Pharmacotherapeutic management of pediatric gliomas : current and upcoming strategies

Genetic Alteration Analysis of IDH1, IDH2, CDKN2A, MYB and MYBL1 in Pediatric Low-Grade Gliomas

Objective

To investigate pediatric low-grade gliomas for alterations in IDH1, IDH2, CDKN2A, MYB, and MYBL1.

Materials and Methods

DNA and RNA were extracted from 62 pediatric gliomas. Molecular methods included PCR, RT-PCR, and RNA sequencing; Sanger sequencing was used for validation.

Results

Analysis for hotspot genetic alterations in IDH1 R132 and IDH2 R172 (45 and 33 samples) was negative in all cases. CDKN2A deletions were detected in exons 1 and 2 in 1 (pleomorphic xanthoastrocytoma) sample of 9 samples analyzed. Of 10 samples analyzed for MYB translocation, 4 each were positive for translocations with exon 2 and exon 3 of PCDHGA1. Six samples showed MYBL rearrangement. The lack of IDH1/2 genetic alterations is in accordance with the literature in pediatric tumors. Alterations in MYB, MYBL were recently reported to characterize diffuse grade II, but not grade I, gliomas.

Conclusion

We optimized methods for analyzing gene variations and correlated the findings to pathological grade. The high incidence of MYB and MYBL need further evaluation. We also compared DNA, RNA, and RNA sequencing results for fusion, translocation, and genetic alterations. More accurate identification of the underlying biology of pediatric gliomas has implications for the development of targeted treatment.

Recurrent or progressive pediatric brain tumors: population pharmacokinetics and exposure-response analysis of pomalidomide

BACKGROUND

Pomalidomide, an immunomodulatory drug, was investigated for pediatric brain tumors. The objectives of this analysis were to characterize the PK of pomalidomide and to examine exposure-response relationship in pediatric patients with recurrent or progressive primary brain tumors.

METHODS

Nonlinear mixed effects modeling was employed in developing a population PK model of pomalidomide using a total of 343 concentrations from 70 patients. Logistic regression models were used for exposure-response analyses.

RESULTS

The PK of pomalidomide was adequately described with a one compartment model with first-order absorption and elimination. Body surface area (BSA) was identified as a statistically significant covariate of apparent clearance and volume of distribution; however, the impact of BSA on exposure parameters was not deemed clinically relevant. Pomalidomide exposure was not associated with higher probabilities of treatment-emergent adverse events or pomalidomide dose interruptions during Cycle 1. Covariates such as BSA, weight, sex, age, and race had no significant effect on safety endpoints. The PK of pomalidomide in pediatric patients with brain tumors was generally consistent with that in adult patients with multiple myeloma after adjustment for BSA.

CONCLUSIONS

This is the first study to characterize PK of pomalidomide in pediatric patients, which supports BSA-based dosing for pediatric patients.

IMPACT

This is the first study to characterize PK of pomalidomide in pediatric patients, which supports BSA-based dosing for pediatric patients. There is no significant pomalidomide PK difference between adults and pediatrics. Pomalidomide exposure was not associated with higher probabilities of treatment-emergent adverse event or pomalidomide dose interruptions during Cycle 1.

Pediatric Glioma at the Optic Pathway and Thalamus

Gliomas are the most common pediatric tumors of the central nervous system. In this review, we discuss the clinical features, treatment paradigms, and evolving concepts related to two types of pediatric gliomas affecting two main locations: the optic pathway and thalamus. In particular, we discuss recently revised pathologic classification, which adopting molecular parameter. We believe that our review contribute to the readers' better understanding of pediatric glioma because pediatric glioma differs in many ways from adult glioma according to the newest advances in molecular characterization of this tumor. A better understanding of current and evolving issues in pediatric glioma is needed to ensure effective management decision.

A pilot study of bevacizumab-based therapy in patients with newly diagnosed high-grade gliomas and diffuse intrinsic pontine gliomas

Although bevacizumab has not proven effective in adults with newly diagnosed high-grade gliomas (HGG), feasibility in newly diagnosed children with diffuse intrinsic pontine gliomas (DIPG) or HGG has not been reported in a prospective study. In a safety and feasibility study, children and young adults with newly diagnosed HGG received radiotherapy (RT) with bevacizumab (10 mg/kg: days 22, 36) and temozolomide (75-90 mg/m(2)/day for 42 days) followed by bevacizumab (10 mg/kg, days 1, 15), irinotecan (125 mg/m(2), days 1, 15) and temozolomide (150 mg/m(2)/day days 1-5). DIPG patients did not receive temozolomide. Telomerase activity, quality of life (QOL), and functional outcomes were assessed. Among 27 eligible patients (15 DIPG, 12 HGG), median age 10 years (range 3-29 years), 6 discontinued therapy for toxicity: 2 during RT (grade 4 thrombocytopenia, grade 3 hepatotoxicity) and 4 during maintenance therapy (grade 3: thrombosis, hypertension, skin ulceration, and wound dehiscence). Commonest ≥grade 3 toxicities included lymphopenia, neutropenia and leukopenia. Grade 3 hypertension occurred in 2 patients. No intracranial hemorrhages occurred. For DIPG patients, median overall survival (OS) was 10.4 months. For HGG patients, 3-year progression free survival and OS were 33 % (SE ± 14 %) and 50 % (SE ± 14 %), respectively. All 3 tested tumor samples, demonstrated histone H3.3K27M (n = 2 DIPG) or G34R (n = 1 HGG) mutations. QOL scores improved over the course of therapy. A bevacizumab-based regimen is feasible and tolerable in newly diagnosed children and young adults with HGG and DIPG.

Confirmation of Bevacizumab Activity, and Maintenance of Efficacy in Retreatment After Subsequent Relapse, in Pediatric Low-grade Glioma

BACKGROUND

Management of low-grade gliomas (LGG) can be a challenge, particularly when not resectable and refractory or recurrent following standard treatments. We undertook a retrospective analysis of 2 institutions' experiences treating children for refractory or progressive LGG with bevacizumab-based therapy (BBT).

PROCEDURE

Inclusion criteria were patients younger than 18 years of age who had previously failed one or more lines of therapy. Treatment was intravenous bevacizumab 10 mg/kg and intravenous irinotecan 125 to 150 mg/m2 every 2 weeks.

RESULTS

Sixteen children (median age of 8.6 y), 5 with neurofibromatosis type 1 and 8 with disseminated disease were treated between 2009 and 2013. Median duration of treatment was 12 months (range, 3 to 45 mo). Seven patients (44%) showed clinical improvement (3 patients within a month) and 8 patients (50%) remained clinically stable during BBT. Imaging studies showed 3 (19%) had a partial response, 11 (69%) stable disease, and 2 (12%) had progressive disease. Four patients had progressive disease after stopping BBT (median duration of 5 mo). Three of these 4 were able to be retreated with BBT and all achieved an objective response. Treatment was well tolerated with no grade 3 or 4 toxicities related to bevacizumab. Irinotecan was discontinued in 4 patients because of grade 2-3 toxicities.

CONCLUSIONS

We conclude that BBT is well tolerated and led to disease control in patients with refractory or recurrent cases of LGG. Retreatment with BBT led to disease control in most of these cases. Larger, prospective studies are warranted to confirm these results.

Aplysin enhances temozolomide sensitivity in glioma cells by increasing miR-181 level

PURPOSE

Aplysin, a natural brominate compound from marine organisms, has been demonstrated to exhibit anti-tumor activity, mainly by inducing apoptosis and cell cycle arrest. However, its effect on glioma is still unknown. In this study, we evaluated the effects of aplysin on the malignant properties of glioma cells and its enhancing effect on temozolomide (TMZ) action against drug-resistant glioma cell lines.

METHODS

We employed several human glioma cell lines and primary glioma cells to address this issue with multidisciplinary approaches.

RESULTS

The combined application of aplysin and TMZ significantly sensitizes glioma cells to TMZ action, compared with TMZ alone. miRNA profile analysis revealed that the abundance of miR-181, an important glioma tumor suppressors believed to enhance TMZ effect, was greatly elevated in aplysin-treated glioma cell lines. The aplysin-induced TMZ sensitivity is dependent on MEK1 in glioma cells. Overexpression of MEK1 was able to abolish the effect of aplysin on glioma cells.

CONCLUSIONS

We found that aplysin can enhance the effect of TMZ on glioma cells by increasing miR-181 expression.

Molecular precision chemotherapy: overcoming resistance to targeted therapies?

Cytotoxic drugs may have specific effects on oncogenes and their downstream targets. Increase of cancer cell sensitivity due to repression of an oncogene downstream target can be specifically addressed by combined precision chemotherapy, increasing the therapeutic index of chemotherapy and overcoming resistance to highly selective targeted therapies.