Lack of cyclin-dependent kinase 4 inhibits c-myc tumorigenic activities in epithelial tissues

Paula L Miliani De Marval, Everardo Macias, Robert Rounbehler, Piotr Sicinski, Hiroaki Kiyokawa, David G. Johnson, Claudio J. Conti, Marcelo L. Rodriguez-Puebla*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

90 Scopus citations


The proto-oncogene c-myc encodes a transcription factor that is implicated in the regulation of cellular proliferation, differentiation, and apoptosis and that has also been found to be deregulated in several forms of human and experimental tumors. We have shown that forced expression of c-myc in epithelial tissues of transgenic mice (K5-Myc) resulted in keratinocyte hyperproliferation and the development of spontaneous tumors in the skin and oral cavity. Although a number of genes involved in cancer development are regulated by c-myc, the actual mechanisms leading to Myc-induced neoplasia are not known. Among the genes regulated by Myc is the cyclin-dependent kinase 4 (CDK4) gene. Interestingly, previous studies from our laboratory showed that the overexpression of CDK4 led to keratinocyte hyperproliferation, although no spontaneous tumor development was observed. Thus, we tested the hypothesis that CDK4 may be one of the critical downstream genes involved in Myc carcinogenesis. Our results showed that CDK4 inhibition in KS-Myc transgenic mice resulted in the complete inhibition of tumor development, suggesting that CDK4 is a critical mediator of tumor formation induced by deregulated Myc. Furthermore, a lack of CDK4 expression resulted in marked decreases in epidermal thickness and keratinocyte proliferation compared to the results obtained for K5-Myc littermates. Biochemical analysis of the K5-Myc epidermis showed that CDK4 mediates the proliferative activities of Myc by sequestering p21Cip1 and p27Kip1 and thereby indirectly activating CDK2 kinase activity. These results show that CDK4 mediates the proliferative and oncogenic activities of Myc in vivo through a mechanism that involves the sequestration of specific CDK inhibitors.

Original languageEnglish (US)
Pages (from-to)7538-7547
Number of pages10
JournalMolecular and cellular biology
Issue number17
StatePublished - Sep 2004

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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