Cyclooxygenase-2 inhibition augments the hepatic antitumor effect of oral Salmonella typhimurium in a model of mouse metastatic colon cancer.
BACKGROUND
Oral inoculation with a nontoxic, attenuated strain of Salmonella typhimurium reduces tumor burden and improves survival in a mouse model of metastatic colon cancer. These effects are likely mediated by S. typhimurium-induced increases in hepatic natural killer leukocytes. Cyclooxygenase-2 inhibitors may mediate antitumor effects through antiangiogenic, immune, or proapoptotic pathways. We hypothesized that cyclooxygenase-2 inhibitors would act synergistically with S. typhimurium, resulting in additional antitumor effects.


METHODS
Four groups of mice were studied: control, S. typhimurium alone, cyclooxygenase-2 inhibitor alone, and S. typhimurium plus cyclooxygenase-2 inhibitor. Mice were given normal drinking water (control, S. typhimurium alone) or water with 1,600 parts per million cyclooxygenase-2 inhibitor (cyclooxygenase-2 inhibitor alone, and S. typhimurium plus cyclooxygenase-2 inhibitor) and orally inoculated with saline (control, cyclooxygenase-2 inhibitor alone) or 10(9) S. typhimurium (S. typhimurium alone, S. typhimurium plus cyclooxygenase-2 inhibitor). Twenty-four hours later, all mice underwent laparotomy, and 5 x 10(4) MCA38 murine adenocarcinoma cells were injected into the spleen. On Day 14, hepatic tumor number and tumor volume was quantitated and hepatic leukocytes were analyzed by flow cytometry.


RESULTS
Compared with control mice orally inoculated with saline, S. typhimurium-treated mice had fewer and smaller tumors; mice treated with cyclooxygenase-2 inhibitor alone had tumor burden similar to control mice, and mice treated with S. typhimurium plus cyclooxygenase-2 inhibitor had fewer and smaller tumors compared with all other groups. Increased liver natural killer cells and decreased CD4+ and CD8+ T cells were observed in both S. typhimurium-treated groups. No alterations in hepatic leukocyte phenotype were observed in mice receiving cyclooxygenase-2 inhibitor alone.


CONCLUSIONS
Oral cyclooxygenase-2 inhibitor appeared to act synergistically with S. typhimurium to reduce tumor burden. This combination therapy may have clinical application in the treatment or prevention of hepatic metastases associated with colorectal cancer.
Feltis
Brad A
BA
Department of Surgery, University of Minnesota, Minneapolis, Minnesota, USA.
Sahar
David A
DA
Kim
Adam S
AS
Saltzman
Dan A
DA
Leonard
Arnold S
AS
Sielaff
Timothy D
TD
D000230:Adenocarcinoma / Q000556:secondary* / Q000628:therapy*; D000284:Administration, Oral; D000704:Analysis of Variance; D000818:Animals; D003110:Colonic Neoplasms / Q000473:pathology*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D005434:Flow Cytometry; D007694:Killer Cells, Natural / Q000502:physiology; D008113:Liver Neoplasms / Q000556:secondary* / Q000628:therapy*; D051379:Mice; D012486:Salmonella typhimurium
D016861:Cyclooxygenase Inhibitors