Abstract 965: The role of LOX-mediated FAK phosphorylation in osteosarcoma metastasis

Abstract

Abstract Despite the use of chemotherapy and surgery, the development of metastasis remains to be the leading cause of death in patients with osteosarcoma. LOX encodes for lysyl oxidase, which is an enigmatic molecule in cancer by acting as a tumor suppressor in certain tumors, but a metastatic promoter in other tumors. To investigate the function of LOX, we generated LOX overexpression mutants in two osteosarcoma cell lines and showed that higher LOX expression promoted tumor cell proliferation and invasiveness. Using an orthotopic xenograft mouse model, we further showed that osteosarcoma cells with higher LOX expression produced a higher number of mice with pulmonary metastases than the parental cell line (n=9). To characterize the mechanism of LOX-mediated metastasis, we examined the protein expression of a panel of potential downstream targets. The results demonstrated that phospho-FAK (focal adhesion kinase) expression was increased in the LOX-overexpression mutant relative to the parental cell line. Using a small molecule inhibitor of FAK, we showed that it significantly reduced the LOX-mediated metastasis in the orthotopic xenograft model. To demonstrate the clinical significance of our findings, we analyzed the expression profiling and RNAseq datasets recently generated from the TARGET osteosarcoma study. A Kaplan-Meier analysis showed that a higher level of LOX expression significantly correlated with a poor outcome (p < 0.05) and a multivariate analysis indicated LOX remained to be significant after controlling for initial metastatic status. In addition, we have previously shown that p27 is frequently mislocalized in the cytoplasm of osteosarcoma cells and drives the development of metastasis through interacting with the PAK1-mediated actin cytoskeleton network. Our results showed that the expression of LOX was upregulated in p27-mislocalized osteosarcoma cell lines with high metastatic potential. A tissue microarray analysis showed that cytoplasmic p27 expression significantly correlated with LOX expression (p = 0.003). Together, our findings suggest that a novel link between p27 mislocalization and LOX expression. LOX plays a pivotal role in osteosarcoma metastasis by upregulating FAK phosphorylation. FAK inhibition is a potential therapeutic strategy to reduce the development of metastasis in osteosarcoma with LOX overexpression. Citation Format: Xiang Chen, John M. Hicks, Poonam Sarkar, Waleed M. Gaber, Tsz-Kwong MAN. The role of LOX-mediated FAK phosphorylation in osteosarcoma metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 965.