OS05.4.A Single-cell characterization of human GBM reveals regional differences in tumor-infiltrating leukocyte activation

Background

Clinical trials of systemic T cell checkpoint blockade in GBM patients showed only disappointing results. This may be attributed in part to the immunosuppressive components of the GBM immune tumor microenvironment (iTME). Therefore, major efforts have been undertaken to describe the GBM iTME on a single cell level. However, human data on the composition of the iTME in different tumor regions (contrast enhancing tumor center versus peripheral infiltration zone) remain scarce.

Material and Methods

Here, we performed high-depth single-cell RNA sequencing (scRNA-seq) on patient-matched biopsies from tumor center and the peripheral infiltration zone of five primary GBM patients. Additionally, peripheral blood mononuclear cells (PBMC) of the same patients were included in the analysis to explore the transcriptional changes occurring during tumor infiltration of circulating immune cells. Main findings of the transcriptional analysis were confirmed by flow cytometry.

Results

Through analysis of > 45’000 cells, we revealed a distinct regional transcriptional profile of microglia (MG) and monocyte-derived macrophages (MdM), a non-reactive/exhausted MG subcluster in the GBM iTME and an impaired interferon-response signature in the tumor-peripheral cytotoxic cell compartment. Comparing CD8+ T cells from the tumor periphery to PBMC-derived CD8+ T cells of the same patient revealed CX3CR1high and CX3CR1int CD8+ T cells with effector and memory phenotype, respectively, enriched in the PBMC but lacking in the tumor periphery. Tumor peripheral CD8+ T cells shared features with tissue-resident memory CD8+ T cells with exhausted effector functions.

Conclusion

Our analysis provides a large-scale dissection of GBM-associated cell types complemented by patient-matched PBMCs, serving as a high dimensional reference map of the human GBM iTME.

Autotrophic CO(2) fixation by Chloroflexus aurantiacus: study of glyoxylate formation and assimilation via the 3-hydroxypropionate cycle

In the facultative autotrophic organism Chloroflexus aurantiacus, a phototrophic green nonsulfur bacterium, the Calvin cycle does not appear to be operative in autotrophic carbon assimilation. An alternative cyclic pathway, the 3-hydroxypropionate cycle, has been proposed. In this pathway, acetyl coenzyme A (acetyl-CoA) is assumed to be converted to malate, and two CO(2) molecules are thereby fixed. Malyl-CoA is supposed to be cleaved to acetyl-CoA, the starting molecule, and glyoxylate, the carbon fixation product. Malyl-CoA cleavage is shown here to be catalyzed by malyl-CoA lyase; this enzyme activity is induced severalfold in autotrophically grown cells. Malate is converted to malyl-CoA via an inducible CoA transferase with succinyl-CoA as a CoA donor. Some enzyme activities involved in the conversion of malonyl-CoA via 3-hydroxypropionate to propionyl-CoA are also induced under autotrophic growth conditions. So far, no clue as to the first step in glyoxylate assimilation has been obtained. One possibility for the assimilation of glyoxylate involves the conversion of glyoxylate to glycine and the subsequent assimilation of glycine. However, such a pathway does not occur, as shown by labeling of whole cells with [1,2-(13)C(2)]glycine. Glycine carbon was incorporated only into glycine, serine, and compounds that contained C(1) units derived therefrom and not into other cell compounds.

Phenotypic characterization of androgen receptor-related proliferation in prostatic-carcinoma derived cell-cultures

Our study reviews the central role of androgens for the development of androgen-insensitive growth in prostatic carcinoma using an individual dynamic model which emulates aspects of proliferation control. Our aim is the identification of individually proliferating cells from prostate carcinoma. Short-term cultured cells (n=205) from radical prostatectomy specimens have been used as the major method to skew the correspondence between the androgen-receptor (AR), proliferation-markers (Ki-67, PCNA) and morphological landmarks (nucleoli, AgNOR). These techniques allowed the identification of distinct androgen-insensitive, proliferating cell-clusters and in the future will allow the analysis of genotypic changes in identified proliferating cell clones.