Mononuclear leukocytes from mice with resected tumor induce resistance to transplantation of tumor cells to animals.

Experiments on male C57Bl/6 mice with intraperitoneally transplanted Ehrlich carcinoma and DBA/2 mice with subcutaneously transplanted S-91 melanoma showed that preliminary injection of mononuclear leukocytes obtained from animals 6-8 h after tumor resection induce resistance to transplantation of malignant transformed cells. Our results suggest that not only humoral factors, but also immunocompetent cells are involved in the regulation of tumor growth. The resistance to tumor transplantation was not induced by mononuclear leukocytes isolated over the first hours and 10-12 h after removal of the primary tumor node, which excludes the direct cytotoxic effect of these cells and suggests that this phenomenon is not associated with activation of the effector mechanisms for innate and adoptive immunity.

Evaluation of immunotherapy efficiency in mouse CaO-1 ovarian carcinoma treated by vaccines based on dendritic cells.

Injection of dendritic cells, pulsated by tumor lysate or mucin, containing CA 125 antigen, led to a more than 50% inhibition of tumor growth in female CBA mice with transplanted mouse pseudomucinous CaO-1 ovarian carcinoma in comparison with the control. Tumor-associated CA 125 antigen can be used for obtaining dendritic cell vaccines against ovarian malignant tumors. This trend will extend the potentialities of application of antitumor vaccines based on dendritic cells, as clinical use of this technology is limited by the need in patient's tumor material. Mucin, containing Ca 125 antigen, can be isolated from patient's serum or obtained by gene engineering technologies as a recombinant peptide.

Tumor-specific changes in mouse serum during Ehrlich carcinoma growth.

Using the method of flow cytofluorometry we found that proteinase activity eliminating antigenic determinants from the surface of tumor cells disappeared from the serum of mice with Ehrlich carcinoma. This activity towards Ehrlich carcinoma cells is present in the sera of mice without tumors and in mice with other transplanted tumors. The serum from mice of one strain with Ehrlich carcinoma showed no protease activity against Ehrlich carcinoma cells in mice of other strain. Hence, Ehrlich carcinoma growth is associated with tumor-specific changes in the serum resulting in disappearance of specific protease activity of the serum against tumor cells.

Plasma content of soluble fas antigen in patients with adrenal tumors and tumor-like pathologies.

We compared plasma content of soluble Fas antigen (sFas) in 59 patients with tumors and tumor-like pathologies of the adrenal cortex and medulla and 60 healthy donors (control). The incidence and content of sFas in the plasma from patients with adrenal tumors was significantly higher than in healthy donors. A direct correlation was found between sFas content and patient's age. The maximum sFas concentrations were found in patients with pheochromocytoma and aldosterone-producing adenoma. In patients with adrenocortical cancer plasma content of sFas was lower than in patients with tumors of other morphological types. Plasma sFas content in patients with adrenocortical cancer directly correlated with the size of tumors. Our results suggest that sFas plays a role in the pathogenesis of primary adrenal tumors.