ABCG2 and posterior cortical atrophy: Nevertheless, in the radioresistant PCa cells, the radiosensitizing effect of 5-ALA was limited compared to the parental PCa cells (PC-3-R, p < 0.001; DU 145-R, p < 0.001), which may be attributable to the upregulation of the drug transporter ABCG2 in radioresistant PCa cells (PC-3-R, p < 0.001; DU 145-R, p = 0.020; Myc-CaP-R, p = 0.004).