Roles of GST-π and polβ genes in chemoresistance of esophageal carcinoma cells

Overexpression of Glutathione S-Transferases in Human Diseases: Drug Targets and Therapeutic Implications

Glutathione S-transferases (GSTs) are a major class of phase II metabolic enzymes. Besides their essential role in detoxification, GSTs also exert diverse biological activities in the occurrence and development of various diseases. In the past few decades, much research interest has been paid to exploring the mechanisms of GST overexpression in tumor drug resistance. Correspondingly, many GST inhibitors have been developed and applied, solely or in combination with chemotherapeutic drugs, for the treatment of multi-drug resistant tumors. Moreover, novel roles of GSTs in other diseases, such as pulmonary fibrosis and neurodegenerative diseases, have been recognized in recent years, although the exact regulatory mechanisms remain to be elucidated. This review, firstly summarizes the roles of GSTs and their overexpression in the above-mentioned diseases with emphasis on the modulation of cell signaling pathways and protein functions. Secondly, specific GST inhibitors currently in pre-clinical development and in clinical stages are inventoried. Lastly, applications of GST inhibitors in targeting cell signaling pathways and intracellular biological processes are discussed, and the potential for disease treatment is prospected. Taken together, this review is expected to provide new insights into the interconnection between GST overexpression and human diseases, which may assist future drug discovery targeting GSTs.

Molecular mechanisms associated with chemoresistance in esophageal cancer

Esophageal cancer (EC) is one of the most incident and lethal tumors worldwide. Although surgical resection is an important approach in EC treatment, late diagnosis, metastasis and recurrence after surgery have led to the management of adjuvant and neoadjuvant therapies over the past few decades. In this scenario, 5-fluorouracil (5-FU) and cisplatin (CISP), and more recently paclitaxel (PTX) and carboplatin (CBP), have been traditionally used in EC treatment. However, chemoresistance to these agents along EC therapeutic management represents the main obstacle to successfully treat this malignancy. In this sense, despite the fact that most of chemotherapy drugs were discovered several decades ago, in many cases, including EC, they still represent the most affordable and widely employed treatment approach for these tumors. Therefore, this review summarizes the main mechanisms through which the response to the most widely chemotherapeutic agents used in EC treatment is impaired, such as drug metabolism, apoptosis resistance, cancer stem cells (CSCs), cell cycle, autophagy, energetic metabolism deregulation, tumor microenvironment and epigenetic modifications.

The reversal of drug resistance by two-dimensional titanium carbide Ti2 C (2D Ti2C) in non-small-cell lung cancer via the depletion of intracellular antioxidant reserves

Background

Chemoresistance is a major barrier limiting the therapeutic efficacy of late stage non‐small cell lung cancer (NSCLC). In this study, we sought to use two‐dimensional titanium carbide (2D Ti₂C) to reverse cisplatin resistance in NSCLC.

Methods

We first achieved favorable properties as a potential anti‐tumor agent. We then compared cell viability and cisplatin uptake in chemoresistant NSCLC cells before and after the use of 2D Ti₂C. Afterwards, we explored the effects of 2D Ti₂C on intracellular antioxidant reserves, followed by evaluating the subsequent changes in the expression of core drug resistance genes. Finally, we confirmed the tumor inhibitory effect and bio‐safety of 2D Ti₂C in a drug‐resistant lung cancer model in nude mice.

Results

Due to the properties of thin layer, large specific surface area, and abundant reactive groups on the surface, 2D Ti₂C can deplete the antioxidant reserve systems such as the glutathione redox buffer system, γ‐glutamylcysteine synthetase (γ‐GCS), glutathione peroxidase (GPx), glutathione‐S‐transferase‐Pi (GST‐π), and metallothionein (MT), thereby increasing the intracellular accumulation of cisplatin and decreasing the expression of drug resistance genes.

Conclusions

2D Ti₂C can reverse NSCLC chemoresistance both in vitro and in vivo, suggesting that it may potentially become a novel and effective means to treat chemoresistant NSCLC in the clinic.

Molecular mechanisms of chemo- and radiotherapy resistance and the potential implications for cancer treatment

Cancer is a leading cause of death worldwide. Surgery is the primary treatment approach for cancer, but the survival rate is very low due to the rapid progression of the disease and presence of local and distant metastasis at diagnosis. Adjuvant chemotherapy and radiotherapy are important components of the multidisciplinary approaches for cancer treatment. However, resistance to radiotherapy and chemotherapy may result in treatment failure or even cancer recurrence. Radioresistance in cancer is often caused by the repair response to radiation-induced DNA damage, cell cycle dysregulation, cancer stem cells (CSCs) resilience, and epithelial-mesenchymal transition (EMT). Understanding the molecular alterations that lead to radioresistance may provide new diagnostic markers and therapeutic targets to improve radiotherapy efficacy. Patients who develop resistance to chemotherapy drugs cannot benefit from the cytotoxicity induced by the prescribed drug and will likely have a poor outcome with these treatments. Chemotherapy often shows a low response rate due to various drug resistance mechanisms. This review focuses on the molecular mechanisms of radioresistance and chemoresistance in cancer and discusses recent developments in therapeutic strategies targeting chemoradiotherapy resistance to improve treatment outcomes.