PCP4 and cancer: However, an association between PCP4/PEP19 expression and cancer cell apoptosis has not been fully investigated yet and is largely disregarded in current discussion, even though our previous study showed that PCP4/PEP19 expression in the mammary gland tissue was significantly increased during rat carcinogenesis stimulated by 7, 12-dimethylbenz [a] anthracene (DMBA) exposure [15].