ABSTRACT
ETHNOPHARMACOLOGICAL RELEVANCE: Himatanthus drasticus (Mart.) Plumel - Apocynaceae is a medicinal plant popularly known as Janaguba. Its bark and latex have been used by the public for cancer treatment, among other medicinal uses. However, there is almost no scientific research report on its medicinal properties. AIM OF THE STUDY: The aim of this study was to investigate the antitumor effects of Himatanthus drasticus latex proteins (HdLP) in experimental models. MATERIALS AND METHODS: The in vitro cytotoxic activity of the HdLP was determined on cultured tumor cells. HdLP was also tested for its ability to induce lysis of mouse erythrocytes. In vivo antitumor activity was assessed in two experimental models, Sarcoma 180 and Walker 256 carcinosarcoma. Additionally, its effects on the immunological system were also investigated. RESULTS: HdLP did not show any significant in vitro cytotoxic effect at experimental exposure levels. When intraperitoneally administered, HdLP was active against both in vivo experimental tumors. However, it was inactive by oral administration. The histopathological analysis indicates that the liver and kidney were only weakly affected by HdLP treatment. It was also demonstrated that HdLP acts as an immunomodulatory agent, increasing the production of OVA-specific antibodies. Additionally, it increased relative spleen weight and the incidence of megakaryocyte colonies. CONCLUSION: In summary, HdLP has some interesting anticancer activity that could be associated with its immunostimulating properties.