 It is possible that cancer and TLR9 have a feed-forward relationship, where the occurrence of one leads to the up-regulation of the other.Many viruses take advantage of this relationship by inducing certain TLR9 expression patterns to first infect the cell (down-regulate) then trigger the onset of cancer (up-regulate).Human papilloma virus is a common and widespread disease that, if left untreated, can lead to epithelial lesions and cervical cancer.