SMAD4 and malignant colon neoplasm: Our observation is supported by a recent publication in which C–C chemokine receptor type 1 (CCR1)–positive myeloid cells (CD34+) are shown to be recruited to colon cancers with deletion of Smad4 and promote tumor invasion.(32) Indeed, inflammatory cells (positive for CD45 and BM8, a pan-macrophage marker) have been observed in head-and-neck tumors lacking TGF-β signaling.(33) In TGF-β1-deficient mice, inflammation causes precancerous lesions to progress to colon cancer.(34)