For example, p16Ink-penetratin [94], p27kip-Tat [95], and p21WAF1/CIP1-Tat [96] (Table 4), which are composed of CPPs linked to peptides derived from natural protein inhibitors of cyclin-dependent kinases (CDKs), have been reported to inhibit tumor growth in vitro and in vivo. This evidence concerns the gene TAT and neoplasm.