A positive feedback between HIF1α and lysyl oxidase-like 2 dictates the Warburg Effect in Pancreatic Cancer

Abstract

Background Hypoxic microenvironment is common in solid tumors, particularly in pancreatic ductal adenocarcinoma (PDAC). The Warburg effect is known to facilitate cancer aggressiveness and has long been linked to hypoxia, yet the underlying mechanism remains largely unknown. Methods The expression pattern and prognostic value of LOXL2 was analyzed by immunohistochemistry. The effects of LOXL2 on cancer cell proliferation, migration, and invasion in vitro, tumor growth and metastasis in vivo were investigated by genetic manipulation of LOXL2 expression in human PDAC cell lines. The effects of LOXL2 on aerobic glycolysis were examined by glucose uptake, lactate production, and Seahorse Flux Analyzer. Quantitative real-time PCR, western blotting, immunofluorescence and other techniques were conducted to identify molecular mechanism. Results Lysyl oxidase-like 2 (LOXL2) is a hypoxia-responsive gene and is essential for the Warburg effect in pancreatic ductal adenocarcinoma (PDAC). LOXL2 stabilizes hypoxia-inducible factor 1α (HIF1α) from prolyl hydroxylase (PHD)-dependent hydroxylation via hydrogen peroxide generation, thereby facilitating the transcription of multiple glycolytic genes. Therefore, a positive feedback loop is existed between LOXL2 and HIF1α that facilitates glycolytic metabolism under hypoxia. LOXL2 couples the Warburg effect to tumor growth and metastasis in PDAC. Hijacking glycolysis largely compromises LOXL2-induced oncogenic activities. Conclusion Our results identify a hitherto unknown hypoxia-LOXL2-HIF1α axis in regulating the Warburg effect and provide an intriguing drug target for PDAC therapy.