To identify the tumor cells with high level of c-Jun, we examined c-Jun protein expression in 11 human tumor cell lines including CaCO2 (colon cancer), HCT116 (colon cancer), A375 (melanoma cancer), A549 (non-small cell lung carcinama), MKN-1 (gastric cancer), DU145 (prostate cancer), SKOV-3 (ovarian cancer), MDA-MB-231 (breast cancer), PC3 (prostate cancer), SF295 (glioblastoma cancer), and U251 (glioblastoma cancer). Here, JUN is linked to breast cancer.