DNMT3A R882 Mutations Confer Unique Clinicopathologic Features in MDS Including a High Risk of AML Transformation

DNMT3A mutations play a prominent role in clonal hematopoiesis and myeloid neoplasms with arginine (R)882 as a hotspot, however the clinical implications of R882 vs. non-R882 mutations in myeloid neoplasms like myelodysplastic syndrome (MDS) is unclear. By data mining with publicly accessible cancer genomics databases and a clinical genomic database from a tertiary medical institution, DNMT3A R882 mutations were found to be enriched in AML (53% of all DNMT3A mutations) but decreased in frequency in clonal hematopoiesis of indeterminate potential (CHIP) (10.6%) or other myeloid neoplasms including MDS (27%) (p<.001). Next with the largest cohort of patients with DNMT3A R882 mutant MDS known to date from multiple institutions, DNMT3A R882 mutant MDS cases were shown to have more severe leukopenia, enriched SRSF2 and IDH2 mutations, increased cases with excess blasts (47% vs 22.5%, p=.004), markedly increased risk of AML transformation (25.8%, vs. 1.7%, p=.0001) and a worse progression-free survival (PFS) (median 20.3, vs. >50 months, p=.009) than non-R882 mutant MDS cases. DNMT3A R882 mutation is an independent risk factor for worse PFS, and importantly the differences in the risk of AML transformation between R882 vs. non-R882 mutant patients cannot be explained by different treatment approaches. Interestingly the higher risk of AML transformation and the worse PFS in DNMT3A R882 mutant MDS cases are mitigated by coexisting SF3B1 or SRSF2 mutations. The unique clinicopathologic features of DNMT3A R882 mutant MDS shed light on the prognostic and therapeutic implications of DNMT3A R882 mutations.

Clinical validation of coexisting driver mutations in colorectal cancers

Mutational profiling is recommended for selecting targeted therapy and predicting prognosis of metastatic colorectal cancer (CRC). Detection of coexisting mutations within the same pathway, which are usually mutually exclusive, raises the concern for potential laboratory errors. In this retrospective study for quality assessment of a next-generation sequencing assay, we examined BRAF, KRAS, and NRAS genes within the mitogen-activated protein kinase (MAPK) pathway and the PIK3CA gene within the phosphatidylinositol 3-kinase (mTOR) pathway in 744 CRC specimens submitted to our clinical diagnostics laboratory. Although coexistence of mutations between the MAPK and mTOR pathways was observed, it rarely occurred within the MAPK pathway. Retrospective quality assessments identified false detection of coexisting activating KRAS and NRAS mutations in 1 specimen and confirmed 2 activating KRAS mutations in 2 specimens and coexisting activating KRAS and NRAS mutations in 2 specimens, but no coexisting activating RAS and BRAF mutations. There were 15 CRCs with a kinase-impaired BRAF mutation, including 3 with a coexisting activating KRAS mutation, which may have therapeutic implications. Multiregional analysis based on different histologic features demonstrated that coexisting KRAS and NRAS mutations may be present in the same or different tumor populations and showed that invasion of adenomas by synchronous adenocarcinomas of different clonal origin may result in detection of coexisting mutations within the MAPK pathway. In this study, we proposed an operating procedure for clinical validation of unexpected coexisting mutations. Further studies are warranted to elucidate the biological significance and clinical implications of coexisting mutations within the MAPK pathway.

Assessment of RAS Dependency for BRAF Alterations Using Cancer Genomic Databases

IMPORTANCE

Understanding RAS dependency and mechanisms of RAS activation in non-V600 BRAF variant cancers has important clinical implications. This is the first study to date to systematically assess RAS dependency of BRAF alterations with real-world cancer genomic databases.

OBJECTIVE

To evaluate RAS dependency of individual BRAF alterations through alteration coexistence analysis using cancer genomic databases.

DESIGN AND SETTING

A cross-sectional data analysis of 119 538 nonredundant cancer samples using cancer genomics databases including GENIE (Genomics Evidence Neoplasia Information Exchange) and databases in cBioPortal including TCGA (The Cancer Genome Atlas) (accessed March 24, 2020), in addition to 2745 cancer samples from Mayo Clinic Genomics Laboratory (January 1, 2015, to July 1, 2020). Frequencies and odds ratios of coexisting alterations of RAS (KRAS, NRAS and HRAS) and RAS regulatory genes (NF1, PTPN11 and CBL) were calculated for individual BRAF alterations, and compared according to the current BRAF alteration classification; cancer type specificity of coexisting alterations of RAS or RAS regulatory genes was also evaluated.

MAIN OUTCOMES AND MEASURES

Primary outcome measurement is enrichment of RAS (KRAS, NRAS and HRAS) alterations in BRAF variant cancers. Secondary outcome measurement is enrichment of RAS regulatory gene (NF1, PTPN11, and CBL) in BRAF variant cancers.

RESULTS

A total of 2745 cancer samples from 2708 patients (female/male ratio: 1.0) tested by Mayo Clinic Genomics Laboratory and 119 538 patients (female/male ratio: 1.1) from GENIE and cBioPortal database were included in the study. In 119 538 nonredundant cancer samples, class 1 BRAF alterations and BRAF fusions were found to be mutually exclusive to alterations of RAS or RAS regulatory genes (odds ratio range 0.03-0.13 and 0.03-0.73 respectively), confirming their RAS independency. Both class 2 and class 3 BRAF alterations show variable and overlapping levels of enriched RAS alterations (odds ratio range: 0.03-5.9 and 0.63-2.52 respectively), suggesting heterogeneity in RAS dependency and a need to revisit BRAF alteration classification. For RAS-dependent BRAF alterations, the coexisting alterations also involve RAS regulatory genes by enrichment analysis (for example, S467L shows an odds ratio of 8.26 for NF1, 9.87 for PTPN11, and 15.23 for CBL) and occur in a variety of cancer types with some coalterations showing cancer type specificity (for example, HRAS variations account for 46.7% of all coexisting RAS alterations in BRAF variant bladder cancers, but 0% in non-small cell lung cancers). Variant-level assessment shows that BRAF alterations involving the same codon may differ in RAS dependency. In addition, RAS dependency of previously unclassified BRAF alterations could be assessed.

CONCLUSIONS AND RELEVANCE

Current BRAF alteration classification based on in vitro assays does not accurately predict RAS dependency in vivo for non-V600 BRAF alterations. RAS-dependent BRAF variant cancers with different mechanisms of RAS activation suggest the need for different treatment strategies.

Evaluation of Global Hemostatic Assays in Response to Factor VIII Inhibitors

Global hemostatic assays including thromboelastography (TEG), Innovance ETP (endogenous thrombin potential), and Thrombinoscope could measure thrombin generation potential and be useful to guide management of patients with factor VIII (FVIII) inhibitors. However, the performance characteristics of these global assays in the presence of FVIII inhibitors are incompletely characterized. In this study, the normal range of thrombin generation potential was measured in 20 healthy individuals by all 3 assays. In 5 commercial and 7 clinical samples with FVIII inhibitors, it was shown that PPP-reagent thrombinoscope shows a dose-dependent response to different levels of FVIII inhibitors from the same patients, while Innovance ETP shows virtually no response to FVIII inhibitors. The TEG is more sensitive to FVIII inhibitors than thrombinoscope. Importantly, we show the same levels of FVIII inhibitor from different patients results in different levels of inhibition for thrombin generation potential by thrombinoscope, which potentially explains the phenotypic heterogeneity of patients with FVIII inhibitors. Global assays such as thrombinoscope, but not Innovance ETP, show appropriate sensitivity to FVIII inhibitors that could offer an objective and clinically relevant marker to guide patient management.

The Clinical Utility of the Heparin Neutralization Assay in the Diagnosis of Heparin-Induced Thrombocytopenia

Heparin-induced thrombocytopenia (HIT) remains diagnostically challenging. Immunoassays including PF4/heparin enzyme-linked immunosorbent assay (ELISA) have high sensitivity but low specificity. Whether the heparin neutralization assay (HNA) improves the diagnostic accuracy of the PF4/heparin ELISA for HIT is uncertain. In this study, to assess its clinical utility and evaluate whether it improves the diagnostic accuracy for HIT, we implemented HNA in conjunction with PF4/heparin ELISA over a 1-year period. A total of 1194 patient samples were submitted to the laboratory for testing from December 2015 to November 2016. Heparin neutralization assay alone is a poor predictor for HIT, but it has high negative predictive value (NPV): Cases with %inhibition <70% are always negative for serotonin release assay. It improves the diagnostic positive predictive value (PPV) of ELISA without compromising sensitivity: ELISA optical density (OD) ≥1.4 alone has a sensitivity of 88% (14/16) and a PPV of 61% (14/23); with HNA %inhibition ≥70%, the sensitivity remains 88% (14/16) and PPV is 82% (14/17). 4Ts score correlates with ELISA OD and predicts HIT; the predictive accuracy of 4Ts score is further improved by HNA. Interestingly, HNA %inhibition of <70% correlates with low 4Ts scores. Based on its high NPV, HNA has the potential to facilitate more timely and accurate HIT diagnosis.