Xenovaccinotherapy for colorectal cancer.

The objectives of this phase I-II trial were to assess the toxicity, immunological and clinical responses induced in 37 patients with stage IV colorectal cancer by the subcutaneous administration of a xenogenic polyantigenic vaccine (XPV) prepared from disrupted murine melanoma (B16) and carcinoma (LLC) cells. An inducing course of vaccinotherapy consisted of 10 immunizations (5 at weekly and 5 at fortnight intervals). Twenty-four hours later each of first 5 vaccinations the patient was subcutaneously given a low dose of the recombinant interleukin-2 (IL-2). A consolidating course of vaccinotherapy consisted of monthly vaccinations. No grade III or IV toxicities, but also laboratory and clinical signs of developing systemic autoimmune disorders were noted in any XPV-treated patient. A significant increase in cell-mediated immunoreactivity to both LLC and B16 antigens (Ags) occurred in the patients after inducing vaccinations, as determined by delayed-type hypersensitivity (DTH) skin reactions, as well as by blood lymphocyte proliferation responses. Vaccinations also led to increased cell-mediated reactivity to murine non-tumor, spleen cell (SC)-associated Ags. This reactivity, however, was not as significant as that to tumor-associated antigens (TAAs). XPV was also found to capable of generating IgG antibody-mediated responses. With immunotherapy concentrations of both interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) detectably elevated in patients' sera, suggesting intensification of T helper 1-/T helper 2-mediated responses in the XPV-treated patients. The average survival of the XPV-treated patients was noticeably superior than was that of the clinically comparable control patients (17 vs 7 months). Collectively the results suggest that xenogenic TAAs are safe to use, able to induce measurable cellular and humoral immune responses, and may be clinically effective in certain colorectal cancer patients.