CST2 is activated by RUNX1 and promotes pancreatic cancer progression by activating PI3K/AKT pathway

Cystatin 2 (CST2) is a protein coding gene that belongs to a large superfamily of cysteine protease inhibitors. The deregulation of CST2 has been implicated in human cancers. The role of CST2 in pancreatic carcinogenesis has not yet been investigated. In this study, Gene Expression Profiling Interactive Analysis was performed using the Cancer Genome Atlas (TCGA) dataset containing pancreatic tumor samples and normal tissues. The functional role of CST2 in pancreatic cells was investigated by gene knockdown in vitro and in mouse xenograft tumor model. We found that CST2 was overexpressed in pancreatic tumor samples and cell lines. The knockdown of CST2 led to reduced proliferation, migration, and invasion, while apoptotic events were increased upon CST2 silencing in pancreatic cancer cells. In the xenograft mouse model of pancreatic cells, CST2 knockdown also retarded tumor growth on tumor growth. RUNX1 was identified as a transcription factor which positively regulated the expression of CST2. Further, we showed that, CST2 knockdown suppressed the activation of the PI3K/AKT signaling in pancreatic cells. Overall, our findings suggest that CST2 serves as an oncogene which facilitates the progression of pancreatic cancer. RUNX1 functions to upregulate CST2 in pancreatic cancer cells and CST2 may promote the malignancy of pancreatic cells by maintaining the activation of PI3K/AKT signaling.

Identification of Cysteine Protease Inhibitor CST2 as a Potential Biomarker for Colorectal Cancer

Additional biomarkers for the development and progression of colorectal cancer (CRC) remain to be identified. Hence, the current study aimed to identify potential diagnostic markers for CRC. Analyses of cysteine protease inhibitor [cystatins (CSTs)] expression in CRC samples and its correlation with cancer stage or survival in patients with CRC demonstrated that CRC tissues had greater CST1 and CST2 mRNA expression compared to noncancerous adjacent tissues, while higher CST2 mRNA expression in CRC tissues was correlated with advanced stages and disease-free survival in patients with CRC, encouraging further exploration on the role of CST2 in CRC. Through an online database search and tissue microarray (TMA), we confirmed that CRC samples had higher CST2 expression compared to noncancerous adjacent tissue or normal colorectal tissues at both the mRNA and protein levels. TMA also revealed that colorectal adenoma, CRC, and metastatic CRC tissues exhibited a significantly increased CST2 protein expression. Accordingly, survival analysis demonstrated that the increase in CST2 protein expression was correlated with shorter overall survival of patients with CRC. Moreover, our results found a significant upregulation of CST2 in multiple cancer tissues. Taken together, these findings suggest the potential role of CST2 as a diagnostic and prognostic biomarker for CRC.

Cystatin 2 leads to a worse prognosis in patients with gastric cancer

Despite the amazing progress in the treatment of gastric cancer (GC), it is still the third leading cause of cancer death in the world. This study explored the key genes that are related to the prognosis and pathogenesis of GC. Data from the cancer genome atlas (TCGA) and Oncomine were applied to evaluate the expression of cystatin 2 (CST2) in GC samples. Kaplan-Meier plotter was carried out to detect the overall survival of GC patients with different expression levels of CST2. Gene Set Enrichment Analysis (GSEA) was carried out to investigate the functions and pathways connected with CST2 expression. Quantitative real-time polymerase chain reaction (qPCR) and Western blot assays were used to assess CST2 expression. The biological properties of GC cells were assessed with the support of cell proliferation and Transwell assays. Important proteins involved in the regulation of CST2 in GC cell behaviors were evaluated by Western blot. Through analysis of the database, we found that CST2 expression was significantly upregulated in GC samples and actively related to GC patients' poor outcomes. Importantly, the analysis of GSEA showed that GST2 expression was closely connected with the proliferation and migration of cells, as well as the TGF-β1 signaling pathway. In addition, biological assays illustrated that over-expression of CST2 strengthened the activity and metastasis of GC cells. After the upregulation of CST2, the expression of cyclin D1, N-cadherin, vimentin, TGF-β1, and Smad4 increased, and E-cadherin expression decreased. Our findings revealed that over-expression of CST2 enhanced the growth, migration, and invasion of GC cells through modulating the epithelial-mesenchymal transition (EMT) and TGF-β1 signaling pathway, affording a possible biomarker for the treatment of GC.