We found that the frequency of PD-1+ cells among antigen-experienced CD8+ T cells did not correlate with the number of metastases when either wild-type or Arhgef1-deficient mice were analysed, suggesting that reduced PD-1 expression was unlikely to be the consequence of decreased tumour burden in the lungs of Arhgef1-deficient mice (Extended Data Fig. 4d). The gene discussed is ARHGEF1; the disease is neoplasm.