Abstract 3923: Oncogenic kinase-induced PKM2 Y105 phosphorylation promotes tumorigenesis and cancer stem cell-like property

The role of pyruvate kinase M2 isoform (PKM2) in tumor progression is controversial. Previously, it was reported that PKM2 has an oncogenic function in promoting tumor growth in xenograft models; however, PKM2 was indicated non-oncogenic or even anti-oncogenic because depletion of PKM2 accelerates mammary tumor growth in the Brca1 knockout mouse model of breast cancer. Since tumors frequently harbor various abnormally activated oncogenic kinases, we hypothesized that phosphorylation of PKM2 by oncogenic kinases in tumor cells enables PKM2 to promote tumor growth, while unphosphorylated PKM2 in non-transformed cells cannot promote tumor growth. Here, we report that PKM2 proteins were largely unphosphorylated and formed tetramers in normal mammary epithelial cells (MCF10A, MCF12A). On the other hand, PKM2 proteins were phosphorylated at Y105 and formed dimers in breast cancer cells (MDA-MB-231, MDA-MB-435). Knocking down PKM2 didn’t affect normal mammary epithelial cell (MCF10A) growth but significantly decreased breast cancer cell MDA-MB-231 proliferation. In addition, introducing the PKM2-Y105D phosphomimetic mutant into MCF10A cells induced epithelial to mesenchymal transition, increased CD44 Hi /CD24 Neg stem cell-like cell population, and induced colony formation in soft agar, promoted cell migration and invasion. Interestingly, PKM2-Y105D increased YAP1 protein nuclear localization in MCF10A cells, whereas inhibiting YAP1 by siRNA or a chemical inhibitor (Verteporfin) decreased PKM2-Y105D-induced cancer stem cell-like population and colony formation ability. The data indicate that YAP1 is a novel downstream target of pY105-PKM2 in promoting the stem-like property and triggering mammary tumor initiation. Next, we performed receptor tyrosine kinase array and identified several oncogenic tyrosine kinases (AXL, EPHA2, FAK, Src, JAK3 and so on) that effectively phosphorylates PKM2 at Y105. Currently, we are testing the efficacy of targeting these oncogenic tyrosine kinases in reversing the phosphorylation of PKM2 and blocking its tumor-promoting function. Together, our data indicate that oncogenic kinases-induced phospho-Y105-PKM2, but not the unphosphorylated PKM2, promotes mammary tumor initiation by increasing cancer stem cell populations. Citation Format: Zhifen Zhou, Min Li, Lin Zhang, Dihua Yu. Oncogenic kinase-induced PKM2 Y105 phosphorylation promotes tumorigenesis and cancer stem cell-like property [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3923. doi:10.1158/1538-7445.AM2017-3923