Abstract 1228: Interleukin 8 (IL8) is a modulator of tumorigenicity in colon cancer initiating cells

Introduction: At least 20% of patients with ulcerative colitis (UC) will develop colitis associated cancer (CAC) within 30 years of disease onset. Furthermore, patients with UC have a 5 fold greater risk of developing CAC than the incidence of CRC in the general population. Recently, we isolated and propagated colon cancer initiating cells (CCICs) from UC and CRC patients, and showed that these cells generated tumors in mice and propagated as spheres in vitro. IL8 is a pro-inflammatory chemokine with known proliferation and migration properties. Previously, we showed that inhibition of IL8 inhibited the growth of CCIC-derived tumors in vivo. We hypothesize that IL8 modulates several cancer processes and potentiates the progression from colitis to cancer. Methods: Conditioned media from UC and CRC patient sphere cell isolate cultures were used for measurement of secreted IL8. Exogenous IL8 (10 ng/mL) was added to sphere cultures and proliferation was evaluated. In addition, we knocked down IL8 and IL8 receptor (CXCR1) expression in CRC cell line by short hairpin RNA (shRNA) and measured proliferation in vitro and tumor growth in vivo. We then monitored CCICs from UC or CRC patients, either in the presence or absence of IL8, for symmetric vs. asymmetric division via time lapse video. Results: The chemokine array showed an increase in IL8 in both UC and CRC spheres. Spheres treated with IL8 proliferated faster than controls. Sphere numbers increased with increased exposure to IL8 on days 5 and 7. Conditioned media concentrations of IL8 were increased in both CRC (361-2446 pg/mL) and colitic spheres (208-599 pg/mL) when compared to commercial CRC cell lines (HT29-20.8 and SW480-74.6, respectively). In vitro, knockdown of IL8 or CXCR1 decreased proliferation 1.8-fold compared to the non-targeting controls. Similarly, in vivo xenografts of IL8 or CXCR1 knockdown cells showed 80% decreased tumor growth. UC-derived CCICs exposed to exogenous IL8 exhibited an increase in proliferation starting as early as 16 hrs. We also observed that IL8 treated cells showed a higher percentage of symmetric cellular divisions (68%) when compared to untreated cells (42%). Conclusions: Our findings demonstrate that IL8 potentiates proliferation and symmetric cell division, which is thought to be associated with tumorigenicity. This indicates that IL8 may contribute to the progression of colitis-associated cancer through a modulation of tumorigenic processes. Citation Format: {Author