ARG1 and neoplasm: It was further found that HOXA1 overexpression downregulated the activity of the immunosuppressive molecule Arg1 and ROS production in MDSCs and that HOXA1 overexpression enhanced CD4+ Th1 and CD8+ CTL cell initiation so that HOXA1 overexpression enhanced the anti-tumour T-cell response and suppressed the immunosuppressive effect of MDSCs, thereby delaying tumour progression (80).