CD44 and breast cancer: On the one hand, there is a positive correlationbetween HOX-1 activity and CD44 expression with essential roles playedin the self-renewal of human breast cancer stem cells.49 In addition, hemin is one of the main inducersof HOX-1 expression, causing heme/hemin degradation.50,51 This explains our findings, where, in the absence of •NO, hemin enhanced HOX-1 expression in MDA-MB-231 cells (Figure 5G).