Development of Kras mutant lung adenocarcinoma in mice with knockout of the airway lineage-specific gene Gprc5a

Immunogenic dying cells elicit potent anti-tumor T cell immunity against lung metastasis and tumorigenesis

PURPOSE

Immune checkpoint blockades (ICBs) are promising, however they do not fit all types of tumor, such as those lack of tumor antigens. Induction of potent anti-tumor T cell immunity is critical for cancer therapy. In this study, we investigated the efficacy of immunotherapy via the immunogenic cell death (ICD) dying tumor cells in mouse models of lung metastasis and tumorigenesis.

METHODS

ICD was induced by short exposure to lethal dose of chemotherapeutic drug doxorubicin (Dox), which initiated an irreversible ICD program in tumor cells. We immunized mice with ICD dying tumor cells in prevention, therapy in lung metastasis models, and Gprc5a-knockout (ko) model of lung tumorigenesis. T cells and macrophages isolated from lymph nodes or tumor tissues were analyzed by flow cytometry. Cytokines were analyzed by ELISA or Q-PCR analysis.

RESULTS

Immunization with these live but ICD dying tumor cells induced potent tumor-specific anti-tumor T cell immunity, which not only protected host from challenge by these tumor cells in prevention and therapy in mouse model of lung metastasis, but also prevented tumors development in Gprc5a-ko mouse model of lung tumorigenesis. The lymphocytes from lymph nodes and tumor tissues exhibited greatly enhanced activities of Th1 cells and M1 macrophages.

CONCLUSION

Immunization with the ICD dying tumor cells evokes potent tumor-specific T cell immunity, which provides a novel approach for cancer immunotherapy.

Inflammation Mediated by Gut Microbiome Alterations Promotes Lung Cancer Development and an Immunosuppressed Tumor Microenvironment

Accumulating evidence indicates that the gut microbiome influences cancer progression and therapy. We recently showed that progressive changes in gut microbial diversity and composition are closely coupled with tobacco-associated lung adenocarcinoma in a human-relevant mouse model. Furthermore, we demonstrated that the loss of the antimicrobial protein Lcn2 in these mice exacerbates protumor inflammatory phenotypes while further reducing microbial diversity. Yet, how gut microbiome alterations impinge on lung adenocarcinoma development remains poorly understood. In this study, we investigated the role of gut microbiome changes in lung adenocarcinoma development using fecal microbiota transfer and delineated a pathway by which gut microbiome alterations incurred by loss of Lcn2 fostered the proliferation of proinflammatory bacteria of the genus Alistipes, triggering gut inflammation. This inflammation propagated systemically, exerting immunosuppression within the tumor microenvironment, augmenting tumor growth through an IL6-dependent mechanism and dampening response to immunotherapy. Corroborating our preclinical findings, we found that patients with lung adenocarcinoma with a higher relative abundance of Alistipes species in the gut showed diminished response to neoadjuvant immunotherapy. These insights reveal the role of microbiome-induced inflammation in lung adenocarcinoma and present new potential targets for interception and therapy.

Premalignant Progression in the Lung: Knowledge Gaps and Novel Opportunities for Interception of Non-Small Cell Lung Cancer. An Official American Thoracic Society Research Statement

Rationale: Despite significant advances in precision treatments and immunotherapy, lung cancer is the most common cause of cancer death worldwide. To reduce incidence and improve survival rates, a deeper understanding of lung premalignancy and the multistep process of tumorigenesis is essential, allowing timely and effective intervention before cancer development. Objectives: To summarize existing information, identify knowledge gaps, formulate research questions, prioritize potential research topics, and propose strategies for future investigations into the premalignant progression in the lung. Methods: An international multidisciplinary team of basic, translational, and clinical scientists reviewed available data to develop and refine research questions pertaining to the transformation of premalignant lung lesions to advanced lung cancer. Results: This research statement identifies significant gaps in knowledge and proposes potential research questions aimed at expanding our understanding of the mechanisms underlying the progression of premalignant lung lesions to lung cancer in an effort to explore potential innovative modalities to intercept lung cancer at its nascent stages. Conclusions: The identified gaps in knowledge about the biological mechanisms of premalignant progression in the lung, together with ongoing challenges in screening, detection, and early intervention, highlight the critical need to prioritize research in this domain. Such focused investigations are essential to devise effective preventive strategies that may ultimately decrease lung cancer incidence and improve patient outcomes.

An atlas of epithelial cell states and plasticity in lung adenocarcinoma

Understanding the cellular processes that underlie early lung adenocarcinoma (LUAD) development is needed to devise intervention strategies1. Here we studied 246,102 single epithelial cells from 16 early-stage LUADs and 47 matched normal lung samples. Epithelial cells comprised diverse normal and cancer cell states, and diversity among cancer cells was strongly linked to LUAD-specific oncogenic drivers. KRAS mutant cancer cells showed distinct transcriptional features, reduced differentiation and low levels of aneuploidy. Non-malignant areas surrounding human LUAD samples were enriched with alveolar intermediate cells that displayed elevated KRT8 expression (termed KRT8+ alveolar intermediate cells (KACs) here), reduced differentiation, increased plasticity and driver KRAS mutations. Expression profiles of KACs were enriched in lung precancer cells and in LUAD cells and signified poor survival. In mice exposed to tobacco carcinogen, KACs emerged before lung tumours and persisted for months after cessation of carcinogen exposure. Moreover, they acquired Kras mutations and conveyed sensitivity to targeted KRAS inhibition in KAC-enriched organoids derived from alveolar type 2 (AT2) cells. Last, lineage-labelling of AT2 cells or KRT8+ cells following carcinogen exposure showed that KACs are possible intermediates in AT2-to-tumour cell transformation. This study provides new insights into epithelial cell states at the root of LUAD development, and such states could harbour potential targets for prevention or intervention.

Alveolar type I cells can give rise to KRAS-induced lung adenocarcinoma

Lung adenocarcinoma (LUAD) is the most prevalent subtype of lung cancer and presents clinically with a high degree of biological heterogeneity and distinct clinical outcomes. The current paradigm of LUAD etiology posits alveolar epithelial type II (AT2) cells as the primary cell of origin, while the role of AT1 cells in LUAD oncogenesis remains unknown. Here, we examine oncogenic transformation in mouse Gram-domain containing 2 (Gramd2)+ AT1 cells via oncogenic KRASG12D. Activation of KRASG12D in AT1 cells induces multifocal LUAD, primarily of papillary histology. Furthermore, KRT8+ intermediate cell states were observed in both AT2- and AT1-derived LUAD, but SCGB3A2+, another intermediate cell marker, was primarily associated with AT1 cells, suggesting different mechanisms of tumor evolution. Collectively, our study reveals that Gramd2+ AT1 cells can serve as a cell of origin for LUAD and suggests that distinct subtypes of LUAD based on cell of origin be considered in the development of therapeutics.

Hypermethylation of the ADIRF promoter regulates its expression level and is involved in NNK-induced malignant transformation of lung bronchial epithelial cells

The carcinogenic mechanism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a well-known tobacco carcinogen, has not been fully elucidated in epigenetic studies. 5-Methylcytosine (5mC) modification plays a major role in epigenetic regulation. In this study, the 5mC level increased in both BEAS-2B human bronchial epithelium cells treated with 100 mg/L NNK for 24 h and NNK-induced malignant-transformed BEAS-2B cells (2B-NNK cells), suggesting that 5mC modification is associated with the malignant transformation mechanism of NNK. Using a combination of Methylated DNA Immunoprecipitation Sequencing (MeDIP-seq), RNA sequencing (RNA-seq), and bioinformatics analysis of data from the Genomic Data Commons database, we found that the Adipogenesis regulatory factor (ADIRF) promoter region was abnormally hypermethylated, yielding low ADIRF mRNA expression, and that ADIRF overexpression could inhibit the proliferation, migration, and invasion of 2B-NNK cells. This finding suggests that ADIRF plays a tumor suppressor role in the NNK-induced malignant transformation of cells. Subsequently, using 5-Aza-2'-deoxycytidine (5-Aza-2'-dC) and the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Catalytically Dead Cas9 (dCas9 system), we verified that the demethylation of the ADIRF promoter region in 2B-NNK cells inhibited the proliferation, migration, and invasion ability of the cells and increased their apoptosis ability. These results suggest that abnormal 5mC modification of the ADIRF promoter plays a positive regulatory role in the pathogenesis of NNK-induced lung cancer. This study offers a new experimental basis for the epigenetic mechanism of NNK-induced lung cancer.

The G protein-coupled receptor GPRC5A-a phorbol ester and retinoic acid-induced orphan receptor with roles in cancer, inflammation, and immunity

GPRC5A is the first member of a new class of orphan receptors coupled to G proteins, which also includes GPRC5B, GPRC5C, and GPRC5D. Since its cloning and identification in the 1990s, substantial progress has been made in understanding the possible functions of this receptor. GPRC5A has been implicated in a variety of cellular events, such as cytoskeleton reorganization, cell proliferation, cell cycle regulation, migration, and survival. It appears to be a central player in different pathological processes, including tumorigenesis, inflammation, immune response, and tissue damage. The levels of GPRC5A expression differ depending on the type of cancer, with increased expression in colon, pancreas, and prostate cancers; decreased expression in lung cancer; and varied results in breast cancer. In this review, we discuss the early discovery of GPRC5A as a phorbol ester-induced gene and later as a retinoic acid-induced gene, its regulation, and its participation in important canonical pathways related to numerous types of tumors and inflammatory processes. GPRC5A represents a potential new target for cancer, inflammation, and immunity therapies.

Pathogenesis of Tobacco-Associated Lung Adenocarcinoma Is Closely Coupled with Changes in the Gut and Lung Microbiomes

Microbial dysbiosis has emerged as a modulator of oncogenesis and response to therapy, particularly in lung cancer. Here, we investigate the evolution of the gut and lung microbiomes following exposure to a tobacco carcinogen. We performed 16S rRNA-Seq of fecal and lung samples collected prior to and at several timepoints following (nicotine-specific nitrosamine ketone/NNK) exposure in Gprc5a-/- mice that were previously shown to exhibit accelerated lung adenocarcinoma (LUAD) development following NNK exposure. We found significant progressive changes in human-relevant gut and lung microbiome members (e.g., Odoribacter, Alistipes, Akkermansia, and Ruminococus) that are closely associated with the phenotypic development of LUAD and immunotherapeutic response in human lung cancer patients. These changes were associated with decreased short-chain fatty acids (propionic acid and butyric acid) following exposure to NNK. We next sought to study the impact of Lcn2 expression, a bacterial growth inhibitor, given our previous findings on its protective role in LUAD development. Indeed, we found that the loss of Lcn2 was associated with widespread gut and lung microbiome changes at all timepoints, distinct from those observed in our Gprc5a-/- mouse model, including a decrease in abundance and diversity. Our overall findings apprise novel cues implicating microbial phenotypes in the development of tobacco-associated LUAD.

GPRC5A: An emerging prognostic biomarker for predicting malignancy of Pancreatic Cancer based on bioinformatics analysis

Background: Pancreatic cancer (PaCa) is a highly lethal malignancy. The treatment options for PaCa lack efficacy. The study aimed to explore the molecular biomarkers for predicting survival of PaCa and identify the potential carcinogenic mechanisms of the selected gene. Methods: Based on public databases of PaCa, differentially expressed genes (DEGs) were identified using Networkanalyst. Survival analyses were exerted on GEPIA. Oncomine and The Human Protein Atlas were used for verifying the expression on mRNA and protein levels. Enrichment analyses were generated on Metascape and gene set enrichment analysis (GSEA). Univariate analyses were performed to determine the clinical factors associated with the expression of GPRC5A. Results: GPRC5A was identified as the most valuable gene in predicting survival of PaCa patients. Patients with high expression of GPRC5A showed larger tumor size, higher TNM stages, higher tumor grade, and more positive resection margin. In mutant KRAS, TP53, CDKN2A and SMAD4 group, the expression of GPRC5A was higher than non-mutant group. Mechanistically, GPRC5A may promote metastasis of PaCa mainly via regulating epithelial-mesenchymal transition (EMT) and neuroactive ligand-receptor interaction. Conclusion: GPRC5A may act as an oncogene in the progression of PaCa and could be a prognostic biomarker in predicting survival of PaCa.

Augmented Lipocalin-2 Is Associated with Chronic Obstructive Pulmonary Disease and Counteracts Lung Adenocarcinoma Development

Rationale: Early pathogenesis of lung adenocarcinoma (LUAD) remains largely unknown. We found that, relative to wild-type littermates, the innate immunomodulator Lcn2 (lipocalin-2) was increased in normal airways from mice with knockout of the airway lineage gene Gprc5a (Gprc5a^-/-) and that are prone to developing inflammation and LUAD. Yet, the role of LCN2 in lung inflammation and LUAD is poorly understood.Objectives: Delineate the role of Lcn2 induction in LUAD pathogenesis.Methods: Normal airway brushings, uninvolved lung tissues, and tumors from Gprc5a^-/- mice before and after tobacco carcinogen exposure were analyzed by RNA sequencing. LCN2 mRNA was analyzed in public and in-house data sets of LUAD, lung squamous cancer (LUSC), chronic obstructive pulmonary disease (COPD), and LUAD/LUSC with COPD. LCN2 protein was immunohistochemically analyzed in a tissue microarray of 510 tumors. Temporal lung tumor development, gene expression programs, and host immune responses were compared between Gprc5a^-/- and Gprc5a^-/-/Lcn2^-/- littermates.Measurements and Main Results: Lcn2 was progressively elevated during LUAD development and positively correlated with proinflammatory cytokines and inflammation gene sets. LCN2 was distinctively elevated in human LUADs, but not in LUSCs, relative to normal lungs and was associated with COPD among smokers and patients with LUAD. Relative to Gprc5a^-/- mice, Gprc5a^-/-/Lcn2^-/- littermates exhibited significantly increased lung tumor development concomitant with reduced T-cell abundance (CD4⁺) and richness, attenuated antitumor immune gene programs, and increased immune cell expression of protumor inflammatory cytokines.Conclusions: Augmented LCN2 expression is a molecular feature of COPD-associated LUAD and counteracts LUAD development in vivo by maintaining antitumor immunity.

Silencing lncRNA DUXAP8 inhibits lung adenocarcinoma progression by targeting miR-26b-5p

Lung adenocarcinoma (LUAD), a common type of lung cancer, has become a popularly aggressive cancer. Long noncoding RNAs (lncRNAs) play a critical role in the pathogenesis of human cancers, while the function of double homeobox A pseudogene 8 (DUXAP8) in LUAD remains to be fully inquired. Therefore, our study was conducted to elucidate the DUXAP8 expression in LUAD and its mechanism on the biological features of LUAD cells. Loss-of-function experiments were performed to assess the function of DUXAP8 proliferation and apoptosis of H1975 and A549 cells. Functionally, silencing DUXAP8 inhibited proliferation and induced apoptosis of LUAD cells. Mechanistically, further correlation assay indicated a negative association between miR-26b-5p and DUXAP8 expression. Subsequently, we testified that DUXAP8 exerted its role in the progression and development of LUAD through targeting miR-26b-5p. In summary, our results elucidated that that DUXAP8 promoted tumor progression in LUAD by targeting miR-26b-5p, which provide a novel therapeutic target for diagnosis and therapy of LUAD.

A Seven Immune-Related lncRNAs Model to Increase the Predicted Value of Lung Adenocarcinoma

Background

Recent research has shown that immune-related lncRNA plays a crucial part in the tumor immune microenvironment. This study tried to identify immune-related lncRNAs and construct a robust prediction model to increase the predicted value of lung adenocarcinoma (LUAD).

Methods

RNA expression data of LUAD were download from the Cancer Genome Atlas (TCGA) database. Immune genes were acquired from the Molecular Signatures Database (MSigDB). The immune gene related lncRNAs were acquired by the “limma R” package and Cytoscape3.7.1. Cox regression analysis was applied to construct this forecast model. The prognostic model was validated by the testing cohort which was acquired by the bootstrap method.

Results

A total of 551 lncRNA expression profiles including 497 LUAD tissues and 54 non-LUAD tissues were obtained. A total of 331 immune genes were acquired. The result of the Cox regression analysis showed that seven lncRNAs (AC022784-1, NKILA, AC026355-1, AC068338-3, LINC01843, SYNPR-AS1, and AC123595-1) can be performed to construct the prediction model to forecast the prognosis of LUAD. Kaplan–Meier curves indicated that our prediction model can distribute LUAD patients into two different risk groups (high and low) with significant statistical significance (P = 1.484e-07). Cox analysis and independent analysis illustrated that the seven-lncRNAs prediction model was an isolated factor by comparing it with other clinical variables. We validated the accuracy of our model in the testing dataset. Furthermore, the prognostic model also showed higher predictive efficiency than three other published prognostic models. The two different survival groups represented diverse immune features according to principal components analysis. GSEA analysis (gene set enrichment analysis) indicated that seven-lncRNAs signatures may be involved in the progression of tumorigenesis.

Conclusions

We have established a seven immune-related lncRNAs prediction model. This prognostic model had significant clinical significance that increased the predicted value and guided the personalized treatment for LUAD patients.

Crystalline silica particles cause rapid NLRP3-dependent mitochondrial depolarization and DNA damage in airway epithelial cells

BACKGROUND

Respirable crystalline silica causes lung carcinomas and many thousand future cancer cases are expected in e.g. Europe. Critical questions are how silica causes genotoxicity in the respiratory epithelium and if new cases can be avoided by lowered permissible exposure levels. In this study we investigate early DNA damaging effects of low doses of silica particles in respiratory epithelial cells in vitro and in vivo in an effort to understand low-dose carcinogenic effects of silica particles.

RESULTS

We find DNA damage accumulation already after 5-10 min exposure to low doses (5 μg/cm²) of silica particles (Min-U-Sil 5) in vitro. DNA damage was documented as increased levels of γH2AX, pCHK2, by Comet assay, AIM2 induction, and by increased DNA repair (non-homologous end joining) signaling. The DNA damage response (DDR) was not related to increased ROS levels, but to a NLRP3-dependent mitochondrial depolarization. Particles in contact with the plasma membrane elicited a Ser198 phosphorylation of NLRP3, co-localization of NLRP3 to mitochondria and depolarization. FCCP, a mitochondrial uncoupler, as well as overexpressed NLRP3 mimicked the silica-induced depolarization and the DNA damage response. A single inhalation of 25 μg silica particles gave a similar rapid DDR in mouse lung. Biomarkers (CC10 and GPRC5A) indicated an involvement of respiratory epithelial cells.

CONCLUSIONS

Our findings demonstrate a novel mode of action (MOA) for silica-induced DNA damage and mutagenic double strand breaks in airway epithelial cells. This MOA seems independent of particle uptake and of an involvement of macrophages. Our study might help defining models for estimating exposure levels without DNA damaging effects.

microRNA-367-3p regulation of GPRC5A is suppressed in ischemic stroke

Ischemic stroke is a major cause of mortality and long-term disability with limited treatment options, and a greater understanding of the gene regulatory mechanisms underlying ischemic stroke-associated neuroinflammation is required for new therapies. To study ischemic stroke in vivo, mice were subjected to sustained ischemia by intraluminal filament-induced middle cerebral artery occlusion (MCAo) for 24 h without reperfusion or transient ischemia for 30 min followed by 23.5 h reperfusion, and brain miRNA and mRNA expression changes were quantified by TaqMan OpenArrays and gene (mRNA) expression arrays, respectively. Sustained ischemia resulted in 18 significantly altered miRNAs and 392 altered mRNAs in mouse brains compared to Sham controls; however, the transient ischemic condition was found to impact only 6 miRNAs and 126 mRNAs. miR-367-3p was found to be significantly decreased in brain homogenates with sustained ischemia. G protein-coupled receptor, family C, group 5, member A (Gprc5a), a miR-367-3p target gene, was found to be significantly increased with sustained ischemia. In primary neurons, inhibition of endogenous miR-367-3p resulted in a significant increase in Gprc5a expression. Moreover, miR-367-3p was found to be co-expressed with GPRC5A in human neurons. Results suggest that loss of miR-367-3p suppression of GPRC5A may contribute to neuroinflammation associated with ischemic stroke.

Circulating markers of cellular immune activation in prediagnostic blood sample and lung cancer risk in the Lung Cancer Cohort Consortium (LC3)

Cell-mediated immune suppression may play an important role in lung carcinogenesis. We investigated the associations for circulating levels of tryptophan, kynurenine, kynurenine:tryptophan ratio (KTR), quinolinic acid (QA) and neopterin as markers of immune regulation and inflammation with lung cancer risk in 5,364 smoking-matched case-control pairs from 20 prospective cohorts included in the international Lung Cancer Cohort Consortium. All biomarkers were quantified by mass spectrometry-based methods in serum/plasma samples collected on average 6 years before lung cancer diagnosis. Odds ratios (ORs) and 95% confidence intervals (CIs) for lung cancer associated with individual biomarkers were calculated using conditional logistic regression with adjustment for circulating cotinine. Compared to the lowest quintile, the highest quintiles of kynurenine, KTR, QA and neopterin were associated with a 20-30% higher risk, and tryptophan with a 15% lower risk of lung cancer (all ptrend < 0.05). The strongest associations were seen for current smokers, where the adjusted ORs (95% CIs) of lung cancer for the highest quintile of KTR, QA and neopterin were 1.42 (1.15-1.75), 1.42 (1.14-1.76) and 1.45 (1.13-1.86), respectively. A stronger association was also seen for KTR and QA with risk of lung squamous cell carcinoma followed by adenocarcinoma, and for lung cancer diagnosed within the first 2 years after blood draw. This study demonstrated that components of the tryptophan-kynurenine pathway with immunomodulatory effects are associated with risk of lung cancer overall, especially for current smokers. Further research is needed to evaluate the role of these biomarkers in lung carcinogenesis and progression.

Development and validation of a survival model for lung adenocarcinoma based on autophagy-associated genes

BACKGROUND

Given that abnormal autophagy is involved in the pathogenesis of cancers, we sought to explore the potential value of autophagy-associated genes in lung adenocarcinoma (LUAD).

METHODS

RNA sequencing and clinical data on tumour and normal samples were acquired from The Cancer Genome Atlas (TCGA) database and randomly assigned to training and testing groups. Differentially expressed autophagy-associated genes (AAGs) were screened. Within the training group, Cox regression and Lasso regression analyses were conducted to screen five prognostic AAGs, which were used to develop a model. Kaplan-Meier (KM) and receiver operating characteristic (ROC) curves were plotted to determine the performance of the model in both groups. Immunohistochemistry was used to demonstrate the differential expression of AAGs in tumour and normal tissues at the protein level. Gene Ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were utilized to further elucidate the roles of AAGs in LUAD.

RESULTS

The data from the TCGA database included 497 tumour and 54 normal samples, within which 30 differentially expressed AAGs were screened. Using Cox regression and Lasso regression analyses for the training group, 5 prognostic AAGs were identified and the prognostic model was constructed. Patients with low risk had better overall survival (OS) in the training group (3-year OS, 73.0% vs 48.0%; 5-year OS, 45.0% vs 33.8%; P = 1.305E-04) and in the testing group (3-year OS, 66.8% vs 41.2%; 5-year OS, 31.7% vs 25.8%; P = 1.027E-03). The areas under the ROC curves (AUC) were significant for both the training and testing groups (3-year AUC, 0.810 vs 0.894; 5-year AUC, 0.792 vs 0.749).

CONCLUSIONS

We developed a survival model for LUAD and validated the performance of the model, which may provide superior outcomes for the patients.

Genome-Wide and Phenotypic Evaluation of Stem Cell Progenitors Derived From Gprc5a-Deficient Murine Lung Adenocarcinoma With Somatic Kras Mutations

Lung adenocarcinomas (LUADs) with somatic mutations in the KRAS oncogene comprise the most common molecular subtype of lung cancer in smokers and present with overall dismal prognosis and resistance to most therapies. Our group recently demonstrated that tobacco carcinogen-exposed mice with knockout of the airway lineage G-protein coupled receptor, Gprc5a, develop LUADs with somatic mutations in Kras. Earlier work has suggested that cancer stem cells (CSCs) play crucial roles in clonal evolution of tumors and in therapy resistance. To date, our understanding of CSCs in LUADs with somatic Kras mutations remains lagging. Here we derived CSCs (as spheres in 3D cultures) with self-renewal properties from a murine Kras-mutant LUAD cell line we previously established from a tobacco carcinogen-exposed Gprc5a -/- mouse. Using syngeneic Gprc5a -/- models, we found that these CSCs, compared to their parental isoforms, exhibited increased tumorigenic potential in vivo, particularly in female animals. Using whole-transcriptome sequencing coupled with pathways analysis and confirmatory PCR, we identified gene features (n = 2,600) differentially expressed in the CSCs compared to parental cells and that were enriched with functional modules associated with an augmented malignant phenotype including stemness, tumor-promoting inflammation and anti-oxidant responses. Further, based on in silico predicted activation of GSK3β in CSCs, we found that tideglusib, an irreversible inhibitor of the kinase, exhibited marked anti-growth effects in the cultured CSCs. Our study underscores molecular cues in the pathogenesis of Kras-mutant LUAD and presents new models to study the evolution, and thus high-potential targets, of this aggressive malignancy.

Transcriptomic Alterations in Lung Adenocarcinoma Unveil New Mechanisms Targeted by the TBX2 Subfamily of Tumor Suppressor Genes

T-box (TBX) transcription factors are evolutionary conserved genes and master transcriptional regulators. In mammals, TBX2 subfamily (TBX2, TBX3, TBX4, and TBX5) genes are expressed in the developing lung bud and tracheae. Our group previously showed that the expression of TBX2 subfamily was significantly high in human normal lungs, but markedly suppressed in lung adenocarcinoma (LUAD). To further elucidate their role in LUAD pathogenesis, we first confirmed abundant expression of protein products of the four members by immunostaining in adult human normal lung tissues. We also found overall suppressed expression of these genes and their corresponding proteins in a panel of human LUAD cell lines. Transient over-expression of each of the genes in human (NCI-H1299), and mouse (MDA-F471) derived lung cancer cells was found to significantly inhibit growth and proliferation as well as induce apoptosis. Genome-wide transcriptomic analyses on NCI-H1299 cells, overexpressing TBX2 gene subfamily, unraveled novel regulatory pathways. These included, among others, inhibition of cell cycle progression but more importantly activation of the histone demethylase pathway. When using a pattern-matching algorithm, we showed that TBX's overexpression mimic molecular signatures from azacitidine treated NCI-H1299 cells which in turn are inversely correlated to expression profiles of both human and murine lung tumors relative to matched normal lung. In conclusion, we showed that the TBX2 subfamily genes play a critical tumor suppressor role in lung cancer pathogenesis through regulating its methylating pattern, making them putative candidates for epigenetic therapy in LUAD.

GPRC5A: An Emerging Biomarker in Human Cancer

Aberrant expression of G protein-coupled receptors (GPCRs) is frequently associated with tumorigenesis. G Protein-coupled receptor class C group 5 member A (GPRC5A) is a member of the GPCR superfamily, is expressed preferentially in lung tissues, and is regulated by various entities at multiple levels. GPRC5A exerts a tumor suppressive role in lung cancer and GPRC5A deletion promotes lung tumor initiation and progression. Recent advances have highlighted that GPRC5A dysregulation is found in various human cancers and is related to many tumor-associated signaling pathways, including the cyclic adenosine monophosphate (cAMP), nuclear factor (NF)-κB, signal transducer and activator of transcription (STAT) 3, and focal adhesion kinase (FAK)/Src signaling. This review aimed to summarize our updated view on the biology and regulation of GPRC5A, its expression in human cancers, and the linked signaling pathways. A better comprehension of the underlying cellular and molecular mechanisms of GPRC5A will provide novel insights into its potential diagnostic and therapeutic value.

Genome-Wide Gene Expression Changes in the Normal-Appearing Airway during the Evolution of Smoking-Associated Lung Adenocarcinoma

Smoking perpetuates in cytologically normal airways a molecular "field of injury" that is pertinent to lung cancer and early detection. The evolution of airway field changes prior to lung oncogenesis is poorly understood largely due to the long latency of lung cancer in smokers. Here, we studied airway expression changes prior to lung cancer onset in mice with knockout of the Gprc5a gene (Gprc5a^-/-) and tobacco carcinogen (NNK) exposure and that develop the most common type of lung cancer, lung adenocarcinoma, within 6 months following exposure. Airway epithelial brushings were collected from Gprc5a^-/- mice before exposure and at multiple times post-NNK until time of lung adenocarcinoma development and then analyzed by RNA sequencing. Temporal airway profiles were identified by linear models and analyzed by comparative genomics in normal airways of human smokers with and without lung cancer. We identified significantly altered profiles (n = 926) in the NNK-exposed mouse normal airways relative to baseline epithelia, a subset of which were concordantly modulated with smoking status in the human airway. Among airway profiles that were significantly modulated following NNK, we found that expression changes (n = 22) occurring as early as 2 months following exposure were significantly associated with lung cancer status when examined in airways of human smokers. Furthermore, a subset of a recently reported human bronchial gene classifier (Percepta; n = 56) was enriched in the temporal mouse airway profiles. We underscore evolutionarily conserved profiles in the normal-appearing airway that develop prior to lung oncogenesis and that comprise viable markers for early lung cancer detection in suspect smokers. Cancer Prev Res; 11(4); 237-48. ©2018 AACR.