CTLA4 and neoplasm: These observations suggest that the protumoral effects of GSNO may be associated with the CTLA-4 mediated hindrance of antitumor immunity, rather than direct effects of NO on tumor cell immunogenicity or proliferation, a hypothesis consistent with GSNO’s expansion of CTLA-4 expressing DCs, macrophages, and MDSCs and within LNs draining the locoregional site of injection.