Preclinical evaluation of convection-enhanced delivery of liposomal doxorubicin to treat pediatric diffuse intrinsic pontine glioma and thalamic high-grade glioma.

OBJECTIVE Pediatric high-grade gliomas (pHGGs) including diffuse intrinsic pontine gliomas (DIPGs) are primary brain tumors with high mortality and morbidity. Because of their poor brain penetrance, systemic chemotherapy regimens have failed to deliver satisfactory results; however, convection-enhanced delivery (CED) may be an alternative mode of drug delivery. Anthracyclines are potent chemotherapeutics that have been successfully delivered via CED in preclinical supratentorial glioma models. This study aims to assess the potency of anthracyclines against DIPG and pHGG cell lines in vitro and to evaluate the efficacy of CED with anthracyclines in orthotopic pontine and thalamic tumor models. METHODS The sensitivity of primary pHGG cell lines to a range of anthracyclines was tested in vitro. Preclinical CED of free doxorubicin and pegylated liposomal doxorubicin (PLD) to the brainstem and thalamus of naïve nude mice was performed. The maximum tolerated dose (MTD) was determined based on the observation of clinical symptoms, and brains were analyzed after H & E staining. Efficacy of the MTD was tested in adult glioma E98-FM-DIPG and E98-FM-thalamus models and in the HSJD-DIPG-007-Fluc primary DIPG model. RESULTS Both pHGG and DIPG cells were sensitive to anthracyclines in vitro. Doxorubicin was selected for further preclinical evaluation. Convection-enhanced delivery of the MTD of free doxorubicin and PLD in the pons was 0.02 mg/ml, and the dose tolerated in the thalamus was 10 times higher (0.2 mg/ml). Free doxorubicin or PLD via CED was ineffective against E98-FM-DIPG or HSJD-DIPG-007-Fluc in the brainstem; however, when applied in the thalamus, 0.2 mg/ml of PLD slowed down tumor growth and increased survival in a subset of animals with small tumors. CONCLUSIONS Local delivery of doxorubicin to the brainstem causes severe toxicity, even at doxorubicin concentrations that are safe in the thalamus. As a consequence, the authors could not establish a therapeutic window for treating orthotopic brainstem tumors in mice. For tumors in the thalamus, therapeutic concentrations to slow down tumor growth could be reached. These data suggest that anatomical location determines the severity of toxicity after local delivery of therapeutic agents and that caution should be used when translating data from supratentorial CED studies to treat infratentorial tumors.

Bevacizumab Targeting Diffuse Intrinsic Pontine Glioma: Results of 89Zr-Bevacizumab PET Imaging in Brain Tumor Models.

The role of the VEGF inhibitor bevacizumab in the treatment of diffuse intrinsic pontine glioma (DIPG) is unclear. We aim to study the biodistribution and uptake of zirconium-89 ((89)Zr)-labeled bevacizumab in DIPG mouse models. Human E98-FM, U251-FM glioma cells, and HSJD-DIPG-007-FLUC primary DIPG cells were injected into the subcutis, pons, or striatum of nude mice. Tumor growth was monitored by bioluminescence imaging (BLI) and visualized by MRI. Seventy-two to 96 hours after (89)Zr-bevacizumab injections, mice were imaged by positron emission tomography (PET), and biodistribution was analyzed ex vivo High VEGF expression in human DIPG was confirmed in a publically available mRNA database, but no significant (89)Zr-bevacizumab uptake could be detected in xenografts located in the pons and striatum at an early or late stage of the disease. E98-FM, and to a lesser extent the U251-FM and HSJD-DIPG-007 subcutaneous tumors, showed high accumulation of (89)Zr-bevacizumab. VEGF expression could not be demonstrated in the intracranial tumors by in situ hybridization (ISH) but was clearly present in the perinecrotic regions of subcutaneous E98-FM tumors. The poor uptake of (89)Zr-bevacizumab in xenografts located in the brain suggests that VEGF targeting with bevacizumab has limited efficacy for diffuse infiltrative parts of glial brain tumors in mice. Translating these results to the clinic would imply that treatment with bevacizumab in patients with DIPG is only justified after targeting of VEGF has been demonstrated by (89)Zr-bevacizumab immuno-PET. We aim to confirm this observation in a clinical PET study with patients with DIPG. Mol Cancer Ther; 15(9); 2166-74. ©2016 AACR.

In vitro drug response and efflux transporters associated with drug resistance in pediatric high grade glioma and diffuse intrinsic pontine glioma.

Pediatric high-grade gliomas (pHGG), including diffuse intrinsic pontine gliomas (DIPG), are the leading cause of cancer-related death in children. While it is clear that surgery (if possible), and radiotherapy are beneficial for treatment, the role of chemotherapy for these tumors is still unclear. Therefore, we performed an in vitro drug screen on primary glioma cells, including three DIPG cultures, to determine drug sensitivity of these tumours, without the possible confounding effect of insufficient drug delivery. This screen revealed a high in vitro cytotoxicity for melphalan, doxorubicine, mitoxantrone, and BCNU, and for the novel, targeted agents vandetanib and bortezomib in pHGG and DIPG cells. We subsequently determined the expression of the drug efflux transporters P-gp, BCRP1, and MRP1 in glioma cultures and their corresponding tumor tissues. Results indicate the presence of P-gp, MRP1 and BCRP1 in the tumor vasculature, and expression of MRP1 in the glioma cells themselves. Our results show that pediatric glioma and DIPG tumors per se are not resistant to chemotherapy. Treatment failure observed in clinical trials, may rather be contributed to the presence of drug efflux transporters that constitute a first line of drug resistance located at the blood-brain barrier or other resistance mechanism. As such, we suggest that alternative ways of drug delivery may offer new possibilities for the treatment of pediatric high-grade glioma patients, and DIPG in particular.

Effect of a treatment strategy consisting of pravastatin, vitamin E, and homocysteine lowering on arterial compliance and distensibility in patients with mild-to-moderate chronic kidney disease.

BACKGROUND: Arterial stiffness is increased in chronic kidney disease (CKD). Intervention studies aimed at reduction of arterial stiffness in dialysis patients have been disappointing. We therefore investigated the effect of pravastatin, vitamin E, and homocysteine lowering on arterial compliance and distensibility coefficients in mild-to-moderate CKD. METHODS: This is a sub-study of the ATIC study, a randomized, double-blind trial in 93 CKD patients. The treatment group received pravastatin to which vitamin E supplementation was added after 6 months and homocysteine lowering therapy after another 6 months. Measurement of the distensibility coefficient (DC) and the compliance coefficient (CC) of the common carotid (CCA), femoral (FA) and brachial artery (BA) was performed at 0, 6, 12, 18 months. Young's elastic modulus (YEM) was measured in the common carotid artery. RESULTS: After 18 months, CCA-DC increased from mean (SD) 15.15 (6.67) to 16.52 (6.37) × 10-3kPa-1 in the treatment and decreased from 18.44 (8.19) to 16.26 (7.35) in the placebo group (p = 0.057). CCA-CC increased from 0.64 (0.24) to 0.71 (0.26) mm2kPa-1 in the treatment and decreased from 0.77 (0.28) to 0.69 (0.25) in the placebo group (p < 0.0001). FA-DC had increased from 6.64 (3.45) to 11.46 (6.83) in the treatment group, and from 6.46 (2.85) to 7.08 (2.73) in the placebo group (p = 0.0001). FA-CC had increased from 0.46 (0.24) to 0.74 (0.44) in the treatment group, and from 0.48 (0.27) to 0.53 (0.21) in the placebo group (p = 0.008). BA-DC and CC, and CCA YEM were not significantly different between the groups. CONCLUSION: In patients with mild-to-moderate CKD, 18 months of treatment consisting of pravastatin, vitamin E and homocysteine lowering resulted in significant improvement of compliance and distensibility in CCA and FA. Since pravastatin was used throughout the observation period, it remains unclear whether the beneficial effects are attributable solely to the ongoing effect of pravastatin treatment, or if the additional interventions further slowed the progression of vascular stiffness. Therefore, larger studies with a longer period of follow-up observing the separate effects are needed.

Blood pressure and body composition in long-term survivors of childhood acute lymphoblastic leukemia.

BACKGROUND: Long-term survivors of acute lymphoblastic leukemia (ALL) in childhood are at increased risk of late effects of cancer treatment, among which are cardiovascular sequelae. Purpose of this study was to assess blood pressure and body composition in childhood ALL survivors and compare data to reference values from the general population. PROCEDURE: This single-center retrospective study included 68 survivors of childhood ALL with a median age of 25 years (range 16.4-39.5) and a median follow-up of 16.0 years (range 5.3-30.4). Data on previous treatment, blood pressure and measurements of weight and height at diagnosis and at long-term follow-up (from which body mass index (BMI) was calculated) were obtained from medical records. All data were converted to control-referenced standard deviation scores. RESULTS: Of the ALL survivors 48½% were prehypertensive and 22.1% were hypertensive. Both the mean systolic (mean SDS 0.736, P < 0.001) and diastolic blood pressure (mean SDS 0.409, P < 0.001) of survivors was significantly higher compared to reference control values. Based on BMI values, 38.2% of the survivors were considered overweight/obese and females, in contrast to males had a significantly higher BMI (mean SDS 1.355, P < 0.001) compared to reference values. In addition, females who had received cranial radiotherapy (mean SDS 2.078) had a significantly higher BMI than females who had not (mean SDS 0.512) (P = 0.009). CONCLUSIONS: Both diastolic and systolic blood pressure are significantly increased in survivors of childhood ALL. Female survivors treated with cranial radiation therapy have the highest prevalence and greatest risk of overweight/obesity. Therefore, survivors of childhood ALL are likely to be at an increased risk of cardiovascular disease later in life, which stresses the need for follow-up and adequate medical and/or life style interventions.