Arsenite-induced pseudo-hypoxia results in loss of anchorage-dependent growth in BEAS-2B pulmonary epithelial cells

Abstract

Epidemiology studies have established a strong link between lung cancer and arsenic exposure. Currently, the role of disturbed cellular energy metabolism in carcinogenesis is a focus of scientific interest. Hypoxia inducible factor-1 alpha (HIF-1A) is a key regulator of energy metabolism, and it has been found to accumulate during arsenite exposure under oxygen-replete conditions. We modeled arsenic-exposed human pulmonary epithelial cells in vitro with BEAS-2B, a non-malignant lung epithelial cell line. Constant exposure to 1 μM arsenite (As) resulted in the early loss of anchorage-dependent growth, measured by soft agar colony formation, beginning at 6 weeks of exposure. This arsenite exposure resulted in HIF-1A accumulation and increased glycolysis, similar to the physiologic response to hypoxia, but in this case under oxygen-replete conditions. This "pseudo-hypoxia" response was necessary for the maximal acquisition of anchorage-independent growth in arsenite-exposed BEAS-2B. The HIF-1A accumulation and induction in glycolysis was sustained throughout a 52 week course of arsenite exposure in BEAS-2B. There was a time-dependent increase in anchorage-independent growth during the exposure to arsenite. When HIF-1A expression was stably suppressed, arsenite-induced glycolysis was abrogated, and the anchorage-independent growth was reduced. These findings establish that arsenite exerts a hypoxia-mimetic effect, which plays an important role in the subsequent gain of malignancy-associated phenotypes.