SHMT2 and neoplasm: To test whether loss of the mitochondrial folate cycle impairs tumour formation in vivo, KCL22 SHMT2 KO cells were transplanted via tail vain injection into non-irradiated NRGW (NOD.Cg-Rag1tm1MomKitW-41JIl2rgtm1Wjl)41 mice.