American Association for Cancer Research
00085472can143358-sup-140846_2_supp_3187028_nw44wc.ppt (521.5 kB)

Supplementary Figure 2 from Maximizing the Efficacy of MAPK-Targeted Treatment in PTENLOF/BRAFMUT Melanoma through PI3K and IGF1R Inhibition

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posted on 2023-03-30, 23:43 authored by Barbara Herkert, Audrey Kauffmann, Sandra Mollé, Christian Schnell, Thomas Ferrat, Hans Voshol, Janina Juengert, Hélène Erasimus, Grégory Marszalek, Malika Kazic-Legueux, Eric Billy, David Ruddy, Mark Stump, Daniel Guthy, Mitko Ristov, Keith Calkins, Sauveur-Michel Maira, William R. Sellers, Francesco Hofmann, Michael N. Hall, Saskia M. Brachmann

PI3Kβ inhibition induces p85/IRS2 interaction in a time-dependent manner in the PTENLOF/BRAFMUT melanoma cell line RVH-421 that is mediated by negative feedback signaling. A) Co-immunoprecipitation experiments were carried out using cell lysates of RVH-421 treated with the PI3Kbi for the indicated time and blotted for p85, and pTyr (IRS2). B)-D) Input lysates of the immunoprecipitation experiments shown in Figure 4 were immunoblotted with the indicated phospho-specific or total target protein antibodies. PI3Kβi=rac-KIN-193, mTORi=AZD8055, mTORCi=RAD001, PDK1i=GSK-2334470, AKTi=MK2206



The introduction of MAPK pathway inhibitors paved the road for significant advancements in the treatment of BRAF-mutant (BRAFMUT) melanoma. However, even BRAF/MEK inhibitor combination therapy has failed to offer a curative treatment option, most likely because these pathways constitute a codependent signaling network. Concomitant PTEN loss of function (PTENLOF) occurs in approximately 40% of BRAFMUT melanomas. In this study, we sought to identify the nodes of the PTEN/PI3K pathway that would be amenable to combined therapy with MAPK pathway inhibitors for the treatment of PTENLOF/BRAFMUT melanoma. Large-scale compound sensitivity profiling revealed that PTENLOF melanoma cell lines were sensitive to PI3Kβ inhibitors, albeit only partially. An unbiased shRNA screen (7,500 genes and 20 shRNAs/genes) across 11 cell lines in the presence of a PI3Kβ inhibitor identified an adaptive response involving the IGF1R–PI3Kα axis. Combined inhibition of the MAPK pathway, PI3Kβ, and PI3Kα or insulin-like growth factor receptor 1 (IGF1R) synergistically sustained pathway blockade, induced apoptosis, and inhibited tumor growth in PTENLOF/BRAFMUT melanoma models. Notably, combined treatment with the IGF1R inhibitor, but not the PI3Kα inhibitor, failed to elevate glucose or insulin signaling. Taken together, our findings provide a strong rationale for testing combinations of panPI3K, PI3Kβ + IGF1R, and MAPK pathway inhibitors in PTENLOF/BRAFMUT melanoma patients to achieve maximal response. Cancer Res; 76(2); 390–402. ©2015 AACR.