HMOX1 and cancer: We found high expression of HO-1 in tumor stroma and a negative correlation between stroma HO-1 and P-Erk1/2 (p=0.01, correlation coefficient by Spearman test, R2 = −0.47822), indicating that HO-1 might be a negative regulator of P-Erk1/2 signaling in the tumor microenvironment and/or cancer (Figure 6 and Figure 1, 3).