Abstract NT-102: CHEMICALLY INDUCED HYPOXIA PROMOTES OVARIAN CANCER CHEMORESISTANCE

Abstract

Abstract The accumulation of cells, derived from the imbalance between the aberrant proliferation and resistance to apoptosis of cancer cells, leads to an increased consumption and consequently decreased availability of oxygen (hypoxia). Hypoxia Inducible Factor (HIF-1) is the key regulator of cell adaptive response under different extracellular stimuli. Subunit HIF-1α is kept at low levels under normal oxygen supply, but strongly upregulated under hypoxia. HIF-1α is overexpressed in several malignant and metastatic tumors but its significance in ovarian cancer prognosis is still controversial. CoCl2 is a chemical compound widely used as a positive control for the upregulation of HIF-1α by preventing its proteosomal degradation. Acquired chemoresistance is considered one of the main factors associated with poor prognosis and survival in ovarian cancer patients, and therefore, its understanding is nowadays one of the major challenges pursued to facilitate treatment and increase life expectation of patients. The aim of this study was to determine the possible role of HIF-1α in the development of chemoresistance in ovarian carcinoma. A27801A9 ovarian cancer cell line was treated with 100 μM CoCl2 for 3, 6 12 and 22 hours for chemical induction of hypoxia. Response to cisplatin and paclitaxel chemotherapeutic drugs was tested and compared with untreated cells (normoxia). Western blot was used to test epithelial-to-mesenchymal transition (EMT) and lysyl oxidase (LOx) markers, and enzyme-linked immunosorbent assay (ELISA) to test the secretion of cytokines in cell supernatant. Chemical hypoxia resulted in paclitaxel resistance in a dose-dependent manner, with 7 to 19% increased viability for hypoxic cells in relation to normoxic cells. No effect was observed for cisplatin. HIF-1α expression achieved the maximum level at 12 hours. Mesenchymal markers N-cadherin and vimentin, as well as the transcription factor snail were not remarkably affected, while epithelial marker E-Cadherin expression was reduced at 22 hours and transcription factor slug presented the maximum expression at 12 hours, as well as lysyl oxidase. Tumor necrosis factor (TNF-α) was not affected by the treatments, while inflammatory interlukins IL-6, IL-10 and IL-1β showed differentiated responses, with a slight increase of 3 pg/mL of IL-10 at 12 hours, a decrease of IL-6 in a time dependent manner (from 40 to 3 pg/mL), and a decreased secretion of IL-1β (around 50%) in relation to the control for all the treatment times. These results suggest that epithelial morphology may begin to be lost at 12 hours, through downregulation of E-cadherin mediated by slug as a consequence of HIF-1α upregulation. In addition, the differential expression of cytokines suggests that HIF-1α may be involved in the cellular immune adaptive response. The enhanced mitotic capacity that has been associated to LOx, was possibly increased due to HIF-1α upregulation, reducing the effectivity of paclitaxel and contributing to a consequent acquired chemoresistance. Citation Format: Andrea Nieto-Veloza, Qixin Zhong, Vermont P Dia. CHEMICALLY INDUCED HYPOXIA PROMOTES OVARIAN CANCER CHEMORESISTANCE [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-102.