Effect of BAY 87-2243 on gene expression in hypoxic H460 cells

The activation of the transcription factor Hypoxia-inducible factor-1 (HIF-1) plays an essential role in tumor development, tumor progression and resistance to chemo- and radiotherapy. In order to identify compounds targeting the HIF pathway, a small-molecule library was screened using a luciferase-driven HIF-1 reporter cell line under hypoxia. The high throughput screen led to the identification of a class of aminoalkyl-substituted compounds that inhibited hypoxia-induced HIF-1 target gene expression in human lung cancer cell lines at low nanomolar concentrations but did not affect expression levels of genes outside of the HIF-1 pathway. Lead structure BAY 87-2243 was found to inhibit HIF-1 protein accumulation under hypoxic conditions in NSCLC cell line H460 but had no effect on HIF-1 protein accumulation and HIF target gene expression in RCC4 cells lacking VHL activity or in H460 cells after inhibition of HIF prolyl hydroxylase activity. BAY 87-2243 had no effect on HIF--mRNA levels. Antitumor activity of BAY 87-2243 and suppression of HIF-1 target gene expression in vivo was demonstrated in a H460 xenograft model. BAY 87-2243 did not inhibit cell proliferation under standard conditions. However under glucose depletion, a condition favoring mitochondrial ATP generation as energy source, BAY 87-2243 inhibited cell proliferation in the nanomolar range. Further experiments revealed that BAY 87-2243 inhibits mitochondrial production of reactive oxygen species (ROS) by blocking complex I activity but has no effect on complex III activity. Lowering of mitochondrial ROS production to reduce hypoxia-induced HIF-1 activity in tumors might be an interesting therapeutic approach to overcome chemo- and radiotherapy-resistance of hypoxic tumors.

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