In vivo delayed rejection of tumors and inhibition of delayed-type hypersensitivity by HT-29 human colonic adenocarcinoma cell line

Inhibition of interleukin-2 dependent immune responses by serum from patients with advanced gastrointestinal cancer

Immunotherapy with high-dose interleukin-2 (IL-2) fails to induce clinical responses in patients with advanced gastrointestinal cancer, but may be effective in patients with malignant melanoma or renal adenocarcinoma. The hypothesis that this failure may be related to immunosuppressive moieties present in patients with advanced gastrointestinal cancer was investigated. Serum samples from 93 patients (32 advanced gastrointestinal cancer, 22 localized gastrointestinal cancer, 13 melanoma/renal adenocarcinoma and 26 age-matched controls) were incubated with peripheral blood lymphocytes from healthy volunteers. The generation of cytolytic lymphokine-activated killer (LAK) cells and the allogeneic mixed lymphocyte response (MLR) were measured in-vitro. LAK effector cytotoxicity (mean % +/- SEM) was significantly (P < 0.05) decreased by serum from advanced gastrointestinal cancer patients (30 +/- 3) compared with that from controls (47 +/- 3), serum from patients with localized gastrointestinal cancer (49 +/- 2) or that from patients with melanoma or renal adenocarcinoma (51 +/- 2). MLR responses were also significantly (P < 0.05) decreased using advanced gastrointestinal cancer patients serum compared to controls. A dose-response phenomenon for suppression of MLR was observed. Serum from patients with melanoma or renal adenocarcinoma was not significantly different to control samples. The immunosuppressive properties of serum from patients with advanced gastrointestinal carcinoma may abrogate therapeutic attempts using IL-2.

Combination of interferons and cytostatic drugs for treatment of advanced colorectal cancer

Three phase I/II trials were performed in patients with metastatic colorectal cancer using immunochemotherapy--a combination of recombinant interferon beta and gamma with low doses of cytostatic drugs. The third regimen, consisting of a cytostatic component containing 5-fluorouracil plus carboplatin plus mitomycin C besides the interferons, produced a high remission rate of 47%: 14/30 patients responded. The tolerability of this protocol was good and it could be administered on an out-patient basis.

Suppression of the generation of lymphokine-activated killer (LAK) cells by serum-free supernatants of in vitro maintained tumour cell lines

Serum-free supernatants from in vitro maintained gastrointestinal cancer and melanoma cell lines inhibit the generation of lymphokine (IL-2) activated killer (LAK) cells in a time and dose-related manner. Concentrations as low as 5% can inhibit the generation of LAK cytotoxicity but inhibition of proliferation is not observed until higher concentrations are included in the culture system. Inhibition is not observed with supernatants from a breast cancer cell line nor with supernatants from normal cells. There was complete concordance between the capacity of the tumour cells themselves to inhibit LAK generation and the presence of inhibitory activity in the corresponding supernatant. The inhibitory factor(s) is stable after heating to 44 and 56 degrees C. Production of the inhibitory factor(s) is sensitive to metabolic inhibitors and has a molecular weight greater than 25 kD. The inhibition of LAK cell stimulation by tumour cells may partially explain the failure of adoptively transferred LAK cells and IL-2 therapy to cause tumour regression in man.