CD274 and squamous cell carcinoma: In contrast, a high expression of PD-L1 on surface tumor cells is a poor prognostic marker in several tumor types, e.g., squamous cell carcinoma of the head and neck, melanoma, thyroid, thymus, esophagus, lung, breast, gastrointestinal tract, ovary, skin and others [59]; therefore, our results demonstrate that electrochemotherapy with CDDP, OXA and BLM is also a double-edged sword, as increased PD-L1 expression can counteract the positive effects of ICD on the activation of the immune system, by blocking the cytotoxic activity of CD8+ cytotoxic T cells [59,60,61].