Expression pattern of parkin isoforms in lung adenocarcinomas

The parkin gene has been shown to be genetically altered in a wide variety of human tumors including lung cancer. Although many parkin splice variants have been identified, to date, most of the studies have only been focused on originally cloned isoforms. In this work, for the first time, the expression profile of parkin isoforms in human lung adenocarcinomas has been analyzed to identify their involvement in lung cancer. Their contribution in some biological conditions, such as proteasomal degradation or mitophagy or cell death, has been analyzed in human lung cells. The expression profile of parkin isoforms has been investigated in paraffin-embedded samples of human lung adenocarcinomas by using Western blot analysis. Their expression has also been evaluated in human lung adenocarcinoma and in human normal bronchial epithelial cell lines following treatment with a proteasome inhibitor or mitochondrial depolarizing agent, or in serum starvation. Parkin proteins were detected on blot by using two antibodies, AbI and AbII, which recognize different domains of originally cloned parkin. Furthermore, parkin immunolocalization has been visualized in both cell lines by using immunofluorescence analysis. Results have shown that H1 and/or H5, H14, H4 and/or H8 and/or H17 and H3 and/or H12 isoforms are expressed in human lung adenocarcinomas. Some of them are also present in A549 cell line, whereas they are absent or faintly expressed in BEAS-2B cells. Furthermore, their expression changed after treatment. Human lung adenocarcinomas express different parkin isoforms, which might represent markers of malignancy and could be linked to specific biological functions.