individualized molecular targeted approaches. The aim of this review is to profile recent developments in our understanding of the interrelationships among selected ovarian tumor biomarkers, heterogeneous expression signatures and related molecular signal transduction pathways, and their translation into more efficacious targeted treatment rationales.

Identifying clinical improvement in consolidation single-arm phase 2 trials in patients with ovarian cancer in second or greater clinical remission

OBJECTIVE

Estimates of progression-free survival (PFS) from single-arm phase 2 consolidation/maintenance trials for recurrent ovarian cancer are usually interpreted in the context of historical controls. We illustrate how the duration of second-line therapy (SLT), the time on the investigational therapy (IT), and patient enrollment plan can affect efficacy measures from maintenance trials and might result in underpowered studies.

METHODS

Efficacy data from 3 published single-arm consolidation therapies in second remission in ovarian cancer were used for illustration. The studies were designed to show an increase in estimated median PFS from 9 to 13.5 months. We partitioned PFS as the sum of the duration of SLT, treatment-free interval, and duration of IT. We calculated the statistical power when IT is given concurrently with SLT or after SLT by varying the start of IT. We compared the sample sizes required when PFS includes the time on SLT versus PFS that starts after SLT at initiation of IT.

RESULTS

Required sample sizes varied with duration of SLT. If IT starts with initiation of SLT, only 34 patients are needed to provide 80% power to detect a 33% hazard reduction. In contrast, 104 patients are required for a single-arm study for 80% power, if IT begins 7.5 months after SLT initiation.

CONCLUSIONS

Designs of nonrandomized consolidation trials that aim to prolong PFS must consider the effect of the duration of SLT on the end point definition and on required sample size. If IT is given concurrently with SLT, and after SLT, then SLT duration must be restricted per protocol eligibility, so that a comparison with historical data from other single-arm phase 2 studies is unbiased. If IT is given after SLT, the duration of SLT should be taken into account in the design stage because it will affect statistical power and sample size.

Continued chemotherapy after complete response to primary therapy among women with advanced ovarian cancer: a meta-analysis

BACKGROUND

Ovarian cancer (OC) is associated with a >75% risk of recurrence after completion of primary therapy. Several clinical trials have explored the role of continued therapy after complete response to primary adjuvant therapy to reduce the risk of recurrence; however, these trials have largely been underpowered, leading to inconclusive results.

METHODS

A systematic search strategy was initiated to identify all clinical trials involving consolidation or maintenance therapy regimens for OC in first complete remission. A meta-analysis was conducted to evaluate toxicity and progression-free (PFS) and overall survival (OS).

RESULTS

There were 37 publications meeting all eligibility criteria, representing 20 consolidation and 9 maintenance therapy trials. Consolidation and maintenance therapies were associated with improved PFS (hazard ratio [HR], 0.79 [P = .003] and HR, 0.82 [P = .02], respectively) and OS (HR, 0.68 [P = .0008] and HR, 0.68 [P = .007], respectively). This relationship remained statistically significant when the analysis was limited to randomized trials and across other sensitivity analyses.

CONCLUSIONS

Although individual studies have not yet convincingly shown a survival advantage with maintenance chemotherapy in OC, this meta-analysis demonstrates that continued chemotherapy after completion of primary therapy for OC improves PFS and OS. Benefits are greatest in patients with advanced stage OC who reach complete clinical or pathologic response after primary therapy.

Cancer testis antigen vaccination affords long-term protection in a murine model of ovarian cancer

Sperm protein (Sp17) is an attractive target for ovarian cancer (OC) vaccines because of its over-expression in primary as well as in metastatic lesions, at all stages of the disease. Our studies suggest that a Sp17-based vaccine can induce an enduring defense against OC development in C57BL/6 mice with ID8 cells, following prophylactic and therapeutic treatments. This is the first time that a mouse counterpart of a cancer testis antigen (Sp17) was shown to be expressed in an OC mouse model, and that vaccination against this antigen significantly controlled tumor growth. Our study shows that the CpG-adjuvated Sp17 vaccine overcomes the issue of immunologic tolerance, the major barrier to the development of effective immunotherapy for OC. Furthermore, this study provides a better understanding of OC biology by showing that Th-17 cells activation and contemporary immunosuppressive T-reg cells inhibition is required for vaccine efficacy. Taken together, these results indicate that prophylactic and therapeutic vaccinations can induce long-standing protection against OC and delay tumor growth, suggesting that this strategy may provide additional treatments of human OC and the prevention of disease onset in women with a family history of OC.

Inhibition of Sp1-dependent transcription and antitumor activity of the new aureolic acid analogues mithramycin SDK and SK in human ovarian cancer xenografts

OBJECTIVE

Increased activity of Sp family of transcription factors is a frequent and critical event in cancer development and progression. Genes governing tumor growth, invasion and angiogenesis are regulated by Sp factors, like Sp1, Sp3 or Sp4, and are frequently over-expressed in tumors. Targeting Sp factors has been explored as a therapeutic approach. Mithramycin (MTM) is a natural antibiotic that binds DNA and inhibit Sp1-dependent transcription. New analogues, named MTM-SDK and MTM-SK, were recently obtained by genetic engineering of the MTM biosynthetic pathway and have demonstrated improved transcriptional and antiproliferative activity in ovarian cancer cell lines in vitro. In the present study we evaluated the activity of the new compounds in human ovarian cancer xenografts.

METHODS

Expression of Sp1 and target proteins in ovarian cancer specimens and tumor xenografts was assessed by immunohistochemistry. Drug-induced silencing of Sp1-regulated genes in cells and tumor xenograft samples was assessed by quantitative RT-PCR. Toxicity and antitumor activity of the compounds were investigated in healthy and tumor-bearing immunocompromised mice, respectively.

RESULTS

Expression of Sp1 was frequently increased in human epithelial ovarian cancers. MTM-SDK and MTM-SK acted as potent inhibitors of Sp1-dependent transcription both in vitro and in tumor xenografts. Both compounds were well tolerated even after prolonged administration and delayed growth of ovarian tumor xenografts. MTM-SDK was particularly effective against orthotopic tumors leading to a significant increase of survival and delay of tumor progression.

CONCLUSIONS

MTM-SDK and MTM-SK show relevant activity in vivo and represent interesting candidates for treatment of ovarian cancers.