Diffuse midline glioma with H3-K27M mutation: A rare case with GFAP-positive anucleate whorled patterns

H3 K27-altered diffuse midline glioma of the thalamus with formation of glio-fibrillary globular structures

A case of diffuse midline glioma (DMG), H3 K27-altered, that arose in the right thalamus of a 14-year-old boy is reported. The patient died of tumor spread after a progressive clinical course of approximately 13 months. Histopathologically, the tumor consisted of a mixture of loose proliferation of stellate cells and compact fascicular growth of spindle cells showing a "piloid" feature. Aggregates of globular structures composed of entangled fine glial fibrils ("glio-fibrillary globules, GFGs") were observed. Tumor cells were immunoreactive for S-100 protein and glial fibrillary acidic protein (GFAP), and showed nuclear immunoreactivity for histone H3 K27M and loss of expression of H3 K27me3. Tumor cell nuclei were also negative for alpha-thalassemia/mental retardation syndrome X-linked protein (ATRX) and p16. Although GFGs morphologically resembled "neuropil-like islands" or "neurocytic rosettes" seen in glial or glio-neuronal tumors, they showed immunoreactivity for GFAP, but not for synaptophysin. A GFG is a unique structure that has been described in DMG, H3 K27-altered, by a few investigators. To the best of our knowledge, this structure has not previously been reported in other glial or glio-neuronal tumors. It could be added as a new feature in the histopathological variations of DMG, extending its morphological spectrum. Familiarity with this feature can help prevent misdiagnosis of DMG.

Exosomes Derived from Hypoxic Glioma Cells Reduce the Sensitivity of Glioma Cells to Temozolomide Through Carrying miR-106a-5p

Background

Hypoxia is a frequent feature of solid tumors which significantly affects the efficacy of treatments such as chemotherapy. In addition, exosomes from hypoxic cancer cells could contribute to the chemoresistance of tumor cells through carrying miRNAs. It has been shown that miR-106-5p level was upregulated in glioma. However, whether exosomes derived from hypoxic glioma cells could affect temozolomide (TMZ) resistance in glioma through carrying miR-106a-5p remains unexplored.

Methods

Exosomes were isolated from glioma cells under normoxia or hypoxia condition. EdU staining and flow cytometry assays were used to assess the cell proliferation and cell apoptosis. The relation between miR-106a-5p and PTEN was investigated by dual luciferase assay.

Results

MiR-106a-5p was enriched in exosomes derived from hypoxic glioma cells compared to exosomes from cells under normoxia condition. Additionally, hypoxic glioma cells were able to transfer exosomes to glioma cells, resulting in a significant increase of miR-106a-5p level in cells. TMZ remarkably suppressed glioma cell proliferation and triggered cell apoptosis. However, hypoxic glioma cell-derived exosomes markedly promoted the proliferation and suppressed the apoptosis in TMZ-treated glioma cells, and miR-106a-5p inhibitor was able to abolish these phenomena. Meanwhile, PTEN was verified to be a direct target of miR-106a-5p. Furthermore, TMZ elevated PTEN and Bax level and reduced p-Akt level in glioma cells, whereas these changes were reversed by hypoxia glioma cell-derived exosomes. Furthermore, hypoxia glioma cell-derived exosomes reduced the sensitivity of glioma cells to TMZ in vivo via downregulating PTEN.

Conclusion

Collectively, exosomal miR-106a-5p derived from hypoxia glioma cells could reduce the sensitivity of glioma cells to TMZ through downregulating PTEN. Thus, our study might provide new strategies for improving the clinical efficacy of TMZ on glioma.