No or weak P-gp, MRP1 or MRP2 immunostaining was significantly more frequent in sarcomatoid mesothelimas than in epithelial or biphasic mesotheliomas (P = 0.031, P = 0.034 and P = 0.024, respectively).
These same MRP genes, including, to a lesser extent, MRP-4, were also expressed in pleural mesotheliomas derived from patients as shown by the same methodology.