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Overexpression of Glutathione-S-Transferase A1 in Benign Adrenocortical Adenomas from Patients with Cushing’s Syndrome

Departments of Endocrinology and Metabolism and Teratology and Genetics (S.H.), Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan; and Department of Surgery II, Nagoya University School of Medicine (T.I., H.F.), 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan

Address all correspondence and requests for reprints to: Dr. Hisao Seo, Department of Endocrinology and Metabolism, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan. E-mail: hseo{at}riem.nagoya-u.ac.jp

Benign adrenocortical adenoma is a major primary cause of Cushing’s syndrome. Although numerous studies have been performed, the molecular mechanism of adrenocortical adenoma is yet to be elucidated. In this study we endeavored to identify genes differentially regulated in adrenocortical adenoma by suppression PCR-based complementary DNA (cDNA) subtractive hybridization. The cDNA population in atrophied nontumorous adrenal gland adjacent to the adenoma was subtracted from that in the adenoma. Then adenoma-specific cDNAs were amplified by PCR. We cloned several cDNAs that are selectively up-regulated in the adenoma, one of which was identified to encode glutathione-S-transferase A1 (GSTA1). Northern blot analysis revealed that GSTA1 messenger ribonucleic acid was abundantly expressed in the adenoma compared with that in the adjacent atrophied nontumorous gland. Western blot analysis and immunohistochemistry showed high expression of GSTA1 also at the protein level. In concordance with this finding, GST activity was significantly higher in the adenoma than in the adjacent atrophied nontumorous gland. To clarify the role of GSTA1 in adrenocortical cells, GST activity in the H295R human adrenocortical cell line was inhibited by ethacrynic acid. Inhibition of GSTs interfered with proliferation of the cells. We, therefore, hypothesize that overexpression of GSTA1 in adrenocortical adenomas might be involved in the growth of tumor cells. We also speculate that this overexpression might be an adaptive response to excess cortisol production.

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				D. Sarkar, T. Imai, F. Kambe, A. Shibata, S. Ohmori, A. Siddiq, S. Hayasaka, H. Funahashi, and H. Seo The Human Homolog of Diminuto/Dwarf1 Gene (hDiminuto): A Novel ACTH-Responsive Gene Overexpressed in Benign Cortisol-Producing Adrenocortical Adenomas J. Clin. Endocrinol. Metab., November 1, 2001; 86(11): 5130 - 5137. [Abstract] [Full Text] [PDF]