Mismatch repair deficiency drives malignant progression and alters the tumor immune microenvironment in glioblastoma models
Montserrat Puigdelloses Vallcorba, Nishant Soni, Seung-Won Choi, Kavita Rawat, Tanvi Joshi, Sam Friedman, Alice Buonfiglioli, Angelo Angione, Zhihong Chen, Gonzalo Piñero, Gabrielle Price, Mehek Dedhia, Raina Roche, Emir Radkevich, Anne M. Bowcock, Deepti Bhatt, Winfried Edelmann, Robert M. Samstein, Timothy E. Richardson, Nadejda M. Tsankova, Alexander M. Tsankov, Ranjit S. Bindra, Raul Rabadan, Juan C. Vasquez, Dolores Hambardzumyan
Montserrat Puigdelloses Vallcorba, Nishant Soni, Seung-Won Choi, Kavita Rawat, Tanvi Joshi, Sam Friedman, Alice Buonfiglioli, Angelo Angione, Zhihong Chen, Gonzalo Piñero, Gabrielle Price, Mehek Dedhia, Raina Roche, Emir Radkevich, Anne M. Bowcock, Deepti Bhatt, Winfried Edelmann, Robert M. Samstein, Timothy E. Richardson, Nadejda M. Tsankova, Alexander M. Tsankov, Ranjit S. Bindra, Raul Rabadan, Juan C. Vasquez, Dolores Hambardzumyan
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Research Article Cell biology Immunology Neuroscience Oncology

Mismatch repair deficiency drives malignant progression and alters the tumor immune microenvironment in glioblastoma models

Abstract

Mutations in DNA mismatch repair (MMR) pathway genes (MSH2, MSH6, MLH1, and PMS2) are linked to acquired resistance to temozolomide (TMZ) and high tumor mutation burden (TMB) in high-grade gliomas (HGGs), including glioblastomas (GBMs). However, the specific roles of individual MMR genes in the initiation, progression, TMB, microsatellite instability (MSI), and resistance to TMZ in gliomas remain unclear. Here, we developed de novo mouse models of germline and somatic MMR-deficient (MMRd) HGGs. Surprisingly, loss of Msh2 or Msh6 did not lead to high TMB, MSI, nor did it confer a response to anti–programmed cell death 1 (anti–PD-1) in GBM. Similarly, human GBM showed discordance between MMR gene mutations and the TMB and MSI. Germline MMRd promoted the progression from low-grade to HGG and reduced survival compared with MMR-proficient (MMRp) tumor–bearing mice. This effect was not tumor cell intrinsic but was associated with MMRd in the tumor immune microenvironment, driving immunosuppressive myeloid programs, reduced lymphoid infiltration, and CD8+ T cell exhaustion. Both MMR-reduced (MMRr) and MMRd GBM were resistant to TMZ, unlike MMRp tumors. Our study shows that N3-(2-fluoroethyl) imidazotetrazine (KL-50), an imidazotetrazine-based DNA targeting agent that induces MMR-independent cross-link–mediated cytotoxicity, was effective against germline and somatic MMRr and MMRd GBMs, offering a potential therapy for TMZ-resistant HGG with MMR alterations.

Authors

Montserrat Puigdelloses Vallcorba, Nishant Soni, Seung-Won Choi, Kavita Rawat, Tanvi Joshi, Sam Friedman, Alice Buonfiglioli, Angelo Angione, Zhihong Chen, Gonzalo Piñero, Gabrielle Price, Mehek Dedhia, Raina Roche, Emir Radkevich, Anne M. Bowcock, Deepti Bhatt, Winfried Edelmann, Robert M. Samstein, Timothy E. Richardson, Nadejda M. Tsankova, Alexander M. Tsankov, Ranjit S. Bindra, Raul Rabadan, Juan C. Vasquez, Dolores Hambardzumyan

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Figure 4

Disease-associated myeloid cell subsets are increased in Msh2-dependent MMRr and MMRd tumors.

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Disease-associated myeloid cell subsets are increased in Msh2-dependent ...
(A) UMAP plot of all sequenced mGBM myeloid cells, colored by annotated myeloid cell subset. (B) Stacked bar plots depicting the proportion of annotated myeloid cell subsets. (C) Plots of t-distributed stochastic neighbor embedding (t-SNE) showing the results of spectral flow cytometry of the myeloid cell panel in tumors (top) and heatmaps representing quantification (bottom). (D) UMAP plot of all mGBM microglia cells from the scRNA-seq dataset colored by annotated microglia subsets, and distribution of microglia subset proportions, split by Msh2 status. Black = WT, blue = Msh2 heterozygous, and red = Msh2-KO. (E) Left: UMAP plot of all mGBM monocytes colored by annotated monocytes subsets. Right: Distribution of monocyte subset proportions, split by Msh2 status. (F) Left: UMAP plot of all mGBM MDMs colored by annotated MDM subsets. Right: Distribution of MDM subset proportions, split by Msh2 status. (G) Dot plot showing expression levels and the percentage of cells expressing the Cd274 gene for each annotated myeloid cell subset according to Msh2 status. (H) Schematic illustration of flow cytometry and heatmap quantification of PD-L1 expression in different myeloid cell populations according to Msh2 status. *P < 0.05 and **P < 0.01, unpaired t test (C) and 1-way ANOVA followed by Tukey’s post hoc analysis (H). (D–F) Box plots display the median (central line), interquartile range (box), and whiskers extending to the smallest and largest values within 1.5 times the interquartile range. Individual data points are shown as dots to provide a detailed view of the sample distribution). Panel H includes an illustration created with BioRender.