Germline p53 mutation at codon 133 in a cancer-prone family

Characteristics of Li-Fraumeni Syndrome in Japan; A Review Study by the Special Committee of JSHT

Li-Fraumeni syndrome (LFS) is a hereditary cancer predisposition syndrome, and the majority of patients with LFS have been identified with germline variants in the p53 tumor suppressor (TP53) gene. In the past three decades, considerable case reports of TP53 germline variants have been published in Japan. To the best of our knowledge, there have been no large-scale studies of Japanese patients with LFS. In this study, we aimed to identify Japanese patients with TP53 germline variants and to reveal the characteristics of LFS in Japan. We collected reported cases by reviewing the medical literature and cases diagnosed at the institutions of the authors. We identified 68 individuals from 48 families with TP53 germline pathogenic or likely pathogenic variants. Of the 48 families, 35 (72.9%) had missense variants, most of which were located within the DNA-binding loop. A total of 128 tumors were identified in the 68 affected individuals. The 128 tumor sites were as follows: breast, 25; bones, 16; brain, 12; hematological, 11; soft tissues, 10; stomach, 10; lung, 10; colorectum, 10; adrenal gland, 9; liver, 4; and others, 11. Unique phenotype patterns of LFS were shown in Japan in comparison to those in a large national LFS cohort study in France. Above all, a higher frequency of patients with stomach cancer was observed in Japanese TP53 germline variant carriers. These results may provide useful information for the clinical management of LFS in Japan.

Immortalization of epithelial progenitor cells mediated by resveratrol

Within the hierarchy of epithelial stem cells, normal progenitor cells may express regulated telomerase during renewal cycles of proliferation and differentiation. Discontinuous telomerase activity may promote increased renewal capacity of progenitor cells, while deregulated/continuous telomerase activity may promote immortalization when differentiation and/or senescent pathways are compromised. In the present work, we show that resveratrol activates, while progesterone inactivates, continuous telomerase activity within 24 h in subpopulations of human Li-Fraumeni syndrome-derived breast epithelial cells. Resveratrol results in immortalization of mixed progenitor cells with mutant p53, but not human epithelial cells with wild type p53. Our results demonstrate the potential for renewing progenitor cells with mutant p53 to immortalize after continuous telomerase expression when exposed to certain environmental compounds. Understanding the effects of telomerase modulators on endogenous telomerase activity in progenitor cells is relevant to the role of immortalization in the initiation and progression of cancer subtypes.

BRCA1 and TP53 mutation spectrum of breast carcinoma in an ethnic population of Kashmir, an emerging high-risk area

Breast cancer shows geographical variation in its incidence, even within areas of ethnic homogeneity. Kashmir valley (India), over past few years, witnesses an increase in incidence and occurrence of familial, early onset, and male breast cancer in its unexplored ethnic population. Here, we make a preliminary attempt to estimate the nature and frequency of BRCA1 and TP53 gene mutations of breast cancer patients from Kashmir. PCR-SSCP analysis followed by direct sequencing revealed the presence of only two germline intronic variations (c.199+67T>C and c.5396+187T>C) in BRCA1 gene in only 5.26% (2/38) patients while as 44% (11/25) of sporadic breast cancer patients harboured significant amount of somatic mutations in TP53 (p=0.0074; OR=0.053). The 17 mutations found in TP53 in 11 patients, comprised of 13 substitutions [11 single-base (9 transitions+2 transversions), 1 double-base and 1 complex] and four insertions. The 11 substitutions represent missense mutations, leading to aminoacid substitution while as rest two were silent mutations. The four insertions represented three frame-shifts and one non-sense mutation. The mutation effect data was found to be significant (p=0.0002). Significant amount of mutations were found in exon 6 (p=0.04; OR=0.273) and a combination of exons 6 and 7 (p=0.0145; OR=14.22) of TP53. Comparison of mutation profile with other ethnic populations and regions reflected both differences and similarities indicating co-exposure to a unique set of risk factors. The differences could be due to exposure to particular environmental carcinogens; different lifestyle, reproductive pattern; dietary or cultural practices of Kashmiri women that need further investigations. The infrequent presence of germline BRCA1 mutations in our study agree with the idea that a great proportion of moderate risk breast cancer population could be due to the susceptibility genes distinct from BRCA1. However, high frequency of somatic TP53 gene mutations implicates TP53 as a predominant factor for breast carcinogenesis in moderate risk ethnic Kashmiri population. The study also suggests TP53 as a potential molecular marker and prognostic tool, at least in a subset of sporadic breast tumors.

Germline p53 mutations in a cohort with childhood sarcoma: sex differences in cancer risk

To characterize cancer risk in heterozygous p53 mutation carriers, we analyzed cancer incidence in 56 germline p53 mutation carriers and 3,201 noncarriers from 107 kindreds ascertained through patients with childhood soft-tissue sarcoma who were treated at the University of Texas M. D. Anderson Cancer Center. We systematically followed members in these kindreds for cancer incidence for >20 years and evaluated their p53 gene status. We found seven kindreds with germline p53 mutations that include both missense and truncation mutation types. Kaplan-Meier analysis showed similar cancer risks between 21 missense and 35 truncation p53 mutation carriers (log-rank chi(2)=0.04; P=.84). We found a significantly higher cancer risk in female carriers than in male carriers (log-rank chi(2)=12.1; P<.001), a difference not explained by an excess of sex-specific cancer. The calculated standardized incidence ratio (SIR) showed that mutation carriers had a risk for all types of cancer that was much higher than that for the general population (SIR = 41.1; 95% confidence interval [CI] 29.9-55.0) whereas noncarriers had a risk for all types of cancer that was similar to that in the general population (SIR = 0.9; 95% CI 0.8-1.0). The calculated SIRs showed a >100-fold higher risk of sarcoma, female breast cancer, and hematologic malignancies for the p53 mutation carriers and agreed with the findings of an earlier segregation analysis based on the same cohort. These results quantitatively illustrated the spectrum of cancer risk in germline p53 mutation carriers and will provide valuable reference for the evaluation and treatment of patients with cancer.

IL18 polymorphism is associated with an increased risk of Crohn's disease

BACKGROUND

The etiology of inflammatory bowel disease, which includes ulcerative colitis and Crohn's disease, has not yet been made clear. However, inflammatory bowel disease is recognized as a multifactorial disease, and innate genetic factors might contribute to the pathogenesis. Cytokine genes are thought to be important in inflammatory bowel disease. Recently, interleukin 18, cloned as a novel proinflammatory cytokine, has been implicated in inflammatory bowel disease, especially Crohn's disease.

METHODS

To identify germline mutations in patients with inflammatory bowel disease, the entire coding region of IL18 was examined using a DNA sequencing procedure.

RESULTS

No functional mutations were found, but a novel single nucleotide polymorphism (SNP) was identified as TCA/TCC at codon 35. In patients with Crohn's disease, the frequency of TCC allele carriers was significantly higher than in healthy controls (chi2 = 9.35, P = 0.002229, OR = 2.58, 95% CI = 1.39-4.80). Also, the magnitude of the association was more remarkable in females (chi2 = 16.36, P = 0.000052, OR = 8.17, 95% CI = 2.73-24.41). The TCC allele at codon 35 of IL18 may increase the risk for Crohn's disease, especially in females.

CONCLUSIONS

IL18 is probably one of several genes that determine susceptibility to Crohn's disease.

Analysis of p53 tumor suppressor gene in families with multiple glioma patients

The high incidence of gliomas in Li-Fraumeni families and the high frequency of somatic p53 mutations in sporadic glial tumors have raised the possibility that germline p53 mutations could play an important role in familial aggregation of gliomas. In the present study, 18 families with two or more gliomas were screened for germline p53 mutation. The families were identified through questionnaires sent to 369 consecutive glioma patients operated at Tampere University Hospital during 1983-1994. In these families, a family history of cancer was verified through the Finnish Cancer Registry. Interestingly, the questionnaires reveled only 15 of 57 cancers (index gliomas excluded) retrieved through the Cancer Registry. None of the 18 families fufilled the criteria for classic Li-Fraumeni syndrome. Immunostaining analysis of p53 protein accumulation suggested that alterations of the p53 gene are as common in familial as in sporadic gliomas. Sequencing analysis of exons 4-10 of the p53 gene revealed no germline mutations in any of the 18 families. Thus, although occasional glioma families carrying germline p53 mutations have been identified in earlier studies, systematic evaluation of familial glioma patients suggests that the p53 gene is not a common susceptibility gene in case of familial gliomas. The p53 tumor suppressor gene seems to have a similar role in the tumorigenesis of most familial and sporadic gliomas.

Familial and metachronous malignant lymphoma: absence of constitutional p53 mutations

Familial and metachronous aggregations of malignant lymphoma are well-documented, but the molecular basis of a predisposition for development of lymphoma is as yet unclear. Malignant lymphomas have been described as part of the spectrum of neoplasias in Li-Fraumeni syndrome (LFS), which is associated with constitutional mutations of p53. However, p53 germline mutations have also, albeit less frequently, been described in patients not fitting the clinical definition of LFS. To clarify whether a genetic predisposition for lymphoma is associated with constitutional p53 mutations, DNA from normal blood lymphocytes of 12 lymphoma patients with a family history of lymphoma and/or with metachronous lymphoma (median age 37 years) was examined for mutations of p53 exons 4-8. One patient had four first-degree relatives with Hodgkin's disease, acute leukemia, and carcinomas, but the family history did not fulfill criteria of LFS. Four patients with Hodgkin's disease were diagnosed with metachronous non-Hodgkin's lymphoma as a second malignant neoplasm. No constitutional p53 mutations were detected in any of these patients, implying that outside the clinical spectrum of LFS, constitutional p53 mutations are rare in patients with lymphomas.