Inhibiting insulin and mTOR signaling by afatinib and crizotinib combination fosters broad cytotoxic effects in cutaneous malignant melanoma

• Published in: Cell death & disease 2020-10, Vol.11 (10), p.882-882, Article 882
• Main Authors: Das, Ishani, Chen, Huiqin, Maddalo, Gianluca, Tuominen, Rainer, Rebecca, Vito W., Herlyn, Meenhard, Hansson, Johan, Davies, Michael A., Egyházi Brage, Suzanne
• Format: Article
• Language: English
• Subjects: 1-Phosphatidylinositol 3-kinase; 13; 13/1; 13/105; 13/106; 13/2; 13/51; 13/89; 631/67/1059/2326; 631/67/1059/602; 631/67/1813/1634; 631/67/1857; 82; 82/58; 82/80; Afatinib - pharmacology; Antibodies; Antineoplastic Agents - pharmacology; Axl protein; Biochemistry; Biomarkers; Biomedical and Life Sciences; Cancer och onkologi; Cell Biology; Cell Culture; Cell death; Crizotinib - pharmacology; Cytotoxicity; Drug Resistance, Neoplasm - drug effects; EphA2 protein; Farmakologi och toxikologi; Humans; Immunoblotting; Immunofluorescence; Immunology; Insulin; Insulin receptor substrate 1; Klinisk medicin; Life Sciences; MAP kinase; Mass spectroscopy; Medicin och hälsovetenskap; Medicinska och farmaceutiska grundvetenskaper; Melanoma; Melanoma - drug therapy; Melanoma, Cutaneous Malignant; Molecular modelling; Protein arrays; Protein Kinase Inhibitors - pharmacology; Proto-Oncogene Proteins B-raf - metabolism; Signal transduction; Signal Transduction - drug effects; Skin cancer; Skin Neoplasms - drug therapy; Targeted cancer therapy; TOR protein; TOR Serine-Threonine Kinases - drug effects; Xenografts
• ISSN: 2041-4889; 2041-4889
• DOI: 10.1038/s41419-020-03097-2

Current treatment modalities for disseminated cutaneous malignant melanoma (CMM) improve survival, however disease progression commonly ensues. In a previous study we identified afatinib and crizotinib in combination as a novel potential therapy for CMM independent of BRAF/NRAS mutation status. Herein, we elucidate the underlying mechanisms of the combination treatment effect to find biomarkers and novel targets for development of therapy that may provide clinical benefit by proteomic analysis of CMM cell lines and xenografts using mass spectrometry based analysis and reverse phase protein array. Identified candidates were validated using immunoblotting or immunofluorescence. Our analysis revealed that mTOR/Insulin signaling pathways were significantly decreased by the afatinib and crizotinib combination treatment. Both in vitro and in vivo analyses showed that the combination treatment downregulated pRPS6KB1 and pRPS6, downstream of mTOR signaling, and IRS-1 in the insulin signaling pathway, specifically ablating IRS-1 nuclear signal. Silencing of RPS6 and IRS-1 alone had a similar effect on cell death, which was further induced when IRS-1 and RPS6 were concomitantly silenced in the CMM cell lines. Silencing of IRS-1 and RPS6 resulted in reduced sensitivity towards combination treatment. Additionally, we found that IRS-1 and RPS6KB1 expression levels were increased in advanced stages of CMM clinical samples. We could demonstrate that induced resistance towards combination treatment was reversible by a drug holiday. CD171/L1CAM, mTOR and PI3K-p85 were induced in the combination resistant cells whereas AXL and EPHA2, previously identified mediators of resistance to MAPK inhibitor therapy in CMM were downregulated. We also found that CD171/L1CAM and mTOR were increased at progression in tumor biopsies from two matched cases of patients receiving targeted therapy with BRAFi. Overall, these findings provide insights into the molecular mechanisms behind the afatinib and crizotinib combination treatment effect and leverages a platform for discovering novel biomarkers and therapy regimes for CMM treatment.