Hartmann A

Overexpression and mutations of p53 in metastatic malignant melanomas

Alterations of the p53 tumor suppressor gene are the most frequent genetic abnormalities in human malignancies, but the role of p53 in the etiology of malignant melanomas is unclear. Fifty unselected malignant melanomas were analyzed for p53 overexpression by immunohistochemistry using 3 monoclonal antibodies (MAbs). Fifteen tumors (29.4%) showed positive staining with at least 2 different antibodies. In the first 20 consecutive tumors exons 5–9 and adjacent splice sites of the p53 gene were analyzed by genomic sequencing. There were 4 mutations in 20 metastatic melanomas. Three of 4 mutations were C:G → T:A transitions. A search of our database of p53 mutations revealed that out of 8 p53 mutations reported by others, 4 are C:G → T:A transitions at dipyrimidine sites, and one is a tandem CC → TT mutation. This mutational pattern is comparable with the pattern of p53 mutations in squamous cell and basal cell carcinomas of the skin and is related to exposure to ultraviolet B (UV‐B) wavelength radiation. Taken together with a predominance of UV‐induced mutations in the CDKN2/p16 gene demonstrated in melanoma cell lines, our data support a role of sunlight exposure in the etiology of malignant melanoma. The low frequency of p53 mutants in melanomas compared with other types of skin cancers suggests that although mutations in this gene are likely to be involved in the development of some malignant melanomas, they do not play as large a role as in squamous and basal cell carcinomas of the skin.

Novel pattern of p53 gene mutations in an American black cohort with high mortality from breast cancer

The pattern of acquired mutations in the p53 gene can be used to study differences in factors contributing to carcinogenesis. We investigated mutations in exons 5-9 and adjacent intronic regions in 47 breast cancers of black women from Michigan, a population with the highest breast-cancer mortality in the US. The 16 mutations detected differed from those of other populations. In particular, the black women had an excess of A:T-->G:C transitions compared with rural white US midwest women. While the causes of the different pattern of acquired mutation remain to be determined, this molecular epidemiological approach detects the consequences of mutagenic processes in specific populations. Mutation patterns will constrain hypotheses to mechanisms consistent with the observed biochemical alterations.

A prospective trial of midwest breast cancer patients: A p53 gene mutation is the most important predictor of adverse outcome

Several retrospective studies have suggested p53 gene mutation as an adverse prognostic indicator in breast cancer patients, based on a selective growth advantage of p53 mutant cancer cells and their presumed resistance to current adjuvant therapy regimens. A cohort of 90 Caucasian midwestern breast cancer patients was analyzed prospectively (60 months of follow‐up) with a rigorous mutation detection methodology. The presence of a p53 gene mutation was the single most adverse prognostic indicator for recurrence (p = 0.0032) and death (p = 0.0001), and was associated with poor response to both adjuvant (p = 0.0001) and palliative (p = 0.006) therapy. Analysis of the p53 gene with appropriate mutation detection methodology markedly improves the prediction of early recurrence, treatment failure, and death in breast cancer patients. Int. J. Cancer (Pred. Oncol.) 89:32–38, 2000.

Mcm2 predicts recurrence hazard in stage Ta/T1 bladder cancer more accurately than CK20, Ki67 and histological grade

Stage Ta/T1 urothelial carcinoma of the bladder (Ta/T1 BC) has a marked tendency to recur. Besides histopathology, markers such as CK20 expression and proliferation index (Ki67) have been shown to predict its clinical course. The replication-licensing factor minichromosome maintenance protein 2 (Mcm2) is a marker of proliferative potential shown to be a promising prognostic marker in various malignancies. The aim of the present study was to evaluate the prognostic value of Mcm2 in comparison to stage, grade, CK20 and Ki67. Initial sporadic Ta/T1 BC (n=71) were evaluated for their expression of CK20, Ki67 and Mcm2 by immunohistochemistry and tissue microarray technology. Prognostic power was analysed by univariate and multivariate Cox regression model for tumour recurrence rate. Median follow-up period was 39 months. A total of 35% patients experienced recurrence. While CK20 was not predictive, grade, Ki67 and Mcm2 were significantly related to recurrence rate in univariate Cox regression model. Only grade (HR 2.37; 95% CI 1.24–4.51; P=0.009) and Mcm2 expression with a cutoff ⩾40% (HR 5.81; 95% CI 2.41–14.00; P<0.001) were independent predictors of recurrence rate in multivariate Cox regression analysis. In addition to grade, expression of Mcm2 is an independent predictor of recurrence in Ta/T1 BC.

Database of mutations in the p53 and APC tumor suppressor genes designed to facilitate molecular epidemiological analyses

Germline and somatic mutations in the p53 and APC genes contribute to neoplasia. The patterns of these and other acquired mutations in cancers reflect environmental mutagens and endogenous factors that contribute to carcinogenesis. Herein, we describe a database of almost 2,300 mutations in the p53 and APC genes published until September 1, 1993. In addition to cataloging the mutations, multiple fields of information have been added to facilitate future molecular epidemiological analyses of human cancer. The accuracy of the database has been checked by the present authors and, by soliciting feedback from the original corresponding authors. The strengths and limitations of the primary literature are discussed.

Expression of the lipid transporters ABCA3 and ABCA1 is diminished in human breast cancer tissue.

ATP-binding cassette transporters ABCA3 and ABCA1 are related to a differentiated, lipid-secreting phenotype of type II pneumocytes. Since mammary gland epithelial cells also show pronounced lipid metabolism and secretion, we investigated the expression of these proteins in normal as well as in neoplastic breast tissue. Normal human breast tissue, breast cancer cell lines, and 162 tumor samples of patients with primary unilateral invasive breast cancer were analyzed for ABCA3 and ABCA1 protein expression by immunohistochemistry using tissue microarrays. Strong ABCA3 and ABCA1 expression was found in the inner layer of normal mammary gland epithelium. Concurrent cytoplasmic ABCA3 and ABCA1 immunoreactivity was found in 9 of 11 breast cancer cell lines. ABCA3 and ABCA1 were shown to be differentially expressed in human breast cancer. Loss of ABCA3 staining was significantly associated with positive nodal status and negative progesterone receptor expression. In multivariate analysis, diminished ABCA3 expression proved to be a significant, independent and adverse risk factor for tumor recurrence. ABCA1 expression was associated with positive lymph nodes, but not significantly associated with tumor recurrence or breast cancer-specific survival. ABCA3 and ABCA1 are strongly expressed in normal mammary gland epithelium. Decreased ABCA3 expression in breast cancer seems to be associated with poor prognosis.

High frequency of p53 gene mutations in primary breast cancers in Japanese women, a low-incidence population

The pattern of acquired mutations in the p53 tumour-suppressor gene is potentially useful for determining factors contributing to carcinogenesis in diverse populations differing in incidence and/or mortality from the disease. We previously reported differences in mutational patterns of the p53 gene in primary breast cancers from Midwest US Caucasian, African-American and Austrian women. Herein, we report 16 mutations in 27 primary breast cancers from Japanese women from Hirosaki, a population with a low incidence of breast cancer. The frequency of 59.3% of p53 mutations is the highest reported in breast cancers from a particular ethnic group thus far. A relatively high number of mutations (7/16) were heterozygous in at least some tumour cell clusters. Intergroup comparisons of the mutational pattern between this population and several other US, European and Japanese populations do not show any statistically significant differences. There were recurrent mutations at two sites, codon 273 (R --> H; three mutations), a common hotspot of mutations in breast and other cancers, and codon 183 (S --> Stop; two mutations), a very rare location for p53 mutations. These mutations were shown to be independent and presumably not in the germ line. The highest frequency of p53 mutations raises the possibility that p53 mutagenesis is a predominant factor for breast cancer development in this low-risk Japanese group, whereas in other cohorts different mechanisms are likely to account for the higher proportion of breast cancer. Further studies are needed to confirm the present observations.

A polymorphism but no mutations in the GADD45 gene in breast cancers

The p53 gene product is part of a pathway regulating growth arrest at the G1 checkpoint of the cell cycle. Mutation of other components of this pathway, including the products of the ataxia telangiectasia (AT), GADD45, mdm2, and p21WAF1/CIP1 genes may have effects comparable to mutations in the p53 gene. The GADD45 gene is induced by ionizing radiation and several DNA-damaging xenobiotics. Induction requires the binding of wild-type p53 to an evoulutionarily highly conserved putative intronic p53 binding site in intron 3 of GADD45. We recently analyzed the entire coding region of the p53 gene in primary breast cancers of Midwestern white women and found 21 mutations among 53 tumors (39,6%). We now have shown by direct sequencing that there are no mutations in the intronic p53 binding site of the GADD45 gene in any of the 53 primary breast cancers and no mutations in the entire coding region of the GADD45 gene in a subset of 26 consecutive tumors (12 with p53 mutation and 14 without p53 mutation). The only sequence variation detected was a common polymorphism in intron 3. The absence of mutations in the GADD45 gene, including the putative p53-binding intronic site, suggests that this gene is not a frequent target of mutations in breast cancer. Although mutations of the p53 gene have been studied in a wide spectrum of human cancers, GADD45 has not been examined in any tumor or cell line to the best of our knowledge. Our results raise the possibility that mutation of the GADD45 gene alone is not functionally equivalent to loss of wild-type p53 activity.

Mutational activation of FGFR3: no involvement in the development of renal cell carcinoma

BackgroundSomatic point mutations in the fibroblast growth factor receptor 3 (FGFR3) gene have been identified in certain types of urological cancers, especially urothelial carcinoma of the bladder and the renal pelvis, and could be correlated with a favourable outcome. However, comprehensive data on the FGFR3 mutation status in renal cell carcinoma (RCC) are still missing.MethodsIn order to investigate a possible role for FGFR3 mutations in renal cell carcinogenesis, we performed a sequence-based mutational analysis of FGFR3 in 238 primary RCC. The cohort obtained the common RCC subtypes including 101 clear cell, 50 papillary and 68 chromophobe RCC specimens. The analysed regions encompassed all FGFR3 point mutations previously described in epithelial tumours and other noncutaneous epithelial malignancies.ResultsNo mutations were detected in any renal tumour type examined, and all cases showed wild-type sequence.ConclusionOur results argue against an involvement of mutational activation of FGFR3 in the development of RCC. A recently described cystic renal dysplasia in a patient with thanatophoric dysplasia type 1 due to a germ line FGFR3 mutation might portend to an involvement of mutational FGFR3 activation in renal cyst formation, but this speculation needs further evaluation.