Relationship of transforming growth factor beta 1 to angiogenesis in gastric carcinoma

KLF8 involves in TGF-beta-induced EMT and promotes invasion and migration in gastric cancer cells

PURPOSE

Krüppel-like factor 8 (KLF8), a downstream transcription factor of transforming growth factor-β1 (TGF-β1), has a role in tumorigenesis, tumor progress and epithelial-to-mesenchymal transition (EMT) induction. Recent studies mainly focused on its role in breast cancer and hepatocellular carcinoma; however, little is studied in gastric cancer. Here, we aim to explore whether KLF8 is involved in TGF-β1-induced EMT in gastric cancer cells.

METHODS

Western blot and real-time PCR assays were used to detect the expression of KLF8, E-cadherin and vimentin in gastric cancer cell line SGC7901 treated with or without TGF-β1. The lentivirus-mediated RNA interference technique was used to knock down the expression of KLF8 in gastric cancer cell line SGC7901. In vitro, the ability of cell migration and invasion were measured by transwell and wound healing assays; the cell motility was detected by high content screening assay.

RESULTS

TGF-β1 could induce EMT via down-regulating E-cadherin and up-regulating vimentin expression in gastric cancer cells. Further study found that TGF-β1 could induce KLF8 expression at the protein and mRNA levels in gastric cancer cells (P < 0.05). Western blot and real-time PCR assays found that small interference RNA (siRNA)-mediated KLF8 silence blocked TGF-β1-induced EMT-like transformation and subsequently reversed the loss of E-cadherin and gain of vimentin. In vitro, inhibition of KLF8 decreased TGF-β1-prompted cell migration, invasion and motility.

CONCLUSIONS

KLF8, a transcription factor, is involved in TGF-β1-induced EMT in gastric cancer cells and may be a novel therapeutic target for the treatment of gastric cancer.

Tissue level, activation and cellular localisation of TGF-beta1 and association with survival in gastric cancer patients

Transforming growth factor-β1 (TGF-β1), a tumour suppressing as well as tumour-promoting cytokine, is stored as an extracellular matrix-bound latent complex. We examined TGF-β1 activation and localisation of TGF-β1 activity in gastric cancer. Gastric tumours showed increased stromal and epithelial total TGF-β1 staining by immunohistochemistry. Active TGF-β1 was present in malignant epithelial cells, but most strongly in smooth muscle actin expressing fibroblasts. Normal gastric mucosa from the same patient showed some staining for total, and little for active TGF-β1. Active TGF-β1 levels were determined by ELISA on tissue homogenates, confirming a strong increase in active TGF-β1 in tumours compared to corresponding normal mucosa. Moreover, high tumour TGF-β1 activity levels were significantly associated with clinical parameters, including worse survival of the patients. Total and active TGF-β1 levels were not correlated, suggesting a specific activation process. Of the different proteases tested, active TGF-β1 levels were only correlated with urokinase activity levels. The correlation with urokinase activity suggests a role for plasmin in TGF-β1 activation in the tumour microenvironment, resulting in transformation of resident fibroblasts to tumour promoting myofibroblasts. In conclusion we have shown localisation and clinical relevance of TGF-β1 activity levels in gastric cancer.

Serum levels of transforming growth factor beta1 are significantly correlated with venous invasion in patients with gastric cancer

BACKGROUND AND AIM

The significance of serum levels of transforming growth factor (TGF)-beta1 in the development of gastric cancer is unclear. The purpose of this study is to determine whether serum TGF-beta1 correlated with the clinicopathological findings of patients with gastric cancer.

METHODS

Transforming growth factor-beta1 levels in the serum of 275 gastric cancer patients and 275 gender- and age-matched healthy controls were measured with enzyme-linked immunosorbent assay (ELISA) using a commercially available kit.

RESULTS

The mean level of serum TGF-beta1 of gastric cancer patients (15.9 +/- 5.9 ng/mL) was significantly higher than that (13.9 +/- 7.4 ng/mL) of healthy controls (P < 0.01). The odds ratio for the subjects in the highest quartile (16.7 ng/mL or more) was 4.03 (95% confidence interval, 2.14-7.58), as compared with that for the subjects in the lowest quartile (0-9.5 ng/mL). Patients with venous invasion compared to those without venous invasion had significantly elevated serum TGF-beta1 (17.3 +/- 7.2 vs 15.0 +/- 5.1 ng/mL; P = 0.04). There were no statistically significant differences between the two groups categorized by histological type, lymph node metastasis and distant metastasis. Logistical regression analysis showed that venous invasion was significantly correlated with elevated serum TGF-beta1 levels (P = 0.02).

CONCLUSIONS

The present study showed that an elevated serum TGF-beta1 level may be significantly correlated with venous invasion in gastric cancer patients.

RNAi-mediated gene silencing of transforming growth factor-β1 expression in human gastric cancer cell line SGC-7901 and peritoneal mesothelial cells

AIM: To silence the expression of transforming growth factor-β1 (TGF-β1) gene in human gastric cancer cell line SGC-7901 and peritoneal mesothelial cells using vector based RNA interference (RNAi) technique.

METHODS: A vector, which was used to transcribe functional short interfering RNA (siRNA), was construc-ted, and 62 mer oligonucleotide fragment was inserted into the downstream of the hU6 promoter. Mesothelial cells were isolated from human omenta by trypsin-EDTA disaggregation, and identified by morphology and streptomyces anti-biotin protein-peroxidase meth-od. The plasmids containing TGF-β1 target sequences were transfected into the two kinds of cells menti-oned above, and then the expression level of TGF-β1 was detected by semiquantitive RT-PCR and Western blot technique.

RESULTS: Electrophoresis and DNA sequencing con-firmed that the TGF-β1-specific siRNA was synthesized and cloned into the expression vector pcPUR β iCassette successfully. Immunohistochemistry showed positive staining for cytokeratin and vimentin, but negative staining for leukocyte common antigen and factor VIII-related antigen in cultured mesothelial cells. As compared with their respective untreated group, the TGF-β1 mRNA and protein expression in the two kinds of transfected cells were remarkably decreased, especially TGF-β1 protein. TGF-β1 protein was reduced by a perce-nt of 65.8% and 61.8% in human gastric cancer cell line SGC-7901 and mesothelial cells, respectively.

CONCLUSION: TGF-β1 expression can be notably inh-ibited in human gastric cancer cell line SGC-7901 and peritoneal mesothelial cells using plasmid-based TGF-β1-RNAi technique.

Gene expression of angiogenic factors correlates with metastatic potential of prostate cancer cells

We hypothesize that expression of proangiogenic genes correlates with the metastatic potential of prostate cancer cells. LNCaP, DU-145, and PC-3 are prostate cancer cell lines with low, moderate, and high metastatic potential, respectively, as we demonstrated by their capacity to invade an extracellular matrix, an established tumor invasion assay. The constitutive gene expression of the proangiogenic factors, vascular endothelial growth factor, intercellular adhesion molecule-1, interleukin-8, and transforming growth factor-beta2, was significantly greater in the more metastatic DU-145 and PC-3 cells as compared with LNCaP cells. Matrix metalloproteinase (MMP)-9 is thought to contribute to the invasive phenotype of tumor cells. PC-3 cells showed increased expression of MMP-9 and membrane type 4-MMP as compared with LNCaP and DU-145. Tissue inhibitors of metalloproteinase 1 and 4 gene expression were elevated in DU-145 and PC-3 cells, but paradoxically, LNCaP cells had undetectable levels of these genes. We transfected and overexpressed MMP-9 in poorly metastatic LNCaP cells and measured their invasive activity. Transient expression of human MMP-9 in LNCaP cells produced a 3-5-fold increase in MMP-9 activity with a comparable increase in invasiveness. Antisense ablation of the expression of MMP-9 in DU-145 and PC-3 cells produced concomitant inhibition of the gene expression of the proangiogenic factors, vascular endothelial growth factor, and intercellular adhesion molecule-1 (ICAM-1). Treatment of DU-145 and PC-3 cells with a selective chemical inhibitor of MMP-9 proteinase activity also inhibited their invasive activity. These results support our hypothesis that metastatic potential of prostate cancer cells correlates with expression of proangiogenic factors.

Metastatic melanoma cells escape from immunosurveillance through the novel mechanism of releasing nitric oxide to induce dysfunction of immunocytes

Nitric oxide (NO) is known to facilitate tumour metastasis through the promotion of angiogenesis, vascular dilation, platelet aggregation, etc. In the present study we explored its novel role in producing dysfunction of the host immune system in the metastasis of murine metastatic melanoma B16-BL6 cells. A significant reduction in the mixed lymphocyte reaction (MLR) was observed in the spleen cells from B16-BL6-bearing mice, but not in those from mice bearing the parent cell B16. When B16-BL6 cells were added in vitro to the MLR, a significant decrease was also found, even when they were co-cultured with the lymphocytes in two compartments of a Transwell chamber separated by an 8.0 microm filter. The supernatant from cultured B16-BL6 but not B16 cells, which had a greatly increased NO activity, significantly inhibited concanavalin A- and lipopolysaccharide-induced lymphocyte proliferation. A remarkably higher expression of inducible NO synthase (iNOS) was detected in B16-BL6 cells than in B16 cells. Nomega-Nitro-l-arginine (l-NNA), a NO synthase inhibitor and superoxide dismutase, significantly antagonized the above inhibition by B16-BL6 cells, while l-arginine, a NO precursor, and S-nitroso-N-acetyl-d,l-penicillamine, a NO donor, strengthened the inhibition. Furthermore, l-NNA significantly inhibited lung metastasis of B16-BL6 cells, while l-arginine tended to enhance the metastasis. The cytotoxicity of B16-BL6-specific T-cells was significantly decreased by pre-culture with B16-BL6 cells in a Transwell chamber or the culture supernatants of B16-BL6 cells, whereas l-iminoethyl-lysine, a selective inhibitor of iNOS, showed a significant recovery from the disease. These results suggest that NO released by metastatic tumour cells may impair the immune system, which facilitates the escape from immunosurveillance and metastasis of tumour cells.

Breast masses with peripheral rim enhancement on dynamic contrast-enhanced MR images: correlation of MR findings with histologic features and expression of growth factors

PURPOSE

To investigate the histologic bases of rim enhancement of breast masses demonstrated on dynamic contrast material-enhanced magnetic resonance (MR) images.

MATERIALS AND METHODS

Dynamic MR images of breast lesions (invasive carcinoma, n = 29; other, n = 6) in 35 women were reviewed. In each patient, subtraction images of the dynamic contrast-enhanced study were obtained, and early and delayed rim enhancement and delayed internal enhancement were evaluated. The MR findings were correlated with the ratio of microvessel density of the peripheral to the central portion of the lesion, fibrosis, and other histologic features, including expression of vascular endothelial growth factor (VEGF) and transforming growth factor ss1.

RESULTS

Early rim enhancement was observed in 29% and delayed rim enhancement was noted in 60% of all patients. Small cancer nests, a high ratio of peripheral-to-central microvessel density, peripheral VEGF expression, and a low ratio of peripheral-to-central fibrosis were correlated with early rim enhancement. Delayed rim enhancement was correlated with a high degree of fibrosis and inflammatory changes. Delayed internal enhancement was correlated with a high degree of fibrosis.

CONCLUSION

Rim enhancement of breast lesions at MR imaging is due to a combination of angiogenesis, distribution and degree of fibrosis, expression pattern of VEGF, and various histologic features.

TGF-beta and cancer

The relationships between transforming growth factor-beta (TGF-beta) and cancer are varied and complex. The paradigm that is emerging from the experimental evidence accumulated over the past decade or so is that TGF-beta can play two different and opposite roles with respect to the process of malignant progression. During early stages of carcinogenesis, TGF-beta acts predominantly as a potent tumor suppressor and may mediate the actions of chemopreventive agents such as retinoids and nonsteroidal anti-estrogens. However, at some point during the development and progression of malignant neoplasms, bioactive TGF-betas make their appearance in the tumor microenvironment and the tumor cells escape from TGF-beta-dependent growth arrest. In many cases, this resistance to TGF-beta is the consequence of loss or mutational inactivation of the genes that encode signaling intermediates. These include the types I and II TGF-beta receptors, as well as receptor-associated and common-mediator Smads. The stage of tumor development or progression at which TGF-beta-resistant clones come to dominate the tumor cell population in different types of neoplasm remains to be defined. The phenotypic switch from TGF-beta-sensitivity to TGF-beta-resistance that occurs during carcinogenesis has several important implications for cancer prevention and treatment.