[Growth of endometrial cancer and hormone]

Proliferation and differentiation of the normal endometrium are orderly regulated by female sex steroid hormones. In this connection, development and growth of endometrial cancer have also thought to be controlled in part by sex steroid hormones. Furthermore, some of the sex steroid hormones, progesterone, for example, are used as therapeutic agents in the management of endometrial cancer. The role of estrogen as a promotion factor of endometrial cancer is understood by unopposed estrogen hypothesis, and relative excess of estrogen unopposed by gestagen is regarded as an important factor for the development of endometrial cancer. High dose administration of gestagen has been used as a therapeutic agent of endometrial cancer over these three decades, and now the oral administration of medroxyprogesterone acetate (MPA) is mainstay, with response rate of approximately 30%. However, recently some cases with serious side effect, mainly thrombosis, have been reported. These cases should be regarded as a grave warning to easy usage of MPA. Therefore, the search for more effective and safe way for clinical application have to be requested; for example, clarification of the precise mechanism of anti-tumor effect of MPA on endometrial cancer or development of new hormonal therapeutic agents. Moreover, basic research in the field of cancer and hormone may create a new era in cancer therapy in the future.