Heterogeneities in the biological and biochemical functions of Smad2 and Smad4 mutants naturally occurring in human lung cancers

Long Non-Coding RNA TRG-AS1 Promoted Proliferation and Invasion of Lung Cancer Cells Through the miR-224-5p/SMAD4 Axis

INTRODUCTION

The aim of this study was to investigate the role and mechanism of long non-coding RNA (lncRNA) TRG-AS1 in mediating the proliferation, invasion and migration of lung cancer cells as well lung tumor growth.

METHODS

Firstly, the expression levels of TRG-AS1, miR-224-5p in lung cancer tissues or cells were quantified by quantitative real-time PCR. Western blot analysis was conducted to measure the expression levels of protein SMAD4. CCK-8 assay, wound healing assay and transwell assay were conducted to evaluate cell proliferation, migration and invasion, respectively. The interaction between TRG-AS1 and miR-224-5p was predicted by bioinformatics analysis. Dual-luciferase assay and RNA pull-down assay were performed to further confirm their interaction. In addition, the interaction between miR-224-5p and SMAD4 was detected by RIP assay.

RESULTS

The results showed that TRG-AS1 was highly upregulated and miR-224-5p was downregulated in lung cancer. A negative correlation was found between TRG-AS1 and miR-224-5p. Furthermore, upregulation of TRG-AS1 promoted cell proliferation and invasion, while overexpression of miR-224-5p attenuated the effects of TRG-AS1. The downstream protein SMAD4 played an important role. In vivo study showed that knockdown of TRG-AS1 effectively retarded tumor growth.

DISCUSSION

Our data suggested that the TRG-AS1/miR-224-5p/SMAD4 axis may be a potential therapeutic target in lung cancer.

SMAD4 mutation correlates with poor prognosis in non-small cell lung cancer

SMAD4 is an intracellular signaling mediator of the TGF-β pathway. Its mutation was commonly observed in gastrointestinal cancers, such as pancreatic cancer. The loss of SMAD4 on immunohistochemical staining is often used to suggest a pancreaticobiliary differentiation in evaluating a metastatic adenocarcinoma with unknown origin. However, the function and molecular mechanism of SMAD4 in non-small cell lung cancer (NSCLC) development are largely unknown. Thus, we studied the correlation between SMAD4 mutations and clinico-molecular features in the patients with NSCLC. We reported the frequencies and prognostic values of SMAD4 mutations in a Chinese NSCLC cohort using next-generation sequencing. The NSCLC cases from several public databases, including The Cancer Genome Atlas and others, were also used in this study to elucidate SMAD4-related molecular partners and mechanisms. Integrated bioinformatics analyses were conducted, such as analysis of Gene Ontology enrichment analysis, gene set enrichment analysis (GSEA), and survival analysis. Immunohistochemistry showed that the tissues harboring SMAD4 mutations tended to show SMAD4 deficiency or loss, while SMAD4 expression was significantly reduced at all stages of NSCLC cases. We found that reduced SMAD4 expression was more frequent in the patients with poor disease-free survival and resistance to platinum-based chemotherapy. SMAD4 mutation was an independent risk factor for the survival of NSCLC patients. The expression of SMAD4 was associated with that of SMAD2. The GSEA showed that SMAD4 might promote NSCLC progression by regulating proliferation, adhesion, and immune response. In conclusion, these data suggest that SMAD4 mutation or loss as well as reduced expression can be used to identify the NSCLC patients with poor survival and resistance to platinum-based chemotherapy. SMAD4 may be a predictive marker or therapeutic target in NSCLC. The source code and user's guide are freely available at Github: https://github.com/wangyue77-ab/smad4 .

SMAD-6, -7 and -9 are potential molecular biomarkers for the prognosis in human lung cancer

SMADs, a family of proteins that function as signal transducers and transcriptional regulators to regulate various signaling pathways, including the transforming growth factor-β signaling pathway, are similar to the mothers against decapentaplegic family of genes and the sma gene family in Caenorhabditis elegans. SMADs generate context-dependent modulation by interacting with various sequence-specific transcription factors, such as E2F4/5, c-Fos, GATA3, YY1 and SRF, which have been found to serve a key role in lung carcinoma oncogenesis and progression. However, the prognostic values of the eight SMADs in lung cancer have not been fully understood. In the present study, the expression levels and survival data of SMADs in patients with lung carcinoma from the Oncomine, Gene Expression Profiling Interactive Analysis, Kaplan-Meier plotter and cBioPortal databases were downloaded and analyzed. It was found that the mRNA expression levels of SMAD-6, -7 and -9 were decreased in lung adenocarcinoma and squamous cell carcinoma compared with that in adjacent normal tissues, while there was no significant difference in SMADs 1-5. Survival analysis revealed that not only were low transcriptional levels of SMAD-6, -7 and -9 associated with low overall survival but they also had prognostic role for progression-free survival and post-progression survival (P<0.05) in patients with lung carcinoma. In conclusion, the present study demonstrated that SMAD-6, -7 and -9 are potential biomarkers for the prognosis of patients with lung carcinoma.

Activin-like kinase 5 (ALK5) inactivation in the mouse uterus results in metastatic endometrial carcinoma

The rising incidence of endometrial cancer in the United States and worldwide can be partially attributed to elevated rates of obesity in the population. Although hysterectomy is an effective treatment for early endometrial cancer, medical interventions are required in advanced cases with metastatic disease or for women wishing to preserve fertility. Here, we present a mouse model with conditional inactivation of the transforming growth factor β (TGFβ) receptor, activin-like kinase 5 (Alk5), that develops estrogen-dependent endometrial adenocarcinoma with distant lung metastases. We anticipate that this mouse will be a useful preclinical model for testing novel therapies for endometrial cancer and for understanding the mechanisms that control endometrial regeneration in the postpartum uterus.

The endometrial lining of the uterine cavity is a highly dynamic tissue that is under the continuous control of the ovarian steroid hormones, estrogen and progesterone. Endometrial adenocarcinoma arises from the uncontrolled growth of the endometrial glands, which is typically associated with unopposed estrogen action and frequently occurs in older postmenopausal women. The incidence of endometrial cancer among younger women has been rising due to increasing rates of obesity, a major risk factor for the disease. The transforming growth factor β (TGFβ) family is a highly conserved group of proteins with roles in cellular differentiation, proliferation, and cancer. Inactivating mutations in the genes encoding the TGFβ cell surface receptors (TGFBR1/ALK5 and TGFBR2) have been detected in various human cancers, indicating that a functional TGFβ signaling pathway is required for evading tumorigenesis. In this study, we present a mouse model with conditional inactivation of activin receptor-like kinase 5 (ALK5) in the mouse uterus using progesterone receptor cre (“Alk5 cKO”) that develops endometrial adenocarcinoma with metastasis to the lungs. The cancer and metastatic lung nodules are estrogen dependent and retain estrogen receptor α (ERα) reactivity, but have decreased levels of progesterone receptor (PR) protein. The endometrial tumors develop only in Alk5 cKO mice that are mated to fertile males, indicating that TGFβ-mediated postpartum endometrial repair is critical for endometrial function. Overall, these studies indicate that TGFβ signaling through TGFBR1/ALK5 in the endometrium is required for endometrial homeostasis, tumor suppression, and postpartum endometrial regeneration.

Targeted sequencing reveals distinct pathogenic variants in Chinese patients with lung adenocarcinoma brain metastases

Lung cancer is the most common type of malignancy to metastasize to the brain, with the median survival time of patients being 6-11 months. In the present study, the aim was to compare the actionable gene mutation profiles of primary lung adenocarcinoma (LC) samples and LC brain metastasis (LCBM) samples through targeted sequencing. Next generation sequencing (NGS) of 13 formalin-fixed, paraffin-embedded LC samples and 15 LCBM samples was performed using a customized OncoAim™ cancer panel and OncoAim™ RNA fusion panel on the MiSeq platform. The OncoAim™ cancer panel pipeline and OncoAim™ RNA fusion panel pipeline were used for bioinformatic analysis. Together, 43 variants were observed in 7 genes from the 28 cancer samples. The mutated genes of LCBM were tumor protein (TP)53, epidermal growth factor receptor (EGFR), catenin β1, phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit α, mothers against decapentaplegic homolog 4, Kirsten rat sarcoma viral oncogene homolog (KRAS) and proto-oncogene B-Raf, which were exhibited in 10/15 (66.7%), 6/15 (40.0%), 3/15 (20.0%), 2/15 (13.3%), 2/15 (13.3%), 1/15 (6.7%) and 1/15 (6.7%) of samples, respectively. The mutated genes of LC were TP53, EGFR and KRAS, which were exhibited in 11/13 (84.6%), 5/13 (38.5%) and 2/13 (18.2%) of samples, respectively. echinoderm microtubule associated protein like 4-anaplastic lymphoma kinase rearrangements were present in 1 LCBM sample. For 2 LC samples and 1 LCBM sample, no genetic alterations were observed. The NGS data also revealed a novel 4-codon deletion of TP53 (p.V166_H169del) and a novel TP53 splice site mutation (7577157-63del TACTCAG). Further potentially actionable mutations were detected in LCBM, indicating a high degree of genetic heterogeneity between the LC and LCBM samples that were analyzed. The present study demonstrated that NGS provides an improved approach for the discovery of potentially actionable mutations and the understanding of the mechanisms underlying tumor progression and evolution.

Increased Expression of TGFβR2 Is Associated with the Clinical Outcome of Non-Small Cell Lung Cancer Patients Treated with Chemotherapy

To investigate the prognostic significance of TGFβR2 expression and chemotherapy in Chinese non-small cell lung cancer (NSCLC) patients, TGFβR2 expression NSCLC was analyzed in silico using the Oncomine database, and subsequently analyzed with quantitative RT-PCR in 308 NSCLC biopsies, 42 of which were paired with adjacent non-neoplastic tissues. Our results show that TGFβR2 expression was also increased in NSCLC biopsies relative to normal tissue samples and correlated with poor prognosis. TGFβR2 expression was also significantly correlated with other clinical parameters such as tumor differentiation, invasion of lung membrane, and chemotherapy. Moreover, overall survival (OS) and disease free survival (DFS) was increased in patients with low TGFβR2 expressing NSCLC and who had undergone chemotherapy. Thus, high expression of TGFβR2 is a significant risk factor for decreased OS and DFS in NSCLC patients. Thus, TGFβR2 is a potential prognostic tumor biomarker for chemotherapy.

MicroRNA-224 promotes tumor progression in nonsmall cell lung cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. Despite advancements and improvements in surgical and medical treatments, the survival rate of lung cancer patients remains frustratingly poor. Local control for early-stage nonsmall cell lung cancer (NSCLC) has dramatically improved over the last decades for both operable and inoperable patients. However, the molecular mechanisms of NSCLC invasion leading to regional and distant disease spread remain poorly understood. Here, we identify microRNA-224 (miR-224) to be significantly up-regulated in NSCLC tissues, particularly in resected NSCLC metastasis. Increased miR-224 expression promotes cell migration, invasion, and proliferation by directly targeting the tumor suppressors TNFα-induced protein 1 (TNFAIP1) and SMAD4. In concordance with in vitro studies, mouse xenograft studies validated that miR-224 functions as a potent oncogenic miRNA in NSCLC in vivo. Moreover, we found promoter hypomethylation and activated ERK signaling to be involved in the regulation of miR-224 expression in NSCLC. Up-regulated miR-224, thus, facilitates tumor progression by shifting the equilibrium of the partially antagonist functions of SMAD4 and TNFAIP1 toward enhanced invasion and growth in NSCLC. Our findings indicate that targeting miR-224 could be effective in the treatment of certain lung cancer patients.

Smad4 loss promotes lung cancer formation but increases sensitivity to DNA topoisomerase inhibitors

Non-small cell lung cancer (NSCLC) is a common malignancy with a poor prognosis. Despite progress targeting oncogenic drivers, there are no therapies targeting tumor suppressor loss. Smad4 is an established tumor suppressor in pancreatic and colon cancer, however, the consequences of Smad4 loss in lung cancer are largely unknown. We evaluated Smad4 expression in human NSCLC samples and examined Smad4 alterations in large NSCLC datasets and found that reduced Smad4 expression is common in human NSCLC and occurs through a variety of mechanisms including mutation, homozygous deletion, and heterozygous loss. We modeled Smad4 loss in lung cancer by deleting Smad4 in airway epithelial cells and found that Smad4 deletion both initiates and promotes lung tumor development. Interestingly, both Smad4−/− mouse tumors and human NSCLC samples with reduced Smad4 expression demonstrated increased DNA damage while Smad4 knockdown in lung cancer cells reduced DNA repair and increased apoptosis after DNA damage. In addition, Smad4 deficient NSCLC cells demonstrated increased sensitivity to both chemotherapeutics that inhibit DNA topoisomerase and drugs that block double strand DNA break repair by non-homologous end joining. In sum, these studies establish Smad4 as a lung tumor suppressor and suggest that the defective DNA repair phenotype of Smad4 deficient tumors can be exploited by specific therapeutic strategies.

Driver gene mutations of non-small-cell lung cancer are rare in primary carcinoids of the lung: NGS study by ion Torrent

Lung carcinoids are rare neuroendocrine tumors of the lung. Very little is known about the genetic background of these tumors. We applied Ion Torrent Ampliseq next-generation technology to study hotspot mutations of 22 lung cancer-related genes from typical and atypical lung carcinoid tumors. DNA isolated from 25 formalin-fixed, paraffin-embedded carcinoid tumors were amplified to prepare barcoded libraries covering 507 mutations included in 90 amplicons. The libraries were pooled, purified, enriched, and sequenced on ion personal genome machine. The sequences were aligned and checked for known and novel variations using Torrent Suite Software v.4.0.2. One out of 25 patients had mutations in the targeted regions sequenced. This patient had mutations in BRAF, SMAD4, PIK3CA, and KRAS. All these mutations were confirmed as somatic and are previously known mutations. In summary, mutations in genes commonly mutated in non-small-cell lung cancer are not common in lung carcinoids.

P130cas is required for TGF-β1-mediated epithelial-mesenchymal transition in lung cancer

In lung cancer A549 cells, the present study evaluated the associations between p130cas expression and the activation of p38 or Smad2, which are components of two of the main signaling pathways of transforming growth factor-β1 (TGF-β1), i.e., epithelial-mesenchymal transition (EMT) and apoptosis, respectively. TGF-β1-induced EMT was investigated by inspecting cell shape and cell migration, and by testing E-Cadherin, N-Cadherin and Vimentin biomarkers in p130cas-RNA interference (RNAi)-A549 cells. The changes in TGF-β1-induced apoptosis, i.e., cleaved Caspase-3 levels, were additionally analyzed following p130cas-RNAi. p130cas-knockdown decreased the phosphorylated (p)-p38 expression level, and blockaded the TGF-β1-induced activation of p-p38 in the A549 cells. p130cas-knockdown arrested cell migration and impaired TGF-β1-induced EMT in the A549 cells, characterized by changes in cell morphology and biomarker levels. However, p130cas-knockdown had no impact on the activation of Smad2 and the cleavage of Caspase-3. These results indicate that p130cas is a novel molecular ‘rheostat’ that alters the function of the TGF-β1 signaling pathway from tumor suppression to tumor promotion in lung cancer cells. The underlying mechanism warrants further study.

Mesenchymal-transitioned cancer cells instigate the invasion of epithelial cancer cells through secretion of WNT3 and WNT5B

Although the heterogeneities of epithelial and mesenchymal-transitioned cancer cells are often observed within the tumor microenvironment, the biological significance of the interaction between epithelial cancer cells and mesenchymal-transitioned cancer cells is not yet understood. In this study, we show that the mesenchymal-transitioned cancer cells instigate the invasive ability and metastatic potential of the neighboring epithelial cancer cells in vitro and in vivo. We identify WNT3 and WNT5B as critical factors secreted from Transforming growth factor-induced mesenchymal cancer cells for instigating the epithelial cancer cell invasion along with the induction of secondary EMT phenotype. These results shed light on the significance of cancer heterogeneity and the interaction between epithelial and mesenchymal-transitioned cancer cells within the tumor microenvironment in promoting metastatic disease through the WNT-dependent mechanism.

Systems biology approach to stage-wise characterization of epigenetic genes in lung adenocarcinoma

Background

Epigenetics refers to the reversible functional modifications of the genome that do not correlate to changes in the DNA sequence. The aim of this study is to understand DNA methylation patterns across different stages of lung adenocarcinoma (LUAD).

Results

Our study identified 72, 93 and 170 significant DNA methylated genes in Stages I, II and III respectively. A set of common 34 significant DNA methylated genes located in the promoter section of the true CpG islands were found across stages, and these were: HOX genes, FOXG1, GRIK3, HAND2, PRKCB, etc. Of the total significant DNA methylated genes, 65 correlated with transcription function. The epigenetic analysis identified the following novel genes across all stages: PTGDR, TLX3, and POU4F2. The stage-wise analysis observed the appearance of NEUROG1 gene in Stage I and its re-appearance in Stage III. The analysis showed similar epigenetic pattern across Stage I and Stage III. Pathway analysis revealed important signaling and metabolic pathways of LUAD to correlate with epigenetics. Epigenetic subnetwork analysis identified a set of seven conserved genes across all stages: UBC, KRAS, PIK3CA, PIK3R3, RAF1, BRAF, and RAP1A. A detailed literature analysis elucidated epigenetic genes like FOXG1, HLA-G, and NKX6-2 to be known as prognostic targets.

Conclusion

Integrating epigenetic information for genes with expression data can be useful for comprehending in-depth disease mechanism and for the ultimate goal of better target identification.

TGF-β1, Smad-2/-3, Smad-1/-5/-8, and Smad-4 signaling factors are expressed in ameloblastomas, adenomatoid odontogenic tumors, and calcifying cystic odontogenic tumors: an immunohistochemical study

OBJECTIVES

The TGF-β/Smad signaling pathway regulates diverse cellular functions, including tooth development, and is involved in numerous pathological processes such as tumorigenesis. The aim of this study was to investigate the immunoexpression of the TGF-β/Smad signaling pathway members in ameloblastoma (AM), calcifying cystic odontogenic tumor (CCOT), and adenomatoid odontogenic tumor (AOT).

MATERIALS AND METHODS

This retrospective cross-sectional study included 65 tissue specimens: 34 AMs, 13 CCOTs, and 18 AOTs. Serial sections were immunohistochemically stained with TGF-β1, Smad-4, Smad-1/-5/-8, and Smad-2/-3 antibodies, and a semiquantitative measurement of the positive cells was carried out by two oral pathologists using a 0-3 scale (0: no immunoreactivity, 1: <20% positive cells, 2: 20-50% positive cells, 3: >50% positive cells).

RESULTS

All biomarkers studied were found significantly decreased in AM compared to CCOT and AOT. AOT and CCOT expressed Smad-1/-5/-8 more strongly compared to AM (OR = 11.66, P < 0.001 and OR = 5.34, P = 0.013, respectively), and Smad-2/-3 immunostaining was found significantly increased in CCOT (OR = 10.42, P = 0.001) and AOT (OR = 5.16, P < 0.004) compared to AM. Similarly, Smad-4 was expressed more strongly in AOT and CCOT compared to AM (P = 0.001), while AOT demonstrated a fivefold higher chance to express TGF-β1 compared to AM (P = 0.011).

CONCLUSION

TGF-β/Smad signaling pathway is activated in AM, AOT, and CCOT. The statistically significant reduced TGF-β1/Smad immunoexpression in AM compared to AOT/CCOT could be associated with the more aggressive biological behavior of AM including increased cell proliferation and reduced apoptosis and differentiation. Thus, the biomarkers TGF-β, Smad-4, Smad-1/-5/-8, and Smad-2/-3 could serve as supplementary diagnostic indices between odontogenic tumors of high and low neoplastic dynamics.

Smad3 regulates E-cadherin via miRNA-200 pathway

To identify potential microRNA (miRNA) links between Smad3, a mediator of TGF-β (transforming growth factor-β) signaling, and E-cadherin, we characterized the miRNA profiles of two gastric cancer cell lines: SNU484-LPCX, which does not express Smad3, and SNU484-Smad3, in which Smad3 is overexpressed. We found that among differentially expressed miRNAs, miR-200 family members are overexpressed in SNU484-Smad3 cells. Subsequent studies, including analysis of the effects of silencing Smad3 in SNU484-Smad3 cells and a luciferase reporter assay, revealed that Smad3 directly binds to a Smad-binding element located in the promoter region of miR-200b/a, where it functions as a transcriptional activator. TGF-β did not affect the regulatory role of Smad3 in transcription of miR-200 and expression of epithelial-mesenchymal transition markers. We conclude that Smad3 regulates, at the transcriptional level, miR-200 family members, which themselves regulate ZEB1 and ZEB2, known transcriptional repressors of E-cadherin, at the posttranscriptional level in a TGF-β-independent manner. This represents a novel link between Smad3 and posttranscriptional regulation by miRNAs in epithelial-mesenchymal transition in gastric cancer cells.

The tale of transforming growth factor-beta (TGFbeta) signaling: a soigné enigma

Transforming growth factor-beta (TGFbeta) is a secreted cytokine, which intricately controls a plethora of physiological and pathological processes during development and carcinogenesis. TGFbeta exerts antiproliferative effects and functions as a tumor suppressor during early stages of tumorigenesis, whereas at later stages it functions as a tumor promoter aiding in metastatic progression through an autocrine TGFbeta loop. Intricate knowledge of TGFbeta signaling and its regulation are still evolving. In this review, we make an attempt to showcase the associated enigma of TGFbeta signaling in its dual functional role as tumor suppressor and metastatic promoter during early and late stages of carcinogenesis, respectively.

Identification of novel Smad2 and Smad3 associated proteins in response to TGF-beta1

Transforming growth factor-beta 1 (TGF-beta1) is an important growth inhibitor of epithelial cells and insensitivity to this cytokine results in uncontrolled cell proliferation and can contribute to tumorigenesis. TGF-beta1 signals through the TGF-beta type I and type II receptors, and activates the Smad pathway via phosphorylation of Smad2 and Smad3. Since little is known about the selective activation of Smad2 versus Smad3, we set out to identify novel Smad2 and Smad3 interacting proteins in epithelial cells. A non-transformed human cell line was transduced with Myc-His(6)-Smad2 or Myc-His(6)-Smad3-expressing retrovirus and was treated with TGF-beta1. Myc-His(6)-Smad2 or Myc-His(6)-Smad3 was purified by tandem affinity purification, eluates were subject to SDS-PAGE and Colloidal Blue staining, and select protein bands were digested with trypsin. The resulting tryptic peptides were analyzed by liquid chromatography (LC) and tandem mass spectrometry (MS/MS) and the SEQUEST algorithm was employed to identify proteins in the bands. A number of proteins that are known to interact with Smad2 or Smad3 were detected in the eluates. In addition, a number of putative novel Smad2 and Smad3 associated proteins were identified that have functions in cell proliferation, apoptosis, actin cytoskeleton regulation, cell motility, transcription, and Ras or insulin signaling. Specifically, the interaction between Smad2/3 and the Cdc42 guanine nucleotide exchange factor, Zizimin1, was validated by co-immunoprecipitation. The discovery of these novel Smad2 and/or Smad3 associated proteins may reveal how Smad2 and Smad3 are regulated and/or uncover new functions of Smad2 and Smad3 in TGF-beta1 signaling.

Reassessing epithelial to mesenchymal transition as a prerequisite for carcinoma invasion and metastasis

For most carcinomas, progression toward malignancy is accompanied by loss of epithelial differentiation and a shift towards a mesenchymal phenotype. This process, referred to as epithelial to mesenchymal transition (EMT), exacerbates motility and invasiveness of many cell types and is often considered a prerequisite for tumor infiltration and metastasis. However, there are numerous examples of advanced carcinomas that adopt some mesenchymal features, yet retain characteristics of well-differentiated epithelial cells. We provide a review of these reports and describe mechanisms to explain the morphologic and molecular heterogeneity and plasticity of malignant carcinoma cells, including incomplete EMT, reversion to an epithelial phenotype, and collective migration. We suggest that these mechanisms can manifest in a series of independent and reversible steps and that EMT represents just one mechanism in the global metastatic carcinoma development process.

Roles of Smad3 in TGF-beta signaling during carcinogenesis

Signaling of transforming growth factor beta (TGF-beta) is mediated through a heteromeric complex of two types of transmembrane receptors and downstream intracellular proteins known as Smads. Alterations of TGF-beta signaling underlie various forms of human cancer and developmental diseases. Human genetic studies have revealed both point mutations and deletions of Smad2 or Smad4 in several types of cancers. However, the role of Smad3 in tumorigenesis is not clear. Recent data indicate that Smad3 also functions as a tumor suppressor by inhibiting cell proliferation and promoting apoptosis. In addition, Smad3 is essential for TGF-beta-mediated immune suppression, and it plays an important role in regulating transcriptional responses that are favorable to metastasis. Therefore, through regulating different transcriptional responses, Smad3 functions as both a negative and positive regulator of carcinogenesis depending on cell type and clinical stage of the tumor.

Mechanisms of action of TGF-beta in cancer: evidence for Smad3 as a repressor of the hTERT gene

Transforming growth factor-beta (TGF-beta) induces cell differentiation and suppresses cell proliferation, but the mechanisms underlying the actions of TGF-beta remain to be fully elucidated. Recent studies suggest that TGF-beta suppresses neoplastic cell development by employing Smad3 protein to repress the gene of human telomerase reverse transcriptase (hTERT). In human breast cancer cells, TGF-beta induces rapid phosphorylation and subsequent entry of Smad3 into the nucleus. In the nucleus, Smad3 binds to the hTERT gene promoter directly and inhibits hTERT gene transcription activity. By interacting with c-myc, Smad3 also represses the c-myc gene. Thus, TGF-beta prevents continuous cell proliferation by switching off telomerase activity through Smad3 repression of the hTERT gene and the action of c-myc. Modulating the interface between Smad3 and the hTERT gene, and the potential feedback loop from telomeres to Smad3 via Smurf2, may represent a novel approach to regulate cell lifespan of proliferation.

CLCP1 interacts with semaphorin 4B and regulates motility of lung cancer cells

We previously established a highly metastatic subline, LNM35, from the NCI-H460 lung cancer cell line, and demonstrated upregulation of a novel gene, CLCP1 (CUB, LCCL-homology, coagulation factor V/VIII homology domains protein), in LNM35 and lung cancer specimens. In this study, we focused on the potential roles of that gene in cancer metastasis. First, we established stable LNM35 RNAi clones, in which CLCP1 expression was suppressed by RNAi, and found that their motility was significantly reduced, although growth rates were not changed. Next, in vitro selection of a phage display library demonstrated that a phage clone displaying a peptide similar to a sequence within the Sema domain of semaphorin 4B (SEMA4B) interacted with LNM35. Immunoprecipitation experiments confirmed interaction of CLCP1 with SEMA4B, regulation of CLCP1 protein by ubiquitination and proteasome degradation enhanced in the presence of SEMA4B. These results are the first to indicate that CLCP1 plays a role in cell motility, whereas they also showed that at least one of its ligands is SEMA4B and that their interaction mediates proteasome degradation by CLCP1. Although the physiological role of the interaction between CLCP1 and SEMA4B remains to be investigated, this novel gene may become a target of therapy to inhibit metastasis of lung cancers.

Role of cell-cycle regulators in lung cancer

Lung cancer is the leading cause of cancer death worldwide. Histologically, 80% of lung cancers are classified as non-small-cell lung cancer (NSCLC), and the remaining 20% as small-cell lung cancer (SCLC). Lung carcinoma is the result of molecular changes in the cell, resulting in the deregulation of pathways controlling normal cellular growth, differentiation, and apoptosis. This review summarizes some of the most recent findings about the role of cell-cycle proteins in lung cancer pathogenesis and progression.

Histone modification in the TGFbetaRII gene promoter and its significance for responsiveness to HDAC inhibitor in lung cancer cell lines

We previously reported silencing of the TGF-beta type II receptor gene (TGFbetaRII), involving histone deacetylation, instead of DNA methylation (DNA-Me). Because different histone modifications may play crucial roles in the epigenetic alterations, we further studied links with silencing of the TGFbetaRII gene promoter in six lung cancer cell lines. ChIP assays demonstrated three chromatin patterns for this gene silencing (Pattern I: histone H3 acetylation (H3-Ac)(+/-)/histone H3 lysine 4 methylation (H3K4-Me)(+)/DNA-Me(-), Pattern II; H3-Ac(-)/H3K4-Me(+/-)/DNA-Me(-), and Pattern III; H3-Ac(-)/H3K4-Me(-)/DNA-Me(+)), indicating possible progressive alterations with H3K4-Me alteration. With exposure to a histone deacetylase inhibitor (HDAC-I), trichostatin A, cell lines with the pattern II demonstrated strong and persistent induction of TGFbetaRII expression, while those with the pattern III showed only weak or no induction. ACC-LC-91 cell line, one of the pattern II examples demonstrated strong and continuous induction of H3K4-Me similar to TGFbetaRII expression. In contrast, ACC-LC-176 with the pattern III showed only weak and transient induction of H3K4-Me, similar to TGFbetaRII expression. Treatment with 5-aza-2'-deoxycytidine (5aza-dC) in addition to HDAC-I resulted in strong and continuous induction of TGFbetaRII expression and H3K4-Me in ACC-LC-176, although 5aza-dC alone was without such effects. In ACC-LC-91, both H3-Ac and H3K4-Me were promptly and simultaneously induced by HDAC-I, and similarly inhibited by wortmannin, a PI3K family inhibitor, together with TGFbetaRII induction. These findings suggested progressive alterations of chromatin configuration including H3K4-Me alteration in TGFbetaRII gene silencing. A possible involvement of a wortmannin-sensitive kinase in histone modification was also suggested.

Gene deregulation in gastric cancer

Despite its decreasing frequency in the Western world during recent decades, gastric cancer is still one of the leading causes of cancer-related deaths worldwide. Due to the oligosymptomatic course of early gastric cancer, most cases are diagnosed in the advanced stages of the disease. The curative potential of current standard treatment continues to be unsatisfactory, despite multimodal approaches involving surgery, chemotherapy and radiotherapy. Novel therapeutics including small molecules and monoclonal antibodies are being developed and have been partially introduced into clinical use in connection with neoplastic diseases such as chronic myeloid leukemia, non-Hodgkin's lymphoma and colorectal cancer. Thorough understanding of the changes in gene expression occurring during gastric carcinogenesis may help to develop targeted therapies and improve the treatment of this disease. Novel molecular biology techniques have generated a wealth of data on up- and down-regulation, activation and inhibition of specific pathways in gastric cancer. Here, we provide an overview of the different aspects of aberrant gene expression patterns in gastric cancer.

Smads as intracellular mediators of airway inflammation

Transforming growth factor-beta (TGF-beta) plays an important role in the pathogenesis of allergic asthma and other airway diseases. Signals from the activated TGF-beta receptor complex are transduced to the nucleus of airway cells by Smad proteins, which represent a family of transcription factors that have recently been implicated to play a major role as intracellular mediators of inflammation. The Smad family consists of the receptor-regulated Smads, a common pathway Smad, and inhibitory Smads. Receptor-regulated Smads (R-Smads) are phosphorylated by the TGF-beta type Ireceptor. They include Smad2 and Smad3, which are recognized by TGF-beta and activin receptors, and Smads 1, 5, 8, and 9, which are recognized by bone morphogenetic protein (BMP) receptors. Smad4 is a common pathway Smad, which is also defined as cooperating Smad (co-Smad) and is not phosphorylated by the TGF-beta type I receptor. Inhibitory Smads(anti-Smads) include Smad6 and Smad7, which down-regulate TGF-beta signaling. To date, the Smads are the only TGF-beta receptor substrates with a demonstrated ability to propagate signals and with regard to the growing number of investigations of Smad-mediated effects in the airways, Smads may prove to be an important target for future development of new therapeutic strategies for asthma and chronic obstructive pulmonary disease.

Induction by transforming growth factor-beta1 of epithelial to mesenchymal transition is a rare event in vitro

INTRODUCTION

Transforming growth factor (TGF)-beta1 is proposed to inhibit the growth of epithelial cells in early tumorigenesis, and to promote tumor cell motility and invasion in the later stages of carcinogenesis through the induction of an epithelial to mesenchymal transition (EMT). EMT is a multistep process that is characterized by changes in cell morphology and dissociation of cell-cell contacts. Although there is growing interest in TGF-beta1-mediated EMT, the phenotype is limited to only a few murine cell lines and mouse models.

METHODS

To identify alternative cell systems in which to study TGF-beta1-induced EMT, 18 human and mouse established cell lines and cultures of two human primary epithelial cell types were screened for TGF-beta1-induced EMT by analysis of cell morphology, and localization of zonula occludens-1, E-cadherin, and F-actin. Sensitivity to TGF-beta1 was also determined by [3H]thymidine incorporation, flow cytometry, phosphorylation of Smad2, and total levels of Smad2 and Smad3 in these cell lines and in six additional cancer cell lines.

RESULTS

TGF-beta1 inhibited the growth of most nontransformed cells screened, but many of the cancer cell lines were insensitive to the growth inhibitory effects of TGF-beta1. In contrast, TGF-beta1 induced Smad2 phosphorylation in the majority of cell lines, including cell lines resistant to TGF-beta1-mediated cell cycle arrest. Of the cell lines screened only two underwent TGF-beta1-induced EMT.

CONCLUSION

The results presented herein show that, although many cancer cell lines have lost sensitivity to the growth inhibitory effect of TGF-beta1, most show evidence of TGF-beta1 signal transduction, but only a few cell lines undergo TGF-beta1-mediated EMT.

Loss of the Smad3 expression increases susceptibility to tumorigenicity in human gastric cancer

Loss of the tumor suppressive effect of transforming growth factor-beta (TGF-beta) has been commonly found at later stages in carcinogenic progression. Although the genes encoding TGF-beta receptors and Smads have been found genetically altered in certain human cancers, no mutation in Smad3 has been observed. Therefore, suppression of Smad3 expression may mediate key oncogenic properties of TGF-beta. First, we observed that 37.5% of human gastric cancer tissues showed low to undetectable levels of Smad3 and that in nine human gastric cancer cell lines examined, two showed deficient Smad3 expression. Introduction of Smad3 into human gastric cancer cells that did not express Smad3, restored TGF-beta responsiveness: induction of p21 and p15 gene expression, and growth inhibition in response to TGF-beta. Furthermore, these Smad3-expressing cells showed markedly decreased and delayed tumorigenicity in vivo. These findings suggest that Smad3 expression may have a critical role in tumor suppression in the early stages of gastric carcinogenesis.

BMP4 signaling induces senescence and modulates the oncogenic phenotype of A549 lung adenocarcinoma cells

Lung cancer is the most common visceral malignancy in males, with rapidly increasing incidence in females, and a devastatingly poor prognosis. Transforming growth factor (TGF)-beta has been shown to induce senescence in A549 lung cancer cells, and both TGF-beta and bone morphogenetic protein (BMP) 2 can suppress the transformed phenotype of A549 cells in vitro. We examined the effects of BMP4, another member of the TGF-beta superfamily, on specific oncogenic properties of A549 cancer cells. When A549 cancer cells were treated continuously with 100 ng/ml of BMP4, a senescent phenotype was observed after 2 wk of treatment. The BMP-treated cells appeared larger than untreated cells, grew more slowly, had more senescence-associated beta-galactosidase activity, and had less telomerase activity, as measured by the telomeric repeat amplification protocol assay. Invasion through Engelbreth Holm-Swarm matrix was inhibited in the senescent cell population. Senescent BMP4-treated cells had lower ERK activation, VEGF expression, and Bcl2 expression than wild-type cells, consistent with a less proliferative, less angiogenic phenotype with increased susceptibility to death by apoptosis. BMP4 treatment also resulted in sustained elevation of Smad1. In vivo xenograft studies in the flanks of nude mice confirmed that the BMP-treated cells were significantly less tumorigenic than untreated cells. Direct overexpression of Smad1 using adenoviral constructs resulted in cell death within 5 days. These studies suggest that BMP4 pathway signaling can induce senescence and thus negatively regulate the growth of A549 lung cancer cells.

Reconstitution of Smad3 restores TGF-beta response of tissue inhibitor of metalloprotease-1 upregulation in human choriocarcinoma cells

Extravillous trophoblast (EVT) cells of the human placenta proliferate, migrate, and invade the pregnant uterus and its vasculature in order to nourish the fetus. However, the normal EVT cell proliferation, migration, and invasiveness are exquisitely controlled in situ by decidua-produced transforming growth factor-beta (TGF-beta), whereas EVT cancer (choriocarcinoma) cells are TGF-beta-resistant. We found that these cells lack in expression of Smad3, a key transcription factor involved in TGF-beta signaling pathway. To test whether Smad3 restitution restores TGF-beta response in choriocarcinoma cells, we produced a Smad3-expressing cell line (JAR-smad3/c). Since anti-invasive effect of TGF-beta in the normal EVT cells was partly mediated by an upregulation of tissue inhibitor of metalloprotease (TIMP)-1, we examined whether Smad3-restituted JAR cells have restored TGF-beta response of TIMP-1 upregulation. The expression of TIMP-1 mRNA was found to be low in JAR and JAR-smad3/c cells. Moreover, the basal level of secreted TIMP-1 protein was very low in these cells as compared to the normal EVT cells. TGF-beta1 upregulated TIMP-1 mRNA and secreted protein in Smad3-restituted JAR cells as well as in the normal EVT cells, whereas no effect was detected in Smad3-deficient (wild-type) JAR cells. We had earlier shown that Smad3-restituted JAR cells had also restored TGF-beta response of plasminogen activator inhibitor-1 upregulation. However, in vitro functional analysis revealed that, in contrast to the normal EVT cells, anti-invasive action of TGF-beta was not restored in Smad3-restituted JAR cells. Thus, additional factors (possibly low expression of Smad4 and/or other unknown factors) may contribute to refractoriness to anti-invasive action of TGF-beta in JAR cells.

Lack of correlation between growth inhibition by TGF-beta and the percentage of cells expressing type II TGF-beta receptor in human non-small cell lung carcinoma cell lines

To determine the mechanisms involved in the evasion from TGF-beta growth regulation in the small cell lung carcinoma (SCLC) cell lines and the non-small cell lung carcinoma (NSCLC) cell lines, we studied: (a) production of TGF-beta1 and TGF-beta2; (b) percentage of cells expressing TGF-beta RII; (c) responsiveness of the tumour cell lines to exogenous TGF-beta1 or TGF-beta2; and (d) presence of mRNA transcripts of the three TGF-beta isoforms and of the TGF-beta RII. Our results indicate that the SCLC cell lines do not synthesize the isoforms TGF-beta1 and TGF-beta2 nor the TGF-beta RII, thus avoiding inhibitory autocrine and paracrine TGF-beta actions. However, NSCLC cell lines express not only TGF-beta1, TGF-beta2 and TGF-beta RII mRNA transcripts, but also synthesize both isoforms and the TGF-beta RII. Although approximately 50% of the cells from the studied cell lines expressed the TGF-beta RII, different cell lines varied greatly in the sensitivity to the inhibitory action of TGF-beta. This could result from alterations in: (i) the structure of TGF-beta RII; (ii) the phosphorylation motif of TGF-beta RI; (iii) the molecules involved in the intracellular signalling pathway of TGF-beta; and (iv) cell cycle regulation.

Transforming Growth Factor-beta2 protects the small intestine during methotrexate treatment in rats possibly by reducing stem cell cycling

During chemo- and radiation therapy, the balance between epithelial cell proliferation, differentiation, and cell death at the villus tip is disrupted by premature death of dividing epithelial cells. This will subsequently lead to the onset of mucosal barrier injury in the whole gastrointestinal tract. Up till now there is no validated method to treat side effects occurring due to therapy. An approach to manage this side effect might be to reversibly arrest growth of epithelial stem cells during therapy using Transforming Growth Factor-beta2. A Transforming Growth Factor-beta2 enriched fraction prepared from bovine milk was shown to protect small intestinal epithelial cells against cell cycle specific chemotherapeutic agents by arresting the cells in G1-phase. Secondly, in a rat model for induced small intestinal damage, oral supplementation of rats exposed to methotrexate with the Transforming Growth Factor-beta2 enriched fraction significantly reduced the chemotherapy-associated weight loss and ileal villus atrophy by reducing cell proliferation in the normal stem cell population. Thus oral supplementation with a bovine milk fraction enriched for Transforming Growth Factor-beta2 attenuated the side effects of chemotherapy in the small intestine in rats.

Restoration of TGF-beta regulation of plasminogen activator inhibitor-1 in Smad3-restituted human choriocarcinoma cells

Proliferation, migration, and invasiveness of the normal placental extravillous trophoblast (EVT) cells are negatively regulated by transforming growth factor-beta (TGF-beta), whereas malignant EVT (JAR and JEG-3 choriocarcinoma) cells are resistant to TGF-beta. These malignant cells were found to have lost the expression of Smad3. Present study examined whether Smad3 restitution in JAR cells could restore TGF-beta response. We produced a stable Smad3 cDNA-transfected clone (JAR-smad3/c) which exhibited further upregulation of Smad3 in the presence of TGF-beta1. Since anti-invasive effects of TGF-beta in the normal EVT cells were shown to be mediated in part by plasminogen activator inhibitor-1 (PAI-1) and urokinase-type plasminogen activator (uPA), we compared the expression of PAI-1 and uPA in the normal EVT, JAR, and JAR-smad3/c cells in the presence or absence of TGF-beta1. The basal levels of PAI-1 mRNA and secreted PAI-1 and uPA proteins were found to be very low in JAR and JAR-smad3/c cells, as compared to the normal EVT cells. However, TGF-beta1 upregulated PAI-1 and downregulated uPA in JAR-smad3/c cells, but not in JAR cells. Thus, resistance of choriocarcinoma cells to anti-invasive effects of TGF-beta may, at least in part, be due to loss of Smad3 expression.

Suppressor and oncogenic roles of transforming growth factor-beta and its signaling pathways in tumorigenesis

Transforming growth factor-beta (TGF-beta) has been implicated in oncogenesis since the time of its discovery almost 20 years ago. The complex, multifunctional activities of TGF-beta endow it with both tumor suppressor and tumor promoting activities, depending on the stage of carcinogenesis and the responsivity of the tumor cell. Dysregulation or alteration of TGF-beta signaling in tumorigenesis can occur at many different levels, including activation of the ligand, mutation or transcriptional suppression of the receptors, or alteration of downstream signal transduction pathways resulting from mutation or changes in expression patterns of signaling intermediates or from changes in expression of other proteins which modulate signaling. New insights into signaling from the TGF-beta receptors, including the identification of Smad signaling pathways and their interaction with mitogen-activated protein (MAP) kinase pathways, are providing an understanding of the changes involved in the change from tumor suppressor to tumor promoting activities of TGF-beta. It is now appreciated that loss of sensitivity to inhibition of growth by TGF-beta by most tumor cells is not synonymous with complete loss of TGF-beta signaling but rather suggests that tumor cells gain advantage by selective inactivation of the tumor suppressor activities of TGF-beta with retention of its tumor promoting activities, especially those dependent on cross talk with MAP kinase pathways and AP-1.

Human placental trophoblast as an in vitro model for tumor progression

The human placenta is a highly invasive tumor-like structure in which a subpopulation of placental trophoblast cells known as the "extravillous trophoblast" (EVT) invades the uterine decidua and its vasculature to establish adequate fetal-maternal exchange of molecules. By utilizing in vitro-propagated short-lived EVT cell lines we found that molecular mechanisms responsible for their invasiveness are identical to those of cancer cells; however, unlike cancer cells, their proliferation, migration, and invasiveness in situ are stringently controlled by decidua-derived transforming growth factor (TGF)-beta. By SV40T antigen transfection of normal EVT cells followed by a forced crisis regimen in culture we produced an immortalized premalignant derivative that is hyperproliferative, hyperinvasive, and deficient in gap-junctional intercellular communication. Both premalignant and malignant EVT (JAR and JEG-3 choriocarcinoma) cell lines were found to be TGF-beta-resistant. Using these cell lines, we investigated genetic changes responsible for transition of the normal EVT cells to premalignant and malignant phenotype. Hyperinvasiveness in both cases resulted from a downregulation of tissue inhibitor of metalloprotease (TIMP)-1 and plasminogen activator inhibitor (PAI)-1 genes. In contrast to normal EVT cells, both cell types failed to upregulate these genes in response to TGF-beta. Loss of TGF-beta response in malignant EVT cells was explained by the loss of expression of Smad3 gene. Differential mRNA display of normal and premalignant EVT cells identified up- and down-regulation of numerous known or novel genes in premalignant EVT cells, with potential oncogenic and (or) tumor-suppressor functions, e.g., loss of fibronectin and insulin-like growth factor binding protein (IGFBP-5). Premalignant EVT cells also lost IGF receptor type 2 (IGFR-II). IGFBP-5 was shown to be a negative regulator of IGF-1-induced proliferation of premalignant EVT cells, so that loss of IGFBP-5 as well as IGFR-II permitted their unrestricted proliferation in an IGF-I-rich microenvironment of the fetal-maternal interface. The present model may be a good prototype for identifying genetic changes underlying epithelial tumor progression.

Expression of TGF-beta signaling genes in the normal, premalignant, and malignant human trophoblast: loss of smad3 in choriocarcinoma cells

We had earlier shown that TGF-beta controls proliferation, migration, and invasiveness of normal human trophoblast cells, whereas premalignant and malignant trophoblast cells are resistant to TGF-beta. To identify signaling defects responsible for TGF-beta resistance in premalignant and malignant trophoblasts, we have compared the expression of TGF-beta signaling molecules in a normal trophoblast cell line (HTR-8), its premalignant derivative (RSVT2/C), and two choriocarcinoma cell lines (JAR and JEG-3). RT-PCR analysis revealed that all these cell lines expressed the mRNA of TGF-beta1, -beta2, and -beta3, TGF-beta receptors type I, II, and III, and post-receptor signaling genes smad2, smad3, smad4, smad6, and smad7 with the exception that TGF-beta2 and smad3 were undetectable in JAR and JEG-3 cells. Immunoblot analysis confirmed the absence of smad3 protein in choriocarcinoma cells. Treatment with TGF-beta1 induced smad3 phosphorylation and smad3 translocation to the nucleus in the normal and premalignant trophoblast cells. These results suggest that loss of smad3 may account for a functional disruption in the TGF-beta signaling pathway in choriocarcinomas, but not in the premalignant trophoblast.

Role of transforming growth factor beta in cancer

Transforming growth factor beta (TGF-beta) is an effective and ubiquitous mediator of cell growth. The significance of this cytokine in cancer susceptibility, cancer development and progression has become apparent over the past few years. TGF-beta plays various roles in the process of malignant progression. It is a potent inhibitor of normal stromal, hematopoietic, and epithelial cell growth. However, at some point during cancer development the majority of transformed cells become either partly or completely resistant to TGF-beta growth inhibition. There is growing evidence that in the later stages of cancer development TGF-beta is actively secreted by tumor cells and not merely acts as a bystander but rather contributes to cell growth, invasion, and metastasis and decreases host-tumor immune responses. Subtle alteration of TGF-beta signaling may also contribute to the development of cancer. These various effects are tissue and tumor dependent. Identifying and understanding TGF-beta signaling pathway abnormalities in various malignancies is a promising avenue of study that may yield new modalities to both prevent and treat cancer. The nature, prevalence, and significance of TGF-beta signaling pathway alterations in various forms of human cancer as well as potential preventive and therapeutic interventions are discussed in this review.

Predictive molecular markers in non-small cell lung cancer

Recent biotechnologic knowledge has enabled the discovery of a cornucopia of genetic abnormalities commonly involved not only in cancer but also in other diseases ranging from the plague to arteriosclerosis. The wealth of possibilities uncovered by this knowledge inspires the hope that today's dream of a unified concept of common treatment for multiple diseases could become a future reality. This review arbitrarily categorizes recent findings into five major areas. First, cisplatin resistance associated with the nucleotide excision repair pathway can help clinical oncologists to choose between cisplatin and noncisplatin combinations. Second, the relevant role of nuclear factor-kappa B as a predictor of chemosensitivity can lead to the development of new drugs abrogating nuclear factor-kappa B expression. Third, the presence of tubulin mutations, which are directly involved in resistance to microtubule-interactive drugs, can guide chemotherapy based on taxane or nontaxane combinations. In addition, certain chromosomal deletions affect genes involved in deoxyribonucleotide synthesis, like ribonucleotide reductase, that intervene in gemcitabine metabolism; this raises interest in investigating deletion at chromosome 11p15.5 as a potential mechanism of gemcitabine resistance. Finally, an overwhelming number of publications have analyzed genes involved in cell cycle regulation and development as predictive markers of survival; however, where these pieces fit into the puzzle of cancer management is still unclear.

Role of transforming growth factor beta in cancer

Transforming growth factor beta (TGF-beta) is an effective and ubiquitous mediator of cell growth. The significance of this cytokine in cancer susceptibility, cancer development and progression has become apparent over the past few years. TGF-beta plays various roles in the process of malignant progression. It is a potent inhibitor of normal stromal, hematopoietic, and epithelial cell growth. However, at some point during cancer development the majority of transformed cells become either partly or completely resistant to TGF-beta growth inhibition. There is growing evidence that in the later stages of cancer development TGF-beta is actively secreted by tumor cells and not merely acts as a bystander but rather contributes to cell growth, invasion, and metastasis and decreases host-tumor immune responses. Subtle alteration of TGF-beta signaling may also contribute to the development of cancer. These various effects are tissue and tumor dependent. Identifying and understanding TGF-beta signaling pathway abnormalities in various malignancies is a promising avenue of study that may yield new modalities to both prevent and treat cancer. The nature, prevalence, and significance of TGF-beta signaling pathway alterations in various forms of human cancer as well as potential preventive and therapeutic interventions are discussed in this review.