KLK3 and prostate cancer: Taking into account that PSA has a high level of expression in prostate cancer cells, an anticancer system that feedback-inhibits PSA could be constructed if gRNA is used to target the expression of PSA. In this way, the highly expressed PSA signal of prostate cancer cells can be used to inhibit their own expression levels in turn through a built-in negative feedback system, thereby inhibiting tumors specifically and efficiently.