Treatment outcome of atypical EGFR mutations in the German National Network Genomic Medicine Lung Cancer (nNGM).

BACKGROUND: Atypical EGFR mutations occur in 10%-30% of non-small-cell lung cancer (NSCLC) patients with EGFR mutations and their sensitivity to classical epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKI) is highly heterogeneous. Patients harboring one group of uncommon, recurrent EGFR mutations (G719X, S768I, L861Q) respond to EGFR-TKI. Exon 20 insertions are mostly insensitive to EGFR-TKI but display sensitivity to exon 20 inhibitors. Clinical outcome data of patients with very rare point and compound mutations upon systemic treatments are still sparse to date. PATIENTS AND METHODS: In this retrospective, multicenter study of the national Network Genomic Medicine (nNGM) in Germany, 856 NSCLC cases with atypical EGFR mutations including co-occurring mutations were reported from 12 centers. Clinical follow-up data after treatment with different EGFR-TKIs, chemotherapy and immune checkpoint inhibitors were available from 260 patients. Response to treatment was analyzed in three major groups: (i) uncommon mutations (G719X, S7681, L861Q and combinations), (ii) exon 20 insertions and (iii) very rare EGFR mutations (very rare single point mutations, compound mutations, exon 18 deletions, exon 19 insertions). RESULTS: Our study comprises the largest thus far reported real-world cohort of very rare EGFR single point and compound mutations treated with different systemic treatments. We validated higher efficacy of EGFR-TKI in comparison to chemotherapy in group 1 (uncommon), while most exon 20 insertions (group 2) were not EGFR-TKI responsive. In addition, we found TKI sensitivity of very rare point mutations (group 3) and of complex EGFR mutations containing exon 19 deletions or L858R mutations independent of the combination partner. Notably, treatment responses in group 3 (very rare) were highly heterogeneous. Co-occurring TP53 mutations exerted a non-significant trend for a detrimental effect on outcome in EGFR-TKI-treated patients in groups 2 and 3 but not in group 1. CONCLUSIONS: Based on our findings, we propose a novel nNGM classification of atypical EGFR mutations.

Evidence for a polygenic contribution to androgenetic alopecia.

BACKGROUND: Male pattern baldness (androgenetic alopecia, AGA) is a highly heritable trait and the most common form of hair loss in humans. Eight genome-wide significant risk loci for AGA have been identified. OBJECTIVES: To determine whether a polygenic component contributes to the genetic risk for AGA. METHODS: This study used a German case-control sample for AGA, which comprised 581 severely affected patients and 617 controls, to determine the contribution of polygenic variance to AGA risk. The sample was divided evenly into discovery and test samples. An additive polygenic risk score was calculated from risk alleles with increasingly liberal P-values in the discovery dataset, which was then used to test for the enrichment of AGA risk score alleles in the independent test samples. RESULTS: The polygenic score analysis provided significant evidence for a polygenic contribution to AGA where the amount of variance explained was 1·4-4·5%. CONCLUSION: This study provides evidence for the specific contribution of a polygenic component to the overall heritable risk for AGA. To some degree, the polygenic architecture of AGA might reflect the complexity of the biological pathways involved. Further analyses and strategies that complement conventional genome-wide association studies are needed to identify these factors. These may include pathway-based analyses, the analysis of functional candidate genes and tests for epistatic effects with known loci.

Susceptibility variants on chromosome 7p21.1 suggest HDAC9 as a new candidate gene for male-pattern baldness.

BACKGROUND: Male-pattern baldness (androgenetic alopecia, AGA) is the most common form of hair loss among humans. Research has shown that it is caused by genetic factors. Numerous studies have unequivocally identified two major genetic risk loci for AGA: the X-chromosomal AR/EDA2R locus, and the PAX1/FOXA2 locus on chromosome 20. OBJECTIVES: To identify further candidate genes for AGA, and thus gain further insights into this phenotype. METHODS: A German sample of 581 severely affected cases and 617 controls was used to perform a genome-wide association study. The identified associated locus was further analysed by fine-mapping, and then independently replicated in an Australian sample. Expression and pathway analyses were performed to characterize the susceptibility gene identified. RESULTS: The most significant association signal was obtained for rs756853 (P = 1·64 × 10(-7) ), which is located intronically in the histone deacetylase 9 (HDAC9) gene. Fine-mapping and a family-based analysis revealed that rs756853 and the 6-kb distal rs2249817 were the most highly associated single nucleotide polymorphisms. The association finding was replicated in an independent Australian sample, when the analysis was restricted to severely affected cases and unaffected controls (P = 0·026). Analysis of rs2249817 in a combined sample of severely affected German and Australian cases and unaffected controls revealed a strong association signal (P = 9·09 × 10(-8) ). Tissue expression studies demonstrated HDAC9 expression in various tissues, including tissues of relevance to AGA. No strong genotypic effects were observed in genotype-specific expression or splice studies. Pathway analyses supported the hypothesis that HDAC9 plays a functional role in AGA via interaction with the AR gene. CONCLUSIONS: The present study suggests that HDAC9 is the third AGA susceptibility gene.

The hairless gene in androgenetic alopecia: results of a systematic mutation screening and a family-based association approach.

BACKGROUND: Genetic disposition and androgen dependence are important characteristics of the common patterned loss of scalp hair known as androgenetic alopecia (AGA). The genetic factors contributing to AGA are currently unknown. The human hairless gene (HR) has recently been cloned and mutations have been reported in families with autosomal recessive universal congenital alopecia and papular atrichia. The main feature of these disorders is persistent complete absence of hair at or shortly after birth. This suggests that HR is essential and specific for the development of hair. OBJECTIVES: To test the hypothesis that HR may be involved in AGA. METHODS: We systematically screened HR for genetic variability by means of single-strand conformation analysis (SSCA) in 46 unrelated men with AGA. To test for an involvement of HR in the development of AGA, seven common variants were genotyped in 61 families with 93 affected offspring. The results were analysed with the transmission/disequilibrium test (TDT). RESULTS: SSCA showed 15 single nucleotide substitutions: eight missense mutations, four silent mutations and three mutations in exon-flanking intronic sequences. TDT results showed a marginally significant association between AGA and variants 3379-29G/T (P = 0.024) and 2611-68C/T (P = 0.047). These results, however, did not remain significant after applying the conservative Bonferroni correction for multiple testing. CONCLUSIONS: Our results do not provide evidence for a strong involvement of HR in the development of AGA, although a minor role cannot be fully excluded.

A distinct gene close to the hairless locus on chromosome 8p underlies hereditary Marie Unna type hypotrichosis in a German family.

BACKGROUND: Hypotrichosis of the Marie Unna type (HMU) is a rare autosomal dominant disorder characterized by male-pattern hair loss with childhood onset and anomalies of the hair shaft. OBJECTIVES: We aimed to evaluate a number of chromosomal loci as possible candidate regions for HMU. METHODS: A linkage analysis was performed in a large German family using microsatellite markers spanning candidate regions on chromosomes 8, 12 and 17. RESULTS: We found that the HMU locus maps to chromosomal region 8p21 in a 13.01-cM interval between markers D8S1145 and D8S1771. This interval harbours the hairless gene (HR). Mutational analysis of HR on the genomic and transcript levels revealed no pathogenic mutation. CONCLUSIONS: Our findings, together with a recent report of two unrelated families of Dutch and British origin, provide evidence for a hair growth regulatory gene distinct from HR in chromosomal region 8p21.

Novel Hairless mutations in two kindreds with autosomal recessive papular atrichia.

Papular atrichia is an autosomal recessive disorder characterized clinically by the occurrence of universal congenital alopecia and disseminated papular lesions. Recently, mutations in the human hairless (HR) gene have been reported in Irish and Arab Palestinian families with papular atrichia. We have studied two further kindreds with this clinical phenotype from other ethnic backgrounds. For mutation detection the complete coding region as well as exon-intron boundaries of the HR gene were sequenced. The first family is a Mexican family with clinically typical papular atrichia. Sequencing identified a homozygous deletion of 4 bp in exon 7 (2001delCCAG) leading to a premature stop codon in exon 8. The second family is a South Tyrolian family with affected individuals showing papular atrichia and retardation of bone age during childhood. All affected individuals were identified as homozygous for an A-->G transition at nucleotide position 2909 (exon 14) leading to an amino acid change of asparagine to serine in codon 970 (Asn970Ser). These data provide further evidence for the involvement of hairless mutations in papular atrichia. In addition, these findings suggest that the hairless protein is not only involved in hair development but also in the process of ossification during development.