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Ross KC , Andrews AJ , Marion CD , Yen TJ , Bhattacharjee V
Identification of the Serine Biosynthesis Pathway as a Critical Component of BRAF Inhibitor Resistance of Melanoma, Pancreatic, and Non-Small Cell Lung Cancer Cells
Mol Cancer Ther. 2017 Aug;16(8) :1596-1609
PMID: 28500236    PMCID: PMC5544579    URL: https://www.ncbi.nlm.nih.gov/pubmed/28500236
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Metastatic melanoma cells commonly acquire resistance to BRAF V600E inhibitors (BRAFi). In this study, we identified serine biosynthesis as a critical mechanism of resistance. Proteomic assays revealed differential protein expression of serine biosynthetic enzymes PHGDH, PSPH, and PSAT1 following vemurafenib (BRAFi) treatment in sensitive versus acquired resistant melanoma cells. Ablation of PHGDH via siRNA sensitized acquired resistant cells to vemurafenib. Inhibiting the folate cycle, directly downstream of serine synthesis, with methotrexate also displayed similar sensitization. Using the DNA-damaging drug gemcitabine, we show that gemcitabine pretreatment sensitized resistant melanoma cells to BRAFis vemurafenib and dabrafenib. We extended our findings to BRAF WT tumor cell lines that are intrinsically resistant to vemurafenib and dabrafenib. Pretreatment of pancreatic cancer and non-small cell lung cancer cell lines with sublethal doses of 50 and 5 nmol/L of gemcitabine, respectively, enhanced killing by both vemurafenib and dabrafenib. The novel aspects of this study are the direct identification of serine biosynthesis as a critical mechanism of BRAF V600E inhibitor resistance and the first successful example of using gemcitabine + BRAFis in combination to kill previously drug-resistant cancer cells, creating the translational potential of pretreatment with gemcitabine prior to BRAFi treatment of tumor cells to reverse resistance within the mutational profile and the WT. Mol Cancer Ther; 16(8); 1596-609. (c)2017 AACR.
Ross, Kayleigh C Andrews, Andrew J Marion, Christopher D Yen, Timothy J Bhattacharjee, Vikram eng P30 CA006927/CA/NCI NIH HHS/ R21 CA191956/CA/NCI NIH HHS/ 2017/05/14 06:00 Mol Cancer Ther. 2017 Aug;16(8):1596-1609. doi: 10.1158/1535-7163.MCT-16-0798. Epub 2017 May 12.