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Since the discovery of an oncogenic tropomyosin-receptor kinase (TRK) fusion protein in the early 1980s, our understanding of neurotrophic tropomyosin-receptor kinase (NTRK) fusions, their unique patterns of frequency in different tumor types, and methods to detect them have grown in scope and depth. Identification of these molecular alterations in the management of patients with cancer has become increasingly important with the emergence of histology-agnostic, US Food and Drug Administration-approved, effective TRK protein inhibitors. Herein, we review the biology of TRK in normal and malignant tissues, as well as the prevalence and enrichment patterns of these fusions across tumor types. Testing methods currently used to identify NTRK1-3 fusions will be reviewed in detail, with attention to newer assays including RNA-based next-generation sequencing. Recently proposed algorithms for NTRK fusion testing will be compared, and practical insights provided on how testing can best be implemented and communicated within the multidisciplinary healthcare team.

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The incidence of esophagogastric cancer is rapidly rising, but only a minority of patients derive durable benefit from current therapies. Chemotherapy as well as anti-HER2 and PD-1 antibodies are standard treatments. To identify predictive biomarkers of drug sensitivity and mechanisms of resistance, we implemented prospective tumor sequencing of patients with metastatic esophagogastric cancer. There was no association between homologous recombination deficiency defects and response to platinum-based chemotherapy. Patients with microsatellite instability–high tumors were intrinsically resistant to chemotherapy but more likely to achieve durable responses to immunotherapy. The single Epstein–Barr virus–positive patient achieved a durable, complete response to immunotherapy. The level of ERBB2 amplification as determined by sequencing was predictive of trastuzumab benefit. Selection for a tumor subclone lacking ERBB2 amplification, deletion of ERBB2 exon 16, and comutations in the receptor tyrosine kinase, RAS, and PI3K pathways were associated with intrinsic and/or acquired trastuzumab resistance. Prospective genomic profiling can identify patients most likely to derive durable benefit to immunotherapy and trastuzumab and guide strategies to overcome drug resistance.Significance: Clinical application of multiplex sequencing can identify biomarkers of treatment response to contemporary systemic therapies in metastatic esophagogastric cancer. This large prospective analysis sheds light on the biological complexity and the dynamic nature of therapeutic resistance in metastatic esophagogastric cancers. Cancer Discov; 8(1); 49–58. ©2017 AACR.See related commentary by Sundar and Tan, p. 14.See related article by Pectasides et al., p. 37.This article is highlighted in the In This Issue feature, p. 1

Concordance between copy-number inferred from next generation sequencing and protein overexpression by IHC or gene amplification by FISH.

Supplementary Methods Supplementary References Supplementary Figure 1. Effect of acquired resistance mutations on TRK inhibitor activity. Supplementary Figure 2. Further characterization of LOXO-195 inhibitory activity against acquired resistance mutations. Supplementary Figure 3. LOXO-195 is selectively cytotoxic to TRK-fusion cell lines. Supplementary Figure 4. Identification of a clonal NTRK1 (TRKA)-G595R mutation after larotrectinib treatment. Supplementary Table 1. LOXO-195 ADME properties. Supplementary Table 2. Selectivity of LOXO-195 for 228 kinases. Supplementary Table 3. Summary of LOXO-195 PK parameters for each patient during intra-patient dose escalation.

Additional results for dual probe EGFR and ERBB2 FISH from Patients 9, 30 and 32.

Summary of organoid genotypes and WNT resistance status

Supplemental Tables

On-target resistance to next-generation TRK inhibitors in TRK fusion–positive cancers is largely uncharacterized. In patients with these tumors, we found that TRK xDFG mutations confer resistance to type I next-generation TRK inhibitors designed to maintain potency against several kinase domain mutations. Computational modeling and biochemical assays showed that TRKAG667 and TRKCG696 xDFG substitutions reduce drug binding by generating steric hindrance. Concurrently, these mutations stabilize the inactive (DFG-out) conformations of the kinases, thus sensitizing these kinases to type II TRK inhibitors. Consistently, type II inhibitors impede the growth and TRK-mediated signaling of xDFG-mutant isogenic and patient-derived models. Collectively, these data demonstrate that adaptive conformational resistance can be abrogated by shifting kinase engagement modes. Given the prior identification of paralogous xDFG resistance mutations in other oncogene-addicted cancers, these findings provide insights into rational type II drug design by leveraging inhibitor class affinity switching to address recalcitrant resistant alterations.Significance:In TRK fusion–positive cancers, TRK xDFG substitutions represent a shared liability for type I TRK inhibitors. In contrast, they represent a potential biomarker of type II TRK inhibitor activity. As all currently available type II agents are multikinase inhibitors, rational drug design should focus on selective type II inhibitor creation.This article is highlighted in the In This Issue feature, p. 1

Detected RTK alterations and MAP2K1 mutations in sequenced colorectal carcinomas.

(a) Barplot of GISTIC2.0 chromosome 20q gene level copy number calls in TCGA COADREAD data and (b) chromosome 20q genes covered by MSK-IMPACT. (c) Interquartile range (IGR) of gene level RNASeq expression z-score by copy number group from 2a. (d) MSK-IMPACT and TCGA tumor purity estimates.

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(a) Plot of SCNA in a CRC with 20q amplification as detected by MSK-IMPACT and (b) high resolution SNP analysis on Oncoscan confirmed the results without showing focal amplifications

Text legends for Supplementary Figures S1-S4.

The WNT pathway is a fundamental regulator of intestinal homeostasis, and hyperactivation of WNT signaling is the major oncogenic driver in colorectal cancer. To date, there are no described mechanisms that bypass WNT dependence in intestinal tumors. Here, we show that although WNT suppression blocks tumor growth in most organoid and in vivo colorectal cancer models, the accumulation of colorectal cancer–associated genetic alterations enables drug resistance and WNT-independent growth. In intestinal epithelial cells harboring mutations in KRAS or BRAF, together with disruption of TP53 and SMAD4, transient TGFβ exposure drives YAP/TAZ-dependent transcriptional reprogramming and lineage reversion. Acquisition of embryonic intestinal identity is accompanied by a permanent loss of adult intestinal lineages, and long-term WNT-independent growth. This work identifies genetic and microenvironmental factors that drive WNT inhibitor resistance, defines a new mechanism for WNT-independent colorectal cancer growth, and reveals how integration of associated genetic alterations and extracellular signals can overcome lineage-dependent oncogenic programs.Significance:Colorectal and intestinal cancers are driven by mutations in the WNT pathway, and drugs aimed at suppressing WNT signaling are in active clinical development. Our study identifies a mechanism of acquired resistance to WNT inhibition and highlights a potential strategy to target those drug-resistant cells.This article is highlighted in the In This Issue feature, p. 1426

Here, comprehensive analysis was performed on the molecular and clinical features of colorectal carcinoma harboring chromosome 20q amplification. Tumor and normal DNA from patients with advanced colorectal carcinoma underwent next-generation sequencing via MSK-IMPACT, and a subset of case samples was subjected to high-resolution microarray (Oncoscan). Relationships between genomic copy number and transcript expression were assessed with The Cancer Genome Atlas (TCGA) colorectal carcinoma data. Of the colorectal carcinoma patients sequenced (n = 401) with MSK-IMPACT, 148 (37%) had 20q gain, and 30 (7%) had 20q amplification. In both the MSK-IMPACT and TCGA datasets, BCL2L1 was the most frequently amplified 20q oncogene. However, SRC was the only recognized 20q oncogene with a significant inverse relationship between mRNA upregulation and RAS/RAF mutation (OR, −0.4 ± 0.2, P = 0.02). In comparison with 20q diploid colorectal carcinoma, 20q gain/amplification was associated with wild-type KRAS (P < 0.001) and BRAF (P = 0.01), microsatellite stability (P < 0.001), distal primary tumors (P < 0.001), and mutant TP53 (P < 0.001), but not stage. On multivariate analysis, longer overall survival from the date of metastasis was observed with chromosome 20q gain (P = 0.02) or amplification (P = 0.04) compared with diploid 20q.Implications: 20q amplification defines a subset of colorectal cancer patients with better overall survival from the date of metastasis, and further studies are warranted to assess whether the inhibition of 20q oncogenes, such as SRC, may benefit this subset of patients. Mol Cancer Res; 15(6); 708–13. ©2017 AACR.

Supplementary Table 1: Comprehensive clinical data and sample IDs. Supplementary Table 2: Summary of baseline patient and sample characteristics. Supplementary Table 3: List of somatic mutations identified in all samples. Supplementary Table 4: Detailed data for assesment of ERBB2 amplification. Supplementary Table 5: Genes included on MSK-IMPACT platform

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Supplementary Tables

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supplementary tables, figures, and methods

We report the emergence of the novel MEK1V211D gatekeeper mutation in a patient with BRAFK601E colon cancer treated with the allosteric MEK inhibitor binimetinib and the anti-EGFR antibody panitumumab. The MEK1V211D mutation concurrently occurs in the same cell with BRAFK601E and leads to RAF-independent activity but remains regulated by RAF. The V211D mutation causes resistance to binimetinib by both increasing the catalytic activity of MEK1 and reducing its affinity for the drug. Moreover, the mutant exhibits reduced sensitivity to all the allosteric MEK inhibitors tested. Thus, this mutation serves as a general resistance mutation for current MEK inhibitors; however, it is sensitive to a newly reported ATP-competitive MEK inhibitor, which therefore could be used to overcome drug resistance.Significance:We report a resistance mechanism to allosteric MEK inhibitors in the clinic. A MEK1V211D mutation developed in a patient with BRAFK601E colon cancer on MEK and EGFR inhibitors. This mutant increases the catalytic activity of MEK1 and reduces its affinity for binimetinib, but remains sensitive to ATP-competitive MEK inhibitors.This article is highlighted in the In This Issue feature, p. 1143

Comparison of the sensitivity and specificity of different screening strategies to identify patients with UTUC related to a Lynch syndrome.

Supplemental Table 1: Clinical Characteristics, Treatment, and Recurrence Rates of of Patients with Stage II SBA Supplemental Table 2. Germline variants among SBA patients

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Outcomes to treatment based on genomic mutation

Purpose:Prior molecular profiling of hepatocellular carcinoma (HCC) has identified actionable findings that may have a role in guiding therapeutic decision-making and clinical trial enrollment. We implemented prospective next-generation sequencing (NGS) in the clinic to determine whether such analyses provide predictive and/or prognostic information for HCC patients treated with contemporary systemic therapies.Experimental Design:Matched tumor/normal DNA from patients with HCC (N = 127) were analyzed using a hybridization capture–based NGS assay designed to target 341 or more cancer-associated genes. Demographic and treatment data were prospectively collected with the goal of correlating treatment outcomes and drug response with molecular profiles.Results:WNT/β-catenin pathway (45%) and TP53 (33%) alterations were frequent and represented mutually exclusive molecular subsets. In sorafenib-treated patients (n = 81), oncogenic PI3K–mTOR pathway alterations were associated with lower disease control rates (DCR, 8.3% vs. 40.2%), shorter median progression-free survival (PFS; 1.9 vs. 5.3 months), and shorter median overall survival (OS; 10.4 vs. 17.9 months). For patients treated with immune checkpoint inhibitors (n = 31), activating alteration WNT/β-catenin signaling were associated with lower DCR (0% vs. 53%), shorter median PFS (2.0 vs. 7.4 months), and shorter median OS (9.1 vs. 15.2 months). Twenty-four percent of patients harbored potentially actionable alterations including TSC1/2 (8.5%) inactivating/truncating mutations, FGF19 (6.3%) and MET (1.5%) amplifications, and IDH1 missense mutations (Conclusions:Linking NGS to routine clinical care has the potential to identify those patients with HCC likely to benefit from standard systemic therapies and can be used in an investigational context to match patients to genome-directed targeted therapies.See related commentary by Pinyol et al., p. 2021

Sensitivity of CD74-ROS1D2033N to a spectrum of ROS1 kinase inhibitors. Cell growth and viability of Ba/F3 cells expressing native CD74-ROS1 or CD74-ROS1D2033N after 72 h exposure to (A) foretinib, (B) PF-06463922, (C) ceritinib, and (D) brigatinib. Results are shown as mean viability normalized to vehicle-treated control {plus minus} SEM (n = 3 to 6). (E) Table listing inhibitor IC50 (nM) for native versus ROS1D2033N mutant. (F) Graph depicts fold increase in IC50 (nM) for Ba/F3 cells expressing CD74-ROS1D2033N compared to native CD74-ROS1.

Supplementary Figure Legends and Supplementary Tables. Supplementary Table S1. Detailed clinical and diagnostic summary for a patient with ROS1-rearranged lung adenocarcinoma who developed acquired resistance to crizotinib and responded to cabozantinib. Supplementary Table S2. Next-generation sequencing results reveal a novel acquired ROS1 D2033N mutation in the CD74-ROS1 kinase domain.

Supplementary Methods for FISH and immunohistochemistry.

Purpose: NRAS mutations are now routinely included in RAS testing prior to EGFR inhibitor therapy for metastatic colorectal cancer (mCRC). The clinical implications of NRAS mutation beyond lack of response to anti-EGFR therapy, however, are not known. We undertook this study to determine the clinical features and treatment outcomes of patients with NRAS-mutant mCRC.Experimental Design: We reviewed clinical characteristics, concurrent mutations, and outcomes for all mCRC cases with NRAS mutations undergoing standard genotyping at our institution from 2008 to 2015. Comparison groups consisted of RAS wild-type and KRAS-mutant mCRC consecutive cases genotyped from 2008 to 2012.Results: Three percent (87/2764) of mCRC patients had NRAS-mutant tumors (45% exon 2 and 55% exon 3), including three cases with concurrent NRAS and KRAS mutations. Left-sided primary site and African American self-reported race were associated with NRAS mutation (P < 0.01). Resection rate at 12 months was lower for NRAS-mutant mCRC than for RAS wild-type or KRAS-mutant mCRC. Median survival from time of first known metastasis was 33 months for NRAS-mutant, 47 months for KRAS-mutant, and 78 months for RAS wild-type cases (P < 0.001). Multivariate analysis assigned an HR for overall survival of 2.0 for NRAS mutation and 1.5 for KRAS mutation (P < 0.01).Conclusions: NRAS defines a molecular subset with distinct clinical characteristics from KRAS-mutant and wild-type mCRC. NRAS mutations are enriched in left-sided primary tumors and among African Americans. Mutations in NRAS are associated with poor survival and worse outcomes than either KRAS-mutant or wild-type mCRC. Clin Cancer Res; 23(16); 4753–60. ©2017 AACR.

Supplemental Table 4. Patient level detail of use of immunotherapy in this cohort.

Molecular predictors of progression free survival in patients treated with cytotoxic chemotherapy

Overall survival from diagnosis with advanced disease by KRAS, ERBB2 and CDKN2A/B status

Oncoprints and Venn diagrams for matched-pair comparisons between UCB and UTUC samples in patients with a history of a prior bladder tumor before resection of the UTUC. The arrows show the time between sample collection in months.

MSK IMPACT Gene Panels

Supplemental Figure 1: Distribution of tumor mutation burden (TMB) across different tumor types, comparing TMB in this HCC cohort (N=127) to the most common other tumor types in the MSK-IMPACT clinical sequencing cohort. The mutation rate was plotted as in (Zehir et al. Nat Med 2017).47

Supplemental Figure 3. Comparison of Tumor Types in Larotrectinib Study Population and MSK Cohort.

BRAF V600E colorectal cancers are insensitive to RAF inhibitor monotherapy due to feedback reactivation of receptor tyrosine kinase signaling. Combined RAF and EGFR inhibition exerts a therapeutic effect, but resistance invariably develops through undefined mechanisms. In this study, we determined that colorectal cancer progression specimens invariably harbored lesions in elements of the RAS–RAF–MEK–ERK pathway. Genetic amplification of wild-type RAS was a recurrent mechanism of resistance in colorectal cancer patients that was not seen in similarly resistant melanomas. We show that wild-type RAS amplification increases receptor tyrosine kinase-dependent activation of RAS more potently in colorectal cancer than in melanoma and causes resistance only in the former. Currently approved RAF inhibitors inhibit RAF monomers but not dimers. All the drug-resistant lesions we identified activate BRAF V600E dimerization directly or by elevating RAS-GTP. Overall, our results show that mechanisms of resistance converge on formation of RAF dimers and that inhibiting EGFR and RAF dimers can effectively suppress ERK-driven growth of resistant colorectal cancer. Cancer Res; 77(23); 6513–23. ©2017 AACR.

Purpose:The RET proto-oncogene encodes a receptor tyrosine kinase that is activated by gene fusion in 1%–2% of non–small cell lung cancers (NSCLC) and rarely in other cancer types. Selpercatinib is a highly selective RET kinase inhibitor that has recently been approved by the FDA in lung and thyroid cancers with activating RET gene fusions and mutations. Molecular mechanisms of acquired resistance to selpercatinib are poorly understood.Patients and Methods:We studied patients treated on the first-in-human clinical trial of selpercatinib (NCT03157129) who were found to have MET amplification associated with resistance to selpercatinib. We validated MET activation as a targetable mediator of resistance to RET-directed therapy, and combined selpercatinib with the MET/ALK/ROS1 inhibitor crizotinib in a series of single patient protocols (SPP).Results:MET amplification was identified in posttreatment biopsies in 4 patients with RET fusion–positive NSCLC treated with selpercatinib. In at least one case, MET amplification was clearly evident prior to therapy with selpercatinib. We demonstrate that increased MET expression in RET fusion–positive tumor cells causes resistance to selpercatinib, and this can be overcome by combining selpercatinib with crizotinib. Using SPPs, selpercatinib with crizotinib were given together generating anecdotal evidence of clinical activity and tolerability, with one response lasting 10 months.Conclusions:Through the use of SPPs, we were able to offer combination therapy targeting MET-amplified resistance identified on the first-in-human study of selpercatinib. These data suggest that MET dependence is a recurring and potentially targetable mechanism of resistance to selective RET inhibition in advanced NSCLC.

Supplementary Methods

Supplementary Figures 1-5: Supplementary Figure 1 - validation and characterization of acquired genomic alterations, Supplementary Figure 2 - RAS amplification leads to increased RAS-GTP and dimerization of RAF, Supplementary Figure 3 - Increase in NRAS expression is sufficient to cause resistance to RAF/EGFR inhibition in vitro in CRC, Supplementary Figure 4 - Increase in NRAS expression does not cause resistance to RAF inhibition in melanoma, Supplementary Figure 5 - Combined EGFR and RAF dimer inhibitors lead to better inhibition of signaling and tumor growth than RAF dimer inhibitor alone in BRAF V600E CRC.

Supplementary Figure 1: (A) RET SVUS that did not express RET fusion transcripts on RNA sequencing (group D cases). (B) Location of KIF5B (NM_004521), RET (NM_020975), NCOA4 (NM_001145260), and CCDC6 (NM_005436) in relation to the break-apart FISH probes on chromosome 10. Red (5') and green (3') probes for FISH are provided. The distance between KIF5B and RET is approximately 11.2 Mb, whereas the distance between NCOA4 and RET is approximately 7.9 Mb.

Supplementary Figure 1: (A) RET SVUS that did not express RET fusion transcripts on RNA sequencing (group D cases). (B) Location of KIF5B (NM_004521), RET (NM_020975), NCOA4 (NM_001145260), and CCDC6 (NM_005436) in relation to the break-apart FISH probes on chromosome 10. Red (5') and green (3') probes for FISH are provided. The distance between KIF5B and RET is approximately 11.2 Mb, whereas the distance between NCOA4 and RET is approximately 7.9 Mb.