AMPK-friend or foe for targeted therapy?

High expression of MAGE-A9 contributes to stemness and malignancy of human hepatocellular carcinoma

MAGE-A9, a well-characterized cancer testis antigen (CTA), belongs to a member of melanoma antigen gene (MAGE) family. In human malignancies, aberrant expression of MAGE genes correlated with poor clinical prognosis, increased tumor growth, metastases, and enrichment in stem cell populations of certain cancers. Cancer stem cells (CSCs) have been proposed to contribute to the major malignant phenotypes of liver cancer, including recurrence, metastasis and chemoresistance. However, expression and potential role of MAGE-A9 in liver cancer stem cells (LCSCs) still remain unclear. In the present study, we first analyzed the expression profiling of MAGE family genes in EpCAM+ and EpCAM- human hepatocellular carcinoma (HCC), based on public Gene Expression Omnibus (GEO) database. Among these examined MAGE members, MAGE-A9 is the only one with significantly higher expression in EpCAM+ HCC specimens as compared with EpCAM- HCC. Quantitative PCR analysis further confirmed that MAGE-A9 expression significantly elevated in a subtype of HCC patients that had features of hepatic stem/progenitor cells with high-level expression of EpCAM and α-fetoprotein (AFP). Moreover, MAGE-A9 displayed remarkably enriched expression in EpCAM+ HCC cells that were sorted by fluorescence-activated cell sorting and cultured HCC cell spheroids with characteristics of stem/progenitor cells. Functional experiments further revealed that MAGE-A9 overexpression promoted cell proliferation, colony formation, migration, chemoresistance, and tumorigenicity in the context of EpCAM+ HCC cells, whereas MAGE-A9 knockdown significantly inhibited anchorage-dependent and spheroid colony formation and in vivo tumorigenicity. Collectively, these data demonstrate that MAGE-A9 functions as an important regulator of LCSCs, and MAGE-A9 may serve as a potential therapeutic target against HCC stem/progenitor cells.

A spatiotemporal hypothesis for the regulation, role, and targeting of AMPK in prostate cancer

The 5'-AMP-activated protein kinase (AMPK) is a master regulator of cellular homeostasis. Despite AMPK's known function in physiology, its role in pathological processes such as prostate cancer is enigmatic. However, emerging evidence is now beginning to decode the paradoxical role of AMPK in cancer and, therefore, inform clinicians if - and how - AMPK could be therapeutically targeted. Spatiotemporal regulation of AMPK complexes could be one of the mechanisms that governs this kinase's role in cancer. We hypothesize that different upstream stimuli will activate select subcellular AMPK complexes. This hypothesis is supported by the distinct subcellular locations of the various AMPK subunits. Each of these unique AMPK complexes regulates discrete downstream processes that can be tumour suppressive or oncogenic. AMPK's final biological output is then determined by the weighted net function of these downstream signalling events, influenced by additional prostate-specific signalling.