Expression of a p53 mutant in the epidermis of transgenic mice accelerates chemical carcinogenesis

Abstract

To develop an in vivo model for studying the role of the p53 tumor suppressor in skin carcinogenesis, a murine p53 172H mutant (equivalent to human p53 175H ) was expressed in the epidermis of transgenic mice, utilizing a targeting vector based on the human keratin 1 gene (HK1.p53 m ). HK1.p53 m mice developed normally and did not exhibit an obvious epidermal phenotype or develop spontaneous tumors. However, these mice demonstrated an increased susceptibility to a two-stage chemical carcinogenesis protocol, with the rate of formation and number of papillomas being dramatically increased as compared to non-transgenic controls. The majority of papillomas in control mice regressed after termination of 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment, whereas p53 m papillomas progressed to carcinomas and metastases. In addition, more advanced malignancy, i.e., undierentiated spindle cell carcinomas, were exclusively observed in p53 m mice. Increased bromodeoxyuridine (BrdU) labeling, accompanied by decreased expression of p21, was observed in HK1.p53 m papillomas. In situ examination of centrosomes in HK1.p53 m papillomas also revealed marked abnormalities, with 75% of the cells containing 53 centrosomes/cell, whereas centrosome numbers in papillomas from control animals remained normal. These data suggest that the accelerated tumorigenesis observed in chemically-treated p53 m mice is most likely due to increased genomic instability resulting from an inhibition of G1 arrest and abnormal ampli®cation of centrosomes.

Cooperative interaction between mutant p53 and des(1-3)IGF-I accelerates mammary tumorigenesis

“…Previous studies (Li et al, 1998;Wang et al, 1998) have demonstrated aneuploidy in both mammary and skin tumors occurring in DMBA-treated mice carrying a targeted p53 172R-H transgene. To determine if p53 172R-H expression results in a predisposition to aneuploidy in the context of the WAP-DES transgene, FACS analysis was conducted on tumor cell nuclei.…”

“…Both faint and intensely stained nuclei were pooled for quantitation purposes. Quantitation of Ki 67 positive cells was conducted as described in (Wang et al, 1998). These e ects appear to be due to the gain of function properties of this p53 mutant and may be independent of direct e ects of p53 on gene transcription (Gualberto et al, 1999).…”

Aberrant cell cycle progression contributes to the early-stage accelerated carcinogenesis in transgenic epidermis expressing the dominant negative TGFβRII

“…RNase protection assays (RPA) were performed using the RPA II kit (Ambion, TX, USA) and 32 Plabeled riboprobes. Riboprobe speci®c for p21 (WAF-1) was generated as previously described (Wang et al, 1998a). The SmaI/SacII fragment of murine p15 (INK4b) cDNA (kindly provided by Dr Charles J Sherr) was subcloned into pGem 5 (Promega), and linearized with ApaI as the template of the p15 riboprobe.…”

Mutant mouse p53 transgene elevates the chemical induction of tumors that respond to gene silencing with siRNA

“…9 Mice carrying p53 mutations analogous to the human Li-Fraumeni syndrome hot spot mutation exhibit a high incidence of spontaneous tumors with a spectrum different from that of p53-null mice, [10][11][12] a high metastatic potential for produced tumors 13 and a high incidence of chemically induced tumors. 14 Especially of note is an approach toward simulating the human context with heterozygous mice containing human p53 and Li-Fraumeni mutant p53 in the genome. 12 At the initial step of carcinogenesis caused by p53 mutation, there must exist a heterozygous state of wildtype p53 with mutant p53, resulting in the expression of both types of p53 proteins.…”