Somatic Tumors Research Articles

Genomic Reporting Practices Across 5 Molecular Disciplines: A Study From the College of American Pathologists.

Genomic reports are primarily organized in a narrative and unstructured format with variations in content and format. Regulatory requirements and professional guidelines for genetic test reporting exist but provide little guidance for effective communication of information. To assess clinical genomic reporting practices across 5 disciplines within molecular diagnostics, including germline, somatic solid tumors, somatic hematologic malignancies, pharmacogenomics, and prenatal cell-free DNA screening. Reporting practices were assessed by using a structured review of clinical genomic reports from multiple laboratories in 5 molecular disciplines spanning different practice settings. Report content was reviewed by the presence/absence of from 27 to 44 elements, including 23 elements required by the College of American Pathologists and/or the Clinical Laboratory Improvement Amendments of 1988 (CLIA). If present, the element's location on the report was recorded. A total of 69 genomics reports from 31 laboratories were reviewed. Overall, the reports were compliant with regulatory requirements but showed variability in both format and content. Six of 7 required reporting elements (per CLIA, 42 CFR [Code of Federal Regulations] 493.1291) were included in 90% of the reports. However, these elements were often located in different report sections. Only patient demographics were always found in a specific report section (header). These results show that reports are overall compliant with regulatory requirements, despite some reporting elements being less consistently reported. The lack of consistent presentation of the data elements presents an opportunity to improve the communication of molecular testing results to clinicians and patients.

Shared germline genomic variants in two patients with double primary gastrointestinal stromal tumours (GISTs)

BackgroundGastrointestinal stromal tumours (GISTs) are prevalent mesenchymal tumours of the gastrointestinal tract, commonly exhibiting structural variations in KIT and PDGFRA genes. While the mutational profiling of somatic tumours is well...

Predictive Value and Therapeutic Significance of Somatic BRCA Mutation in Solid Tumors.

Ten percent of patients with breast cancer, and probably somewhat more in patients with ovarian cancer, have inherited germline DNA mutations in the breast and ovarian cancer genes BRCA1 and BRCA2. In the remaining cases, the disease is caused by acquired somatic genetic and epigenetic alterations. Targeted therapeutic agents, such as poly ADP-ribose polymerases (PARP) inhibitors (PARPi), have emerged in treating cancers associated with germline BRCA mutations since 2014. The first PARPi was FDA-approved initially for ovarian cancer patients with germline BRCA mutations. Deleterious variants in the BRCA1/BRCA2 genes and homologous recombination deficiency status have been strong predictors of response to PARPi in a few solid tumors since then. However, the relevance of somatic BRCA mutations is less clear. Somatic BRCA-mutated tumors might also respond to this new class of therapeutics. Although the related literature is often controversial, recently published case reports and/or randomized studies demonstrated the effectiveness of PARPi in treating patients with somatic BRCA mutations. The aim of this review is to summarize the predictive role of somatic BRCA mutations and to provide further assistance for clinicians with the identification of patients who could potentially benefit from PARPi.

Artificial intelligence in technologies for segmentation and classification of neuro-oncological lesions

The study is devoted to considering the effectiveness of modern approaches to the development of diagnostic technology for analyzing MRI images in neuro-oncology, based on artificial intelligence (AI) and computer vision. Such approaches are necessary for rapid and diagnostically effective analysis to implement the principle of individualized medicine. Material and methods. An analysis of the effectiveness of the choice of AI technologies for the formation of processes of segmentation and classification of neuro-oncological MRI images has been presented. AI was trained on its own annotated database (SBT Dataset), containing about 1000 clinical cases based on archival data from preoperative MRI studies at the Federal Neurosurgical Center (Novosibirsk, Russian Federation), in patients with astrocytoma, glioblastoma, meningioma, neuroma, and with metastases of somatic tumors, with histological and histochemical postoperative confirmation. Results and discussion. The effectiveness and efficiency of the developed technologies was tested during the international BraTS competition, in which it was proposed to segment and classify cases from a dataset of neuro-oncological patients prepared by the competition organizers. Conclusions. The methodological approaches proposed in the article in the development of diagnostic systems based on AI and the principles of computer vision have shown high efficiency at the level of dozens of world leaders and can be used to develop software and hardware systems for diagnostic neuroradiology with the functions of a “doctor’s assistant.”

Evaluation the Effect of Sonodynamic Therapy with 5-Aminolevulinic Acid and Sodium Fluorescein by Preclinical Animal Study.

Sonodynamic therapy (SDT) is a novel tumor treatment that combines biosafe sonosensitizers and noninvasive focused ultrasound to eradicate solid tumors. Sonosensitizers such as 5-aminolevulinic acid and fluorescein have great potential in tumor treatment. Here, rodent subcutaneous and brain tumor models were used to evaluate the treatment effect of both 5-ALA- and fluorescein-mediated SDT. The subcutaneous tumor growth rates of both SDT groups were significantly inhibited compared with that of the control groups. For intracranial tumors, 5-ALA-SDT treatment significantly inhibited brain tumor growth, while fluorescein-SDT exerted no therapeutic effect in animals. The distribution of fluorescein in the brain tumor region underwent further assessment. Seven days post tumor implantation, experimental animals received fluorescein and were sacrificed for brain specimen collection. Analysis of the dissected brains revealed no fluorescence signals, indicating an absence of fluorescein accumulation in the early-stage glioma tissue. These data suggest that the fluorescein-SDT treatment response is closely related to the amount of accumulated fluorescein. This study reports the equivalent effects of 5-ALA and fluorescein on the treatment of somatic tumors. For orthotopic brain tumor models, tumor vascular permeability should be considered when choosing fluorescein as a sonosensitizer. In conclusion, both fluorescein and 5-ALA are safe and effective SDT sonosensitizers, and the tumor microenvironment and pathologic type should be considered in the selection of adequate sonosensitizers.

EBV-Associated Smooth Muscle Tumors With Autoimmune Hemolytic Anemia and Hepatitis B Infection: Report of a Previously Undescribed Neoplasm With Review.

Epstein-Barr virus-associated smooth muscle tumor (EBV-SMT) is rare in adults. The presence of intratumoral T lymphocytes and primitive rounded cells characterized this neoplasm. We report a 24-year-old Chinese man who developed EBV-SMT in the right adrenal gland with hepatitis B infection and autoimmune hemolytic anemia without a history of HIV infection, primary immune deficiency, organ transplantation, or malignant tumor. This patient had an unknown immunodeficient state. EBV-SMTs are commonly located in the liver, lung, and gastrointestinal tract but rarely in the adrenal gland. We reviewed 10 reported literature on EBV-SMT in the adrenal gland. It is imperative to distinguish EBV-SMT from conventional somatic smooth muscle tumors. The discovery of EBV-SMT forces the clinician to conduct a thorough evaluation of immune function and immune status surveillance, and these patients are vulnerable to subsequent malignant tumors.

SIG: Graph-Based Cancer Subtype Stratification With Gene Mutation Structural Information.

Somatic tumors have a high-dimensional, sparse, and small sample size nature, making cancer subtype stratification based on somatic genomic data a challenge. Current methods for improving cancer clustering performance focus on dimension reduction, integrating multi-omics data, or generating realistic samples, yet ignore the associations between mutated genes within the patient-gene matrix. We refer to these associations as gene mutation structural information, which implicitly includes cancer subtype information and can enhance subtype clustering. We introduce a novel method for cancer subtype clustering called SIG(Structural Information within Graph). As cancer is driven by a combination of genes, we establish associations between mutated genes within the same patient sample, pair by pair, and use a graph to represent them. An association between two mutated genes corresponds to an edge in the graph. We then merge these associations among all mutated genes to obtain a structural information graph, which enriches the gene network and improves its relevance to cancer clustering. We integrate the somatic tumor genome with the enriched gene network and propagate it to cluster patients with mutations in similar network regions. Our method achieves superior clustering performance compared to SOTA methods, as demonstrated by clustering experiments on ovarian and LUAD datasets. The code is available at https://github.com/ChangSIG/SIG.git.

Spermatogonial fate in mice with increased activin A bioactivity and testicular somatic cell tumours.

Adult male fertility depends on spermatogonial stem cells (SSCs) which undergo either self-renewal or differentiation in response to microenvironmental signals. Activin A acts on Sertoli and Leydig cells to regulate key aspects of testis development and function throughout life, including steroid production. Recognising that activin A levels are elevated in many pathophysiological conditions, this study investigates effects of this growth factor on the niche that determines spermatogonial fate. Although activin A can promote differentiation of isolated spermatogonia in vitro, its impacts on SSC and spermatogonial function in vivo are unknown. To assess this, we examined testes of Inha KO mice, which feature elevated activin A levels and bioactivity, and develop gonadal stromal cell tumours as adults. The GFRA1+ SSC-enriched population was more abundant and proliferative in Inha KO compared to wildtype controls, suggesting that chronic elevation of activin A promotes a niche which supports SSC self-renewal. Intriguingly, clusters of GFRA1+/EOMES+/LIN28A- cells, resembling a primitive SSC subset, were frequently observed in tubules adjacent to tumour regions. Transcriptional analyses of Inha KO tumours, tubules adjacent to tumours, and tubules distant from tumour regions revealed disrupted gene expression in each KO group increased in parallel with tumour proximity. Modest transcriptional changes were documented in Inha KO tubules with complete spermatogenesis. Importantly, tumours displaying upregulation of activin responsive genes were also enriched for factors that promote SSC self-renewal, including Gdnf, Igf1, and Fgf2, indicating the tumours generate a supportive microenvironment for SSCs. Tumour cells featured some characteristics of adult Sertoli cells but lacked consistent SOX9 expression and exhibited an enhanced steroidogenic phenotype, which could arise from maintenance or acquisition of a fetal cell identity or acquisition of another somatic phenotype. Tumour regions were also heavily infiltrated with endothelial, peritubular myoid and immune cells, which may contribute to adjacent SSC support. Our data show for the first time that chronically elevated activin A affects SSC fate in vivo. The discovery that testis stromal tumours in the Inha KO mouse create a microenvironment that supports SSC self-renewal but not differentiation offers a strategy for identifying pathways that improve spermatogonial propagation in vitro.

Advances in Making Cancer Mouse Models More Accessible and Informative through Non-Germline Genetic Engineering.

Genetically engineered mouse models (GEMMs) allow for modeling of spontaneous tumorigenesis within its native microenvironment in mice and have provided invaluable insights into mechanisms of tumorigenesis and therapeutic strategies to treat human disease. However, as their generation requires germline manipulation and extensive animal breeding that is time-, labor-, and cost-intensive, traditional GEMMs are not accessible to most researchers, and fail to model the full breadth of cancer-associated genetic alterations and therapeutic targets. Recent advances in genome-editing technologies and their implementation in somatic tissues of mice have ushered in a new class of mouse models: non-germline GEMMs (nGEMMs). nGEMM approaches can be leveraged to generate somatic tumors de novo harboring virtually any individual or group of genetic alterations found in human cancer in a mouse through simple procedures that do not require breeding, greatly increasing the accessibility and speed and scale on which GEMMs can be produced. Here we describe the technologies and delivery systems used to create nGEMMs and highlight new biological insights derived from these models that have rapidly informed functional cancer genomics, precision medicine, and immune oncology.

Abstract 5818: Cadherin complexes recruit PIWIL2 to suppress pro-tumorigenic transformation

Abstract Recent studies have shown that genomic instability, oncogene expression, and high mutation rates in more than 50% of tumors can be attributed to increased transposon activity. Transposons, also called transposable elements (TEs), are parasitic mobile DNA elements that make up 45% of the human genome and can cause DNA damage and gene mutations. The reasons for increased TE activity in somatic tumors are currently unknown. TE RNA transcripts are targeted for degradation by PIWI ribonucleases, which are members of the Argonaute superfamily of proteins, through regulation of small RNAs called piRNAs (PIWI-interacting RNAs). Although the function of the PIWI-piRNA pathway has been extensively studied in the germline, there is little understanding about the presence or functionality of the pathway in somatic tissues. We have evidence of a novel interaction of the adherens junctions of well-differentiated epithelial cells with PIWIL2 (PIWI-like RNA-Mediated Gene Silencing 2), a key catalytic component of the PIWI-piRNA complex. Through immunofluorescence staining, confocal microscopy, and co-immunoprecipitation studies, we found co-localization and association of PIWIL2, as well as of other key members of the PIWI complex, such as PIWIL4 and TDRD1, with E-cadherin and p120 catenin at adherens junctions of well-differentiated breast and colon epithelial cells, whereas this association is lost in cancer cells and patient tissues. Adherens junction disruption results in mis-localization of PIWIL2, PIWIL4, and TDRD1 from the adherens junctions and their accumulation either to the cytoplasm or to the nucleus. E-cadherin depletion particularly results in increased expression of the LINE1 transposon, which is the most abundant transposon in human cells, and in increased levels of γ-H2AX, an indicator of DNA damage. Our working hypothesis is that cadherin junctions of well-differentiated epithelial cells recruit and regulate the PIWIL2 complex to suppress transposon activity. Since both loss of junctional integrity and increased transposon activity are universal events in cancer, this study has the potential to deepen our understanding of the role of the PIWI-transposon pathway in somatic tumorigenesis. Citation Format: Alyssa Risner, Joyce Nair-Menon, Vamsi Gangaraju, Antonis Kourtidis. Cadherin complexes recruit PIWIL2 to suppress pro-tumorigenic transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5818.

Identification of circulating tumour DNA (ctDNA) from the liquid biopsy results: Findings from an observational cohort study

Liquid biopsies can be a rapid, cost-effective and non-invasive alternative to tumour biopsies for detecting genetic mutations in somatic tumours. Genetic profiling of liquid biopsies can also be used to identify novel antigens for targeted therapy, provide updated information on disease prognosis and evaluate treatment efficacy. In this study, we aimed to examine mutations that could be identified in liquid biopsy and their distribution in a small study cohort. We studied the genomic profiles of 99 blood samples from 85 patients with 21 different types of cancer using two commercially available liquid biopsy tests. The mean circulating free DNA (cfDNA) concentration was 162.7 ± 352.3 nanograms per 20 millilitres. Amongst cfDNA, the circulating tumour DNA (ctDNA) percentage ranged from 0.006% to 90.6%. With the exception of samples with gene amplification and high microsatellite instability, the number of mutations in each sample varied from zero to 21, with an average of 5.6 mutations in each patient. Amongst these mutations, nonsynonymous mutations were the most frequently observed type of mutation (90% of the sample, with an average frequency of 3.6 mutations per patient). Mutations were observed in 76 different genes. TP53 mutations constituted more than 16% of the detectable mutations, especially in non-small cell lung cancer. All the tumour types, except the ovary, kidney and apocrine gland tumours, harboured at least one type of TP53 mutation. KRAS (mainly in pancreatic cancer) and PIK3CA (mostly in breast cancer) mutations, were responsible for an additional 10% of the mutations in the studied samples. The tumour mutations were specific to each patient, as approximately 94.7% of the mutations were so unique that there was almost no duplication amongst the patients. These findings indicate that liquid biopsy can detect specific molecular changes of tumour, which is useful for precision oncology and personalized cancer treatment.

Specific features of designing a database for neuro-oncological 3D MRI images to be used in training artificial intelligence

The research was aimed at analyzing current approaches to the organization and design methodology of visualization database built on the basis of computer vision . Such approaches are necessary for effective development of diagnostic systems using artificial intelligence (AI). A training data set of high quality is a mandatory prerequisite for that . Material and methods . The paper presents the technology for designing an annotated database (SBT Dataset ) that contains about 1000 clinical cases based on the archived data acquired by the Federal Neurosurgical Center, Novosibirsk , Russia including data on patients with astrocytoma , glioblastoma , meningioma , neurinoma , and patients with metastases of somatic tumors . Each case is represented by a preoperative MRI. The Results and discussion . The dataset was built (SBT Dataset ) containing segmented 3D MRI images of 5 types of brain tumors with 991 verified observations . Each case is represented by four MRI sequences T1-WI, T1C ( with Gd-contrast ), T2-WI and T2-FLAIR with histological and histochemical postoperative confirmation . Tumors segmentation with verification of the tumor core elements boundaries and perifocal edema was approved by two certified experienced neuroradiologists . Conclusion . The database built during the research is comparable in its volume and quality ( verification level ) with the state-of-the-art databases . The methodological approaches proposed in this paper were focused on designing the high-quality medical computer vision systems . The database was used to create artificial intelligence systems with the “ physician assistant ” functions for preoperative MRI diagnostics in neurosurgery.

Atypical cartilage in type II germ cell tumors of the mediastinum show significantly different patterns of IDH1/2 mutations from conventional chondrosarcoma

AbstractNeoplastic cartilage is a common component of teratomas in type II germ cell tumors. Although IDH1/2 mutations have been well-described in somatic cartilaginous tumors, ranging from benign enchondromas to highly aggressive dedifferentiated chondrosarcomas, the presence of IDH1/2 mutations in cartilaginous neoplasms arising from germ cell tumors has not been previously investigated. To better understand the relationship between these tumors and their bone/soft tissue counterpart, we studied the IDH1/2 mutational status of 20 cases of primary mediastinal mixed germ cell tumors with areas of readily identifiable cartilaginous differentiation. Our study found that cartilaginous lesions arising in germ cell tumors have a different frequency and distribution of IDH1/2 mutations compared to those at somatic sites. We identified IDH1/2 mutations in only 15% (3/20) of cases, compared to a frequency in the literature among differentiated chondroid tumors of bone and soft tissue of 54%, a highly significant decreased frequency (p = 0.0011; chi-square test). Furthermore, they were exclusively IDH2 R172 mutations that occurred at a non-significant, increased frequency in the germ cell tumor group compared to conventional chondrosarcoma (15% vs. 5%, respectively, p > 0.05, chi-square test). The unexpected finding, therefore, was entirely attributable to the absence of IDH1 R132 mutation in chondroid neoplasia of germ cell origin (p < 0.00001, Fisher exact test). Our results suggest that a subset of cartilaginous lesions arising within type II germ cell tumors have a similar oncogenic mechanism to their bone/soft tissue counterpart but that the majority form using different oncogenic mechanisms compared to their somatic counterparts.

Brain Abnormalities in Patients with Germline Variants in H3F3: Novel Imaging Findings and Neurologic Symptoms Beyond Somatic Variants and Brain Tumors.

Pathogenic somatic variants affecting the genes Histone 3 Family 3A and 3B (H3F3) are extensively linked to the process of oncogenesis, in particular related to central nervous system tumors in children. Recently, H3F3 germline missense variants were described as the cause of a novel pediatric neurodevelopmental disorder. We aimed to investigate patterns of brain MR imaging of individuals carrying H3F3 germline variants. In this retrospective study, we included individuals with proved H3F3 causative genetic variants and available brain MR imaging scans. Clinical and demographic data were retrieved from available medical records. Molecular genetic testing results were classified using the American College of Medical Genetics criteria for variant curation. Brain MR imaging abnormalities were analyzed according to their location, signal intensity, and associated clinical symptoms. Numeric variables were described according to their distribution, with median and interquartile range. Eighteen individuals (10 males, 56%) with H3F3 germline variants were included. Thirteen of 18 individuals (72%) presented with a small posterior fossa. Six individuals (33%) presented with reduced size and an internal rotational appearance of the heads of the caudate nuclei along with an enlarged and squared appearance of the frontal horns of the lateral ventricles. Five individuals (28%) presented with dysgenesis of the splenium of the corpus callosum. Cortical developmental abnormalities were noted in 8 individuals (44%), with dysgyria and hypoplastic temporal poles being the most frequent presentation. Imaging phenotypes in germline H3F3-affected individuals are related to brain features, including a small posterior fossa as well as dysgenesis of the corpus callosum, cortical developmental abnormalities, and deformity of lateral ventricles.

Frequencies of actionable alterations found by somatic tumor sequencing in veterans with metastatic prostate cancer.

178 Background: Prostate cancer comprises one third of male Veteran cancers and is their second leading cause of cancer death. Metastatic prostate cancer is lethal. Next Generation Sequencing (NGS) of somatic tumors is recommended for metastatic prostate to identify actionable alterations targeted with approved therapies. Veterans with prostate cancers harboring alterations in genes involved in the DNA damage response (e.g. BRCA1/2) or high microsatellite instability (MSI-High) may be eligible for PARP inhibitors or checkpoint blockade immunotherapy, respectively. Potential candidates may be identified for ongoing clinical trials of novel precision oncology approaches. Methods: This is a retrospective analysis of clinical, genomic, demographic data from Veterans with metastatic prostate cancer who underwent somatic NGS using the Foundation Medicine NGS platform from 2019-February 2021. To be included, prostate cancer was submitted diagnosis for the NGS testing and metastatic disease determined by the VINCI natural language processing tool. Variables included demographic, clinical, and pathological characteristics (self-identified race/ethnicity, age, rurality of residence, Gleason score, specimen site, other cancer diagnosis, mutation frequency). Primary outcome was mutation rates in homologous recombination (HR) genes under current FDA approval for olaparib (ATM, BARD1, BRCA1, BRCA2, BRIP1, CDK12, CHEK1, CHEK2, FANCL, PALB2, RAD51B, RAD51C, RAD51D, RAD54L) or MSI-High. Raw variant data, submitted diagnosis, and clinical data were extracted from the NGS reports and harmonized for further variant annotation. Variant data included chromosome, position, reference and alternate allele, total depth, variant allele depth, and quality scores. Variants were annotated using ANNOVAR. Likely oncogenic and oncogenic mutations were identified using OncoKB. Results: 1,597 Veterans with metastatic prostate cancer underwent FMI NGS testing (63% White, 33% African American, 4% other). Median age was 66 years, 78.6% of cases from &gt;60 years. Of the 1,597 who underwent blood or tumor testing, at least one likely oncogenic mutation in an HR gene under FDA approval for olaparib was found in 369 (23.1%) of Veterans (19% of tissue-based tests, 32.9% of blood-based tests). Of 651 liquid biopsy tests with at least one HR gene mutation, 125 of 214 (52%) had mutations at a variant allele frequency (VAF) &lt;0.5% or were found in an MSI-High sample that could indicate a spurious mutation due to clonal hematopoiesis. 33 patients (2.1%) were MSI-High, (21 tissue-based and 12 blood-based). Frequencies of alterations in ATM (3.6%), CDK12 (5.6%), and BRCA2 (4%) in tissue-based tests were not significantly different from those reported in other series. Conclusions: NGS of somatic tumors from Veterans with metastatic prostate cancer identifies alterations that impact management and clinical outcomes.

TP53 mutations determined by targeted NGS in breast cancer: a case-control study.

Background: Tumor protein 53 (TP53) gene mutations are identified in up to 37% of breast tumors especially in HER-2 positive and basal-like subtype. Previous studies have indicated TP53 mutations as a prognostic biomarker in breast cancer. However, most of these studies performed immunohistochemistry (IHC) for the detection of TP53 mutations.Aim: The purpose of our study is to evaluate the role of TP53 somatic mutations detected via next-generation sequencing (NGS) as a potential prognostic marker in patients with breast cancer.Materials and Methods: 82 female patients with Stage I–III breast cancer underwent NGS in paraffin blocks and blood samples during the period 25/09/2019 through 25/05/2021. 23 cases of somatic TP53 mutations and 23 cases of healthy controls were matched on age at diagnosis, menopausal status, histological subtype, histological grade, ki67 expression and disease stage.Results: Mean age at diagnosis was 52.35 (SD; 11.47) years. The somatic TP53 mutation NM_000546.5:c.824G>A p.(Cys275Tyr) was most frequently detected. Co-existence of PIK3CA mutation was a common finding in somatic TP53-mutant tumors (4/23; 17.4%). Disease-free survival was shorter in TP53-mutated cases (16.3 months vs. 62.9 months). TP53 pathogenic somatic mutations were associated with a 8-fold risk of recurrence in the univariate Cox regression analysis (OR = 8.530, 95% CI: 1.81–40.117; p = 0.007).Conclusions: Our case-control study suggests that TP53 somatic mutations detected by next-generation sequencing (NGS) are associated with an adverse prognosis in breast cancer.

Combined RNA/tissue profiling identifies novel Cancer/testis genes.

Cancer/Testis (CT) genes are induced in germ cells, repressed in somatic cells, and derepressed in somatic tumors, where these genes can contribute to cancer progression. CT gene identification requires data obtained using standardized protocols and technologies. This is a challenge because data for germ cells, gonads, normal somatic tissues, and a wide range of cancer samples stem from multiple sources and were generated over substantial periods of time. We carried out a GeneChip‐based RNA profiling analysis using our own data for testis and enriched germ cells, data for somatic cancers from the Expression Project for Oncology, and data for normal somatic tissues from the Gene Omnibus Repository. We identified 478 candidate loci that include known CT genes, numerous genes associated with oncogenic processes, and novel candidates that are not referenced in the Cancer/Testis Database (www.cta.lncc.br). We complemented RNA expression data at the protein level for SPESP1, GALNTL5, PDCL2, and C11orf42 using cancer tissue microarrays covering malignant tumors of breast, uterus, thyroid, and kidney, as well as published RNA profiling and immunohistochemical data provided by the Human Protein Atlas (www.proteinatlas.org). We report that combined RNA/tissue profiling identifies novel CT genes that may be of clinical interest as therapeutical targets or biomarkers. Our findings also highlight the challenges of detecting truly germ cell‐specific mRNAs and the proteins they encode in highly heterogenous testicular, somatic, and tumor tissues.

MBCL-21. GERMLINE ELONGATOR MUTATIONS IN SONIC HEDGEHOG MEDULLOBLASTOMA

BACKGROUNDOur previous analysis of established cancer predisposition genes in medulloblastoma (MB) identified pathogenic germline variants in ~5% of all patients. Here, we extended our analysis to include all protein-coding genes.METHODSCase-control analysis performed on 795 MB patients against >118,000 cancer-free children and adults was performed to identify an association between rare germline variants and MB.RESULTSGermline loss-of-function variants of Elongator Complex Protein 1 (ELP1; 9q31.3) were strongly associated with SHH subgroup (MBSHH). ELP1-associated-MBs accounted for ~15% (29/202) of pediatric MBSHH cases and were restricted to the SHHα subtype. ELP1-associated-MBs demonstrated biallelic inactivation of ELP1 due to somatic chromosome 9q loss and most tumors exhibited co-occurring somatic PTCH1 (9q22.32) alterations. Inheritance was verified by parent-offspring sequencing (n=3) and pedigree analysis identified two families with a history of pediatric MB. ELP1-associated-MBSHH were characterized by desmoplastic/nodular histology (76%; 13/17) and demonstrated a favorable clinical outcome when compared to TP53-associated-MBSHH (5-yr OS 92% vs 20%; p-value=1.3e-6) despite both belonging to the SHHα subtype. ELP1 is a subunit of the Elongator complex, that promotes efficient translational elongation through tRNA modifications at the wobble (U34) position. Biochemical, transcriptional, and proteomic analyses revealed ELP1-associated-MBs exhibit destabilization of the core Elongator complex, loss of tRNA wobble modifications, codon-dependent translational reprogramming, and induction of the unfolded protein response.CONCLUSIONSWe identified ELP1 as the most common MB predisposition gene, increasing the total genetic predisposition for pediatric MBSHH to 40%. These results mark MBSHH as an overwhelmingly genetically-predisposed disease and implicate disruption of protein homeostasis in MBSHH development.

Detection of BRAFV600E in Liquid Biopsy from Patients with Papillary Thyroid Cancer Is Associated with Tumor Aggressiveness and Response to Therapy.

The detection of rare mutational targets in plasma (liquid biopsy) has emerged as a promising tool for the assessment of patients with cancer. We determined the presence of cell-free DNA containing the BRAFV600E mutations (cfBRAFV600E) in plasma samples from 57 patients with papillary thyroid cancer (PTC) with somatic BRAFV600E mutation-positive primary tumors using microfluidic digital PCR, and co-amplification at lower denaturation temperature (COLD) PCR. Mutant cfBRAFV600E alleles were detected in 24/57 (42.1%) of the examined patients. The presence of cfBRAFV600E was significantly associated with tumor size (p = 0.03), multifocal patterns of growth (p = 0.03), the presence of extrathyroidal gross extension (p = 0.02) and the presence of pulmonary micrometastases (p = 0.04). In patients with low-, intermediate- and high-risk PTCs, cfBRAFV600E was detected in 4/19 (21.0%), 8/22 (36.3%) and 12/16 (75.0%) of cases, respectively. Patients with detectable cfBRAFV600E were characterized by a 4.68 times higher likelihood of non-excellent response to therapy, as compared to patients without detectable cfBRAFV600E (OR (odds ratios), 4.68; 95% CI (confidence intervals)) 1.26–17.32; p = 0.02). In summary, the combination of digital polymerase chain reaction (dPCR) with COLD-PCR enables the detection of BRAFV600E in the liquid biopsy from patients with PTCs and could prove useful for the identification of patients with PTC at an increased risk for a structurally or biochemically incomplete or indeterminate response to treatment.

Phase II trial of a PARP inhibitor in somatic BRCA mutant metastatic breast cancer.

TPS1113 Background: Poly(ADP-ribose) polymerase (PARP) inhibitors are now approved for patients with germline BRCA1/2 mutated HER2 negative metastatic breast cancer (MBC). However, germline BRCA1/2 mutations only account for 5-10% of breast cancer. We previously demonstrated that a subset of MBC may harbor somatic BRCA1/2 mutations detectable by cell-free DNA (cfDNA) (Vidula, SABCS, 2017). We hypothesize that somatic BRCA1/2 mutant MBC may also respond to PARP inhibition, similar to ovarian cancer, where PARP inhibition is efficacious in both somatic and germline tumors (Oza, 2017). Methods: This single arm, open label, phase II clinical trial is evaluating the efficacy of talazoparib, a PARP inhibitor, in 30 patients with somatic pathogenic BRCA1/2 mutant MBC identified by cfDNA. Patients may have triple-negative disease with receipt of at least 1 prior chemotherapy regimen, or hormone receptor positive, HER2 negative disease with at least 1 prior hormone therapy for MBC. Patients may have received a prior platinum, in the absence of progression on platinum chemotherapy. Patients must not have a known germline BRCA1/2 mutation. Patients will be treated with talazoparib 1 mg daily until progression, unacceptable toxicity, or withdrawal of consent, with clinical exams monthly, scans (CT chest, abdomen, and pelvis, and bone scan as appropriate) every 3 months, and serial cfDNA collected monthly. The primary endpoint is progression-free survival, as defined by RECIST 1.1. Subjects are enrolled in a 2-stage design, which provides 80% power to demonstrate that treatment is associated with “success” (PFS &gt; 12 weeks) in ³ 53% patients (4% alpha). Additional endpoints include objective response rate and toxicity (per NCI CTCAE version 5.0). Correlative endpoints include determining changes in BRCA1/2 mutant allele fraction, genomic evolution including emergence of BRCA reversion mutations, and the impact of biomarker changes on outcomes. This trial is currently enrolling patients at the Massachusetts General Hospital. Successful completion of this study may help expand the patient population that is able to benefit from PARP inhibition. Clinical trial information: NCT03990896 .