Effects of tumor-suppressor lysyl oxidase propeptide on prostate cancer xenograft growth and its direct interactions with DNA repair pathways

• Published in: Oncogene 2015-04, Vol.34 (15), p.1928-1937
• Main Authors: Bais, M V, Ozdener, G B, Sonenshein, G E, Trackman, P C
• Format: Article
• Language: English
• Subjects: 631/337/1427; 631/67/581; 631/67/589/466; Animals; Apoptosis; Ataxia; Breast cancer; Care and treatment; Cell Biology; Cell death; Cell Line, Tumor; Cell Proliferation - drug effects; Chemotherapy; CHK2 protein; Collagen; Deoxyribonucleic acid; DNA; DNA Damage; DNA Repair; Elastin; Fibroblast growth factors; Genetic aspects; Genotoxicity; Human Genetics; Humans; Internal Medicine; Ionizing radiation; Kinases; Lysyl oxidase; Male; Medicine; Medicine & Public Health; Metastases; Mice; Mice, Nude; MRE11 protein; Mutation; Oncology; original-article; Oxidases; Peptides; Phosphorylation; Physiological aspects; Prostate cancer; Prostatic Neoplasms - genetics; Prostatic Neoplasms - metabolism; Prostatic Neoplasms - pathology; Prostatic Neoplasms - therapy; Protein-Lysine 6-Oxidase - biosynthesis; Protein-Lysine 6-Oxidase - genetics; Proteins; Risk factors; Tumor cell lines; Tumors; Xenograft Model Antitumor Assays; Xenografts
• ISSN: 0950-9232; 1476-5594
• DOI: 10.1038/onc.2014.147

Lysyl oxidase (LOX) is a multifunctional protein required for normal collagen and elastin biosynthesis and maturation. In addition, LOX has complex roles in cancer in which the lysyl oxidase propeptide (LOX-PP) domain of secreted pro-LOX has tumor-suppressor activity, while the active enzyme promotes metastasis. In prostate cancer cell lines, recombinant LOX-PP (rLOX-PP) inhibits the growth of PC3 cells in vitro by mechanisms that were not characterized, while in DU145 cells rLOX-PP targeted fibroblast growth factor signaling. Because rLOX-PP can enhance effects of a genotoxic chemotherapeutic on breast cancer cell apoptosis, we reasoned that rLOX-PP could target DNA repair pathways typically elevated in cancer. Here we demonstrate for the first time that rLOX-PP inhibits prostate xenograft growth in vivo and that activating phosphorylations of the key DNA repair molecules ataxia-telangiectasia mutated (ATM) and checkpoint kinase 2 (CHK2) are inhibited by rLOX-PP expression in vivo . In addition, in vitro studies showed that rLOX-PP inhibits radiation-induced activating phosphorylations of ATM and CHK2 and that exogenously added rLOX-PP protein can localize to the nucleus in both DU145 and PC3 cells. rLOX-PP pull-down studies resulted in detection of a protein complex with the nuclear DNA repair regulator MRE11 in both cell lines, and rLOX-PP localized to radiation-induced nuclear DNA repair foci. Finally, rLOX-PP was shown to sensitize both DU145 and PC3 cells to radiation-induced cell death determined in colony-formation assays. These data provide evidence that rLOX-PP has a nuclear mechanism of action in which it directly interacts with DNA repair proteins to sensitize prostate cancer cells to the effects of ionizing radiation.