Prognostic significance of transforming growth factor beta (TGF-β) signaling axis molecules and E-cadherin in colorectal cancer

The transforming growth factor beta (TGF-β) signaling pathway has been considered both a tumor suppressor and a cancer promoter. Additionally, downregulation of cell adhesion molecules such as E-cadherin plays an important role in the metastatic potential of colorectal cancer (CRC). The aim of the present study was to evaluate TGF-β, TGF-β type I receptor (TGF-βR1), TGF-β type II receptor (TGF-βR2), Smad4, pSmad2/3, and E-cadherin expression in colorectal carcinoma and to correlate the obtained data with other standard prognostic parameters, such as disease stage, metastases, and patient survival. TGF-β, TGF-βR1, TGF-βR2, Smad4, pSmad2/3, and E-cadherin expression was evaluated immunohistochemically in 195 unrelated CRC specimens and the results subjected to various statistical analyses. TGF-β was expressed in 71.28%, TGF-βR1 in 61.0%, TGF-βR2 in 54.4%, Smad4 in 61.5%, pSmad2/3 in 71.3%, and E-cadherin in 50.26% of the colorectal carcinoma samples tested. The correlation of immunoexpression with the clinicopathological parameters of CRC revealed that the high expression of TGF-β and low expression of TGF-βR1, TGF-βR2, Smad4, pSmad2/3, and E-cadherin were correlated with tumor-node-metastasis (TNM) stage of disease. High TGF-β expression and low TGF-βR1, TGF-βR2, Smad4, and pSmad2/3 expression were also correlated with lymph node metastasis. The Kaplan-Meier survival curves demonstrated a clear association of cancer-specific overall survival with high TGF-β, as well as low TGF-βR1, TGF-βR2, Smad4, pSmad2/3, and E-cadherin expression. Our results suggest that TGF-β, TGF-βR1, TGF-βR2, Smad4, pSmad2/3, and E-cadherin are closely related to TNM stage of CRC. Moreover, TGF-β, TGF-βR2, Smad4, pSmad2/3, and E-cadherin emerge as valuable independent biomarkers of prognosis in CRC patients.     

The tumor suppressor Smad4 is required for transforming growth factor beta-induced epithelial to mesenchymal transition and bone metastasis of breast cancer cells

Transforming growth factor beta (TGF-beta) can act as suppressor and promoter of cancer progression. Intracellular Smad proteins (i.e., receptor regulated Smads and common mediator Smad4) play a pivotal role in mediating antimitogenic and proapoptotic effects of TGF-beta, but their function in TGF-beta-induced invasion and metastasis is unclear. Here, we have investigated the role of Smad4 in a cellular and mouse model for TGF-beta-induced breast cancer progression. Consistent with its tumor suppressor function, specific silencing of Smad4 in NMuMG mammary gland epithelial cells using small hairpin RNA (shRNA)-expressing RNAi vectors strongly mitigated TGF-beta-induced growth inhibition and apoptosis. Smad4 knockdown also potently inhibited TGF-beta-induced epithelial to mesenchymal transition of NMuMG cells as measured by morphologic transformation from epithelial to fibroblast-like cells, formation of stress fibers, inhibition of E-cadherin expression, and gain of expression of various mesenchymal markers. Furthermore, we show that knockdown of Smad4 in MDA-MB-231 breast cancer cells strongly inhibited the frequency of bone metastasis in nude mice by 75% and significantly increased metastasis-free survival. Communication of MDA-MB-231 cells with the bone microenvironment, which is needed for optimal tumor cell growth and metastasis, may be affected in Smad4 knockdown cells as TGF-beta-induced expression of interleukin 11 was attenuated on Smad4 knockdown. Taken together, our results show that Smad4 plays an important role in both tumor suppression and progression of breast cancer cells.     

Molecular pathways: targeting the TGF-β pathway for cancer therapy

TGF-β is a ubiquitous cytokine that plays an active role in many cellular processes. Nearly every cell type has the ability to secrete TGF-β, as well as the ability to respond to TGF-β via the presence of TGF-β receptors on the cell surface. Consequently, gain or loss of function of the TGF-β pathway and its components are known to lead to a variety of diseases, including cancer. In epithelial cells, TGF-β functions as a tumor suppressor, where it inhibits proliferation, induces apoptosis, and mediates differentiation. Conversely, in other contexts, TGF-β promotes tumor progression through increasing tumor cell invasion and metastasis. Thus, TGF-β can have opposing roles, likely dependent, in part, on whether the cancer is early or late stage. The effects of TGF-β on tumor suppression and promotion are not limited to the tumor cell itself; rather, these effects can also be mediated through the stroma and the immune system. The dichotomous role of TGF-β in cancer highlights our need to understand the contextual effects of this cytokine to better guide patient selection for the use of anti-TGF-β therapies currently in clinical trials.     

TGF-β and αvβ6 Integrin Act in a Common Pathway to Suppress Pancreatic Cancer Progression

The TGF-β pathway is under active consideration as a cancer drug target based on its capacity to promote cancer cell invasion and to create a protumorigenic microenvironment. However, the clinical application of TGF-β inhibitors remains uncertain as genetic studies show a tumor suppressor function of TGF-β in pancreatic cancer and other epithelial malignancies. Here, we used genetically engineered mouse models to investigate the therapeutic impact of global TGF-β inhibition in pancreatic cancer in relation to tumor stage, genetic profile, and concurrent chemotherapy. We found that αvβ6 integrin acted as a key upstream activator of TGF-β in evolving pancreatic cancers. In addition, TGF-β or αvβ6 blockade increased tumor cell proliferation and accelerated both early and later disease stages. These effects were dependent on the presence of Smad4, a central mediator of TGF-β signaling. Therefore, our findings indicate that αvβ6 and TGF-β act in a common tumor suppressor pathway whose pharmacologic inactivation promotes pancreatic cancer progression. Cancer Res; 72(18); 4840-5. ?2012 AACR.     

Targeting transforming growth factor-β signaling in liver metastasis of colon cancer

Despite a primary tumor suppressor role, there is compelling evidence suggesting that TGF-β can promote tumor growth, invasion and metastasis in advanced stages of colorectal cancer. Blocking these tumor-promoting effects of TGF-β provides a potentially important therapeutic strategy for the treatment of colorectal cancer. However, little is known about how the inhibitors of TGF-β receptor kinases affect colorectal carcinogenesis in vivo. Here, we have observed that a novel dual kinase inhibitor of TGF-β type I and type II receptors, LY2109761, inhibits TGF-β-mediated activation of Smad and non-Smad pathways in CT26 colon adenocarcinoma cells having K-Ras mutation. The inhibitor attenuates the oncogenic effects of TGF-β on cell migration, invasion and tumorigenicity of CT26 cells. Furthermore, LY2109761 decreases liver metastases and prolongs survival in an experimental metastasis model. These findings suggest that the dual kinase inhibitor LY2109761 has potential therapeutic value for metastatic colorectal cancer.     

The prognostic role of TGF-β signaling pathway in breast cancer patients

BackgroundThe transforming growth factor-β (TGF-β) pathway has dual effects on tumor growth. Seemingly, discordant results have been published on the relation between TGF-β signaling markers and prognosis in breast cancer. Improved prognostic information for breast cancer patients might be obtained by assessing interactions among TGF-β signaling biomarkers.Patients and methodsThe expression of nuclear Smad4, nuclear phosphorylated-Smad2 (p-Smad2), and the membranous expression of TGF-β receptors I and II (TβRI and TβRII) was determined on a tissue microarray of 574 breast carcinomas. Tumors were stratified according to the Smad4 expression in combination with p-Smad2 expression or Smad4 in combination with the expression of both TGF-β receptors.ResultsTumors with high expression of TβRII, TβRI and TβRII, and p-Smad2 (P = 0.018, 0.005, and 0.022, respectively), and low expression of Smad4 (P = 0.005) had an unfavorable prognosis concerning progression-free survival. Low Smad4 expression combined with high p-Smad2 expression or low expression of Smad4 combined with high expression of both TGF-β receptors displayed an increased hazard ratio of 3.04 [95% confidence interval (CI) 1.390–6.658] and 2.20 (95% CI 1.464–3.307), respectively, for disease relapse.ConclusionsCombining TGF-β biomarkers provides prognostic information for patients with stage I–III breast cancer. This can identify patients at increased risk for disease recurrence that might therefore be candidates for additional treatment.     

Smad4 inactivation promotes malignancy and drug resistance of colon cancer

SMAD4 is localized to chromosome 18q21, a frequent site for loss of heterozygosity in advanced stage colon cancers. Although Smad4 is regarded as a signaling mediator of the TGFβ signaling pathway, its role as a major suppressor of colorectal cancer progression and the molecular events underlying this phenomenon remain elusive. Here, we describe the establishment and use of colon cancer cell line model systems to dissect the functional roles of TGFβ and Smad4 inactivation in the manifestation of a malignant phenotype. We found that loss of function of Smad4 and retention of intact TGFβ receptors could synergistically increase the levels of VEGF, a major proangiogenic factor. Pharmacologic inhibition studies suggest that overactivation of the TGFβ-induced MEK-Erk and p38-MAPK (mitogen-activated protein kinase) auxiliary pathways are involved in the induction of VEGF expression in SMAD4 null cells. Overall, SMAD4 deficiency was responsible for the enhanced migration of colon cancer cells with a corresponding increase in matrix metalloprotease 9 enhanced hypoxia-induced GLUT1 expression, increased aerobic glycolysis, and resistance to 5'-fluoruracil-mediated apoptosis. Interestingly, Smad4 specifically interacts with hypoxia-inducible factor (HIF) 1α under hypoxic conditions providing a molecular basis for the differential regulation of target genes to suppress a malignant phenotype. In summary, our results define a molecular mechanism that explains how loss of the tumor suppressor Smad4 promotes colorectal cancer progression. These findings are also consistent with targeting TGFβ-induced auxiliary pathways, such as MEK-ERK, and p38-MAPK and the glycolytic cascade, in SMAD4-deficient tumors as attractive strategies for therapeutic intervention.     

Loss of RUNX3 expression by histone deacetylation is associated with biliary tract carcinogenesis

RUNX3 is a candidate tumor suppressor gene localized in 1p36, a region frequently inactivated through hypermethylation, histone modulation, and other processes in various human tumors. In this study, to elucidate a causal link between RUNX3 expression and biliary tract cancer, we investigated 17 human biliary cancer specimens. In addition, to examine roles of RUNX3 in biliary tract cancer, we restored silenced RUNX3 in the human biliary cancer cell line Mz-ChA-2 using a histone deacetylase inhibitor. Thirteen of 17 human cancer specimens exhibited suppressed RUNX3 expression compared with normal biliary ducts. Moreover, the decreased RUNX3 expression was related to a lower accumulation of acetylated histone H3 associated with RUNX3. In in vitro experiments, vorinostat, a member of a new class of highly potent histone deacetylase inhibitors, restored RUNX3 expression in Mz-ChA-2 cells. Furthermore, vorinostat-induced RUNX3 significantly enhanced p21 expression and growth inhibition of Mz-ChA-2 cells through restoration of TGF-β signaling. These data suggest the significance of histone deacetylation-associated suppression of RUNX3 expression in biliary tract carcinogenesis. Furthermore, vorinostat might hold promise for treating biliary tract cancer through enhancement of TGF-β signaling by restoration of RUNX3.     

Lack of transforming growth factor-β signaling promotes collective cancer cell invasion through tumor-stromal crosstalk

ABSTRACT: INTRODUCTION: Transforming growth factor beta (TGF-β) has a dual role during tumor progression, initially as a suppressor and then as a promoter. Epithelial TGF-β signaling regulates fibroblast recruitment and activation. Concurrently, TGF-β signaling in stromal fibroblasts suppresses tumorigenesis in adjacent epithelia, while its ablation potentiates tumor formation. Much is known about the contribution of TGF-β signaling to tumorigenesis, yet the role of TGF-β in epithelial-stromal migration during tumor progression is poorly understood. We hypothesize that TGF-β is a critical regulator of tumor-stromal interactions that promote mammary tumor cell migration and invasion. METHODS: Fluorescently labeled murine mammary carcinoma cells, isolated from either MMTV-PyVmT transforming growth factor-beta receptor II knockout (TβRII KO) or TβRIIfl/fl control mice, were combined with mammary fibroblasts and xenografted onto the chicken embryo chorioallantoic membrane. These combinatorial xenografts were used as a model to study epithelial-stromal crosstalk. Intravital imaging of migration was monitored ex ovo, and metastasis was investigated in ovo. Epithelial RNA from in ovo tumors was isolated by laser capture microdissection and analyzed to identify gene expression changes in response to TGF-β signaling loss. RESULTS: Intravital microscopy of xenografts revealed that mammary fibroblasts promoted two migratory phenotypes dependent on epithelial TGF-β signaling: single cell/strand migration or collective migration. At epithelial-stromal boundaries, single cell/strand migration of TβRIIfl/fl carcinoma cells was characterized by expression of α-smooth muscle actin and vimentin, while collective migration of TβRII KO carcinoma cells was identified by E-cadherin+/p120+/β-catenin+ clusters. TβRII KO tumors also exhibited a twofold greater metastasis than TβRIIfl/fl tumors, attributed to enhanced extravasation ability. In TβRII KO tumor epithelium compared with TβRIIfl/fl epithelium, Igfbp4 and Tspan13 expression was upregulated while Col1α2, Bmp7, Gng11, Vcan, Tmeff1, and Dsc2 expression was downregulated. Immunoblotting and quantitative PCR analyses on cultured cells validated these targets and correlated Tmeff1 expression with disease progression of TGF-β-insensitive mammary cancer. CONCLUSION: Fibroblast-stimulated carcinoma cells utilize TGF-β signaling to drive single cell/strand migration but migrate collectively in the absence of TGF-β signaling. These migration patterns involve the signaling regulation of several epithelial-to-mesenchymal transition pathways. Our findings concerning TGF-β signaling in epithelial-stromal interactions are important in identifying migratory mechanisms that can be targeted as recourse for breast cancer treatment.     

TGF-β信号通路对胶质瘤干／祖细胞的生物学效应

转化生长因子-β（transforminggrowthfactor-β,TGF-β）作为一种多功能生长因子,具有抑制神经干细胞增殖以及诱导其分化的功能。然而,TGF-β在肿瘤形成过程中具有双重性,在肿瘤形成初期TGF-β可作为抑癌因子抑制细胞增殖．促进细胞分化或凋亡：而在肿瘤发展期,TGF-β却通过促进肿瘤增殖、刺激血管增生和抑制免疫反应而成为促癌因子。目前TGF-β由抑癌因子转变成促癌因子的分子机制尚不清楚。研究发现,TGF-β信号通路在高级别胶质瘤中高度激活表达,并且TGF-β活性高的胶质瘤患者的临床预后极差。胶质瘤干／祖细胞作为胶质瘤发生发展的起源．是胶质瘤治疗成败的关键。因此,研究TGF-β信号通路在胶质瘤干／祖细胞中的生物学效应显得至关重要。本文就TGF-β信号通路在肿瘤干细胞和胶质瘤干／祖细胞的增殖、分化、血管生成、转移等方面的作用作一综述．     

转化生长因子β信号转导途径与胃癌发生发展的关系

 目的 探讨转化生长因子β（TGF-β）信号转导途径与胃癌发生、发展的关系。方法 应用免疫组织化学方法，检测26例正常胃黏膜、22例肠上皮化生、20例不典型增生及43例胃癌中TGF-β受体（RⅠ、RⅡ）和Smad 4蛋白的表达。结果 TGF-β RⅠ、TGF-βRⅡ和Smad 4表达的阳性率随着胃组织病变程度的进展而降低（P＜0.01）。TGF-β RⅠ在胃癌组织中的阳性表达与胃癌组织分化程度、浸润深度及有无淋巴结转移无关。胃癌组织TGF-βRⅡ和Smad4的阳性表达率随浸润深度的加深而降低，差异均有统计学意义（P＜0.01，P＜0.05）；在淋巴结转移阳性患者TGF-βRⅡ、Smad4表达阳性率显著低于无淋巴结转移者，差异有统计学意义（P＜0.05）；TGF-βRⅡ和Smad4在中、高分化组中的阳性表达率明显高于低分化组（P＜0.05）。结论 TGF-β信号转导途径与胃癌发生、发展密切相关，其受体表达的缺失可能是肿瘤细胞逃逸TGF-β负调控的机制之一。     

Tumor-Derived Transforming Growth Factor-β is Critical for Tumor Progression and Evasion from Immune Surveillance

Tumors have evolved numerous mechanisms by which they can escape from immune surveillance. One of these is to produce immunosuppressive cytokines. Transforming growth factor-β(TGF-β) is a pleiotropic cytokine with a crucial function in mediating immune suppression, especially in the tumor  microenvironment. TGF-β produced by T cells has been demonstrated as an important factor for suppressing antitumor immune responses, but the role of tumor-derived TGF-β in this process is poorly understood. In this study, we demonstrated that knockdown of tumor-derived TGF-β using shRNA resulted in dramatically reduced tumor size, slowing tumor formation, prolonging survival rate of tumor-bearing mice and inhibiting metastasis. We revealed possible underlying mechanisms as reducing the number of myeloid-derived suppressor cells (MDSC) and CD4+Foxp3+ Treg cells, and consequently enhanced IFN-γ production by CTLs. Knockdown of tumor-derived TGF-β also significantly reduced the conversion of naïve CD4+ T cells into Treg cells in vitro. Finally, we found that knockdown of TGF-β suppressed cell migration, but did not change the proliferation and apoptosis of tumor cells in vitro. In summary, our study provided evidence that tumor-derived TGF-β is a critical factor for tumor progression and evasion of immune surveillance, and blocking tumor-derived TGF-β may serve as a potential therapeutic approach for cancer.