The value of rapid functional assays of germline p53 status in LFS and LFL families

We have tested two rapid assays of p53 function, namely the apoptotic assay and the FASAY as means of detecting germline p53 mutations in members of Li-Fraumeni and Li-Fraumeni-like families. Results of the functional assays have been compared with direct sequencing of all 11 exons of the p53 gene. The results show good agreement between the two functional assays and between them and sequencing. No false-positives or negatives were seen with either functional assay although the apoptotic assay gave one borderline result for an individual without a mutation. As an initial screen the apoptotic assay is not only rapid but inexpensive and very simple to perform. It would be expected to detect any germline defect that leads to loss of p53 function. The apoptotic assay could be ideal as a means of prescreening large numbers of samples and identifying those that require further investigation. The FASAY detects mutations in exons 4-10, is rapid and distinguishes between functionally important and silent mutations.     

Sarcomas in TP53 germline mutation carriers: a review of the IARC TP53 database

BACKGROUND:

Sarcoma is the index diagnosis of Li‐Fraumeni syndrome (LFS), a familial predisposition to cancer that also includes brain cancer, breast cancer, and adrenal cortical carcinoma. Germline mutations in the TP53 gene are detected in approximately 80% of families that fulfill LFS criteria and in 15% to 25% of families that fulfill criteria for Li‐Fraumeni‐like syndrome (LFS), a group of related syndromes with broader clinical criteria.

METHODS:

The authors of this report used the International Agency for Research on Cancer TP53 database to analyze the types, age at onset and mutation patterns of sarcoma in TP53 mutation carriers. Those data were compared with sarcoma types in the general population of Caucasians using data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program.

RESULTS:

Overall, sarcomas represented 25% of tumors in TP53 mutation carriers, and 95.6% occurred before age 50 years compared with 38.3% before age 50 years in the SEER data set. Sarcomas were more likely to be rhabdomyosarcoma in carriers aged <5 years (odds ratio [OR], 11.6; 95% confidence interval [CI], 6.1‐21.9) and osteosarcoma in carriers at any age (aged <20 years: OR, 1.41; 95% CI, 1.02‐1.94; age >20 years: OR, 4.61; 95% CI, 2.72‐7.83). Early sarcoma (at age <20 years) was associated with missense mutations in exons encoding the DNA‐binding domain of p53 protein. Conversely, p53 null mutations (frameshift, splice sites, nonsense) and mutations outside the DNA‐binding domain were associated with leiomyosarcoma (OR, 10.1; 95% CI, 3.4‐29.9), a type of sarcoma that occurred after age 20 years.

CONCLUSIONS:

The current results further demonstrated genotype‐phenotype correlations and age‐dependent variations in sarcoma types in carriers of germline TP53 mutations. Cancer 2012;. © 2011 American Cancer Society.     

Investigations on a clinically and functionally unusual and novel germline p53 mutation

This report describes an individual with a rare choroid plexus papilloma in adulthood (age 29) after earlier having an osteosarcoma (age 22). The results from this study, and others, suggest that it may be advisable to consider the possibility of a germline p53 mutation in adults presenting with choroid plexus tumours. In the current study automated DNA sequencing of genomic DNA detected a novel germline 7 base pair insertion in exon 5 of the p53 gene in this patient. The alteration in frame would produce amino acid substitutions beginning with alanine to glycine at position 161 and a stop codon at position 182 in the mutated protein. Surprisingly two assays of p53 function gave apparently wild-type results on peripheral blood lymphocytes from this individual. These results led us to carry out more detailed functional tests on the mutant protein. The mutant allele was expressed either at very low levels or not at all in phytohaemagglutinin stimulated lymphocytes. Further, the mutant protein was completely non-functional in terms of its ability to transactivate a series of p53-responsive genes (p21(WAF1), bax, PIG3), to transrepress a target gene and to inhibit colony growth in transfected Saos-2 cells. However, surprisingly, data from irradiated peripheral blood lymphocytes and transfected Saos-2 cells, suggested that this truncated, mutant protein retains significant ability to induce apoptosis.     

Disruption of tp53 leads to cutaneous nevus and melanoma formation in Xenopus tropicalis

In humans, germline TP53 mutations predispose carriers to a wide spectrum of cancers, which is known as Li–Fraumeni syndrome (LFS). To date, the association of melanomas with LFS remains unestablished. No melanomas have been reported in any P53‐modified mouse models either. In this study, we show that targeted disruption of P53 at the DNA‐binding domain in Xenopus tropicalis recapitulates LFS, with the formation of soft‐tissue sarcomas and pancreatic ductal adenocarcinoma. Interestingly, 19% of the 14‐month‐old tp53 ^Δ7/Δ7 homozygotes and 18% of tp53 ^+/Δ7 heterozygotes spontaneously developed small nevi and non‐invasive melanomas. Large invasive melanomas were also observed in other older homozygous mutants, with about 7.9% penetrance. Our data suggest that more dermatologic investigation of LFS patients should be able to settle the association of melanoma with LFS in epidemiology. Our model is also valuable for further investigation of the molecular mechanism underlying melanoma progression upon germline alteration of the tp53 locus.     

Early onset HER2-positive breast cancer is associated with germline TP53 mutations

BACKGROUND:

Germline TP53 mutations predispose to early onset breast cancer in women and are associated with Li‐Fraumeni syndrome. Published data on the pathological characteristics of breast cancer among women with TP53 mutations is limited.

METHODS:

We retrospectively reviewed the clinical records of women who underwent genetic testing for suspected germline TP53 mutations and who were diagnosed with breast cancer between 2000 and 2011. The pathological characteristics of the breast tumors from patients testing positive for a mutation (cases) were compared with those testing negative (controls).

RESULTS:

Patients who tested positive for germlineTP53 mutations (n = 30) were compared with controls (n = 79). Human epidermal growth factor receptor 2 (HER2) amplification and/or overexpression was found in 67% of the tumors from the cases, compared with 25% for the controls (P = .0001). Among patients with a mutation, 70% had estrogen receptor‐ and/or progesterone receptor‐positive tumors, compared with 68% in the control group (P = .87). After adjusting for age at breast cancer diagnosis, having a HER2‐positive tumor increased the odds of testing positive for a germline TP53 mutation (odds ratio, 6.9; 95% confidence interval, 2.6‐18.2). For each yearly increment in age at breast cancer diagnosis, there was decreased likelihood of having a TP53 mutation of 5% (odds ratio, 0.95; 95% confidence interval0.91‐0.99).

CONCLUSIONS:

This study suggests an association between germline TP53 mutations and early onset HER2‐positive breast cancer. If confirmed in a larger cohort, these results could guide genetic testing strategies, lead to chemoprevention trials incorporating HER2‐targeted therapies, and elucidate some of the molecular pathways involved in breast cancer. Cancer 2012;. © 2011 American Cancer Society.     

Identification and characterization of a novel germline p53 mutation in a patient with glioblastoma and colon cancer

Germline mutations in the p53 tumor suppressor gene have been identified in patients with Li‐Fraumeni syndrome (LFS) and patients with Li‐Fraumeni‐like syndrome (LFL). However, to date, germline p53 mutations in patients not fulfilling the criteria of LFS or LFL have been reported only very rarely. In our study, a novel germline c.584T>C (p.Ile195Thr) mutation of the p53 gene was found in a 21–year‐old male with a glioblastoma and colon cancer. He had no family history of cancer within second‐degree relatives, and loss of the wild‐type p53 allele and overexpression of p53 protein were observed in both tumors. Functional analyses revealed transactivation and growth suppressive function activities of the Thr195‐type p53 to be impaired. These results suggest germline p53 mutations to possibly be responsible for a subset of young adult patient with multiple malignant tumors, even those not meeting the clinical criteria for LFS or LFL. © 2009 UICC     

TP53 mutation and survival in aggressive B cell lymphoma

TP53 is mutated in 20–25% of aggressive B‐cell lymphoma (B‐NHL). To date, no studies have addressed the impact of TP53 mutations in prospective clinical trial cohorts. To evaluate the impact of TP53 mutation to current risk models in aggressive B‐NHL, we investigated TP53 gene mutations within the RICOVER‐60 trial. Of 1,222 elderly patients (aged 61–80 years) enrolled in the study and randomized to six or eight cycles of CHOP‐14 with or without Rituximab (NCT00052936), 265 patients were analyzed for TP53 mutations. TP53 mutations were demonstrated in 63 of 265 patients (23.8%). TP53 mutation was associated with higher LDH (65% vs. 37%; p < 0.001), higher international prognostic index‐Scores (IPI 4/5 27% vs. 12%; p = 0.025) and B‐symptoms (41% vs. 24%; p = 0.011). Patients with TP53 mutation were less likely to obtain a complete remission CR/CRu (CR unconfirmed) 61.9% (mut) vs. 79.7% (wt) (p = 0.007). TP53 mutations were associated with decreased event‐free (EFS), progression‐free (PFS) and overall survival (OS) (median observation time of 40.2 months): the 3 year EFS, PFS and OS were 42% (vs. 60%; p = 0.012), 42% (vs. 67.5%; p < 0.001) and 50% (vs. 76%; p < 0.001) for the TP53 mutation group. In a Cox proportional hazard analysis adjusting for IPI‐factors and treatment arms, TP53 mutation was shown to be an independent predictor of EFS (HR 1.5), PFS (HR 2.0) and OS (HR 2.3; p < 0.001). TP53 mutations are independent predictors of survival in untreated patients with aggressive CD20+ lymphoma. TP53 mutations should be considered for risk models in DLBCL and strategies to improve outcome for patients with mutant TP53 must be developed.     

Telomere length in peripheral blood cells of germline TP53 mutation carriers is shorter than that of normal individuals of corresponding age

BACKGROUND: A decrease in the age at cancer onset and increase in cancer incidence in successive generations in Li-Fraumeni syndrome (LFS) families with germline TP53 mutations have been previously described. In the current study a possible relation was analyzed between telomere length and cancer onset in TP53 mutation carriers. METHODS: Telomere length was measured using real-time quantitative polymerase chain reaction (PCR) in 20 carriers of germline TP53 mutations and in 83 unrelated healthy individuals. According to the age at blood sampling, patients and controls were divided into 2 age groups, children and adults. Telomere length was correlated to TP53 mutation status and telomere shortening in patients to the age at cancer onset. A t-test and linear regression were used to analyze the data. RESULTS: Compared with healthy controls, telomere length was significantly shorter both in the child (P = .001) and adult (P = .034) germline T53 mutation carriers. Although a statistically significant correlation between telomere shortening and the age at cancer onset was not observed, there was a trend of shorter telomeres in mutation carriers affected in childhood compared with those affected later in life. Neither cancer therapy nor sex differences were likely to affect the results. CONCLUSIONS: The findings suggest a possible link between the carriership of a germline TP53 mutation, telomere length, predisposition to early-onset cancer, and anticipation in LFS.     

Unique volatolomic signatures of TP53 and KRAS in lung cells

Background:

Volatile organic compounds (VOCs) are potential biomarkers for cancer detection in breath, but it is unclear if they reflect specific mutations. To test this, we have compared human bronchial epithelial cell (HBEC) cell lines carrying the KRAS^V12 mutation, knockdown of TP53 or both with parental HBEC cells.

Methods:

VOC from headspace above cultured cells were collected by passive sampling and analysed by thermal desorption gas chromatography mass spectrometry (TD-GC–MS) or sensor array with discriminant factor analysis (DFA).

Results:

In TD-GC–MS analysis, individual compounds had limited ability to discriminate between cell lines, but by applying DFA analysis combinations of 20 VOCs successfully discriminated between all cell types (accuracies 80–100%, with leave-one-out cross validation). Sensor array detection DFA demonstrated the ability to discriminate samples based on their cell type for all comparisons with accuracies varying between 77% and 93%.

Conclusions:

Our results demonstrate that minimal genetic changes in bronchial airway cells lead to detectable differences in levels of specific VOCs identified by TD-GC–MS or of patterns of VOCs identified by sensor array output. From the clinical aspect, these results suggest the possibility of breath analysis for detection of minimal genetic changes for earlier diagnosis or for genetic typing of lung cancers.     

Detection of R337H, a germline TP53 mutation predisposing to multiple cancers, in asymptomatic women participating in a breast cancer screening program in Southern Brazil

Germline TP53 mutations predispose to a rare familial cancer syndrome, the Li-Fraumeni Syndrome (LFS), characterized by the early onset of multiple cancers including childhood adrenocortical carcinomas, sarcomas and brain tumors, and breast and colon cancer in young adults. An identical germline mutation at codon 337 in TP53 (R337H) has been shown to be causally related to an increased risk of multiple cancers in unrelated subjects with familial cancer risk in Southern Brazil. Here we have assessed the prevalence of R337H in 750 healthy women participating in a community-based breast cancer screening program in the area of Porto Alegre. The mutant was detected in two participants (0.3%) who were fourth-degree relatives and reported a familial history of cancer at multiple sites that did not match classical criteria for LFS and its variants. Testing in additional family members detected the mutation in three subjects, one of whom developed breast cancer at the age of 36. These findings indicate that R337H may be a low penetrance mutant which predisposes to multiple cancers and occurs in the population of Southern Brazil at a frequency 10-20 times higher than other TP53 mutants commonly associated with LFS.     

p53 Arg72Pro polymorphism,adiposity status,and cancer risk: Two case‐cohorts within a Japanese prospective study

The tumor suppressor protein, p53, is a critical molecule involved in cancer development. However, the association between p53 Arg72Pro polymorphism and cancer risk remains unclear, possibly due to the pro‐tumor potential of p53 under metabolic stress. Here, we hypothesized that the p53 Arg72Pro polymorphism plays different roles during tumorigenesis by adiposity status. We measured baseline body mass index (BMI) and p53 Arg72Pro polymorphism for two case‐cohorts, which included 4264 cancers with up to 20 years of follow‐up. Multivariable‐adjusted hazard ratios (HRs) and confidence intervals (CIs) were estimated using weighted Cox proportional‐hazards method. Without consideration of adiposity status, p53 Arg72Pro polymorphism was not associated with cancer risk. However, proline (Pro) homozygous genotype conferred an increased cancer risk for individuals with a BMI <25 kg/m² (HR [95% CI]: 1.12 [1.00–1.26] for total cancer and 1.19 [1.02–1.38] for obesity‐related cancer), but not for those with a BMI ≥ 25 kg/m². The heterogeneous effect of p53 Arg72Pro polymorphism on cancer risk according to adiposity status was indicated (p _{heterogeneity}: 0.07 for total cancer and 0.03 for obesity‐related cancer). Furthermore, the association between overweight and cancer risk was only observed in arginine (Arg) carriers, but not in Pro homozygous carriers (p _{heterogeneity}: 0.07 for total cancer and 0.02 for obesity‐related cancer). Pro homozygous carriers were more likely to be predisposed to cancer than Arg carriers with normal‐weight conditions. In addition, overweight was related to a higher cancer risk in Arg carriers than Pro homozygous carriers. Our findings may suggest the adiposity‐dependent dual effects of p53 Arg72Pro polymorphism during tumorigenesis.     

A Japanese patient with Li-Fraumeni syndrome who had nine primary malignancies associated with a germline mutation of the p53 tumor-suppressor gene

We describe a patient who had nine primary malignant tumors and a germline mutation in the p53 tumor-suppressor gene, characteristically found in the Li-Fraumeni syndrome (LFS). A 15-year-old girl with no family history of cancer was referred to our hospital because of pain and swelling of the right knee. Osteosarcoma was diagnosed. The patient received chemotherapy followed by surgery and had a remission. After the age of 28 years, nine primary malignant tumors developed successively, including right breast cancer, colon cancer, malignant fibrous histiocytoma (MFH) of the abdominal wall, right lung double cancers, bilateral breast cancers, and MFH of the left thigh. This is the second highest number of types of primary malignant tumors to be reported in LFS. All tumors were treated by a multidisciplinary approach, including surgery. Genetic analysis revealed a germline missense mutation in the p53 gene (c.659 A > G), resulting in Y220C, which has been reported in three families with LFS. The patient died of lung metastasis from MFH at the age of 37 years. Despite the multiple tumors, repeated induction of remissions resulted in long survival. Our findings suggest that a multidisciplinary approach to treatment, including surgery, is beneficial in patients with LFS.     

Rapid development of post-radiotherapy sarcoma and breast cancer in a patient with a novel germline 'de-novo' TP53 mutation

AimsGermline mutations in the TP53 tumour suppressor gene are associated with Li–Fraumeni syndrome, which is characterised by a spectrum of neoplasms occurring in children and young adults that predominantly include early-onset breast cancer, a variety of sarcomas, brain tumours and adrenocortical tumours. The identification of patients carrying TP53 mutations is primarily based on a positive family history of these early-onset characteristic cancer types. The aim of this study is to emphasize the importance of TP53 molecular testing in patients with very early onset breast cancer and no family history of cancer.Materials and methodsA young woman with no family history of cancer presented with bilateral breast cancer at the age of 27 years. Forty months later she developed malignant fibrous histiocytoma of the right clavicle and another primary left breast cancer. Molecular testing of mutations 185delAG, 5382insC in BRCA1 gene and 6174delT in BRCA2 gene was performed using multiplex PCR and separation on a denaturing polyacrylamide gel. TP53 molecular analysis was performed by PCR-SSCP analysis of the whole coding region of the TP53. Exon 8 PCR products were sequenced using an ABI dye terminator kit and examined on an ABI 3100 automated sequencer.ResultsMolecular testing of peripheral blood DNA did not reveal mutations in BRCA1 or BRCA2 genes. A novel germline TP53 mutation, c.G841C, p.D281N, was identified. The detected mutation is a missense substitution, c.G841C, resulting in the substitution of the amino acid aspartate to asparagine, p.D281N. Molecular analysis in her parents showed that neither of them carried the mutation.ConclusionsWe describe a novel ‘de novo’ TP53 mutation and discuss the importance of molecular testing in early-onset breast cancer patients and its effect on the management and outcome of the disease.     

Genetic variants in germline TP53 and MDM2 SNP309 are not associated with early onset colorectal cancer

BACKGROUND AND OBJECTIVES: Colorectal cancer (CRC) arising in patients under age 30 is a rare disease, and few cases have been reported within Li-Fraumeni kindreds. To determine how often alterations in the p53 pathway genes contribute to disease susceptibility, we have evaluated patients with early onset CRC for the presence of germline variants in the p53 gene and MDM2 SNP309. METHODS: Thirty-five patients with CRC diagnosed before age 30 were included in this study-based on tissue availability. DNA samples from peripheral blood leukocytes were analyzed for constitutional mutations and polymorphisms in p53 as well as polymorphisms in MDM2 SNP309. RESULTS: No mutations were found in exons 4-10 of the p53 gene. The frequencies of polymorphisms in p53 and in MDM2 SNP309 did not differ from rates previously reported for normal control populations, and no polymorphism in either gene could be associated with early onset CRC. CONCLUSIONS: Neither germline variants in p53 nor MDM2 SNP309 play an underlying role in the development of very early onset CRC. For the large majority of cases, the genetic basis of this disease remains unknown.     

The relationship between radiation-induced G(1)arrest and chromosome aberrations in Li-Fraumeni fibroblasts with or without germline TP53 mutations.

We previously showed that cultured fibroblasts from patients with the cancer-prone Li-Fraumeni (LF) syndrome, having heterozygous germline TP53 mutations, sustain less ionizing radiation-induced permanent G(1)arrest than normal fibroblasts. In contrast, fibroblast strains from LF patients without TP53 mutations showed normal G(1)arrest. We have now investigated the relationship between the extent of G(1)arrest and the level of structural chromosome damage (mainly dicentrics, rings and acentric fragments) in cells at their first mitosis after G(1)irradiation, in 9 LF strains with TP53 mutations, 6 without TP53 mutations and 7 normal strains. Average levels of damage in the mutant strains were 50% higher than in normals, whereas in non-mutant LF strains they were 100% higher. DNA double strand breaks (dsb) are known to act as a signal for p53-dependent G(1)arrest and to be the lesions from which chromosome aberrations arise. These results suggest that a minimal level of dsb is required before the signal for arrest is activated and that p53-defective cells have a higher signal threshold than p53-proficient cells. Dsb that do not cause G(1)blockage can progress to mitosis and appear as simple deletions or interact to form exchange aberrations. The elevated levels in the non-mutant strains may arise from defects in the extent or accuracy of dsb repair. In LF cells with or without TP53 mutations, the reduced capacity to eliminate or repair chromosomal damage of the type induced by ionising radiation, may contribute to cancer predisposition in this syndrome.