SMPD2 and hepatocellular carcinoma: Blocking exosome formation by a pharmacological inhibitor of neutral sphingomyelinase-2 (nSMase) GW4869 significantly inhibited the levels of exosomal circCCAR1, with no effect on the levels of circCCAR1 in HCC cells (Fig. 7H-I), thus confirming the existence of circCCAR1 in exosomes.