BMC Cancer 2006, 6:109 http://www.biomedcentral.com/1471-2407/6/109 of KIAA0101 by cDNA transfection in HEK293 cells had no effect on cell growth on this immortalized human renal cells[9]. Our data did demonstrate that KIAA0101 over-expression could retard the cell growth of human HCC cells. These data were further supported by the results of cell cycle analysis which indicated the arrest at G1/S transition in KIAA0101 over-expressed cells. The inconsistency between our data and those from other lab- oratories might be attributed to different types of cancers or cells used for studies. It is probable that KIAA0101 might have different expression pattern in various types of cancers. Also the possibility that KIAA0101 may play var- ious biological roles in different types of normal and can- cer cells could not be excluded. Moreover, the discrepancy of data between level of mRNA and protein expression in the same tissue has been reported[11]. In chen's report, they compared the level of mRNA with protein expression among 165 proteins. A subset of proteins demonstrated a negative correlation with the mRNA expression value. Thus the possibility that a negative correlation existed between KIAA0101 mRNA with protein level could not be excluded. It may also interpret, at least in part, the contro- versial data about mRNA and protein expression of KIAA0101 genes from different laboratories. In our observation, the KIAA0101 gene product was pre- dominantly localized in mitochondria of human HCC cells, but the minor portion was found in nuclei. A recent report by Simpson F etal has described that KIAA0101 was predominantly found in mitochondria of human renal HEK293 cells, but it could translocate into nuclei after UV exposure. It was found that KIAA0101 could bind to PCNA and a putative tumor suppressor[9]. Therefore, the KIAA0101 may have a complex feature in its signal path- way and further studies of KIAA0101 are needed to explore its signal pathway in human HCC cells. Taken together, our findings may put some insight on fur- ther elucidation of KIAA0101 in regulatory mechanism of cell growth and its relevance to HCC development and progression. Conclusion This is the first report to demonstrate the down-regulation of KIAA0101 at protein level in human HCC and its over- expression could inhibit the human HCC cell growth. Abbreviations HCC: hepatocellular carcinoma; FACS: flow-asisted cell sorting; ISH: in situ hybridization; MACS: magnetic acti- vated cell sorting. Competing interests The author(s) declared they have no competing interests. Authors' contributions All the authors contributed to the conception during the initial stages and study design, and in the analysis and interpretation of the data, as well as to the drafting and critical revision of the important intellectual content. All the authors agreed to the final approval of the version to be published. Professor Jianren Gu was in charge of the general supervision of this research. The coauthors declare the order of authorship was based on a joint decision. Additional material Additional File 1 Table 1: The KIAA0101 protein expression in HCC, non-cancerous liver tissues, liver cirrhosis and normal liver tissues. The KIAA0101 protein expression was investigated in 161 pairs of tumor tissues and their coun- terpart non-cancerous liver tissue, 13 liver cirrhosis and 10 normal liver tissues by ISH. The results showed that in 107/161 tumor tissues, the intensity of KIAA0101 protein expression was + or -; while only in 24/161 non-cancerous liver tissues, the signal intensity was + or - (P < 0.05). (NT: non-tumor tissue; T: tumor tissue; LC: liver cirrhosis; NL: normal liver tissue). Click here for file [http://www.biomedcentral.com/content/supplementary/1471- 2407-6-109-S1.doc] Additional File 2 Supplement Table 1. Comparison of KIAA0101 expression level and serological HBV markers in HCC patients Serological HBV markers included HBsAg, HBcAb, HBeAg, HbsAb, HBeAb and others. HBsAg (+), HBcAb (+), HBeAg (+) indicated patients as HBV (+). Statistical analysis indicated that the KIAA0101 (-)/(+) versus (++)/(+++) groups had no statistical difference between HBV(+) and HBV (-) patients. Sup- plementary Table 2. Expression of KIAA0101 in HCC with different his- topathologicalgrades. The histopathological grading was according to standard of childpugh. 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