Targeting the Microenvironment in Advanced Colorectal Cancer

Colorectal cancer (CRC) diagnosis often occurs at late stages when tumor cells have already disseminated. Current therapies are poorly effective for metastatic disease, the main cause of death in CRC. Despite mounting evidence implicating the tumor microenvironment in CRC progression and metastasis, clinical practice remains predominantly focused on targeting the epithelial compartment. Because CRCs remain largely refractory to current therapies, we must devise alternative strategies. Transforming growth factor (TGF)-β has emerged as a key architect of the microenvironment in poor-prognosis cancers. Disseminated tumor cells show a strong dependency on a TGF-β-activated stroma during the establishment and subsequent expansion of metastasis. We review and discuss the development of integrated approaches focused on targeting the ecosystem of poor-prognosis CRCs.