With the FDA approval of larotrectinib, NTRK fusion assessment has recently become a standard part of management for patients with locally advanced or metastatic cancers. Unlike somatic mutation ...assessment, the detection of NTRK fusions is not straightforward, and various assays exist at the DNA, RNA, and protein level. Here, we investigate the performance of immunohistochemistry and DNA-based next-generation sequencing to indirectly or directly detect NTRK fusions relative to an RNA-based next-generation sequencing approach in the largest cohort of NTRK fusion positive solid tumors to date. A retrospective analysis of 38,095 samples from 33,997 patients sequenced by a targeted DNA-based next-generation sequencing panel (MSK-IMPACT), 2189 of which were also examined by an RNA-based sequencing assay (MSK-Fusion), identified 87 patients with oncogenic NTRK1-3 fusions. All available institutional NTRK fusion positive cases were assessed by pan-Trk immunohistochemistry along with a cohort of control cases negative for NTRK fusions by next-generation sequencing. DNA-based sequencing showed an overall sensitivity and specificity of 81.1% and 99.9%, respectively, for the detection of NTRK fusions when compared to RNA-based sequencing. False negatives occurred when fusions involved breakpoints not covered by the assay. Immunohistochemistry showed overall sensitivity of 87.9% and specificity of 81.1%, with high sensitivity for NTRK1 (96%) and NTRK2 (100%) fusions and lower sensitivity for NTRK3 fusions (79%). Specificity was 100% for carcinomas of the colon, lung, thyroid, pancreas, and biliary tract. Decreased specificity was seen in breast and salivary gland carcinomas (82% and 52%, respectively), and positive staining was often seen in tumors with neural differentiation. Both sensitivity and specificity were poor in sarcomas. Selection of the appropriate assay for NTRK fusion detection therefore depends on tumor type and genes involved, as well as consideration of other factors such as available material, accessibility of various clinical assays, and whether comprehensive genomic testing is needed concurrently.
Activating neurotrophic tyrosine receptor kinase (NTRK) fusions, typically detected using nucleic-acid based assays, are highly targetable and define certain tumors. Here, we explore the utility of ...pan-TRK immunohistochemistry (IHC) to detect NTRK fusions. NTRK rearrangements were detected prospectively using MSK-IMPACT, a DNA-based next-generation sequencing assay. Transcription of novel NTRK rearrangements into potentially functional fusion transcripts was assessed via Archer Dx fusion assay. Pan-Trk IHC testing with mAb EPR17341 was performed on all NTRK rearranged cases and 20 cases negative for NTRK fusions on Archer. Of 23 cases with NTRK rearrangements, 15 had known activating fusions. Archer detected fusion transcripts in 6 of 8 novel NTRK rearrangements of uncertain functional significance. Pan-Trk IHC was positive in 20 of 21 cases with NTRK fusion transcripts confirmed by Archer. The discordant negative case was a mismatch repair- deficient colorectal carcinoma with an ETV6-NTRK3 fusion. All 20 additional Archer-negative cases had concordant pan-TRK IHC results. Pan-Trk IHC sensitivity and specificity for transcribed NTRK fusions was 95.2% and 100%, respectively. All positive IHC cases had cytoplasmic staining while the following fusion partner-specific patterns were discovered: all 5 LMNA-NTRK1 fusions displayed nuclear membrane accentuation, all 4 TPM3/4 fusions displayed cellular membrane accentuation, and half (3/6) of ETV6-NTRK3 fusions displayed nuclear staining. Pan-Trk IHC is a time-efficient and tissue-efficient screen for NTRK fusions, particularly in driver-negative advanced malignancies and potential cases of secretory carcinoma and congenital fibrosarcoma. Pan-Trk IHC can help determine whether translation occurs for novel NTRK rearrangements.
Recently discovered DNAJB1-PRKACA oncogenic fusions have been considered diagnostic for fibrolamellar hepatocellular carcinoma. In this study, we describe six pancreatobiliary neoplasms with PRKACA ...fusions, five of which harbor the DNAJB1-PRKACA fusion. All neoplasms were subjected to a hybridization capture-based next-generation sequencing assay (MSK-IMPACT), which enables the identification of sequence mutations, copy number alterations, and selected structural rearrangements involving ≥410 genes (n = 6) and/or to a custom targeted, RNA-based panel (MSK-Fusion) that utilizes Archer Anchored Multiplex PCR technology and next-generation sequencing to detect gene fusions in 62 genes (n = 2). Selected neoplasms also underwent FISH analysis, albumin mRNA in-situ hybridization, and arginase-1 immunohistochemical labeling (n = 3). Five neoplasms were pancreatic, and one arose in the intrahepatic bile ducts. All revealed at least focal oncocytic morphology: three cases were diagnosed as intraductal oncocytic papillary neoplasms, and three as intraductal papillary mucinous neoplasms with mixed oncocytic and pancreatobiliary or gastric features. Four cases had an invasive carcinoma component composed of oncocytic cells. Five cases revealed DNAJB1-PRKACA fusions and one revealed an ATP1B1-PRKACA fusion. None of the cases tested were positive for albumin or arginase-1. Our data prove that DNAJB1-PRKACA fusion is neither exclusive nor diagnostic for fibrolamellar hepatocellular carcinoma, and caution should be exercised in diagnosing liver tumors with DNAJB1-PRKACA fusions as fibrolamellar hepatocellular carcinoma, particularly if a pancreatic lesion is present. Moreover, considering DNAJB1-PRKACA fusions lead to upregulated protein kinase activity and that this upregulated protein kinase activity has a significant role in tumorigenesis of fibrolamellar hepatocellular carcinoma, protein kinase inhibition could have therapeutic potential in the treatment of these pancreatobiliary neoplasms as well, once a suitable drug is developed.
Mechanistic understanding of oncogenic variants facilitates the development and optimization of treatment strategies. We recently identified in-frame, tandem duplication of EGFR exons 18 - 25, which ...causes EGFR Kinase Domain Duplication (EGFR-KDD). Here, we characterize the prevalence of ERBB family KDDs across multiple human cancers and evaluate the functional biochemistry of EGFR-KDD as it relates to pathogenesis and potential therapeutic intervention. We provide computational and experimental evidence that EGFR-KDD functions by forming asymmetric EGF-independent intra-molecular and EGF-dependent inter-molecular dimers. Time-resolved fluorescence microscopy and co-immunoprecipitation reveals EGFR-KDD can form ligand-dependent inter-molecular homo- and hetero-dimers/multimers. Furthermore, we show that inhibition of EGFR-KDD activity is maximally achieved by blocking both intra- and inter-molecular dimerization. Collectively, our findings define a previously unrecognized model of EGFR dimerization, providing important insights for the understanding of EGFR activation mechanisms and informing personalized treatment of patients with tumors harboring EGFR-KDD. Finally, we establish ERBB KDDs as recurrent oncogenic events in multiple cancers.
Immunohistochemistry for mismatch repair protein expression is widely used as a surrogate for microsatellite instability status-an important signature for immunotherapy and germline testing. There ...are no systematic analyses examining the sensitivity of immunohistochemistry for microsatellite instability-high status. Mismatch repair immunohistochemistry and microsatellite instability testing were performed routinely as clinically validated assays. We classified germline/somatic mutation types as truncating (nonsense, frameshift, and in/del) versus missense and predicted pathogenicity of the latter. Discordant cases were compared with concordant groups: microsatellite instability-high/mismatch repair-deficient for mutation comparison and microsatellite stable/mismatch repair-proficient for immunohistochemical comparison. 32 of 443 (7%) microsatellite instability-high cases had immunohistochemistry. Four additional microsatellite instability-high research cases had discordant immunohistochemistry. Of 36 microsatellite instability-high cases with discordant immunohistochemistry, 30 were mismatch repair-proficient, while six (five MLH1 and one MSH2) retained expression of the defective mismatch repair protein and lost its partner. In microsatellite instability-high tumors with discordant immunohistochemistry, we observed an enrichment in deleterious missense mutations over truncating mutations, with 69% (25/36) of cases having pathogenic germline or somatic missense mutations, as opposed to only 19% (7/36) in a matched microsatellite instability-high group with concordant immunohistochemistry (p = 0.0007). In microsatellite instability-high cases with discordant immunohistochemistry and MLH1 or PMS2 abnormalities, less cells showed expression (p = 0.015 and p = 0.00095, respectively) compared with microsatellite stable/mismatch repair-proficient cases. Tumor mutation burden, MSIsensor score, and truncating mismatch repair gene mutations were similar between microsatellite instability-high cases with concordant versus discordant immunohistochemical expression. Approximately 6% of microsatellite instability-high cases have retained mismatch repair protein expression and would be missed by immunohistochemistry-based testing, hindering patient access to immunotherapy. Another 1% of microsatellite instability-high cases show isolated loss of the defective gene's dimerization partner, which may lead to germline testing of the wrong gene. These cases are enriched for pathogenic mismatch repair missense mutations.
Most mutations in cancer are rare, which complicates the identification of therapeutically significant mutations and thus limits the clinical impact of genomic profiling in patients with cancer. ...Here, we analyzed 24,592 cancers including 10,336 prospectively sequenced patients with advanced disease to identify mutant residues arising more frequently than expected in the absence of selection. We identified 1,165 statistically significant hotspot mutations of which 80% arose in 1 in 1,000 or fewer patients. Of 55 recurrent in-frame indels, we validated that novel
duplications induced pathway hyperactivation and conferred AKT inhibitor sensitivity. Cancer genes exhibit different rates of hotspot discovery with increasing sample size, with few approaching saturation. Consequently, 26% of all hotspots in therapeutically actionable oncogenes were novel. Upon matching a subset of affected patients directly to molecularly targeted therapy, we observed radiographic and clinical responses. Population-scale mutant allele discovery illustrates how the identification of driver mutations in cancer is far from complete.
Our systematic computational, experimental, and clinical analysis of hotspot mutations in approximately 25,000 human cancers demonstrates that the long right tail of biologically and therapeutically significant mutant alleles is still incompletely characterized. Sharing prospective genomic data will accelerate hotspot identification, thereby expanding the reach of precision oncology in patients with cancer.
.
Undifferentiated uterine sarcoma is a diagnosis of exclusion with limited molecular genetic data available. Recent recognition of high-grade endometrial stromal sarcomas with diverse genotypes ...suggests that some tumors classified as undifferentiated uterine sarcomas may represent misdiagnosed high-grade endometrial stromal sarcomas. Archival material from 10 tumors diagnosed as undifferentiated uterine sarcomas in 2009 to 2017 were collected. BCOR immunohistochemistry and fluorescence in situ hybridization (FISH) using break-apart probes flanking BCOR, ZC3H7B, CCNB3, YWHAE, NUTM2, JAZF1, and BCORL1 were performed. Tumors lacking or harboring gene rearrangement with no known fusion partner by FISH were subjected to targeted RNA sequencing. Morphology was correlated with FISH and sequencing results. BCOR expression was moderate to strong in ≥50% of cells in 8 tumors, while weak in <5% cells and negative in 2. FISH detected mutually exclusive ZC3H7B-BCOR and YWHAE-NUTM2 fusions in 3 uniform undifferentiated uterine sarcomas; 2 pleomorphic tumors harbored YWHAE rearrangement with no known partner. Targeted RNA sequencing of 5 FISH-negative uniform undifferentiated uterine sarcomas detected BRD8-PHF1 and YWHAE-NUTM2B fusions and BCOR internal tandem duplication in 4 of them. Tumors with YWHAE-NUTM2 fusions and BCOR genetic abnormalities showed morphology characteristic of high-grade endometrial stromal sarcomas. No fusions were detected by sequencing in the tumor with YWHAE rearrangement only by FISH. Most tumors classified as undifferentiated uterine sarcomas represent misdiagnosed high-grade endometrial stromal sarcomas. BCOR expression in ≥50% of cells may help triage tumors for molecular confirmation of high-grade endometrial stromal sarcoma-related genetic abnormalities. Novel YWHAE rearrangements may define a subset of true undifferentiated pleomorphic sarcomas.
Selpercatinib and pralsetinib induce deep and durable responses in patients with advanced
fusion-positive lung and thyroid cancer.
fusion testing strategies with rapid and reliable results are ...critical given recent FDA approval. Here, we assess various clinical assays in a large pan-cancer cohort.
Tumors underwent DNA-based next-generation sequencing (NGS) with reflex to RNA-based NGS if no mitogenic driver or if a
structural variant of unknown significance (SVUS) were present. Canonical DNA-level
fusions and RNA-confirmed
fusions were considered true fusions. Break-apart FISH and IHC performance were assessed in subgroups.
A total of 171 of 41,869 patients with DNA NGS harbored
structural variants, including 139 canonical fusions and 32 SVUS. Twelve of 32 (37.5%) SVUS were transcribed into RNA-level fusions, resulting in 151 oncogenic
fusions. The most common
fusion-positive tumor types were lung (65.6%) and thyroid (23.2%). The most common partners were
(45%),
(29.1%), and
(13.3%). DNA NGS showed 100% (46/46) sensitivity and 99.6% (4,459/4,479) specificity. FISH showed 91.7% (44/48) sensitivity, with lower sensitivity for
-
(66.7%, 8/12). A total of 87.5% (7/8) of
SVUS negative for RNA-level fusions demonstrated rearrangement by FISH. The sensitivity of IHC varied by fusion partner:
sensitivity was highest (100%, 31/31), followed by
(88.9%, 16/18) and
(50%, 6/12). Specificity of RET IHC was 82% (73/89).
Although DNA sequencing has high sensitivity and specificity, RNA sequencing of
SVUS is necessary. Both FISH and IHC demonstrated lower sensitivity for
-
fusions.
Half of inflammatory myofibroblastic tumors (IMTs) regardless of anatomic location harbor anaplastic lymphoma kinase gene (ALK) rearrangements and overexpress anaplastic lymphoma kinase protein. The ...wide application of next-generation sequencing and the clinical benefit to tyrosine kinase inhibitors have opened new opportunities for investigation of ALK-negative IMTs.
In this study, we have investigated a series of pediatric and adult thoracic IMTs for abnormalities in a wide spectrum of actionable kinases by applying a variety of molecular and next-generation sequencing techniques, including fluorescence in situ hybridization (FISH), targeted RNA sequencing, and NanoString assay.
There were 33 patients with thoracic IMTs, including five children; their mean age was 37. The tumors showed a monomorphic spindle cell phenotype, except for one with an epithelioid morphologic pattern and moderate to severe atypia. By immunohistochemistry, 24 tumors were ALK positive, and 19 of the 24 showed ALK rearrangements and one ret proto-oncogene gene (RET) rearrangement by FISH. RNA sequencing was performed in the remaining four cases lacking ALK abnormalities by FISH, revealing ALK fusions involving tropomyosin 4 gene (TMP4) and echinoderm microtubule associated protein like 4 gene (EML4) as partner in three cases. NanoString assay was performed in the remaining case, revealing ALK alternative transcription initiation (ALKATI). Nine cases lacking ALK abnormalities were further tested by FISH or targeted RNA sequencing, revealing ROS1 rearrangement in six cases and ETS variant 6 gene (ETV6)–neurotrophic receptor tyrosine kinase 3 gene (NTRK3) fusion in three cases, respectively.
By using a battery of complementary molecular techniques, we have shown that all the thoracic IMTs harbored a tyrosine kinase abnormality, with 30% involving a kinase gene other than ALK, including ROS1, NTRK3, and RET gene fusions. We have also described for the first time ALKATI-induced ALK oncogenic activation in IMTs.
High-grade histologic transformation of low-grade endometrial stromal sarcoma (LGESS) is rare. Here, we describe the clinicopathologic features and gene fusion status of 12 cases (11 primary uterine ...corpus and 1 primary vaginal), 11 diagnosed prospectively from 2016, and 1 retrospectively collected. Targeted RNA sequencing and/or fluorescence in situ hybridization was employed in all cases. High-grade transformation was seen at the time of initial diagnosis in eight patients and at the time of recurrence in four patients, 4–11 years after initial diagnosis of LGESS. High-grade morphology consisted of generally uniform population of round to epithelioid cells with enlarged nuclei one to two times larger than a lymphocyte, visible nucleoli, and increased mitotic index (range, 6–30; median, 16 per 10 high-power fields); there was often an associated sclerotic and/or myxoid stroma. Estrogen receptor, progesterone receptor, and CD10 expression was absent or significantly decreased (compared with the low-grade component) in the high-grade foci of five tumors. One tumor demonstrated positive (diffuse and strong) cyclin D1 and BCOR staining. p53 staining was wild type in both components of all eight tumors tested. JAZF1-SUZ12 (n = 6), JAZF1-PHF1 (n = 3), EPC1-PHF1, (n = 1), or BRD8-PHF1 (n = 1) fusions were detected in 11 tumors; no fusions were found in one by targeted RNA sequencing. Patients presented with FIGO stages I (n = 4), II (n = 4), III (n = 1), and IV disease (n = 2). Median overall survival calculated from the time of histologic transformation was 22 months (range, 8 months to 8 years) with five patients who died of disease 8–18 months after transformation. High-grade transformation may occur in LGESS with JAZF1 and PHF1 rearrangements at the time of or years after initial diagnosis. Such high-grade transformation is characterized by nuclear enlargement, prominent nucleoli, and increased mitotic index compared with typical LGESS. Histologic high-grade transformation may herald aggressive behavior.
PDF
