SIRT7 and angiosarcoma: • miR-340 expression was considerably lower in angiosarcoma than controls.• Overexpression of miR-340 decreased angiosarcoma cell proliferation and invasion.• Sirtuin 7 (SIRT7) may be a miR-340 target gene.• Overexpression of SIRT7 increased angiosarcoma cell proliferation and invasion and partially reversed miR-340’s anticancer impact.