Induction of human endometrial cancer cell senescence through modulation of HIF‐1α activity by EGLN1

Abstract

Previous observations indicate that transfer of human chromosome (chr.) 1 induces senescence of endometrial cancer cells. To identify the gene(s) responsible for the senescence, we first analyzed the structural integrity of the introduced chr. 1 in immortal revertant from chr.1‐transferred HHUA cells. The data demonstrated a correlation between nonrandom deletions within the 1q31‐qter region and reversion to immortality. Next, by using a panel of 12 microsatellite markers, we found high frequencies of loss of heterozygosity in the particular 1q region (1q41‐42), in surgically removed samples. Then, we screened the genetic mutation of the genes involved in this region, with endometrial cancer panel. Among them, EGLN1, that is a member of prolyl hydroxylase and can facilitate HIF‐1 degradation by ubiquitination through the hydroxylation of HIF‐1, was mutated at significantly higher frequencies (12/20, 60%). Introduction of wild‐type EGLN1 into endometrial cancer cell lines (HHUA, Ishikawa and HWCA), that carry EGLN1 gene mutations induced senescence. This was invoked through the negative regulation of HIF‐1 expression. In addition, alternative way of negative regulation of HIF‐1 by Factor inhibiting HIF‐1(FIH), SiRNA against HIF‐1, and HIF‐1 inhibitor, YC‐1, could also induce senescence. Thus, EGLN1 can be considered as a candidate tumor suppressor on chr. 1q, and our observation could open the new aspect in exploring the machinery of senescence induction associated with HIF‐1 signal transduction. These results also suggested the availability of negative regulation of HIF‐1 signals for uterine cancer treatment, especially for uterine sarcomas that have worse prognosis and show a high frequency of EGLN1 gene abnormality.