Friday, May 9, 2025
5/9/2025
Targeting melanoma promoting RNA modification pathway for melanoma therapy. - PROJECT SUMMARY Post-transcriptional mRNA modifications are central to establishing proteomic and functional diversity in mammalian cells. These post-transcriptional mRNA modifications and their functional consequences are controlled by RNA-binding proteins (RBPs). However, our understanding of these alterations and the role of RBPs in melanoma metastasis is limited. Therefore, to identify RBPs that promote melanoma metastasis, we performed a large-scale in vivo short-hairpin RNA screen by targeting 1500 human RBPs. Our in vivo screen identified that YTHDF1, a reader of m6A modified RNA, is necessary for metastatic melanoma. The genetic inhibition of YTHDF1 resulted in increased anoikis induction and enhanced NK cell-mediated metastatic melanoma eradication. Additionally, an unbiased Photoactivable Ribonucleoside-Enhanced Crosslinking (PAR- CLIP) analysis and follow-up studies identified IMPDH1, an enzyme of the de novo guanosine synthesis pathway, and TrkB/BDNF that regulates Neurotrophin signaling pathway as potential downstream mediators of YTHDF1-function in metastatic melanoma. IMPDH1 promoted anoikis resistance, while the TrkB/BDNF pathway was necessary for suppressing NK cell-mediated cytotoxicity against melanoma cells. Our overall objective is to determine the role of cell-intrinsic (anoikis resistance) and cell-extrinsic (NK cell-mediated anti-tumor immunity) pathways in YTHDF1-driven melanoma metastasis and to establish pharmacological targeting of IMPDH1 and TrkB/BDNF pathways as an approach for melanoma therapy. Aim 1 studies will determine the role of YTHDF1- mediated anoikis resistance in driving melanoma metastasis and the role of IMPDH1 and the de novo guanosine synthesis pathway in this process. Aim 2 studies will ascertain the role of YTHDF1-driven suppression of NK cell-mediated anti-tumor immunity in promoting melanoma metastasis. We will also determine the role of TrkB/BDNF pathway and its ability to inhibit the NKG2D activating ligand ULBP6 in suppressing NK-cell function downstream of YTHDF1. Aim 3 studies will evaluate the therapeutic efficacy of TrkB/BDNF and IMPDH1 inhibitors either alone or in conjunction with other US FDA-approved metastatic melanoma therapies. Aims 1-3 studies will utilize complementary cell culture models based on established melanoma cell lines, short-term patient-derived melanoma cultures and patient-derived xenografts (PDXs) of naïve and drug resistance metastatic melanoma. The in vivo models for the proposed studies will include syngeneic, genetically engineered mouse models of metastatic melanoma, spontaneous human melanoma metastasis model, and a highly innovative immunocompetent humanized NSG-Tg(Hu-IL15) mice. These mice develop human NK cells in addition to other immune cells after human hematopoietic stem cells transplant, which will allow us to perform studies in the context of human NK cells. Collectively, these studies will uncover a novel YTHDF1-driven melanoma metastasis pathway that can be targeted for treating naïve and drug-resistant metastatic melanoma.
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