Concurrence of chromosome 6 chromothripsis and glioblastoma metastasis

Molecular profiling of an osseous metastasis in glioblastoma during checkpoint inhibition: potential mechanisms of immune escape

Peripheral metastases of glioblastoma (GBM) are very rare despite the ability of GBM cells to pass through the blood-brain barrier and be disseminated through the peripheral blood. Here, we describe a detailed genetic and immunological characterization of a GBM metastasis in the skeleton, which occurred during anti-PD-1 immune checkpoint therapy. We performed whole genome sequencing (WGS) and 850 K methylation profiling of the primary and recurrent intracranial GBM as well as one of the bone metastases. Copy number alterations (CNA) and mutational profiles were compared to known genomic alterations in the TCGA data base. In addition, immunophenotyping of the peripheral blood was performed. The patient who was primarily diagnosed with IDH-wildtype GBM. After the resection of the first recurrence, progressive intracranial re-growth was again detected, and chemotherapy was replaced by PD-1 checkpoint inhibition, which led to a complete intracranial remission. Two months later MR-imaging revealed multiple osseous lesions. Biopsy confirmed the GBM origin of the skeleton metastases. Immunophenotyping reflected the effective activation of a peripheral T-cell response, with, however, increase of regulatory T cells during disease progression. WGS sequencing demonstrated distinct genomic alterations of the GBM metastasis, with gains along chromosomes 3 and 9 and losses along chromosome 4, 10, and 11. Mutational analysis showed mutations in potentially immunologically relevant regions. Additionally, we correlated tumour-infiltrating lymphocyte and microglia presence to the occurrence of circulating tumour cells (CTCs) in a larger cohort and found a decreased infiltration of cytotoxic T cells in patients positive for CTCs. This study exemplifies that the tumour microenvironment may dictate the response to immune checkpoint therapy. In addition, our study highlights the fact that despite an effective control of intracranial GBM, certain tumour clones have the ability to evade the tumour-specific T-cell response and cause progression even outside of the CNS.

Creutzfeldt astrocytes may be seen in IDH-wildtype glioblastoma and retain expression of DNA repair and chromatin binding proteins

Astrocytes with multiple micronuclei ("Creutzfeldt cells") in a brain biopsy are classically associated with demyelinating disease. However, glioblastoma may also have prominent Creutzfeldt astrocytes, along with granular mitoses. Therefore, Creutzfeldt cells may raise the diagnostic dilemma of high-grade glioma vs tumefactive demyelination. While cases of glioblastoma (GBM) with Creutzfeldt astrocytes have been reported, their clinicopathologic spectrum and genetic features are not understood. Studies have proposed that micronuclei in Creutzfeldt cells are a consequence of DNA damage, or may be susceptible to DNA damage and chromothripsis, but their biology in the context of glioblastoma remains unclear. Based on a challenging index case of GBM with mild hypercellularity, Creutzfeldt astrocytes, and granular mitoses on biopsy, we searched our archives for additional cases with similar histopathologic features. We identified 13 cases, reviewed their clinico-radiologic and pathologic features, and examined them for recurrent genetic alterations via NGS (9 cases) and for evidence of DNA damage by immunohistochemistry for DNA repair and chromatin remodeling proteins. We found that Creutzfeldt cell-rich GBMs were IDH-wildtype with no recurring genetic alterations. To test our hypothesis that micronuclei demonstrate loss of DNA repair or chromatin remodeling proteins, we examined the expression of various proteins (MDM2, p53, MLH1, MSH2, PMS2, MSH6, ATRX, INI1, SATB2, Ki67, pHH3) in Creutzfeldt cell rich-GBM. There was intact expression of DNA repair and chromatin remodeling proteins, with accumulation of p53 and reduced MDM2 expression within micronuclei. In contrast, granular mitoses showed pHH3 expression, confirming these cells are undergoing mitotic division, with no accumulation of p53 and reduced expression of DNA repair proteins. Our results emphasize that Creutzfeldt cells are part of the morphologic spectrum of IDH-wildtype glioblastoma. We did not find a role for DNA damage in the generation of Creutzfeldt cells, as both DNA repair and chromatin remodeling protein expression was retained in these cells.