To evaluate the efficiency of Chicabuffers in promoting Cas9-mediated genome editing, we designed a gRNA targeting exon 2 of PDCD1 gene, which encodes the inhibitory receptor PD-1, a relevant potential target for cancer cell-based immunotherapy (Hamid et al., 2013; Chicaybam and Bonamino, 2014). Here, PDCD1 is linked to cancer.