TETRANDRINE: A NOVEL CHEMOPREVENTIVE AGENT

Purpose: The development and study of chemopreventive agents may be promising in combating aggressive behavior of triple-negative breast cancer. Tetrandrine, a bis-benzylisoquinoline alkaloid isolated from the root of Stephania tetrandra, is a calcium channel blocker used in Chinese medicine for the treatment of silicosis and arthritis. Studies have shown that tetrandrine also has anti-tumor and anti-growth activities. Our objective is to study the effects of tetrandrine on the localization of Annexin A2 (36 kDa calcium-dependent phospholipid binding protein) and determine the implication of this in the overall cell proliferation and cancer metastasis processes. We hypothesize that inhibition of calcium trafficking by tetrandrine will inhibit the migration, invasion and proliferation via attenuation of AnxA2 localization to the plasma membrane Methods: We have used Her-2 positive, triple-negative, and non-cancerous breast cell lines (MDA-MB-231, HCC70, BT474, SKBR3, and MCF-10A) to study the effects of tetrandrine. MTT assays were carried out to determine the effect of tetrandrine on cell viability. Additionally, cells were subjected to the Versene wash to analyze the effect of calcium depletion on the AnnXA2 localization in cells. Effects of tetrandrine on the expression and localization of Annexin A2 were also analyzed by the immunofluorescence and the Western blot analyses of the sub cellular fractions of the control and treated cells. Results: The viability of the cells at various concentrations of tetrandrine after incubation of 48 h measured by MTT assay showed IC50 values of 20uM, 25uM, 30uM, 40uM, and 75uM for HCC70, MDA MB231, SKBR3, BT474, and MCF10A respectively. Annexin A2 translocation to the membrane was analyzed by using a) versene (calcium ion chelating agent) washed cells, b) Western blot analyses of membrane and cytosolic extracts and c) Immunofluorescence of control and tetrandrine treated cells. Results of these studies indicated that treatment of breast cancer cells with tetrandrine did not show any significant effect on the Annx.A2 accumulation in plasma membrane of these cells when compared with the control cells. Conclusions: Our results suggest that tetrandrine inhibits the proliferation of breast cancer cells through mechanisms independent of Annexin A2. Significantly high IC50 value for MCF10A compared to the breast cancer cells indicates that this phyto-chemical may be used as a cancer chemopreventive agent.