Chromosomal instability shapes the tumor microenvironment of esophageal adenocarcinoma via a cGAS–chemokine–myeloid axis

Chromosomal instability (CIN), a pervasive feature of esophageal adenocarcinoma (EAC), drives tumor aggressiveness and metastasis. CIN stimulates the cGAS-STING pathway, typically linked to antitumor immunity. However, despite the high CIN burden in EAC, the cGAS-STING pathway remains largely intact. To address this paradox, we interrogated multiple esophageal cancer models, finding myeloid-attracting chemokines-with <i>CXCL8</i> as a prominent hit-as conserved CIN-driven targets in EAC. Using multiplexed immunofluorescence microscopy, we quantified ongoing CIN in human EAC tumors by measuring cGAS-positive micronuclei, validated by whole-genome sequencing. Coupling in situ CIN detection with single-nucleus RNA sequencing and multiplex immunophenotyping of human EAC, we link CIN to tumor-intrinsic innate immune activation, <i>CXCL8</i> expression, and myeloid cell-mediated immunosuppression. In patients with EAC, CIN^high, myeloid-dominated tumors correlate with poor outcomes and aberrant cGAS-STING signaling. These insights explain the counterintuitive maintenance of cGAS-STING and highlight the disruption of the CIN-cGAS-inflammation axis as a potential therapeutic strategy in EAC.