Article
Intratumoral heterogeneity of tumour associated macrophages in glioblastoma multiforme
Intratumorale Heterogenität Tumor-assoziierter Makrophagen im Glioblastoma multiforme
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Published: | June 4, 2021 |
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Objective: Previous work of our group did assess the PSGL-1 expression on tumour associated macrophages (TAM) by FACS and Immunohistochemistry (IHC). The FACS and IHC results did not correlate with each other, but we noticed that the samples for both methods came from distinct regions in the tumour (sample for pathology and sample for research). The present study aimed to investigate the intratumoral heterogeneity of TAM in GBM with a special focus on PSGL-1 expression.
Methods: Tumour samples of n=11 GBM patients at initial diagnosis were gathered under neuronavigational guidance from up to 6 different defined regions per tumour of the contrast-enhancing tumour margin. Samples were snap-frozen immediately. Overall 12 antigens were investigated with their immunofluorescence staining utilizing the Operetta CLS high content imager followed by algorithm-driven quantification with the Harmony 4.9 analysis software. Overall expression intensity (Foldchange (FC): MFI to MFI of the negative control) was quantified. Also, the heterogeneity of expression (Score = 0 − (1/(x<1)) × 100) in between different regions of one tumour was quantified.
Results: As expected, GFAP as tumour cell marker showed up with the highest expression level across all patients and sample locations (mean FC 6.9, range from 2.1 to 19.9). A medium expression level (mean FC from 2 to 3.1) was shown for CCR7, CD204, Arg1, iNOS, CD163, CD206 and CSFR1. MHCII, CD16, CD68 and PSGL1 (mean FC = 1.2 to 1.5) were among the low abundant antigens. Interestingly, those low abundant antigens showed up with the highest score in the assessment of the intra-tumoral heterogeneity (Score 7.5 to 10). The lowest intra-tumoral heterogeneity has been seen in GFAP expression (Score 5.5).
Conclusion: The present study reveals a tremendous intratumoral heterogeneity of common surface expression marker of TAM in GBM. Especially low abundant antigens as PSGL-1 have a high intra-tumoral heterogeneity. That shows that immunological studies using one sample per tumour are rather limited in their significance.