In vitro studies showed that blockade of Rab27a or nSMase2 does not change cell proliferation in prostate cancer, colorectal cancer, or breast cancer, indicating that blockade of exosome biogenesis itself does not cause the suppression of tumor growth (Yang et al., 2018; Poggio et al., 2019). The gene discussed is SMPD3; the disease is breast carcinoma.