Is there effective systemic therapy for recurrent surgery- and radiation-refractory meningioma?

Drug target therapy and emerging clinical relevance of exosomes in meningeal tumors

Meningioma is the most common central nervous system (CNS) tumor. In recent decades, several efforts have been made to eradicate this disease. Surgery and radiotherapy remain the standard treatment options for these tumors. Drug therapy comes to play its role when both surgery and radiotherapy fail to treat the tumor. This mostly happens when the tumors are close to vital brain structures and are nonbenign. Although a wide variety of chemotherapeutic drugs and molecular targeted drugs such as tyrosine kinase inhibitors, alkylating agents, endocrine drugs, interferon, and targeted molecular pathway inhibitors have been studied, the roles of numerous drugs remain unexplored. Recent interest is growing toward studying and engineering exosomes for the treatment of different types of cancer including meningioma. The latest studies have shown the involvement of exosomes in the theragnostic of various cancers such as the lung and pancreas in the form of biomarkers, drug delivery vehicles, and vaccines. Proper attention to this new emerging technology can be a boon in finding the consistent treatment of meningioma.

Metformin enhances anti-cancer effects of cisplatin in meningioma through AMPK-mTOR signaling pathways

Cisplatin is currently used to treat inoperable recurrent meningiomas, but its side effects and drug resistance limit its use. Metformin has recently been identified as a chemosensitizing agent. However, the combined treatment of cisplatin and metformin in high-grade meningiomas has not been reported. Herein, our findings demonstrate metformin significantly enhanced cisplatin-induced inhibition of proliferation in meningioma cells, which was associated with the induction of G0/G1 cell cycle arrest. Additionally, metformin activated adenosine monophosphate activated protein kinase (AMPK) and repressed the mammalian target of rapamycin (mTOR) signaling pathways via an AMPK-dependent mechanism. Furthermore, our xenograft murine model confirmed that metformin enhanced cisplatin’s anti-cancer effect by upregulation of AMPK and downregulation of mTOR signaling pathways. In addition, in 63 patients with atypical meningiomas, the activation of AMPK was significantly associated with tumor recurrence and short disease-free survival (DFS). These results demonstrate metformin enhanced the anti-cancer effect of cisplatin in meningioma in vitro and in vivo, an effect mediated through the activation of AMPK and repression of mTOR signaling pathways. Our study suggests the combined treatment of metformin and cisplatin is an effective and safe treatment for high-grade meningiomas.

Predictors of Treatment Response and Survival Outcomes in Meningioma Recurrence with Atypical or Anaplastic Histology

BACKGROUND

Recurrence rates for atypical and anaplastic meningiomas range between 9% and 50% after gross total resection and between 36% and 83% after subtotal resection. Optimal treatment of recurrent meningiomas exhibiting atypical/anaplastic histology is complicated because they are often refractory to both surgery and radiation.

OBJECTIVE

To evaluate clinical determinants of recurrence and treatment-specific outcomes in patients with recurrent meningiomas exhibiting atypical/anaplastic histology at our institution.

METHODS

A cohort study was conducted using clinical data of all patients treated for meningiomas with atypical/anaplastic histology at first recurrence between January 1985 and July 2014 at a tertiary cancer center. Predictors of second recurrence were analyzed using competing risks regression models.

RESULTS

Nine hundred eighteen patients with meningioma were screened, of whom 60 (55% female) had recurrent disease with atypical/anaplastic histology at a median age of 58.1 yr at diagnosis. The median follow-up from the time of first recurrence was 36.7 mo, with 32 (53%) patients alive at last follow-up. There was no effect of extent of resection at first recurrence on time to a subsequent recurrence. Inclusion of radiation as primary or adjuvant therapy at first recurrence reduced the risk of progression or subsequent recurrence compared to surgery alone (P = .07).

CONCLUSION

Treatment of recurrent meningiomas with atypical/anaplastic histology remains challenging. Our data, from one of the largest cohorts, suggest better tumor control with the addition of radiation and challenges the importance of extent of resection at first recurrence. A multicenter effort is needed to confirm these findings and propose treatment guidelines.

Antitumor activity of gemcitabine against high-grade meningioma in vitro and in vivo

Currently, there is no established therapeutic option for high-grade meningioma recurring after surgery and radiotherapy, and few chemotherapeutic agents are in development for the treatment of high-grade meningioma. Here in this study, we screened a panel of chemotherapeutic agents for their possible antitumor activity in high-grade meningioma and discovered that high-grade meningioma cells show a preferential sensitivity to antimetabolites, in particular, to gemcitabine. In vitro, gemcitabine inhibited the growth of high-grade meningioma cells effectively by inducing S-phase arrest and apoptotic cell death. In vivo, systemic gemcitabine chemotherapy suppressed not only tumor initiation but also inhibited the growth and achieved a long-term control of established tumors in xenograft models of high-grade meningioma. Histological analysis indicated that systemic gemcitabine blocks cell cycle progression and promotes apoptotic cell death in tumor cells in vivo. Together, our data demonstrate that gemcitabine exerts potent antitumor activity against high-grade meningioma through cytostatic and cytotoxic mechanisms. We therefore propose gemcitabine is a promising chemotherapeutic agent that warrants further investigation as a treatment option for high-grade meningioma.

HSP90 inhibitors in the context of heat shock and the unfolded protein response: effects on a primary canine pulmonary adenocarcinoma cell line

BACKGROUND

Agents targeting HSP90 and GRP94 are seldom tested in stressed contexts such as heat shock (HS) or the unfolded protein response (UPR). Tumor stress often activates HSPs and the UPR as pro-survival mechanisms. This begs the question of stress effects on chemotherapeutic efficacy, particularly with drugs targeting chaperones such as HSP90 or GRP94. We tested the utility of several HSP90 inhibitors, including PU-H71 (targeting GRP94), on a primary canine lung cancer line under HS/UPR stress compared to control conditions.

METHODS

We cultured canine bronchoalveolar adenocarcinoma cells that showed high endogenous HSP90 and GRP94 expression; these levels substantially increased upon HS or UPR induction. We treated cells with HSP90 inhibitors 17-DMAG, 17-AAG or PU-H71 under standard conditions, HS or UPR. Cell viability/survival was assayed. Antibody arrays measured intracellular signalling and apoptosis profiles.

RESULTS

HS and UPR had varying effects on cells treated with different HSP90 inhibitors; in particular, HS and UPR promoted resistance to inhibitors in short-term assays, but combinations of UPR stress and PU-H571 showed potent cytotoxic activity in longer-term assays. Array data indicated altered signalling pathways, with apoptotic and pro-survival implications. UPR induction + dual targeting of HSP90 and GRP94 swayed the balance toward apoptosis.

CONCLUSION

Cellular stresses, endemic to tumors, or interventionally inducible, can deflect or enhance chemo-efficacy, particularly with chaperone-targeting drugs. Stress is likely not held accountable when testing new pharmacologics or assessing currently-used drugs. A better understanding of stress impacts on drug activities should be critical in improving therapeutic targeting and in discerning mechanisms of drug resistance.

Optimization of Treatment Geometry to Reduce Normal Brain Dose in Radiosurgery of Multiple Brain Metastases with Single-Isocenter Volumetric Modulated Arc Therapy

Treatment of patients with multiple brain metastases using a single-isocenter volumetric modulated arc therapy (VMAT) has been shown to decrease treatment time with the tradeoff of larger low dose to the normal brain tissue. We have developed an efficient Projection Summing Optimization Algorithm to optimize the treatment geometry in order to reduce dose to normal brain tissue for radiosurgery of multiple metastases with single-isocenter VMAT. The algorithm: (a) measures coordinates of outer boundary points of each lesion to be treated using the Eclipse Scripting Application Programming Interface, (b) determines the rotations of couch, collimator, and gantry using three matrices about the cardinal axes, (c) projects the outer boundary points of the lesion on to Beam Eye View projection plane, (d) optimizes couch and collimator angles by selecting the least total unblocked area for each specific treatment arc, and (e) generates a treatment plan with the optimized angles. The results showed significant reduction in the mean dose and low dose volume to normal brain, while maintaining the similar treatment plan qualities on the thirteen patients treated previously. The algorithm has the flexibility with regard to the beam arrangements and can be integrated in the treatment planning system for clinical application directly.

Systemic therapy for recurrent meningioma

INTRODUCTION

Meningioma comprise 20-30% of all primary brain tumors. Notwithstanding surgery and radiotherapy, a subset of patients will manifest recurrent meningioma. Systemic therapy is recommended only when further surgery and radiotherapy are not possible. No prospective study with a high level of evidence is available to inform as to recommendations regarding systemic therapy.

AREAS COVERED

We aim to summarize systemic therapies for recurrent meningioma. Expert commentary: Hydroxurea, temozolomide, irinotecan, the combination of cyclophosphamide/adriamycine/vincristine, interferon-alpha, somatostatin analogs, mifepristone, megestrol acetate, imatinib, erlotinib and gefitinib are considered as having limited efficacy. Potential activity of VEGF (vascular endothelial growth factor) inhibitors such as sunitinib, valatinib, and bevacizumab is suggested in small non-controlled studies and requires validation in randomized trials. The identification of new prognostic markers such as TERT promoter mutations and potential new therapeutic targets, such as KLF4, AKT1, TRAF7, and SMO mutations hopefully facilitate this endeavor.