Non-Canonical HIF2 Accumulation in Breast Cancer Cells

Metabolic reprogramming drives cancer aggressiveness. While hypoxia-inducible factor 1 (HIF1) is commonly associated with glycolysis regulation, the under-investigated HIF2 isoform may also modulate the metabolic profile of breast cancer. We investigated the role of non-canonical HIF2 activation in metabolic adaptation to nutrient availability by culturing MDA-MB-231 and MCF-7 cells under normoxia with varying glucose and glutamine concentrations. Using RNA interference, we downregulated HIF2 and analyzed HIF isoforms and metabolic targets (GLUT1, HK2, PKM2, PDK1) at the transcriptional and protein levels. We observed a new, non-canonical accumulation of HIF2 in MDA-MB-231 cells associated with glucose and glutamine restriction, a phenomenon absent in MCF-7 cells. In MDA-MB-231 cells, silencing HIF2A under standard conditions significantly decreased PDK1 mRNA expression. At the protein level, HIF2 downregulation altered metabolic targets in a context-dependent manner under nutrient restriction. Adding a hypoxia-mimetic (CoCl2) did not fully restore the protein expression patterns, suggesting that HIF2 accumulation may contribute to these context-dependent shifts. HIF2 downregulation decreased glycolytic efficiency under low-glucose conditions. Our findings suggest that HIF2 might modulate the metabolic plasticity of MDA-MB-231 cells through distinct changes in gene expression and post-translational mechanisms. This provides support for investigating the HIF2 isoform while studying breast cancer metabolism and considering it as a potential target for treating triple-negative breast cancer.