FEN1 and cancer: While the batch-to-batch variation of PHH and/or antibody sensitivity might affect the Western blot detection, the results indicate that Mus81 and FEN1 may be upregulated in hepatoma cells due to the high rate of cancer cell proliferation and DNA damage compared to the nondividing PHHs [47–51], although down-regulation of Mus81 in hepatoma has also been reported [52].