These data indicate that loss of Vamp8 occurs as murine mammary tumours progress from DCIS to IDC and that Vamp8 levels are maintained in less-aggressive luminal-A and low-grade human tumours in comparison to more-aggressive cancers, which is consistent with an anti-invasive role for Rab17 and Vamp8. The gene discussed is RAB17; the disease is ductal breast carcinoma in situ.