Role of Interleukin-6 (il-6) in the Growth of Ct26 Colorectal Cancer in a Murine Model

PURPOSE: This study is designed to investigate the role of surgery-induced levels of cytokines in affecting proliferation and migration of colon cancer cells. Clinical standards in the management of colon cancer and surgery-related differences in various cytokines have been predicted to correlate with the degree of trauma afflicted during surgery, ultimately impacting tumor growth and metastasis. Laparoscopic surgery is thought to stimulate less of an acute cytokine (IL-1β, TNF-α, IL-6) response than open surgery, thereby preserving normal immune function. The significance of the surgery-related differences in these cytokines may correlate with the degree of anterior abdominal wall trauma.

METHODS: Murine colon cancer CT26 cells were incubated in the absence or presence of 1-10 uM recombinant mouse IL-6. Protein expression of IL-6 and its receptor (IL-6R) was measured and the cell proliferation/cell viability and migration was monitored by in vitro biological assays. In the first set of in vivo studies, non-tumor bearing Balb/c mice and Balb/c mice injected subcutaneously with CT26 cells received an open or laparoscopic surgery (LAS). Serum levels of IL-6 were measured at 30 minutes, 2 hrs, 4 hrs, 6 hrs, 12 hrs, 24 hrs, and 48 hrs following surgery. In a second set of murine studies, 10 Balb/c mice received either an intraperitoneal (i.p.) or a subcutaneous (s.c.) injection of 1500 ng of recombinant mouse IL-6 immediately following s.c. injections of CT26 cells. Tumor growth was monitored by caliper measurements every three days for twenty-one days. Tumor-bearing mice that did not receive IL-6 injections served as controls.

RESULTS: Colon cancer CT26 cells growing in vitro express low levels of IL-6 and IL-6R. CT26 cell proliferation and migration was not significantly increased in the presence of recombinant IL-6. There is a significant decrease in tumor take, size and volume of subcutaneously growing CT26 cells in mice which received LAS surgery as compared to mice which received an open surgery, and control mice (no surgery). IL-6 levels in the open group peaked at 8 hours; in sharp contrast, IL-6 peaked in the LAS group at 4 hours. Interestingly, the peak (at their respective hours) in the open surgery group was significantly greater as compared to the LAS group. By 48 hours, the IL-6 levels for both groups normalized to baseline levels. Additionally, i.p. injection (and not the s.c. injection) of IL-6 into mice caused the most significant increase in tumor growth.

CONCLUSION: These data suggest that surgery-induced (and not tumor-derived) serum levels of IL-6 may play a crucial role in the in vivo growth of colon cancer. Understanding the differential effects of open versus laparoscopic surgery on the growth of colon cancer may significantly impact the immediate and long-term prognosis of colon cancer patients.

Session: Poster of Distinction

Program Number: P014

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