Anti-Mullerian hormone concentration regulates activin receptor-like kinase-2/3 expression levels with opposing effects on ovarian cancer cell survival

Anti-Mullerian hormone (AMH) type II receptor (AMHRII) and the AMH/AMHRII signaling pathway are potential therapeutic targets in ovarian carcinoma. Conversely, the role of the three AMH type I receptors (AMHRIs), namely activin receptor-like kinase (ALK)2, ALK3 and ALK6, in ovarian cancer remains to be clarified. To determine the respective roles of these three AMHRIs, the present study used four ovarian cancer cell lines (COV434-AMHRII, SKOV3-AMHRII, OVCAR8, KGN) and primary cells isolated from tumor ascites from patients with ovarian cancer. The results demonstrated that ALK2 and ALK3 may be the two main AMHRIs involved in AMH signaling at physiological endogenous and supraphysiological exogenous AMH concentrations, respectively. Supraphysiological AMH concentrations (25 nM recombinant AMH) were associated with apoptosis in all four cell lines and decreased clonogenic survival in COV434-AMHRII and SKOV3-AMHRII cells. These biological effects were induced via ALK3 recruitment by AMHRII, as ALK3-AMHRII dimerization was favored at increasing AMH concentrations. By contrast, ALK2 was associated with AMHRII at physiological endogenous concentrations of AMH (10 pM). Based on these results, tetravalent IgG1-like bispecific antibodies (BsAbs) against AMHRII and ALK2, and against AMHRII and ALK3 were designed and evaluated. In vivo, COV434-AMHRII tumor cell xenograft growth was significantly reduced in all BsAb-treated groups compared with that in the vehicle group (P=0.018 for BsAb 12G4-3D7; P=0.001 for all other BsAbs). However, the growth of COV434-AMHRII tumor cell xenografts was slower in mice treated with the anti-AMRII-ALK2 BsAb 12G4-2F9 compared with that in animals that received a control BsAb that targeted AMHRII and CD5 (P=0.048). These results provide new insights into type I receptor specificity in AMH signaling pathways and may lead to an innovative therapeutic approach to modulate AMH signaling using anti-AMHRII/anti-AMHRI BsAbs.