Protumor

Protumor refers to factors, cells, signals, and environments that promote tumor development and progression. In cancer biology, protumor elements act in contrast to antitumor or tumor-suppressive processes and contribute to initiation, growth, survival, invasion, metastasis, and therapy resistance. The protumor state often arises from interactions among cancer cells, stromal cells, immune cells, and the extracellular matrix within the tumor microenvironment.

Key components of protumor biology include tumor-associated macrophages (often with an M2-like phenotype), regulatory T cells, and myeloid-derived suppressor cells that dampen anti-tumor immunity; cancer-associated fibroblasts that remodel the extracellular matrix and secrete growth factors and chemokines; and endothelial and platelet-derived signals that drive angiogenesis and tumor perfusion. Pro-tumor signaling is driven by cytokines and growth factors such as TGF-beta, IL-6, and VEGF, as well as extracellular vesicles that transfer pro-tumor cargo. Hypoxic conditions within tumors further promote adaptation, survival, and aggressive behavior.

Clinical relevance lies in targeting protumor processes. Therapeutic strategies aim to disrupt these mechanisms by inhibiting angiogenesis, blocking pro-tumor signaling pathways, or reactivating anti-tumor immunity. Some components can have dual roles depending on context, complicating targeted approaches. The term protumor is used mainly in research to describe a pro-tumorigenic milieu and is not a formal disease category.