Abstract
Results Proteomic analysis of frozen melanoma clinical specimens and cell lines demonstrated that phosphorylation (activation) of AKT (P-AKT) correlated inversely with PTEN protein expression. Confirmatory analysis of PTEN expression by an immunohistochemical (IHC) assay on archival tumor samples identified a linear correlation between PTEN measurement by IHC and RPPA. Significantly increased expression of P-AKT was observed in melanomas with complete loss of PTEN protein expression compared to tumors with any other pattern of PTEN expression. Integrated analysis of BRAF/NRAS mutation status, PTEN expression, and clinical outcomes was performed using lymphadenectomy specimens from patients who underwent surgery for stage IIIB/C melanoma. Complete loss of PTEN expression correlated with shorter overall survival and time to brain metastasis on univariate and multivariate analyses. Testing of human melanoma cell lines demonstrated that cells with baseline or compensatory activation of the PI3K-AKT pathway were generally resistant to apoptosis induction following BRAF or MEK inhibition. Extended molecular profiling found that a subset of melanoma cell lines with de novo and acquired resistance to MEK inhibitors are characterized by increased expression of PGC1alpha and a metabolic phenotype of high oxidative phosphorylation (OxPhos). The resistant high OxPhos cell lines all demonstrated synergistic growth inhibition and apoptosis induction with combined targeting of MEK and mTORC1/2. mTORC1/2 inhibition decreased PGC1alpha expression in vitro and in vivo, and caused cytosolic localization of MITF. Treatment with a MEK inhibitor and an mTORC1/2 inhibitor demonstrated marked synergy in a BRAF-mutant, MEK inhibitor resistant human melanoma cell line in vivo.
Highlights
The PI3K-AKT pathway has been shown to complement activation of the MAPK pathway in melanocyte transformation in preclinical models
Cell lines demonstrated that cells with baseline or compensatory activation of the PI3K-AKT pathway were generally resistant to apoptosis induction following BRAF or MEK inhibition
Extended molecular profiling found that a subset of melanoma cell lines with de novo and acquired resistance to MEK inhibitors are characterized by increased expression of PGC1alpha and a metabolic phenotype of high oxidative phosphorylation (OxPhos)
Summary
The PI3K-AKT pathway has been shown to complement activation of the MAPK pathway in melanocyte transformation in preclinical models. We have utilized clinical specimens and cell lines to examine the regulation, functional role, and clinical significance of the PI3K-AKT pathway in melanoma
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
