Willin/FRMD6 may play a role in the function of secretory vesicles and exocytosis in neuronal cells, but the evidence for this remains indirect: Willin/FRMD6 colocalizes with SP-containing vesicles in nerve fibers and in vitro expression of preprotachykinin A, a SP precursor, in pituitary tumor AtT20 and breast cancer MCF-7 cells induces Willin/FRMD6 recruitment to large dense-core vesicles (LDCVs) [22]. This evidence concerns the gene TFF2 and pituitary tumor.