['Activated leukocyte cell adhesion molecule (ALCAM/CD166) is a 105-kDa transmembrane glycoprotein linked with cell migration and development and with cancer progression (malignant melanoma, prostate cancer and, very recently, breast cancer). This report is the first evaluation of ALCAM/CD166 in an estrogen-dependent (MCF-7) and a metastatic (MDA-MB-231) breast cancer cell line and a reference breast cell line (HBL-100). The effects of estrogen and anti-estrogen treatment, bcl-2 overexpression, and ALCAM gene silencing on ALCAM/CD166 protein concentration and cell survival were investigated.', 'Laser scanning cytometry, confocal microscopy, and Western blotting were used for the determination of ALCAM/CD166 protein and biochemical markers of apoptosis and autophagy.', '17-beta-estradiol increased and tamoxifen inhibited ALCAM/CD166 expression and survival of MCF-7 cells. Overexpression of the bcl2 gene in MCF-7 bcl2/neo, MDA-MB-231 bcl2/neo, and HBL-100 bcl2/neo cells significantly increased ALCAM/CD166 expression and was accompanied by decreasing MMP-2 concentrations. Appearance of the ALCAM/CD166 protein was noted in HBL-100 bcl2/neo in contrast to an almost undetectable level in HBL-100 cells. ALCAM gene silencing in MCF-7 cells decreased the concentration of BCL-2 and increased levels of apoptosis (89-kDa PARP, active caspase7) and autophagy (MAP1LC3, Beclin1) markers.'] Does aLCAM/CD166 protect breast cancer cells against apoptosis and autophagy?