Effects of ATRA on expression of mRNA binding protein p62 in human gastric cancer cells

The distribution of the cancer-associated protein p62 in human gastric carcinoma (BGC-823) cells was examined by confocal laser scanning microscopy and electron microscope immunocytochemistry. In control cells p62 was cytoplasmic in location and concentrated in the cytoplasmic matrix, but when cell growth was inhibited by treatment with 50 μM all-trans-retinoic acid (ATRA) for 5 days, p62 expression decreased and the protein was translocated from cytoplasm to nucleus. Ultrastructural localization using gold particles showed that p62 was bond mainly to a linear structure in nucleus. The speculation that p62 binds Insulin-like growth factor (IGF)-II mRNA indicates its probable involvement in the posttranscriptional IGF-II mRNA processing and p62 could play a role in tumorgenesis by regulating the expression of IGF-II. Further studies will be needed to confirm this view.