The purpose of this study was to examine the effects of antitumor activity of the
venom from the spider Macrothele raven (Araneae, Hexathelidae) on the human
breast carcinoma cell line, MCF-7. The
spider venom affected cell viability in a dose- and time-dependent manner as observed by [(3)H]-methyl
thymidine incorporation assay. Cytotoxicity changes in MCF-7 cells caused by the
spider venom at concentrations of 10, 20, and 40 mug/mL were determined by
lactate dehydrogenase release assay. Flow cytometry showed that the
spider venom induced apoptosis and
necrosis of MCF-7 cells at these concentrations. MCF-7 cells treated with
spider venom were accumulated on the G(2)/M and G(0)/G(1) phases. In addition, Western blotting analysis indicated that one of the pharmacological mechanisms of
spider venom was to activate the expression of p21. In vivo examination of the inhibition of
tumor growth in nude mice by the
spider venom (at concentrations of 1.6, 1.8, and 2.0 mug/g mice) revealed that
tumor size significantly decreased compared to controls by 21 days of treatment and at all points of analysis thereafter for 7 weeks (p < 0.01). We thus propose that the in vivo and in vitro effects of the
spider venom can be possibly estimated.