Tripartite motif-containing protein 28 promotes drug resistance to bortezomib in gastric cancer through proteasome activity regulation

Objective: Gastric cancer (GC) persists as a leading global cause of cancer-related mortality. Although bortezomib (BTZ), a proteasome inhibitor, has demonstrated efficacy in treating various cancers, its therapeutic potential is hindered by drug resistance in GC. This study aims to explore the regulatory role of tripartite motif-containing protein 28 (TRIM28) in BTZ resistance in GC cells and to evaluate the antitumor effect of targeting TRIM28 in combination with BTZ. Material and Methods: We established control groups (including Lenti-control and short hairpin non-targeting control groups), TRIM28-overexpressing (OE), and TRIM28-knockdown models using the MGC-803 gastric cancer cell line to investigate TRIM28-mediated BTZ resistance. A series of assays was performed, including cell counting kit-8 analysis to assess cell viability, flow cytometry for apoptosis analysis, colony formation assays to evaluate cell proliferation, western blot to measure the protein expression of 20S proteasome subunits (α1/4 and β1/2/5), proteasome activity assays, and immunohistochemistry to assess TRIM28 expression in clinical samples. Bioinformatic tools were also used to analyze the clinical correlation of TRIM28 expression with cancer stage and grade. Results: Our results demonstrate that TRIM28 markedly enhanced BTZ resistance in GC cells. TRIM28 OE increased cell viability, inhibited apoptosis, enhanced colony-forming ability, upregulated the expression of proteasome subunits, and increased proteasome activity, contributing to a protective effect against BTZ-induced cytotoxicity. For the clinical GC samples, TRIM28 was highly expressed in tumor tissues, and its expression was correlated with advanced cancer stages and high tumor grades. Conclusion: TRIM28 is critical in promoting BTZ resistance in GC cells. Targeting TRIM28 could potentiate BTZ treatment outcomes and offer a promising therapeutic strategy for overcoming drug resistance in GC treatment.