Reporting TP53 gene analysis results in CLL

Transcription

1 Reporting TP53 gene analysis results in CLL

2 Mutations in TP53 - From discovery to clinical practice in CLL Discovery Validation Clinical practice Variant diversity *Leroy at al, Cancer Research Review 2017

3 Mutations in TP53 - From discovery to clinical practice in CLL Discovery Validation Clinical practice Variant diversity NCBI - TP53 and CLL

4 Mutations in TP53 - From discovery to clinical practice in CLL (cont d) Discovery Validation Clinical practice Variant diversity NCBI - TP53 and CLL Eichhorst (ESMO) Ann. Clin. Onc 2015 Stilgenbauer et al, Blood 2014 Gonzales JCO 2010 Rossi Clin Canc Res 2009 Dicker et al. Leukemia 2009 Zenz et al. Blood 2008 Malcikova et al. Mol. Immunol

5 Mutations in TP53 - From discovery to clinical practice in CLL (cont d) Discovery Validation Clinical practice Variant diversity Variant reports

6 From variant detection to clinical report Sequencing Detection

7 From variant detection to clinical report Sequencing Detection Validation Variant artifact Sanger: Enzyme Slippage Dye Blob DNA loop/hairpin Contamination NGS: PCR dublicates First bp read Low Q30/ Low Coverage Contamination

8 From variant detection to clinical report Sequencing Detection Validation Variant artifact VAF<10% omit variants with VAF <10% / not confirmable via Sanger 1) Higher risk for false positive results 2) Clinical significance remains unclear

9 From variant detection to clinical report Sequencing Detection Validation Variant Interpretation pathogenic variant artifact VAF<10% SNPs Single nucleotide polymorphisms or just polymorphisms are variants with a frequency of >1% in healthy. 97 known in TP53, only 5 exonic missense TP53 SNPs. Rest is rare non-disease coding variants or rare non-pathogenic variants.

10 From variant detection to clinical report Sequencing Detection Validation Variant Interpretation pathogenic variant artifact VAF<10% SNPs pathogenic or not? => Samesense, missense, intronic, exonic, splice site... => Databases (dbsnp, 1000g, IARC, COSMIC, SESHAT) => Prediction tools (SIFT, POLYPHEN) => Non-tumor control (CD19neg, saliva, remission sample)

11 From variant detection to clinical report Sequencing Detection Validation Variant Interpretation pathogenic variant hereditary pathogenic variants tumor associated pathogenic variant Report artfact VAF<10% SNPs pathogenic or not? => Samesense, missense, intronic, exonic, splice site... => Databases (dbsnp, 1000g, IARC, COSMIC, SESHAT) => Prediction tools (SIFT, POLYPHEN) => Non-tumor control (CD19neg, saliva, remission sample)

12 From variant detection to clinical report Sequencing Detection Validation Variant Interpretation pathogenic variant hereditary pathogenic variants tumor associated pathogenic variant Report Clinical consequence artifact VAF<10% SNPs pathogenic or not? => Samesense, missense, intronic, exonic, splice site... => Databases (dbsnp, 1000g, IARC, COSMIC, SESHAT) => Prediction tools (SIFT, POLYPHEN) => Non-tumor control (CD19neg, saliva, remission sample)

13 Evidence based variant categorization Standards and Guidelines for the Interpretation and Reporting of Sequence Variants in Cancer a Joint Consensus Recommendation of the Association for Molecular Pathology, American Society of Clinical Oncology and College of American Pathologists Li et al., Journal of Molecular Diagnostics 2016

14 Evidence based variant categorization What the clinician wants to know: Mutated or not? Standards and Guidelines for the Interpretation and Reporting of Sequence Variants in Cancer a Joint Consensus Recommendation of the Association for Molecular Pathology, American Society of Clinical Oncology and College of American Pathologists Li et al., Journal of Molecular Diagnostics 2016

15 Evidence based variant categorization What the clinician wants to know: Mutated or not? Mutation rare in TP53 SNP/ rare non pathogenic variant Li et al., Journal of Molecular Diagnostics 2016

16 TP53 mutation type Missense, Silent, Nonsense? ~ 73% of mutations are missense and the pathogenic value unclear (database!) ~17% of mutations are nonsense or frameshift=> generally pathogenic (database!). ~2% are splice site => pathogenic Silent and intronic mutations are generally of no pathogenic effect. However very few variants have proven effect on splicing and RNA processing (Database!)

17 TP53 mutation type (cont d) Exonic, intronic, splice site? TP53 exon 6

18 Intronic Splice site Splice site Intronic TP53 mutation type (cont d) Exonic, intronic, splice site? TP53 exon 6 Exonic

19 Intronic Splice site Splice site Intronic TP53 mutation type splice site mutations Exonic, intronic, splice site? TP53 exon 6 Exonic +/-2bp from start/end covers the splice site often characterized by AGGT

20 ERIC TP53 certification splice site mutations (cont d) Passed Good laboratory practice; 4 25 labs Failed All mutations detected, but exons 4-9 not covered; 1 Passed; 10 Wrong annotation; 1 Splice site mutation detected, but not evaluated as a mutation; 3 Splice site mutation not detected; 3 Not identified at least 2 samples correctly; 3

21 TP53 mutation analysis pitfalls in variant identification Missense, Silent, Nonsense? This nonsense mutation / stop codon leads to an amino acid substitution. p. R213R: The TP53 variant c.639a>g, which lead to an amino acid change in codon 213.

22 TP53 mutation analysis databases Population databases: 1000 Genomes Project, Exome Variant Server, dbsnp P72R SNP / Polymorphism

23 TP53 mutation analysis databases (cont d) Population databases: 1000 Genomes Project, Exome Variant Server, dbsnp??? P72R SNP / Polymorphism

24 TP53 mutation analysis databases (cont d) Cancer-specific variant databases Catalog of Somatic Mutations in Cancer (COSMIC) IARC TP53 mutation database

25 TP53 mutation analysis databases (cont d) Cancer-specific variant databases Catalog of Somatic Mutations in Cancer (COSMIC) IARC TP53 mutation database

26 % of Respondents TP53 mutation analysis pitfalls in variant identification What database do you use for mutation validation? Polymorphisms and Mutations ,83 61,02 52,54 40,68 27,12 Database 0 5,08. P72R: This SNP is likely benign, possible clinical significance affecting drug response. p.pro72arg (rs ) is related with a higher risk of breast cancer, and is not associated with Systemic Lupus Erythematosus in Caucasians, African-Americans, and Asian children and adult. IARC TP53 database TP53 website (UMD database COSMIC dbsnp ClinVar None I am not sure

27 TP53 mutation analysis pitfalls in variant identification Prediction tools SIFT prediction is based on the degree of conservation of amino acid residues in sequence alignments derived from closely related sequences Polyphen-2 possible impact of an amino acid substitution on the structure and function of a human protein using straightforward physical and comparative considerations Specificity of only 60-80% i.e. SIFT result for BRAF V600E => Benign

28 TP53 mutation analysis pitfalls in variant identification Prediction tools SIFT prediction is based on the degree of conservation of amino acid residues in sequence alignments derived from closely related sequences Polyphen-2 possible impact of an amino acid substitution on the structure and function of a human protein using straightforward physical and comparative considerations Specificity of only 60-80% i.e. SIFT result for BRAF V600E => Benign TA class Overall transcriptional activity (TA) on 8 different promoters Missense mutations are classified as "non-functional" if the median of promotor activity is <=20, "partially functional" if the median is >20 and <=75, "functional" if the median is >75 and <=140, and "supertrans" if the median is >140.

29 TP53 mutation analysis databases (cont d) Cancer-specific variant databases Catalog of Somatic Mutations in Cancer (COSMIC) IARC TP53 mutation database

30 TP53 mutation analysis non-tumor control Non-tumor control derived from tumor free material (saliva, buccal swap, bone marrow) or enriched / purified from same sample (purity control recommended) or sample from a time point of no measurable disease.

31 TP53 mutation analysis non-tumor control Non-tumor control derived from tumor free material (saliva, buccal swap, bone marrow) or enriched / purified from same sample (purity control recommended) or sample from a time point of no measurable disease. variant identified in tumor variant identified in control variant not identified in control rare non-pathogeneic variants germline mutation (very rare) somatic mutation Pitfalls: tumor contamination of nontumor material haematopoetic progenitor cells not considered

32 Should I look for germline variants? Non-tumor control derived from tumor free material (saliva, buccal swap, bone marrow) or enriched / purified from same sample (purity control recommended) or sample from a time point of no measurable disease. variant identified in tumor variant identified in control variant not identified in control rare non-pathogenic variants germline mutation (very rare) somatic mutation

33 Should I look for germline origin of a variant? Clinical suspicious? Variant fraction of 50% (or 100%)? Variant with high prevalence in patients with Li Fraumeni (like) syndrome.

34 Should I look for germline origin of a variant? Clinical suspicious? Variant fraction of 50% (or 100%)? Variant with high prevalence in patients with Li Fraumeni (like) syndrome?

35 Should I look for germline origin of a variant? Clinical suspicious? Variant fraction of 50% (or 100%)? Variant with high prevalence in patients with Li Fraumeni (like) syndrome?

36 Should I look for germline origin of a variant? Clinical suspicious? Variant fraction of 50% (or 100%)? Variant with high prevalence in patients with Li Fraumeni (like) syndrome?

37 % of Respondents Should I look for germline origin of a variant? Clinical suspicious? Variant fraction of 50% (or 100%)? Variant with high prevalence in patients with Li Fraumeni (like) syndrome Do you verify somatic origin of detected variants? 37,29 25,42 20,34 Never In suspicious Cases Always when possible Always I am not sure ,08 11,86

38 Main aspect: Analysis Report

39 Reporting of TP53 variants - Requirements Lab name / Contact details Lab ID Responsible Person

40 Reporting of TP53 variants - Requirements Lab name / Contact details Date of sample acquisition Patient Identifier Sample ID Responsible Person

41 Reporting of TP53 variants - Requirements Lab name / Contact details Analysis details Date of sample acquisition Patient Identifier Type of analysis Type of material and technique (Sensitivity / Specificity) Exons covered & Reference Seq Responsible Person

42 Reporting of TP53 variants - Requirements Lab name / Contact details Result Date of sample acquisition Patient Identifier Type of analysis Type of material and technique (Sensitivity / Specificity) Exons covered & Reference Seq Result Interpretation Reference Responsible Person

43 321t5:c.128G>A Reporting of TP53 variants - Requirements Result 1) Mutated or Unmutated TP53 status 2) Type of mutation (missense, nonsense) 3) Use HGVS to describe mutations chr17.hg19:g c>t or alternatively NG_ :g.17463G>A c.524g>a (NM_ ) p.r175h

44 Reporting of TP53 variants - Requirements Result 1) Mutated or Unmutated TP53 status 2) Type of mutation (missense, nonsense) 3) Use HGVS to describe mutations chr17.hg19:g c>t or alternatively NG_ :g.17463G>A c.524g>a (NM_ ) p.r175h Interpretation summary of the finding in the context of the current state of knowledge (reference)

45 Reporting of TP53 variants Optional results Variant fraction Allelic fraction or cancer cell fraction? Consider tumor content For NGS directly from variant calling > PCR duplicates can give wrong results (>UMIs) > chromosomal Aberrations give wrong results For Sanger only estimation possible Both: Understimation of subclonal TP53 mutations

46 % of Respondents % of Respondents Reporting of TP53 variants Optional results When using NGS, what is the VAF you currently set as the cut-off for reporting in the clinic? 0 9,8 15,69 23,53 3,92 29,41 17,65 <1% 1% 5% 10% We report all found variants irrespective of the VAF I am not sure Other VAF Do you report over-time changes in VAF when the patient is analysed repeatedly? 50,85 13,56 35,59 Response Yes No I am not sure

47 Reporting of TP53 variants Optional results No clinical impact no clinical need for reporting SNP Causing confusion: ( This SNP is likely benign, possible clinical significance affecting drug response. ) Actually providing germline data (Patient identification) => Not recommended

48 % of Respondents Reporting of TP53 variants Optional results Do you report known polymorphisms and benign variants to clinicians? SNP 70 66,1 No clinical impact no clinical need for reporting 60 Causing confusion: ( This SNP is likely benign, possible clinical 50 significance affecting drug response. ) 40 Actually providing germline data (Patient identification) 30 => Not recommended ,95 6,78 5,08 No Yes, only benign variants other than described polymorphisms Yes, only known polymorphisms Yes, Both I am not sure 5,08

49 Reporting of TP53 variants - Requirements Lab name / Contact details Result Date of sample acquisition Patient Identifier Type of analysis Type of material and technique (Sensitivity / Specificity) Exons covered & Reference Seq Result Interpretation Reference Responsible Person

50 Acknowledgements Ulm Hartmut Döhner Stephan Stilgenbauer Eva Moll Melanie Flauger Antonia Feist Sabrina Kless Christina Galler ERIC Office Natalie Sorolla Sonia Amaral Martin Fox ERIC Jitka Malcikova Sarka Pospisilova Davide Rossi Paolo Ghia Kostas Stamatopoulos