Thus, the auto-S-palmitoylation assay discriminates between cancer-related zDHHC mutations that do or do not impact zDHHC activation and provides novel insight into the potential role of diminished zDHHC activation in breast cancer (zDHHC4), as well as prostate cancer and testicular germ cell tumor (zDHHC14). This evidence concerns the gene ZDHHC4 and breast cancer.