ENTPD1 and neoplasm: On the other hand, the lack of CD39 expression was observed in two CD8 TEM subsets, GZMKhigh and GZMBhigh, among which GZMKhigh CD8 TEM phenotype constitutes the most abundant subset with low lytic potential (PRF1, GLNY, GZMB.)Notably, multiple lines of evidence have linked the CD8 TEMGZMKhigh phenotype to tumor progression [53].