title: Inhibition of estrogen biosynthesis enhances lymphoma growth in mice.
abstract: Most lymphomas show higher incidence and poorer prognosis in males compared to females. However, the endocrine contribution to this gender difference is not entirely known. Here we show that castration accelerates lymphoma growth in C57BL6 male mice grafted with murine EG7 T cell lymphoma cells. However, the androgen receptor antagonist Bicalutamide did not affect lymphoma growth, suggesting no impact of androgen receptor signaling on lymphoma progression. In contrast, inhibition of androgen-to-estrogen conversion by the aromatase inhibitor (AI) Letrozole induced faster lymphoma growth in mice, suggesting that androgens impact lymphoma growth through its conversion to estrogens. This was supported by the inability of dihydrotestosterone, which is not converted to estrogens by aromatase, to influence lymphoma growth in castrated male mice. Lymphoma growth was also stimulated in immunocompromised mice grafted with human B cell lymphoma (Granta-519) and treated with either reversible or irreversible AIs, showing that the blockage of estrogen synthesis caused enhanced growth of both murine T and human B cell lymphomas and with different AIs. Additionally, AI-treated EG7 lymphomas showed accelerated growth not only in male but also in intact female mice. Altogether, our results demonstrate that aromatase inhibition accelerates lymphoma growth but not androgens per se, highlighting a protective role of estrogens in lymphoma pathogenesis. These results also raise concern that the use of AIs in women with breast cancer might enhance lymphoma progression.
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, NOVUM, Huddinge, Sweden.
authors.forename: Gergely
authors.initials: G
authors.lastname: Talaber
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, NOVUM, Huddinge, Sweden.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Yakimchuk
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, NOVUM, Huddinge, Sweden.
authors.forename: Jiyu
authors.initials: J
authors.lastname: Guan
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, NOVUM, Huddinge, Sweden.
authors.forename: Jose
authors.initials: J
authors.lastname: Inzunza
authors.affiliation: Department of Biosciences and Nutrition, Karolinska Institutet, NOVUM, Huddinge, Sweden.
authors.forename: Sam
authors.initials: S
authors.lastname: Okret
mesh_terms: D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D006801:Humans; D016393:Lymphoma, B-Cell / Q000378:metabolism / Q000473:pathology*; D016399:Lymphoma, T-Cell / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D009919:Orchiectomy; D011960:Receptors, Estrogen / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D004967:Estrogens; D011960:Receptors, Estrogen
keywords: androgens; aromatase inhibitor; gender difference; lymphoma; sex hormones