Background: A major challenge in pancreatic cancer treatment is the resistance of human pancreatic cancer cells to apoptosis. Soy isoflavones and calpain inhibition have been suggested to exert inhibitory effects on cancer development and progression. We investigated the effects of the isoflavone containing beverage Haelan 951 and the calpain inhibitor PD150606 on the viability, growth and apoptosis of the human pancreatic cancer cell lines CAPAN-1 and BxPC-3, on the rat pancreatic cancer cell line AR42J, and on human fibroblasts as the control cell line.
Methods: Cellular viability and proliferation were determined using the LDH cytotoxicity and WST-1 assay, respectively. Apoptosis was detected by flow cytometric analyses of Annexin V-FITC labeled-cells, TUNEL assay and caspase activation. Student's t test or Mann-Whitney Rank Sum test were used to compare the data.
Results: Haelan concentrations lower than 8% showed no cytotoxic effects, whereas higher concentrations led to necrosis. Eight percent Haelan induced significant growth inhibition of CAPAN-1 and BxPC-3 cell lines by 30% and 35%, respectively, compared with the control. The proliferation rate of AR42J cells decreased by 50%, whereas the fibroblasts remained unaffected. An 1.1-fold increase in apoptosis was found in CAPAN-1 cells, whereas the number of apoptotic BxPC-3 cells was elevated 2-fold. The number of apoptotic AR42J cells and fibroblasts was elevated 1.5-fold, each. Inhibition of calpain activity amplified the Haelan-induced growth inhibition of CAPAN-1 and BxPC-3 cells, but failed to amplify the growth inhibition of Haelan-treated AR42J cells. In fibroblasts, calpain inhibition induced Haelan-independent growth inhibition. Calpain inhibition also amplified the Haelan-induced apoptotic activity in all cancer cell lines, but exerted no further effect in fibroblasts.
Conclusions: The proliferation-inhibiting and apoptosis-inducing effects of Haelan are highly dependent on cell type and concentration administered. The results show for the first time that Haelan may be a promising candidate in the treatment of human pancreatic cancer, and its anticancer activity may be potentiated when administered with calpain inhibitors.