Suppression of colorectal tumorigenesis by recombinant Bacteroides fragilis enterotoxin-2 in vivo.

AIM: To evaluate the impact of recombinant Bacteroides fragilis enterotoxin-2 (BFT-2, or Fragilysin) on colorectal tumorigenesis in mice induced by azoxymethane/dextran sulfate sodium (AOM/DSS). METHODS: Recombinant proBFT-2 was expressed in Escherichia coli strain Rosetta (DE3) and BFT-2 was obtained and tested for its biological activity via colorectal adenocarcinoma cell strains SW-480. Seventy C57BL/6J mice were randomly divided into a blank (BC; n = 10), model (AD; n = 20), model + low-dose toxin (ADLT; n = 20, 10 µg), and a model + high-dose toxin (ADHT; n = 20, 20 µg) group. Mice weight, tumor formation and pathology were analyzed. Immunohistochemistry determined Ki-67 and Caspase-3 expression in normal and tumor tissues of colorectal mucosa. RESULTS: Recombinant BFT-2 was successfully obtained, along with its biological activity. The most obvious weight loss occurred in the AD group compared with the ADLT group (21.82 ± 0.68 vs 23.23 ± 0.91, P < 0.05) and the ADHT group (21.82 ± 0.68 vs 23.57 ± 1.06, P < 0.05). More tumors were found in the AD group than in the ADLT and ADHT groups (19.75 ± 3.30 vs 6.50 ± 1.73, P < 0.05; 19.75 ± 3.30 vs 6.00 ± 2.16, P < 0.05). Pathology showed that 12 mice had adenocarcinoma and 6 cases had adenoma in the AD group. Five mice had adenocarcinoma and 15 had adenoma in the ADLT group. Four mice had adenocarcinoma and 16 had adenoma in the ADHT group. The incidence of colorectal adenocarcinoma in both the ADHT group and the ADHT group was reduced compared to that in the AD group (P < 0.05, P < 0.05). The positive rate of Ki-67 in the ADLT group and the ADHT group was 50% and 40%, respectively, both of which were lower than that found in the AD group (94.44%, P < 0.05, P < 0.05). Caspase-3 expression in the ADLT group and the ADHT group was 45% and 55%, both of which were higher than that found in the BC group (16.67%, P < 0.05, P < 0.05). CONCLUSION: Oral administration with lower-dose biologically active recombinant BFT-2 inhibited colorectal tumorigenesis in mice.

Hyperthermic carbon dioxide pneumoperitoneum reinforces the inhibition of 5-FU on the proliferation and invasion of colon cancer.

The effect of hyperthermic carbon dioxide (CO2) pneumoperitoneum in combination with 5-fluorouracil (5-FU) on the proliferation and invasion of colon cancer was explored. Colon cancer cell line SW-480 was sealed into the urine collection bag to simulate pneumoperitoneum with 100% CO2 under a pressure of 12 mmHg. The cells were divided into group A, CO2 at 37˚C; group B, CO2 at 43˚C; group C, 5-FU; group D, CO2 at 37˚C+5-FU; group E, CO2 at 43˚C+5-FU; and control groups under normal culture conditions. The cell proliferation was assessed by CCK-8 test; the cell apoptosis was tested by FACS analysis; the cell invasion was examined by Transwell assay; the expression of HSP-70, caspase-3, HIF-1α and MMP-9 proteins and genes were detected by western blot analysis and RT-PCR. The SW-480 cells were injected into nude mouse cecum subserosal to establish a colon cancer model. We applied 43˚C CO2 pneumoperitoneum or 5-FU intraperitoneal chemotherapy to intervene, detected the transplantation tumor growth and metastasis. The cell proliferation was inhibited in groups B, C, D and E, apoptosis was induced in groups B, C, D and E, the Transwell cell number decreased in groups B, C, D and E, the transplantation tumor weight and metastasis rate were inhibited in groups B, C, D and E, but all not in group A. The most significant change was observed in group E. Hyperthermic CO2 pneumoperitoneum was able to reinforce the inhibition of 5-FU on proliferation and invasion of colon cancer.

Study on the inhibition of hyperthermic CO2 pneumoperitoneum on the proliferation and migration of colon cancer cells and its mechanism.

The present study explored the inhibitory effect of hyperthermic CO2 pneumoperitoneum on the proliferation and migration of colon cancer cells, and its mechanism. Colon cancer cell line SW-480 was sealed into a urine collection bag to simulate pneumoperitoneum with 100% CO2 under a pressure of 14 mmHg. The growth and morphology of cells were observed under a microscope, the inhibition on cell proliferation was measured using WST-8 test, cell apoptosis and the cell cycle were monitored using fluorescence-activated cell sorting analysis, the migration of cells was tested using the scratch assay, and the expression of HSP-70, caspase-3, hypoxia-inducible factor-1α (HIF-1α) and matrix metalloproteinase-9 (MMP-9) proteins and genes was investigated using western blotting and reverse transcription polymerase chain reaction. Compared with the control group, there was no significant difference in the CO2 group (P>0.05), while the apoptosis and necrosis rates in the hyperthermo-CO2 group was significantly increased (P<0.05). Compared with the control group, the number of cells at G0/G1 phase significantly increased and the number of cells at S phase significantly decreased in the hyperthermo-CO2 group (P<0.05), indicating that hyperthermo-CO2 could arrest the cell cycle. It was suggested by the results of the scratch assay that cell migration ability enhanced in the CO2 group, but decreased in the hyperthermo-CO2 group compared with the control. CO2 pneumoperitoneum promoted cell migration by upregulating HIF-1α and MMP-9 expression. However, the CO2 pneumoperitoneum with hyperthermia enhanced apoptosis and inhibited migration by upregulating the expression of HSP-70, HIF-1α and caspase-3, but downregulating the expression of MMP-9.