RESUMEN
Introduction: The aim of the present study was to describe different biological aspects of Ehrlich tumor in mice, such as body weight evolution, tumor growth rate, histological organization and systemic immune response after treatment with high-diluted thymulin (10-9 M, named 5CH). Methods: Tumor assessment was focused on macro- and microscopic aspects; parameters included occurrence of necrosis, embolism and tumor development, in addition to quantitative analysis of apoptosis (caspase-3), cell proliferation (Ki-67) and angiogenesis (vascular endothelial growth factor - VEGF) by means of specific immunohistochemistry markers. Spleen cell populations were evaluated by flow cytometry analysis. Results: Mice treated with thymulin 5CH exhibited changes in the tumor microenvironment, such as reduced micro-embolism incidence and cytokeratin expression, with increased caspase-3 expression in the tumor cells. These findings indicate some apoptotic activity by the tumor cells induced by the treatment, even though no reduction of the macroscopic tumor mass occurred. No changes in the systemic immune response were detected, as the balance among spleen cell populations remained unchanged. Conclusions: The results indicate that treatment of mice bearing Ehrlich tumor with thymulin 5CH induces some specific changes in the tumor environment. However, it did not influence systemic immunity parameters. Adjuvant use of thymulin 5CH in oncological clinical practice is still a matter of discussion. (AU)