Abstract B02: Oxidized hemoglobin promotes survival of ROS-stressed and DNA damaged fallopian tube epithelial cells with p53 loss, resulting in a copy number variation phenotype of HGSC.

Abstract

Abstract Purpose: Ovulation is a strong risk factor for high grade serous carcinoma (HGSC) of ovary known to largely originate from the fallopian tube fimbriae. Previously, we have showed ROS in the mature follicular fluid (FF) is mutagenic and cytotoxic to fimbria epithelial cells, and induces DNA double strand breaks (DSB) in the context of p53 loss. We hypothesized that hemoglobin (Hb) in FF accumulated in cul-de-sac (CDS) after ovulatory bleeding may protect the bathed fimbria from cell death and enhance cancer initiation. Results: Peritoneal fluids collected from the CDS after ovulation contained high level of oxidized Hb and ROS, so did ovarian FFs retrieved from IVF patients. When treating E6/E7-immortalized fimbria secretory cells (FE25) with FFs with various ROS levels ranging from 100-1200 μM of H2O2 equivalence, a positive correlation of Hb levels (ranging from 100-1100 μg/ml) in FF and cell viability was observed. This was further confirmed in treating FE25 cells with H2O2 where Hb dose-dependently rescued cell death. As a consequence, FE25 cells treated with either Hb-high FF or with H2O2 plus Hb accumulated high level of DSB and showed an extensive DNA copy number variation compatible with the copy number variation (CNV) phenotype of HGSC. The resulted DNA aneuploidy rates were 50±5% and 65±7% in FE25 treated with 500 μM H2O2 supplemented with 100 μg/ml Hb or 3% Hb-hgih FF, respectively; as compared to 15±2% at baseline and 31±8% with H2O2 only. In the case of primary fimbria epithelial cells the figures were 2±0.3% and 1.3±0.2%, respectively. Finally, the p53 deficiency dependent rescuing effect of Hb on ROS-stressed tubal epithelial cells, and the consequent CNV phenotype were confirmed ex vivo with oviducts of wild type and Trp53-null mice. Conclusion: While ROS in FF induces DNA damage and cytotoxicity of p53-deficient fimbria epithelial cells, oxidized Hb in peritoneal fluid rescues cells from death and results in a CNV phenotype, a major characteristic of HGSC. Citation Format: Hsuan-Shun Huang, Che-Fang Hsu, Tang-Yuan Chu. Oxidized hemoglobin promotes survival of ROS-stressed and DNA damaged fallopian tube epithelial cells with p53 loss, resulting in a copy number variation phenotype of HGSC. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B02.