RNA interference: a promising therapy for gastric cancer

Long Non-Coding RNAs in Drug Resistance of Gastric Cancer: Complex Mechanisms and Potential Clinical Applications

Gastric cancer (GC) ranks as the third most prevalent malignancy and a leading cause of cancer-related mortality worldwide. However, the majority of patients with GC are diagnosed at an advanced stage, highlighting the urgent need for effective perioperative and postoperative chemotherapy to prevent relapse and metastasis. The current treatment strategies have limited overall efficacy because of intrinsic or acquired drug resistance. Recent evidence suggests that dysregulated long non-coding RNAs (lncRNAs) play a significant role in mediating drug resistance in GC. Therefore, there is an imperative to explore novel molecular mechanisms underlying drug resistance in order to overcome this challenging issue. With advancements in deep transcriptome sequencing technology, lncRNAs-once considered transcriptional noise-have garnered widespread attention as potential regulators of carcinogenesis, including tumor cell proliferation, metastasis, and sensitivity to chemo- or radiotherapy through multiple regulatory mechanisms. In light of these findings, we aim to review the mechanisms by which lncRNAs contribute to drug therapy resistance in GC with the goal of providing new insights and breakthroughs toward overcoming this formidable obstacle.

Long non-coding RNAs and gastric cancer: An update of potential biomarkers and therapeutic applications

The frequent metastasis of gastric cancer (GC) complicates the cure and therefore the development of effective diagnostic and therapeutic approaches is urgently necessary. In recent years, lncRNA has emerged as a drug target in the treatment of GC, particularly in the areas of cancer immunity, cancer metabolism, and cancer metastasis. This has led to the demonstration of the importance of these RNAs as prognostic, diagnostic and therapeutic agents. In this review, we provide an overview of the biological activities of lncRNAs in GC development and update the latest pathological activities, prognostic and diagnostic strategies, and therapeutic options for GC-related lncRNAs.

EXPRESSION OF THE RENIN-ANGIOTENSIN SYSTEM COMPONENTS IN ONCOLOGIC DISEASES

The literature devoted to changes in the expression of the renin-angiotensin system (RAS) proteins of cancer cells was analyzed. The dynamics of RAS protein expression in malignant tumors and the possible role of epigenetic mechanisms in these processes are briefly reviewed. Through research of the epigenetic mechanisms in cancer, principally new techniques for their correction based on the use of selective regulatory systems of covalent modification of histone proteins (for example, deacetylase inhibitor) and microRNA synthesis technologies have been developed. Literature data show promising pharmacological correction of epigenetic modification of chromatin in the treatment of cancer.

Reversal of Multidrug Resistance in an Epirubicin-Resistant Gastric Cancer Cell Subline

Background:

Gastric cancer is one of the most common malignancies worldwide. Epirubicin (EPI) is used extensively in the treatment of multiple cancers despite its tendency to induce multidrug resistance though overexpression of the ABCB1 efflux pump. However, this overexpression can be disrupted using short interfering RNAs (siRNAs).

Objective and Methods:

The aim of this study was to explore approaches to reverse EPI resistance and thus increase the success of chemotherapy treatment in an EPI-resistant gastric cancer cell subline (AGS/EPI).

Methods:

The study focused on effects of ABCB1 knockdown by siRNA technology using TaqMan gene expression assays with quantitative real-time reverse-transcription PCR (qRT-PCR). MTT assays were performed to evaluate viability and prolifer in subline. ABCB1 protein localization and EPI intracellular fluorescence intensity in AGS/EPI cells were detected by confocal microscopy.

Results:

The siRNA efficiently downregulated ABCB1 mRNA in AGS/EPI cells. Thus MDR reversal was clearly demonstrated in the AGS/EPI cells, offering the possibility of future in vitro chemoresistance assays for the GC field.

Conclusions:

ABCB1 knockdown decreased EPI efflux and increased EPI sensitivity in AGS/EPI cells. This result provides a novel strategy for targeted gene therapy to reverse EPI resistance in gastric cancer.

Molecular targeted therapy in gastric cancer

Gastric cancer is one of the most common malignant tumors in China. Traditional treatments such as surgery, radiotherapy and chemotherapy not only have side effects, but the treatment efficiency is also poor. Molecular targeted therapy, due to its high efficiency, low toxicity, and high orientation, has been widely used in the treatment of gastric cancer. Targets applied in molecular targeted therapy of gastric cancer are mainly related to the cytokine and receptors that contribute to gastric cancer cell growth, including epidermal growth factor and its receptors, vascular endothelial growth factor and its receptors, epithelial cell adhesion molecules, insulin-like growth factor and its receptors, and molecules related to the cell cycle. This review focuses on molecular targeted treatment in gastric cancer.

RNAi-based knockdown of multidrug resistance-associated protein 1 is sufficient to reverse multidrug resistance of human lung cells

Up-regulation of multidrug resistance-associated protein 1 (MRP1) is regarded as one of the main causes for multidrug resistance (MDR) of tumor cells, leading to failure of chemotherapy-based treatment for a multitude of cancers. However, whether silencing the overexpressed MRP1 is sufficient to reverse MDR has yet to be validated. This study demonstrated that RNAi-based knockdown of MRP1 reversed the increased efflux ability and MDR efficiently. Two different short haipin RNAs (shRNAs) targeting MRP1 were designed and inserted into pSilence- 2.1-neo. The shRNA recombinant plasmids were transfected into cis-dichlorodiamineplatinum-resistant A549 lung (A549/DDP) cells, and then shRNA expressing cell clones were collected and maintained. Real time PCR and immunofluorescence staining for MRP1 revealed a high silent efficiency of these two shRNAs. Functionally, shRNA-expressing cells showed increased rhodamine 123 retention in A549/DDP cells, indicating reduced efflux ability of tumor cells in the absence of MRP1. Consistently, MRP1-silent cells exhibited decreased resistance to 3- (4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and DDP, suggesting reversal of MDR in these tumor cells. Specifically, MRP1 knockdown increased the DDP-induced apoptosis of A549/DDP cells by increased trapping of their cell cycling in the G2 stage. Taken together, this study demonstrated that RNAi- based silencing of MRP1 is sufficient to reverse MDR in tumor cells, shedding light on possible novel clinical treatment of cancers.

Potential application of injectable chitosan hydrogel treated with siRNA in chronic rhinosinusitis therapy

Chronic rhinosinusitis is a condition with severe clinical symptoms and limited therapeutic solutions. It has been reported that vascular endothelial growth factor (VEGF) can promote nasal epithelial cell growth and result in hyperplasia of the sinuses. Therefore, the downregulation of VEGF may inhibit the process of hyperplasia. In the present study, small interfering RNA (siRNA) targeting VEGF was used to silence the expression of VEGF, and injectable chitosan based hydrogel, which is suitable for sinus injection and exhibits long-term retention, was prepared as the siRNA carrier. Human bronchial epithelial cells were cultured directly on the hydrogel to observe the biological performance in vitro. Further in vivo effects were investigated by the injection of the hydrogel into the sinus cavity. Following the introduction of siRNA introducing, the expression of VEGF in the bronchial epithelial cells was significantly suppressed at mRNA and protein levels. The number of living cells on the gel was significantly decreased, thus resulting in the inhibition of proliferation. However, the cytoskeletal arrangement of the remaining cells were not affected substantially. The hydrogel was able to retain the siRNA for an extended duration, which enabled a sustained supply of siRNA. The in vivo sinus mucosa analysis revealed that the siRNA was able to collocate with cells and the mucosa thickness was substantially decreased. In conclusion, the results of the present study suggested that injectable chitosan based hydrogel, treated with siRNA targeting VEGF, may be used as a convenient therapeutic option for chronic rhinosinusitis.

MicroRNA‑34a attenuates the proliferation, invasion and metastasis of gastric cancer cells via downregulation of MET

Proliferation, invasion and metastasis are key features of gastric cancer, contributing to high mortality rates in patients with gastric cancer worldwide. As a direct target of p53, the functions of microRNA (miR)‑34a are important, but controversial, in the progression of gastric cancer. In the present study, the clinical importance of miR‑34a in GC specimens (n=40) were investigated and were confirmed in an independent cohort from The Cancer Genome Atlas (TCGA; n=352). The prognostic value of miR‑34a was analyzed using a Kaplan‑Meier survival curve in the TCGA cohort, in combination with complete follow‑up data (n=157). The level of miR‑34a was detected in the human gastric cancer cell line and normal gastric epithelial cell line. The effect of miR‑34a on proliferation and invasion were evaluated using Cell Counting Kit 8, colony formation and cell invasion assays. The molecular basis of miR‑34a was determined by bioinformatics prediction. The correlation between miR‑34a and MET was assessed using reverse transcription‑quantitative polymerase chain reaction and western blot analyses. The results indicated that miR‑34a was downregulated in the gastric cancer tissues, compared with the normal gastric tissues (P<0.01). miR‑34a was negatively correlated with the depth of invasion and lymph node metastasis of gastric cancer (P<0.01). In the TCGA cohort, the levels of miR‑34a were lower in T3 and T4 tumor stages, compared with the level in the T1 stage, and low levels of miR‑34a predicted significantly longer survival rates in patients with GC (P<0.05). miR‑34a also attenuated the proliferation ability, and inhibited the colony formation and cell invasion abilities of the cells (P<0.01). A negative correlation was observed between miR‑34a and MET in gastric cancer (P<0.01; r=‑0.9526), and >60% of cases exhibited consistent expression of miR‑34a and MET in gastric cancer (P<0.01). In conclusion, miR‑34a was associated with the clinicopathological features of gastric cancer and was a valuable predictor of patient prognosis. miR‑34a acted as a tumor suppressor to inhibit gastric cancer proliferation and invasion via the downregulation of MET.