Interleukin-8: a tumor-agnostic biomarker integrating cancer biology and host response across solid tumors

Interleukin-8 (IL-8/CXCL8) drives tumor progression via CXCR1/2 signaling, promoting proliferation, invasion, angiogenesis, and recruitment of pro-tumoral immune and stromal cells. Accumulating clinical evidence indicates that elevated circulating or intratumoral IL-8 levels are consistently associated with adverse prognosis and reduced therapeutic benefit across principal solid tumors. In particular, IL-8 has emerged as a promising prognostic and predictive biomarker of resistance to immune checkpoint inhibitors. This review highlights its prognostic and predictive value across gastrointestinal, genitourinary, lung, melanoma, breast, ovarian, and head and neck cancers, and discusses strategies targeting IL-8 and the need for standardized, clinically actionable assays.