The Role of Lysyl Oxidase in SRC-Dependent Proliferation and Metastasis of Colorectal Cancer

Abstract

Emerging evidence implicates lysyl oxidase (LOX), an extracellular matrix-modifying enzyme, in promoting metastasis of solid tumors. We investigated whether LOX plays an important role in the metastasis of colorectal cancer (CRC). We analyzed LOX expression in a patient CRC tissue microarray consisting of normal colon mucosa (n = 49), primary (n = 510), and metastatic (n = 198) tissues. LOX was overexpressed in CRC cell line SW480 (SW480+LOX), and the expression was knocked down in CRC cell line SW620 using LOX-specific short hairpin RNA (SW620+shLOX). Effect of LOX manipulation on three-dimensional cell proliferation and invasion was characterized in vitro. Effect of LOX manipulation on tumor proliferation and metastasis was investigated in a subcutaneous tumor mouse model (n = 3 mice per group) and in an intrasplenic metastatic mouse model (n = 3 mice per group). The mechanism of LOX-mediated effects via v-src sarcoma (Schmidt-Ruppin A-2) viral oncogene homolog (avian) (SRC) was investigated using dasatinib, an inhibitor of SRC activation. All statistical tests were two-sided. Compared with normal colon tissue (n = 49), LOX expression was statistically significantly increased in tumor tissues (n = 510) of CRC patients (P < .001), and a greater increase was observed in metastatic tissue (n = 198). SW480+LOX cells showed a statistically significantly increased three-dimensional proliferation (P = .037) and invasion (P = .015), whereas SW620+shLOX cells showed reduced proliferation (P = .011) and invasion (P = .013) compared with controls. Subcutaneous tumor growth in mice was statistically significantly increased in SW480+LOX tumors (P = .036) and decreased in SW620+shLOX tumors (P = .048), and metastasis was statistically significantly increased in SW480+LOX tumors (P = .044) and decreased in SW620+shLOX tumors (SW620 control vs SW620+shLOX, mean = 1.0 luminescent signal, 95% confidence interval = 0.3 to 1.7 luminescent signal, vs mean = 0.3 luminescent signal, 95% confidence interval = 0.1 to 0.5 luminescent signal; P = .035) compared with controls. LOX-mediated effects on tumor progression were associated with SRC activation, and these effects were inhibited by dasatinib. LOX showed an important role in CRC cell proliferation and metastasis and was dependent on the activation of SRC. These results have the potential to identify patients with high SRC activity, who may benefit from dasatinib treatment.