In addition, we found that higher CTLA-4 expression in CTCs was weakly correlated with those cancers with the KRAS mutant (p = 0.06) (Figure 4B), while in PBMCs, CTLA-4 was more likely have higher expression in patients detected with high CTC counts (64% vs. 93%, p = 0.046) and with lymph node metastasis (65% vs. 100%, p = 0.006) (Table 3). Here, CTLA4 is linked to cancer.