CD44 and melanoma: Sheng et al. showed that serum carotenoids may affect the MAPK and PI3K/Akt signaling pathways of zeaxanthin by increasing cycle-related proteins P21 and P27 and regulating the levels of CD44 and CD105 on the epidermal membrane, thus inducing apoptosis of human gastric cancer cells and inhibiting the proliferation of melanoma cells (18, 21).