A new review reports that the matrix protein SPP1 (osteopontin) orchestrates immunosuppression across the tumor microenvironment and lays out emerging strategies to target it. The synthesis focuses on how SPP1 contributes to immune cell dysfunction and spatial immune reprogramming in solid tumors. By framing SPP1 as a coordinating node, the article ties mechanistic evidence to drug-discovery approaches that aim to disrupt immunosuppressive signaling rather than only deplete tumor cells. The review also positions SPP1 alongside other targets used to reshape tumor–immune interactions. For translational teams, the work offers a structured rationale to evaluate SPP1 pathway biomarkers and target engagement strategies in immunotherapy combinations.