Differential effects of HIF-alpha isoforms on apoptosis in renal carcinoma cell lines

作者：Doonachar Alana; Gallo Michael D; Doukas Donald; Pasricha Rajiv; Lant**erg Igor; Schoenfeld Alan R^*

来源：Cancer Cell International, 2015, 15(1): 23.

DOI：10.1186/s12935-015-0175-3

• Apoptosis
• Glucose starvation
• HIF-alpha
• Serum starvation
• UV-irradiation
• VHL

Background: Germline mutations in the von Hippel-Lindau (VHL) tumor suppressor gene predispose individuals to clear cell renal carcinomas, hemangioblastomas, and pheochromocytomas. The VHL gene product forms an ubiquitin E3 ligase complex, with regulation of hypoxia-inducible factor alpha (HIF-alpha) as its best known function. Lack of VHL expression has been shown previously to sensitize renal cells to apoptosis caused by certain cellular stresses. In this report, the role of HIF-alpha in apoptosis was investigated using two parent VHL-null renal carcinoma cell lines.
Methods: 786-O and RCC10 renal carcinoma cell lines with manipulated levels of VHL, HIF-1 alpha, or HIF-2 alpha were subjected to cellular stresses and analyzed by western blotting for the abundance of apoptotic markers. Results: Cell lines expressing mutant VHL proteins that were unable to regulate HIF-a had increased levels of apoptosis when irradiated with ultraviolet (UV) light. The influences of the two major isoforms of HIF-alpha, HIF-1 alpha and HIF-2 alpha, on apoptosis, were compared by creating cell lines in which levels of each isoform were modulated via short hairpin RNA interference. In UV-irradiated cells, HIF-2 alpha expression was determined to promote apoptosis, whereas HIF-1 alpha was anti-apoptotic. In cells deprived of either glucose or serum, HIF-1 alpha expression was generally anti-apoptotic, while HIF-2a expression was observed to either promote apoptosis or have less of an influence on apoptosis, depending on the cell line used.
Conclusions: HIF-1 alpha and HIF-2 alpha exerted distinct effects in each of the conditions tested, with expression of HIF-1 alpha largely blocking apoptosis and HIF-2 alpha generally promoting apoptosis. These results reinforce that HIF-1 alpha and HIF-2 alpha have distinct biological roles and that their relative expression levels may influence some therapeutic interventions that are dependent on apoptosis.

• 出版日期2015-2-22