Degradation of HIF-1α induced by curcumol blocks glutaminolysis and inhibits epithelial-mesenchymal transition and invasion in colorectal cancer cells

Abstract

Colorectal cancer (CRC) has high morbidity and mortality. Epithelial-mesenchymal transition (EMT) is associated with CRC progression and metastasis. Glutaminolysis is essential for malignancy of cancer cells. Here, we examined the effects of curcumol on CRC EMT. We observed that curcumol suppressed invasion and migration in human CRC cells associated with upregulation of epithelial markers E-cadherin and Zonula occludens 1 and downregulation of mesenchymal markers N-cadherin and Vimentin as well as EMT-related transcription factors Snail and Twist. Curcumol increased intracellular levels of glutamine but decreased intracellular levels of glutamate, α-ketoglutarate, ATP, glutathione, and tricarboxylic acid cycle metabolites, suggesting interruption of glutaminolysis. Next, curcumol repressed glutaminase 1 (Gls1) mRNA and protein expression, and overexpression of Gls1 promoted EMT and abolished curcumol effects on CRC cell EMT. Molecular examinations showed that curcumol stimulated protein degradation of hypoxia-inducible factor-1α (HIF-1α) and prevented its nuclear accumulation in CRC cells. HIF-1α agonist deferoxamine (DFO) promoted HIF-1α binding to Gls1 promoter and increased Gls1 expression but abolished curcumol's inhibitory effects on Gls1 expression. DFO also enhanced EMT and invasion and migration in CRC cells and eliminated curcumol effects. Furthermore, mouse CRC models were established with in vivo overexpression of HIF-1α and Gls1. Curcumol effectively inhibited CRC growth, metastasis, and EMT in mice, which was abrogated by overexpression of HIF-1α or Gls1. Altogether, stimulation of HIF-1α degradation was required for curcumol to disrupt EMT and repress invasion and migration in CRC cells through inhibiting Gls1-mediated glutaminolysis. Curcumol could be a promising candidate for intervention of CRC metastasis. • Curcumol inhibits EMT and blocks glutaminolysis in CRC cells. • Inhibition of Gls1 is required for curcumol blockade of glutaminolysis and EMT. • Curcumol induces HIF-1α degradation leading to inhibition of Gls1 and blockade of glutaminolysis and EMT. • Curcumol suppresses CRC growth and metastasis via inhibiting HIF-1α, glutaminolysis and EMT in mice.

Keywords: Colorectal cancer; Curcumol; EMT; Glutaminolysis; HIF-1α; Metastasis.