Fig. 6.

CACNG4 modulates calcium influx and VGCC antagonist binding kinetics (a) and (b) L-type calcium channel antagonists verapamil and amlodipine inhibit MCF7 and MDA-MB-231 breast cancer cell proliferation in a dosage dependent manner at 48hrs. Data are represented as mean of triplicate values (c) shRNA knockdown of CACNG4 results in rescue of inhibition of proliferation by amlodipine (0,1,5 and 10μM) in MCF7 breast cancer cells (d) Knockdown of CACNG4 increases serum induced Ca2+ influx and also leads to resistance to influx inhibiting concentrations of amlodipine in MDA-MB-231 breast cancer cells. Data for c and d are represented as mean ± SEM for triplicate values. (e) Down regulation of CACNG4 in breast cancer cells affects EGFR and calcium signaling pathways; AKT2, pAKT, and HDAC3 are down regulated while p-PKCZ is up regulated as confirmed by protein expression levels in MCF7 cells validating the mRNA results (f) Serum induced calcium influx in MDA-MB-231 cells is reduced when cells are treated individually with EGFR specific inhibitor Tryphostin AG148 or L-type VGCC antagonist amlodipine. The level of calcium influx is most strongly reduced when cells are treated with both calcium influx antagonists combined.