Identification of differentially expressed genes in immortalized human bronchial epithelial cell line as a model for in vitro study of lung carcinogenesis

TBL1X: At the crossroads of transcriptional and posttranscriptional regulation

Over the past 2 decades, the adaptor protein transducin β-like 1 (TBL1X) and its homolog TBL1XR1 have been shown to be upregulated in solid tumors and hematologic malignancies, and their overexpression is associated with poor clinical outcomes. Moreover, dysregulation of the TBL1 family of proteins has been implicated as a key component of oncogenic prosurvival signaling, cancer progression, and metastasis. Herein, we discuss how TBL1X and TBL1XR1 are required for the regulation of major transcriptional programs through the silencing mediator for tetanoid and thyroid hormone receptor (SMRT)/nuclear receptor corepressor (NCOR)/ B cell lymphoma 6 (BCL6) complex, Wnt/β catenin, and NF-κB signaling. We outline the utilization of tegavivint (Iterion Therapeutics), a first-in-class small molecule targeting the N-terminus domain of TBL1, as a novel therapeutic strategy in preclinical models of cancer and clinically. Although most published work has focused on the transcriptional role of TBL1X, we recently showed that in diffuse large B-cell lymphoma (DLBCL), the most common lymphoma subtype, genetic knockdown of TBL1X and treatment with tegavivint resulted in decreased expression of critical (onco)-proteins in a posttranscriptional/β-catenin-independent manner by promoting their proteasomal degradation through a Skp1/Cul1/F-box (SCF)/TBL1X supercomplex and potentially through the regulation of protein synthesis. However, given that TBL1X controls multiple oncogenic signaling pathways in cancer, treatment with tegavivint may ultimately result in drug resistance, providing the rationale for combination strategies. Although many questions related to TBL1X function remain to be answered in lymphoma and other diseases, these data provide a growing body of evidence that TBL1X is a promising therapeutic target in oncology.

TBL1XR1 as a potential therapeutic target that promotes epithelial-mesenchymal transition in lung squamous cell carcinoma

Transducin (β)-like 1 X-linked receptor 1 (TBL1XR1) has been demonstrated to serve a vital role in tumor progression. However, the biological role and molecular mechanisms of TBL1XR1 in lung squamous cell carcinoma (SCC) remain largely unknown. The purpose of the present study was to investigate the biological role of TBL1XR1 and its mechanism in lung SCC. TBL1XR1 was expressed in a human bronchial epithelial cell line and in lung SCC cell lines. The present study analyzed TBL1XR1-induced proliferation, invasion and migration abilities in vitro using the cell counting kit-8 assay, cell invasion assay and wound healing assay, respectively. This study examined the effects of TBL1XR1 on epithelial-mesenchymal transition (EMT) in lung SCC cells and activation of the transforming growth factor (TGF)-β/mothers against decapentaplegic homolog (Smad) signaling pathway by western blotting. The results indicated that TBL1XR1 was upregulated in lung SCC cells. Overexpression of TBL1XR1 increased the rate of cell proliferation compared with the control group. In vitro, overexpression of TBL1XR1 promoted cell invasion and migration ability compared with the control group. In addition, overexpression of TBL1XR1 produced a mesenchymal phenotype, while cells with downregulated TBL1XR1 produced an epithelial phenotype. Overexpression of TBL1XR1 significantly increased E-cadherin protein expression whilst snail family transcriptional repressor 1 (SNAI1), zinc finger E-box binding homebox 1 (ZEB1), p-Smad2/3, Smad2 and Smad3 protein expression was significantly reduced, compared with the control group. Downregulation of TBL1XR1 produced the opposite results. The present study indicated that TBL1XR1 contributed to lung SCC development and progression, and therefore TBL1XR1 may be a potential therapeutic target. TBL1XR1 may induce EMT of lung SCC cells through activation of the TGF-β/Smad signaling pathway.

Rap2B promotes angiogenesis via PI3K/AKT/VEGF signaling pathway in human renal cell carcinoma

Human renal cell carcinoma which is a highly vascular tumor is the leading cause of death from urologic cancers. Angiogenesis has a pivotal role in oncogenesis and in the viability and expansion of renal cell carcinoma. Rap2B, as a small guanosine triphosphate–binding protein of the Ras family, was first discovered in the early 1990s during the screening of a platelet complementary DNA library. Previous studies have shown that Rap2B aberrantly expressed in human carcinogenesis and promoted the development of tumors via multiple signaling pathways. However, the function of Rap2B in tumor angiogenesis that is necessary for tumor growth and metastasis remains unknown. In this study, we examined the role of Rap2B in angiogenesis in renal cell carcinoma by Western blot, quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, human umbilical vascular endothelial cells growth assay, and endothelial cell tube formation assay. We found that Rap2B promoted angiogenesis in vitro and in vivo. Moreover, our data illustrated that phosphoinositide 3-kinase/AKT signaling pathway is involved in Rap2B-mediated upregulation of vascular endothelial growth factor and renal cell carcinoma angiogenesis. Taken together, these results revealed that Rap2B promotes renal cell carcinoma angiogenesis via phosphoinositide 3-kinase/AKT/vascular endothelial growth factor signaling pathway, which suggests that Rap2B is a novel therapeutic target for renal cell carcinoma anti-angiogenesis therapy.

Knockdown of Rap2B, a Ras Superfamily Protein, Inhibits Proliferation, Migration, and Invasion in Cervical Cancer Cells via Regulating the ERK1/2 Signaling Pathway

Rap2B, belonging to the Ras superfamily, has been implicated in cancer development and functions as a tumor promoter. However, the role of Rap2B in cervical cancer is unknown. In this study, we investigated the expression pattern and biological functions of Rap2B in cervical cancer. The results showed that Rap2B was overexpressed in cervical cancer tissues and cell lines. Knockdown of Rap2B inhibited the proliferation, migration, and invasion of cervical cancer cells. In addition, our tumorigenesis assay showed that Rap2B knockdown suppressed cervical cancer cell growth and metastasis in vivo. We also found that the ERK1/2 signaling pathway is involved in the inhibitory effect of Rap2B knockdown on cervical cancer development. In conclusion, we suggest that Rap2B is an oncogene and may be a promising therapeutic target for cervical cancer.

TBL1XR1 Is Highly Expressed in Gastric Cancer and Predicts Poor Prognosis

Objective. To investigate the expression of transducin- (β-) like 1 X-linked receptor 1 (TBL1XR1) in human gastric cancer (GC) and its correlation with prognostic and biologic significance. Methods. TBL1XR1 mRNA expression was analyzed in gastric cancer using a microarray dataset (GSE2701) from the Gene Expression Omnibus (GEO). Immunohistochemistry (IHC) analysis of TBL1XR1 was performed on GC tissue microarray (TMA) to assess its prognostic and biological significance in 334 patients of GC. Results. Analysis of GSE2701 showed that the mRNA levels of TBL1XR1 were significantly elevated in primary gastric tumor and lymph node tissues than normal gastric tissues (P < 0.05). The same results of TBL1XR1 protein level were observed by IHC staining in 334 GC tissues. 204 of 334 (60.1%) primary gastric cancer tissues showed high expression of TBL1XR1 protein. TBL1XR1 overexpression was significantly correlated with lymph node metastasis (P = 0.000) and advanced TNM stage (P = 0.001). Moreover, high levels of TBL1XR1 predicted worse overall survival (P = 0.015). Multivariate Cox regression analysis indicated that high expression of TBL1XR1 was an independent prognostic factor for poor overall survival (HR, 0.525; 95% confidence interval, 0.367–0.752; P = 0.005). Conclusion. This present study demonstrates that TBL1XR1 is overexpressed in gastric cancer and may be a potential predictor and therapeutic target for GC patients.

Rap2B promotes cell proliferation, migration and invasion in prostate cancer

Rap2B, a member of the Ras family of small GTP-binding proteins, reportedly presents a high level of expression in various human tumors and plays a significant role in the development of tumor. However, the function of Rap2B in prostate cancer (PCa) remains unclear. We elucidated the stimulative role of Rap2B in PCa cell proliferation, migration and invasion by means of the CCK-8 cell proliferation assay, cell cycle analysis and transwell migration assay. Western blot analysis uncovered that elevated Rap2B leads to increased phosphorylation levels of FAK, suggesting that FAK-dependent pathway might be responsible for the effect of Rap2B on PCa cells migration and invasion. Inversely, FAK-specific inhibitor (PF-573228) can abort Rap2B-induced FAK phosphorylation. In vivo experiment confirmed that Rap2B positively regulated PCa growth and metastasis, as well as the expression of phosphorylated FAK. Collectively, these findings shed light on Rap2B as a potential therapeutic target for PCa.

Structure, functional regulation and signaling properties of Rap2B

The Ras family small guanosine 5'-triphosphate (GTP)-binding protein Rap2B is is a member of the Ras oncogene family and a novel target of p53 that regulates the p53-mediated pro-survival function of cells. The Rap2B protein shares ~90% homology with Rap2A, and its sequence is 70% identical to other members of the Rap family such as RaplA and RaplB. As a result, Rap2B has been theorized to have similar signaling effectors to the GTPase-binding protein Rap, which mediates various biological functions, including the regulation of sterile 20/mitogen-activated proteins. Since its identification in the early 1990s, Rap2B has elicited a considerable interest. Numerous studies indicate that Rap2B exerts specific biological functions, including binding and stimulating phospholipase C-ε and interferon-γ. In addition, downregulation of Rap2B affects the growth of melanoma cells. The present review summarizes the possible effectors and biological functions of Rap2B. Increasing evidence clearly supports the association between Rap2B function and tumor development. Therefore, it is conceivable that anticancer drugs targeting Rap2B may be generated as novel therapies against cancer.

Decreased Interferon Alpha/Beta Signature Associated with Human Lung Tumorigenesis

Accumulating evidence suggests that interferon (IFN) alpha/beta are involved in antitumor immunity and cancer immunoediting, but information on the antitumor effects of IFN alpha/beta in lung cancer is limited. In our study, we elucidated the IFN alpha/beta signature during both human fetal lung development and lung tumorigenesis. Our findings indicated gradual upregulation in the IFN alpha/beta signature during human fetal lung development. In addition, this signature was progressively downregulated in normal human airway epithelial cells from lung cancer patients, in immortalized human bronchial epithelial cell lines from later passages, in late-stage lung squamous cell carcinoma (LSCC) tissues, and in LSCC tissues exhibiting lymph node metastasis. Therefore, from its earliest stages, lung tumorigenesis may be associated with a decreased IFN alpha/beta signature. This association may provide insight to guide the detection of high-risk lung cancer patients.

Rap2B promotes proliferation, migration, and invasion of human breast cancer through calcium-related ERK1/2 signaling pathway

Rap2B, a member of GTP-binding proteins, is widely upregulated in many types of tumors and promotes migration and invasion of human suprarenal epithelioma. However, the function of Rap2B in breast cancer is unknown. Expression of Rap2B was examined in breast cancer cell lines and human normal breast cell line using Western blot analysis. Using the CCK-8 cell proliferation assay, cell cycle analysis, and transwell migration assay, we also elucidated the role of Rap2B in breast cancer cell proliferation, migration, and invasion. Results showed that the expression of Rap2B is higher in tumor cells than in normal cells. Flow cytometry and Western blot analysis revealed that Rap2B elevates the intracellular calcium level and further promotes extracellular signal-related kinase (ERK) 1/2 phosphorylation. By contrast, calcium chelator BAPTM/AM and MEK inhibitor (U0126) can reverse Rap2B-induced ERK1/2 phosphorylation. Furthermore, Rap2B knockdown inhibits cell proliferation, migration, and invasion abilities via calcium related-ERK1/2 signaling. In addition, overexpression of Rap2B promotes cell proliferation, migration and invasion abilities, which could be neutralized by BAPTM/AM and U0126. Taken together, these findings shed light on Rap2B as a therapeutic target for breast cancer.

TBLR1 is a novel prognostic marker and promotes epithelial-mesenchymal transition in cervical cancer

BACKGROUND

Invasion and metastasis remain a critical issue in cervical cancer. However, the underlying mechanism of it in cervical cancer remains unclear. The newly discovered protein, TBLR1, plays a crucial role in regulating various key cellular functions.

METHODS

In this study, western blot, real-time RT-PCR, immunohistochemical staining, 3D morphogenesis Matrigel culture, wound healing and Boyden chamber invasion assays, xenografted tumour model, luciferase assays, and chromatin immunoprecipitation assays were used.

RESULTS

The expression of TBLR1 in cervical cancer cell lines and tissues was significantly upregulated at both the RNA and protein levels compared with that in normal cervical cells. Statistical analysis suggested that TBLR1 as an independent prognostic factor was significantly correlated with the clinical stage, survival time and recurrence. Moreover, overexpression of TBLR1 in Hela and Siha cell lines promoted invasion in vitro and in vivo with the increases of the mesenchymal factors vimentin and fibronectin and decreases of the epithelial marker α-catenin. In contrast, RNAi-mediated knockdown of TBLR1 inhibited epithelial-mesenchymal transition in vitro and in vivo. Further study indicated that this might be mediated via the NF-κB and Wnt/β-Catenin signalling pathway, and involve regulation of Snail and Twist.

CONCLUSIONS

The TBLR1 protein may be a prognostic marker in cervical cancer and play an important role in the invasion and metastasis of human cervical cancer.

Suppression of non-small cell lung cancer proliferation and tumorigenicity by DENND2D

DENND2D was identified as being down-regulated in lung cancer using a lung cancer low-expression suppression subtractive hybridization (SSH) library. In this study, DENND2D down-regulation has been observed not only in non-small cell lung cancer (NSCLC) cell lines and lung squamous cell carcinoma (SCC) tissues, but also in immortalized human bronchial epithelial (IHBE) cell lines and precancerous lesions, indicating that the down-regulation of DENND2D may be an early event in lung cancer. The relative DNA copy number and mRNA and protein expression levels of DENND2D were determined in vitro, and they revealed a complicated regulatory network at the genomic, transcriptional and translational levels. Over-expression of DENND2D significantly suppressed the proliferation of NSCLC cells in vitro and in vivo by inducing apoptosis. These results indicate that DENND2D might function as a tumor suppressor-like gene to prevent the survival and expansion of cells with genetic damage through apoptosis mechanism, and absence of DENND2D might play a permissive role, as an early event, in tumorigenesis.

Overexpression of OLC1, cigarette smoke, and human lung tumorigenesis

BACKGROUND

Exposure to cigarette smoke is a major risk factor for lung cancer, but how it induces cancer is unclear. The overexpressed in lung cancer 1 (OLC1) gene is one of 50 candidate lung cancer genes identified by suppression subtractive hybridization as having higher expression in squamous cell carcinoma (SCC) than normal lung epithelia.

METHODS

We used immunohistochemistry (IHC) to measure OLC1 protein levels in primary lung cancer samples from 559 patients and used fluorescence in situ hybridization to measure OLC1 copy number in primary SCC samples from 23 patients. We compared OLC1 protein expression in SCC samples of 371 patients with and without a smoking history using the Pearson chi(2) test. We assayed OLC1 protein levels by immunoblotting in H1299 human lung cancer cells, immortalized human bronchial epithelial cells, and primary cultured normal human bronchial epithelial cells that were treated with cigarette smoke condensate. We assayed tumor formation in athymic mice using NIH3T3 mouse fibroblast cells transfected with OLC1 (eight mice) and analyzed apoptosis and colony formation of H1299 and H520 lung cancer cells transfected with scrambled (negative) or OLC1 small interfering RNAs (siRNAs) (s1).

RESULTS

OLC1 protein was overexpressed in 387 of 464 (83.4%) of primary lung cancers, as detected by IHC, and OLC1 was amplified in 14 of 23 (60%) of SCC samples. OLC1 protein overexpression was more common in SCC patients with a smoking history than those without (77.1% vs 45.8%, P < .001). In addition, cigarette smoke condensate increased OLC1 protein levels in H1299 cells, immortalized human bronchial epithelial cells, and primary cultured normal human bronchial epithelial cells. Overexpression of OLC1 induced tumor formation in athymic mice (control vs OLC1, 0% vs 100%). Knockdown of OLC1 increased apoptosis (mean percentage of apoptotic H1299 cells, s1 vs negative: 30.3% vs 6.4%, difference = 23.9%, 95% confidence interval [CI] = 19.1% to 28.5%, P = .002; mean percentage of apoptotic H520 cells, s1 vs negative: 21.6% vs 4.9%, difference = 16.7%, 95% CI = 10.6% to 22.8%, P = .007) and decreased colony formation (mean no. of colonies of H1299 cells transfected with siRNAs, negative vs s1: 84 vs 4, difference = 80, 95% CI = 71 to 88, P < .001; mean no. of colonies of H520 cells transfected with siRNAs, negative vs s1: 103 vs 24, difference = 79, 95% CI = 40 to 116, P = .005).

CONCLUSIONS

OLC1 is a candidate oncogene in lung cancer whose expression may be regulated by exposure to cigarette smoke.

Identification of genes differentially expressed in human primary lung squamous cell carcinoma

To identify differentially expressed genes in lung squamous cell carcinomas (SCCs), the suppression subtractive hybridization method (SSH) was performed comparing six lung tumour tissues and 10 morphologically normal bronchial epithelial tissues. A cDNA library consisting of 220 upregulated genes in tumour tissue was established and named as LSCC (lung squamous cell carcinoma). Of them, six were tested using semi-quantitative reverse transcription-PCR on 27 pairs of tumour tissue and normal lung tissue. Differential expression was confirmed in five of these six genes, including IGFBP5, SQLE, RAP2B, CLDN1, and TBL1XR1. The elevated mRNA expression of RAP2B, CLDN1 and TBL1XR1, three genes located on chromosome 3q, were further validated in 64.3% (18/28), 82.1% (23/28), and 75.0% (21/28) of lung SCC tumour tissues, respectively, by quantitative real-time reverse transcription-PCR analysis. Moreover, western blot analysis showed that the protein expression of TBL1XR1 was also upregulated in 53.3% (8/15) of lung SCC tumour samples, as well as in five lung cancer cell lines and in one human immortalized bronchial epithelial cell line. All the initial characteristics of these genes were first reported in the lung SCCs. The differentially expressed genes reported in this study will provide a valuable resource for understanding the pathogenesis of lung SCCs and for discovery of novel diagnostic or therapeutic targets.

Comparative genomic hybridization array analysis and real time PCR reveals genomic alterations in squamous cell carcinomas of the lung

Genomic alterations have been identified in lung cancer tissues and reported in numerous studies. To analyze genomic aberrations in lung cancer patients, we used array comparative genomic hybridization (array CGH) in 14 squamous cell lung carcinoma (SqC) tissues. Copy number gain and loss in chromosomal regions were detected, and the corresponding genes were confirmed by real time PCR. Several frequently altered loci, including gain of 3q (36% of samples), were found. The most frequently identified losses were found at 14q32.33 (21% of samples). The relative degree of chromosomal change was analyzed using log2 ratios. High-level DNA amplifications (>0.8 log2 ratio) were detected at 20 regions in 1p, 2q, 3q, 4q, 6q, 7p, 8q, 9p, 10q, 12q, 14q and 19p. We found that the fold change levels were highest at EVI1 (3q26.2), LPP (3q27-28) and FHF-1 (3q28) gene loci. Our results show that array CGH is a useful tool for identification of gene alteration in lung cancer, and that the above-mentioned genes might represent potential candidate genes for pathogenesis and diagnosis of lung cancer.

Identification of differently expressed genes in human colorectal adenocarcinoma

AIM: To investigate the differently expressed genes in human colorectal adenocarcinoma.

METHODS: The integrated approach for gene expression profiling that couples suppression subtractive hybridization, high-throughput cDNA array, sequencing, bioinformatics analysis, and reverse transcriptase real-time quantitative polymerase chain reaction (PCR) was carried out. A set of cDNA clones including 1260 SSH inserts amplified by PCR was arrayed using robotic printing. The cDNA arrays were hybridized with florescent-labeled probes prepared from RNA of human colorectal adenocarcinoma (HCRAC) and normal colorectal tissues.

RESULTS: A total of 86 genes were identified, 16 unknown genes and 70 known genes. The transcription factor Sox9 influencing cell differentiation was downregulated. At the same time, Heat shock protein 10 KDis downregulated and Calmoulin is up-regulated.

CONCLUSION: Downregulation of heat shock protein 10 KD lost its inhibition of Ras, and then attenuated the Ras GTPase signaling pathway, increased cell proliferation and inhibited cell apoptosis. Down-regulated transcription factor So x 9 influences cell differentiation and cell-specific gene expression. Down-regulated So x 9 also decreases its binding to calmodulin, accumulates calmodulin as receptor-activated kinase and phosphorylase kinase due to the activation of PhK.

Profile of differentially expressed genes after transfer of chromosome 17 into the breast cancer cell line CAl51

Previous studies have shown that transfer of chromosome 17 suppresses the tumorigenic phenotype of the breast cancer cell line CAL51, suggesting the presence of putative tumor suppressor genes on this chromosome. Suppression subtractive hybridization and oligonucleotide microarray analyses were performed to identify differentially expressed genes in nontumorigenic microcell hybrids, CAL/17-1 and CAL/17-3, when compared with CAL51 cells. In total, 263 differentially expressed transcripts were associated with these phenotypes. Of these, a high percentage is involved in various biological processes associated with tumorigenesis, including DNA-dependent regulation of transcription, regulation of cell cycle, signal transduction, and cell proliferation. Microarray analysis of selected chromosome 17 genes in a series of 25 human primary breast tumors showed associations with clinicopathologic parameters of the tumors. Of these genes, TOB1 (transducer of ERBB2) was selected for further expression analysis. Using RT-PCR and immunohistochemical staining of tissue microarrays, we could reveal a differential mRNA and protein expression of TOB1 in the majority of breast tumors and lymph node metastases compared with normal breast tissues, indicating a potential role of this protein in breast tumorigenesis.

Identification of differentially expressed genes in human lung squamous cell carcinoma using suppression subtractive hybridization

Lung cancer is one of the major causes of cancer-related deaths. Over the past decade, much has been known about the molecular changes associated with lung carcinogenesis; however, our understanding to lung tumorigenesis is still incomplete. To identify genes that are differentially expressed in squamous cell carcinoma (SCC) of the lung, we compared the expression profiles between primarily cultured SCC tumor cells and bronchial epithelial cells derived from morphologically normal bronchial epithelium of the same patient. Using suppression subtractive hybridization (SSH), two cDNA libraries containing up- and down-regulated genes in the tumor cells were constructed, named as LCTP and LCBP. The two libraries comprise 258 known genes and 133 unknown genes in total. The known up-regulated genes in the library LCTP represented a variety of functional groups; including metabolism-, cell adhesion and migration-, signal transduction-, and anti-apoptosis-related genes. Using semi-quantitative reverse transcription-polymerase chain reaction, seven genes chosen randomly from the LCTP were analyzed in the tumor tissue paired with its corresponding adjacent normal lung tissue derived from 16 cases of the SCC. Among them, the IQGAP1, RAP1GDS1, PAICS, MLF1, and MARK1 genes showed a consistent expression pattern with that of the SSH analysis. Identification and further characterization of these genes may allow a better understanding of lung carcinogenesis.