Mutation analysis of transforming growth factor beta type II receptor, Smad2, Smad3 and Smad4 in esophageal squamous cell carcinoma

LncRNA MTX2-6 Suppresses Cell Proliferation by Acting as ceRNA of miR-574-5p to Accumulate SMAD4 in Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) has been one of the key causes of cancer deaths worldwide. It has been found that long non-coding RNA (lncRNA) is related to the generation and progression of various cancers (including ESCC). However, there are still many lncRNAs related to ESCC whose functions and molecular mechanisms have not been clearly elucidated. In this study, we first reported that lncRNA MTX2-6 was significantly downregulated in ESCC tissues and cell lines. The decreased expression of MTX2-6 is closely related to larger tumor and worse prognosis of ESCC patients. Through a series of functional experiments, we detected that overexpressed MTX2-6 inhibited cell proliferation and promoted cell apoptosis of ESCC in vitro and in vivo. Further studies showed that MTX2-6 exerts as a competing endogenous RNA (ceRNA) by binding miR-574-5p and elevates the expression of SMAD4 in ESCC. In summary, our results clarify the tumor suppressor roles of MTX2-6/miR-574-5p/SMAD4 axis in the progression of ESCC and provide emerging therapeutic targets for ESCC patients.

The Activation Status of the TGF-β Transducer Smad2 Is Associated with a Reduced Survival in Gastrointestinal Cancers: A Systematic Review and Meta-Analysis

Aberrant function of Smad2, a crucial member of transforming growth factor beta (TGF-β) signaling, is associated with the development of malignancies, particularly in the gastrointestinal district. However, little is known about its possible prognostic role in such tumor types. With the first meta-analysis on this topic, we demonstrated that the lack of the activated form of Smad2 (phosphor-Smad2 or pSmad2), which was meant to be the C-terminally phosphorylated form, showed a statistically significant association with an increased risk of all-cause mortality in patients with gastrointestinal cancers (RR, 1.58; 95% CI, 1.05–2.37, p = 0.029, I² = 84%), also after having adjusted for potential confounders (RR, 1.65; 95% CI, 1.24–2.18; p < 0.001; I² = 4%). This finding highlights the importance of the TGF-β signaling in this type of cancer. In this line, further studies are needed to explore more in depth this important molecular pathway, focusing also on potential therapeutic strategies based on its effectors or molecular targets.

Expression of Smad4, TGF-βRII, and p21waf1 in esophageal squamous cell carcinoma tissue

Esophageal squamous cell carcinoma (SCC) possesses one of the worst prognoses out of the digestive carcinomas. Several studies have suggested that transforming growth factor β receptor type II (TGF-βRII), Smad family member 4 (Smad4) and p21 wild-type p53-activated factor 1 (p21^waf1) are associated with esophageal SCC. The aim of the present study was to evaluate the effect of Smad4, TGF-βRII and p21^waf1 in esophageal squamous cancer tissue and the pathological significance of the effect. An immunohistochemical method was used to evaluate the expression levels of Smad4, TGF-βRII and p21^waf1 in specimens of esophageal SCC lesions obtained from 80 patients. It was found that the expression of Smad4, TGF-βRII and p21^waf1 in histologically-classified grade I esophageal SCC, without invasion or lymph node metastasis, was markedly higher compared with grade III esophageal SCC that had invaded into the deep muscular or serous layer and metastasized to the lymph nodes (P<0.05). Analysis of the expression level of Smad4, TGF-βRII and p21^waf1, as well as the clinical and pathological characteristics of esophageal SCC, revealed that the three proteins may be associated with the carcinogenesis, biological behavior and prognosis of esophageal SCC, parallel to the pathological stage and cell grade.

The combination of SMAD4 expression and histological grade of dysplasia is a better predictor for the malignant transformation of oral leukoplakia

Oral leukoplakia (OL) is the most common premalignancy in the oral cavity and can progress to oral squamous cell carcinoma (OSCC). SMAD4 is a tumor suppressor implicated in multiple cancer types including OSCC. To assess the role of SMAD4 in oral leukoplakia malignant transformation, the authors investigated SMAD4 expression patterns in OL and OSCC using a highly specific antibody and correlated the patterns with the risk of malignant transformation oral leukoplakia. Immunohistochemistry and a quantitative imaging system were used to measure SMAD4 expression in OL from 88 OL patients, including 22 who later went through malignant transformation, and their OSCC counterpart. Forty-three (48.9%) of the 88 OL patients had strong SMAD4 expression. SMAD4 expression had no significant correlation with patients' clinicopathological parameters. Interestingly, 17 (39.5%) of the 43 OL lesions with strong SMAD4 expression went through malignant transformation whereas only 5 (11.1%) of the 45 OL lesions with weak SMAD4 expression did so (p = 0.002). The SMAD4 expression in OL was much higher than that in their OSCC counterpart. Kaplan-Meier analysis revealed that the combination of SMAD4 expression and histological grade of dysplasia (p = 0.007) is a better predictor for the malignant transformation of oral leukoplakia. In the multivariate analysis, both SMAD4 expression and grade of dysplasia were identified as independent factors for OL malignant transformation risk (p = 0.013 and 0.021, respectively). It was concluded that high SMAD4 expression may be indicative of an early carcinogenic process in OL and serve as an independent biomarker in assessing malignant transformation risk in patients with OL, and the combination of SMAD4 expression and histological grade of dysplasia is a better predictor for the malignant transformation of oral leukoplakia.

Two sides of the story? Smad4 loss in pancreatic cancer versus head-and-neck cancer

TGFβ signaling Smads (Smad2, 3, and 4) were suspected tumor suppressors soon after their discovery. Nearly two decades of research confirmed this role and revealed other divergent and cancer-specific functions including paradoxical tumor promotion effects. Although Smad4 is the most potent tumor suppressor, its functions are highly context-specific as exemplified by pancreatic cancer and head-and-neck cancer: in pancreatic cancer, Smad4 loss cannot initiate tumor formation but promotes metastases while in head-and-neck cancer Smad4 loss promotes cancer progression but also initiates tumor formation, likely through effects on genomic instability. The differing consequences of impaired Smad signaling in human cancers and the molecular mechanisms that underpin these differences will have important implications for the design and application of novel targeted therapies.

Disruption of transforming growth factor beta-Smad signaling pathway in head and neck squamous cell carcinoma as evidenced by mutations of SMAD2 and SMAD4

The role of the TGF-beta-Smad signaling pathway in the carcinogenesis of head and neck cancer has not been fully evaluated genetically. In this study, we screened for mutation in the five main members of the TGF-beta -Smad signaling pathway, TGF-beta type I receptor (TGFBRI), TGF-beta type II receptor (TGFBRII), SMAD2, SMAD3 and SMAD4, in eight human head and neck squamous cell carcinoma (HNSCC) cell lines. Two mutations with presumed loss of heterozygosity (LOH) were identified. A novel missense mutation of SMAD2, located in exon 8 at codon 276 TCG (ser) -->TTG (leu), was identified in cell line SCC-15. This is the first report of a biallelic mutation of the SMAD2 gene in HNSCC. A nonsense mutation of the SMAD4 gene in exon 5 codon 245 CAG (glut) -->TAG (stop) was found in cell line CAL27. Western blotting verified that this nonsense mutation gives rise to the complete loss of the Smad4 protein in the cells. While the down-regulation and loss of expressions of the TGF-beta-Smad signaling pathway have been described frequently in HNSCC, here we offer further genetic evidence that the pathway is directly targeted for mutation during the HNSCC tumorigenesis.

Inability of transforming growth factor-beta to cause SnoN degradation leads to resistance to transforming growth factor-beta-induced growth arrest in esophageal cancer cells

It is well established that loss of a growth inhibitory response to transforming growth factor-beta (TGF-beta) is a common feature of epithelial cancers including esophageal cancer. However, the molecular basis for the abrogation of this key homeostatic mechanism is poorly understood. In esophageal cancer cell lines that are resistant to TGF-beta-induced growth inhibition, TGF-beta also fails to decrease transcription of c-myc despite the presence of functional signaling components. Consequently, to gain a better understanding of the mechanisms leading to resistance to TGF-beta-induced growth arrest, the basis for the inability to decrease c-myc transcription was investigated. Regardless of sensitivity to TGF-beta-induced growth arrest, TGF-beta enhanced the ability of Smad3-protein complexes to bind c-myc regulatory elements. However, in a growth inhibition-resistant esophageal cancer cell line, the Smad3-protein complexes contained the SnoN oncoprotein. Furthermore, in esophageal cancer cell lines that are resistant to TGF-beta-induced growth arrest, TGF-beta does not cause degradation of SnoN. Analyses of the effect of modulating SnoN expression in both growth inhibition-sensitive and growth inhibition-resistant cell lines showed that degradation of SnoN is a prerequisite for both TGF-beta-induced repression of c-myc transcription and growth arrest. The data indicate that SnoN-Smad3 complexes do not cause repression of c-myc transcription but rather prevent functionality of active repressor complexes. Thus, these studies reveal a novel mechanism for resistance to TGF-beta-induced growth inhibition in esophageal cancer, namely the failure to degrade SnoN. In addition, they show that SnoN can block TGF-beta repression of gene transcription.

Plasma level of transforming growth factor beta1 measured from the azygos vein predicts prognosis in patients with esophageal cancer

PURPOSE

Transforming growth factor (TGF)-beta regulates cell growth inhibition. When tumor cells lose their sensitivity to TGF-beta growth inhibition, the excess TGF-beta that results may act on tumor cells to facilitate tumor development. Previously, we have shown that an elevated systemic TGF-beta 1 level is not related to tumor progression in esophageal cancer (Y. Fukai et al., Int J Cancer 2003;104:161-6). We considered that systemic inflammation or chronic disease, in addition to the tumor, may influence the plasma TGF-beta level. Therefore, we examined the hypothesis that the plasma TGF-beta level measured from the azygos vein would independently predict tumor progression and prognosis in patients with esophageal cancer.

EXPERIMENTAL DESIGN

Fifty-seven plasma samples were obtained intraoperatively from the azygos vein in patients with esophageal cancer. ELISA was used to quantify the plasma TGF-beta 1 levels, which were correlated with pathological features and patient survival.

RESULTS

The mean plasma TGF-beta 1 level measured from the azygos vein of esophageal cancer patients was 5.09 +/- 0.48 ng/ml (mean +/- SE). The survival rates of patients with a high TGF-beta 1 level (defined as a level above the 4.6 ng/ml level of normal controls) in the azygos vein were significantly lower than those of patients with a low TGF-beta 1 level (P = 0.0317). Moreover, the TGF-beta 1 level in the azygos vein was an independent prognostic factor for overall survival (P = 0.0474).

CONCLUSIONS

The level of plasma TGF-beta 1 measured from the azygos vein is an independent predictor in patients with esophageal cancer and may reflect tumor progression more specifically because the azygos vein is responsible for venous return from the esophagus.

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