1171 Research Article Introduction Major features of lung adenocarcinoma (LADC) are rapid growth and high metastatic potential as well as resistance to irradiation and chemotherapy (Rosell et al., 2006). Cell proliferation and metastasis are regulated by the balance between growth factors and inhibitory molecules (Schaefer et al., 2007). Using suppression subtractive hybridization (SSH), microarray and hierarchical clustering to investigate gene expression patterns in patients with lung cancer, we found that hepatocyte growth factor (HGF) and HGF receptor (HGFR, or product of proto-oncogene met, MET) were highly expressed in advanced LADC patients who smoked. Cigarette smoking was further shown to be a key factor of disease progression and treatment failure (Chen et al., 2006). However, a portion of patients who did not respond well to therapies in Taiwan were women and nonsmokers (Sun et al., 2007). We used the same strategy to identify genes that were highly expressed in LADC. We then subtracted this LADC-specific gene pool from smoking-related genes. The resulting genes were subcategorized for ATPase and GTPase. The genes, of which the enzyme activity was activated by receptors, such as hepatocyte growth factor receptor (HGFR), epidermal growth factor receptor (EGFR) and HER2/neu, were excluded. Using this procedure, we identified three genes, encoding for dynamin-related protein 1 (DRP1) (Chiang et al., 2009), mitofusin 2 (Mfn-2) (de Brito and Scorrano, 2008a) and the ATPase family, AAA domain-containing protein 3 (ATAD3) (Hubstenberger et al., 2008), which were upregulated in LADC. DRP1 and Mfn-2 are GTPases, and ATAD3 is an ATPase. Three types of ATAD3 have been documented in the NCBI database (http://www. ncbi.nlm.gov): a 66-kDa ATAD3A (BC033109), a 72.6-kDa ATAD3B (NM_031921) and a 46-kDa ATAD3C (NM_001039211; the differences in protein sequences among ATAD3A, 3B and 3C are summarized in supplementary material Fig. S1A). Although protein sequence alignment indicates that ATAD3A and 3C are truncated isoforms of ATAD3B, they are encoded by different genes located in non-overlapping regions on chromosome 1 (supplementary material Fig. S1B,C). Moreover, ATAD3A contains 16 exons, 3B 15 exons and 3C 12 exons, indicating that ATAD3A and 3C are not alternatively spliced variants of ATAD3B. Using autoantibody-mediated identification of antigens (AMIDA), Gires et al. detected overexpression of KIAA1273/TOB3 (ATAD3B) in patients with head and neck cancer (Gires et al., 2004). Applying phage display to probe tumor-associated antigens, Geuijen et al. identified ATAD3A in acute myeloid leukemic (AML) blasts (Geuijen et al., 2005). Inhibition of ATAD3B expression by siRNA increased apoptosis (Schaffrik et al., 2006), but whether ATAD3B or ATAD3A were directly involved in programmed cell death, was not clear. In this study, we determined the expression level of ATAD3A in LADC cells and pathological specimens. The correlation between ATAD3A expression and patient survival was evaluated statistically. The effect of ATAD3A on cell growth and apoptosis was characterized in vitro. Results Expression of ATAD3A in LADC cells determined by RT-PCR Expression of ATAD3A was examined by RT-PCR in one HeLa and eight lung cancer cell lines. ATAD3A was detected in all cell ATPase family AAA domain-containing 3A is a novel anti-apoptotic factor in lung adenocarcinoma cells Hsin-Yuan Fang 1,2 , Chia-Ling Chang 3 , Shu-Han Hsu 3 , Chih-Yang Huang 4 , Shu-Fen Chiang 4 , Shiow-Her Chiou 4 , Chun-Hua Huang 3 , Yi-Ting Hsiao 3 , Tze-Yi Lin 5 , I-Ping Chiang 5 , Wen-Hu Hsu 6 , Sumio Sugano 7 , Chih-Yi Chen 2 , Ching-Yuang Lin 2 , Wen-Je Ko 1, * and Kuan-Chih Chow 3, * 1 Graduate Institute of Clinical Medicine, National Taiwan University, Taipei, Taiwan 2 Departments of Surgery, China Medical University Hospital, China Medical University, Taichung, Taiwan 3 Graduate Institute of Biomedical Sciences, and 4 Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taichung, Taiwan 5 Department of Pathology, China Medical University Hospital, Taichung, Taiwan 6 Division of Thoracic Surgery, Department of Surgery, Taipei Veterans General Hospital, Taipei, Taiwan 7 Laboratory of Functional Genomics, Department of Medical Genome Sciences, Graduate School of Frontier Sciences, the University of Tokyo, Tokyo, Japan *Authors for correspondence (wenje@ha.mc.ntu.edu.tw; kcchow@dragon.nchu.edu.tw) Accepted 3 January 2010 Journal of Cell Science 123, 1171-1180 © 2010. Published by The Company of Biologists Ltd doi:10.1242/jcs.062034 Summary AAA 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. Key words: ATAD3A, Lung adenocarcinoma, Mitochondrial fragmentation, Cisplatin sensitivity Journal of Cell Science