Osteopontin Levels Are Persistently Elevated for 4 weeks Following Minimally Invasive Colorectal Cancer Resection.

Introduction: Osteopontin (OPN) is an integrin binding phosphorylated glycoprotein secreted by macrophages and leukocytes that is found in extracellular fluids and sites of inflammation; various forms of CD44 serve as receptors. Osteopontin, expressed by numerous cancers, enhances tumor progression and angiogenesis via the PI3K/AKT and ERK mediated pathways in concert with Vascular Endothelial Growth Factor (VEGF); OPN also plays a role in wound healing. The impact of minimally invasive colorectal resection (MICR) for colorectal cancer (CRC) on plasma OPN levels is unknown. This study's goal was to assess blood levels during the first month after MICR.

Method: Patients undergoing MICR for CRC who were enrolled in an IRB approved tissue/prospective data bank for whom preoperative, postop Day (POD) 1, POD 3, and at least 1 late postop plasma sample (POD 7-34) were available were studied. Osteopontin levels were determined in duplicate via enzyme linked immunosorbent assay (ELISA) (results reported as mean ± SD). The Wilcoxon signed rank test was used for analysis (significance < .05).

Results: A total of 101 CRC patients (63% colon and 37% rectal) met study criteria. The mean preop OPN level was 89.2 ± 36.8 (ng/ml) for the entire group. Significantly elevated ( < .001) mean plasma levels were detected, vs preop, on POD1 (198.0 ± 67.4; n = 101), POD 3 (186.0 ± 72.6, n = 101), POD 7-13 (154.1 ± 70.2, n = 70), POD14-20 (146.7 ± 53.4, n=32), and POD 21-27 (123.0 ± 56.9, n = 25). No difference was noted at the POD 27-34 timepoint ( > .05).

Conclusion: Plasma OPN levels are significantly elevated over baseline for a month after MICR for CRC. The early rise in OPN levels may be related to the postop acute inflammatory response. The persistent elevation noted in weeks 2-4, however, may be a manifestation of wound healing in which OPN plays a role. Similar persistent plasma elevations of VEGF, angiopoietin 2 (ANG 2), and 11 other proangiogenic proteins have been noted and, collectively, may promote angiogenesis in residual tumors.