Conclusion
We hypothesise that lack of PD-L1-mediated immunosuppression in the TIME may allow efficient immune control following adoptive T-cell therapy. Future studies combining anti-PD-L1 or genetically modified T cells with PD-1 receptor knockdown could be considered to improve clinical responses in patients who have high PD-L1 expression in their tumors.
Methods
Multiplexed immunohistochemical analysis of CD3, PD-L1 and Sox-2 in GBM tissue biopsies obtained before autologous T-cell therapy was carried out and correlated with long-term survival of GBM patients adoptively treated with T-cell therapy.
Results
Tumor microenvironment analyses revealed that the pre-treatment cellular composition of the tumor tissue may influence the subsequent response to adoptive T-cell therapy. GBM patients who showed prolonged overall survival following T-cell therapy had a significantly lower number of tumor-infiltrating CD3+ T cells in recurrent tumors than that in patients with short-term survival. Furthermore, long-term surviving patients showed low or undetectable PD-L1 expression in tumor cells in recurrent GBM biopsies.