During the SSCP analysis, we found a SNP (Gln 302 Arg) which was relatively frequent in lung cancer tissues. Recently, a Fosbretabulin report that the same SNP of Rad18 is associated to the risk of lung cancer was published [18]. Different to our study, LGX818 in vivo this report was focused only on the SNP and the mutation analysis of the entire Rad18 gene was not evaluated. They used only genomic DNA extracted from a formalin embedded lung cancer tissue which was PCR amplified and checked only the status of codon 302 SNP and concluded that this SNP is the risk of lung cancer development. The total number of the

lung cancer sample was quite large and the frequency of SNP and lung cancer development was statistically different. If this single nucleotide change (which changes the amino acid sequence) is the cause of lung cancer, this is no more a “”polymorphism”" but a “”mutation”". And if this nucleotide change is a “”mutation”", there should be a difference in the function between these two different proteins. Based on the function of Rad18, as a CCI-779 datasheet key protein of PRR system, the sensitivity to the DNA damaging reagents (cisplatin and CPT-11) were examined according to the reports [19, 20]. Furthermore, when Rad18 is null, it is reported that the growth of the cells won’t change but the abnormal

morphologies with nuclear segregation will occur [21, 22]. Thus we investigated the differences of cell morphology, cell growth and sensitivity to anti-drug agents. Unfortunately, we could not find a difference from both clinical samples and in vitro study. Furthermore, no difference

was observed in DNA repair function. Different to the report, we used mRNA and analyzed the whole open reading frame of Rad18 gene and also examined the expression level, in vitro analysis. Conclusion From all these results, we came to a conclusion that, there is no relation between Rad18 and lung cancer development. Methocarbamol Still there is a possibility that PRR system might be involved in cancer development. As Rad18 interacts with Rad6 and function as a ubiquitin enzyme to activate PCNA, if these key proteins were involved in cancer, the PRR system will not function and might lead to cancer development. Further analysis of this system is required to clear whether there is a relation between PRR and cancer development. Acknowledgements This study was supported by a grant-in-aid from the Ministry of Education, Culture, and Science of Japan. References 1. Heinen CD, Schmutte C, Fishel R: DNA repair and tumorigenesis: lessons from hereditary cancer syndromes. Cancer Biol Ther 2002, 5: 477–85. 2. Lovett ST: Polymerase switching in DNA replication. Mol Cell 2007, 27: 523–6.CrossRefPubMed 3. Barbour L, Ball LG, Zhang K, Xiao W: DNA damage checkpoints are involved in postreplication repair. Genetics 2006, 174: 1789–800.CrossRefPubMed 4. Callegari AJ, Kelly TJ: Shedding light on the DNA damage checkpoint. Cell Cycle 2007, 6: 660–6.PubMed 5.