Predictive markers of immune checkpoint inhibitor therapy

The past few years brought a dramatic breakthrough of immunotherapeutic modalities in cancer treatment. Advances in understanding the mechanisms regulating antitumor immune response led to development of a new class of immunotherapeutic agents targeting molecular interactions blocking immune activation, the so called immune checkpoint inhibitors (ICIs). These agents release the brakes of activation of T lymphocytes, the main effector cell type involved in antitumor immune reactions. This approach showed unprecedented clinical efficacy in advanced stage cancers, however, generally only a smaller proportion of patients benefit from ICI therapy while serious side effects may occur with a higher frequency. To enhance their efficacy it is of primary importance to search for biomarkers that could help predict the likelihood of therapeutic effect. We propose investigation of local immune parameters in oncological patients treated with ICI therapy, and assess their applicability in predicting treatment response and the outcome of the disease. We plan to analyze tumor samples from patients with metastatic melanoma, head and neck cancer, or breast cancer, and investigate multiple immune cell types and regulatory molecules involved in the development of antitumor immune reactions, and evaluate their associations with response to immunotherapy and patients survival. Our aim is to contribute to understanding of mechanisms that are important in the effect of ICI agents, and to provide easily applicable predictive markers to help in selecting patients most likely to respond to this therapeutic approach. 1

The international project I3976-B33 is a joint international collaboration between the National Institute of Oncology in Budapest, Hungary and the Department of Otorhinolaryngology and Head and Neck Surgery in Innsbruck Austria. This project considers that tumor cells abrogate the tumor-cell-killing-function of the immune system, which blockade is called: immune checkpoint. Antibodies, as immune checkpoint inhibitors (ICI), successfully release this blockade. ICI-therapy is effective, nevertheless, only a smaller proportion of patients benefit from it, the reasons of which are poorly known. The success of the ICI therapy is not predictable. Moreover, ICI-therapies might have serious side effects. This project aimed to find predictive markers for the success of the ICI-therapy. For this approach, the Hungarian partner collected surgical tissue samples from patients with metastatic melanoma who received ICI-therapy. A similar approach is ongoing in head and neck cancer. In melanoma, one major reason for less success of ICI-therapy is the impaired antigen presentation of the tumor cells, which was found in pre-treatment metastases of melanoma patients. Decreased melanoma cell human leukocyte antigen class I expression was found in post-treatment tumors of progressing patients. This finding was published by the two groups together in 2022. A similar conclusion for head and neck cancer is difficult to get, because of the heterogeneity of the tumor tissue, and the limited availability of post-treatment samples. During the project period (2019-2024) a new finding was achieved in head and neck oncology, that tumor cells transdifferentiating to a mesenchymal direction are not only resistant to standard radio- and chemotherapy, but also survive ICI-treatments. The background of this finding revealed that this increased tumor cell survival, in spite of cell killing therapies (to which indirectly the ICI-treatment also belongs to), is related with stress-induced RNA and protein stabilization mechanisms and sustained cell signaling pathways. Moreover, these pathways are pharmacologically targetable. The step-by-step enlightenment of this process, and finally the suggestion for pharmacological treatment are published in 7 project specific papers. The project also provided methodological achievements, which enable the computerized quantification of local protein signals in the histological tissue sample, and grouping the signals to cancer cell nests, disseminating tumor cells, tumor microenvironment and also to normal or inflamed tissue parts. The combined view of multiple molecules and cells investigation in the tissue was utilized and resulted in 6 project specific publications. The collaboration goes on, the complex tumor cell- and immune cell-derived effects on the ICI-treated local tumor tissue is being investigated by organotypic cultures and the identification of the effects of tumor cells and immune cells on ICI therapy is further investigated in tissue sections.