Radhika Peddinti

Anti-angiogenic SPARC peptides inhibit progression of neuroblastoma tumors

BackgroundNew, more effective strategies are needed to treat highly aggressive neuroblastoma. Our laboratory has previously shown that full-length Secreted Protein Acidic and Rich in Cysteine (SPARC) and a SPARC peptide corresponding to the follistatin domain of the protein (FS-E) potently block angiogenesis and inhibit the growth of neuroblastoma tumors in preclinical models. Peptide FS-E is structurally complex and difficult to produce, limiting its potential as a therapeutic in the clinic.ResultsIn this study, we synthesized two smaller and structurally more simple SPARC peptides, FSEN and FSEC, that respectively correspond to the N-and C-terminal loops of peptide FS-E. We show that both peptides FSEN and FSEC have anti-angiogenic activity in vitro and in vivo, although FSEC is more potent. Peptide FSEC also significantly inhibited the growth of neuroblastoma xenografts. Histologic examination demonstrated characteristic features of tumor angiogenesis with structurally abnormal, tortuous blood vessels in control neuroblastoma xenografts. In contrast, the blood vessels observed in tumors, treated with SPARC peptides, were thin walled and structurally more normal. Using a novel method to quantitatively assess blood vessel abnormality we demonstrated that both SPARC peptides induced changes in blood vessel architecture that are consistent with blood vessel normalization.ConclusionOur results demonstrate that SPARC peptide FSEC has potent anti-angiogenic and anti-tumorigenic effects in neuroblastoma. Its simple structure and ease of production indicate that it may have clinical utility in the treatment of high-risk neuroblastoma and other types of pediatric and adult cancers, which depend on angiogenesis.

Prominent Microvascular Proliferation in Clinically Aggressive Neuroblastoma

Purpose: Tumor vasculature is disorganized and glomeruloid microvascular proliferation (MVP) has been identified as a poor prognosticator in some adult cancers. To determine the clinical significance of MVP, including glomeruloid MVP in neuroblastoma, we initially examined vessel architecture in tumor sections from 51 children diagnosed at Childrens Memorial Hospital (CMH) and subsequently evaluated 154 neuroblastoma tumors on a tissue microarray constructed at Childrens Hospital of Philadelphia (CHOP). Experimental Design: H&E sections were examined for the presence of structurally abnormal vessels and further characterized by immunostaining for CD31 and von Willebrand factor to highlight endothelial cells and α-smooth muscle actin for pericytes. Tumors with thickened walls containing a complete layer of hypertrophic endothelial cells plus additional layers of vascular mural cells were classified as MVP positive. Associations between MVP and established clinicopathologic features and outcome were assessed. Results: In both series, MVP was significantly associated with Schwannian stroma-poor histology (CMH, P = 0.008; CHOP, P < 0.001) and decreased survival probability (CMH, P = 0.017; CHOP, P = 0.014). In the CHOP series, MVP was associated with high-risk group classification (P < 0.001), although this association was not seen in the smaller CMH cohort. Conclusions: The association between MVP and poor outcome provides further support for the concept that angiogenesis plays an important role in determining the biological behavior of neuroblastoma tumors. Our results also indicate that angiogenesis is regulated differently in Schwannian stroma-rich versus stroma-poor neuroblastoma tumors. Further studies investigating the activity of angiogenic inhibitors in children with clinically aggressive stroma-poor neuroblastoma are warranted.

Truncated DNMT3B Isoform DNMT3B7 Suppresses Growth, Induces Differentiation, and Alters DNA Methylation in Human Neuroblastoma

Epigenetic changes in pediatric neuroblastoma may contribute to the aggressive pathophysiology of this disease, but little is known about the basis for such changes. In this study, we examined a role for the DNA methyltransferase DNMT3B, in particular, the truncated isoform DNMT3B7, which is generated frequently in cancer. To investigate if aberrant DNMT3B transcripts alter DNA methylation, gene expression, and phenotypic character in neuroblastoma, we measured DNMT3B expression in primary tumors. Higher levels of DNMT3B7 were detected in differentiated ganglioneuroblastomas compared to undifferentiated neuroblastomas, suggesting that expression of DNMT3B7 may induce a less aggressive clinical phenotype. To test this hypothesis, we investigated the effects of enforced DNMT3B7 expression in neuroblastoma cells, finding a significant inhibition of cell proliferation in vitro and angiogenesis and tumor growth in vivo. DNMT3B7-positive cells had higher levels of total genomic methylation and a dramatic decrease in expression of the FOS and JUN family members that comprise AP1 transcription factors. Consistent with an established antagonistic relationship between AP1 expression and retinoic acid receptor activity, increased differentiation was seen in the DNMT3B7-expressing neuroblastoma cells following treatment with all-trans retinoic acid (ATRA) compared to controls. Our results indicate that DNMT3B7 modifies the epigenome in neuroblastoma cells to induce changes in gene expression, inhibit tumor growth, and increase sensitivity to ATRA.

Presence of cancer-associated fibroblasts inversely correlates with Schwannian stroma in neuroblastoma tumors.

Stromal cells have a central function in the regulation of tumor angiogenesis. Recent studies have shown that stromal myofibroblasts (cancer-associated fibroblasts) actively promote tumor growth and enhance tumor angiogenesis in many types of adult carcinomas. To evaluate the function cancer-associated fibroblasts have in neuroblastoma angiogenesis and investigate their relationship to stromal Schwann cells, we quantified cancer-associated fibroblasts in 60 primary neuroblastoma tumors and in a novel neuroblastoma xenograft model in which murine Schwann cells were induced to infiltrate into the tumor stroma. Tumor sections were examined for presence of microvascular proliferation, a hallmark of tumor angiogenesis. Cancer-associated fibroblasts were characterized by positive immunostaining for α-smooth muscle actin (α-SMA) and were distinguished from pericytes by staining negatively for high-molecular-weight caldesmon. α-SMA-positive cells were quantified and their number was defined as high when >1.0% of the area was positive. Associations between high cancer-associated fibroblast number, microvascular proliferation and established prognosticators were analyzed. High numbers of cancer-associated fibroblasts were associated with Schwannian stroma-poor histopathology and microvascular proliferation. Thirty-seven (80%) of the 46 Schwannian stroma-poor tumors had high numbers of cancer-associated fibroblasts in the tumor stroma compared to only 2 (14%) of the 14 Schwannian stroma-rich/dominant tumors (P<0.001). Thirty-three (89%) of 37 tumors with microvascular proliferation had high numbers of cancer-associated fibroblasts compared to 9 (40%) of 22 tumors without microvascular proliferation (P<0.001). In the xenografts with infiltrating Schwann cells (n=10), the number of cancer-associated fibroblasts per mm2 was approximately sevenfold less than in the control xenografts without stromal Schwann cells (n=9) (mean of 51±30 vs 368±105, respectively; P<0.001). Thus, cancer-associated fibroblasts were inversely associated with presence of Schwann cells, suggesting that Schwann cells may prevent the activation of fibroblasts. A deeper understanding of the function cancer-associated fibroblasts have in neuroblastoma angiogenesis may guide future development of stroma-directed therapeutic strategies.

Sorafenib inhibits neuroblastoma cell proliferation and signaling, blocks angiogenesis, and impairs tumor growth†

More effective therapy for children with high‐risk neuroblastoma is desperately needed. Preclinical studies have shown that neuroblastoma tumor growth can be inhibited by agents that block angiogenesis. We hypothesized that drugs which target both neuroblastoma cells and tumor angiogenesis would have potent anti‐tumor activity. In this study we tested the effects of sorafenib, a multi‐kinase inhibitor, on neuroblastoma cell proliferation and signaling, and in mice with subcutaneous human neuroblastoma xenografts or orthotopic adrenal tumors.

The quinoxaline anti-tumor agent (R+)XK469 inhibits neuroblastoma tumor growth.

The quinoxaline anti‐tumor agent (R+)XK469 mediates its effects by topoisomerase IIB inhibition. This report describes a 14‐year old with relapsed neuroblastoma who experienced disease stabilization for 14 months while receiving (R+)XK469 monotherapy. Due to this favorable response, laboratory studies were undertaken to determine efficacy in the preclinical setting. (R+)XK469 inhibited proliferation, caused G2 cell cycle arrest of neuroblastoma cells in vitro, and inhibited growth of neuroblastoma xenograft tumors. These preclinical results, coupled with the favorable clinical response, demonstrate that (R+)XK469 and similar anti‐tumor agents may be effective in the treatment of high‐risk neuroblastoma and warrant further testing. Pediatr Blood Cancer. 2010;56:164–167.

Outpatient Management of Febrile Children With Sickle Cell Disease

The electronic medical records at 2 children’s hospitals were reviewed from June 1, 2011 to May 31, 2013 for all patients with sickle cell disease who presented with fever. Of a total of 390 blood cultures drawn, 11 cultures (2.8%) turned positive with only 1 (0.3%) growing a true pathogen. This culture turned positive in 13 hours. There were 154 patients who received exclusive outpatient management of fever. Fourteen patients (9.1%) completed 1 acute care visit, 16 patients (10.4%) completed 2 acute care visits, and 124 patients (80.5%) completed 3 acute care visits. Of those treated exclusively as outpatients, there was 1 positive culture that was considered a contaminant. Although the overall rate of positivity was low, this study confirms previous findings that pediatric blood cultures become positive with pathogens within 48 hours. Given the high rate of compliance and early time to positivity of true pathogens, we suggest that follow-up for the febrile sickle cell disease patients can be treated on an outpatient basis.

Causes and Diagnosis of Abnormal Vaginal Bleeding.

Abnormal vaginal bleeding in a postmenarchal adolescent patient is most often related to dysfunctional uterine bleeding. However, there are other potential etiologies, including hematologic disorders, infections, and oncologic problems. We present a 12-year-old girl who presented with prolonged vaginal bleeding and was ultimately diagnosed with rhabdomyosarcoma. In this article, we discuss the approach to a patient with vaginal bleeding along with a more in-depth review of risk stratification in rhabdomyosarcoma, including treatment options such as chemotherapy, surgery, and radiation therapy.

Lead Toxicity in the Pediatric Patient with Sickle Cell Disease: Unique Risks and Management

Lead toxicity is the result of lead ingestion, one of the most common ingestions in the pediatric population. Nationwide and statewide efforts to recognize and curtail this epidemic have led to declining rates of toxicity. In patients with sickle cell disease (SCD), lead toxicity can be an elusive diagnosis due to overlapping symptom profiles, and inconsistent follow-up with a primary care physician can make the diagnosis even more difficult. In this article, two illustrative cases of lead toxicity in patients with SCD are described. The discussion reviews the current risk factors, screening, and inpatient management of lead toxicity, as well as describing the unique and sometimes confounding presentations of lead toxicity versus sickle cell crisis. [Pediatr Ann. 2018;47(1):e36-e40.].

Exosomes contribute to endothelial integrity and acute chest syndrome risk: Preliminary findings

Acute Chest Syndrome (ACS) is one of the leading causes of death among children with Sickle Cell Disease (SCD). Disruption of microvascular integrity is critical to the pathophysiology of ACS, but the factors governing its phenotypic variability are incompletely understood. Because circulating exosomes have been implicated in vascular dysfunction in various diseases, we hypothesized that exosomes induce endothelial dysfunction in patients who experience ACS.