Oncogenic fusions occur in several types of cancer and can be effectively treated with ALK inhibitors; however, fusions and treatment response have not been characterized in malignant melanomas. Recently, a novel isoform of ( ) was reported in 11% of melanomas but the response of melanomas expressing to ALK inhibition has not been well characterized. We analyzed 45 melanoma patient-derived xenograft models for mRNA and protein expression. expression was identified in 11 of 45 (24.4%) melanomas. Ten melanomas express wild-type (wt) and/or and one mucosal melanoma expresses multiple novel fusion variants. Melanoma cells expressing different variants were tested for response to ALK inhibitors. Whereas the melanoma expressing were sensitive to ALK inhibitors and, the melanomas expressing wt or were not sensitive to ALK inhibitors. In addition, a patient with mucosal melanoma expressing was treated with an ALK/ROS1/TRK inhibitor (entrectinib) on a phase I trial but did not respond. Our results demonstrate fusions occur in malignant melanomas and respond to targeted therapy, whereas melanomas expressing do not respond to ALK inhibitors. Targeting fusions is an effective therapeutic option for a subset of melanoma patients, but additional clinical studies are needed to determine the efficacy of targeted therapies in melanomas expressing wt or.
Summary
MLLT11, an MLL fusion partner, is a poor prognostic biomarker for paediatric acute myeloid leukaemia (AML), adult normal cytogenetics AML, and adult myelodysplastic syndrome. MLLT11 is highly regulated during haematopoietic progenitor differentiation and development but its regulatory mechanisms have not been defined. In this study, we demonstrate by transfection experiments that MIR29B directly regulates MLLT11 expression in vitro. MIR29B expression level was also inversely related to MLLT11 expression in a cohort of 56 AML patients (P < 0·05). AML patients with low MIR29B/elevated MLLT11 expression had poor overall survival (P = 0·038). Therefore, MIR29B may be a potential prognostic biomarker for AML patients.
Despite the recent advancement in treating melanoma, options are still limited for patients without BRAF mutations or in relapse from current treatments. BH3 mimetics against members of the BCL-2 family have gained excitement with the recent success in hematological malignancies. However, single drug BH3 mimetic therapy in melanoma has limited effectiveness due to escape by the anti-apoptotic protein MCL-1 and/or survival of melanoma-initiating cells (MICs). We tested the efficacy of the BH3 mimetic combination of A-1210477 (an MCL-1 inhibitor) and ABT-263 (a BCL-2/BCL-XL/BCL-W inhibitor) in killing melanoma, especially MICs. We also sought to better define Dynamin-Related Protein 1 (DRP-1)’s role in melanoma; DRP-1 is known to interact with members of the BCL-2 family and is a possible therapeutic target for melanoma treatment. We used multiple assays (cell viability, apoptosis, bright field, immunoblot, and sphere formation), as well as the CRISPR/Cas9 genome-editing techniques. For clinical relevance, we employed patient samples of different mutation status, including some relapsed from current treatments such as anti-PD-1 immunotherapy. We found the BH3 mimetic combination kill both the MICs and non-MICs (bulk of melanoma) in all cell lines and patient samples irrespective of the mutation status or relapsed state (p < 0.05). Unexpectedly, the major pro-apoptotic proteins, NOXA and BIM, are not necessary for the combination-induced cell death. Furthermore, the combination impedes the activation of DRP-1, and inhibition of DRP-1 further enhances apoptosis (p < 0.05). DRP-1 effects in melanoma differ from those seen in other cancer cells. These results provide new insights into BCL-2 family’s regulation of the apoptotic pathway in melanoma, and suggest that inhibiting the major anti-apoptotic proteins is sufficient to induce cell death even without involvement from major pro-apoptotic proteins. Importantly, our study also indicates that DRP-1 inhibition is a promising adjuvant for BH3 mimetics in melanoma treatment.
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