Accession Number : ADA302398

Title :   Modulation of Cyclin Expression by C-MYC in Malignant and Nonmalignant Mammary Epithelial Cells.

Descriptive Note : Annual rept. 1 Sep 94-31 Aug 95,

Corporate Author : GEORGETOWN UNIV WASHINGTON DC

Personal Author(s) : Dickson, Robert B.

PDF Url : ADA302398

Report Date : SEP 1995

Pagination or Media Count : 32

Abstract : We studied cell cycle control in mammary epithelial cells (MECs) with constitutive c-myc expression. Myc overexpression decreased the doubling time of MECs by 6 h compared to parental lines. A1N4 and A1N4-myc cells were arrested in GO in the absence of EGF and were allowed to re-enter the cell cycle by replacing EGF. The A1N4-myc cel 5 began to enter S phase 12 h after EGF addition and percent cells in S phase peaked at 8 in contrast, parental cells did not enter S phase until 18 h and peaked at 24 h, suggesting that the decrease in doubling time was due to shortened Gi phase. In unsynchronized cells, myc overexpression had no effect on cyclin A or Dl expression. In arrested cel 5, cyclin expression was nearly undetectable and induction closely correlated with change in cell cycle phase. Our results are in contrast to reports that myc overexpressing fibroblasts exhibited altered cyclin expression compared to parental cells. Those change were probably due to the fact that the cells were unable to withdraw from the cell cycle and became apoptotic rather than growth arrested. Myc-overexpressing MECs which do ndergo apoptosis in the absence of EGF suggest that is the case. Myc83 cells did not down-regulate cyclin expression in the absence of EGF and continued to traverse the cell cycle while becoming apoptotic.

Descriptors :   *EPITHELIUM, *CELLS(BIOLOGY), *MAMMARY GLANDS, *BREAST CANCER, CONTRAST, CELLS, REPORTS, CYCLES, FIBROBLASTS, MODULATION.

Subject Categories : Medicine and Medical Research
      Anatomy and Physiology

Distribution Statement : APPROVED FOR PUBLIC RELEASE