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

Use of anti-VEGF adjuvant therapy in cancer: challenges and rationale

Several ongoing clinical studies are designed to test the efficacy of antiangiogenic therapies in the adjuvant setting, where the goal is to increase the cure rate in patients who have just undergone surgical resection of all visible disease. Tumors depend on angiogenesis to support their growth and progression and blockade of this process has proven to be a valid strategy for treating multiple types of advanced metastatic cancer. However, results from the first of these clinical adjuvant studies were disappointing, stimulating extensive debate as to the potential of this approach. It will require additional clinical studies before we realize whether the effects of angiogenic blockade are durable, and if they are able to cure a subset of patients with early stage cancer.

Regional chemotherapy for colorectal hepatic metastases: evidence for improved survival with new drug combinations

BACKGROUND

In patients with colorectal hepatic metastases, response rates with hepatic arterial infusion (HAI) FUdR (5-Fluoro-2-deoxyuridine) are significantly higher than with systemic fluoropyrimidines. We report a novel animal model of intrahepatic therapy for hepatic metastasis for the study of methods to increase response rates and improve survival. METHODS. BD-IX rats are injected intrasplenically with K12/TRb cells. When hepatic metastases are established, animals are treated with hepatic or systemic chemotherapy, and the response to treatment, survival, and cause of death is determined.

RESULTS

Significant responses were observed with low- and high-dose HAI FUdR (p = 0.03 and 0.001, respectively). Only high-dose FUdR controlled hepatic disease. HAI FUdR alone did not prolong survival compared with control, but combination systemic FUdR and HAI FUdR did (p = 0.04). Continuous HAI of either 5-fluorouridine or mitomycin C has not previously been reported. There was no significant difference in response to FUdR, 5-fluorouridine, or mitomycin C. However, combination HA bolus mitomycin C plus either HAI 5-fluorouridine or HAI mitomycin C showed synergy with improved survival compared with all treatment groups (p < 0.0001).

CONCLUSIONS

The combination of bolus hepatic artery mitomycin C with either HAI mitomycin C or HAI 5-fluorouridine yields significant response rates, and survival is improved by this novel combination therapy.

Levamisole/fluorouracil. A review of their pharmacology and adjuvant therapeutic use in colorectal cancer

The combination of the antimetabolite fluorouracil plus the immunomodulator levamisole is used as adjuvant therapy following surgical tumour removal in patients with Dukes' stage C colon cancer. Fluorouracil given alone in this setting results in only a modest improvement in survival rate, and levamisole monotherapy is clinically ineffective. Well controlled studies, however, demonstrate that combined levamisole/fluorouracil reduces the recurrence rate by between 31 and 41% and the total mortality rate by between 13 and 33% compared with surgery alone in patients with Dukes' stage C colon cancer after median follow-up of 3 or 7.75 years. The median time to recurrence and median survival time are also extended significantly by levamisole/fluorouracil compared with fluorouracil alone or no adjuvant treatment. Thus, levamisole/fluorouracil has been recommended as the standard adjuvant therapy for patients with Dukes' C colon cancer, against which new investigative regimens should be compared. Methods for optimising the impressive results already achieved with this combination, and using this as a basis for further progress should be the thrust of future trials.

Phenotype alteration in colon carcinoma cells: effect of in vivo passage?

A panel of rat colon adenocarcinoma cell lines (the Per series) were used to investigate the phenotype and karyotype changes induced by in vivo passage in the subcutis of athymic nude mice. One poorly and one well-differentiated tumor cell line were serially passaged through the athymic nude mouse and then back to the syngeneic rat host. Each of the primary and xenograft cell lines expressed fetal crypt cell ("CaCo") antigens. The well differentiated primary and xenograft lines (Per305, Per305N1, and Per305N2a) were different in each of their growth factor responsiveness in vitro [i.e. epidermal growth factor (EGF), bombesin, vasoactive intestinal peptide], their EGF receptor expression, their secretion of transforming growth factor-alpha, and their exhibition of anchorage independent (A-I) growth capabilities. The poorly differentiated primary and xenograft cell lines were also different but were all capable of A-I growth; their responsiveness to exogenous growth factor stimulation decreased with progressive in vivo passage, as did their basal unstimulated proliferation rate. Cytogenetic alterations detected were those associated with clinical specimens from various stages of malignancy, i. e. aneuploidy, structural aberrations, and marker chromosomes. Genetic and mitogenic individuality of each line demonstrated the diversity of the growth control mechanisms in neoplasms at different stages of progression.

Three new rat colon tumour cell lines from 1,2-dimethylhydrazine induced adenocarcinomas: morphology, karyotype and clonogenicity

Three different tumour cell lines (Per113, Per192, Per237) were established from colon adenocarcinomas induced by 1,2-dimethylhydrazine (DMH) inbred male Wistar/Wag rats. Each cell line had epithelial morphology and an abnormal karyotype. The three cell lines were clonogenic in semi-solid medium, but differed in growth factor response, culture characteristics and karyotype. Each cell line was stimulated differentially by epidermal growth factor (EGF) and bombesin in culture. Only Per192 would passage in vivo in athymic nude mice. Per 113 had modal chromosome number of 70 with multiple structural abnormalities; Per237 had 43 chromosomes with consistent trisomy of chromosome I; 20-25% of the cells in line Per192 were in the tetraploid range with multiple copies of chromosome I.

Experimental colorectal cancer as a model of human disease

Colorectal cancer may now be induced consistently in experimental animals by the carcinogen 1,2-dimethylhydrazine (DMH). Adenomas and adenocarcinomas are produced in the large bowel and these resemble human colorectal cancer both macroscopically, and in their clinical behaviour. They are a close model of human disease and may be used for the evaluation of anti-cancer therapies and for the development of a diagnostic test for colorectal cancer.

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.