In prostate cancer, low Smad4 expression is associated with a significantly increased infiltration of memory B cells, CD8+ T cells, Tregs, and M2-type macrophages66; while in PDAC, the direct effect of Smad4 mutations on macrophages has not been clearly studied, although Smad4 plays a key role in the recruitment of immuno-infiltrating cells.67 The gene discussed is SMAD4; the disease is prostate cancer.