ERBB2 and posterior cortical atrophy: To study androgen effect on PCa cell proliferation, we analyzed the protein level of cellular prostatic acid phosphatase (cPAcP), an authentic PTP, as a marker for androgen action; because cPAcP functions as a negative growth regulator by dephosphorylating ErbB-2 tyrosine phosphorylation [26], [27], [28].