(A) Human PDAC PANC1 and HPAF-II cells were cultured in DMEM and treated with TNF-α in the presence of 13- cis RA or 1,25-VD3 for 24 hr. At the end of experiment, invasion of human PDAC cells was analyzed in Boyden chambers coating with Matrigel™ as described in Materials and Methods. Invasive human PDAC cells were counted as described above and the number of human PDAC cells invading into the lower side of the filter was measured as the invasion index. Different upper-case letters (A, B, C) represent statistically significant differences among subgroups in PANC-1 cells (P<0.05). Different lower-case letters (a, b, c) represent statistically significant differences among subgroups in HPAF-II cells (P<0.05). (B) Same conditions were performed to measure cell survival (at 24 hr time point) using MTT assay as described in Materials and Methods. Statistical significance is expressed as the mean ± SD (standard deviation) of three independent experiments. An asterisk (*) represent statistically significant differences in comparison with the untreated control subgroup(P<0.05).