Glucose metabolism and angiogenesis in granulosa cell tumors of the ovary: activation of Akt, expression of M2PK, TKTL1 and VEGF.

OBJECTIVES

Very little is known about the biology of granulosa cell tumors of the ovary. A hallmark of granulosa cell tumors of the ovary is extensive growth, distant metastases however, are rarely found. We hypothesise that granulosa cell tumors of the ovary on the one hand need to stimulate vascularisation; on the other hand glucose metabolism has to be altered to ensure the supply of nutrients and metabolites. Increased glycolysis, the main source of energy supply, is considered to be important during malignant transformation. Thus, we focussed on a selection of key factors in angiogenesis and tumor glycolysis to study metabolic characteristics of granulosa cell tumors of the ovary.

STUDY DESIGN

We analysed 32 tumor specimens for immunohistochemical expression of vascular endothelial growth factor, phosphorylated Akt, M2 pyruvate kinase isoenzyme, and transketolase-like enzyme 1. As controls, we stained 10 samples of normal ovaries.

RESULTS

We found expression of vascular endothelial growth factor in 94%, transketolase-like enzyme 1 in 81%, and phosphorylated Akt as well as M2 pyruvate kinase isoenzyme in 53% of the specimens. There were no significant differences between the expression levels in primary and those in recurrent tumors. Temporal analysis of marker expression in primary tumors and recurrences in the same patients revealed no increase or decrease of marker expression overtime. In contrast to granulosa cell tumors, normal ovaries showed no expression of the markers analysed in granulosa cells.

CONCLUSION

Our results show that granulosa cell tumors of the ovary express vascular endothelial growth factor as an important stimulator of tumor angiogenesis as well as several molecular markers for glycolysis. The dependence of granulosa cell tumors of the ovary on the glycolytic pathway may provide a biochemical basis for therapeutic strategies involving glycolytic inhibitors.