bims-lifras Biomed News
on Li-Fraumeni syndrome
Issue of 2021–01–24
fourteen papers selected by
Joanna Zawacka-Pankau, University of Warsaw
  1. Prevalence of mutations in BRCA and MMR genes in patients affected with hereditary endometrial cancer.
  2. A rare large duplication of MLH1 identified in Lynch syndrome.
  3. Novel PHOX2B germline mutation in childhood medulloblastoma: a case report.
  4. The importance of Li-Fraumeni syndrome, a hereditary cancer predisposition disorder.
  5. Homologous recombination deficiency (HRD) score in germline BRCA2- versus ATM-altered prostate cancer.
  6. Germline EGFR variants are over-represented in adolescents and young adults (AYA) with adrenocortical carcinoma.
  7. Spectrum of germline mutations in RB1 in Chinese patients with retinoblastoma: Application of targeted next-generation sequencing.
  8. British Gynaecological Cancer Society/British Association of Gynaecological Pathology consensus for germline and tumor testing for BRCA1/2 variants in ovarian cancer in the United Kingdom.
  9. Interpretation of BRCA2 Splicing Variants: A Case Series of Challenging Variant Interpretations and the Importance of Functional RNA Analysis.
  10. Recontacting non-BRCA1/2 breast cancer patients for germline CHEK2 c.1100del pathogenic variant testing: uptake and patient experiences.
  11. Long-term risk of subsequent cancer incidence among hereditary and nonhereditary retinoblastoma survivors.
  12. ATM germline variants and male breast cancer.
  13. A Case Report of Germline Compound Heterozygous Mutations in the BRCA1 Gene of an Ovarian and Breast Cancer Patient.
  14. Ubiquitin Ligase Activities of WWP1 Germline Variants K740N and N745S.
  1. Med Oncol. 2021 Jan 23. 38(2): 13
    Prevalence of mutations in BRCA and MMR genes in patients affected with hereditary endometrial cancer.
    Maria Teresa Vietri, Giovanna D'Elia, Gemma Caliendo, Amelia Casamassimi, Alessandro Federico, Luana Passariello, Michele Cioffi, Anna Maria Molinari.
      Endometrial cancer (EC) is the fifth most common cancer in women from developed countries, accounting for 4.8% of new cases and 2.1% of deaths. The genetic basis for the familial risk of endometrial cancer has not been completely defined. Mostly, hereditary EC is part of two syndromes as Lynch syndrome (LS) and Hereditary Breast and Ovarian Cancer syndrome (HBOC). LS is the prototypical hereditary cancer syndrome in EC and accounts for 2-6% of all endometrial cancers. This disease is caused by autosomal dominant mutations in DNA mismatch repair (MMR) genes. Patients carrying a germline mutation in one of the MMR genes have a cumulative lifetime risk to develop EC of 20-70%. HBOC is an autosomal dominantly inherited disease, which mostly predisposes to breast and ovarian cancers, but it can be also associated with other malignancies. HBOC results from germline mutations in BRCA1/2 genes. The aim of this study was to determine the mutational status of a cohort of 40 EC patients, 19 belonging to families with LS and 21 to HBOC. Mutation analysis of MLH1, MSH2, BRCA1 and BRCA2 genes showed pathogenic variants in 17/40 (42.5%) patients. Out of 19 patients belonging to LS families, 8 (42.1%) showed a pathogenic variant. Out of 21 patients belonging to HBOC families, 9 (42.8%) showed a pathogenic variant. 1/21 (4.8%) patient report 1 variant of unknown significance (UV), c.599 C > T (p.T200I), in BRCA2. Moreover, in 1/21 (4.8%) patient we identified a novel missense variant in BRCA2, c.9541A > T (p.Met3181Leu). Mutational analysis was extended to family members, both healthy and cancer affected, of mutated patients; all the tested relatives affected with cancer displayed the pathogenic variant. Our data suggest that patients with hereditary EC have a high percentage of mutations in the LS and HBOC main susceptibility genes; therefore, the surveillance for EC, already indicated in LS patients, should also be recommended for patients with HBOC.
    Keywords:  BRCA genes; Endometrial cancer; Hereditary breast and ovarian cancer syndrome; Lynch syndrome; MMR genes
    DOI:  https://doi.org/10.1007/s12032-021-01454-5
  2. Hered Cancer Clin Pract. 2021 Jan 19. 19(1): 10
    A rare large duplication of MLH1 identified in Lynch syndrome.
    Abhishek Kumar, Nagarajan Paramasivam, Obul Reddy Bandapalli, Matthias Schlesner, Tianhui Chen, Rolf Sijmons, Dagmara Dymerska, Katarzyna Golebiewska, Magdalena Kuswik, Jan Lubinski, Kari Hemminki, Asta Försti.
       BACKGROUND: The most frequently identified strong cancer predisposition mutations for colorectal cancer (CRC) are those in the mismatch repair (MMR) genes in Lynch syndrome. Laboratory diagnostics include testing tumors for immunohistochemical staining (IHC) of the Lynch syndrome-associated DNA MMR proteins and/or for microsatellite instability (MSI) followed by sequencing or other techniques, such as denaturing high performance liquid chromatography (DHPLC), to identify the mutation.
    METHODS: In an ongoing project focusing on finding Mendelian cancer syndromes we applied whole-exome/whole-genome sequencing (WES/WGS) to 19 CRC families.
    RESULTS: Three families were identified with a pathogenic/likely pathogenic germline variant in a MMR gene that had previously tested negative in DHPLC gene variant screening. All families had a history of CRC in several family members across multiple generations. Tumor analysis showed loss of the MMR protein IHC staining corresponding to the mutated genes, as well as MSI. In family A, a structural variant, a duplication of exons 4 to 13, was identified in MLH1. The duplication was predicted to lead to a frameshift at amino acid 520 and a premature stop codon at amino acid 539. In family B, a 1 base pair deletion was found in MLH1, resulting in a frameshift and a stop codon at amino acid 491. In family C, we identified a splice site variant in MSH2, which was predicted to lead loss of a splice donor site.
    CONCLUSIONS: We identified altogether three pathogenic/likely pathogenic variants in the MMR genes in three of the 19 sequenced families. The MLH1 variants, a duplication of exons 4 to 13 and a frameshift variant, were novel, based on the InSiGHT and ClinVar databases; the MSH2 splice site variant was reported by a single submitter in ClinVar. As a variant class, duplications have rarely been reported in the MMR gene literature, particularly those covering several exons.
    Keywords:  Genetic predisposition; Lynch syndrome; Mismatch repair genes; Whole-genome sequencing
    DOI:  https://doi.org/10.1186/s13053-021-00167-0
  3. Hered Cancer Clin Pract. 2021 Jan 19. 19(1): 12
    Novel PHOX2B germline mutation in childhood medulloblastoma: a case report.
    Caiping Ke, Xiaoshun Shi, Allen Menglin Chen, Chaoming Li, Bifeng Jiang, Kailing Huang, Zhouxia Zheng, Yanhui Liu, Zhuona Chen, Yingjun Luo, Huaming Lin, Jiexia Zhang.
       BACKGROUND: Medulloblastoma is an aggressive brain tumor mostly found in children, few studies on pathogenic germline mutations predisposing this disease was reported.
    CASE PRESENTATION: We present an 11-year-old male with medulloblastoma, who harbors a de novo PHOX2B germline mutation as detected by whole exome sequencing (WES). Family history was negative. Sanger sequencing confirmed this mutation in peripheral blood, hair bulbs, urine and saliva. Identification of novel germline mutations is beneficial for childhood cancer screening.
    CONCLUSIONS: This case revealed a de novo PHOX2B germline mutation as a potential cause of medulloblastoma in a child and suggests familial germline variant screening is useful when an affected family is considering having a second child.
    Keywords:  Cancer screening; Germline mutation; Medulloblastoma; PHOX2B; Whole exome sequencing
    DOI:  https://doi.org/10.1186/s13053-021-00170-5
  4. Arch Argent Pediatr. 2021 Feb;119(1): e11-e17
    The importance of Li-Fraumeni syndrome, a hereditary cancer predisposition disorder.
    Belén Miranda Alcalde, Marta Villa Alcázar, Isabel Martínez Romera, Blanca López Ibor.
      Pediatric cancer is rare. It is estimated that more than 10-15 % of tumors are secondary to a pathogenic variant in a cancer predisposition gene. More than 100 cancer predisposition genes and their association with syndromes or isolated tumors have been identified. Li-Fraumeni syndrome is one of those who have been most widely described. Patients with this syndrome present a high risk of developing one or more tumors. Its knowledge allows to establish a follow-up protocol for the patient and affected family members, so as to detect new tumors in an early manner and reduce tumorand treatment-related morbidity and mortality. The objective of this review is to offer useful guidelines for pediatricians. Based on a family case, reasons for Li-Fraumeni syndrome suspicion, clinical and genetic diagnosis, and the follow-up protocol of family members who carry the same mutation will be reviewed.
    Keywords:  Li-Fraumeni syndrome; TP53 gene; hereditary neoplastic syndromes; neoplasms; pediatrics
    DOI:  https://doi.org/10.5546/aap.2021.eng.e11
  5. Mod Pathol. 2021 Jan 18.
    Homologous recombination deficiency (HRD) score in germline BRCA2- versus ATM-altered prostate cancer.
    Tamara L Lotan, Harsimar B Kaur, Daniela C Salles, Sanjana Murali, Edward M Schaeffer, Jerry S Lanchbury, William B Isaacs, Robert Brown, Andrea L Richardson, Olivier Cussenot, Geraldine Cancel-Tassin, Kirsten M Timms, Emmanuel S Antonarakis.
      The homologous recombination deficiency (HRD) score integrates three DNA-based measures of genomic instability, and has been understudied in prostate cancer. Given the recent FDA approval of two PARP inhibitors for prostate cancer, HRD score analysis could help to refine treatment selection. We assessed HRD score (defined as the sum of loss-of-heterozygosity, telomeric allelic imbalance, and large-scale state transitions) in three cohorts of primary prostate cancer, including a Johns Hopkins University (JHU) cohort with germline mutations in BRCA2, ATM, or CHEK2 (n = 64), the TCGA cohort (n = 391), and the PROGENE cohort (n = 102). In the JHU cohort, tumors with germline BRCA2 mutations had higher HRD scores (median = 27) than those with germline ATM or CHEK2 mutations (median = 16.5 [p = 0.029] and 9 [p < 0.001], respectively). For TCGA tumors without underlying HR pathway mutations, the median HRD score was 11, significantly lower than ovarian carcinoma lacking BRCA1/2 mutations (median = 28). In the absence of HR gene mutations, the median HRD score was unexpectedly higher among prostate cancers with TP53 mutations versus those without (17 vs. 11; p = 0.015); this finding was confirmed in the PROGENE cohort (24 vs. 16; p = 0.001). Finally, among eight BRCA2-altered patients who received olaparib, progression-free survival trended longer in those with HRD scores above versus below the median (14.9 vs. 9.9 months). We conclude that HRD scores are low in primary prostate cancer and higher in cases with germline BRCA2 or somatic TP53 mutations. Germline BRCA2-altered cases have significantly higher HRD scores than germline ATM-altered or CHEK2-altered cases, consistent with the lower efficacy of PARP inhibitors among the latter.
    DOI:  https://doi.org/10.1038/s41379-020-00731-4
  6. Hum Mol Genet. 2021 Jan 21. 29(22): 3679-3690
    Germline EGFR variants are over-represented in adolescents and young adults (AYA) with adrenocortical carcinoma.
    Sara Akhavanfard, Lamis Yehia, Roshan Padmanabhan, Jordan P Reynolds, Ying Ni, Charis Eng.
      Adrenocortical Carcinoma (ACC) is a rare endocrine tumor with poor overall prognosis and 1.5-fold overrepresentation in females. In children, ACC is associated with inherited cancer syndromes with 50-80% of childhood-ACC associated with TP53 germline variants. ACC in adolescents and young adults (AYA) is rarely due to germline TP53, IGF2, PRKAR1A and MEN1 variants. We analyzed exome sequencing data from 21 children (<15y), 32 AYA (15-39y), and 60 adults (>39y) with ACC, and retained all pathogenic, likely pathogenic, and highly prioritized variants of uncertain significance. We engineered a stable lentiviral-mutant ACC cell line, harboring an EGFR variant (p.Asp1080Asn) from a 21-year-old female without germline-TP53-variant and with aggressive ACC. We found that 4.8% of the children (P = 0.004) and 6.2% of AYA (P < 0.0001), all-female participants, harbored germline EGFR variants, compared to only 0.3% of the control group. Expanding our analysis to the RTK-RAS-MAPK pathway, we found that the RTK genes have the highest number of highly prioritized germline variants in these individuals amongst all three arms of this pathway. We showed EGFR mutant cells migrate faster and are characterized by a stem-like phenotype compared to wild type cells. While EGFR inhibitors did not affect the stemness of mutant cells, Sunitinib, a multireceptor tyrosine kinase inhibitor, significantly reduced their stem-like behavior. Our data suggest that EGFR could be a novel underlying germline predisposition factor for ACC, especially in the Childhood-AYA (C-AYA) population. Further clinical validation can improve precision oncology management of this disease, which is known to have limited therapeutic options.
    DOI:  https://doi.org/10.1093/hmg/ddaa268
  7. Mol Vis. 2021 ;27 1-16
    Spectrum of germline mutations in RB1 in Chinese patients with retinoblastoma: Application of targeted next-generation sequencing.
    Yihua Zou, Jiakai Li, Peiyan Hua, Tingyi Liang, Xunda Ji, Peiquan Zhao.
       Purpose: Retinoblastoma (RB) is a pediatric ocular malignancy due to biallelic inactivation of the RB1 gene. Genetic testing is critically important for treatment decisions for this disease. Targeted next-generation sequencing (NGS) has been demonstrated to be an effective strategy for discovering all types of mutations in the RB1 gene. The aim of this study is the application of targeted NGS in a cohort of Chinese patients with retinoblastoma to identify germline mutations in the RB1 gene.
    Methods: Blood samples were collected from 149 unrelated probands with retinoblastoma (62 bilaterally and 87 unilaterally) and their parent(s). Genomic DNA was analyzed with custom panel-based targeted NGS, and the panel was designed to include exons 1-27 of the RB1 gene with flanking intronic sequences. Single nucleotide variations (SNVs) and small insertions/deletions (InDels) identified were confirmed with Sanger sequencing. If the Sanger sequencing of a low-frequency variant (LFV) detected with targeted NGS was negative, PCR-based deep NGS was conducted for added confirmation. Copy number variations (CNVs) detected with targeted NGS were confirmed with multiplex ligation-dependent probe amplification (MLPA).
    Results: Overall, 74 germline mutations were detected in 48.3% of the probands (72/149, 56 bilateral and 16 unilateral cases). The total detection rate in the bilateral cases was 90.3% (56/62). These mutations included 64 SNVs and InDels (25 nonsense, 20 splicing, ten frameshift, eight missense, and one synonymous variants) and ten CNVs. All CNVs were confirmed with MLPA. Twenty-four (32.4%, 24/74) variants detected were novel, including nine splicing, six frameshift, five missense, and four nonsense variants. Eight LFVs (10.8%, 8/74) were found with targeted NGS; six of which were identified with Sanger sequencing, and two were identified with PCR-based deep NGS (13.16% and 3.000% mutant rates, respectively).
    Conclusions: This study expanded the spectrum of germline mutations in RB1 using targeted NGS technology, which is a cost-saving and efficient method for genetic sequencing of retinoblastoma and may improve the molecular diagnosis of retinoblastoma.
  8. Int J Gynecol Cancer. 2021 Jan 19. pii: ijgc-2020-002112. [Epub ahead of print]
    British Gynaecological Cancer Society/British Association of Gynaecological Pathology consensus for germline and tumor testing for BRCA1/2 variants in ovarian cancer in the United Kingdom.
    Sudha Sundar, Ranjit Manchanda, Charlie Gourley, Angela George, Andrew Wallace, Janos Balega, Sarah Williams, Yvonne Wallis, Richard Edmondson, Shibani Nicum, Jonathan Frost, Ayoma Attygalle, Christina Fotopoulou, Rebecca Bowen, Dani Bell, Ketankumar Gajjar, Bruce Ramsay, Nicholas J Wood, Sadaf Ghaem-Maghami, Tracie Miles, Raji Ganesan.
      The British Gynecological Cancer Society and the British Association of Gynecological Pathologists established a multidisciplinary consensus group comprising experts in surgical gynecological oncology, medical oncology, genetics, and laboratory science, and clinical nurse specialists to identify the optimal pathways to BRCA germline and tumor testing in patients with ovarian cancer in routine clinical practice. In particular, the group explored models of consent, quality standards identified at pathology laboratories, and experience and data from pioneering cancer centers. The group liaised with representatives from ovarian cancer charities to also identify patient perspectives that would be important to implementation. Recommendations from these consensus group deliberations are presented in this manuscript.
    Keywords:  BRCA1 protein; BRCA2 protein; fallopian tube neoplasms; ovarian neoplasms
    DOI:  https://doi.org/10.1136/ijgc-2020-002112
  9. Fam Cancer. 2021 Jan 20.
    Interpretation of BRCA2 Splicing Variants: A Case Series of Challenging Variant Interpretations and the Importance of Functional RNA Analysis.
    Paola Nix, Erin Mundt, Bradford Coffee, Elizabeth Goossen, Bryan M Warf, Krystal Brown, Karla Bowles, Benjamin Roa.
      A substantial proportion of pathogenic variants associated with an increased risk of hereditary cancer are sequence variants affecting RNA splicing. The classification of these variants can be complex when both non-functional and functional transcripts are produced from the variant allele. We present four BRCA2 splice site variants with complex variant interpretations (BRCA2 c.68-3T>G, c.68-2A>G, c.425G>T, c.8331+2T>C). Evidence supporting a pathogenic classification is available for each variant, including in silico models, absence in population databases, and published functional data. However, comprehensive RNA analysis showed that some functional transcript may be produced by each variant. BRCA2 c.68-3T>G results in a partial splice defect. For BRCA2 c.68-2A>G and c.425G>T, aberrant splicing was shown to produce a potentially functional, in-frame transcript. BRCA2 c.8331+2T>C may utilize a functional GC donor in place of the wild-type GT donor. The severity of cancer history for carriers of these variants was also assessed using a history weighting algorithm and was not consistent with pathogenic controls (carriers of known pathogenic variants in BRCA2). Due to the conflicting evidence, our laboratory classifies these BRCA2 variants as variants of uncertain significance. This highlights the importance of evaluating new and existing evidence to ensure accurate variant classification and appropriate patient care.
    Keywords:  BRCA2; Hereditary cancer syndromes; Pathogenicity; RNA analysis; Splice variants
    DOI:  https://doi.org/10.1007/s10689-020-00224-y
  10. Hered Cancer Clin Pract. 2021 Jan 19. 19(1): 9
    Recontacting non-BRCA1/2 breast cancer patients for germline CHEK2 c.1100del pathogenic variant testing: uptake and patient experiences.
    Mary E Velthuizen, Rob B van der Luijt, Beja J de Vries, Marco J Koudijs, Eveline M A Bleiker, Margreet G E M Ausems.
       BACKGROUND: CHEK2 has been recognized as a breast cancer risk gene with moderate effect. Women who have previously tested negative for a BRCA1/2 gene germline pathogenic variant may benefit from additional genetic testing for the CHEK2 c.1100del pathogenic variant. The aims of this study were: 1) to assess the uptake of an active approach by recontacting BRCA1/2-negative women for additional CHEK2 c.1100del testing on stored DNA-samples and 2) to explore patients' experiences with this approach.
    METHODS: Between 2015 and 2017, women who had been tested earlier negative for BRCA1/2 germline pathogenic variants, were recontacted for additional CHEK2 c.1100del testing on stored DNA-samples, free-of-charge. They received an information letter about the CHEK2 pathogenic variant and could return an informed consent form when they opted for additional genetic testing. Those in whom the CHEK2 pathogenic variant was absent, received a letter describing this result. Those who tested positive, were invited for a personal counseling at the department of genetics. On average 21 months (range 4-27) after the genetic test result, a questionnaire was sent to all identified carriers and a control group of women who tested negative for the pathogenic variant to explore patients' experiences with our approach.
    RESULTS: In total, 70% (N = 1666) of the N = 2377 women contacted opted for additional testing, and 66 (4%) of them proved to be carriers of the CHEK2 c.1100del pathogenic variant. Regardless of the outcome of the genetic test, women were generally satisfied with our approach and reported that the written information was sufficient to make an informed decision about the additional CHEK2 testing.
    CONCLUSIONS: The uptake (70%) of our approach was considered satisfactory. Patients considered the benefits more important than the psychosocial burden. Given the rapid developments in DNA-diagnostics, our findings may support future initiatives to recontact patients about additional genetic testing when they previously tested negative for a pathogenic variant in a breast cancer gene.
    Keywords:  Breast cancer risk; CHEK2 c.1100del pathogenic variant; Recontacting; Uptake testing
    DOI:  https://doi.org/10.1186/s13053-021-00166-1
  11. Br J Cancer. 2021 Jan 21.
    Long-term risk of subsequent cancer incidence among hereditary and nonhereditary retinoblastoma survivors.
    Sara J Schonfeld, Ruth A Kleinerman, David H Abramson, Johanna M Seddon, Margaret A Tucker, Lindsay M Morton.
       BACKGROUND: Increased sarcoma and melanoma risks after hereditary retinoblastoma are well established, whereas less is known about epithelial subsequent malignant neoplasms (SMNs) and risks for multiple (≥2) SMNs.
    METHODS: Leveraging long-term follow-up and detailed histologic information, we quantified incident SMN risk among 1128 hereditary and 924 nonhereditary retinoblastoma survivors (diagnosed 1914-2006; follow-up through 2016). Standardised incidence ratios (SIRs) compared cancer risk after retinoblastoma relative to the general population. We estimated cumulative incidence accounting for competing risk of death.
    RESULTS: Hereditary survivors had statistically significantly increased SMN risk (N = 239; SIR = 11.9; 95% confidence interval [CI] 10.4-13.5), with SIRs >80-fold for sarcomas, nasal cavity tumours and pineoblastoma. Significantly increased risks were also observed for melanoma and central nervous system, oral cavity and breast SMNs (SIRs = 3.1-17), but not the uterus, kidney, lung, bladder, pancreas or other types. Cumulative incidence 50 years following hereditary retinoblastoma was 33.1% (95% CI 29.0-37.2) for a first SMN and 6.0% (95% CI 3.8-8.2) for a second SMN. SMN risk was not increased after nonhereditary retinoblastoma (N = 25; SIR = 0.8; 95% CI 0.5-1.2).
    CONCLUSION: Beyond the established sarcoma and melanoma risks after hereditary retinoblastoma, we demonstrate increased risk for a more limited number of epithelial malignancies than previously suggested. Cumulative incidence estimates emphasise long-term SMN burden after hereditary retinoblastoma.
    DOI:  https://doi.org/10.1038/s41416-020-01248-y
  12. BMJ Case Rep. 2021 Jan 18. pii: e238100. [Epub ahead of print]14(1):
    ATM germline variants and male breast cancer.
    Renato Cunha, Priscila Nejo, Sandra Bento, Fátima Vaz.
      Male breast cancer is rare and has been frequently associated with cancer predisposing variants, particularly in BRCA 1 and BRCA 2 genes. ATM pathogenic variants may also increase risk for breast and other cancers. However, less than 10 cases relating ATM mutations and male breast cancer have been previously reported. Therefore, risk estimates and surveillance recommendations are not well established. We report a case of a male patient with breast cancer found to be heterozygous for a pathogenic ATM variant after multigene testing. We also review the literature regarding increased cancer risk associated with ATM germline variants, with emphasis on potential recommendations for surveillance and follow-up.
    Keywords:  Breast cancer; Genetic screening / counselling; Genetics; Oncology
    DOI:  https://doi.org/10.1136/bcr-2020-238100
  13. Int J Mol Sci. 2021 Jan 17. pii: E889. [Epub ahead of print]22(2):
    A Case Report of Germline Compound Heterozygous Mutations in the BRCA1 Gene of an Ovarian and Breast Cancer Patient.
    Ava Kwong, Cecilia Y S Ho, Vivian Y Shin, Chun Hang Au, Tsun Leung Chan, Edmond S K Ma.
      The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers.
    Keywords:  Chinese; Fanconi anemia; compound heterozygous mutations; hereditary breast cancer
    DOI:  https://doi.org/10.3390/ijms22020889
  14. Biochemistry. 2021 Jan 20.
    Ubiquitin Ligase Activities of WWP1 Germline Variants K740N and N745S.
    Hanjie Jiang, Daniel R Dempsey, Philip A Cole.
      WWP1 is an E3 ubiquitin ligase that has been reported to target the tumor suppressor lipid phosphatase PTEN. K740N and N745S are recently identified germline variants of WWP1 that have been linked to PTEN-associated cancers [Lee, Y. R., et al. (2020) N. Engl. J. Med.]. These WWP1 variants have been suggested to release WWP1 from its native autoinhibited state, thereby promoting enhanced PTEN ubiquitination as a mechanism for driving cancer. Using purified proteins and in vitro enzymatic assays, we investigate the possibility that K740N and N745S WWP1 possess enhanced ubiquitin ligase activity and demonstrate that these variants are similar to the wild type (WT) in both autoubiquitination and PTEN ubiquitination. Furthermore, K740N and N745S WWP1 show dependencies similar to those of WT in terms of allosteric activation by an engineered ubiquitin variant, upstream E2 concentration, and substrate ubiquitin concentration. Transfected WWP1 WT and mutants demonstrate comparable effects on cellular PTEN levels. These findings challenge the idea that K740N and N745S WWP1 variants promote cancer by enhanced PTEN ubiquitination.
    DOI:  https://doi.org/10.1021/acs.biochem.0c00869
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