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Metastatic melanoma is an aggressive disease. Despite recent improvements in therapy, drug resistant populations emerge even in drug-sensitive tumors. The ability to adapt to multiple types of stress contributes to tumor progression and therapy resistance. We have found a subset of melanoma cells with high Wnt5A and wild type p53 expression can transition to a slow-cycling state, rendering them resistant to most targeted therapy. Multiple types of stress, including DNA damage, targeted therapy, and aging increase Wnt5A and p53 in these metastatic cells. Inhibiting p53 blocks the slow cycling phenotype and promotes sensitivity to targeted therapy. A single dose of a p53 inhibitor at the commencement of BRAF/MEKi therapy was sufficient to prolong sensitivity to BRAF/MEKi therapy in Yumm1.7 derived tumors grown in aged mice (> 52 weeks). Upon analysis of PDX tumors with WTp53, treated with BRAF/MEKi combination or BRAFi therapy, we observed an increase in p53 positive cells as well as an increase in Wnt5A expression, further linking Wnt5A and p53 with resistance to targeted therapy. These data suggest that melanoma cells require p53 to survive multiple types of stress and that taking the paradoxical approach of inhibiting rather than activating WTp53 may sensitize previously resistant metastatic melanoma cells to therapy by temporarily driving them into a rapidly cycling state. WTp53 is typically thought of as a tumor suppressor due to its ability to regulate cell proliferation, stress response, and cell death. However, in metastatic melanoma cells, p53 promotes the expression of EDIL3, FAP, MMP3, and netrin G1, which are associated with poor prognosis, increased angiogenesis, and metastasis in multiple types of cancer. These data suggest that p53, typically thought of as a tumor suppressor, may be promoting the survival of a subset of highly resistant metastatic cells. Citation Format: Jasmin Giles, Maria Biancaniello, Mitchell Fane, Gretchen Alicea, Andrew Kossenkov, Amanpreet Kaur, Vito Rebecca, Xiaowei Xu, Meenhard Herlyn, Maureen Murphy, Ashani Weeraratna, Marie R. Webster. All stressed out: Phenoytpe plasticity and therapy resistance in melanoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 966. |
