Expression of RUNX3 and β-catenin in the carcinogenesis of sporadic colorectal tubular adenoma

RUNX Proteins as Epigenetic Modulators in Cancer

RUNX proteins are highly conserved in metazoans and perform critical functions during development. Dysregulation of RUNX proteins through various molecular mechanisms facilitates the development and progression of various cancers, where different RUNX proteins show tumor type-specific functions and regulate different aspects of tumorigenesis by cross-talking with different signaling pathways such as Wnt, TGF-β, and Hippo. Molecularly, they could serve as transcription factors (TFs) to activate their direct target genes or interact with many other TFs to modulate chromatin architecture globally. Here, we review the current knowledge on the functions and regulations of RUNX proteins in different cancer types and highlight their potential role as epigenetic modulators in cancer.

Regulatory effect between HMGA2 and the Wnt/β-catenin signaling pathway in the carcinogenesis of sporadic colorectal tubular adenoma

Due to the high incidence of colorectal cancer worldwide, the underlying molecular mechanisms have been extensively investigated. The Wnt/β-catenin signaling pathway plays a key role in the carcinogenesis of colorectal adenoma. In addition, the high mobility group AT-hook 2 (HMGA2) protein, which is involved in several biological processes, such as proliferation, differentiation, transformation and metastasis, is expressed at significantly high levels in colorectal cancer tissues compared with adjacent normal tissues. Currently, the role of HMGA2 in the carcinogenesis of sporadic colorectal tubular adenoma remains unclear. The downstream Wnt/β-catenin signaling molecule, T-cell factor/lymphoid enhancing factor (TCF/LEF), shares a similar domain with HMGA2, which enhances β-catenin transcriptional activity and TCF/LEF binding. Thus, the present study investigated the association between HMGA2 and the Wnt/β-catenin signaling pathway, and their role in the carcinogenesis of sporadic colorectal tubular adenoma via immunohistochemistry, siRNA, quantitative PCR and western blot analyses. The results demonstrated that the positive rate of HMGA2 expression gradually increased during tumor progression. Furthermore, HMGA2 expression was positively correlated with Wnt/β-catenin signaling protein expression [Wnt, β-catenin, cyclin-dependent kinase 4 (CDK4) and cyclin D1], suggesting its involvement in the carcinogenesis of sporadic colorectal tubular adenoma and its potential to synergistically interact with the Wnt/β-catenin signaling pathway. HMGA2 knockdown in the human colorectal cancer cell line, HCT 116 decreased β-catenin expression and its downstream targets, CDK4 and cyclin D1. Furthermore, silencing of Wnt or β-catenin decreased HMGA2 expression. Taken together, the results of the present study suggest the coordinated regulation of HMGA2 and the Wnt/β-catenin signaling pathway in the carcinogenesis of sporadic colorectal tubular adenoma.

Effects of RUNX3 mediated Notch signaling pathway on biological characteristics of colorectal cancer cells

This study investigated the effects of runt-related transcription factor 3 (RUNX3) mediated Notch pathway on the biological behavior of colorectal cancer (CRC) SW260 cells. CRC tissues and para-carcinoma tissues were collected from 182 CRC patients who had undergone surgical treatment between January 2008 and December 2010. Immunohistochemical staining with streptavidin-peroxidase (SP) was used to detect RUNX3, Notch1 and Jagged 1 expression levels. CRC SW260 cells were divided into the following groups: Control group, si-NC group, si-RUNX3 group, DAPT group, si-RUNX3+DAPT group, and si-NC+DAPT group. Expression levels of RUNX3, and Notch signaling related genes were measured by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) and western blotting in vitro. Besides, MTT, soft agar colony formation, Annexin V-FITC/PI double staining and Transwell were performed to analyze the effects of RUNX3 on cell growth and metastasis. Lower positive expression rate of RUNX3 and higher positive expression rate of Notch1 and Jagged 1 were observed in CRC tissues than those in normal adjacent tissues with a negative correlation, and the expression levels were associated with the differentiation degree, TNM staging, lymph node metastasis and tumor invasion depth (all P<0.05). RUNX3 expression was reduced in si-RUNX3 and si-RUNX3+DAPT group but the expression levels of Notch signaling related genes were markedly increased in si-RUNX3 group or decreased in DAPT and si-NC+DAPT group, as compared with those in the control group (all P<0.05). In addition, the proliferation, colony formation, migration and invasion abilities of SW260 cells were enhanced in si-RUNX3 group but were restricted in DAPT and si-NC+DAPT group, which was contrary to cell apoptosis (all P<0.05). RUNX3 contributes to attenuate the proliferation and metastasis of CRC cells, and promotes cell apoptosis through inhibition of Notch signaling pathway.