5-Fluorouracil causes leukocytes attraction in the peritoneal cavity by activating autophagy and HMGB1 release in colon carcinoma cells

Signals released by leukocytes contribute to tumor growth and influence the efficacy of antineoplastic treatments. The outcome of peritoneal carcinomatosis treatments is unsatisfactory, possibly because chemotherapy activates events that have in the long-term deleterious effects. In this study we offer evidence that 5-fluorouracile (5-FU), besides provoking apoptosis of MC38 colon carcinoma cells, induces a striking attraction of leukocytes both in an orthotopic model of colon carcinomatosis in vivo and in monocyte-migration assays in vitro. Leukocyte attraction depends on the presence of High Mobility Group Box 1 (HMGB1), an endogenous immune adjuvant and chemoattractant released by dying cells. Leukocyte recruitment is prevented in vivo and in vitro using blocking antibodies against HMGB1 and its competitive antagonist BoxA or by interfering with HMGB1 expression. Autophagy is required for leukocyte chemoattraction, since the latter abates upon pharmacological blockade of the autophagic flux while activation of autophagy per se, in the absence of death of colon carcinoma cells, is not sufficient to attract leukocytes. Our results identify autophagy induction and HMGB1 release in colon carcinoma cells as key events responsible for 5-FU elicited leukocyte attraction and define a novel rate-limiting target for combinatorial therapies. What's New? Anti-cancer drugs can sometimes help the tumors they are meant to destroy. One reason is because stressed or dying cancer cells release molecular factors that can attract leukocytes, and some of those leukocytes can contribute to tumor survival. In this study, the authors found that this is precisely what happens during intraperitoneal treatment of colon-cancer carcinomatosis with 5-fluorouracil (5-FU). Their results suggest that blocking autophagy and the release of HMGB1 are potential therapeutic targets for enhancing standard chemotherapy.