Emerging drugs for ovarian cancer

Distinct DNA Methylation Profiles in Ovarian Tumors: Opportunities for Novel Biomarkers

Aberrant methylation of multiple promoter CpG islands could be related to the biology of ovarian tumors and its determination could help to improve treatment strategies. DNA methylation profiling was performed using the Methylation Ligation-dependent Macroarray (MLM), an array-based analysis. Promoter regions of 41 genes were analyzed in 102 ovarian tumors and 17 normal ovarian samples. An average of 29% of hypermethylated promoter genes was observed in normal ovarian tissues. This percentage increased slightly in serous, endometrioid, and mucinous carcinomas (32%, 34%, and 45%, respectively), but decreased in germ cell tumors (20%). Ovarian tumors had methylation profiles that were more heterogeneous than other epithelial cancers. Unsupervised hierarchical clustering identified four groups that are very close to the histological subtypes of ovarian tumors. Aberrant methylation of three genes (BRCA1, MGMT, and MLH1), playing important roles in the different DNA repair mechanisms, were dependent on the tumor subtype and represent powerful biomarkers for precision therapy. Furthermore, a promising relationship between hypermethylation of MGMT, OSMR, ESR1, and FOXL2 and overall survival was observed. Our study of DNA methylation profiling indicates that the different histotypes of ovarian cancer should be treated as separate diseases both clinically and in research for the development of targeted therapies.

Frequent Loss of NISCH Promotes Tumor Proliferation and Invasion in Ovarian Cancer via Inhibiting the FAK Signal Pathway

NISCH encodes the imidazoline receptor Nischarin and is a known tumor suppressor in many human malignancies; however, its roles in ovarian cancer are still largely unknown. Here, we aim to investigate the biologic functions of NISCH in ovarian cancer. We found that NISCH was significantly downregulated, which correlated considerably with advanced tumor stage, poor differentiation, lymph node metastasis, and the serous/mucinous subtypes in a panel of ovarian cancer tissues. Moreover, NISCH gene silencing was mainly the product of promoter hypermethylation, which could be reversed by treatment with 5-aza-dC. In vitro, NISCH overexpression suppressed cell proliferation and colony formation by hindering cell-cycle progression, whereas the opposite was observed in NISCH knockdown counterparts. In vivo, abundant NISCH expression hindered the growth of HO8910 xenografts, whereas NISCH knockdown accelerated the growth of SKOV3 xenografts. In addition, NISCH significantly attenuated cell invasion by inhibiting the phosphorylation of FAK and ERK, which could be neutralized by PF-562271 (a FAK/Pyk2 inhibitor). Accordingly, NISCH knockdown xenografts exhibited increased peritoneal/pelvic metastases that were not present in counterparts treated with PF-562271. Furthermore, NISCH expression in primary ovarian cancer cells predicted a cellular resistance to PF-562271. In conclusion, we showed that NISCH was frequently silenced by promoter hypermethylation in human ovarian cancer. NISCH manipulated cellular proliferation and invasion by arresting cell cycle and inhibiting the FAK signal. Our findings revealed the biologic functions of NISCH in ovarian cancer, and might be useful for treating patients with aberrant expression of NISCH.

Chemotherapy dosing schedule influences drug resistance development in ovarian cancer

Drug resistance leads to chemotherapy failure and is responsible for the death of a great majority of patients with metastatic, late-stage ovarian cancer. The present study addressed whether changes in the chemotherapy dosing schedule affect the development, further worsening, or circumvention of drug resistance in chemosensitive and chemoresistant ovarian cancer. Severe combined immunodeficient mice bearing HeyA8 and HeyA8-MDR xenografts were treated with docetaxel intermittently (1×/wk or 3×/wk) or continuously for 21 days. Tumor mRNA expression of genes implicated in docetaxel resistance was measured by quantitative real-time-PCR. Analyzed genes included those encoding for the drug efflux transporters mdr1 and mrp7 and for molecules that interfere with or overcome the effects of docetaxel, including β-tubulinIII, actinin4, stathmin1, bcl2, rpn2, thoredoxin, and akt2. In both models, continuous docetaxel resulted in greater antitumor efficacy than 1×/wk or 3×/wk dosing and did not induce upregulation of any analyzed genes. Once weekly dosing caused upregulation of various drug resistance-related genes, especially in chemoresistant xenografts. More frequent, 3×/wk dosing diminished this effect, although levels of various genes were higher than for continuous chemotherapy. Drug efflux transporter expression was further examined by Western blotting, confirming that intermittent, but not continuous, docetaxel induced significant upregulation. Overall, our results show that the presence and length of treatment-free intervals contribute to the development of drug resistance. Elimination of these intervals by continuous dosing resulted in superior antitumor efficacy and prevented drug resistance induction in chemosensitive and chemoresistant disease. These results encourage the clinical implementation of continuous chemotherapy to overcome and/or prevent drug resistance in newly diagnosed and recurrent, refractory ovarian cancer.