TGIF function in oncogenic Wnt signaling

Roles of oncogenes in esophageal squamous cell carcinoma and their therapeutic potentials

Esophageal squamous cell carcinoma (ESCC) is the most common type of esophageal cancer (EC) in Asia. It is a malignant digestive tract tumor with abundant gene mutations. Due to the lack of specific diagnostic markers and early cancer screening markers, most patients are diagnosed at an advanced stage. Genetic and epigenetic changes are closely related to the occurrence and development of ESCC. Here, We review the activation of proto-oncogenes into oncogenes through gene mutation and gene amplification in ESCC from a genetic and epigenetic genome perspective, We also discuss the specific regulatory mechanisms through which these oncogenes mainly affect the biological function and occurrence and development of ESCC through specific regulatory mechanisms. In addition, we summarize the clinical application value of these oncogenes is summarized, and it provides a feasible direction for clinical use as potential therapeutic and diagnostic markers.

TGIF1 plays a carcinogenic role in esophageal squamous cell carcinoma through the Wnt/β‑catenin and Akt/mTOR signaling pathways

TGFB induced factor homeobox 1 (TGIF1), a transcriptional corepressor, has been reported to be involved in tumorigenesis and cancer development. However, the role of TGIF1 in the growth and metastasis of esophageal cancer is poorly studied. In the present study, it was found that TGIF1 was highly expressed in esophageal cancer tissues and cell lines. The silencing of TGIF1 by siRNA interference significantly inhibited the proliferation, migration, invasion and epithelial‑mesenchymal transition (EMT) process of KYSE‑150 esophageal cancer cells, and promoted cell apoptosis. Correspondingly, the upregulation of TGIF1 significantly promoted the proliferation and metastatic potential of Eca‑109 cells, and reduced apoptosis. Furthermore, the data indicated that the Wnt/β‑catenin and Akt/mammalian target of rapamycin (mTOR) signaling pathways were inhibited by TGIF1 knockdown, and were promoted by the overexpression of TGIF1. It was also confirmed that TGIF1 knockdown reduced tumor growth, inhibited Wnt/β‑catenin and Akt/mTOR pathway activation, and reversed the TGF‑β1‑mediated EMT process in a tumor xenograft model. Taken together, the data of the present study suggest that TGIF1 plays an oncogenic role in the progression of esophageal cancer. It may carry out this role by regulating the Wnt/β‑catenin and Akt/mTOR signaling pathways.

Use of signals of positive and negative selection to distinguish cancer genes and passenger genes

A major goal of cancer genomics is to identify all genes that play critical roles in carcinogenesis. Most approaches focused on genes positively selected for mutations that drive carcinogenesis and neglected the role of negative selection. Some studies have actually concluded that negative selection has no role in cancer evolution. We have re-examined the role of negative selection in tumor evolution through the analysis of the patterns of somatic mutations affecting the coding sequences of human genes. Our analyses have confirmed that tumor suppressor genes are positively selected for inactivating mutations, oncogenes, however, were found to display signals of both negative selection for inactivating mutations and positive selection for activating mutations. Significantly, we have identified numerous human genes that show signs of strong negative selection during tumor evolution, suggesting that their functional integrity is essential for the growth and survival of tumor cells.

Genetic Mechanisms of Immune Evasion in Colorectal Cancer

To understand the genetic drivers of immune recognition and evasion in colorectal cancer, we analyzed 1,211 colorectal cancer primary tumor samples, including 179 classified as microsatellite instability-high (MSI-high). This set includes The Cancer Genome Atlas colorectal cancer cohort of 592 samples, completed and analyzed here. MSI-high, a hypermutated, immunogenic subtype of colorectal cancer, had a high rate of significantly mutated genes in important immune-modulating pathways and in the antigen presentation machinery, including biallelic losses of B2M and HLA genes due to copy-number alterations and copy-neutral loss of heterozygosity. WNT/β-catenin signaling genes were significantly mutated in all colorectal cancer subtypes, and activated WNT/β-catenin signaling was correlated with the absence of T-cell infiltration. This large-scale genomic analysis of colorectal cancer demonstrates that MSI-high cases frequently undergo an immunoediting process that provides them with genetic events allowing immune escape despite high mutational load and frequent lymphocytic infiltration and, furthermore, that colorectal cancer tumors have genetic and methylation events associated with activated WNT signaling and T-cell exclusion.Significance: This multi-omic analysis of 1,211 colorectal cancer primary tumors reveals that it should be possible to better monitor resistance in the 15% of cases that respond to immune blockade therapy and also to use WNT signaling inhibitors to reverse immune exclusion in the 85% of cases that currently do not. Cancer Discov; 8(6); 730-49. ©2018 AACR.This article is highlighted in the In This Issue feature, p. 663.

Silencing of TGIF sensitizes MDA-MB-231 human breast cancer cells to cisplatin-induced apoptosis

The present study was designed to explore the sensitivity of MDA-MB-231 cells to cisplatin after silencing the expression of TG-interacting factor (TGIF) protein. Cell viability was measured using an MTT assay. Cell apoptosis was detected by the annexin V and dead cell assay and the Hoechst staining assay. Protein expression was analyzed using western blot analysis. A colony formation assay was also performed. It was observed that cisplatin reduced the expression of TGIF protein in a dose- and time-dependent manner. Silencing TGIF significantly suppressed the cell proliferation and colony formation in MDA-MB-231 cells with the treatment of cisplatin. Results indicated that silencing TGIF could dramatically increase the cisplatin-induced apoptosis rate in MDA-MB-231 cells. The expression of PARP and caspase-3 proteins was correlated with the effect that silencing TGIF enhanced cisplatin sensitivity in MDA-MB-231 cells. The present data showed that silencing TGIF promoted apoptotic sensitivity that was induced by cisplatin in MDA-MB-231 human breast cancer cells and suggested that TGIF might be a therapeutic target for improving the chemotherapy response in triple-negative breast cancer.

BHX, a novel pyrazoline derivative, inhibits breast cancer cell invasion by reversing the epithelial-mesenchymal transition and down-regulating Wnt/β-catenin signalling

The novel pyrazoline derivative, BHX, has recently been shown to exhibit potent anti-tumour activity by blocking the Wnt/β-catenin signalling pathway. However, its effect on breast cancer growth and invasion are unknown. Our results show that BHX suppresses MDA-MB-231 cell viability and colony formation in a dose-dependent manner, and induces apoptosis and G0/G1 phase arrest. BHX-treated breast cancer cells showed morphological characteristics of cells undergoing apoptosis. Furthermore, BHX inhibited cell migration and invasion, which was associated with increased E-cadherin mRNA and protein expression, and down-regulation of SNAIL and vimentin. In addition, BHX induced the generation of intracellular ROS and decreased β-catenin protein and mRNA expression. We used a mouse xenograft model to investigate the effects of BHX in vivo, where the growth of MDA-MB-231 xenografted tumours was suppressed in nude mice treated continuously with BHX for 21 days. Finally, the rat plasma concentration of BHX was measured by ultra-performance liquid-chromatography tandem mass spectrometry and the pharmacokinetic parameters of BHX were processed by non-compartmental analysis. In conclusion, BHX merits further study as a novel therapeutic small molecule for the treatment of breast cancer.

Characterization of contrasting features between hepatitis B virus genotype A and genotype D in small envelope protein expression and surface antigen secretion

Hepatitis B virus (HBV) genotypes A and D are prevalent in many parts of the world and show overlapping geographic distributions. We amplified the entire HBV genome from sera of patients with genotypes A and D and generated overlength constructs for transient transfection into Huh7 or HepG2 cells. Genotype D clones were associated with less HBsAg in culture supernatant and even less intracellular HBsAg. They produced less 2.1-kb RNA due to a weaker SPII promoter. Chimeric promoter constructs identified three divergent positions as most critical, and their exchange reversed extracellular HBsAg phenotype. The S protein of genotype D was more efficient at secretion, while its L protein possessed greater inhibitory effect. Swapping the S gene diminished genotypic difference in intracellular S protein but widened the difference in secreted HBsAg. In conclusion, HBV genotypes A and D differ in S protein expression, secretion and modulation by L protein.