Integration of whole-exome and anchored PCR-based next generation sequencing significantly increases detection of actionable alterations in precision oncology

The implementation of an RNA-based gene fusion assay into a diagnostic oncology department: an Australian perspective

Accurate detection of oncogenic gene fusions is important for histological diagnosis of a subset of tumours. Some fusions are also the target of precision therapies. We describe our validation and early diagnostic results for the detection of fusions using the commercially available Illumina TruSight RNA Fusion Panel (TRFP) and the Arriba fusion detection algorithm. Retrospective validation showed that this assay demonstrated high accuracy (94% positive predictive agreement) for a wide variety of fusions. Prospective diagnostic data comprised a cohort of 131 clinical samples (102 mesenchymal tumours, 29 epithelial tumours), of which 80 were excisional specimens and 51 were small specimens, predominantly core biopsies. The test failure rate was 10.7%. We detected 64 (54.7%) clinically-actionable fusions in passed samples, including 12 (10.3%) that either changed or were critical for the diagnosis and 14 (12.0%) that were potentially therapeutically targetable. Most samples (89.7%) fulfilled criteria for partial reimbursement by the Australian Government Medical Benefits Scheme. In addition to describing the utility of an RNA-based fusion assay in cancer diagnostics, it is hoped that this study will provide practical advice for other laboratories considering introducing such a test.

Integration of proteomics in the molecular tumor board

Cancer remains one of the most complex and challenging diseases in mankind. To address the need for a personalized treatment approach for particularly complex tumor cases, molecular tumor boards (MTBs) have been initiated. MTBs are interdisciplinary teams that perform in-depth molecular diagnostics to cooperatively and interdisciplinarily advise on the best therapeutic strategy. Current molecular diagnostics are routinely performed on the transcriptomic and genomic levels, aiming to identify tumor-driving mutations. However, these approaches can only partially capture the actual phenotype and the molecular key players of tumor growth and progression. Thus, direct investigation of the expressed proteins and activated signaling pathways provide valuable complementary information on the tumor-driving molecular characteristics of the tissue. Technological advancements in mass spectrometry-based proteomics enable the robust, rapid, and sensitive detection of thousands of proteins in minimal sample amounts, paving the way for clinical proteomics and the probing of oncogenic signaling activity. Therefore, proteomics is currently being integrated into molecular diagnostics within MTBs and holds promising potential in aiding tumor classification and identifying personalized treatment strategies. This review introduces MTBs and describes current clinical proteomics, its potential in precision oncology, and highlights the benefits of multi-omic data integration.

Diagnosis and Management of Tropomyosin Receptor Kinase Fusion-Positive Thyroid Carcinomas: A Review

IMPORTANCE

Thyroid epithelial malignant neoplasms include differentiated thyroid carcinomas (papillary, follicular, and oncocytic), follicular-derived high-grade thyroid carcinomas, and anaplastic and medullary thyroid carcinomas, with additional rarer subtypes. The discovery of neurotrophic tyrosine receptor kinase (NTRK) gene fusions has fostered developments in precision oncology, with the approval of tropomyosin receptor kinase inhibitors (larotrectinib and entrectinib) for patients with solid tumors, including advanced thyroid carcinomas, harboring NTRK gene fusions.

OBSERVATIONS

The relative rarity and diagnostic complexity of NTRK gene fusion events in thyroid carcinoma present several challenges for clinicians, including variable access to robust methodologies for comprehensive NTRK fusion testing and poorly defined algorithms of when to test for such molecular alterations. To address these issues in thyroid carcinoma, 3 consensus meetings of expert oncologists and pathologists were convened to discuss diagnostic challenges and propose a rational diagnostic algorithm. Per the proposed diagnostic algorithm, NTRK gene fusion testing should be considered as part of the initial workup for patients with unresectable, advanced, or high-risk disease as well as following the development of radioiodine-refractory or metastatic disease; testing by DNA or RNA next-generation sequencing is recommended. Detecting the presence of NTRK gene fusions is important to identify patients eligible to receive tropomyosin receptor kinase inhibitor therapy.

CONCLUSIONS AND RELEVANCE

This review provides practical guidance for optimal integration of gene fusion testing, including NTRK gene fusion testing, to inform the clinical management in patients with thyroid carcinoma.

The peptide woods are lovely, dark and deep: Hunting for novel cancer antigens

Harnessing the patient's immune system to control a tumor is a proven avenue for cancer therapy. T cell therapies as well as therapeutic vaccines, which target specific antigens of interest, are being explored as treatments in conjunction with immune checkpoint blockade. For these therapies, selecting the best suited antigens is crucial. Most of the focus has thus far been on neoantigens that arise from tumor-specific somatic mutations. Although there is clear evidence that T-cell responses against mutated neoantigens are protective, the large majority of these mutations are not immunogenic. In addition, most somatic mutations are unique to each individual patient and their targeting requires the development of individualized approaches. Therefore, novel antigen types are needed to broaden the scope of such treatments. We review high throughput approaches for discovering novel tumor antigens and some of the key challenges associated with their detection, and discuss considerations when selecting tumor antigens to target in the clinic.

GLI1 -Rearranged Enteric Tumor : Expanding the Spectrum of Gastrointestinal Neoplasms With GLI1 Gene Fusions

GLI1 encodes a transcription factor that targets cell cycle regulators affecting stem cell proliferation. GLI1 gene fusions were initially described in pericytomas with a t[7;12] translocation and more recently in gastric plexiform fibromyxomas and gastroblastomas. This study describes the clinicopathologic, immunohistochemical, and molecular features of three intestinal-based neoplasms harboring GLI1 gene fusions. We studied three unique mesenchymal small bowel tumors. Paraffin embedded tumor tissues from these cases and 62 additional tumor samples that included a plexiform fibromyxoma were sequenced using a targeted RNAseq method to detect fusion events. The study patients included two women and one man who were 52, 80, and 22 years of age at the time of diagnosis. The tumors involved the submucosa and muscularis propria of the duodenum, jejunum, and ileum. All 3 tumors contained a proliferation of monotonous oval or spindle cells with scattered, somewhat dilated vessels. Two cases showed epithelioid structures such as glands, tubules, or nests. Immunohistochemical analysis revealed cytokeratin expression in the epithelioid components of both tumors displaying these features, and variable numbers of mesenchymal cells. Diffuse CD56 positivity was seen in the mesenchymal component of 2 tumors and desmin and smooth muscle actin staining in the other tumor. Immunostains for S-100 protein, DOG-1, and CD117 were negative in all cases. GLI1 fusions with different partner genes were detected in all tumors, and in the plexiform fibromyxoma, used as a control. Validation by fluorescence in situ hybridization was performed. None of the tumors have recurred or metastasize after surgery. We describe novel GLI1 fusions in 3 mesenchymal neoplasms of the small intestine, including 2 with biphenotypic features. Thus far, all cases have pursued indolent clinical courses. We propose the term " GLI1 -rearranged enteric tumor" to encompass this group of unique neoplasms of the small intestine that harbor GLI1 gene fusions and expand the spectrum of gastrointestinal neoplasms with these alterations.

Feasibility of a novel non-invasive swab technique for serial whole-exome sequencing of cervical tumors during chemoradiation therapy

Background

Clinically relevant genetic predictors of radiation response for cervical cancer are understudied due to the morbidity of repeat invasive biopsies required to obtain genetic material. Thus, we aimed to demonstrate the feasibility of a novel noninvasive cervical swab technique to (1) collect tumor DNA with adequate throughput to (2) perform whole-exome sequencing (WES) at serial time points over the course of chemoradiation therapy (CRT).

Methods

Cervical cancer tumor samples from patients undergoing chemoradiation were collected at baseline, at week 1, week 3, and at the completion of CRT (week 5) using a noninvasive swab-based biopsy technique. Swab samples were analyzed with whole-exome sequencing (WES) with mutation calling using a custom pipeline optimized for shallow whole-exome sequencing with low tumor purity (TP). Tumor mutation changes over the course of treatment were profiled.

Results

216 samples were collected and successfully sequenced for 70 patients (94% of total number of tumor samples collected). A total of 33 patients had a complete set of samples at all four time points. The mean mapping rate was 98% for all samples, and the mean target coverage was 180. Estimated TP was greater than 5% for all samples. Overall mutation frequency decreased during CRT but mapping rate and mean target coverage remained at >98% and >180 reads at week 5.

Conclusion

This study demonstrates the feasibility and application of a noninvasive swab-based technique for WES analysis which may be applied to investigate dynamic tumor mutational changes during treatment to identify novel genes which confer radiation resistance.

Target Enrichment Approaches for Next-Generation Sequencing Applications in Oncology

Screening for genomic sequence variants in genes of predictive and prognostic significance is an integral part of precision medicine. Next-generation sequencing (NGS) technologies are progressively becoming platforms of choice to facilitate this, owing to their massively parallel sequencing capability, which can be used to simultaneously screen multiple markers in multiple samples for a variety of variants (single nucleotide and multi nucleotide variants, insertions and deletions, gene copy number variations, and fusions). A crucial step in the workflow of targeted NGS is the enrichment of the genomic regions of interest to be sequenced, against the whole genomic background. This ensures that the NGS effort is focused to predominantly screen target regions of interest with minimal off-target sequencing, making it more accurate and economical. Polymerase chain reaction-based (PCR, or amplicon-based) and hybridization capture-based methodologies are the two prominent approaches employed for target enrichment. This review summarizes the basic principles of target enrichment utilized by these methods, their multiple variations that have evolved over time, automation approaches, overall comparison of their advantages and drawbacks, and commercially available choices for these methodologies.

Tumor-immune microenvironment revealed by Imaging Mass Cytometry in a metastatic sarcomatoid urothelial carcinoma with a prolonged response to pembrolizumab

Sarcomatoid urothelial carcinoma (SUC) is a rare subtype of urothelial carcinoma (UC) that typically presents at an advanced stage compared to more common variants of UC. Locally advanced and metastatic UC have a poor long-term survival following progression on first-line platinum-based chemotherapy. Antibodies directed against the programmed cell death 1 protein (PD-1) or its ligand (PD-L1) are now approved to be used in these scenarios. The need for reliable biomarkers for treatment stratification is still under research. Here, we present a novel case report of the first Imaging Mass Cytometry (IMC) analysis done in SUC to investigate the immune cell repertoire and PD-L1 expression in a patient who presented with metastatic SUC and experienced a prolonged response to the anti-PD1 immune checkpoint inhibitor pembrolizumab after progression on first-line chemotherapy. This case report provides an important platform for translating these findings to a larger cohort of UC and UC variants.

RET Fusion-Positive Papillary Thyroid Cancers are Associated with a More Aggressive Phenotype

BACKGROUND

It is unclear if different genetic drivers in papillary thyroid cancer (PTC) confer different phenotypic tumor behavior leading to more aggressive disease. We hypothesized that RET-driven cancers are more aggressive.

PATIENTS AND METHODS

We reviewed records of consecutive patients treated for newly diagnosed PTC at this single institution from 2015 to 2016. Tumor samples from these patients were genotyped to identify RET-translocated, BRAFV600E mutant, and HRAS, KRAS, and NRAS mutant tumors. Patient demographic, clinicopathologic, and outcomes data were compared to identify genotype-specific patterns of disease.

RESULTS

Of the 327 patients who underwent initial surgery for PTC during the study period, 192 (58.7%) had BRAFV600E mutant tumors (BRAF), 14 (4.3%) had RET-rearranged tumors (RET), 46 (14.1%) had RAS mutant tumors (RAS), and 75 (22.9%) had BRAF, RET, and RAS wildtype tumors. RET-driven tumors were more likely to have extrathyroidal extension (50.0% versus 27.0% for BRAF and 2.2% for RAS, P < 0.001), multifocal disease (85.7% versus 60.3%, and 44.4%, respectively, P = 0.017), and distant metastases (14.3% versus 1.1%, and 0%, respectively, P = 0.019). RET and BRAF patients also had worse disease-free survival than RAS patients (Kaplan-Meier log rank, P = 0.027).

CONCLUSIONS

Patients with RET-driven PTCs had higher rates of extrathyroidal extension, multifocal disease, and distant metastases than patients whose tumors had BRAFV600E or RAS mutations. Patients with RET-rearranged tumors had similar disease-free survival to patients with BRAFV600E mutant tumors. RET rearrangement may confer an aggressive phenotype in PTC.

Gene Rearrangement Detection in Pediatric Leukemia

The detection of gene rearrangements in pediatric leukemia is an essential component of the work-up, with implications for accurate diagnosis, proper risk stratification, and therapeutic decisions, including the use of targeted therapies. The traditional methods of karyotype and fluorescence in situ hybridization are still valuable, but many new assays are also available, with different strengths and weaknesses. These assays include next-generation sequencing-based assays that have the potential for highly multiplexed and/or unbiased detection of rearrangements.