RET splice site variants in medullary thyroid carcinoma.

Introduction: Medullary thyroid carcinoma (MTC) is an aggressive cancer that is often caused by driver mutations in RET. Splice site variants (SSV) reflect changes in mRNA processing, which may alter protein function. RET SSVs have been described in thyroid tumors in general but have not been extensively studied in MTC. Methods: The prevalence of RET SSVs was evaluated in 3,624 cases with next generation sequence reports, including 25 MTCs. Fisher exact analysis was performed to compare RET SSV frequency in cancers with/without a diagnosis of MTC. Results: All 25 MTCs had at least one of the two most common RET SSVs versus 0.3% of 3,599 cancers with other diagnoses (p < 0.00001). The 11 cancers with non-MTC diagnoses that had the common RET SSVs were 4 neuroendocrine cancers, 4 non-small cell lung carcinomas, 2 non-MTC thyroid cancers, and 1 melanoma. All 25 MTCs analyzed had at least one of the two most common RET SSVs, including 4 with no identified mutational driver. Discussion: The identification of RET SSVs in all MTCs, but rarely in other cancer types, demonstrates that these RET SSVs distinguish MTCs from other cancer types. Future studies are needed to investigate whether these RET SSVs play a pathogenic role in MTC.

Utility of UV Signature Mutations in the Diagnostic Assessment of Metastatic Head and Neck Carcinomas of Unknown Primary.

BACKGROUND: Metastatic carcinoma of unknown primary origin to the head and neck lymph nodes (HNCUP) engenders unique diagnostic considerations. In many cases, the detection of a high-risk human papillomavirus (HR-HPV) unearths an occult oropharyngeal squamous cell carcinoma (SCC). In metastatic HR-HPV-independent carcinomas, other primary sites should be considered, including cutaneous malignancies that can mimic HR-HPV-associated SCC. In this context, ultraviolet (UV) signature mutations, defined as ≥ 60% C→T substitutions with ≥ 5% CC→TT substitutions at dipyrimidine sites, identified in tumors arising on sun exposed areas, are an attractive and underused tool in the setting of metastatic HNCUP. METHODS: A retrospective review of institutional records focused on cases of HR-HPV negative HNCUP was conducted. All cases were subjected to next generation sequencing analysis to assess UV signature mutations. RESULTS: We identified 14 HR-HPV negative metastatic HNCUP to either the cervical or parotid gland lymph nodes, of which, 11 (11/14, 79%) had UV signature mutations, including 4 (4/10, 40%) p16 positive cases. All UV signature mutation positive cases had at least one significant TP53 mutation and greater than 20 unique gene mutations. CONCLUSION: The management of metastatic cutaneous carcinomas significantly differs from other HNCUP especially metastatic HR-HPV-associated SCC; therefore, the observation of a high percentage of C→T with CC →TT substitutions should be routinely incorporated in next generation sequencing reports of HNCUP. UV mutational signatures testing is a robust diagnostic tool that can be utilized in daily clinical practice.

p21 Protein Outperforms Clinico-pathological Criteria in Predicting Liver Metastases in Pancreatic Endocrine Tumors.

BACKGROUND/AIM: P21 is a cyclin-dependent kinase inhibitor regulating the cell cycle as a tumor suppressor. Using a p21 immunohistochemistry (IHC) assay, we compared tumor p21 levels with conventional clinico-pathological criteria in primary pancreatic endocrine tumor subsets with and without liver metastases. MATERIALS AND METHODS: Sections from tissue microarray (TMA) including 13 archival metastatic primary and 18 non-metastatic primary pancreatic endocrine carcinomas/tumors (MP-PECAs/NMP-PETs) were stained with a monoclonal anti-p21WAFI,CIP primary antibody. Tumor p21 IHCs were scored as the sum of intensity (0-3) and proportion scores (0-5) (Total Allred score: 0-8), and as p21% labelling index in the tumor. ROC curve analysis was used for most optimal p21 score cut-off (4 or >) and Fisher's exact test was used to compare the association among tumor p21 scores, conventional prognostic criteria, and liver metastases. RESULTS: For PET/PECA patients, mean ages were 55.6 years (27-73) and 49.3 years (28-71), M/F ratios were 7/11 and 7/6. Mean p21 labelling index (%) for MP- PECAs was 24% (range=3-63%) vs. 9% for NMP-PETs (range=1-25%) (p=0.022). The mean p21 index in MP-PECAs was significantly higher (24%) as compared to PIs (7%) (p=0.0047). Using a p21 Allred score of ≥4, high p21 IHC score had strong association with the presence of liver metastases (p-value <0.001). High tumor p21 IHC score had a 93% sensitivity, 68% specificity, 78% predictive accuracy, 66% positive, and 94% negative predictive values. CONCLUSION: In patients with primary PETs, p21 IHC is superior to conventional criteria in predicting presence or absence of liver metastases.

Expression of DNA Mismatch Repair Proteins, PD1 and PDL1 in Barrett's Neoplasia.

BACKGROUND/AIM: Cancers with a microsatellite instability-high (MSI-H) or deficient mismatch repair (dMMR) status respond to immune checkpoint inhibition (ICI). Regardless of the tumor type, MSI-H/dMMR status is a reliable biomarker for ICI responsiveness. This study aimed at determining the MSI-H status in precursor lesions to esophageal adenocarcinoma (EAC) such as Barrett's esophagus (BE) and BE with either low-grade dysplasia (LGD) or high-grade dysplasia (HGD). PATIENTS AND METHODS: We performed immunohistochemical staining (IHC) for PMS2, MSH6, PD1, and PD-L1. RESULTS: All cases of BE (50), LGD (48), and HGD (50) had intact PMS2 and MSH6 nuclear expression; were negative for PD1; and had a PD-L1 combined positive score (CPS) score <1. One EAC case (2%) was negative for PMS2 nuclear expression. One HGD case (2%) and two EAC cases (4%) were PD1 positive (CPS score <1 applied to PD1). One EAC case (2%) had a CPS score >1, and one EAC case (2%) was MSI-H. MSI-H tumors usually show PD-L1 expression, although the MSI-H EAC in this study had a PD-L1 CPS score of <1. CONCLUSION: Further studies investigating EAC and its precursor lesions for PD1, PD-L1, and dMMR status may be informative regarding the immunogenicity of the evolution of EAC.

Benefit of Gene Expression Profiling in Gastrointestinal Neuroendocrine Tumors of Unknown Primary Origin.

BACKGROUND/AIM: Cancer of unknown primary (CUP), representing 3-5% of all newly diagnosed cancers in the United States, is a presumptive, non-definitive diagnosis rendered when a primary tumor site cannot be identified after exhaustive diagnostic evaluation, including cases of neuroendocrine neoplasms (NENs). CUPs are characterized by findings that are challenging to reconcile, including inconclusive immunohistochemical (IHC) stains, an undifferentiated morphologic phenotype, history of multiple cancers, a clinical presentation that is discordant from histologic findings, an atypical distribution of metastases, or lack of expected response to treatment. For a significant subset of NENs (10%), traditional diagnostic evaluation is unable to determine a primary tumor site using histomorphology and IHC stains. Gene expression profiling (GEP) of either mRNA or microRNA is the technique utilized in the three commercially available platforms that provide a prediction of tumor type in cases of diagnostic uncertainty of CUPs, including those with neuroendocrine differentiation. Case Series Report: Here we present four cases of NENs, where the diagnosis based upon histomorphological and IHC features presented a unique challenge that ultimately benefited from the integration of molecular tumor classification using the validated assay. CancerTYPE ID by Biotheranostics is based on a quantitative RT-PCR assay that uses a computational algorithm to measure the collective expression of 92 genes (87 cancer-related genes and 5 control genes). This case series reports five appropriate clinical scenarios that highlight the utility of a GEP-based assay to effectively provide a molecular tumor classification to identify NEN subtypes and tumor primary site of origin. CONCLUSION: These cases demonstrated that the CancerTYPE ID test was able to resolve challenging diagnoses for primary and metastatic NENs. These cases emphasize the clinical need of utilizing a GEP-based assay for determining the anatomic site of origin and NEN subtyping, both essential for the appropriate clinical management of NENs.

Integrated Proteomics-Based Physical and Functional Mapping of AXL Kinase Signaling Pathways and Inhibitors Define Its Role in Cell Migration.

To better understand the signaling complexity of AXL, a member of the tumor-associated macrophage (TAM) receptor tyrosine kinase family, we created a physical and functional map of AXL signaling interactions, phosphorylation events, and target-engagement of three AXL tyrosine kinase inhibitors (TKI). We assessed AXL protein complexes using proximity-dependent biotinylation (BioID), effects of AXL TKI on global phosphoproteins using mass spectrometry, and target engagement of AXL TKI using activity-based protein profiling. BioID identifies AXL-interacting proteins that are mostly involved in cell adhesion/migration. Global phosphoproteomics show that AXL inhibition decreases phosphorylation of peptides involved in phosphatidylinositol-mediated signaling and cell adhesion/migration. Comparison of three AXL inhibitors reveals that TKI RXDX-106 inhibits pAXL, pAKT, and migration/invasion of these cells without reducing their viability, while bemcentinib exerts AXL-independent phenotypic effects on viability. Proteomic characterization of these TKIs demonstrates that they inhibit diverse targets in addition to AXL, with bemcentinib having the most off-targets. AXL and EGFR TKI cotreatment did not reverse resistance in cell line models of erlotinib resistance. However, a unique vulnerability was identified in one resistant clone, wherein combination of bemcentinib and erlotinib inhibited cell viability and signaling. We also show that AXL is overexpressed in approximately 30% to 40% of nonsmall but rarely in small cell lung cancer. Cell lines have a wide range of AXL expression, with basal activation detected rarely. IMPLICATIONS: Our study defines mechanisms of action of AXL in lung cancers which can be used to establish assays to measure drug targetable active AXL complexes in patient tissues and inform the strategy for targeting it's signaling as an anticancer therapy.

Tumor-infiltrating lymphocyte treatment for anti-PD-1-resistant metastatic lung cancer: a phase 1 trial.

Adoptive cell therapy using tumor-infiltrating lymphocytes (TILs) has shown activity in melanoma, but has not been previously evaluated in metastatic non-small cell lung cancer. We conducted a single-arm open-label phase 1 trial ( NCT03215810 ) of TILs administered with nivolumab in 20 patients with advanced non-small cell lung cancer following initial progression on nivolumab monotherapy. The primary end point was safety and secondary end points included objective response rate, duration of response and T cell persistence. Autologous TILs were expanded ex vivo from minced tumors cultured with interleukin-2. Patients received cyclophosphamide and fludarabine lymphodepletion, TIL infusion and interleukin-2, followed by maintenance nivolumab. The end point of safety was met according to the prespecified criteria of ≤17% rate of severe toxicity (95% confidence interval, 3-29%). Of 13 evaluable patients, 3 had confirmed responses and 11 had reduction in tumor burden, with a median best change of 35%. Two patients achieved complete responses that were ongoing 1.5 years later. In exploratory analyses, we found T cells recognizing multiple types of cancer mutations were detected after TIL treatment and were enriched in responding patients. Neoantigen-reactive T cell clonotypes increased and persisted in peripheral blood after treatment. Cell therapy with autologous TILs is generally safe and clinically active and may constitute a new treatment strategy in metastatic lung cancer.

Managing a Large-Scale Multiomics Project: A Team Science Case Study in Proteogenomics.

Highly collaborative scientists are often called on to extend their expertise to different types of projects and to expand the scope and scale of projects well beyond their previous experience. For a large-scale project involving "big data" to be successful, several different aspects of the research plan need to be developed and tested, which include but are not limited to the experimental design, sample collection, sample preparation, metadata recording, technical capability, data acquisition, approaches for data analysis, methods for integration of different data types, recruitment of additional expertise as needed to guide the project, and strategies for clear communication throughout the project. To capture this process, we describe an example project in proteogenomics that built on our collective expertise and experience. Key steps included definition of hypotheses, identification of an appropriate clinical cohort, pilot projects to assess feasibility, refinement of experimental designs, and extensive discussions involving the research team throughout the process. The goal of this chapter is to provide the reader with a set of guidelines to support development of other large-scale multiomics projects.

PHGDH supports liver ceramide synthesis and sustains lipid homeostasis.

BACKGROUND: d-3-phosphoglycerate dehydrogenase (PHGDH), which encodes the first enzyme in serine biosynthesis, is overexpressed in human cancers and has been proposed as a drug target. However, whether PHGDH is critical for the proliferation or homeostasis of tissues following the postnatal period is unknown. METHODS: To study PHGDH inhibition in adult animals, we developed a knock-in mouse model harboring a PHGDH shRNA under the control of a doxycycline-inducible promoter. With this model, PHGDH depletion can be globally induced in adult animals, while sparing the brain due to poor doxycycline delivery. RESULTS: We found that PHGDH depletion is well tolerated, and no overt phenotypes were observed in multiple highly proliferative cell compartments. Further, despite detectable knockdown and impaired serine synthesis, liver and pancreatic functions were normal. Interestingly, diminished PHGDH expression reduced liver serine and ceramide levels without increasing the levels of deoxysphingolipids. Further, liver triacylglycerol profiles were altered, with an accumulation of longer chain, polyunsaturated tails upon PHGDH knockdown. CONCLUSIONS: These results suggest that dietary serine is adequate to support the function of healthy, adult murine tissues, but PHGDH-derived serine supports liver ceramide synthesis and sustains general lipid homeostasis.

A community-based lung cancer rapid tissue donation protocol provides high-quality drug-resistant specimens for proteogenomic analyses.

BACKGROUND: For the advancement of cancer research, the collection of tissue specimens from drug-resistant tumors after targeted therapy is crucial. Although patients with lung cancer are often provided targeted therapy, post-therapy specimens are not routinely collected due to the risks of collection, limiting the study of targeted therapy resistance mechanisms. Posthumous rapid tissue donation (RTD) is an expedient collection process that provides an opportunity to understand treatment-resistant lung cancers. METHODS: Consent to participate in the thoracic RTD protocol was obtained during patient care. When death occurred, tumor and paired non-tumor, cytology, and blood specimens were collected within 48 hours and preserved as formalin-fixed and frozen specimens. Tissue sections were evaluated with hematoxylin and eosin staining and immunohistochemistry (IHC) against multiple biomarkers, including various programmed death ligand 1 (PD-L1) clones. Next-generation sequencing was performed on 13 specimens from 5 patients. RESULTS: Postmortem specimens (N = 180) were well preserved from 9 patients with lung cancer. PD-L1 IHC revealed heterogeneity within and between tumors. An AGK-BRAF fusion was newly identified in tumor from a donor with a known echinoderm microtubule-associated protein-like 4 to anaplastic lymphoma kinase (EML4-ALK) fusion and history of anaplastic lymphoma kinase (ALK) inhibitor therapy. RNA expression analysis revealed a clonal genetic origin of metastatic cancer cells. CONCLUSIONS: Post-therapy specimens demonstrated PD-L1 heterogeneity and an acyl glycerol kinase to B-rapidly accelerated fibrosarcoma (AGK-BRAF) fusion in a patient with an EML4-ALK-positive lung adenocarcinoma as a potential resistance mechanism to ALK inhibitor therapy. Rapid tissue donation collection of postmortem tissue from lung cancer patients is a novel approach to cancer research that enables studies of molecular evolution and drug resistance.

Proteogenomic landscape of squamous cell lung cancer.

How genomic and transcriptomic alterations affect the functional proteome in lung cancer is not fully understood. Here, we integrate DNA copy number, somatic mutations, RNA-sequencing, and expression proteomics in a cohort of 108 squamous cell lung cancer (SCC) patients. We identify three proteomic subtypes, two of which (Inflamed, Redox) comprise 87% of tumors. The Inflamed subtype is enriched with neutrophils, B-cells, and monocytes and expresses more PD-1. Redox tumours are enriched for oxidation-reduction and glutathione pathways and harbor more NFE2L2/KEAP1 alterations and copy gain in the 3q2 locus. Proteomic subtypes are not associated with patient survival. However, B-cell-rich tertiary lymph node structures, more common in Inflamed, are associated with better survival. We identify metabolic vulnerabilities (TP63, PSAT1, and TFRC) in Redox. Our work provides a powerful resource for lung SCC biology and suggests therapeutic opportunities based on redox metabolism and immune cell infiltrates.

Phase I/Ib Study of Pembrolizumab Plus Vorinostat in Advanced/Metastatic Non-Small Cell Lung Cancer.

PURPOSE: Histone deacetylase inhibitors (HDACi) enhance tumor immunogenicity through several mechanisms and may improve response to immune checkpoint inhibitors (ICIs). In a phase I/Ib trial, we tested the oral HDACi vorinostat combined with the programmed cell death protein 1 inhibitor pembrolizumab in advanced/metastatic non-small cell lung cancer. PATIENTS AND METHODS: Patients received intravenous pembrolizumab (200 mg every 3 weeks) plus oral vorinostat (200 or 400 mg/day). Primary endpoint was safety/tolerability. Secondary endpoints included response rate, progression-free survival, disease control rate (DCR), and overall survival. Tumor gene expression changes, T-cell density, and myeloid cell levels were studied in serial tissue specimens. RESULTS: Thirty-three patients were treated (13 in phase I, 20 in phase Ib). In phase I, both ICI-naïve and ICI-pretreated patients were enrolled to determine dose-limiting toxicities (DLT). No DLTs were observed, and the recommended phase I dose was pembrolizumab 200 mg and vorinostat 400 mg. Any-grade adverse events were mainly fatigue (33%) and nausea/vomiting (27%). Of six ICI-naïve and 24 ICI-pretreated patients evaluable for response, four (13%) had partial response [two confirmed, one unconfirmed with subsequent prolonged stable disease (SD), one unconfirmed with subsequent progressive disease (PD)], 16 (53%) had SD, and 10 (33%) had PD for a DCR of 67%. In the ICI-pretreated cohort, three patients (one confirmed, two unconfirmed) had partial response and 10 had SD. Pretreatment CD8+ T-cell presence in tumor stromal regions was associated with treatment benefit. CONCLUSIONS: Pembrolizumab plus vorinostat was well tolerated and demonstrated preliminary antitumor activity despite progression on prior ICI treatment.