P06.08.B Radiation therapy enhances anti-tumor activity of a MET CAR T-based immunotherapy for glioblastoma

Background

Glioblastoma is the most frequent primary brain tumor with dismal prognosis after standard treatment with surgery, and chemoradiation (the Stupp protocol). After a decade of failed clinical trials, tumor-treating fields have been first to show the added benefit of improved overall survival compared to the Stupp protocol (20.9 months vs 16.0 months). However, GBM remains a devastating disease, with almost inevitable recurrence, and limited options for second-line therapy. Radiation therapy (RT), is a standard therapy option for GBM, and it is used in most GBM cases affecting tumor through induction of DNA-damage. Recently, RT has been investigated as a mediator of T cell-based therapies in the context of immunosuppressive GBM microenvironment. The findings have shown promise in combination of T cell-based therapies, such as chimeric antigen receptor (CAR) T cell therapies, in improving the tumor infiltration, and penetration with immune cells. MET is a relevant oncogene in the context of GBM, being involved in stem-like properties, radiation response and resistance․ Hence, MET appeared to be a plausible target for combination with RT. In our research, we use MET-targeting CAR T cells (MET-CAR T cells) combined with radiation, and hypothesize synergistic interaction for GBM treatment.

Material and Methods

We used adherent (2D) and stem-like (3D) human GBM cell lines with different levels of MET expression. For MET-CAR T cell generation we did retrovirus-mediated transduction of activated human T cells and sorted the CAR-positive cells. We co-cultured MET-CAR T cells with GBM cells with or without RT, and assessed the killing and cytokine production in CAR T cells.

Results

Our results indicated that 5Gy radiation combined with MET-CAR T cells increases their potential in tumor cell killing. We observed increased CAR T cells effect at lower CAR T to target cells ratios when combined with radiation, even when radiation treatment did not lead to a significant decrease in viability. This phenomenon was similar across different types of cell lines (adherent, stem-like), different levels of MET expression, and different sensitivity to CAR T cells. We investigated the underlying mechanisms via intracellular cytokine measurement. We observed the most prominent response in TNF-α-expression. We also observed an increase in Granzyme B expression in co-culture with some of the GBM cell lines, especially in CD8+ subpopulation of CAR T cells. IFN-gamma expression increased in some adherent glioma cell lines but not in stem-like cell lines.

Conclusion

In conclusion, our data demonstrates the potency of MET-CAR T cells against GBM, and increased efficiency when combined with radiation. The suggested mechanism is the increased activation of T cells in TNF-α-dependent-manner. To validate these results we are testing our setup in an orthotopic mouse GBM model.

Abstract PO-039: Radiation therapy enhances anti-tumor activity of a MET CAR T-based immunotherapy approach for glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most prevalent primary malignant brain tumor, which has an aggressive phenotype and mostly fatal recurrence after standard therapy. MET, the hepatocyte growth factor (HGF) receptor is a relevant target for GBM treatment as it is expressed in up to 50% of cases and its expression, which may be induced by radiation therapy (RT), can potentially contribute to RT-resistance of GBM stem cells, and tumor recurrence. MET-based chimeric antigen (CAR) T cell therapy is currently being evaluated in several solid tumor working settings. A combination of T cell-based therapies with RT may improve the efficacy of the CAR T cell therapy through by the RT-induced immune activation via release of cytokines and induction of antigen expression, similarly as has been observed when combining RT with immune checkpoint inhibitors. Here we investigated the combination of MET-targeting CAR T cells with RT for GBM treatment, hypothesizing enhanced anti-tumor effects. The current study used a panel of MET-proficient and MET-deficient human GBM and GBM stem-like cell lines. Cells have been irradiated with a single dose of 0, 2, 5, or 10 Gy and RT impact on MET expression has been assessed at various time points after RT administration. Results show MET increase after RT in some cell lines. To test MET-targeting CAR T effect on the GBM cell lines, CAR constructs that are based on HGF-MET binding elements have been introduced into virus-producing cells and used for human T cells transduction to generate MET-targeting CAR T cells. CAR T cells co-cultured with GBM cell lines in vitro have specifically and significantly decreased viability of MET-positive cancer cells. Data resulting from combination of RT and CAR T cells treatment suggest that radiation exhibits an enhancement of CAR T cells anti-tumor killing activity, indicating a synergism between the two modalities. In conclusion, our data are the first to indicate the efficacy of a MET-based CAR T immunotherapy approach in GBM cell lines. The results also demonstrate a basis for the combination of a MET CAR T modality together with RT. The mechanisms for understanding the interaction between RT and the MET CAR T cells are under investigation.

Citation Format: Lusine Hovhannisyan, Daniel M. Aebersold, John Maher, Adrian F. Ochsenbein, Carsten Riether, Michaela Medova, Yitzhak Zimmer. Radiation therapy enhances anti-tumor activity of a MET CAR T-based immunotherapy approach for glioblastoma multiforme [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-039.

Abstract A20: The DNA damage-induced phosphoproteome is modulated by inhibition of the MET receptor

Ionizing radiation (IR) is frequently used in the treatment of a variety of malignant tumors of different origins and stages. In recent years, numerous studies have demonstrated that interfering with signaling via growth factor receptor tyrosine kinases (RTKs) can increase the sensitivity of certain tumors to IR. The RTK for hepatocyte growth factor MET is aberrantly activated in numerous types of human malignancies. MET inhibition has been shown to synergize with DNA damaging agents in generation of DNA damage and to interfere with damage repair. In this study, we aimed to explore how the cellular response to ionizing radiation is modulated by MET inhibition.

We have conducted an immunoaffinity-based LC-MS/MS phosphoproteomics survey study to explore the cellular phosphoproteome following exposure of MET-addicted cancer cells to MET inhibition alone and in combination with IR. Phosphorylation sites of interest have been examined using selected reaction monitoring (SRM) and further validated in vitro and in vivo by Western blotting and immunohistochemistry, respectively.

Analysis of the survey data has identified more than 300 phosphopeptides which have changed in one experimental condition or more. Several of these phosphorylation changes have been confirmed and further investigated by targeted proteomics. These results have pointed to a sub-network of the DNA damage response (DDR) that is modulated in MET-addicted cancer cells upon DNA damage and MET inhibition. The resulting molecular signature present solely in MET-addicted systems could be responsible for the synergism observed between MET inhibition and DNA-damaging agents. We believe that these results will aid in understanding as how MET signaling crosstalks with the DDR with subsequent translational therapeutic clinical applications.

Citation Format: Ariel Bensimon, Yitzhak Zimmer, Paola Francica, Jonas P. Koch, Astrid A. Glück, Daniel M. Aebersold, Ruedi Aebersold, Michaela Medova. The DNA damage-induced phosphoproteome is modulated by inhibition of the MET receptor. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr A20.