Furthermore, a conjugate of Pph-a with a cyclic cRGDfK peptide, with high binding affinity for integrin receptors overexpressed in many types of tumor cells or tumor vessels compared with normal cells, a highly hydrophilic polyethylene glycol chain and an extra strongly hydrophilic carboxylic acid inhibits the viability of some human cancer cell lines in vitro and reduces tumor volume in mice in vivo [44]. Here, ENO1 is linked to cancer.