Characterization of AMH as part of a novel TGF-beta signaling loop

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Project Summary/Abstract. Lung cancer kills approximately 160,000 people in the US annually, making it the deadliest type of cancer, with a 5-year survival rate of only 15.9% of diagnosed cases. As a chaperone protein, heat shock protein 90 (HSP90) is essential to support activity of many proteins involved in oncogenesis, and its overexpression correlates with worse outcomes. Although early HSP90 inhibitors were not clinically successful due to toxic side effects, second-generation compounds, such as ganetespib, are showing considerable promise in late stage clinical trials, including some for lung cancer. Following extensive preliminary short interfering (si)RNA screening, I found that depletion of anti-Müllerian hormone (AMH) and the AMH type II receptor (AMHRII) significantly sensitized three KRAS-mutated lung cancer cell lines to ganetespib. Importantly, AMH is a member of the transforming growth factor (TGF)-β superfamily and relates to TGF-β signaling by sharing parts of an effector cascade. TGF-β signaling is frequently involved in lung cancer proliferation, survival and metastasis, the last being the deadliest aspect of this malignancy. TGF-β has been studied extensively, but aspects of its function in aggressive cancer remain opaque. Our preliminary data suggests a novel autocrine-signaling loop involving AMH and AMHRII, representing the first time these proteins have been identified as functioning in a non-gonadal tissue cancer context. Intriguingly, Taipale et al. recently discovered that AMHRII stability is most dependent on HSP90 out of 314 tested kinases, while online databases and my own investigations have established significant expression of AMH and AMHRII in a subset of lung cancer cell lines as well as in many primary lung cancers. Thus, we propose that AMH and AMHRII play a critical role in a subpopulation of lung cancers, and may be exploitable targets to potentiate the efficacy of current and novel therapies or at minimum be utilized as biomarkers. Our broad, long-term objectives are to further elucidate the role TGF-β plays in cancer proliferation and metastasis and how this information can be used to improve the status quo of patients afflicted with lung cancer. Our three aims will better delineate AMH as a pro-survival ligand linked to TGF-β signaling and explore the translational possibilities of our findings. For our first aim, we will use siRNA and overexpression experiments to probe interactions of AMH and the TGF-β effector cascades and explore links of AMH to epithelial-mesenchymal transition. The second aim will use in vitro testing of combinations of ganetespib with AMHIIR-targeting antibodies or an AMH-targeting fusion protein, in the context of altered AMH function, and xenograft mouse models will be used to study the effects of short hairpin RNA (shRNA) knockdown of AMH in combination with ganetespib treatment in vivo. Lastly, we will stain tissue microarrays of human lung cancer for AMH, AMHRII, HSP90 and several other proteins as part of a preclinical assessment.