Search

Epithelial-to-mesenchymal transition results in loss of specialized epithelial cell contacts and acquisition of mesenchymal invasive capacity. The transcription repressor zinc finger E-box-binding homeobox 1 (ZEB1) binds to E-boxes of gene promoter regions to suppress the expression of epithelial genes. ZEB1 has inconsistent molecular weights, which have been attributed to posttranslational modifications (PTM). We performed mass spectrometry and identified K811 acetylation as a novel PTM in ZEB1. To define the role of ZEB1 acetylation in regulating function, we generated ZEB1 acetyl-mimetic (K811Q) and acetyl-deficient (K811R) mutant-expressing non–small cell lung cancer cell lines (NSCLC). We demonstrate that the K811R ZEB1 (125 kDa) has a shorter protein half-life than wild-type (WT) ZEB1 and K811Q ZEB1 (∼225 kDa), suggesting that lack of ZEB1 acetylation in the lower molecular weight form affects protein stability. Further, the acetylated form of ZEB1 recruits the nucleosome remodeling and deacetylase (NuRD) complex to bind the promoter of its target genes mir200c-141 and SEMA3F. RNA-sequencing revealed that WT ZEB1 and K811Q ZEB1 downregulate the expression of epithelial genes to promote lung adenocarcinoma invasion and metastasis, whereas the K811R ZEB1 does not. Our findings establish that the K811 acetylation promotes ZEB1 protein stability, interaction with other protein complexes, and subsequent invasion/metastasis of lung adenocarcinoma via epithelial-to-mesenchymal transition. Implications: The molecular mechanisms by which ZEB1 is regulated by K811 acetylation to promote protein stability, NuRD complex and promoter interactions, and function are relevant to the development of treatment strategies to prevent and treat metastasis in patients with NSCLC.

Potential ZEB1 acetylation-dependent target genes.

qPCR Primer Sequences

Antibody information

S1. K811 acetylation is integral to ZEB1 molecular weight. S2. &tilde225 kDa ZEB1 band regulates protein stability. S3. K811 acetylation facilitates ZEB1/NuRD interaction. S4. K811 acetylation directs the ZEB1/NuRD complex to bind at genomic promoters. S5. K811 acetylation decreased epithelial expression levels. S6. RNA-seq reveals K811 acetylation downregulates the expression of epithelial genes. S7. K811 acetylation in ZEB1 KO cells promotes lung adenocarcinoma migration and invasion. S8. K811 acetylation enhances metastatic potential of murine NSCLC cells.

Epithelial-to-mesenchymal transition results in loss of specialized epithelial cell contacts and acquisition of mesenchymal invasive capacity. The transcription repressor zinc finger E-box-binding homeobox 1 (ZEB1) binds to E-boxes of gene promoter regions to suppress the expression of epithelial genes. ZEB1 has inconsistent molecular weights, which have been attributed to posttranslational modifications (PTM). We performed mass spectrometry and identified K811 acetylation as a novel PTM in ZEB1. To define the role of ZEB1 acetylation in regulating function, we generated ZEB1 acetyl-mimetic (K811Q) and acetyl-deficient (K811R) mutant-expressing non–small cell lung cancer cell lines (NSCLC). We demonstrate that the K811R ZEB1 (125 kDa) has a shorter protein half-life than wild-type (WT) ZEB1 and K811Q ZEB1 (∼225 kDa), suggesting that lack of ZEB1 acetylation in the lower molecular weight form affects protein stability. Further, the acetylated form of ZEB1 recruits the nucleosome remodeling and deacetylase (NuRD) complex to bind the promoter of its target genes mir200c-141 and SEMA3F. RNA-sequencing revealed that WT ZEB1 and K811Q ZEB1 downregulate the expression of epithelial genes to promote lung adenocarcinoma invasion and metastasis, whereas the K811R ZEB1 does not. Our findings establish that the K811 acetylation promotes ZEB1 protein stability, interaction with other protein complexes, and subsequent invasion/metastasis of lung adenocarcinoma via epithelial-to-mesenchymal transition.Implications:The molecular mechanisms by which ZEB1 is regulated by K811 acetylation to promote protein stability, NuRD complex and promoter interactions, and function are relevant to the development of treatment strategies to prevent and treat metastasis in patients with NSCLC.

Protein expression values of the immunoprecipitated samples

ChIP Primer Sequences

One of the mechanisms by which cancer cells acquire hyperinvasive and migratory properties with progressive loss of epithelial markers is the epithelial-to-mesenchymal transition (EMT). We have previously reported that in different cancer types, including nonsmall cell lung cancer (NSCLC), the microRNA-183/96/182 cluster (m96cl) is highly repressed in cells that have undergone EMT. In the present study, we used a novel conditional m96cl mouse to establish that loss of m96cl accelerated the growth of Kras mutant autochthonous lung adenocarcinomas. In contrast, ectopic expression of the m96cl in NSCLC cells results in a robust suppression of migration and invasion in vitro, and tumor growth and metastasis in vivo. Detailed immune profiling of the tumors revealed a significant enrichment of activated CD8+ cytotoxic T lymphocytes (CD8+ CTLs) in m96cl-expressing tumors, and m96cl-mediated suppression of tumor growth and metastasis was CD8+ CTL-dependent. Using coculture assays with naïve immune cells, we show that m96cl expression drives paracrine stimulation of CD8+ CTL proliferation and function. Using tumor microenvironment-associated gene expression profiling, we identified that m96cl elevates the interleukin-2 (IL2) signaling pathway and results in increased IL2-mediated paracrine stimulation of CD8+ CTLs. Furthermore, we identified that the m96cl modulates the expression of IL2 in cancer cells by regulating the expression of transcriptional repressors Foxf2 and Zeb1, and thereby alters the levels of secreted IL2 in the tumor microenvironment. Last, we show that in vivo depletion of IL2 abrogates m96cl-mediated activation of CD8+ CTLs and results in loss of metastatic suppression. Therefore, we have identified a novel mechanistic role of the m96cl in the suppression of lung cancer growth and metastasis by inducing an IL2-mediated systemic CD8+ CTL immune response.

One of the mechanisms by which cancer cells acquire hyperinvasive and migratory properties with progressive loss of epithelial markers is the epithelial-to-mesenchymal transition (EMT). We have previously reported that in different cancer types, including nonsmall cell lung cancer (NSCLC), the microRNA-183/96/182 cluster (m96cl) is highly repressed in cells that have undergone EMT. In the present study, we used a novel conditional m96cl mouse to establish that loss of m96cl accelerated the growth of Kras mutant autochthonous lung adenocarcinomas. In contrast, ectopic expression of the m96cl in NSCLC cells results in a robust suppression of migration and invasion in vitro, and tumor growth and metastasis in vivo. Detailed immune profiling of the tumors revealed a significant enrichment of activated CD8

Lung cancer is a highly aggressive and metastatic disease responsible for approximately 25% of all cancer-related deaths in the United States. Using high-throughput in vitro and in vivo screens, we have previously established Impad1 as a driver of lung cancer invasion and metastasis. Here we elucidate that Impad1 is a direct target of the epithelial microRNAs (miRNAs) miR-200 and miR∼96 and is de-repressed during epithelial-to-mesenchymal transition (EMT); thus, we establish a mode of regulation of the protein. Impad1 modulates Golgi apparatus morphology and vesicular trafficking through its interaction with a trafficking protein, Syt11. These changes in Golgi apparatus dynamics alter the extracellular matrix and the tumor microenvironment (TME) to promote invasion and metastasis. Inhibiting Impad1 or Syt11 disrupts the cancer cell secretome, regulates the TME, and reverses the invasive or metastatic phenotype. This work identifies Impad1 as a regulator of EMT and secretome-mediated changes during lung cancer progression.

Metastasis is the cause for 90% of cancer-related mortalities. Identification of genetic drivers promoting dissemination of tumor cells may provide opportunities for novel therapeutic strategies. We previously reported an in vivo gain-of-function screen that identified ∼30 genes with a functional role in metastasis promotion and characterized detailed mechanistic functions of two hits. In the present study, we characterized the contribution of one of the identified genes, MBIP (MAP3K12 binding inhibitory protein), towards driving tumor invasion and metastasis. We demonstrate that expression of MBIP significantly enhances the cellular proliferation, migration and invasion of NSCLC cells in vitro and metastasis in vivo. We functionally characterized that MBIP mediates activation of the JNK pathway and induces expression of matrix metalloproteinases (MMPs), which are necessary for the invasive and metastatic phenotype. Our findings establish a novel mechanistic role of MBIP as a driver of NSCLC progression and metastasis.

// C. Allison Stewart 1 , Pan Tong 2 , Robert J. Cardnell 1 , Triparna Sen 1 , Lerong Li 2 , Carl M. Gay 1 , Fatemah Masrorpour 1 , You Fan 1 , Rasha O. Bara 1 , Ying Feng 3 , Yuanbin Ru 3 , Junya Fujimoto 4 , Samrat T. Kundu 1 , Leonard E. Post 3 , Karen Yu 3 , Yuqiao Shen 3 , Bonnie S. Glisson 1 , Ignacio Wistuba 4 , John V. Heymach 1 , Don L. Gibbons 1 , Jing Wang 2 and Lauren Averett Byers 1 1 Department of Thoracic Head & Neck Medical Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA 2 Department of Bioinformatics and Computational Biology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA 3 BioMarin Pharmaceutical, San Rafael, CA 94901, USA 4 Department of Translational Molecular Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA Correspondence to: Lauren Averett Byers, email: lbyers@mdanderson.org Keywords: SCLC, SLFN11, ATM, EMT, PARP inhibitor Received: December 10, 2016 Accepted: January 19, 2017 Published: February 15, 2017 ABSTRACT Small cell lung cancer (SCLC) is one of the most aggressive forms of cancer, with a 5-year survival

Mitogen-activated protein kinase kinase (MEK) inhibitors have failed to show clinical benefit in Kirsten rat sarcoma (KRAS)-mutant lung cancer due to various resistance mechanisms. To identify differential therapeutic sensitivities between epithelial and mesenchymal lung tumors, we performed in vivo small hairpin RNA (shRNA) screens, proteomic profiling, and analysis of patient tumor datasets, which revealed an inverse correlation between mitogen-activated protein kinase (MAPK) signaling dependency and a zinc finger E-box-binding homeobox 1 (ZEB1)-regulated epithelial-to-mesenchymal transition (EMT). Mechanistic studies determined that MAPK signaling dependency in epithelial lung cancer cells is due to the scaffold protein interleukin 17 receptor D (IL17RD), which is directly repressed by ZEB1. Lung tumors in multiple Kras mutant murine models with increased ZEB1 displayed low IL17RD expression, accompanied by MAPK-independent tumor growth and therapeutic resistance to MEK inhibition. Suppression of ZEB1 function with miR-200 expression or the histone deacetylase (HDAC) inhibitor mocetinostat sensitized resistant cancer cells to MEK inhibition and markedly reduced in vivo tumor growth, showing a promising combinatorial treatment strategy for KRAS-mutant cancers. In human lung tumor samples, high ZEB1 and low IL17RD expression correlated with low MAPK signaling, presenting potential markers that predict patient response to MEK inhibitors.

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death worldwide, due in part to the propensity of lung cancer to metastasize. Aberrant epithelial-to-mesenchymal transition (EMT) is a proposed model for the initiation of metastasis. During EMT cell-cell adhesion is reduced allowing cells to dissociate and invade. Of the EMT-associated transcription factors, ZEB1 uniquely promotes NSCLC disease progression. Here we apply two independent screens, BioID and an Epigenome shRNA dropout screen, to define ZEB1 interactors that are critical to metastatic NSCLC. We identify the NuRD complex as a ZEB1 co-repressor and the Rab22 GTPase-activating protein TBC1D2b as a ZEB1/NuRD complex target. We find that TBC1D2b suppresses E-cadherin internalization, thus hindering cancer cell invasion and metastasis., Non-small cell lung cancer (NSCLC) is often associated with metastasis to the lungs. Here, the authors perform independent screens and identify NuRD as a co-repressor of ZEB1, and demonstrate TBC1D2b as a downstream target of ZEB1/NuRD complex regulating NSCLC metastasis.

Metastatic lung cancer is one of the most lethal forms of cancer and molecular pathways driving metastasis are still not clearly elucidated. Metastatic cancer cells undergo an epithelial-mesenchymal transition (EMT) where they lose their epithelial properties and acquire a migratory and invasive phenotype. Here we identify that expression of microRNAs from the miR-200 family and the miR-183~96~182 cluster are significantly co-repressed in non-small cell lung cancer (NSCLC) cell lines and primary tumors from multiple TCGA data sets with high EMT scores. Ectopic expression of the miR-183~96~182 cluster inhibited cancer cell migration and invasion, while its expression was tightly modulated by miR-200. We identified Foxf2 as a common, novel and direct target of both these microRNA families. Foxf2 expression tightly correlates with the transcription factor Zeb1 and is elevated in mesenchymal-like metastatic lung cancer cells. Foxf2 expression induced robust EMT, migration, invasion and metastasis in lung cancer cells, whereas Foxf2 inhibition significantly repressed these phenotypes. We also demonstrated that Foxf2 transcriptionally represses E-Cadherin and miR-200, independent of Zeb1, to form a double negative feedback loop. We therefore identified a novel mechanism whereby the miR-200 family and the miR-183~96~182 cluster inhibit lung cancer invasion and metastasis by targeting Foxf2.

Keratin expression in stratified epithelia is tightly regulated during squamous cell differentiation. Keratins 5 and 14 are expressed in mitotically active basal layer cells, but their function is not well defined. Reported here is the possible role of K14 in regulation of cell proliferation/differentiation in stratified epithelial cells., Keratins are cytoplasmic intermediate filament proteins preferentially expressed by epithelial tissues in a site-specific and differentiation-dependent manner. The complex network of keratin filaments in stratified epithelia is tightly regulated during squamous cell differentiation. Keratin 14 (K14) is expressed in mitotically active basal layer cells, along with its partner keratin 5 (K5), and their expression is down-regulated as cells differentiate. Apart from the cytoprotective functions of K14, very little is known about K14 regulatory functions, since the K14 knockout mice show postnatal lethality. In this study, K14 expression was inhibited using RNA interference in cell lines derived from stratified epithelia to study the K14 functions in epithelial homeostasis. The K14 knockdown clones demonstrated substantial decreases in the levels of the K14 partner K5. These cells showed reduction in cell proliferation and delay in cell cycle progression, along with decreased phosphorylated Akt levels. K14 knockdown cells also exhibited enhanced levels of activated Notch1, involucrin, and K1. In addition, K14 knockdown AW13516 cells showed significant reduction in tumorigenicity. Our results suggest that K5 and K14 may have a role in maintenance of cell proliferation potential in the basal layer of stratified epithelia, modulating phosphatidylinositol 3-kinase/Akt–mediated cell proliferation and/or Notch1-dependent cell differentiation.

A decrease in the levels of the desmosomal plaque protein, plakophilin3 (PKP3), leads to a decrease in desmosome size and cell-cell adhesion. To test the hypothesis that PKP3 is required for desmosome formation, the recruitment of desmosomal components to the cell surface was studied in the PKP3 knockdown clones. The PKP3 knockdown clones showed decreased cell border staining for multiple desmosomal proteins, when compared to vector controls, and did not form desmosomes in a calcium switch assay. Further analysis demonstrated that PKP3, plakoglobin (PG) and E-cadherin are present at the cell border at low concentrations of calcium. Loss of either PG or E-cadherin led to a decrease in the levels of PKP3 and other desmosomal proteins at the cell border. The results reported here are consistent with the model that PG and E-cadherin recruit PKP3 to the cell border to initiate desmosome formation.

Mitotic progression requires the activity of the dual specificity phosphatase, cdc25C. Cdc25C function is inhibited by complex formation with two 14-3-3 isoforms, 14-3-3epsilon and 14-3-3gamma. To understand the molecular basis of specific complex formation between 14-3-3 proteins and their ligands, chimeric 14-3-3 proteins were tested for their ability to form a complex with cdc25C in vivo. Specific complex formation between cdc25C and 14-3-3epsilon in vivo requires a phenylalanine residue at position 135 (F135) in 14-3-3epsilon. Mutation of this residue to the corresponding residue present in other 14-3-3 isoforms (F135V) leads to reduced binding to cdc25C and a decrease in the ability to inhibit cdc25C function in vivo. Similarly, F135V failed to rescue the incomplete S phase and the G2 DNA damage checkpoint defects observed in cells lacking 14-3-3epsilon. A comparative analysis of the 14-3-3 structures present in the database suggested that the F135 in 14-3-3epsilon was required to maintain the integrity of a pocket that might be involved in secondary interactions with cdc25C. These results suggest that the specificity of the 14-3-3 ligand interaction may be dependent on structural motifs present in the individual 14-3-3 isoforms.

Metastatic lung cancer is the leading cause of cancer related death in the world and novel approaches are necessary to elucidate specific genes that drive lung cancer progression and metastasis. Lung cancers commonly demonstrate genetic alteration of potent drivers like Kras, p53 or EGFR accompanied with hundreds of low frequency gene aberrations which are a mix of key driver events and nascent passenger mutations. We established a robust screening platform to selectively identify these functionally critical “driver” genes in lung cancers from a prioritized list of candidates selected by a multi-level cross-species comparison of our published high confidence transcriptome data from genetically-engineered mouse models and genomic data of human lung cancers from TCGA, focusing on elevated gene expression and/or gene amplification. We identified 225 putative candidate driver genes which were used to construct a lentiviral based cDNA expression library with unique molecular barcoding of individual cDNAs. Using a non-metastatic syngeneic mouse lung cancer model we generated individually transduced stable over-expressing lines for each gene. These candidate lines were used for a unique in vivo positive selection screen to identify functional metastasis drivers. We transplanted pools of 20 cDNA expressing lines into syngeneic mice and observed for primary tumor growth and occurrence of metastases in lungs and other organs. Metastatic drivers were identified by the relative enrichment of the unique barcode sequences in the genomic DNA from metastatic lesions over primary tumors. We have identified both known (e.g. MYC) and several novel (e.g. THRA, TMEM106B, GNAS) potential oncogenic and metastatic drivers. We validated our top hits for their individual in vivo metastatic potencies by gain-of-function/loss-of-function studies and identified TMEM106B as one of the primary drivers of metastasis. TMEM106B is a transmembrane protein localizing to the lysosomes and has been shown to drive expression of lysosomal genes. We hypothesize that elevated levels of TMEM106B is able to drive the expression and secretion of lysosomal enzymes thus making cancer cells hyper invasive and metastatic. We found strong correlation for expression of TMEM106B with several lysosomal genes in a panel of 1016 human lung cancers and are currently performing in depth studies to understand these mechanisms of TMEM106B driven metastasis. We are also analyzing the clinical relevance of TMEM106B based upon their expression pattern and prognostic utility across TCGA and other public datasets, along with in-house patient samples and tissue microarrays of resected and biopsy specimens. Identification of such novel players will significantly advance the field of cancer target discovery by identifying new drug targets and biomarkers, essential for effective treatment options for lung cancer patients. Citation Format: Samrat Kundu, Caitlin Grzeskowiak, Chad J. Creighton, Kenneth L. Scott, Don L. Gibbons. Identifying TMEM106B as a novel metastasis driver in non-small cell lung cancers through an in vivo gain-of-function screen. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 688.

s: AACR Special Conference on Tumor Metastasis; November 30-December 3, 2015; Austin, TX Metastatic lung cancer is the leading cause of cancer related mortality in the world. Insights on specific genetic causes are limited and novel approaches are necessary to elucidate specific genes that drive lung cancer progression and metastasis. Extensive genomic and transcriptomic profiling of human lung cancers by consortia like ‘The Cancer Genome Atlas’ (TCGA) and the ‘International Cancer Genome Consortium’ (ICGC) has revealed a complex genetic landscape marked by abundant aberrations. In addition to acquiring mutations or amplification of well documented drivers like Kras, p53 or EGFR, lung cancers also demonstrate an enrichment of hundreds of low frequency gene aberrations which are a mix of key driver mutations and nascent passenger alterations caused by progressive genomic instability that could have definite role in cancer progression and metastasis. Our goal was to establish a robust screening platform to selectively identify these functionally critical “driver” genes in lung cancers. To identify a prioritized list of potential candidates we performed a multi-level cross-species comparison of our published high confidence transcriptome data from genetically-engineered mouse models of lung cancers and human lung cancer genomic data from TCGA, focusing on elevated gene expression and/or gene amplification. We identified an enriched list of 225 putative driver genes in lung cancers which were used to construct a lentiviral based cDNA expression library with unique molecular barcoding of individual cDNAs. Using a non-metastatic syngeneic mouse lung cancer model we generated individually transduced stable over-expressing lines for each of the 225 genes. These candidate lines were then entered into parallel in vitro and in vivo screens. In vitro testing includes cell invasion assays in a 96-well format, with positive hits defined as those scoring above 3x standard deviations relative to the control cells expressing mCherry. Positive hits were revalidated using standard 24-well invasion assays and also studied for growth phenotypes in 3D cultures. To selectively identify genes with functional role in metastasis, we performed a unique in vivo positive selection screen to test individual and combinatorial effects of lung cancer driver aberrations. For this we used pools of 20 cDNA expressing lines transplanted into syngeneic mice and observed for primary tumor growth and occurrence of metastases in lungs and other organs. Metastatic lesions and primary tumors were collected and genomic DNA from these was used to identify the unique individual barcodes by NGS barcode enrichment analysis. Metastatic drivers were identified by the relative enrichment of the unique barcode sequences for all the respective pool cDNAs in the metastatic tissue. We have identified both known (e.g. MYC) and several novel (e.g. THRA, TMEM106B, GNAS) potential oncogenic and metastatic drivers from the pooled screen which are currently being revalidated for their individual in vivo metastatic potencies. We are performing gain-of-function/loss-of-function studies for the identified driver genes to determine the pathways which they regulate. We are also analyzing the clinical relevance of these genes based upon their expression pattern and prognostic utility across TCGA and other public datasets, along with in-house patient samples and tissue microarrays of resected and biopsy specimens. Our unique high through-put approach will significantly advance the field of cancer target discovery by identifying new drug targets and biomarkers, essential for novel effective treatment options for lung cancer patients. Citation Format: Samrat T. Kundu, Caitlin Grzeskowiak, Chad J. Creighton, Kenneth L. Scott, Don L. Gibbons. A novel in vivo gain-of-function screen for metastasis drivers in non-small cell lung cancers. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr B25.

The KRAS-variant is a germline single nucleotide polymorphism (SNP) within the 3'UTR of the KRAS gene predicted to disrupt a complementary binding site (LCS6) for the let-7 microRNA (miRNA). The KRAS-variant is associated with increased risk of various cancers, including lung cancer, ovarian cancer and triple-negative breast cancer, and is associated with altered tumor biology in head and neck cancer, colon cancer and melanoma. To better understand the molecular pathways that may be regulated or affected by the presence of the KRAS-variant allele in cancer cells, we examined its prevalence in the NCI-60 panel of cell lines and sought to identify common features of the cell lines that carry the variant allele. This study provides a step forward towards understanding the molecular and pathological significance of the KRAS-variant.

Keratins 8 and 18 (K8 and K18) are predominantly expressed in simple epithelial tissues and perform both mechanical and regulatory functions. Aberrant expression of K8 and K18 is associated with neoplastic progression and invasion in squamous cell carcinomas (SCCs). To understand the molecular basis by which K8 promotes neoplastic progression in oral SCC (OSCC), K8 expression was inhibited in AW13516 cells. The K8-knockdown clones showed a significant reduction in tumorigenic potential, which was accompanied by a reduction in cell motility, cell invasion, decreased fascin levels, alterations in the organization of the actin cytoskeleton and changes in cell shape. Furthermore, K8 knockdown led to a decrease in α6β4 integrin levels and α6β4-integrin-dependent signalling events, which have been reported to play an important role in neoplastic progression in epithelial tissues. Therefore, modulation of α6β4 integrin signalling might be one of the mechanisms by which K8 and K18 promote malignant transformation and/or progression in OSCCs.

Plakophilin3 is a desmosomal plaque protein whose levels are reduced in poorly differentiated tumors of the oropharyngeal cavity and in invasive colon carcinomas. To test the hypothesis that plakophilin3 loss stimulates neoplastic progression, plakophilin3 expression was inhibited by DNA vector driven RNA interference in 3 epithelial cell lines, HCT116, HaCaT and fetal buccal mucosa. The plakophilin3-knockdown clones showed a decrease in cell-cell adhesion as assessed in a hanging drop assay, which was accompanied by an increase in cell migration. The HCT116 plakophilin3-knockdown clones showed a decrease in desmosome size as revealed by electron microscopy. These altered desmosomal properties were accompanied by colony formation in soft agar and growth to high density in culture. The HCT116-derived clones showed accelerated tumor formation in nude mice and increased metastasis to the lung, a phenotype consistent with the increased migration observed in vitro and is consistent with data from human tumors that suggests that plakophililn3 is lost in invasive and metastatic tumors. These data indicate that plakophilin3 loss leads to a decrease in cell-cell adhesion leading to the stimulation of neoplastic progression and metastasis.

Large-scale profiling efforts by consortia such as The Cancer Genome Atlas (TCGA) are revealing the complexity of cancer genomes, which are comprised of causal “driver” aberrations and many biologically neutral “passengers”. Most cancers acquire one or more well-studied high frequency driver events that promote tumor growth (e.g., mutations/copy number changes in KRAS, TP53, EGFR, MYC). Much less is known about the thousands of low frequency gene aberrations and their contribution to cancer progression, particularly metastasis, which is the primary cause of cancer-related mortality. Comprehensive biological assessment of low frequency metastasis drivers is difficult given their large number and the fact that their activity may be influenced by the specific biological context of a given cancer such as tissue type, microenvironment, and the host immune system. We sought to address these challenges in the context of lung cancer, which presents as metastatic disease in approximately 65% of patients and carries a 5-year survival rate of 35,000 sequence verified human gene clones (2) a molecular barcoding strategy that permits simultaneous DNA tagging of gene clones through multi-fragment DNA recombineering for (3) pooled functional screening in vivo to identify metastasis drivers that work alone or in combination. We used these technologies to build gene libraries based on oncogenomics-guided integrations of mutant KRAS-specific gene signatures derived from mouse and human TCGA lung cancer datasets. The resulting barcoded libraries were delivered to non-metastatic lung cancer cells expressing oncogenic KRAS and then implanted into immune competent mice. Animals were sacrificed at maximal tumor burden and resulting primary tumors and metastases subjected to barcode enrichment analysis by next generation sequencing to identify gene aberrations enriched within metastatic lesions. Our screening approach has identified known (MYC and SNAI2) and many novel (e.g., MBIP and CCNE1) potent drivers of lung cancer growth and metastasis currently under mechanistic and pre-clinical evaluation. These efforts are revealing new pathways contributing to lung cancer aggression and our ultimate goal is to translate these findings into the care of metastatic lung cancer patients who have few treatment options. We have also scaled these efforts across other screening platforms, functionalizing thousands of aberrations across diverse cancer types. Together these systems reveal the highest priority targets to enroll in deep mechanistic biology studies and drug discovery and development programs. Citation Format: Caitlin L. Grzeskowiak, Rosalba Minelli, Ping Wu, Samrat Kundu, Don L. Gibbons, Kenneth L. Scott. High-throughput functional screening for metastasis drivers of lung cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 955. doi:10.1158/1538-7445.AM2015-955

MicroRNAs (miRNAs) are small non-coding RNAs that regulate the expression of numerous target genes. Yet, while hundreds of miRNAs have been identified, little is known about their functions. In a recent report published in Silence, Zheng and colleagues demonstrate a technique for robust and specific knockdown of miRNA expression in Caenorhabditis elegans using modified antisense oligonucleotides, which could be utilized as a powerful tool for the study of regulation and function of miRNAs in vivo. See research article http://www.silencejournal.com/content/1/1/9