Abstract 6777: Digital Spatial Profiler highlights a T and B cells inflamed tumor microenvironment in brain metastases derived from melanoma vs. non-melanoma solid tumors
Authors: Mendoza-Valderrey Alberto , Kessler Daria M. , Dettmann Ethan , Li Xinmin , Thompson Sierra , Kolker Steven E. , Margolin Kim A. , Ascierto Maria L. 
Published: April 2023

Introduction: Systemic immunotherapies (IO) have recently shown activity in melanoma and non-small cell lung cancer metastatic to the brain, but minimal activity in the treatment of other brain metastases. Further, only a limited percentage of melanoma or lung cancer (MBM/NSCLC)-brain metastasis (BrMs) patients respond to IO. The aim of this study is to explore the differences in the tumor microenvironment (TME) among BrMs from different tumor types including melanoma, NSCLC, breast, and renal cell carcinoma (RCC).

Methods: Formalin-fixed paraffin-embedded (FFPE) tumor from 13 MBM and 43 non-MBM [18 NSCLC-BrMs, 20 breast-BrMs and 5 Renal RCC-BrMs] and primary tissue from 7 melanoma, 4 NSCLC and 3 breast cases were identified. RNA was isolated from tumor regions and subjected to whole gene expression profiling (GEP) by RNA-seq. Microenvironment Cell-Populations counter method estimated the abundance of immune and stromal infiltrated cell subpopulations. Inter- and intra-tumor heterogeneity was evaluated in selected regions of interest using a 59-plex immune related protein panel assessed by GeoMx Digital Spatial Profiling (DSP) technology.

Results: Whole GEP revealed 3650 transcripts differentially expressed between MBM and non-MBM (False Discovery Rate, FDR, ≤0.01). MBM showed increased expression of genes involved in B cell function, cytolytic activity associated with CD8 and NK cells and complement signaling (C1QA/B/C). Conversely, overexpression of genes involved in epithelial signaling, cell adhesion and neurovascular coupling was observed in non MBM vs MBM. Spatial protein profiling revealed in the TME of MBM vs non-MBM, an increased expression (p &lt;0.1, FC&gt;1.5) of the tumor antigen MART-1, together with a higher infiltration of CD8+ cytotoxic cells (CD8+, 41BB+), antigen presenting cells (HLA-DR+, B2M+, CD40+) and cells involved in the formation of tertiary lymphoid structures (CD20+, CD11c+). Conversely, increased infiltration of Tregs (CD25+, CD127+), neutrophils (CD66b+) and epithelial cells (EpCAM+, PanCK+) was observed in non-MBM vs MBM. Interestingly, LAG3+and PD-L2+cells were also observed to be more enriched in non-MBM vs MBM. GEP in primary tumors (FDR≤0.01) showed limited immune-related signals but revealed overexpression of genes associated with NK cells functions and immune chemoattraction (CCL18/20, CXCL2/5/17) to be overexpressed in PM vs other primary tumors.

Conclusion: TME interrogation at molecular and protein levels has shown that MBM are more immune infiltrated than brain metastases derived from non-melanoma solid tumors. Particularly, a cytotoxic and B cells - enriched TME was observed in MBM vs brain metastases derived from NSCLC, breast and RCC. These findings will be validated in larger cohorts and incorporated in therapeutic investigations.

Citation Format: Alberto Mendoza-Valderrey, Daria M. Kessler, Ethan Dettmann, Xinmin Li, Sierra Thompson, Steven E. Kolker, Kim A. Margolin, Maria L. Ascierto. Digital Spatial Profiler highlights a T and B cells inflamed tumor microenvironment in brain metastases derived from melanoma vs. non-melanoma solid tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6777.