Li-Fraumeni-like Research Articles

Germline TP53 mutations in BRCA1 and BRCA2 mutation-negative French Canadian breast cancer families

About 40% of French Canadian breast and/or ovarian cancer families harbor germline BRCA1 or BRCA1 mutations where common mutations account for about 84% of all mutations identified in cancer families. Within a series of BRCA1 and BRCA2 mutation-negative families, a germline TP53 13398 G>A (Arg213Gln) mutation was identified, which was selected for mutation analysis in this gene because of a family history consistent with Li-Fraumeni syndrome (LFS). Given the founder effects in this population, the 13398 G>A mutation was screened in series of 52 BRCA1 and BRCA2 mutation-negative cancer families, and a mutation-positive family was identified. However, pedigree inspection and expansion of mutation-positive families with the same mutation revealed that they were closely related to each other. To further characterize the contribution of TP53 in cancer families, mutation analysis was performed in the remaining BRCA1 and BRCA2 mutation-negative cancer families. Thirty sequence variants were identified, the majority of which occur in intronic sequences and are not predicted to affect the functionality of TP53. However, the 14538 G>A (Arg290His) mutation was identified in a family which did not exhibit features consistent with LFS or Li-Fraumeni-like (LFL) syndrome. Neither of the TP53 mutations was detected in 381 French Canadian women with breast cancer diagnosed before 50 years of age not selected for family history of cancer. In all, germline TP53 mutations were identified in two of 52 (3.8%) cancer families, suggesting that TP53 is not a major contributor to BRCA1 and BRCA2 mutation-negative breast and/or ovarian cancer families of French Canadian descent.

Germline mutations of TP53 and BRCA2 genes in breast cancer/sarcoma families

The genetic aetiology of familial aggregations of breast cancer and sarcomas has been elucidated only in part. In this study, 23 unrelated individuals from families with one case of sarcoma and at least one case of breast cancer were screened for mutations in the TP53, BRCA1 and BRCA2 genes. Families were classified according to their conformity to the criteria defining the Li-Fraumeni syndrome (LFS), Li-Fraumeni-like (LFL) syndrome and hereditary breast/ovarian cancer (HBOC). Germline TP53 mutations were identified in three instances (13%), including one LFS and two LFL families, while none of the non-LFS/non-LFL families had a TP53 mutation. Three cases (13%), including one with a TP53 mutation, carried BRCA2 mutations. Of these, two were observed in LFL/HBOC families and the other one in a non-LFS/non-LFL/HBOC family, while none of the non-HBOC families tested positive. These findings suggest that the screening of BRCA2, in addition to TP53, may be appropriate for the molecular characterisation of breast cancer/sarcoma families, with practical implications for counselling and clinical management.

The TP53 mutation, R337H, is associated with Li-Fraumeni and Li-Fraumeni-like syndromes in Brazilian families

A TP53 germline mutation, R337H, has been previously described in children from southern Brazil with adrenocortical tumours but no documented familial history of other cancers. Here, we have screened for TP53 mutation 45 Brazilian unrelated individuals with family histories fulfilling the clinical definitions of Li-Fraumeni (LFS) or Li-Fraumeni-like (LFL) syndromes. Mutations were found in 13 patients (28.9%), including six (46.1%) R337H mutations, and four novel germline mutations (V173M, V197M, G244D and IVS6+1G>T). Families with the R337H mutation presented a wide spectrum of tumours, including breast cancers (30.4%), brain cancers (10.7%), soft tissue sarcomas (10.7%) and adrenocortical carcinomas (8.9%). Testing of 53 Brazilian subjects with no cancer history showed that R337H was not a common polymorphism in that population. Moreover, loss of heterozygocity with retention of the R337H allele was observed in a breast adenocarcinoma, supporting a role for this mutation in breast tumorigenesis. These results show that the TP53 R337H germline mutation predisposes to a larger spectrum of tumours, similar to the one reported for other TP53 mutations.

The TP53 mutational spectrum and frequency of CHEK2*1100delC in Li–Fraumeni-like kindreds

Li-Fraumeni syndrome (LFS) is a dominantly inherited cancer predisposition syndrome characterized by a wide spectrum of neoplasms occurring at young age. Germline mutations in the TP53 tumor suppressor gene have been identified in approximately 71 of LFS patients and 22 of Li-Fraumeni-like (LFL) patients. Mutations within the cell cycle checkpoint gene CHEK2 have also been reported in some patients with LFS, LFL, and phenotypically suggestive of LFS (PS-LFS) not carrying a TP53 mutation. In this study, we show that 7 of the 23 patients with LFS/LFL tested positive for deleterious mutations in p53. Fifteen of the remaining sixteen were not found to carry the CHEK2* 1100delCmutation. These results indicate that CHEK2*1100delC is not a common cause of LFS, LFL, or PS-LFS in North American kindreds not carrying a TP53 mutation. Of note, two patients were found to carry p53* R72P, which is of unknown clinical significance. Lack of segregation of this allele in one of these kindreds provides strong evidence that the R72P allele is not disease-causing. While mutations in p53 account for a proportion of patients with LFS/LFL, future studies are needed to determine if other genes are responsible for LFS/LFL families not carrying germline p53 mutations.

Germline TP53 mutations in women with very early onset breast cancer (BR)

1015 Background: Women with Li-Fraumeni syndrome (LFS) have a 49% risk of cancer by age 30, most of which is BR. In small series of women with early BR, prevalence of germline TP53 mutation is 1% (age <40) or 4% (age <30), most with personal or family history suggesting LFS. If true prevalence were higher, clinical testing for TP53 mutations might be useful, as carriers are advised to avoid nonessential radiation due to 2nd cancer risk. Among women tested in our cancer genetics program, age at BR diagnosis was 33 years in female members of 38 TP53 mutation kindreds versus 41 yrs (p<0.0001) in 186 women with BRCA1 and 45 yrs (p<0.0001) in 65 women with BRCA2 mutations. Methods: The prevalence of germline TP53 mutations among women diagnosed with BR age ≤33 years was assessed. DNA was extracted from 165 cell lines from a population-based series of women with BR age ≤33 years in Connecticut and from whole blood from 45 similar women from the Dana-Farber/Harvard Cancer Center SPORE bank. Family history data came from questionnaires and could not be confirmed under the protocols. None met strict criteria for LFS, but 9 had histories consistent with Li-Fraumeni-Like (LFL) syndrome (see Table). TP53 analysis utilized high through-put techniques. Results: 3 germline mutations were identified in the cohort [prevalence 1.4%, 95% CI 0.3 to 4.1]. Among probands 1 had a mother with BR at 40, 1 a mother with BR at 59 and maternal grandmother with colon >70; the third had no family cancer history. There were no mutations among the 9 women with LFL. BRCA1/2 analysis results on the cohort will be available for ASCO. Conclusion: Routine screening for germline TP53 mutations in women with BR at unusually young ages will have a low yield in otherwise unselected patients. These data are consistent with Lallo et al, Lancet 2003. No significant financial relationships to disclose.

TP53 and CHEK2 *1100delC gene mutation in North American families suggestive Li-Fraumeni syndrome: Memorial Sloan-Kettering experience

9537 Background: Li-Fraumeni syndrome (LFS) is a dominantly inherited cancer predisposition syndrome characterized by a wide spectrum of neoplasms including soft-tissue and bone sarcomas, brain tumors, adrenocortical tumors, breast cancers and leukemia occurring at young age. Germline mutations in the tumor suppressor gene TP53 have been identified in approximately 71% of LFS patients and 22% of Li-Fraumeni like (LFL) patients meeting Eeles's or Birch's criteria. Mutations within the checkpoint gene, CHEK2, encoding a kinase required for cell cycle regulation have also been reported in some patients with LFS/LFL not carrying TP53 mutation. Methods: We conducted a study to explore the possible association between a specific CHEK2*1100delC mutation and LFS/LFL. All patients who were evaluated for LFS/LFL at the Clinical Genetics Service at MSKCC from 1994–2003, who underwent testing for a TP53 mutation, and did not have a deleterious mutation identified were anonymously tested for CHEK2*1100delC. Testing for the CHEK2*1100delC mutation was done by DNA sequencing. Results: A total of 23 patients who underwent TP53 testing were identified. M:F ratio was 6:17. 13% of the patients met LFS criteria, 78% LFL and 9% patients did not meet these criteria. All patients tested had at least one primary malignancy (14 breast, 7 sarcoma, 5 hematological, 4 brain, 3 melanoma and 4 other). Median age at diagnosis of first tumor was 30. 57%, 30% and 9% of patients had a total of 2, 3 and 4 primary malignancies respectively. Overall, TP53 mutations were identified in 7 of 23 patients and variants of unknown clinical significance in 2 patients. TP53 germline mutations were identified in 2 of 3 LFS's and 4 of 18 LFL's patients. 15 of 16 patient who did not have a deleterious TP53 mutation were tested for CHEK2*1100delC. None of these TP53 negative patients were found to harbor CHEK2*1100delC. Conclusions: Our results do not support the causative role of the CHEK2*1100delC mutation in patients with LFS/LFL not carrying a TP53 mutation. No significant financial relationships to disclose.

Identification of a rare polymorphism in the human TP53 promoter

The majority of families with classic Li-Fraumeni Syndrome (LFS) and a significant proportion of Li-Fraumeni-like (LFL) families have a germline mutation in the TP53 tumor suppressor gene. However around 20% of LFS and 60% of LFL families have no identifiable genetic defect in the coding region or splice junctions of TP53, and the genetic basis for cancer susceptibility in these families remains largely uncharacterized. To determine whether promoter mutations could be responsible for the Li-Fraumeni phenotype, we sequenced the TP53 promoter in index cases from members of classic LFS and LFL families without detectable TP53 mutations. We identified an identical single nucleotide deletion within the C/EBP- like site of the promoter in two out of eighteen such families (11%), compared to only one of a total of 366 control samples (0.3%). Although this result is highly significant ( P=0.006, Fischer's exact test), the mutation did not affect the expression of TP53 in our hands. We provide evidence that this site is not utilized in the wild type TP53 promoter and further, that mutation of this site in LFS/LFL does not have a functional effect. We conclude that the sequence variant is a rare polymorphism arising within the TP53 promoter. However, the significantly increased frequency of this variant in LFS/LFL remains intriguing.

Analysis of Li–Fraumeni syndrome and Li–Fraumeni-like families for germline mutations in Bcl10

The Li–Fraumeni syndrome (LFS) is a dominant disease whose hallmark is an increased risk of breast cancers, brain tumours, sarcomas, leukaemia and adrenal carcinoma. Some, but not all LFS and Li–Fraumeni-like (LFL) families are caused by TP53 mutations. Bcl10 is a recently identified tumour suppressor reported to be commonly mutated in a wide range of cancers. To investigate the possibility that Bcl10 is a susceptibility gene for LFS and LFL we have analysed 27 LFS/LFL families. No mutations were observed. This indicates that Bcl10 is unlikely to act as a susceptibility gene for LFS and LFL.

A detailed study of loss of heterozygosity on chromosome 17 in tumours from Li – Fraumeni patients carrying a mutation to the TP53 gene

We have studied a total of 36 tumours from 28 patients with germline mutations to the TP53 gene for loss of heterozygosity at TP53 using techniques of both direct sequencing and restriction fragment length polymorphism analysis. All patients were from families conforming to the definition of classical Li-Fraumeni syndrome (LFS) or were Li-Fraumeni-like (LFL). The data we have obtained show that loss of the wild-type TP53 gene is observed in under half (44%) of all tumours, and that the pattern of LOH at TP53 may be mutation specific. LOH has been observed in premalignant as well as invasive tumours. Two tumours (6%) show loss of the mutant allele and retention of the wild-type. To confirm that TP53 is indeed the target for LOH events on chromosome 17, we have used additional microsatellite repeats to examine patterns of allelic imbalance along the length of chromosome 17. Data from this analysis indicate that TP53 is the target of loss, but reveal some other interesting patterns of allelic imbalance at other loci on chromosome 17.