Angiopoietin-like protein 2 renders colorectal cancer cells resistant to chemotherapy by activating spleen tyrosine kinase-phosphoinositide 3-kinase-dependent anti-apoptotic signaling.
Bottom Line: Apoptosis induced by antineoplastic drug treatment was significantly decreased in SW480/ANGPTL2 compared to control cells.Expression of anti-apoptotic BCL-2 family genes was upregulated in SW480/ANGPTL2 compared to SW480/Ctrl cells.Furthermore, ANGPTL2 increased its own expression in a feedback loop by activating the spleen tyrosine kinase-nuclear factor of activated T cells (Syk-NFAT) pathway.
Affiliation: Department of Molecular Genetics, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.Show MeSH
Related in: MedlinePlus
Mentions: To assess a potential role for ANGPTL2 in enhancing survival of CRC cells treated with antineoplastic drugs, we established two independent SW480 lines constitutively expressing ANGPTL2 (SW480/ANGPTL2-1 and -2) and a control line expressing vector only (SW480/Ctrl). Western blotting and ELISA analyses confirmed that both SW480/ANGPTL2-1 and -2 cells showed similarly enhanced expression of ANGPTL2 protein in both cell lysates and in culture medium relative to SW480/Ctrl cells (Fig. 1a,b). However, we observed no significant difference in proliferation among all three lines at 24, 48 and 72 h after plating (Fig. 1c), indicating that ANGPTL2 protein secreted by CRC cells does not alter proliferation under normal growth conditions. Next, we carried out a cell viability assay 24 h after treatment of CRC cells with the apoptosis-inducing drug 5-FU.(17) Constitutive ANGPTL2 expression in SW480/ANGPTL2-1 and -2 cells increased cell viability following 5-FU treatment relative to control drug-treated control cells (SW480/Ctrl) (Fig. 1d). Thus, we used flow cytometry to evaluate the proportion of apoptosis following 5-FU treatment using double-staining with annexin V and 7-AAD. That proportion significantly decreased in SW480/ANGPTL2-1 or -2 compared to SW480/Ctrl cells (Fig. 1e). We also examined cell viability after treatment of cells with other antineoplastic drugs used to treat CRC, including irinotecan (CPT11), cisplatin (CDDP), and mitomycin C (MMC),(2,18) and observed similar results (Fig. S1). These findings suggest that constitutive expression of ANGPTL2 in SW480 cells increases their chemoresistance by inhibiting apoptosis.
Affiliation: Department of Molecular Genetics, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.