Re-transfer experiments (Extended Data Fig. 9e,f) confirmed that EP2/EP4-deficient TIM-3−(TCF1+) OT-I TILs but not their TIM-3+(TCF1−) descendants possessed the capacity to expand in tumours (Extended Data Fig. 9g,h) and were able to give rise to TIM-3+CXCR6+ TILs (Extended Data Fig. 9i). Here, PTGER2 is linked to neoplasm.