CASP3 and neoplasm: CD44 is deeply involved in metastasis processes as (1) it facilitates cell adhesion to blood vessels and transendothelial migration, (2) it contributes to the maintenance of stem characteristics in tumor cells through the stimulation of key signaling pathways, (3) it confers resistance to drugs through an increased expression of the MDR1 multidrug resistance gene, and (4) it confers resistance to apoptosis by modifying the expression levels of caspase 3 and 9.