gms | German Medical Science

Objective: Pluripotent cells do not only play an essential role in developmental biology but also in carcinogenesis and malignancy of tumors. These cells represent a special subgroup or state of cancer stem cells. Pluripotent cells are able to form every other cell type and are characterized by specific expression profiles of the key transcription factors NANOG, Sox2 and OCT4. In the past we identified cells incorporating NANOG even in human meningiomas. With this study we want to establish a suitable in vitro model for a stable isolation and cultivation of potential tumor stem cells and compare them with induced pluripotent cells (iPCs) from non-pathological and pathological meningeal cells.

Methods: Potential meningioma stem cells (PMSC) were isolated from 50 specimens of individual patients (WHO °I: n=37, WHO °II: n=11, WHO °III: n=2) and characterized by various physiological parameters, immunocytochemistry (Vimentin, Nestin, EMA, Ki67, Nanog, Oct4, Sox2, CD44, Musashi-1) and qPCR (NANOG, OCT4, SOX2, MIB1, MSI1, CD44). iPCs of primary dura cell cultures (n=1), primary meningioma cell cultures (n=2) and immortalized meningioma cell lines (n=2) were generated by mRNA transfection. Of these mRNA level of NANOG, SOX2, OCT4, KLF4, CMYC as direct regulators of pluripotency, MSI1 and CD44 as stem cell markers were measured in iPCs and meningioma stem cells qPCR, too. Pearson correlation analysis was performed for statistical evaluation.

Results: We could isolate stable PMSC from 39 samples (78%). In addition, we found a significant higher median relative protein expression for Nanog (7.5% vs 0.0%; p=0.037) and lower for Vimentin (100% vs. 85%; p=0.002), and Oct4 (30 vs. 5%, p=0.026) in the isolated PMSC compared to the corresponding differentiated primary cell cultures. We detected significantly higher relative mRNA levels (x fold to mean expression) for NANOG (1.55 vs 0.44, p=0.001), MIB1 (0.66 vs. 1.15, p=0.022) and MSI1 (1.77 vs. 0.26, p=0.000) compared to the primary cell cultures. All transfected cell cultures showed morphological changes towards an iPCs typical phenotype. We found high similarities in expression changes of NANOG (4.2 to 5.7) and OCT4 (1.7 to 1.5) between the isolated and the reprogrammed group. We established a positive correlation of isolated cells with iPCs over all genes (r=0.756, p=0.019).

Conclusion: From human meningiomas we could reproducibly isolate cells highly expressing markers for stem cells as well as features of pluripotency. In addition we were able to reprogram pathological and non-pathological meningeal cells into iPCs. The specific gene expression for pluripotency of these iPCs and of isolated meningioma stem cells showed significant correlations. In summary, the isolated meningioma stem cells expressed a high number of pluripotency-regulating genes and can therefore be identified as potential pluripotent meningioma stem cells (PPMSCs).