Granulosa cell tumor with activated mTOR-HIF-1α-VEGF pathway

The DNA-binding activity of hypoxia-inducible factor-1 α (HIF-1α) has been analyzed for various gynecological tumors. Among the tumors that were studied, there was a finding of a high level of DNA-binding HIF-1α activity, although it was limited to one case of adult type granulosa cell tumor (GCT). In this case a 60-year-old female had marked immunohistochemical expression of HIF-1α. The expressions of the mammalian target of rapamycin (mTOR) and phosphorylated-mTOR (p-mTOR) were also marked, and vascular endothelial growth factor (VEGF) was moderately expressed. To compare the expression profiles, 11 consecutive cases with adult type GCT were used. All cases showed marked expressions of HIF-1α and mTOR, but p-mTOR expression was moderately to markedly observed in four of the 12 cases. VEGF was expressed in all cases in varying degrees. Based on the evidence that downregulation of the mTOR pathway due to treatment with rapamycin (everolimus) would suppress tumor cell growth, an experimental study using the GCT cell line was designed to clarify whether HIF-1α and VEGF expressions decline. As a result, the expressions of p-mTOR, HIF-1α and VEGF were suppressed, but those of mTOR were not. It was concluded that mTOR-targeted therapy may represent a promising strategy for some GCT with an activated mTOR-HIF-1α-VEGF pathway.