Search

Bladder cancer poses a significant challenge to chemotherapy due to its resistance to cisplatin, especially at advanced stages. Understanding the mechanisms behind cisplatin resistance is crucial for improving cancer therapy. The enzyme glutathione S‐transferase omega class 1 (GSTO1) is known to be involved in cisplatin resistance in colon cancer. This study focused on its role in cisplatin resistance in bladder cancer. Our analysis of protein expression in bladder cancer cells stimulated by secretions from tumor‐associated macrophages (TAMs) showed a significant increase in GSTO1. This prompted further investigation into the role of GSTO1 in bladder cancer. We found a strong correlation between GSTO1 expression and cisplatin resistance. Mechanistically, GSTO1 triggered the release of large extracellular vesicles (EVs) that promoted cisplatin efflux, thereby reducing cisplatin–DNA adduct formation and enhancing cisplatin resistance. Inhibition of EV release effectively counteracted the cisplatin resistance associated with GSTO1. In conclusion, GSTO1‐mediated EV release may contribute to cisplatin resistance caused by TAMs in bladder cancer. Strategies to target GSTO1 could potentially improve the efficacy of cisplatin in treating bladder cancer. [ABSTRACT FROM AUTHOR]

Ocimum gratissimum (O. gratissimum), a medicinal herb with antifungal and antiviral activities, has been found to prevent liver injury and liver fibrosis and induce apoptosis in hepatocellular carcinoma (HCC) cells. In this study, we evaluated the effect of aqueous extracts of O. gratissimum (OGE) on improving the efficacy of chemotherapeutic drugs in HCC cells. Proteomic identification and functional assays were used to uncover the critical molecules responsible for OGE-induced sensitization mechanisms. The antitumor activity of OGE in combination with a chemotherapeutic drug was evaluated in a mouse orthotopic tumor model, and serum biochemical tests were further utilized to validate liver function. OGE sensitized HCC cells to the chemotherapeutic drug cisplatin. Proteomic analysis and Western blotting validation revealed the sensitization effect of OGE, likely achieved through the inhibition of breast cancer type 1 susceptibility protein (BRCA1). Mechanically, OGE treatment resulted in BRCA1 protein instability and increased proteasomal degradation, thereby synergistically increasing cisplatin-induced DNA damage. Moreover, OGE effectively inhibited cell migration and invasion, modulated epithelial-to-mesenchymal transition (EMT), and impaired stemness properties in HCC cells. The combinatorial use of OGE enhanced the efficacy of cisplatin and potentially restored liver function in a mouse orthotopic tumor model. Our findings may provide an alternate approach to improving chemotherapy efficacy in HCC. [ABSTRACT FROM AUTHOR]

Posttranslational modifications to the intracellular domain of the EGFR are known to regulate EGFR functions; however, modifications to the extracellular domain and their effects remain relatively unexplored. Here, we determined that methylation at R198 and R200 of the EGFR extracellular domain by protein arginine methyltransferase 1 (PRMT1) enhances binding to EGF and subsequent receptor dimerization and signaling activation. In a mouse orthotopic colorectal cancer xenograft model, expression of a methylation-defective EGFR reduced tumor growth. Moreover, increased EGFR methylation sustained signaling activation and cell proliferation in the presence of the therapeutic EGFR monoclonal antibody cetuximab. In colorectal cancer patients, EGFR methylation level also correlated with a higher recurrence rate after cetuximab treatment and reduced overall survival. Together, these data indicate that R198/R200 methylation of the EGFR plays an important role in regulating EGFR functionality and resistance to cetuximab treatment.

Glycosylation of immune receptors and ligands, such as T cell receptor and coinhibitory molecules, regulates immune signaling activation and immune surveillance. However, how oncogenic signaling initiates glycosylation of coinhibitory molecules to induce immunosuppression remains unclear. Here we show that IL-6-activated JAK1 phosphorylates programmed death-ligand 1 (PD-L1) Tyr112, which recruits the endoplasmic reticulum-associated N-glycosyltransferase STT3A to catalyze PD-L1 glycosylation and maintain PD-L1 stability. Targeting of IL-6 by IL-6 antibody induced synergistic T cell killing effects when combined with anti-T cell immunoglobulin mucin-3 (anti-Tim-3) therapy in animal models. A positive correlation between IL-6 and PD-L1 expression was also observed in hepatocellular carcinoma patient tumor tissues. These results identify a mechanism regulating PD-L1 glycosylation initiation and suggest the combination of anti-IL-6 and anti-Tim-3 as an effective marker-guided therapeutic strategy., Introduction Programmed death-ligand 1 (PD-L1; also known as B7 homolog 1 and CD274) is an immune checkpoint protein, and its engagement with programmed cell death protein-1 (PD-1) receptor on T [...]

Taxanes, particularly docetaxel (DTX), has been widely used for combination therapy of head and neck squamous cell carcinoma (HNSCC). For locally advanced unresectable HNSCC, DTX combined with cisplatin and 5-fluorouracil as a revolutionary treatment revealed an advantage in the improvement of patient outcome. In addition, DTX plus immune check inhibitors (ICIs) showed low toxicity and an increased response of patients with recurrent or metastatic HNSCC (R/M HNSCC). Accumulated data indicate that taxanes not only function as antimitotics but also impair diverse oncogenic signalings, including angiogenesis, inflammatory response, ROS production, and apoptosis induction. However, despite an initial response, the development of resistance remains a major obstacle to treatment response. Taxane resistance could result from intrinsic mechanisms, such as enhanced DNA/RNA damage repair, increased drug efflux, and apoptosis inhibition, and extrinsic effects, such as angiogenesis and interactions between tumor cells and immune cells. This review provides an overview of taxanes therapy applied in different stages of HNSCC and describe the mechanisms of taxane resistance in HNSCC. Through a detailed understanding, the mechanisms of resistance may help in developing the potential therapeutic methods and the effective combination strategies to overcome drug resistance. [ABSTRACT FROM AUTHOR]

Poly (ADP-ribose) polymerase (PARP) inhibitors have emerged as promising therapeutics for many diseases, including cancer, in clinical trials (1). One PARP inhibitor, olaparib (Lynparza, AstraZeneca), was recently approved by the FDA to treat ovarian cancer with mutations in BRCA genes. BRCA1 and BRCA2 have essential roles in repairing DNA double-strand breaks, and a deficiency of BRCA proteins sensitizes cancer cells to PARP inhibition (2,3). Here we show that the receptor tyrosine kinase c-Met associates with and phosphorylates PARP1 at Tyr907 (PARP1 pTyr907 or pY907). PARP1 pY907 increases PARP1 enzymatic activity and reduces binding to a PARP inhibitor, thereby rendering cancer cells resistant to PARP inhibition. The combination of c-Met and PARP1 inhibitors synergized to suppress the growth of breast cancer cells in vitro and xenograft tumor models, and we observed similar synergistic effects in a lung cancer xenograft tumor model. These results suggest that the abundance of PARP1 pY907 may predict tumor resistance to PARP inhibitors, and that treatment with a combination of c-Met and PARP inhibitors may benefit patients whose tumors show high c-Met expression and who do not respond to PARP inhibition alone., Increased levels of reactive oxygen species (ROS) in cells can cause oxidative DNA damage that leads to genomic instability and tumor development (4-7). ROS-induced DNA damage, such as single-strand breaks [...]

MicroRNAs (miRNAs) are generated by two-step processing to yield small RNAs that negatively regulate target gene expression at the post-transcriptional level (1). Deregulation of miRNAs has been linked to diverse [...]