Cystatins in cancer progression: More than just cathepsin inhibitors

Cystatins are endogenous and reversible inhibitors of cysteine peptidases that are important players in cancer progression. Besides their primary role as regulators of cysteine peptidase activity, cystatins are involved in cancer development and progression through proteolysis-independent mechanisms. Mechanistic studies of cystatin function revealed that they affect all stages of cancer progression including tumor growth, apoptosis, invasion, metastasis and angiogenesis. Recently, the involvement of cystatins in the antitumor immune responses was reported. In this review, we discuss molecular mechanisms and clinical aspects of cystatins in cancer. Altered expression of cystatins in cancer resulting in harmful excessive cysteine peptidase activity has been a subject of several studies in order to find correlations with clinical outcome and therapy response. However, involvement in anti-tumor immune response and signaling cascades leading to cancer progression designates cystatins as possible targets for development of new anti-tumor drugs.

Cysteine cathepsins as a prospective target for anticancer therapies-current progress and prospects

Cysteine cathepsins (CTS), being involved in both physiological and pathological processes, play an important role in the human body. During the last 30 years, it has been shown that CTS are highly upregulated in a wide variety of cancer types although they have received a little attention as a potential therapeutic target as compared to serine or metalloproteinases. Studies on the increasing problem of neoplastic progression have revealed that secretion of cell-surface- and intracellular cysteine proteases is aberrant in tumor cells and has an impact on their growth, invasion, and metastasis by taking part in tumor angiogenesis, in apoptosis, and in events of inflammatory and immune responses. Considering the role of CTS in carcinogenesis, inhibition of these enzymes becomes an attractive strategy for cancer therapy. The downregulation of natural CTS inhibitors (CTSsis), such as cystatins, observed in various types of cancer, supports this claim. The intention of this review is to highlight the relationship of CTS with cancer and to present illustrations that explain how some of their inhibitors affect processes related to neoplastic progression.

MMP-9 is increased in the pathogenesis of gastric cancer by the mediation of HER2

Human epidermal growth factor receptor 2 (HER2) overexpression is not only closely associated with the tumor growth, but is also related to tumor invasion. We here aimed to investigate the mechanism of HER2 mediation in the pathogenesis of gastric cancer. The human gastric cancer cell lines SGC-7901, MKN-45, AGS, the immortalized cell line GES-1 derived from normal gastric mucosa. Cell transfection and selection of stable cell lines and the gene and protein levels of HER2 and Matrix metalloproteinase-9 (MMP-9) were examined to determine the molecular relationship between them in the pathogenesis of gastric cancer. The human gastric cancer cell lines SGC-7901, MKN-45, AGS, the immortalized cell line GES-1 derived from normal gastric mucosa. Cell transfection and selection of stable cell lines and the gene and protein levels of HER2 and MMP-9 were examined to determine the molecular relationship between them in the pathogenesis of gastric cancer. We demonstrated that vector-based shRNA significantly knocked down the expression of HER2 and considerably inhibited both the migration and invasion of gastric cancer cells. HER2 knockdown resulted in the downregulation of the expression of MMP-9, whereas HER2 overexpression improved the transcription of MMP-9 through the activation of an MMP-9 promoter. The promoter region of MMP-9 between -2500 and -2000 bp was found to be crucial for the upregulation of HER2-mediated transcription. Furthermore, a truncated promoter (-70 to +63) did not display any transcriptional activity. Cell invasion activity was almost completely inhibited when MMP-9 was knocked down. Conversely, the overexpression of MMP-9 partly rescued the invasion ability of cell strains with knockdown HER2. These findings help further understanding of the molecular mechanisms through which HER2 promotes malignancy, and suggest that targeting both HER2 and MMP-9 may be required to effectively block HER2 signaling in gastric cancer therapy.

HER-2-induced PI3K signaling pathway was involved in the pathogenesis of gastric cancer

Human epidermal growth factor receptor-2 (HER-2) overexpression was closely associated with the tumor growth and invasion, we here aimed to investigate the mechanism of HER-2 mediation in the pathogenesis of gastric cancer (GC). We first detected the expression of HER-2 in GC cell line SGC-7901 and then examined the levels of nuclear factor-κB (NF-κB), matrix metalloproteinase-9 (MMP-9) and intercellular adhesion molecule-1 (ICAM-1) and the association between them by molecular methods. Statistical analysis was used to compare the significance. We further detected the possible molecular mechanism involved in their relationship in the SGC-7901 genesis. The MMP-9, NF-κB and secretory type (s-ICAM-1) levels were significantly greater in peripheral blood serum from SGC-7901 than healthy control GES-1 (P<0.01). ICAM-1, MMP-9 and NF-κB mRNA and protein levels were more highly expressed in SGC-7901 than healthy control GES-1. The expression levels of NF-κB, MMP-9 and ICAM-1 were positively related in GC cell line SGC-7901, which was HER-2 positive. The HER-2 positive SGC-7901 secreted more transforming growth factor beta 1 (TGF-β1) and resultantly activated MMP-9 to enhance s-ICAM-1 secretion and further studies showed that phosphatidylinositol-3 kinase (PI3K)/Akt/NF-κB signaling pathway was involved in GC pathogenesis. The GC cells that express the HER-2 oncogene spur the activation of NF-κB that can upregulate the expression of ICAM-1 and induce the expression of MMP-9, which hydrolyzes ICAM-1 into s-ICAM-1 to promote tumor immune escape. TGF-β1-induced PI3K/Akt/NF-κB signaling pathway was involved in the pathogenesis of GC and they could be a new target for cancer therapy. The GC cells that express the HER-2 oncogene spur the activation of NF-κB that can upregulate the expression of ICAM-1 and induce the expression of MMP-9, which hydrolyzes ICAM-1 into s-ICAM-1 to promote tumor immune escape. TGF-β1-induced PI3K/Akt/NF-κB signaling pathway was involved in the pathogenesis of GC and they could be a new target for cancer therapy.

High expression of integrin-linked kinase predicts aggressiveness and poor prognosis in patients with gastric cancer

Integrin-linked kinase (ILK), an intracellular serine/threonine protein kinase, has been reported to be highly expressed in many human malignancies, including gastric cancer. However, the prognostic significance of ILK expression in gastric cancer remains to be elucidated. In the present study, ILK expression in 95 gastric tumor tissues and 30 adjacent non-cancerous gastric mucosa was evaluated by immunohistochemistry and correlated with clinicopathological characteristics and patients' outcome. The results showed that high ILK expression was observed in 47.4% (45/95) of gastric cancer tissues, but only in 20.0% (6/30) of adjacent gastric mucosa. Clinicopathological analysis indicated that high ILK expression was significantly associated with poor tumor differentiation (P=0.024), advanced TNM stage (P=0.006), tumor invasion (P=0.001), and lymph node metastasis (P=0.014). Kaplan-Meier survival curves demonstrated that patients with high ILK expression had substantially shorter overall survival that those with low ILK expression (P=0.043, log-rank test). Furthermore, Cox multivariate regression analysis identified ILK expression as an independent prognostic factor for overall survival of gastric cancer patients (hazard ratio, 1.95; 95% confidence interval, 1.02-3.13; P=0.026). In conclusion, our data suggest that ILK may contribute to the malignant progression of gastric cancer and serve as a novel prognostic indicator for gastric cancer patients.