CEACAM1 and neoplasm: CEACAM1 and PD-L1 levels were increased in the treatment-naive and -resistant tumor samples relative to that observed in PBMC (Fig. 5c, e); the levels of PD1 expression were also increased in the tumor-associated PBMC, although not significantly (Fig. 5d), as was CEACAM1 (Fig. 5c).