Siamese Crocodile White Blood Cell Extract Inhibits Cell Proliferation and Promotes Autophagy in Multiple Cancer Cell Lines

Cancer represents one of the most significant threats to human health on a global scale. Hence, the development of effective cancer prevention strategies, as well as the discovery of novel therapeutic agents against cancer, is urgently required. In light of this challenge, this research aimed to evaluate the effects of several potent bioactive peptides and proteins contained in crocodile white blood cell extract (cWBC) against LU-1, LNCaP, PC-3, MCF-7, and CaCo-2 cancer cell lines. The results demonstrate that 25, 50, 100, and $200{\mu}g/ml$ cWBC exhibits a strong cytotoxic effect against all investigated cell lines ($IC_{50}$ $70.34-101.0{\mu}g/ml$), while showing no signs of cytotoxicity towards noncancerous Vero and HaCaT cells. Specifically, cWBC treatment caused a significant reduction in the cancerous cells' colony forming ability. A remarkable suppression of cancerous cell migration was observed after treatment with cWBC, indicating potent antimetastatic properties. The mechanism involved in the cancer cell cytotoxicity of cWBC may be related to apoptosis induction, as evidenced by typical apoptotic morphology features. Moreover, certain cWBC concentrations induced significant overproduction of ROS and significantly inhibited the $S-G_2/M$ transition in the cancer cell. The molecular mechanisms of cWBC in apoptosis induction were to decrease Bcl-2 and XIAP expression levels and increase the expression levels of caspase-3, caspase-8, and p53. These led to a decrease in the expression level of the cell cycle-associated gene cyclin-B1 and the arrest of cell population growth. Consequently, these findings demonstrate the prospect of the use of cWBC for cancer therapy.