Abstract 34: AMH and AMHR2 regulate survival signaling, epithelial-mesenchymal transition (EMT) and resistance to HSP90 inhibition in non-small cell lung cancer (NSCLC)
Authors: Beck Tim , Nicolas Emmanuelle , Zhou Yan , Serebriiskii Ilya , Golemis Erica 
Published: August 2015

In spite of encouraging advances in the treatment of lung cancer, the five-year survival rate has remained below 20 percent. Much of the mortality is associated with uncontrolled metastasis. Members of the TGF-ß/BMP superfamily have long been known to regulate progression and metastasis in NSCLC. In this study, we identify unexpected inputs into TGF-ß/BMP superfamily signaling that significantly modulate intrinsic tumor properties and drug response in NSCLC.

Anti-Mullerian Hormone (AMH) and its specific type II receptor, AMHR2, share common type I receptors with BMP, and regulate overlapping signaling outputs. AMH and AMHR2 have thus far predominantly been studied in the context of gonadal development, in regulation of the female reproductive cycle and in gynecological malignancies. However, using a focused RNAi library designed to detect genes associated with resistance to the HSP90 inhibitor ganetespib, siRNAs against AMH and AMHR2 sensitized 4 out of 5 and 3 out of 5 NSCLC cell lines to ganetespib, respectively. We for the first time confirmed autocrine expression of AMH and AMHR2 in this non-gonadal tumor environment.

TGF-ß and BMP signaling is important for the regulation of epithelial-mesenchymal transition (EMT). Strikingly, depletion of AMH/AMHR2 induced EMT-like features, including downregulation of cadherins, assumption of a mesenchymal morphology, and expression of mesenchymal markers, which are generally associated with resistance to chemotherapy. In contrast, inhibition of HSP90 selected for a more epithelial-like population of cells, as evident by increased E-Cadherin or P-Cadherin, and down regulation of mesenchymal markers such as vimentin and α-smooth muscle actin. To confirm that mesenchymal-like cells are indeed more responsive to HSP90 inhibition, we depleted E-cadherin or P-cadherin and again observed sensitization to ganetespib. We further found that AMH and AMHR2 did not confer sensitization to cisplatin.

These data suggested an unusual relationship between ganetespib control of cell growth and differentiation status. We further established that inhibition of HSP90 increased expression of AMH and AMHR2 as well as several of the type 1 receptors (ALK2, ALK3, ALK6) that are necessary for signaling by BMP. Mechanistically, AMH and AMHR2 depletion increased phosphorylation of SMAD proteins, but depressed activity of NF-kB and AKT, both critical regulators of EMT and survival. These results for the first time indicate the presence of an AMH-AMHR2-NFkB-AKT signaling axis of therapeutic relevance in NSCLC. Importantly, our results also suggest that AMH and AMHR2 may serve as biomarkers to predict resistance to HSP90 inhibitors, and that it may be beneficial to prime lung tumors with HSP90 inhibitors, to reverse EMT and decrease survival signaling, prior to treatment with chemotherapy.

Citation Format: Tim Beck, Emmanuelle Nicolas, Yan Zhou, Ilya Serebriiskii, Erica Golemis. AMH and AMHR2 regulate survival signaling, epithelial-mesenchymal transition (EMT) and resistance to HSP90 inhibition in non-small cell lung cancer (NSCLC). [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 34. doi:10.1158/1538-7445.AM2015-34