SFRP1 and prostate cancer: Studies using 3D co-cultures (human CRPC 22Rv1 or PC-3 cells cultured with mouse primary wildtype prostatic fibroblasts) or co-engrafted xenografts (22Rv1 cells co-injected with CAFs) show that CD105 signaling in CAFs drives increased secretion of the Wnt regulator SFRP1 upon enzalutamide treatment, which correlates with expansion of the CD105-positive CAF population that promote neuroendocrine differentiation of adjacent prostate cancer epithelial cells in a paracrine manner [6].