p53 mutations and overexpression in locally advanced breast cancers

Abstract

Summary Alterations in the p53 gene were analysed in 39 patients with locally advanced breast cancers (LABCs) (stage III-IV) with inflammatory signs in most cases (UICC stage T4d = 32 patients) by molecular and immunohistochemical (IHC) approaches. All patients were included in the same therapy protocol. Using polymerase chain reaction (PCR) and a single-strand conformational polymorphism migration technique (SSCP), the presence of mutations in exons 2-11, covering the entire coding sequence of the p53 gene, was evaluated. Using the mouse specific anti-human p53 monoclonal antibody (PAb 1801), we also looked for overexpression of the p53 protein in tissue sections. In 16 cases shifted bands were reproducibly identified by PCR-SSCP, and all but one (localised to exon 10) were in exons 5-8, the usual mutational hotspots. Fifteen of these 16 samples were sequenced and 14 of the suspected mutations (36%) were confirmed. Most of them (12) were single nucleotide substitutions, and transitions were more frequent (eight cases) than transversions (four cases). Fourteen of the tumour samples were positively stained with the monoclonal antibody PAb 1801, 11 with nuclear staining only, two with mixed cytoplasmic and nuclear staining and one with cytoplasmic staining only. Staining patterns were very heterogeneous in terms of the percentage of positive cells (10-75%) and their distribution in the tissue section (isolated foci or dispersed cells). In 11 of the 14 mutated cases a positive immunostaining was observed. The presence of a p53 mutation was significantly associated with larger tumour diameter (X2 = 7.490, P = 0.0062) and the presence of clinical metastases (stage IV) (X2 = 10.113, P = 0.0015). A non-statistically significant trend of association was observed between p53 mutation, negative oestrogen receptors and lower response rate to therapy. Our results in this group of patients and the heterogeneity of the staining of tumour cells in tissue sections suggest that p53 mutations could be a late event in this non-familial form of breast cancer.

Identification of tumour-associated and germ line p53 mutations in canine mammary cancer

“…The Ala125Val mutant p53 gene was isolated from the carcinoma indicating that the more aggressive mammary tumour of patient 5 was associated with a point mutation of the canine p53 gene. Such an association between p53 mutation and high grade tumours has been noted previously in human breast cancer patients (Faille et al, 1994;Berns et al, 1996;Hartmann et al, 1997). The observed C to T transition mutation of patient 5 may have been the result of de-amination of 5-methylcytosine at the CpG position within codon 125 (GCG).…”

“…This is consistent with a number of human p53 mutants that contain amino acid substitutions within the highly conserved central core domain (for example, see Rolley et al, 1995). Adoption of the mutant conformation is suggested to contribute to nuclear accumulation of mutant p53 protein within tumour cells (Faille et al, 1994). Indeed, the corresponding human p53 mutant, Ala138Val, has been shown to display an increase in nuclear p53 protein levels within breast cancer cells (Moll et al, 1992;Faille et al, 1994).…”

“…Adoption of the mutant conformation is suggested to contribute to nuclear accumulation of mutant p53 protein within tumour cells (Faille et al, 1994). Indeed, the corresponding human p53 mutant, Ala138Val, has been shown to display an increase in nuclear p53 protein levels within breast cancer cells (Moll et al, 1992;Faille et al, 1994). Thus, it is likely that Ala125Val p53 would show an increase in protein stability within the mammary carcinoma of patient 5.…”

“…This point mutation at codon 125 (GCG to GTG) within exon 5 results in a substitution from alanine to valine (Figure 1) and corresponds to the temperature-sensitive mutants Ala135Val of murine p53 (Martinez et al, 1991) and Ala138Val of human p53 Yamato et al, 1995). Mutation at the equivalent position in the human p53 gene has been observed in three breast cancer patients (Moll et al, 1992;Faille et al, 1994). Although not directly investigated, the lack of detectable wild-type p53 sequence within the carcinoma of patient 5 indicates that allelic loss of the p53 gene may have also occurred during tumorigenesis (Figure 1).…”

Overexpression of p53 mRNA in colorectal cancer and its relationship to p53 gene mutation

“…In contrast to previous findings (Kern et al, 1989), when tumours were classified according to their histological stage, a multivariate Cox model analysis showed that p53 mutation, rather than 17p allelic losses, was the only independent prognostic factor (Hamelin et al, 1994). Immunohistochemistry (IHC) studies have indicated that mutated p53 is overexpressed in premalignant head and neck lesions (Shin et al, 1994), oesophageal squamous cell carcinomas (Wagata et al, 1993), ovarian cancer (Kupryjanczyk et al, 1993), breast cancer (Faille et al, 1994) and hepatocellular carcinoma (Wolkmann et al, 1994). In colorectal cancer, overexpression of p53 protein has been correlated with poor short-term prognosis (Yamaguchi et al, 1992; p53 mRNA overexpression in colorectal cancer 529 1 00C 1OC 10 100'…”