C-myc, a downstream target of the Erk1/2 pathway, was also strongly elevated in A549 xenograft tumors in mice treated with CO at 100 ppm twice per week and 250 ppm daily (Figure 1B, Supplementary Figure S1G) and unexpectedly correlated with strong suppression of tumor growth (Figure 1A). This evidence concerns the gene MYC and neoplasm.