Abstract 3784: Induction of BRCAness phenotype by curcumin and hydroxyurea in WT BRCA ovarian cancer cells
Authors: Mao Yuehua , Dinnen Richard D , Fine Robert L. 
Published: May 2015

The field of ovarian cancer therapeutics has made a substantial leap forward with the discovery that ovarian cancers with a BRCA mutation, can be exploited with “synthetic lethality.” In patients who have a BRCA germline mutation, this phenomenon is achieved by blocking PARP (poly-ADP-ribosyl-polymerase), which has a role in compensating for the missing or low levels of the BRCA protein. PARP activity is essential for DNA repair in patients with BRCA mutations as their cells attempt to maintain a normal genotype; however, PARP is not enough to compensate for the BRCA mutation, and these patients eventually develop ovarian cancer. Out of the five major mechanisms of DNA repair, PARP compensates for missing BRCA1 and/or BRCA2 proteins required for homologous repair, base excision repair and nuclear excision repair. If PARP is inhibited in BRCA-mutant patients, DNA mutations accumulate and are not repaired because PARP is not available to ribosylate the areas of cut or damaged DNA, which would signal that repair is needed. The BRCA-mutant genotype, in which there is a germline-inactivating mutation in one allele and loss of heterozygosity or somatic mutation in the other allele, only occurs in 5-10% of the cancer population. We wondered, “is there a way to apply the concept of “synthetic lethality” to the 90-95% of the ovarian cancer patients who do not have BRCA mutations?” We tried to answer that query by testing different gene-expression, modulating agents. We found that low-concentration hydroxyurea can sometimes potentiate the cytotoxicity of alkylating agents, suggesting a mechanism that involves DNA repair.

We found synergistic apoptosis in 4 (ovcar-8, TOV21G, PA-1 and UACC1598) ovarian cancer cell lines treated with hydroxyurea and the PARP inhibitor, Olaparib, and in cells treated with curcumin with Olaparib. When the Ovcar-8 cancer cell line was treated with a single agent, the percentage of apoptosis was ≤ 17%, and when treated with synergistic agents together, relative apoptosis increased to ≤ 45%.

In these cell lines, both curcumin and hydroxyurea significantly decreased BRCA1 and BRCA2 mRNA and protein levels. We also found that curcumin triggered BRCA1,2 promoter methylation, which led to cessation of gene expression. Whereas, hydroxyurea, not only caused BRCA1,2 promoter methylation, but also elicited an increase in miRNA hsa-miR-17-5p and hsa-miR-182-5p, causing BRCA1 mRNA degradation.

This finding suggests greater than 5-10% of wild-type, BRCA ovarian cancer patients may benefit from PARP inhibitors and DNA cross-linking agents, such as mitomycin C. if they can be induced into “BRCAness,”

Citation Format: Yuehua Mao, Richard D Dinnen, Robert L. Fine. Induction of BRCAness phenotype by curcumin and hydroxyurea in WT BRCA ovarian cancer cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3784. doi:10.1158/1538-7445.AM2014-3784