2250 - Interferon Signaling Underlies Radiotherapy Responses in Malignant Peripheral Nerve Sheath Tumors (MPNSTs)

02:30pm - 04:00pm PT

Hall F

Screen: 33

POSTER

Presenter(s)

Harish Vasudevan, MD, PhD - University of California San Francisco, SAN FRANCISCO, CA

I. Zhu¹, K. Mirchia¹, S. Pan², K. Miller¹, J. Pak¹, R. L. Wustrack¹, V. Monga³, L. Jacques⁴, S. E. Braunstein⁵, M. Pekmezci⁶, S. J. Liu², and H. Vasudevan⁵; ¹University of California, San Francisco, San Francisco, CA, ²UCSF, San Francisco, CA, ³Division of Hematology, Oncology, and Blood & Marrow Transplantation, Department of Internal Medicine, Holden Comprehensive Cancer Center, The University of Iowa, Iowa City, IA, ⁴University of California San Francisco, SAN FRANCISCO, CA, ⁵Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, ⁶University of California San Francisco, Department of Pathology, San Francisco, CA

Purpose/Objective(s):

Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas with poor clinical outcomes despite multimodal treatment with surgery, systemic therapy, and radiation therapy (RT). Our objective was to identify genomic and cellular mediators of MPNST RT response. Given the benefits of combining immune checkpoint blockade with radiation for undifferentiated sarcomas, we hypothesized both tumor cell autonomous factors and their interaction with the immune microenvironment underlie MPNST RT response.

Materials/Methods:

Patient derived plexiform neurofibroma (pNF) and MPNST cells were analyzed for radiation responses by CellTrace Yellow staining (Thermo Fisher), cell counts, and clonogenic assays. Bulk RNA-sequencing of irradiated cell lines in vitro was performed to analyze transcriptomic responses. A genome-wide CRISPRi screen in human MPNST cells was performed to identify genetic modifiers of RT response. A murine MPNST immunocompetent allograft model was used to study RT responses in vivo. Single cell RNA-sequencing (scRNA-seq) of murine MPNSTs in irradiated and control untreated tumors was performed using the 10x Genomics platform. Flow cytometry was performed using a Becton Dickinson (BD) FACS Aria Fusion. Methylation array profiling of 30 human MPNST patient samples who received RT with detailed clinical follow up was analyzed to identify factors associated with clinical RT response.

Results:

MPNSTs demonstrated radioresistance compared to pNFs and induce a unique tumor cell autonomous type I interferon signature not observed in pNFs. Consistently, our genome wide CRISPRi screen converged on a type I interferon circuit including genes such as TMEM173 encoding STING, IRF3, and STAT1 that functionally underlies MPNST radioresistance in vitro. ScRNA-seq of 32,763 cells from irradiated and control untreated immunocompetent mouse MPNST allografts showed radiation drives interferon mediated T-cell recruitment and activation through both tumor cells and the macrophage compartment in vivo. Immunomethylomic deconvolution of human MPNST resection specimens demonstrates increased microenvironmental and CD8+ T-cell infiltration are associated with significantly improved local control following RT while chromosome 9p loss, which harbors a type I interferon gene cluster, is associated with significantly worse radiotherapy response and decreased CD8+ T-cell infiltration.

Conclusion:

Our results provide preclinical rationale for combining immunomodulatory agents designed to stimulate interferon secretion as a rational approach to improve radiation responses in MPNSTs, which may be broadly applicable to other soft tissue sarcomas. Future work more precisely refining the cellular subpopulation, regulators, and effectors of type I interferons as well as approaches to selectively modulate key signaling nodes within this network will be critical to design better tolerated therapies leveraging these immunologic circuits.