Ectopic expression of Rsu-1 results in elevation of p21(CIP) and inhibits anchorage-independent growth of MCF7 breast cancer cells

F. Vasaturo, G. W. Dougherty, M. L. Cutler*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Signal transduction from tyrosine kinase receptors mediates growth regulation of breast cancer cells in part through the GTPase Ras and downstream kinases. Rsu-1 is a cDNA previously identified as an inhibitor of Ras-induced transformation. An HA-epitope tagged Rsu-1 cDNA was introduced into the MCF7 breast carcinoma cell line. Stable transfectants were selected and used for analysis of Rsu-1 expression on growth control and Ras-dependent kinase pathways. Assessment of biological activity of HA-Rsu-1 transfectants revealed that HA-Rsu-1 clones showed slower anchorage dependent growth rates than control MCF7 cell lines and a significant reduction in anchorage independent growth. Analysis of cell cycle regulatory proteins required for transit through G1 revealed that HA-Rsu-1 transfectant cell lines expressed elevated levels of p21(CIP) CDK inhibitor. Perturbations in signal transduction pathways which can be activated by Ras were detected in the HA-Rsu-1 transfectants. Exposure of serum-starved cells to EGF revealed that expression of HA-Rsu-1 increased ERK-2 kinase activation, decreased activation of Jun kinase and inhibited Rho-dependent Rho-alpha kinase (ROK) activity compared to control cells. While serum starvation reduced AKT activity to undetectable levels in HA-Rsu-1 transfectants but not in control MCF7 cells, activation of AKT kinase by serum was unaffected by HA-Rsu-1 expression. Finally, the level of c-myc transcription in HA-Rsu-1 transfectants reached only 60% of the MCF7 control cell line following serum stimulation of starved cells while Fos RNA levels were similar to control cells. These results demonstrate that increased Rsu-1 expression critically altered cell cycle regulation and growth of MCF7 cells as well as signaling pathways in MCF7 cells required for malignant growth.

Original languageEnglish
Pages (from-to)69-78
Number of pages10
JournalBreast Cancer Research and Treatment
Issue number1
StatePublished - 1 May 2000
Externally publishedYes


  • Agar growth
  • Erk
  • Jun kinase
  • MCF7
  • P21(WAF/CIP)
  • Rho kinase
  • Rsu-1


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