No germline FH mutations in familial breast cancer patients

Fumarate hydratase: (FH) was recently identified as the predisposing gene for a tumor predisposition syndrome, hereditary leiomyomatosis and renal cell cancer (HLRCC) (MIM 605839). In HLRCC, individuals with a germline heterozygous mutation in the FH gene typically develop benign leiomyomas of the skin and the uterus (fibroids, myomas). In a subset of the families, predisposition to renal cell carcinoma and uterine leiomyosarcoma occurs. Other malignancies including breast cancer have also been detected in patients with a germline FH mutation. To examine whether FH could be involved in predisposition to breast cancer, we analyzed germline FH mutations from 85 Finnish breast cancer patients. Most of the cases were selected based on positive family or personal history for malignancies associated with HLRCC. No mutations were found. These results show that FH is not a major predisposing gene for familial breast cancer.     

TP53 mutations in familial breast cancer: functional aspects

Mutation in p53 (TP53) remains one of the most commonly described genetic events in human neoplasia. The occurrence of mutations is somewhat less common in sporadic breast carcinomas than in other cancers, with an overall frequency of about 20%. There is, however, evidence that p53 is mutated at a significantly higher frequency in breast carcinomas arising in carriers of germ-line BRCA1 and BRCA2 mutations. Some of the p53 mutants identified in BRCA1 and BRCA2 mutation carriers are either previously undescribed or infrequently reported in sporadic human cancers. Functional characterization of such mutants in various systems has revealed that they frequently possess properties not commonly associated with those occurring in sporadic cases: they retain apoptosis-inducing, transactivating, and growth-inhibitory activities similar to the wild-type protein, yet are compromised for transformation suppression and also possess an independent transforming phenotype. The occurrence of such mutants in familial breast cancer implies the operation of distinct selective pressures during tumorigenesis in BRCA-associated breast cancers.     

Three germline mutations in the TP53 gene

Three germline mutations in the TP53 tumor-suppressor gene are reported, two of which are not reported previously. A missense mutation at codon 265 of TP53 was found in three patients of a family that complied with the definition of the Li-Fraumeni syndrome. A nonsense mutation in codon 306 was found in a woman who had had a rhabdomyosarcoma at age 4 and a subsequent breast cancer at age 22. She was part of a Li-Fraumeni-like family, but the parental origin of the mutation could not be traced. Finally, while screening for somatic alterations in TP53 in a series of 141 sporadic breast tumors, we detected a constitutional missense mutation in codon 235 in a woman diagnosed with breast cancer at age 26 and a recurrence 4 years later. The recurrence, but not the primary tumor, showed an additional missense mutation at codon 245 as well as loss of the wild-type allele. This suggests that the 245 mutation was particularly important for tumor progression and that there might exist heterogeneity in terms of cancer predisposition potential among the various germline TP53 mutations. Hum Mutat 9:157–163, 1997. © 1997 Wiley-Liss, Inc.     

Childhood adrenocortical carcinoma as a sentinel cancer for detecting families with germline TP53 mutations

Choong SS, Latiff ZA, Mohamed M, Lim LLW, Chen KS, Vengidasan L, Razali H, Abdul Rahman EJ, Ariffin H for Malaysian Society of Paediatric Haematology‐Oncology. Childhood adrenal cortical carcinoma as a sentinel cancer for detecting families with germline TP53 mutations. Li‐Fraumeni syndrome (LFS) is a highly penetrant, autosomal dominant disorder where affected individuals carry a 50% risk of developing cancer before 30 years of age. It is most commonly associated with mutations in the tumour suppressor gene, TP53. Adrenocortical carcinoma (ACC) is a very rare paediatric cancer, and up to 80% of affected children are found to carry germline TP53 mutations. Hence, we propose using childhood ACC incidence as selection criteria for referral for TP53 mutation testing, independent of familial cancer history. Under the auspices of the Malaysian Society of Paediatric Haematology–Oncology, four eligible children diagnosed with ACC over a 30‐month study period were referred for mutation testing. Three had a germline TP53 mutation. Subsequent TP53 testing in relatives showed two inherited mutations and one de novo mutation. These findings strongly support paediatric ACC as a useful sentinel cancer for initiating a germline TP53/LFS detection programme, particularly in countries where the lack of structured oncogenetic practice precludes the identification of families with LFS features.     

BRCA1 germline mutations in Indian familial breast cancer

Germline mutation analysis of BRCA1 gene has demonstrated significant allelic heterogeneity. These differences represent historical influences of migration, population structure and geographic or cultural isolation. To date, there have been no reports of Indian families with mutations in BRCA1. We have screened for mutations in selected coding exons of BRCA1 and their flanking intron regions in three breast or breast and ovarian cancer families with family history of three or more cases of breast cancer under age 45 and/or ovarian cancer at any age. We have also analyzed 10 female patients with sporadic breast cancer regardless of age and family history, as well as 50 unrelated normal individuals as controls. Thus a total of 90 samples were analyzed for BRCA1 mutations using polymerase chain reaction-mediated site directed mutagenesis (PSM) and single stranded conformation polymorphism (SSCP) analysis for various selected exons followed by sequencing of variant bands. Eight point mutations were identified. Two deleterious pathogenic, protein truncating non-sense mutations were detected in exon 11 (E1250X) and exon 20 (E1754X) and six novel and unique amino acid substitutions (F1734S, D1739Y, V1741G, Q1747H, P1749A, R1753K). One complex missense mutation of exon 20 [V1741G; P1749A] was seen in two out of three families and another complex combination of missense and non-sense mutations of the same exon [V1741G; E1754X] was observed in only one family. These complex mutations exist only in breast cancer families but not in control populations of women. Three splice site variants (IVS20+3A>C, IVS20+4A>T, IVS20+5A>T) and two intronic variants (IVS20+21_22insG, IVS20+21T>G) were also detected. In the group of 10 sporadic female patients no mutations were found.     

TP53 gene mutations in plasma DNA of cancer patients

Using different molecular techniques, DNA has been shown to be present in plasma of patients with several types of tumors. Mutations of TP53 are the most common genetic changes in human cancers. We investigated the presence of TP53 gene mutations in plasma DNA of breast and small cell lung cancer patients. Tumor and plasma DNA of 25 patients were studied by PCR‐SSCP and direct sequencing, through exons 5, 6, 7, and 8, of TP53. Six cases of mutations in tumor DNA were observed that, in 3 cases (50%), were also identified in plasma of the same patients. Mutations of the TP53 gene are seen in plasma DNA of cancer patients, and may prove to be a useful new tool in the management of these patients. Genes Chromosomes Cancer 24:160–161, 1999. © 1999 Wiley‐Liss, Inc.     

Analysis of BRCA1, TP53, and TSG101 germline mutations in German breast and/or ovarian cancer families

The establishment of esophageal cancer cell lines can facilitate the search for molecular mechanisms underlying its pathogenesis. Two novel human esophageal squamous cell carcinoma (ESCC) cell lines, HKESC-2 and HKESC-3, were established from a moderately differentiated ESCC of a 46-year-old Chinese woman and a well-differentiated ESCC of a 74-year-old Chinese man, both from Hong Kong. The pathological characteristics (morphological, immunohistochemical, and electron microscopic studies), tumorigenicity in nude mice, cytogenetic features, and DNA ploidy of the two cell lines were investigated. The two cell lines have been maintained in vitro for more than 17 months and passaged over 85 times for HKESC-2 and 58 times for HKESC-3. Both grew as monolayers, with a doubling time of 24 hours for HKESC-2 and 48 h for HKESC-3. Their squamous epithelial nature was authenticated by their strong immunopositivity with the anti-cytokeratin antibodies and the ultrastructural demonstration of tonofilaments and desmosomes. They are tumorigenic in nude mice and had DNA aneuploidy. G-banding cytogenetic analysis showed hyperdiploidy in HKESC-2 and near-tetraploidy in HKESC-3. Frequent breakpoints were noted at 1p22, 1p32, and 9q34 in HKESC-2 and at 1p31, 3p25, 3p14, 6q16, 6q21, 8p21, 9q34, 13q32, and 17q25 in HKESC-3. Comparative genomic hybridization analysis found that chromosomal gains were at 3q24-qter, 5q21-qter, 8q11-qter, 13q21-q31, 17q11-qter, 19, 22q22 for HKESC-2 and at 3q13-qter, 5p, 6p, 9q21-qter, 10q21-q22, 12q15-pter, 14q24-qter, 16, 17q24-qter, 20 for HKESC-3. Chromosomal losses were at 3p13-pter, 18q12-qter for HKESC-3. These two newly established cell lines will be useful tools in the study of the molecular pathogenesis and biological behavior of ESCC cells and for testing new therapeutic reagents for ESCC in the future.     

TP53 mutations in human skin cancers

The p53 gene (TP53) is mutated in numerous human cancers. We have used it as a molecular target to characterize the induction of mutations in human skin cancers. About 50% of all skin cancers in normal individuals exhibit p53 mutations. This frequency rises to 90% in skin cancers of patients with the DNA-repair deficiency known as xeroderma pigmentosum (XP). These mutations are characterized by a specific signature, attributed to the ultraviolet uvB part of the solar spectrum. In this review, we will describe different p53 mutation spectra, in relation to the various histopathological types of skin cancers such as basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and malignant melanoma as well as to the DNA repair efficiency of the patients. In particular, different mutational hot spots are found among the various spectra. We have tried to elucidate them in terms of induced DNA lesion hot spots, as well as speed of local nucleotide excision repair (NER) or sequence effects. The molecular analysis of these mutagenic characteristics should help in the understanding of the origin of human skin cancers in the general population.     

Germline TP53 mutations and Li-Fraumeni syndrome

There are now reports of nearly 250 independent germline TP53 (p53) mutations in over 100 publications. Such mutations are typically associated with Li-Fraumeni or Li-Fraumeni-like syndrome, although many have been identified in cohorts of patients with tumors considered to be typical of LFS. In general, the spectrum of mutations that has been detected in the germline reflects that found in tumors, although there are some notable exceptions in certain tumor types. Detailed knowledge of the pedigrees allows a comprehensive analysis of genotype-phenotype correlations and an understanding of the tumors that are associated with germline TP53 mutations. This review will discuss the spectrum of mutations and the methods for mutation detection, the tumors associated with inheritance of a germline mutation, and some of the ethical and clinical problems in patients with a germline TP53 mutation.     

Polymorphisms in apoptosis-related genes and TP53 mutations in non-small cell lung cancer

Apoptosis plays an essential role in the elimination of mutated or transformed cells from the body. Therefore, polymorphisms of apoptosis-related genes may lead to an alteration in apoptotic capacity, thereby affecting the occurrence of TP53 mutations in lung cancer. We investigated the relationship between potentially functional polymorphisms of apoptosis-related genes and TP53 mutations in non-small cell lung cancer (NSCLC). Twenty-seven single nucleotide polymorphisms in 20 apoptosis-related genes were genotyped by a sequenome mass spectrometry-based genotyping assay in 173 NSCLCs and the associations with TP53 mutations in the entire coding exons (exons 2-11), including splicing sites of the gene, were analyzed. None of the 27 polymorphisms was significantly associated with the occurrence of TP53 mutations. This suggests that apoptosis-related genes may not play an important role in the occurrence of TP53 mutations in lung cancer.     

BRCA2 germline mutations in Cypriot patients with familial breast/ovarian cancer

Germline mutations in the BRCA2 gene have been shown to be associated with familial female and male breast cancer. Mutations occur throughout the entire coding region of the gene, and there is considerable ethnic and geographical diversity in the deleterious mutations detected in different populations. No data exist on the role of the BRCA2 gene in the Cypriot population. In this study we present the results of characterizing mutations in the BRCA2 gene, in 26 Cypriot families with multiple cases of breast/ovarian cancer. The entire coding region, including splice sites, of BRCA2 were sequenced using cycle sequencing. In total 29 BRCA2 variants were detected which include 3 truncating mutations, 8 missense mutations, 6 polymorphisms and 12 intronic variants. The 3 truncating mutations are frameshift mutation 8984delG (exon 22), and two nonsense mutations, namely C1913X (exon 11) which is a novel mutation, and K3326X (exon 27). It is of interest that frameshift mutation 8984delG was the most frequent, since it was detected in 5 patients from three different families. Among the 6 polymorphisms detected, polymorphism T77T is novel and similarly 4 of the 12 intronic variants were also novel, namely IVS1+8G>A, IVS1-96insA, IVS4+36A>G and IVS11-51G>T. These results show that deleterious BRCA2 mutations, occur at the same frequency, about 20%, in Cypriot families, as that recorded in other European populations. We conclude that the BRCA2 gene plays a significant role in the familial breast cancer phenotype in the Cypriot population.     

TP53 and breast cancer

The TP53 gene (p53) is found altered in breast carcinomas in approximately 20-40% of all cases depending on tumor size and stage of the disease. It seems to be an early event in breast tumorigenesis. Several polymorphisms in the TP53 gene have been detected and their possible roles in breast cancer risk and association to type of cancer developed are discussed. The different mutation spectra seen in geographical and ethnic populations may be used to identify environmental exposure contributing to breast cancer development. The role of TP53 mutation as a prognostic marker is reviewed as well as its role as a predictor for therapy response. All data available on TP53 mutation analyses of human breast carcinomas, as well data from transgenic animal studies and experimental cell studies, support an important role for TP53 in mammary carcinogenesis.     

TP53 and ovarian cancer

Ovarian cancer represents the fourth most frequent type of cancer among females and is the leading cause of death from gynecological cancer in the western world. This review describes gene alterations in ovarian cancer. Specific emphasis is placed on genetic alterations and the prevalence of TP53 (p53) gene alterations in the distinct biological ovarian tumors (benign, borderline, and malignant) and histological subtypes (serous, mucinous, endometrioid, clear cell), as well as in BRCA1-associated hereditary ovarian cancer. Although multi-modality treatment regimens, including cytoreductive surgery and cisplatin-containing combination chemotherapy, have usefully prolonged survival, the overall cure rate of the disease has not changed dramatically. Ovarian cancer is difficult to eradicate completely by surgery and many patients have only a partial response to postoperative chemotherapy and/or many will develop chemotherapy resistance. All these important factors contribute to the poor prognosis of ovarian cancer patients. In this review, the putative prognostic or predictive value of TP53 in ovarian cancer is addressed.