HIF and COX-2 expression in triple negative breast cancer cells with hypoxia and 5-fluorouracil

Abstract

Our purpose was to understand the effects of normoxia or hypoxia on 5-fluorouracil  (5-FU) treatment in triple negative breast cancer (TNBC) cells, and characterize the molecular changes in hypoxia inducible factors (HIFs) and cyclooxygenase-2 (COX-2) following treatment.  Cell viability and protein levels of HIFs and COX-2 were determined after wild type and HIF silenced MDA-MB-231 cells, and wild type SUM-149 cells, were treated with 5-FU under normoxia or hypoxia.  5-FU reduced cell viability to the same levels irrespective of normoxia or hypoxia.  HIF silenced MDA-MB-231 cells showed comparable changes in cell viability, supporting observations that hypoxia and the HIF pathways did not significantly influence cell viability reduction by 5-FU.  Our data suggest that HIF-2aaccumulation may predispose cancer cells to cell death under hypoxia.  SUM-149 cells that have higher COX-2 and HIF-2afollowing 24 h of hypoxia, were more sensitive to 96 h of hypoxia compared to MDA-MB-231 cells, and were more sensitive to 5-FU than MDA-MB-231 cells.  COX-2 levels changed with hypoxia and with 5-FU treatment but patterns were different between the two cell lines.  At 96 h, COX-2 increased in both untreated and 5-FU treated cells under hypoxia in MDA-MB-231 cells.  In SUM-149 cells, only treatment with 5-FU increased COX-2 at 96 h of hypoxia.  Cells that survive hypoxia and 5-FU treatment may exhibit a more aggressive phenotype.  Our results support understanding interactions between HIF and COX-2 with chemotherapeutic agents under normoxia and hypoxia, and investigating the use of COX-2 inhibitors in these settings.