Serum Levels of Vascular Endothelial Growth Factor and Its Receptor in Newly Diagnosed Paediatric Acute Lymphoblastic Leukemia

Autocrine and paracrine loop involving vascular endothelial growth factor (VEGF) and its receptor have been described in haematological malignancies. However, scarce literature is present on angiogenesis in paediatric acute lymphoblastic leukemia (ALL) with studies showing controversial results. The aim was to study serum levels of VEGF and its receptors in paediatric ALL at the time of diagnosis and at the end of induction phase and to compare these levels with clinico-haematological parameters in these patients. Serum VEGF, VEGFR-1 and VEGFR-2 levels were measured by enzyme-linked immunoabsorbant assay at diagnosis (day 0) and at the end of induction phase (day 35) in 30 newly diagnosed paediatric ALL patients and in 10 healthy controls. Median s-VEGF was significantly lower at day 0 as compared to day 35 (196.15 vs. 606.75 pg/ml: p < 0.001). s-VEGFR-1 levels were detectable only in 7 patients at day 0 and were below detection level at day 35 in all patients. Median s-VEGFR-2 at day 0 was significantly lower as compared to day 35 (17,577.5 vs. 20,507.5 pg/ml; p = 0.005). Median VEGF-R1 showed an inverse relationship with VEGF-R2 but was statistically insignificant. All patients were in remission at the end of induction. Thus, leukemic infiltration of bone marrow affects angiogenesis and reduces pro-angiogenic markers VEGF and VEGFR-2 in serum possibly due to increased local consumption by blasts. A successful induction leads to clearing of blasts causing restoration of normal hematopoiesis with normalization of VEGF and VEGFR-2 levels.

Phase 1 study of sirolimus in combination with oral cyclophosphamide and topotecan in children and young adults with relapsed and refractory solid tumors

Purpose

To determine the maximum tolerated dose (MTD), toxicities, and pharmacodynamics effects of sirolimus combined with oral metronomic topotecan and cyclophosphamide in a pediatric population.

Materials and Methods

Patients who were 1 to 30 years of age with relapsed/refractory solid tumors (including CNS) were eligible. Patients received daily oral sirolimus and cyclophosphamide (25-50 mg/m²/dose) on days 1-21 and oral topotecan (0.8 mg/m²/dose) on days 1-14 in 28-day cycles. Sirolimus steady-state plasma trough concentrations of 3-7.9 ng/mL and 8-12.0 ng/mL were evaluated, with dose escalation based on a 3+3 phase 1 design. Biomarkers of angiogenesis were also evaluated.

Results

Twenty-one patients were treated (median age 18 years; range 9-30). Dose-limiting toxicities included myelosuppression, ALT elevation, stomatitis, and hypertriglyceridemia. The MTD was sirolimus with trough goal of 8-12.0 ng/mL; cyclophosphamide 25 mg/m²/dose; and topotecan 0.8 mg/m²/dose. No objective responses were observed. Four patients had prolonged stable disease > 4 cycles (range 4-12). Correlative biomarker analyses demonstrated reductions in thrombospondin-1 (p=0.043) and soluble vascular endothelial growth factor receptor-2 plasma concentrations at 21 days compared to baseline.

Conclusions

The combination of oral sirolimus, topotecan, and cyclophosphamide was well tolerated and biomarker studies demonstrated modulation of angiogenic pathways with this regimen.

Molecular ultrasound imaging using contrast agents targeting endoglin, vascular endothelial growth factor receptor 2 and integrin

Expression levels of endoglin, αv integrin and vascular endothelial growth factor receptor 2 (VEGFR2) were investigated using targeted, contrast-enhanced ultrasonography in murine melanoma tumor models. Microvasculature and expression levels of biomarkers were investigated using specific contrast agents conjugated with biotinylated monoclonal antibodies. Ultrasound signal intensity from bound contrast agents was evaluated in two groups of mice: control mice and mice treated with sorafenib. Expression levels were analyzed by immunohistochemistry. Endoglin biomarkers were more highly expressed than αv integrin and VEGFR2. Endoglin decreased in the sorafenib group, whereas it tended to increase with time in the control group. Targeted ultrasound contrast agents may be used for non-invasive longitudinal evaluation of tumor angiogenesis during tumor growth or therapeutic treatment in preclinical studies. Endoglin protein, which plays an important role in angiogenesis, seems to be a target of interest for detection of cancer and for prediction of therapeutic efficacy.

Phase I study of vinblastine and sirolimus in pediatric patients with recurrent or refractory solid tumors

BACKGROUND

The combination of vinblastine and mammalian target of rapamycin (mTOR) inhibitor sirolimus inhibits the growth of neuroblastoma xenografts through pro-apoptotic and anti-angiogenic mechanisms. This phase I study aimed to explore the safety and toxicity of this combination in pediatric patients with advanced solid tumors.

PROCEDURE

Patients ≤21 years of age with recurrent/refractory solid tumors (including CNS) were eligible. Sirolimus was administered daily by mouth or nasogastric (NG) tube, with doses adjusted to achieve a target trough concentration of 10-15 ng/ml, with weekly intravenous vinblastine (dose escalated 4-6 mg/m(2)/dose according to 3 + 3 phase I design).

RESULTS

Fourteen patients were enrolled (median age 8.7 years; range 2.3-19) of whom 12 were evaluable for toxicity and 11 for response. One patient experienced a dose-limiting toxicity (grade 3 mucositis) at the highest vinblastine dose level. Myelosuppression was the most common toxicity. Dose-adjusted sirolimus trough concentrations were significantly lower in patients receiving drug via NG tube (1.50 ± 0.75 ng/ml/mg vs. 2.25 ± 1.07 ng/ml/mg for oral administration). Correlative biomarker analysis demonstrated a significant reduction in serum concentration of soluble vascular endothelial growth factor receptor (sVEGFR2) at 28 days compared to baseline consistent with inhibition of angiogenesis. One patient had a partial response and three had stable disease for more than 3 months.

CONCLUSIONS

The combination of mTOR inhibitor and vinblastine given over an extended continuous schedule is safe, associated with a reduction in circulating angiogenic factor (CAF) VEGFR2 and resulted in clinical responses. Future studies using the intravenously administered mTOR inhibitor temsirolimus are planned.

Serum vascular endothelial growth factor-a levels during induction therapy in children with acute lymphoblastic leukemia

OBJECTIVE

To evaluate serum vascular endothelial growth factor (VEGF) levels in children with acute lymphoblastic leukemia (ALL) during the induction phase of chemotherapy.

DESIGN

Prospective sudy.

SETTING

Setting: Hospital-based study over 18 months.

PATIENTS

30 children with ALL and 17 healthy age- and sex-matched controls.

INTERVENTION

Serum concentration of VEGF-A-165 isoform (s-VEGF) was measured by enzyme-linked immunoabsorbant assay at diagnosis and at the end of induction chemotherapy.

MAIN OUTCOME MEASURES

s-VEGF was compared with markers of tumor burden. Kinetics of s-VEGF was assessed in response to induction chemotherapy.

RESULTS

Median VEGF was significantly lower in untreated patients than in controls (17.0 vs. 42.6 pg/mL, P=0.004). s-VEGF levels were fairly correlated with WBC count (r=-0.56, P=0.004) and LDH (r=-0.52, P=0.02) at diagnosis. All patients but one were in morphologic remission at the end of induction. Median s-VEGF concentration on day 29/33 was significantly higher than on day 1 (44.2 pg/mL, P=0.009).

CONCLUSIONS

Untreated children with ALL have significantly lower s-VEGF concentration than controls. At the end of the induction therapy, s-VEGF increased to levels similar to controls. The role of ligand-receptor interaction between VEGF and VEGF receptors on leukemia cells needs to be further delineated.To identify the risk factors for scholastic backwardness in children.

Clinical development of VEGF signaling pathway inhibitors in childhood solid tumors

Angiogenesis is a target shared by both adult epithelial cancers and the mesenchymal or embryonal tumors of childhood. Development of antiangiogenic agents for the pediatric population has been complicated by largely theoretical concern for toxicities specific to the growing child and prioritization among the many antiangiogenic agents being developed for adults. This review summarizes the mechanism of action and preclinical data relevant to childhood cancers and early-phase clinical trials in childhood solid tumors. Single-agent adverse event profiles in adults and children are reviewed with emphasis on cardiovascular, bone health, and endocrine side effects. In addition, pharmacological factors that may be relevant for prioritizing clinical trials of these agents in children are reviewed. Considerations for further clinical evaluation should include preclinical data, relative potency, efficacy in adults, and the current U.S. Food and Drug Administration approval status. Toxicity profiles of vascular endothelial growth factor (VEGF) signaling pathway inhibitors may be age dependent and ultimately, their utility in the treatment of childhood cancer will require combination with standard cytotoxic drugs or other molecularly targeted agents. In combination studies, toxicity profiles, potential drug interactions, and late effects must be considered. Studies to assess the long-term impact of VEGF signaling pathway inhibitors on cardiovascular, endocrine, and bone health in children with cancer are imperative if these agents are to be administered to growing children and adolescents with newly diagnosed cancers.