PDCD1 and basal cell carcinoma: To test EpiTrace in a more complex cell population in an in vivo setting, with possible influx, efflux and proliferation, we applied EpiTrace to an scATAC-seq dataset comprising biopsies from basal cell carcinoma pre-anti-PD1 and post-anti-PD1 treatment (Fig. 5a; GSE129785 (ref. 64)).