Journal of Circadian Rhythms Volume 6
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ResearchPeriod-2: a tumor suppressor gene in breast cancerShulin Xiang1 , Seth B Coffelt2 , Lulu Mao1 , Lin Yuan1 , Qi Cheng1 and Steven M Hill1,3  1Department of Structural and Cellular Biology, Tulane University Health Sciences Center, New Orleans, LA 70112, USA 2Department of Microbiology and Immunology, Tulane University Health Sciences Center, New Orleans, LA 70112, USA 3Tulane Cancer Center, Tulane University Health Sciences Center, New Orleans, LA 70112, USA author email corresponding author email
Journal of Circadian Rhythms 2008,
6:4doi:10.1186/1740-3391-6-4 Abstract
Previous reports have suggested that the ablation of the Period 2 gene (Per 2) leads to enhanced development of lymphoma and leukemia in mice. Employing immunoblot analyses, we have demonstrated that PER 2 is endogenously expressed in human breast epithelial cell lines but is not expressed or is expressed at significantly reduced level in human breast cancer cell lines. Expression of PER 2 in MCF-7 breast cancer cells significantly inhibited the growth of MCF-7 human breast cancer cells, and, when PER 2 was co-expressed with the Crytochrome 2 (Cry 2) gene, an even greater growth-inhibitory effect was observed. The inhibitory effect of PER 2 on breast cancer cells was also demonstrated by its suppression of the anchorage-independent growth of MCF-7 cells as evidenced by the reduced number and size of colonies. A corresponding blockade of MCF-7 cells in the G1 phase of the cell cycle was also observed in response to the expression of PER 2 alone or in combination with CRY 2. Expression of PER 2 also induced apoptosis of MCF-7 breast cancer cells as demonstrated by an increase in PARP [poly (ADP-ribose) polymerase] cleavage. Finally, our studies demonstrate that PER 2 expression in MCF-7 breast cancer cells is associated with a significant decrease in the expression of cyclin D1 and an up-regulation of p53 levels. |