Topological control of p21WAF1/CIP1 expression in normal and neoplastic tissues

El-Deiry, Wafik S., Tokino, Takashi, Waldman, Todd, Oliner, Jon D., Velculescu, Victor E., Burrell, Marilee, Hill, David E., Healy, Eugene, Rees, Jonathan L., Hamilton, Stanley R., Kinzler, Kenneth W. and Vogelstein, Bert (1995) Topological control of p21WAF1/CIP1 expression in normal and neoplastic tissues. Cancer Research, 55 (13), 2910-2919. (PMID:7796420)

Abstract

The p53-regulated gene product p21WAF1/CIP1 is the prototype of a family of small proteins that negatively regulate the cell cycle. To learn more about p21WAF1/CIP1 regulation in vivo, monoclonal antibodies were developed for immunohistochemistry. These revealed that p21WAF1/CIP1 expression followed radiation-induced DNA damage in human skin in a pattern consistent with its regulation by p53. A detailed comparison of the human, rat, and mouse p21WAF1/CIP1 promoter sequences revealed that this induction was probably mediated by conserved p53-binding sites upstream of the transcription start site. In unirradiated tissues, p21WAF1/CIP1 expression was apparently independent of p53 and was observed in a variety of cell types. Moreover, there was a striking compartmentalization of p21WAF1/CIP1 expression throughout the gastrointestinal tract that correlated with proliferation rather than differentiation. As epithelial cells migrated up the crypts, the Ki67-expressing proliferating compartment near the crypt base ended abruptly, with the coincident appearance of a nonproliferating compartment expressing p21WAF1/CIP1. In colonic neoplasms, this distinct compartmentalization was largely abrogated. Cell cycle inhibitors are thus subject to precise topological control, and escape from this regulation may be a critical feature of neoplastic transformation.

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