A fluorescent substrate for ATX was recently adapted for use in an assay that detected lyso-PLD activity in membranes from HEK293 (human embryonic kidney) cells transfected with GDE4 and GDE7 and from untransfected LNCaP (human prostate cancer) and MCF-7 (human breast cancer) cells [67]. The gene discussed is GPLD1; the disease is breast cancer.