Tepary Bean (Phaseolus acutifolius) Lectins as Modulators of Intracellular Calcium Mobilization in Breast Cancer and Normal Breast Cells.

Lectins are proteins that specifically recognize carbohydrates on cell membranes, triggering several cellular events such as apoptosis of cancer-transformed cells; however, the mechanisms of action remain incompletely understood. Our research group has reported that a concentrated fraction of Tepary bean lectins (Phaseolus acutifolius; TBLF) exhibits the concentration-dependent induction of apoptosis in colon cancer cells by caspase activation. It is well established that an increase in cytoplasmic calcium ([Ca(2+)](i)) initiates intracellular signals involved in processes such as exocytosis, gene transcription, apoptosis, cell cycle regulation, and muscle contraction, among others. Furthermore, dysregulated calcium signaling has been implicated in various diseases, including certain neurological disorders and cancer. In this study, we aim to demonstrate the effects of native TBLF lectins and a recombinant lectin (rTBL-1) on calcium mobility in breast cancer cells (MCF-7) and non-cancerous cells (MCF-12F). Both TBLF and rTBL-1 increased intracellular calcium concentrations and mobilized calcium from intracellular stores in a concentration-dependent manner; however, the two cell lines exhibited differential responses. While MCF-12F cells restored cytoplasmic calcium concentration, MCF-7 cells maintained a high intracellular calcium concentration. This strongly suggests that lectins can elicit differential cellular responses in cancer and non-cancer cells due to variations in their intrinsic mechanisms of calcium homeostasis. Finally, we demonstrated that TBLF and rTBL-1 can differentially alter Metabolic Cellular Activity (MCA) as a direct measure of cell viability (CVi) in both cell lines. These findings strengthen the evidence of the therapeutic potential of Tepary bean lectins. Undoubtedly, further studies will be necessary to elucidate the mechanisms underlying their applications.