Targeting ATF4 overcomes dual resistance to chemo-immunotherapy in gastric cancer by disrupting the DNA damage response.

BACKGROUND

The efficacy of chemo-immunotherapy in gastric cancer (GC) is limited by heterogeneous resistance and the lack of predictive biomarkers. However, the molecular mechanisms underlying concurrent intrinsic chemoresistance and extrinsic immunosuppression remain poorly understood.

METHODS

We performed integrative analysis of single-cell RNA sequencing and bulk transcriptomic datasets from GC cohorts to identify key regulators of chemo-immunotherapy resistance. The functional role of activating transcription factor 4 (ATF4) was validated in GC cell lines, patient-derived organoids (PDOs), and patient-derived xenograft (PDX) models. Mechanistic investigations employed chromatin immunoprecipitation sequencing, RNA-seq, and multiplex immunofluorescence to elucidate the ATF4-HSPA9-DNA damage response (DDR) axis. Clinical relevance was assessed in GC patients treated with 5-fluorouracil (5-FU) monotherapy and those receiving combination 5-FU plus anti-PD-1 therapy.

RESULTS

We identify integrated stress-response transcription factor ATF4 as a key regulator of dual resistance. Mechanistically, ATF4 transcriptionally upregulates HSPA9 to activate the DDR, which promotes both intrinsic chemoresistance and extrinsic immunosuppression. ATF4 overexpression reduces 5-FU sensitivity and induces CD8+ T cell exhaustion in PDOs and PDX models. Clinically, low ATF4 expression correlates with improved survival in GC patients receiving chemo-immunotherapy.

CONCLUSIONS

These findings establish the ATF4-HSPA9 axis as a dual-function therapeutic target and predictive biomarker in GC chemo-immunotherapy. This axis bridges DNA damage repair-mediated chemoresistance and T cell exhaustion, providing a strategy to overcome resistance to 5-FU and PD-1 blockade.