Autotaxin inhibitor IOA-289 reduces gastrointestinal cancer progression in preclinical models

BACKGROUND: Autotaxin (ATX) is a secreted enzyme that converts lysophosphatidylcholine to lysophosphatidic acid (LPA). LPA stimulates cell proliferation and migration and promotes wound repair following tissue damage. ATX levels are directly correlated with stage and grade in several human cancers. Several small molecule ATX inhibitors have been developed in recent years. IOA-289 is a potent ATX inhibitor, developed to treat cancers containing fibrosis. In this study, we tested IOA-289 treatment on different gastrointestinal tract tumor cell lines, in order to evaluate its effects on viability and motility. METHODS: To determine the effects on cell viability and proliferation of treatment with increasing concentrations of IOA-289, we used the crystal violet assay, a clonogenic assay in matrigel, and we evaluated the inhibitor’s effect on formation of 3D spheroids in an in vitro model. The effect of IOA-289 on cell cycle phases was analysed with a redox dye reagent. Cell migration capacity was evaluated by wound healing assay and transwell migration assay. To evaluate the pro-apoptotic effect of the inhibitor, cells were stained with Annexin V and immunofluorescence and flow cytometry analysis were performed. An antibody array was also used, to discriminate, in various samples, the differential expression of 43 proteins involved in the apoptosis pathway. RESULTS: We found that IOA-289 is able to inhibit both growth and migration of gastrointestinal tract tumor cell lines, both in 2D (crystal violet assay) and 3D in vitro models (spheroid formation and clonogenic assay in matrigel). This effect is dose-dependent, and the drug is most effective when administered in FBS-free culture medium. The inhibitory effect on cell growth is due to a pro-apoptotic effect of IOA-289. Staining with FITC-conjugated Annexin V showed that IOA-289 induced a dose-dependent increase in fluorescence following incubation for 24 h, and apoptotic cells were also distinguished in flow cytometry using Annexin/PI staining. The antibody array shows that treatment with IOA-289 causes the increased expression of several pro-apoptotic proteins in all tested cell lines. CONCLUSIONS: These results indicate that IOA-289 may be an effective drug for the treatment of tumors of the gastrointestinal tract, particularly those characterized by a high degree of fibrosis.