Journal
CANCERS
Volume 9, Issue 10, Pages -Publisher
MDPI
DOI: 10.3390/cancers9100137
Keywords
hypoxia-induced chemoresistance; HIF-1; STAT3; cisplatin; cancer stemness
Categories
Funding
- Canadian Institutes of Health Research (CIHR)
- Canadian Breast Cancer Foundation (CBCF)
- Women and Children's Health Research Institute (WCHRI)
- Alberta Cancer Foundation (ACF)
- CBCF
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Hypoxia-induced chemoresistance (HICR) is a well-recognized phenomenon, and in many experimental models, hypoxia inducible factor-1 (HIF-1) is believed to be a key player. We aimed to better understand the mechanism underlying HICR in a triple negative breast cancer cell line, MDA-MB-231, with a focus on the role of HIF-1. In this context, the effect of hypoxia on the sensitivity of MDA-MB-231 cells to cisplatin and their stem-like features was evaluated and the role of HIF-1 in both phenomena was assessed. Our results showed that hypoxia significantly increased MDA-MB-231 resistance to cisplatin. Correlating with this, intracellular uptake of cisplatin was significantly reduced under hypoxia. Furthermore, the stem-like features of MDA-MB-231 cells increased as evidenced by the significant increases in the expression of ATP-binding cassette (ABC) drug transporters, the proportion of CD44(+)/CD24(-) cells, clonogenic survival and cisplatin chemoresistance. Under hypoxia, both the protein level and DNA binding of HIF-1 was dramatically increased. Surprisingly, siRNA knockdown of HIF-1 did not result in an appreciable change to HICR. Instead, signal transducer and activator of transcription 3 (STAT3) activation was found to be important. STAT3 activation may confer HICR by upregulating ABC transporters, particularly ABCC2 and ABCC6. This study has demonstrated that, in MDA-MB-231 cells, STAT3 rather than HIF-1 is important in mediating HICR to cisplatin.
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