Using the human breast cancer cell lines LCC1 (antiestrogen sensitive) and LCC9 (antiestrogen resistant) we found that either calcitriol or EB1089 lowered phosphorylation of IRE1α, JNK, and Bcl2, especially in LCC9 cells, suggesting that VitD has the potential to inhibit autophagy in these cells. This evidence concerns the gene MAPK8 and breast cancer.