According to recent published studies, bacterial DNA activates DNA sensing receptors, possibly due to the frequency of unmethylated CpG sequences in bacterial genome, which is 20 fold higher than in vertebrates’ genome.[35] From further studies it was clear that DNA from pathogenic bacteria upregulate TLR9 expression [15], In the present study we have examined the gene expression changes induced by DNA of tumor origin in cancer cells, by whole genome array. The gene discussed is TLR9; the disease is cancer.