Various forms of HIF-1α protein characterize the clear cell renal cell carcinoma cell lines

Renal cell carcinoma (RCC) represents around 2-3% of all malignancies diagnosed in adult patients. Most frequent (around 70-80% cases) and the most aggressive subtype is clear cell RCC (ccRCC). Mutations in VHL (von Hippel Lindau) gene, characteristic for this cancer type, lead to altered activity of the trimeric VBC (pVHL-elongin B-C) complex and consequently to HIF-1 alpha stabilization. In this study, we present results of exhaustive investigation of HIF-1 alpha alternative transcript variants abundance in A498, CAKI-1, and 786-O ccRCC cell lines. We proved the existence of truncated HIF-1 alpha protein form (HIF1A increment -6) in A498 and HIF1A gene rearrangements in 786-O cell lines. Subsequently, we found that HIF1A increment 2-6 was more stable than the full-length HIF-1 alpha. Moreover, the shorter HIF-1 alpha was insensitive for hypoxia and was overaccumulated after proteasome inhibitor treatment indicative of potential diversified roles of full-length and truncated HIF-1 alpha forms in the cell. We also showed that A498, CAKI-1, and 786-O exhibit differential expression of various regulatory genes involved in the control of metabolic processes, that is, glucose and lipid metabolism, and encoding subunits of such machineries like SWI/SNF chromatin remodeling complex. Furthermore, these cell lines exhibited differential responses to axitinib, everolimus, and sunitinib-anticancer drugs-in normoxia and hypoxia as well as various alterations in metabolism-related regulatory processes. Finally, we have shown that overexpression of truncated HIF1A increment 2-6 form may affect the protein level of endogenous full-length HIF-1 alpha protein. Thus, our study proves an important role of HIF-1 alpha in the ccRCC development.