Replacement of the radiosensitive haematopoietic compartment with TLR-2/-4−/− or TLR-9−/− cells did not affect tumour formation (Fig. 3c), in contrast to the role of TLR-4 on haematopoietic and non-haematopoietic cells in chemically induced skin carcinogenesis23. Here, TLR9 is linked to neoplasm.