SummaryAAA domain-containing 3A (ATAD3A) is a member of the AAA-ATPase family. Three forms of ATAD3 have been identified: ATAD3A, ATAD3B and ATAD3C. In this study, we examined the type and expression of ATAD3 in lung adenocarcinoma (LADC). Expression of ATAD3A was detected by reverse transcription-polymerase chain reaction, immunoblotting, immunohistochemistry and confocal immunofluorescent microscopy. Our results show that ATAD3A is the major form expressed in LADC. Silencing of ATAD3A expression increased mitochondrial fragmentation and cisplatin sensitivity. Serum deprivation increased ATAD3A expression and drug resistance. These results suggest that ATAD3A could be an anti-apoptotic marker in LADC.

Dynamin-related protein 1 (DRP1), an 80 kDa GTPase, is involved in mitochondrial fission and anticancer drugmediated cytotoxicity, which implicate an association with disease progression of cancer. In this study we investigated the prognostic value of DRP1 in lung adenocarcinomas. Using immunohistochemistry, we measured the expression of DRP1 in 227 patients with lung adenocarcinomas. Expression of DRP1 was confirmed by immunoblotting. The correlation between DRP1 expression and clinicopathological parameters was analyzed by statistical analysis. Difference of survivals between different groups was compared by a logrank test. The results showed that DRP1 expression was detected in 202 patients with lung adenocarcinomas. Among these, nuclear DRP1 (DRP1 nuc ) was detected in 184 patients. A significant difference was found in cumulative survival between patients with high DRP1 nuc levels and those with DRP1 cyt levels (Po0.001). In vitro, hypoxia increased DRP1 nuc levels and cisplatin resistance. Antibodies specific to DRP1 co-precipitated a human homologue of yeast Rad23 protein A (hHR23A) and silencing of hHR23A decreased the nuclear DRP1 level and cisplatin resistance. In conclusion, DRP1 nuc is highly expressed in lung adenocarcinomas, and correlates with poor prognosis. Nuclear DRP1 may increase drug resistance during hypoxia, and hHR23A is essential for nuclear transportation of DRP1. Our results suggest that other than the protein level alone, intracellular distribution of the protein is critical for determining the protein function in cells.

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