All these findings equivocally demonstrate that a crucial factor that determines the detection of EPR HbNO signals in the tissue is cancellation of barriers between the sites where NO is formed (cytoplasm of cells responsible for inflammation, mainly macrophages, perhaps also endothelium and neutrophils) and where it is trapped by Hb (initially inside of erythrocytes in tumor capillaries). This evidence concerns the gene GSTM1 and neoplasm.