We considered our observations in the Stat3 KO mice to be highly relevant, given that constitutively active Stat3 signalling is observed in approximately half of primary breast cancers30 and that mCLCA5 is the murine orthologue of the human putative tumour suppressor hCLCA2, as previously discussed.20 It therefore appeared logical that Stat3 signalling in tumours may have an inhibitory effect upon expression of mCLCA5 and thus we explored this hypothesis in the 4T1 murine syngeneic tumour model, which has previously been reported to exhibit minimal expression of mCLCA5.22 The gene discussed is CLCA2; the disease is neoplasm.