Clinical significance and correlation of miR-200c and P-gp expression in gastric cancer and the effects on multidrug resistance

Mechanism of multidrug resistance to chemotherapy mediated by P‑glycoprotein (Review)

Multidrug resistance (MDR) seriously limits the clinical application of chemotherapy. A mechanism underlying MDR is the overexpression of efflux transporters associated with chemotherapeutic drugs. P‑glycoprotein (P‑gp) is an ATP‑binding cassette (ABC) transporter, which promotes MDR by pumping out chemotherapeutic drugs and reducing their intracellular concentration. To date, overexpression of P‑gp has been detected in various types of chemoresistant cancer and inhibiting P‑gp‑related MDR has been suggested. The present review summarizes the mechanisms underlying MDR mediated by P‑gp in different tumors and evaluated the related signaling pathways, with the aim of improving understanding of the current status of P‑gp‑mediated chemotherapeutic resistance. This review focuses on the main mechanisms of inhibiting P‑gp‑mediated MDR, with the aim of providing a reference for the study of reversing P‑gp‑mediated MDR. The first mechanism involves decreasing the efflux activity of P‑gp by altering its conformation or hindering P‑gp‑chemotherapeutic drug binding. The second inhibitory mechanism involves inhibiting P‑gp expression to reduce efflux. The third inhibitory mechanism involves knocking out the ABCB1 gene. Potential strategies that can inhibit P‑gp include certain natural products, synthetic compounds and biological techniques. It is important to screen lead compounds or candidate techniques for P‑gp inhibition, and to identify inhibitors by targeting the relevant signaling pathways to overcome P‑gp‑mediated MDR.

Unrevealing the vital role of ncRNAs in Gastric Cancer chemoresistance

The high incidence of gastric cancer in many nations and poor overall survival rates has remained a serious global health concern. Chemoresistance in gastric cancer is a significant issue that hinders the efficacy of available treatment options. In gastric cancer, non-coding RNAs like microRNAs, long non-coding RNAs, and circular RNAs have become effective regulators of chemoresistance. These non-coding RNAs can influence several mechanisms, including drug efflux transporters, drug metabolism, and detoxification, cancer stem cells and the epithelial-mesenchymal transition, autophagy and apoptosis, and the tumor microenvironment. In this article review, we summarize the key roles non-coding RNAs play in the chemoresistance of gastric cancer and consider how they might be used in clinical settings as markers for diagnosis and prognosis, as well as potential targets and treatment plans. We also emphasize the need for additional study and collaborations in this area and highlight the difficulties and opportunities in non-coding RNA research for gastric cancer chemoresistance. This review offers crucial insights into the intricate relationship between non-coding RNAs and chemoresistance in gastric cancer, with implications for precision oncology and personalized medicine.

High miR-200c expression is associated with suppressed epithelial-mesenchymal transition, TGF-β signaling and better survival despite enhanced cell proliferation in gastric cancer patients

MicroRNAs are small non-coding RNAs that epigenetically regulate gene expression. MiR-200c is a known tumor suppressive microRNA found in many types of cancer, and its high expression has been associated with improved prognosis. However, the association between miR-200c expression and its clinical relevance in gastric cancer (GC) patients remains controversial. Here, we hypothesized that gastric cancer patients with high miR-200c gene expression translated to better overall survival. A total of 372 GC patients from the Cancer Genome Atlas (TCGA) were analyzed. The top three quartiles were defined as a high miR-200c expression group. High miR-200c expression was associated with decreased invasion, favorable histological type, and improved overall survival in gastric cancer patients. Unexpectedly, high miR-200c expression GC was also associated with enhanced cell proliferation, shown by MKi67 expression, proliferation score, and enrichment of Hallmark cell proliferation-related gene sets (E2F targets, G2M checkpoints, MYC targets v1 and v2) by gene set enrichment assay (GSEA). High miR-200c GC was also associated with a high mutation rate and homologous recombination deficiency. Despite the association with elevated neoantigens, high miR-200c GC was associated with significantly low infiltration of anti-cancer immune cells, decreased immune response, and with suppressed IL2, TNF-α, and IFN-γ pathways. On the other hand, GC with low miR-200c expression significantly enriched hypoxia, angiogenesis, epithelial-mesenchymal transition (EMT), and TGF-β signaling gene sets, all of which promote cancer progression and metastasis in GSEA. In conclusion, patients with high miR-200c expression GC had better survival despite association with aggressive tumor biology, such as high mutation rates, cell proliferation, and low cancer immunity. Given that low miR-200c GC was associated with hypoxia, angiogenesis, EMT and TGF-β signaling, we cannot help but speculate that the difference in survival by miR-200c expression may be at least partly due to the association between low miR-200c expression and aggressive biology.

An emphasis on the interaction of signaling pathways highlights the role of miRNAs in the etiology and treatment resistance of gastric cancer

Gastric cancer (GC) is 4th in incidence and mortality rates globally. Several genetic and epigenetic factors, including microRNAs (miRNAs), affect its initiation and progression. miRNAs are short chains of nucleic acids that can regulate several cellular processes by controlling their gene expression. So, dysregulation of miRNAs expressions is associated with GC initiation, progression, invasion capacity, apoptosis evasions, angiogenesis, promotion and EMT enhancement. Of important pathways in GC and controlled by miRNAs are Wnt/β-catenin signaling, HMGA2/mTOR/P-gp, PI3K/AKT/c-Myc, VEGFR and TGFb signaling. Hence, this review was conducted to review an updated view of the role of miRNAs in GC pathogenesis and their modulatory effects on responses to different GC treatment modalities.

Chalcones and Gastrointestinal Cancers: Experimental Evidence

Colorectal (CRC) and gastric cancers (GC) are the most common digestive tract cancers with a high incidence rate worldwide. The current treatment including surgery, chemotherapy or radiotherapy has several limitations such as drug toxicity, cancer recurrence or drug resistance and thus it is a great challenge to discover an effective and safe therapy for CRC and GC. In the last decade, numerous phytochemicals and their synthetic analogs have attracted attention due to their anticancer effect and low organ toxicity. Chalcones, plant-derived polyphenols, received marked attention due to their biological activities as well as for relatively easy structural manipulation and synthesis of new chalcone derivatives. In this study, we discuss the mechanisms by which chalcones in both in vitro and in vivo conditions suppress cancer cell proliferation or cancer formation.