Meningiomas are the most common primary tumors in central nervous system. While recent studies have revealed genetic clues to lower grade human meningiomas, the molecular determinants driving the progression and recurrence of anaplastic meningioma, the most malignant subtype with a low prevalence but high morbidity, are still poorly understood. It has been proposed that high recurrence rates of malignant meningiomas are linked to cancer stem cells. Indeed, tumor stem-like cells have been isolated from various meningioma subtypes, but never been obtained from anaplastic meningioma. In this study, we successfully isolated stem-like cells from human anaplastic meningioma. These cells are capable of forming spheres and initiating xenograft tumors that recapitulate anaplastic meningioma phenotypes, and thus could serve as an in vitro model for malignant meningiomas. KLF4, a transcription factor known for its role in stemness maintenance, was identified as one of the most frequently mutated genes in the benign secretory meningioma. Interestingly, we found that KLF4 is downregulated in anaplastic meningioma compared with low-grade meningioma subtypes. By manipulating KLF4 expression in anaplastic meningioma stem-like cells, we demonstrated that KLF4 acts as a tumor suppressor during malignant progression in meningioma, affecting apoptosis, proliferation, invasion, and cell cycle. These results suggest a potential therapeutic value of KLF4 for clinical intervention of anaplastic meningioma.

OBJECTIVE Malignant meningioma is rare and classified as Grade III in the WHO classification of CNS tumors. However, the presence of estrogen receptor (ER) in WHO Grade III meningiomas and its correlation with patients' outcomes are still unclear. In this single-center cohort study, the authors analyzed clinical features, treatment, and prognosis of these malignant tumors in patients with long-term follow-up. METHODS A total of 87 patients who were pathologically diagnosed with WHO Grade III meningiomas between 2003 and 2008 were enrolled in this study and followed for at least 7 years. Clinical information was collected to analyze the factors determining the prognosis. RESULTS Twelve patients with rhabdoid, 12 with papillary, and 63 with anaplastic meningioma were included. The mean progression-free survival (PFS) and overall survival (OS) were 56.2 ± 49.8 months and 68.7 ± 47.4 months, respectively. No significant differences were observed among the 3 histological subtypes in either PFS (p = 0.929) or OS (p = 0.688). Patients who received gross-total resection had a longer PFS (p = 0.001) and OS (p = 0.027) than those who received subtotal resection. Adjuvant radiotherapy was associated with OS (p = 0.034) but not PFS (p = 0.433). Compared with primary meningiomas, patients with recurrent disease had worse PFS (p < 0.001). For patients who had malignant transformations, the prognosis was poorer than for patients without malignant transformations for both PFS (p = 0.002) and OS (p = 0.019). ER-positive patients had a significantly worse prognosis than ER-negative patients regarding both PFS (p = 0.003) and OS (p < 0.001), whereas no association between progesterone receptor and patients' outcomes was observed. Multivariate analysis demonstrated that ER expression was an independent prognostic factor for both PFS (p = 0.008) and OS (p < 0.001). CONCLUSIONS This retrospective study showed that patients with meningioma with ER-positive expression had a much worse prognosis than those with ER weak-positive or ER-negative status. The results demonstrated that ER is an independent prognostic factor for both PFS and OS of patients with WHO Grade III meningioma. The authors also found that more radical resection of the tumor, as well as postoperative radiotherapy, may prolong patients' survival time.

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