Furthermore, PD-1+/CD8+ T cells co-expressing both nPKC-θ and ZEB1 represented 80.0% of the total CD8+ T-cell population in breast cancer brain cancer metastases compared to 54.7% in primary breast metastases, suggesting that nPKC-θ may interact with ZEB1 as part of an exhaustion signature important for tumor progression and metastasis (Figure 6F). Here, ZEB1 is linked to breast cancer.