Increase in ADAR1p110 activates the canonical Wnt signaling pathway associated with aggressive phenotype in triple negative breast cancer cells

A Comprehensive Analysis of the Effect of A>I(G) RNA-Editing Sites on Genotoxic Drug Response and Progression in Breast Cancer

Dysregulated A>I(G) RNA editing, which is mainly catalyzed by ADAR1 and is a type of post-transcriptional modification, has been linked to cancer. A low response to therapy in breast cancer (BC) is a significant contributor to mortality. However, it remains unclear if there is an association between A>I(G) RNA-edited sites and sensitivity to genotoxic drugs. To address this issue, we employed a stringent bioinformatics approach to identify differentially RNA-edited sites (DESs) associated with low or high sensitivity (FDR 0.1, log2 fold change 2.5) according to the IC50 of PARP inhibitors, anthracyclines, and alkylating agents using WGS/RNA-seq data in BC cell lines. We then validated these findings in patients with basal subtype BC. These DESs are mainly located in non-coding regions, but a lesser proportion in coding regions showed predicted deleterious consequences. Notably, some of these DESs are previously reported as oncogenic variants, and in genes related to DNA damage repair, drug metabolism, gene regulation, the cell cycle, and immune response. In patients with BC, we uncovered DESs predominantly in immune response genes, and a subset with a significant association (log-rank test p < 0.05) between RNA editing level in LSR, SMPDL3B, HTRA4, and LL22NC03-80A10.6 genes, and progression-free survival. Our findings provide a landscape of RNA-edited sites that may be involved in drug response mechanisms, highlighting the value of A>I(G) RNA editing in clinical outcomes for BC.

ADAR1 affects gastric cancer cell metastasis and reverses cisplatin resistance through AZIN1

Adenosine deaminases acting on RNA1 (ADAR1) are involved in the occurrence and development of cancers. Although the role of ADAR1 in gastric cancer metastasis has been reported, the role of ADAR1 in the mechanism of cisplatin resistance in gastric cancer is not clear. In this study, human gastric cancer tissue specimens were used to construct cisplatin-resistant gastric cancer cells; the results indicated that the mechanism underlying the inhibition of gastric cancer metastasis and reversal of cisplatin-resistant gastric cancer by ADAR1 inhibits gastric cancer occurs through the antizyme inhibitor 1 (AZIN1) pathway. We assessed ADAR1 and AZIN1 expression in the tissues of patients with low to moderately differentiated gastric cancer. Gastric cancer cells (human gastric adenocarcinoma cell line [AGS] and HGC-27 cells) and gastric cancer cisplatin-resistant cells (AGS CDDP and HGC-27 CDDP ) were selected, and the protein expression of ADAR1 and AZIN1 was detected using immunocytochemistry and immunocytofluorescence. The effects of ADAR1 small interfering RNA (siRNA) on the invasion, migration and proliferation of cisplatin-resistant gastric cancer cells were investigated. Western blot assays were used to assess the protein expression levels of ADAR1, AZIN1 and epithelial-mesenchymal transition (EMT)-related markers. In-vivo experiments, a subcutaneous tumor formation model of nude mice was established, and the effects of ADAR1 on tumor growth and AZIN1 expression level were detected by hematoxylin and eosin, immunohistochemistry and western blot. The expression of ADAR1 and AZIN1 in human gastric cancer tissue was significantly higher than that in paracancerous tissues. The colocalization of ADAR1, AZIN1 and E-cadherin expression in immunofluorescence assays indicated a significant correlation between the three. In in-vitro experiments, ADAR1 knockout not only reduced the invasion and migration ability of AGS and HGC-27 cells but also reduced that of cisplatin-resistant gastric cancer cells. ADAR1 siRNA inhibited the proliferation and decreased the colony number of cisplatin-resistant gastric cancer cells. ADAR1 siRNA decreased the expression of AZIN1 and EMT-related marker proteins (vimentin, N-cadherin, β-catenin, MMP9, MMP2 and TWIST). The effect of ADAR1 siRNA combined with AZIN1 siRNA was more significant. In-vivo, the knockdown of ADAR1 significantly inhibited tumor growth and AZIN1 expression. ADAR1 and AZIN1 are antimetastatic targets of gastric cancer, and AZIN1 is a downstream regulatory target of ADAR1. ADAR1 knockout can inhibit the metastasis of gastric cancer cells and reverse the cisplatin resistance of gastric cancer cells by downregulating the expression of AZIN1, potentially resulting in increased treatment efficacy.

Biological functions and molecular interactions of Wnt/β-catenin in breast cancer: Revisiting signaling networks

Changes in lifestyle such as physical activity and eating habits have been one of the main reasons for development of various diseases in modern world, especially cancer. However, role of genetic factors in initiation of cancer cannot be ignored and Wnt/β-catenin signaling is such factor that can affect tumor progression. Breast tumor is the most malignant tumor in females and it causes high mortality and morbidity around the world. The survival and prognosis of patients are not still desirable, although there have been advances in introducing new kinds of therapies and diagnosis. The present review provides an update of Wnt/β-catenin function in breast cancer malignancy. The upregulation of Wnt is commonly observed during progression of breast tumor and confirms that tumor cells are dependent on this pathway Wnt/β-catenin induction prevents apoptosis that is of importance for mediating drug resistance. Furthermore, Wnt/β-catenin signaling induces DNA damage repair in ameliorating radio-resistance. Wnt/β-catenin enhances proliferation and metastasis of breast tumor. Wnt/β-catenin induces EMT and elevates MMP expression. Furthermore, Wnt/β-catenin participates in tumor microenvironment remodeling and due to its tumor-promoting factor, drugs for its suppression have been developed. Different kinds of upstream mediators Wnt/β-catenin signaling in breast cancer have been recognized that their targeting is a therapeutic approach. Finally, Wnt/β-catenin can be considered as a biomarker in clinical trials.

ADAR1 and its implications in cancer development and treatment

The family of adenosine deaminases acting on RNA (ADARs) regulates global gene expression output by catalyzing adenosine-to-inosine (A-to-I) editing of double-stranded RNA (dsRNA) and through interacting with RNA and other proteins. ADARs play important roles in development and disease, including an increasing connection to cancer progression. ADAR1 has demonstrated a largely pro-oncogenic role in a growing list of cancer types, and its function in cancer has been attributed to diverse mechanisms. Here, we review existing literature on ADAR1 biology and function, its roles in human disease including cancer, and summarize known cancer-associated phenotypes and mechanisms. Lastly, we discuss implications and outstanding questions in the field, including strategies for targeting ADAR1 in cancer.