SUMMARY The pyruvate kinase isoforms PKM1 and PKM2 are alternatively spliced products of the PKM2 gene. PKM2, but not PKM1, alters glucose metabolism in cancer cells and contributes to tumorigenesis by mechanisms that are not explained by its known biochemical activity. We show that PKM2 gene transcription is activated by hypoxia-inducible factor 1 (HIF-1). PKM2 interacts directly with the HIF-1α subunit and promotes transactivation of HIF-1 target genes by enhancing HIF-1 binding and p300 recruitment to hypoxia response elements, whereas PKM1 fails to regulate HIF-1 activity. Interaction of PKM2 with prolyl hydroxylase 3 (PHD3) enhances PKM2 binding to HIF-1α and PKM2 coactivator function. Mass spectrometry and anti-hydroxyproline antibody assays demonstrate PKM2 hydroxylation on proline-403/408. PHD3 knockdown inhibits PKM2 coactivator function, reduces glucose uptake and lactate production, and increases O2 consumption in cancer cells. Thus, PKM2 participates in a positive feedback loop that promotes HIF-1 transactivation and reprograms glucose metabolism in cancer cells.

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Hypoxia-inducible factor 1 (HIF-1) activates transcription of genes encoding proteins that play key roles in breast cancer biology. We hypothesized that interaction of HIF-1 with epigenetic regulators may increase HIF-1 transcriptional activity, and thereby promote breast cancer progression. We report that the histone demethylase jumonji domain containing protein 2C (JMJD2C) selectively interacts with HIF-1α, but not HIF-2α, and that HIF-1α mediates recruitment of JMJD2C to the hypoxia response elements of HIF-1 target genes. JMJD2C decreases trimethylation of histone H3 at lysine 9, and enhances HIF-1 binding to hypoxia response elements, thereby activating transcription of BNIP3, LDHA, PDK1, and SLC2A1, which encode proteins that are required for metabolic reprogramming, as well as LOXL2 and L1CAM, which encode proteins that are required for lung metastasis. JMJD2C expression is significantly associated with expression of GLUT1, LDHA, PDK1, LOX, LOXL2, and L1CAM mRNA in human breast cancer biopsies. JMJD2C knockdown inhibits breast tumor growth and spontaneous metastasis to the lungs of mice following mammary fat pad injection. Taken together, these findings establish an important epigenetic mechanism that stimulates HIF-1-mediated transactivation of genes encoding proteins involved in metabolic reprogramming and lung metastasis in breast cancer.H3K9me3 | SILAC | chromatin immunoprecipitation | gene expression