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Oncogenic Kinase-Induced PKM2 Tyrosine 105 Phosphorylation Converts Nononcogenic PKM2 to a Tumor Promoter and Induces Cancer Stem-like Cells.

ABSTRACT: The role of pyruvate kinase M2 isoform (PKM2) in tumor progression has been controversial. Previous studies showed that PKM2 promoted tumor growth in xenograft models; however, depletion of PKM2 in the Brca1-loss-driven mammary tumor mouse model accelerates tumor formation. Because oncogenic kinases are frequently activated in tumors and PKM2 phosphorylation promotes tumor growth, we hypothesized that phosphorylation of PKM2 by activated kinases in tumor cells confers PKM2 oncogenic function, whereas nonphosphorylated PKM2 is nononcogenic. Indeed, PKM2 was phosphorylated at tyrosine 105 (Y105) and formed oncogenic dimers in MDA-MB-231 breast cancer cells, whereas PKM2 was largely unphosphorylated and formed nontumorigenic tetramers in nontransformed MCF10A cells. PKM2 knockdown did not affect MCF10A cell growth but significantly decreased proliferation of MDA-MB-231 breast cancer cells with tyrosine kinase activation. Multiple kinases that are frequently activated in different cancer types were identified to phosphorylate PKM2-Y105 in our tyrosine kinase screening. Introduction of the PKM2-Y105D phosphomimetic mutant into MCF10A cells induced colony formation and the CD44hi/CD24neg cancer stem-like cell population by increasing Yes-associated protein (YAP) nuclear localization. ErbB2, a strong inducer of PKM2-Y105 phosphorylation, boosted nuclear localization of YAP and enhanced the cancer stem-like cell population. Treatment with the ErbB2 kinase inhibitor lapatinib decreased PKM2-Y105 phosphorylation and cancer stem-like cells, impeding PKM2 tumor-promoting function. Taken together, phosphorylation of PKM2-Y105 by activated kinases exerts oncogenic functions in part via activation of YAP downstream signaling to increase cancer stem-like cell properties.Significance: These findings reveal PKM2 promotes tumorigenesis by inducing cancer stem-like cell properties and clarify the paradox of PKM2's dichotomous functions in tumor progression. Cancer Res; 78(9); 2248-61. ©2018 AACR.

SUBMITTER: Zhou Z

PROVIDER: S-EPMC5932213 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Project description:Background:Neuroblastoma (NB) is an early childhood malignancy that arises from the developing sympathetic nervous system. Harmine is a tricyclic ?-carboline alkaloid isolated from the harmal plant that exhibits both cytostatic and cytotoxic effects. Harmine is capable of blocking the activities of dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) family proteins and mitogen-activated protein kinase. These kinases promote proliferation and inhibit apoptosis. Methods:Four human NB cell lines were used to study the effects of harmine treatment: SKNBE and KELLY (MYCN-amplified) as well as SKNAS and SKNFI (MYCN non-amplified). The anti-cancer properties of harmine were examined by RealTime-Glo MT cell viability assays, caspase activity assays, PARP cleavage using Western blot analysis, and flow cytometry-based Annexin V detection. A molecular interaction model of harmine bound to the DYRK2 family kinase was generated by computational docking using X-ray structures. NB tumors from human patients were profiled for DYRK mRNA expression patterns and clinical correlations using the R2 platform. Results:The IC50 values for harmine after 72 h treatment were 169.6, 170.8, and 791.7 ?M for SKNBE, KELLY, and SKNFI, respectively. Exposure of these NB cell lines to 100 ?M of harmine resulted in caspase-3/7 and caspase-9 activation as well as caspase-mediated PARP cleavage and Annexin V-positive stained cells, as early as 24 h after treatment, clearly suggesting apoptosis induction, especially in MYCN-amplified cell lines. Elevated DYRK2 mRNA levels correlated with poor prognosis in a large cohort of NB tumors. Conclusion:Harmine is a known inhibitor of DYRK family kinases. It can induce apoptosis in NB cell lines, which led us to investigate the clinical correlations of DYRK family gene expression in NB tumors. The patient results support our hypothesis that DYRK inhibition by harmine and the subsequent triggering of caspase-mediated apoptosis might present a novel approach to NB therapy.

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Oncogenic Kinase-Induced PKM2 Tyrosine 105 Phosphorylation Converts Nononcogenic PKM2 to a Tumor Promoter and Induces Cancer Stem-like Cells.

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