Induction of Apoptosis by the p53-273L (Arg arrow right Leu) Mutant in HSC3 Cells without Transactivation of p21 super(Waf1/Cip1/Sdi1) and bax

• Published in: Molecular carcinogenesis Vol. 26; no. 1; pp. 44 - 52
• Main Authors: Kaneuchi, Masanori, Yamashita, Toshiharu, Shindoh, Masanobu, Segawa, Kaoru, Takahashi, Shuji, Furuta, Itsuko, Fujimoto, Seiichiro, Fujinaga, Kei
• Format: Journal Article
• Language: English
• Published: 01.09.1999
• ISSN: 0899-1987

Codon 273 is one of the hot spots of missense mutation of the p53 tumor suppressor gene found in human cancers. We have previously reported that a mutation at codon 273, p53-273L (Arg arrow right Leu), suppresses cell growth despite its having no p53-specific transactivation activity. To further elucidate the mechanism of growth suppression caused by p53-273L, we used squamous cell carcinoma cell line HSC3 to isolate subclones containing Zn super(2+)-inducible wild-type (wt) p53, p53-175H, and p53-273L. Northern blot hybridization of the HSC3 cells possessing an inducible function of p53 as well as a luciferase assay for the p21 super(Waf1/Cip1/Sdi1) promoter showed that only wt p53 could induce p21 super(Waf1/Cip1/Sdi1) transcription. Meanwhile, the expression of bax remained unchanged between, before, and after the induction of any analyzed p53s. When wt p53 was induced in HSC3 cells cultured in medium containing 5% fetal bovine serum, cell growth was suppressed through G sub(1) arrest. On the other hand, in medium with 0.1% fetal bovine serum, the growth of HSC3 cells expressing p53-273L was suppressed to a greater degree than that of cells expressing wt p53. Flow cytometric analysis and DNA ladder formation revealed that, unlike wt p53-SN3- and p53-175H-expressing HSC3 cells, p53-273L-expressing cells contained a larger sub-G sub(1) fraction under this culture condition. These findings suggest that p53-273L can induce apoptosis in HSC3 cells without transactivation of p21 super(Waf1/Cip1/Sdi1) and bax.