Candidate Tumor Suppressor Gene Research Articles

Secreted Clusterin Inhibits Tumorigenesis by Modulating Tumor Cell and Macrophage in Human Meningioma.

Meningioma is the most common primary intracranial tumor with high frequency of postoperative recurrence, yet the biology of meningioma malignancy process is still obscure. To identify potential therapeutic targets and tumor suppressors, we performed single-cell transcriptome analysis through meningioma malignancy, which included 18 samples spanning normal meninges, benign and high grade in situ tumors, and lung metastases, for extensive transcriptome characterization. Tumor suppressor candidate gene and molecular mechanism were functionally validated at animal model and cellular level. Comprehensive analysis and validation in mice and clinical cohorts indicated Clusterin (CLU) had suppressive function for meningioma tumorigenesis and malignancy by inducing mitochondria damage and triggering type I interferon pathway dependent on its secreted isoform, and the inhibition effect was enhanced by TNFα as TNFα also induced type I interferon pathway. The expression of CLU was upregulated by histone deacetylase inhibition. Meanwhile, both intra- and extra-cellular CLU overexpression enhanced macrophage polarization towards M1 phenotype and TNFα production, thus promoted tumor killing and phagocytosis. CLU might be a key brake of meningioma malignance by synchronous modulating tumor cells and their microenvironment. Our work provides comprehensive insights into meningioma malignancy and a potential therapeutic strategy.

Molecular Characterization and Subtyping of Breast Cancer Cell Lines Provide Novel Insights into Cancer Relevant Genes.

Continuous cell lines are important and commonly used in vitro models in breast cancer (BC) research. Selection of the appropriate model cell line is crucial and requires consideration of their molecular characteristics. To characterize BC cell line models in depth, we profiled a panel of 29 authenticated and publicly available BC cell lines by mRNA-sequencing, mutation analysis, and immunoblotting. Gene expression profiles separated BC cell lines in two major clusters that represent basal-like (mainly triple-negative BC) and luminal BC subtypes, respectively. HER2-positive cell lines were located within the luminal cluster. Mutation calling highlighted the frequent aberration of TP53 and BRCA2 in BC cell lines, which, therefore, share relevant characteristics with primary BC. Furthermore, we showed that the data can be used to find novel, potential oncogenic fusion transcripts, e.g., FGFR2::CRYBG1 and RTN4IP1::CRYBG1 in cell line MFM-223, and to elucidate the regulatory circuit of IRX genes and KLF15 as novel candidate tumor suppressor genes in BC. Our data indicated that KLF15 was activated by IRX1 and inhibited by IRX3. Moreover, KLF15 inhibited IRX1 in cell line HCC-1599. Each BC cell line carries unique molecular features. Therefore, the molecular characteristics of BC cell lines described here might serve as a valuable resource to improve the selection of appropriate models for BC research.

Identification of tumor-suppressor genes in lung squamous cell carcinoma through integrated bioinformatics analyses.

Lung cancer is a prevalent malignancy, and fatalities of the disease exceed 400,000 cases worldwide. Lung squamous cell carcinoma (LUSC) has been recognized as the most common pathological form of lung cancer. The comprehensive understanding of molecular features related to LUSC progression has great significance in LUSC prognosis assessment and clinical management. In this study, we aim to identify a panel of signature genes closely associated with LUSC, which can provide novel insights into the progression of LUSC. Gene expression profiles were retrieved from public resources including gene expression omnibus (GEO) and the cancer genome atlas (TCGA) database. Differentially expressed genes (DEGs) between LUSC specimens and normal lung tissues were identified by bioinformatics analyses. A total of 66 DEGs were identified based on two cohorts of data. CytoHubba plugin of Cytoscape software was utilized for the further analyses of the top 10 candidate hub genes including OGN, ABI3BP, MAMDC2, FGF7, FAM107A, SPARCL1, DCN, COL14A1, and MFAP4 and CHRDL1, which showed significant downregulation in LUSC. Two LUSC cell lines were used to validate the functions of CHRDL1 and FAM107A through overexpression experiment. Together, our data revealed novel candidate tumor-suppressor genes in LUSC, suggesting previously unappreciated mechanisms in the progression of LUSC.

Clinical significance of tumor suppressor genes methylation in circulating tumor DNA of patients with pancreatic cancer

BackgroundCirculating tumor DNA (ctDNA) has emerged as a potential diagnostic and prognostic biomarker in various tumors. However, the role of tumor suppressor genes (TSGs) methylation in ctDNA of patients with pancreatic cancer (PC) remains largely unclear. MethodsPatients with PC (n = 43), pancreatic benign diseases (n = 39), and healthy controls (n = 20) were enrolled in the study. Quantitative analysis of methylation pattern of five candidate TSGs including NPTX2, RASSF1A, EYA2, p16, and ppENK in ctDNA was performed by next generation sequencing (NGS). The diagnostic performances of these 5-TSGs methylation were assessed by the operating characteristic (ROC) curve and clinicopathological features correlation analysis. Meanwhile, the changes in methylation levels of these 5-TSGs on the 7th postoperative day were evaluated in 23 PC patients who underwent radical resection. ResultsThe methylation levels of RASSF1A, EYA2, ppENK and p16 genes in patients with PC were significantly higher than those in healthy controls. EYA2, p16 and ppENK genes showed significantly hypermethylation in PC than those in pancreatic benign diseases. NPTX2, RASSF1A, EYA2, p16 and ppENK genes showed significantly hypermethylation in pancreatic benign diseases than those in healthy controls (P < 0.05). The methylation levels of these 5 candidate TSGs were not correlated with the tumor size, nerve invasion, lymph node metastasis and TNM stage of PC. The AUC of these biomarkers for diagnosis of PC ranged from 0.65 to 0.96. The AUC values of these methylated genes and CpG sites for differentiating malignant and benign pancreatic diseases were ranging from 0.68 to 0.92. Combined the hypermethylated genes improved the detective ability of PC than single gene. The methylation levels of NPTX2, EYA2 and ppENK genes were significantly decreased after radical resection of PC. ConclusionQuantitative analysis of methylation pattern of NPTX2, RASSF1A, EYA2, p16 and ppENK in ctDNA by NGS could be a valuable non-invasive tool for detection and monitoring of PC.

Regional bias of tumor suppressor gene mutations of STARD8 and WNK2 in colon cancers

StAR-related lipid transfer domain protein 8 (STARD8), encoding a Rho-GTPase-activating protein, and WNK2, encoding a serine/threonine kinase are candidate tumor suppressor genes (TSGs) in human cancers. Inactivation of these genes that would promote cancer pathogenesis is largely unknown in colon cancer (CC). Our study addressed to address whether STARD8 and WNK2 genes are mutated in CC. STARD8 and WNK2 genes possess mononucleotide repeats in their exons, which could be the targets for frameshift mutations in cancers with high microsatellite instability (MSI-H). By single-strand conformation polymorphism (SSCP) analysis, we analyzed the repeated sequences in 140 CCs (95 CCs with MSI-H and 45 CCs with stable MSI (MSS)). By DNA sequencing, we found that five MSI-H CCs (5/95: 5.3%) harbored the frameshift mutations, whereas MSS CCs (0/45) did not. In addition, we detected regional heterogeneous frameshift mutations of these genes in four (25%) of 16 MSI-H CCs. In immunohistochemistry for WNK2, WNK2 expression in the MSI-H CCs was significantly lower than that in the MSS CCs. Our results for the mutation and expression indicate that STARD8 and WNK2 genes are altered at various levels (frameshift mutation, expression, and regional heterogeneity) in MSI-H CCs, which might play a role in the pathogenesis by inactivating their TSG functions.

Natural Killer Cells Are Active Against Myeloma, Leukemia or Lymphoma Cells with Loss of Tumor Suppressor Genes

The therapeutic targeting of tumor cells with loss of function (LOF) for tumor suppressor genes (TSGs) is challenging across cancers, including hematologic neoplasias, because pharmacological mechanisms to restore the function(s) of such genes are not readily feasible, in contrast to e.g., inhibition of oncogenic drivers. We reasoned, however, that, although LOF for TSGs leads to de-repressed growth of neoplastic hematopoietic cells, it may not necessarily protect them from immune attack. We thus explored the hypothesis that CRISPR-based loss of function of TSGs in cells from multiple myeloma (MM), leukemias or lymphoma may still be associated with substantial response to immune effector cells such as NK cells, which have the advantage to kill tumor cells across HLA barriers. We have conducted CRISPR-based studies in 7 cell lines that represent different hematologic malignancies and different levels of sensitivity to natural killer (NK) cells, namely the B-cell lymphoma (SUDHL4), precursor B cell acute lymphoblastic leukemia (NALM6), multiple myeloma (MM1.S, LP1, KMS11), chronic myeloid leukemia (K562), and acute myeloid leukemia (MOLM14). In these genome-scale or focused CRISPR screens for LOF (CRISPR-based gene editing) or gain of function (GOF, CRISPR activation), the blood cancer lines were exposed to allogeneic donor-derived NK cells (vs. control cultures without NK cells). We evaluated the performance of genes known to represent recurrent TSGs based on genomic data of patient samples or cell lines; as well as candidate TSGs, based on results from genome-scale CRISPR gene editing screens (e.g., CERES or CHRONOS scores &amp;gt;0.4 in multiple DepMap releases and TPM&amp;gt;1 [RNA-seq]) in the same cell lines as the NK cell resistance screens. These analyses sought to identify any TSGs whose LOF may potentially alter the response of blood cancer cells to NK cells. We also evaluated genes identified as top recurrent TSGs in patient samples from MM and other hematologic neoplasias (e.g., based on prior genomic studies). On aggregate, we evaluated a collection of known and recurrent TSGs (e.g., PTEN, TP53, RB1, CDKN2C, CDKN1B, TENT5C/FAM46C) as well as other, previously underappreciated candidate genes with TSG properties in hematologic neoplasias (e.g., HIF1A, DEPDC5). Perturbation of none of these genes was identified to meet criteria for association with significant resistance to allogeneic donor-derived NK cells (e.g., log2FC&amp;gt;1.0, at least 3-4 sgRNAs with enrichment upon CRISPR KO or depletion with CRISPR activation, p-value &amp;lt;0.05, enrichment rank &amp;lt;100, based on rank aggregation algorithm) in any of the MM, leukemia or lymphoma cell lines examined in LOF or GOF CRISPR screens for NK cell resistance. In fact, for a limited set of cases (e.g., PTEN in KMS11 cells), KO of a TSG was associated with sensitization to NK cell treatment. To probe the mechanistic basis for this lack of effect of TSG loss, we examined the molecular sequelae of CRISPR-based KO for one of these recurrent TSGs, PTEN, by performing scRNAseq using the CROP-seq platform. Pools of MM1.S and LP1 cells expressing sgRNAs targeting select hits from our CRISPR screens and also PTEN were co-cultured with NK cells for 24 h or left untreated, followed by scRNA-seq and sgRNA detection, differential gene-expression analysis. We observed in these studies that the transcriptional changes induced in MM cells by KO of PTEN included limited, if any, changes in the expression of key genes involved in regulation of NK cell responses of tumor cells, e.g., ligands for activating or inhibitor receptors in NK cells, death receptors (e.g., TRAIL, Fas) or their downstream effectors/regulators or other molecules identified from our aforementioned genome-scale and focused CRISPR LOF and GOF studies. Notably, our in-house results from studies of NK exposure of cell lines from hematologic neoplasias are concordant with results for these TSGs in CRISPR screens of non-hematological cancer cells treated with cytotoxic T-cells (e.g., 4T1 or RENCA cells; GSE149933). Overall, our observations indicate that MM, leukemia or lymphoma cells that become deficient for diverse TSGs based on CRISPR-based gene editing are equally responsive to NK cells as their TSG-proficient counterparts. NK cell-based therapies may thus be a promising approach to target TSG-deficient hematologic malignancies for which specific pharmacological therapies are not currently available.

Retracted] Functional characterization of the nitrogen permease regulator‑like‑2 candidate tumor suppressor gene in colorectal cancer cell lines.

Following the publication of this paper, it was drawn to the Editor's attention by a concerned reader that certain of the microscopic images shown in Fig.1C on p.3489 and the invasion assay images shown in Fig.5 on p.3491 were strikingly similar to data appearing in different form in other articles written by different authors at different research institutes. Moreover, unexpected similarities were identified comparing between a pair of the flow cytometric assay data panels in Fig.4 on p.3490, considering that these data were intended to show the results from differently performed experiments. Owing to the fact that the contentious data in the above article had already been published, or were already under consideration for publication, prior to its submission to Molecular Medicine Reports, the Editor has decided that this paper should be retracted from the Journal. The authors were asked for an explanation to account for these concerns, but the Editorial Office did not receive a reply. The Editor apologizes to the readership for any inconvenience caused. [Molecular Medicine Reports 12: 3487‑3493, 2015; DOI: 10.3892/mmr.2015.3881].

Expression and prognostic value of AIM1L in esophageal squamous cell carcinoma.

Absent in melanoma 1-like (AIM1L), also known as crystalline beta gamma domain containing 2. The relationship between AIM1L and tumors has not been fully investigated, and the biological function of AIM1L in different tumors is unknown, so we bioinformatically explored a possible relationship between AIM1L and esophageal squamous cell carcinoma (ESCC). AIM1L mRNA expression was detected by the Gene Expression Omnibus database (GSE20347, GSE161533, and GSE53625), and protein level expression was detected by immunohistochemistry. The correlation between AIM1L expression and clinical pathological characteristics was evaluated by the Wilcoxon signed rank test or chi-square test. Kaplan-Meier analysis and Cox proportional risk regression model were used to determine the prognostic value of AIM1L in ESCC patients and establish and verify a nomogram. Find genes highly related to the expression of AIM1L, conduct GO and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, and conduct GSEA analysis on the gene set. The "CIBERSORT" R package was used to explore the relationship between AIM1L and immune infiltration, and the "OncoPredict" R package was used to explore the relationship between AIM1L and drug sensitivity. Compared with the matched adjacent non-cancer tissues, the expression of AIM1L was down-regulated in ESCC tissues, and correlated with tumor grade. Kaplan-Meier survival analysis and Cox analysis showed that the low expression of AIM1L was related to the poor prognosis of ESCC patients. Enrichment analysis explained the possible function of AIM1L, GSEA determined the highly correlated signal pathway of AIM1L low expression phenotype, immune infiltration analysis determined that AIM1L was related to activated NK cells and macrophage M2, and drug sensitivity analysis determined that the low expression of AIM1L might be related to EGFR targeted drug resistance. AIM1L may be a candidate tumor suppressor gene for ESCC and an independent molecular biomarker for the prognosis of ESCC patients.

Genomic Loss and Epigenetic Silencing of the FOSL1 Tumor Suppressor Gene in Radiation-induced Neoplastic Transformation of Human CGL1 Cells Alters the Tumorigenic Phenotype In Vitro and In Vivo.

The CGL1 human hybrid cell system has been utilized for many decades as an excellent cellular tool for investigating neoplastic transformation. Substantial work has been done previously implicating genetic factors related to chromosome 11 to the alteration of tumorigenic phenotype in CGL1 cells. This includes candidate tumor suppressor gene FOSL1, a member of the AP-1 transcription factor complex which encodes for protein FRA1. Here we present novel evidence supporting the role of FOSL1 in the suppression of tumorigenicity in segregants of the CGL1 system. Gamma-induced mutant (GIM) and control (CON) cells were isolated from 7 Gy gamma-irradiated CGL1s. Western, Southern and Northern blot analysis were utilized to assess FOSL1/FRA1 expression as well as methylation studies. GIMs were transfected to re-express FRA1 and in vivo tumorigenicity studies were conducted. Global transcriptomic microarray and RT-qPCR analysis were used to further characterize these unique cell segregants. GIMs were found to be tumorigenic in vivo when injected into nude mice whereas CON cells were not. GIMs show loss of Fosl/FRA1 expression as confirmed by Western blot. Southern and Northern blot analysis further reveals that FRA1 reduction in tumorigenic CGL1 segregants is likely due to transcriptional suppression. Results suggest that radiation-induced neoplastic transformation of CGL1 is in part due to silencing of the FOSL1 tumor suppressor gene promoter by methylation. The radiation-induced tumorigenic GIMs transfected to re-express FRA1 resulted in suppression of subcutaneous tumor growth in nude mice in vivo. Global microarray analysis and RT-qPCR validation elucidated several hundred differentially expressed genes. Downstream analysis reveals a significant number of altered pathways and enriched Gene Ontology terms genes related to cellular adhesion, proliferation, and migration. Together these findings provide strong evidence that FRA1 is a tumor suppressor gene deleted and epigenetically silenced after ionizing radiation-induced neoplastic transformation in the CGL1 human hybrid cell system.

Clinical and genomic features of non-small cell lung cancer occurring in families.

Exposure to environmental carcinogens, such as through smoking, is a major factor in the carcinogenesis of non-small cell lung cancer (NSCLC). However, genetic factors may also contribute. To identify candidate tumor suppressor genes for NSCLC, we included 23 patients (10 related pairs and 3 individuals) with NSCLC who had other NSCLC-affected first-degree relatives in a local hospital. Exome analyses for both germline and somatic (NSCLC specimens) DNA were performed for 17 cases. Germline exome data of these 17 cases revealed that most of the short variants were identical to the variants in 14KJPN (a Japanese reference genome panel of more than 14 000 individuals) and only a nonsynonymous variant in the DHODH gene, p.A347T, was shared between a pair of NSCLC patients in the same family. This variant is a known pathogenic variant of the gene for Miller syndrome. Somatic genetic alterations in the exome data of our samples showed frequent mutations in the EGFR and TP53 genes. Principal component analysis of the patterns of 96 types of single nucleotide variants (SNVs) suggested the existence of unique mechanisms inducing somatic SNVs in each family. Delineation of mutational signatures of the somatic SNVs with deconstructSigs for the pair of germline pathogenic DHODH variant-positive cases showed that the mutational signatures of these cases included SBS3 (homologous recombination repair defect), SBS6, 15 (DNA mismatch repair), and SBS7 (ultraviolet exposure), suggesting that disordered pyrimidine production causes increased errors in DNA repair systems in these cases. Our results suggest the importance of the detailed collection of data on environmental exposure along with genetic information on NSCLC patients to identify the unique combinations that cause lung tumorigenesis in a particular family.

Chromosome 1p status in neuroblastoma correlates with higher expression levels of miRNAs targeting neuronal differentiation pathway.

Neuroblastoma (NB) is characterized by acquired segmental and numerical chromosome aberrations. Although deletions of distal 1p and 11q are frequent alterations, no candidate tumor suppressor gene residing in these chromosomal sites could be identified so far. In the present study, we detected the genomic imbalances of six neuroblastoma cell lines using the multiplex ligation-dependent probe amplification (MLPA) technique and the microRNA (miRNA) expression profiles of the cell lines by a microarray study. According to MLPA results, we aimed to assess the miRNA expression profiles of the cell lines harboring 11q and 1p deletions. The cell lines with 1p deletions revealed statistically significant higher levels of expression for 29 miRNAs in contrast to the cell lines without 1p deletion in microarray study. We also performed GO enrichment analysis for predicted targets of the differentially expressed miRNAs. According to GO enrichment analysis, miRNAs that showed the high change in expression was associated with neuronal differentiation. We showed that hsa-miR-494, hsa-miR-495, and hsa-miR-543 target most of mRNAs in neuronal differentiation pathway. Although limited to the cell lines, our results highly suggest that NBs with different segmental chromosome abnormalities may have different dysregulated miRNA expression signatures that target the genes involved in neuronal differentiation.

Disruption to the FOXO-PRDM1 axis resulting from deletions of chromosome 6 in acute lymphoblastic leukaemia

A common problem in the study of human malignancy is the elucidation of cancer driver mechanisms associated with recurrent deletion of regions containing multiple genes. Taking B-cell acute lymphoblastic leukaemia (B-ALL) and large deletions of 6q [del(6q)] as a model, we integrated analysis of functional cDNA clone tracking assays with patient genomic and transcriptomic data, to identify the transcription factors FOXO3 and PRDM1 as candidate tumour suppressor genes (TSG). Analysis of cell cycle and transcriptomic changes following overexpression of FOXO3 or PRDM1 indicated that they co-operate to promote cell cycle exit at the pre-B cell stage. FOXO1 abnormalities are absent in B-ALL, but like FOXO3, FOXO1 expression suppressed growth of TCF3::PBX1 and ETV6::RUNX1 B-ALL in-vitro. While both FOXOs induced PRDM1 and other genes contributing to late pre-B cell development, FOXO1 alone induced the key transcription factor, IRF4, and chemokine, CXCR4. CRISPR-Cas9 screening identified FOXO3 as a TSG, while FOXO1 emerged as essential for B-ALL growth. We relate this FOXO3-specific leukaemia-protective role to suppression of glycolysis based on integrated analysis of CRISPR-data and gene sets induced or suppressed by FOXO1 and FOXO3. Pan-FOXO agonist Selinexor induced the glycolysis inhibitor TXNIP and suppressed B-ALL growth at low dose (ID50 < 50 nM).

Concurrent inactivating mutations and expression losses of RGS2, HNF1A, and CAPN12 candidate tumor suppressor genes in colon cancers.

Microsatellite instability-high (MSI-H) colorectal cancer (CRC) is different from microsatellite stable (MSS) CRC concerning biological, and clinical features. In MSI-H CRCs, defects of mismatch repair genes produce increased mutation accumulation in repetitive DNA sequences. To see whether candidate tumor suppressor genes (TSGs) are altered in MSI-H CRC, we studied frameshift mutation and protein expression of candidate TSGs of RGS2, HNF1A, HNF1B, CAPN12, RCBTB2, ATE1, PKNOX1, and USP19. We found frameshift mutations of RGS2 in 5 (5%), HNF1A in 6 (6%), HNF1B in 2 (2%), CAPN12 in 3 (3%), RCBTB2 in 4 (4%), ATE1 in 2 (2%), PKNOX1 in 2 (2%), and USP19 in 2 (2%) MSI-H CRCs. However, we found no such mutations in MSS CRCs. RCBTB2, CAPN12, HNF1A, and HNF1B frameshift mutations revealed the regional difference in the same tumors. In addition, we identified loss of RGS2, HNF1A, and CAPN12 protein expression irrespective of MSI phenotype in 13-29% of CRCs. The results indicate that many TSGs harbor concurrent inactivating mutations and protein loss in MSI-H CRCs with intratumoral mutational heterogeneity, and that MSS CRCs are altered by protein losses. These alterations could contribute to CRC development and underlying mechanisms and consequences of the TSG alterations remain to be clarified.

Expression of Esophageal Cancer-Related Gene 4: A Candidate Tumor Suppressor Gene Regulated by Methylation Level in Laryngeal Malignant Tumor

To clarify the expression level and methylation level of esophageal cancer related gene 4 in laryngeal malignant tumor and tumor adjacent tissues, and to explore its potential correlation with the clinicopathological characteristics of patients with laryngeal cancer is the objective of the study. The clinical samples were collected from 20 patients with primary laryngeal cancer in Xiangtan Central Hospital from December 2017 to December 2018. The level of expression and methylation of esophageal cancer related gene 4 in the samples were detected by the next-generation sequencing technology. In 15 cases, the messenger ribonucleic acid expression of esophageal cancer related gene 4 of tumor was significantly lower than that in adjacent tissues (p<0.05). In 18 cases, the methylation level of esophageal cancer related gene 4 in tissue of laryngeal squamous carcinoma was 46.7 %, which was significantly higher than that in adjacent tissues (26.2 %, p<0.01). Combined with clinical data analysis, it was found that, in laryngeal high and middle differentiated squamous cell carcinoma, the expression level of esophageal cancer related gene 4 was low and the methylation level was significantly increased. However, the expression of esophageal cancer related gene 4 in small round cell carcinoma was high, while the methylation level was significantly reduced. Smoking and drinking habits are the related factors of laryngeal high and middle differentiated squamous cell carcinoma. These results indicated significant difference of the esophageal cancer related gene 4 expression and methylation level between laryngeal malignant tumor and tumor adjacent tissues. Furthermore, the correlation between esophageal cancer related gene 4 expression and methylation level in laryngeal malignant cancer was found. Esophageal cancer related gene 4 could be regarded as a potential therapeutic target gene for laryngeal malignant cancer.

TMEM196 inhibits lung cancer metastasis by regulating the Wnt/β-catenin signaling pathway.

The TMEM196 protein, which comprises four membrane-spanning domains, belongs to the TMEM protein family. TMEM196 was identified as a candidate tumor suppressor gene in lung cancer. However, its role and mechanism in lungcancer metastasis remain unclear. Here, we study the role of TMEM196 in tumor metastasis to further verify the function in lung cancer. In this study, we used qRT-PCR, western blot analysis and immunohistochemistry to examine the expression levels of TMEM196 and related proteins in lung cancer tissues and tumor cells. We utilized Transwell assays, xenograft nude mouse models, and TMEM196-/- mouse models to evaluate the effects of TMEM196 on tumor invasion and metastasis. Finally, we used bioinformatics analysis and dual-luciferase reporter gene assays to explore the molecular mechanism of TMEM196 as a tumor suppressor. We found that TMEM196 mRNA and protein expression levels were significantly decreased in lung cancer tissues and cells. Low expression of TMEM196 in clinical patients was associated with poor prognosis. TMEM196 strongly inhibited tumor metastasis and progression in vitro and in vivo. The primary lung tumors induced by tail vein-inoculated B16 cells in TMEM196-/- mice were significantly larger than those in TMEM196+/+ mice. Mechanistically, TMEM196 inhibited the Wnt signaling pathway and repressed β-catenin promoter transcription. TMEM196 silencing in lung cancer cells and mice resulted in significant upregulation of the expression of β-catenin and Wnt signaling pathway downstream target genes (MMP2 and MMP7). Decreasing β-catenin expression in TMEM196-silenced cancer cells attenuated the antimetastatic effect of TMEM196. Our results revealed that TMEM196 acts as a novel lung cancer metastasis suppressor via the Wnt/β-catenin signaling pathway.

CSMD1 Shows Complex Patterns of Somatic Copy Number Alterations and Expressions of mRNAs and Target Micro RNAs in Esophageal Squamous Cell Carcinoma.

Simple SummaryHuman Cub and Sushi Multiple Domains 1 (CSMD1) is a novel candidate tumor-suppressor gene. We investigated CSMD1 in esophageal squamous cell carcinoma (ESCC) by performing an integrated analysis of somatic DNA alterations (i.e., copy number alteration, allelic imbalance, and loss of heterozygosity) with RNA expressions (mRNA and target miRNAs) on specimens from the same ESCC patients, using data from SNP, miRNA, and RT-PCR arrays. Our results indicate that the CSMD1 gene may play a role in the development of ESCC through complex patterns involving somatic alterations and mRNA expression. Furthermore, somatic copy number alterations in SNPs located in non-coding regions of CSMD1 appear to influence expression of both this gene and its target miRNAs.Background: Human Cub and Sushi Multiple Domains 1 (CSMD1) is a novel candidate tumor-suppressor gene that codes for multiple domains, including complement regulatory and adhesion proteins, and has recently been shown to have alterations in multiple cancers. We investigated CSMD1 in esophageal squamous cell carcinoma (ESCC) by performing an integrated analysis on somatic copy number alterations (CNAs), including copy-number gain or loss, allelic imbalance (AI), loss of heterozygosity (LOH), and the expressions of mRNA and its target miRNAs on specimens from the same patients with ESCC. Results: (i) Two-thirds of ESCC patients had all three types of alterations studied—somatic DNA alterations in 70%, and abnormal expressions of CSMD1 RNA in 69% and in target miRNAs in 66%; patterns among these alterations were complex. (ii) In total, 97% of 888 CSMD1 SNPs studied showed somatic DNA alterations, with most located near exons 4–11, 24–25, 39–40, 55–56, and 69–70. (iii) In total, 68% of SNPs with a CNA were correlated with expression of CSMD1. (iv) A total of 33 correlations between non-coding SNPs and expression of CSMD1 target miRs were found. Conclusions: Our results indicate that the CSMD1 gene may play a role in ESCC through complex patterns of DNA alterations and RNA and miRNA expressions. Alterations in some somatic SNPs in non-coding regions of CSMD1 appear to influence expression of this gene and its target miRNAs.

Whole genome sequencing reveals the independent clonal origin of multifocal ileal neuroendocrine tumors

BackgroundSmall intestinal neuroendocrine tumors (SI-NETs) are the most common neoplasms of the small bowel. The majority of tumors are located in the distal ileum with a high incidence of multiple synchronous primary tumors. Even though up to 50% of SI-NET patients are diagnosed with multifocal disease, the mechanisms underlying multiple synchronous lesions remain elusive.MethodsWe performed whole genome sequencing of 75 de-identified synchronous primary tumors, 15 metastases, and corresponding normal samples from 13 patients with multifocal ileal NETs to identify recurrent somatic genomic alterations, frequently affected signaling pathways, and shared mutation signatures among multifocal SI-NETs. Additionally, we carried out chromosome mapping of the most recurrent copy-number alterations identified to determine which parental allele had been affected in each tumor and assessed the clonal relationships of the tumors within each patient.ResultsAbsence of shared somatic variation between the synchronous primary tumors within each patient was observed, indicating that these tumors develop independently. Although recurrent copy-number alterations were identified, additional chromosome mapping revealed that tumors from the same patient can gain or lose different parental alleles. In addition to the previously reported CDKN1B loss-of-function mutations, we observed potential loss-of-function gene alterations in TNRC6B, a candidate tumor suppressor gene in a small subset of ileal NETs. Furthermore, we show that multiple metastases in the same patient can originate from either one or several primary tumors.ConclusionsOur study demonstrates major genomic diversity among multifocal ileal NETs, highlighting the need to identify and remove all primary tumors, which have the potential to metastasize, and the need for optimized targeted treatments.

Abstract 46: Independent clonal origins of synchronous primary tumors in multifocal ileal neuroendocrine tumor patients

Abstract Background: Small intestinal neuroendocrine tumors (SI-NETs) are the most common neoplasms of the small bowel, accounting for 40% of all small intestinal malignancies. Previous high-throughput sequencing studies have shown that SI-NETs have a low somatic mutation rate. Loss of heterozygosity (LOH) at chromosome 18 is the most frequent genomic alteration identified, occurring in ~60% of tumors, and the only recurrent mutations reported to date are loss-of-function mutations in CDKN1B in ~10% of tumors. Most previous studies have focused on sequencing a single primary tumor from each SI-NET patient, even though up to 50% of the patients are diagnosed with multiple synchronous tumors. Thus, the mechanisms by which multifocal SI-NETs arise remain elusive. A better understanding of their tumorigenesis is essential for the optimal treatment of the patients. Materials and Methods: We performed a comprehensive genomic profiling of 75 de-identified synchronous primary tumors, 15 metastases, and 18 normal ileal mucosa and/or whole blood specimens from 13 patients with multifocal ileal NETs using whole genome sequencing. Results: We observed lack of shared somatic variation among the multifocal ileal NET patients and between the synchronous primary tumors within each patient, indicating that these tumors develop independently. Although recurrent copy-number alterations were identified, additional chromosome mapping revealed that tumors from the same patient can gain or lose different parental alleles. In addition to the previously reported CDKN1B loss-of-function mutations, we identified potential driver gene alterations in TNRC6B in a subset of ileal NETs. We also observed two different metastatic dissemination patterns among patients with multiple metastases. Metastases were either clonal or independent, originating from one or several primary tumors. Conclusions: Our study demonstrates notable genomic diversity among multifocal ileal NETs, which corroborates previous literature suggesting that these tumors originate independently. We identified potential loss-of-function mutations in TNRC6B, a candidate tumor suppressor gene in a small subset of ileal NETs. Identification of different metastatic dissemination patterns has an important clinical implication, highlighting the need to carefully remove all synchronous primary tumors of the entire jejunum and ileum at the time of surgery. Lastly, our results indicate that the tumorigenesis of multifocal ileal NETs is not exclusively driven by genomic alterations, suggesting that SI-NETs could be also driven by epigenetic mechanisms, or arise from morphologically normal small intestine as a result of field cancerization. Also, the tumor microenvironment in the ileum may play a role in the growth and development of SI-NETs. Citation Format: NETTA MÄKINEN, Meng Zhou, Zhouwei Zhang, Yosuke Kasai, Elizabeth Perez, Grace E. Kim, Chrissie Thirlwell, Eric Nakakura, Matthew Meyerson. Independent clonal origins of synchronous primary tumors in multifocal ileal neuroendocrine tumor patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 46.

Abstract 1452: Analyses of whole exome sequencing (WES) data of hereditary lung cancer families identify germline copy number variations (CNVs) in multiple genes

Abstract Lung cancer (LC) is the most common cause of cancer mortality and the third most common cancer by incidence in the United States. While environmental factors play an important role in its development, LC risk also exhibits a high degree of heritability. Linkage analyses and genome-wide association studies have identified multiple loci associated with increased LC risk; however, much of the heritability has yet to be explained by these loci. Structural mutations, including copy number variations (CNVs), contribute to phenotypic diversity through dosage and/or cis-regulatory effects. Unbiased CNV mapping is only possible with the use of high-depth, short-read sequencing and remains much more complicated and prone to false positives than SNP detection. As the tools necessary for CNV detection have improved, both somatic and germline CNVs have been shown to play an important role in disease, especially cancer, and often they account for a significant proportion of pathogenic variants. Little has been done to understand the role of germline CNVs in the biological pathways of hereditary lung cancer (HLC). The goal of the current project is to utilize the whole exome sequencing (WES) data in identifying the CNVs in the HLC families (≥3 LC/family) recruited by the Genetic Epidemiology of Lung Cancer Consortium (GELCC). This work uses germline WES data from 203 individuals (60 with a LC diagnosis) from 25 HLC families (≥3 LC affected/family). We limited our investigation to CNVs called by two independent tools using read depth to infer copy number changes and genomic breakpoints: GATK 4 (https://gatk.broadinstitute.org) and XHMM (https://atgu.mgh.harvard.edu/xhmm/). We have identified CNVs (deletions) in the following protein coding genes: KIR2DL1 (19q13.42; OR=1.77), DMBT1 (10q26.13; OR=1.56), SIBPB1 (20p13; OR=1.53), LILRA6 (20p13; OR=1.53), and HLA-DRB5 (6p21.32; OR=1.64) in ≥3 families in at least two individuals/family. All of these genes with the exception of HLA-DRB5 were previously reported in LC studies; HLA-DRB5 was reported in other cancer studies. DMBT1 was reported to be a candidate tumor suppressor gene and frequent loss of heterozygosity (LOH) was observed in several human tumors. It is highly expressed in lung and loss of expression was reported in LC cell lines. All CNVs identified in our study are consistent with Mendelian expectations and appear to be uncommon in the general population. CNVs in these genes may contribute to the lung cancer risk in the HLC families. Further validation of the identified variants is ongoing. We will consider overall CNV burden and disease association with identified deletions and duplications. The enrichment of rare variants in oncogenically associated genes that co-segregate with LC provides specific mutations for future work and improves our understanding of the inheritance and pathogenesis of LC. Citation Format: John Waldron, Kirsten W. Termine, Anthony M. Musolf, Mariza de Andrade, Colette Gaba, Ramaswamy Govindan, Ping Yang, Ming You, Ellen Jaeger, Angelle F. Bencaz, Marshall W. Anderson, Ann G. Schwartz, Susan M. Pinney, Christopher I. Amos, Joan E. Bailey-Wilson, Diptasri M. Mandal. Analyses of whole exome sequencing (WES) data of hereditary lung cancer families identify germline copy number variations (CNVs) in multiple genes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1452.

Abstract 2194: Rapid interrogation of colon cancer driver genes in vivo using split Cre and CRISPR-Cas9

Abstract Colorectal cancer (CRC) is the second leading cause of cancer-related deaths worldwide, with a five-year survival rate of only 63% with current treatment regimens. While genetically engineered mouse models (GEMMs) have contributed widely to our understanding of the underlying genetics and molecular mechanisms of the disease, major limitations exist. Most models of CRC lack flexibility to initiate focal adenocarcinomas with different genetic perturbations within the native microenvironment of the distal colon. Specifically, no autochthonous model of metastatic CRC compatible with in vivo CRISPR-Cas9 genome engineering has been described. Therefore, we developed a novel split Cre-recombinase system restricting activation of oncogenic KrasG12D and deletion of the tumor suppressor gene (TSG) Trp53 to Lgr5+ stem cells of the colon crypts. Importantly, these events are not only critical drivers of CRC progression and metastasis in mice and humans but can also lead to non-specific transformation of the surrounding colonic stroma. By expressing one half of Cre from the endogenous Lgr5 locus and other half via colonoscopy-guided submucosal injection of lentivirus, we restricted Cre-mediated recombination to enterocytes. Lentivirus was also engineered to express a single guide RNA (sgRNA) against Apc, facilitating tumor initiation via deletion of this critical CRC TSG in mice expressing Cas9. A second sgRNA was included to facilitate rapid interrogation of putative cancer driver genes. As proof-of-principle, we targeted Smad4, a critical suppressor of metastasis in CRC, and observed adenocarcinoma formation and liver metastases with complete recombination and editing of all targeted genes. To prioritize candidate TSGs for future in vivo interrogation, we applied MutSigCV to large human sequencing datasets and identified genes significantly co-mutated with APC and KRAS in CRC. Altogether, this faithful and tractable model of CRC can be used for rapid functional interrogation of TSGs and should accelerate downstream mechanistic and preclinical studies. Citation Format: Daniel Zhang, Peter Westcott, Santiago Naranjo, Haley Hauck, William Rideout, Nate Sacks, Arjun Bhutkar, Justin Patten, Norihiro Goto, Joseph Sedlak, Tyler Jacks. Rapid interrogation of colon cancer driver genes in vivo using split Cre and CRISPR-Cas9 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2194.