TLR9 and neoplasm: The most well-characterized DNA sensor is Toll-like receptor 9 (TLR9), which is found predominantly in the endosomes of immune cells and detects mainly CpG motif DNA and RNA-DNA hybrids.51,52 In contrast, other intracellular DNA sensors are nuclear or cytosolic, are ubiquitous and present in virtually any mammalian cell, including tumour cells, and detect various DNA motifs.17,53