Exploring the regulation of co-inhibitory (PD-1, PD-L1, CTLA-4) and co-stimulatory (CD28) genes by chemotherapeutic drugs is important for combined immune checkpoint blockade (ICB) therapy. ICB interferes with T-cell receptor and major histocompatibility complex (MHC) signaling by antibody drugs directed against the co-inhibitors. Here, we analyzed urothelial (T24) cell line with respect to cytokine signaling by interferon γ (IFNG) and the leukemia lymphocyte (Jurkat) cell line with respect to T-cell activation as mimicked by phorbolester and calcium ionophore (pma/iono). Alongside, we considered possible intervention with the chemotherapeutics gemcitabine, cisplatin and vinflunine. Noteworthy, cisplatin significantly induced PD-L1-mRNA in naïve and IFNG treated cells whereas gemcitabine and vinflunine had no effect on PD-L1-mRNA. At the protein level, PD-L1 showed typical induction in IFNG treated cells. In Jurkat cells, cisplatin significantly induced PD-1-mRNA and PD-L1-mRNA. Pma/iono administration did not alter PD-1-mRNA and PD-L1-mRNA but significantly increased CTLA-4-mRNA and CD28-mRNA levels where vinflunine suppressed the CD28-mRNA induction. In sum, we demonstrated that certain cytostatic drugs being relevant for the therapy of urothelial cancer, affect co-inhibitory and co-stimulatory modulators of immune signaling with potential impact for perspective combined ICB therapy of patients.MHC-TCR signaling between antigen presenting cells and T-lymphocytes with co-stimulator (blue) and co-inhibitors (red) and interacting proteins (blank). Co-inhibitory connections are shown by lines and co-stimulatory connections by dotted lines. The inducible or suppressive actions of the drugs (underlined) on the respective targets are indicated.