Since tumor cell motility has been proposed to involve CD13 binding to NGR motifs on fibronectin [25], and mAbs C and E are able to inhibit CD13-mediated cell binding to fibronectin, one possibility is that mAbs C and E in some way affect the region of CD13 involved in NGR binding, which is the catalytic site [25]. The gene discussed is FN1; the disease is neoplasm.