The immunosuppressive tumor microenvironment (TME) fosters cancer progression, yet overarching determinants of cancer-borne immunoinstruction remain ill-defined. By multimodal integration of single-nucleus and bulk transcriptomics, proteomics, functional approaches, and clinical parameters, we discover a cancer-immunoinstructive secretory signature (CISS) across multiple human cancers-a set of inflammatory proteins correlated with poor prognosis and pro-tumorigenic TMEs. In pancreatic cancer (PC), CISS arises in pre-malignant epithelium, intensifies along transformation toward most malignant basal-like PC, and particularly correlates with suppressed natural killer (NK) cell activity. The CISS is quantitatively dominated by tissue inhibitor of metalloproteinases (TIMP)-1, most prevalent in TIMP-1hi/CISShi basal-like PC, and causal for PC-cell-mediated NK cell suppression, reflected by impaired cytotoxicity, interleukin-2 (IL-2) responses, and mammalian target of rapamycin (mTOR) signaling. In pre-clinical PC, TIMP-1/CISS proves targetable through combined inhibition of upstream kinases with clinically approved drugs trametinib and nintedanib. Collectively, CISS represents a ubiquitous signature of pro-tumor immunoinstruction with actionable diagnostic and therapeutic potential across human cancers.