Cytosolic calcium mobilization concomitant with cell retraction induced by sulphate in oral KB carcinoma cells.

Inorganic sulphate is known to induce cell retraction, a process which is important in the cancer metastatic cascade. Using laser scanning confocal microscopy, we showed that sulphate mobilizes intracellular Ca 2+ from cytosolic stores in human KB oral cavity epidermoid carcinoma cells as shown by a three fold rise in Ca 2+ sensitive Fluo-3 dye fluorescence. As Ca 2+ stores are known to be located in the endoplasmic reticulum (ER), we demonstrated the rich network of ER channels in the KB cells by microinjecting live cells with an ER membrane-specific dye (DiI). Within 16 minutes after incubation with sulphate, KB cells had retracted and were easily detachable. The reduction in cell profile area as quantified by image analysis with the confocal microscope was statistically significant (p < 10(-6), ANOVA test). This suggests an alternative novel pathway of cell rounding and retraction involving Ca 2+ release, induced via inorganic sulphate.