Identifying patients with NTRK fusion cancer

Due to the efficacy of tropomyosin receptor kinase (TRK) inhibitor therapy and the recent Food and Drug Administration approval of larotrectinib, it is now clinically important to accurately and efficiently identify patients with neurotrophic TRK (NTRK) fusion-driven cancer. These oncogenic fusions occur when the kinase domain of NTRK1, NTRK2 or NTRK3 fuse with any of a number of N-terminal partners. NTRK fusions are characteristic of a few rare types of cancer, such as secretory carcinoma of the breast or salivary gland and infantile fibrosarcoma, but they are also infrequently seen in some common cancers, such as melanoma, glioma and carcinomas of the thyroid, lung and colon. There are multiple methods for identifying NTRK fusions, including pan-TRK immunohistochemistry, fluorescence in situ hybridisation and sequencing methods, and the advantages and drawbacks of each are reviewed here. While testing algorithms will obviously depend on availability of various testing modalities and economic considerations for each individual laboratory, we propose triaging specimens based on histology and other molecular findings to most efficiently identify tumours harbouring these treatable oncogenic fusions.

Enrichment of kinase fusions in ESR1 wild-type, metastatic breast cancer revealed by a systematic analysis of 4854 patients

BACKGROUND

Kinase fusions are rare and poorly characterized in breast cancer (BC). We aimed to characterize kinase fusions within a large cohort of advanced BC.

PATIENTS AND METHODS

A total of 4854 patients with BC were analyzed by Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets (MSK-IMPACT) targeted DNAseq and MSK-Fusion targeted RNAseq during the study time period.

RESULTS

Twenty-seven of 4854 (0.6%) patients harbored fusions: 11 FGFR (five FGFR2, three FGFR3, three FGFR1), five BRAF, four NTRK1, two RET, two ROS1, one ALK, one ERBB2, and one MET. A history of endocrine therapy was present in 15 (56%) of fusion-positive BC; eight of the 15 cases had available pre-treatment samples, of which six were fusion-negative. None of the fusion-positive BC samples harbored ESR1 hotspot mutations. Two patients with acquired LMNA-NTRK1 fusions and metastatic disease received larotrectinib and demonstrated clinical benefit.

CONCLUSION

Kinase fusions in BC are extremely rare, and appear to be enriched in hormone-resistant, metastatic carcinomas and mutually exclusive with ESR1 mutations. The present study expands the spectrum of genetic alterations activating mitogen-activated protein kinase (MAPK) signaling that can substitute for ESR1 mutations in this setting. Molecular testing at progression after endocrine therapy should include fusion testing, particularly in the absence of ESR1 hotspot alterations, in an effort to identify additional therapeutic options which may provide substantial clinical benefit.

Genetic variation in IL28B and treatment outcome in HBeAg-positive and -negative chronic hepatitis B patients treated with Peg interferon alfa-2a and adefovir

In a cohort of 95 chronic hepatitis B patients, who were treated with peg-interferon and adefovir for 1 year, and who had 15% HBsAg loss (overall), no association was found between IL28B polymorphisms and HBeAg seroconversion or HBsAg clearance. These findings suggest that any association with outcome, if present, is less than that seen in chronic hepatitis C. Additional studies are needed to enlarge sample size and to refine our understanding of IL28B biology in the context of chronic hepatitis B response to immunomodulatory and direct antiviral therapy.

Association of the homeobox transcription factor, ENGRAILED 2, 3, with autism spectrum disorder

Mouse mutants of the homeobox transcription factor Engrailed2 (En2) and autistic individuals display similar cerebellar morphological abnormalities, which include hypoplasia and a decrease in the number of Purkinje cells. Human EN2 maps to 7q36, a chromosomal region that has demonstrated suggestive linkage to autism spectrum disorder (ASD). To investigate EN2 for evidence of association with ASD, four single-nucleotide polymorphisms (SNPs) (rs3735653, rs1861972, rs1861973, rs2361689) that span the majority of the 8.0 kb gene were assessed by the transmission/disequilibrium test. Initially, 138 triads of autistic individuals and their parents were tested. Two intronic SNPs (rs1861972 and rs1861973) demonstrated significant association with autism (rs1861972, P=0.0018; rs1861973, P=0.0003; haplotype, P=0.000005). Flanking exonic SNPs (rs3735653 and rs2361689) did not display association. This analysis was then extended to include 167 small nuclear ASD pedigrees and significant association was again only observed for rs1861972 and rs1861973 under both the narrow and broad diagnostic criteria (narrow: rs1861972 P=0.0290, rs1861973 P=0.0073, haplotype P=0.0009; broad: rs1861972 P=0.0175, rs1861973 P=0.0107, haplotype P=0.0024). These data demonstrate association between a cerebellar patterning gene and ASD, suggesting a role for EN2 as a susceptibility locus and supporting a neurodevelopmental defect hypothesis in the etiology of autism.