Expression of hepaCAM is downregulated in cancers and induces senescence-like growth arrest via a p53/p21-dependent pathway in human breast cancer cells.
Previously, we reported the identification of a novel immunoglobulin-like cell adhesion molecule hepaCAM that is frequently downregulated and inhibits cell growth in hepatocellular carcinoma. In this study, we show that the expression of hepaCAM is suppressed in diverse human cancers. Aiming to evaluate the biological role of hepaCAM in breast cancer, we stably transfected the MCF7 cell line with either wild-type hepaCAM or its mutant hCAM-tailless that lacked the cytoplasmic domain. We found that hepaCAM inhibited colony formation and cell proliferation and arrested cells in the G(2)/M phase. Intriguingly, hepaCAM was capable of inducing cellular senescence as defined by the enlarged cell morphology and increased beta-galactosidase activity. Furthermore, hepaCAM elevated the expression levels of senescence-associated proteins including p53, p21 and p27. In contrast, cell growth inhibition and senescence were less apparent in cells overexpressing hCAM-tailless mutant. To determine if the p53-mediated pathway was involved in hepaCAM-induced senescence, we used the small-interfering RNA system to knock down endogenous p53 expression. In the presence of hepaCAM, downregulation of p53 resulted in a clear reduction of p21, insignificant change in p27 and alleviated senescence. Together, the results suggest that the expression of hepaCAM in MCF7 cells not only inhibits cell growth but also induces cellular senescence through the p53/21 pathway.
Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
Mei Chung
MC
Moh
Ting
T
Zhang
Lay Hoon
LH
Lee
Shali
S
Shen
D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D016922:Cellular Senescence / Q000502:physiology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D011506:Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; C487620:HEPACAM protein, human; D011506:Proteins; D016159:Tumor Suppressor Protein p53