The immune response to carcinoma of the colon in a rat model: a temporal study

Clinical and in Vivo Response Following Surgery or Surgery Plus Adjuvant Chemotherapy or Immunotherapy for Colorectal Carcinoma in a Rat Model

Two cohorts of rats, 240 with colon cancer and 150 controls, were assessed clinically and immunologically for their response to tumour and its management which was either by surgical excision alone or by surgical excision combined with either adjuvant chemotherapy or immunotherapy. The histology and invasion characteristics were observed for similarity with those of human lesions. Metastases were found in liver, lymph nodes, the peritoneum or lungs in 27% of animals during follow up. Significantly fewer adjuvant-treated rats had metastases than those receiving surgery alone ( P < 0.05), and less total tumour weight was found in the adjuvant-treated rats at four ( P < 0.03) and six ( P < 0.001) weeks postoperatively. Animals in the adjuvant immunotherapy group survived longer than in either other group ( P < 0.001). The crude parameters of host response to tumour, body, spleen and mesenteric lymph node weight were recorded and the latter two indexed to body weight. The body weight of tumour and control rats increased significantly with time ( P < 0.04). The spleen and mesenteric node indices were significantly ( P < 0.04) greater in tumour than control rats and were varied by recurrent tumour growth and by the adjuvant treatment administered postoperatively.

Immune capability of rats with colorectal carcinoma treated by resection with or without 5-fluorouracil or levamisole

The immune status of rats with chemically induced colorectal tumors was investigated for 8 weeks following treatment by resection, resection plus 5-fluorouracil (5-FU), and resection plus levamisole. Normal rats without tumors were given identical treatment and acted as controls. Tumor rats regained their ability to respond to an allograft of allogeneic lymphocytes after surgical excision of the tumor for a short period. Adjuvant Levamisole treatment enhanced this responsiveness, but adjuvant 5-FU depressed it. The spleen and lymph node cells of tumor-bearing rats showed greater spontaneous and PHA-induced cytotoxicity for chicken red blood cells than control rats (P less than 0.001), and adjuvant therapy did not alter this response. However in control animals, levamisole treatment did augment the antibody-dependent cytotoxicity of their spleen and lymph node cells. Rats receiving tumor resection alone were immune by leukocyte migration inhibition at 8 weeks only, while those receiving either adjuvant exhibited an immune response to the same homogenate for 4 and 8 weeks.