Temozolomide Resistance in Smoking-Related Bladder Cancer through TNFAIP6-Mediated Post-Translational Modifications.

Background: Lung adenocarcinoma (LUAD) and bladder cancer (BLCA) are two major cancers that have high incidence and mortality worldwide and are particularly exacerbated by smoking, which is a primary risk factor that influences cancer progression through genetic and immune pathways. Temozolomide (TMZ), a chemotherapeutic agent, is often used to treat various cancers, including brain tumours, and is known to induce DNA damage via methylation. This study aims to identify key smoking-related genes, particularly TNFAIP6, and explore their mechanisms in LUAD and BLCA, focusing on their prognostic value, role in cancer progression, immune regulation, and response to TMZ.

Methods: Bayesian colocalisation and pan-cancer differential analyses identified 14 key genes, including TNFAIP6. Pan-cancer survival and clinical stage analyses were performed using The Cancer Genome Atlas (TCGA) data. TNFAIP6's functional role in cancer stages, smoking status, immune infiltration and its effect on TMZ resistance was analysed through statistical tests, gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA). Laboratory experiments were conducted to assess TNFAIP6's influence on cell proliferation, apoptosis, epithelial-mesenchymal transition (EMT) markers, oxidative stress and TMZ-induced post-translational modifications (PTMs).

Results: TNFAIP6 was significantly upregulated in LUAD and BLCA and linked to poorer prognosis, especially in smokers. High TNFAIP6 expression was associated with pro-inflammatory pathways and immune suppression in the tumour microenvironment. Moreover, TMZ treatment induced considerable PTMs in TNFAIP6, promoting resistance to the drug, which was confirmed by functional assays showing increased cell viability and migration in TNFAIP6-overexpressing cells.

Conclusions: TNFAIP6 is a key biomarker of poor prognosis in smoking-related cancers. Interestingly, silencing TNFAIP6 both inhibits TMZ's anticancer effects and underscores its potential role in immune regulation, highlighting the paradoxical value of TNFAIP6 in developing novel therapeutic strategies, including combination therapies.