Pediatric low-grade gliomas: implications of the biologic era

For the past decade, it has been recognized that pediatric low-grade gliomas (LGGs) and glial-neuronal tumors carry distinct molecular alterations with resultant aberrant intracellular signaling in the Ras-mitogen-activated protein kinase pathway. The conclusions and recommendations of a consensus conference of how best to integrate the growing body of molecular genetic information into tumor classifications and, more importantly, for future treatment of pediatric LGGs are summarized here. There is uniform agreement that molecular characterization must be incorporated into classification and is increasingly critical for appropriate management. Molecular-targeted therapies should be integrated expeditiously, but also carefully into the management of these tumors and success measured not only by radiographic responses or stability, but also by functional outcomes. These trials need to be carried out with the caveat that the long-term impact of molecularly targeted therapy on the developing nervous system, especially with long duration treatment, is essentially unknown.

Hypofractionated Radiotherapy for Children With Diffuse Intrinsic Pontine Gliomas

Children with diffuse intrinsic pontine gliomas have very poor outcomes, with nearly all children dying from disease. Standard therapy includes 6 weeks of radiation. There have been descriptions of using a shortened course of radiation. We describe our experience with a hypofractionated radiotherapy approach delivered over five treatments. In seven children, hypofractionated radiotherapy was well tolerated, but symptomatic radiation necrosis was seen in three of the children. Overall survival was slightly shorter than previously described in the literature. We are developing a prospective dose-finding protocol with the goal of tolerable short-course radiation treatment with outcomes comparable to conventional radiation.

Abstract B69: Activation of the IL6/STAT3 pathway in childhood ependymoma is associated with a pro-inflammatory tumor microenvironment and a poor prognosis

To aid development of immunotherapy for poor outcome Group A ependymoma (EPN) in children we sought to identify the molecular pathway underlying the adverse pro-inflammatory phenotype associated with this molecular subgroup. We have previously shown the importance of immunological factors in EPN outcome and that an anti-tumor immunophenotype was critical in survival whereas a pro-inflammatory phenotype was associated with a poor outcome. Moreover we showed a strong correlation between these immunophenotypes and the newly recognized molecular subgroups of posterior fossa EPN. We showed that Group A EPN have an adverse pro-inflammatory immunophenotype at presentation which adversely affects outcome even at relapse.

We contrasted the gene expression profiles of patient tumor samples from Group A EPN to the more clinically favorable Group B EPN, as well as a broader panel of pediatric and adult brain tumors and normal brain, to identify potential molecular pathways that might be associated with the Group A immunophenotype. The results of these studies were validated using functional assays in short-term cultures of patient tumor samples and novel EPN cell lines.

Strikingly we found a robust expression signature implicating the interleukin-6/signal transduced and activator of transcription 3 (IL6/STAT3) pathway in the Group A tumors. Comparison of transcriptomic profiles of EPN Group A (n=17) and Group B (n=20) demonstrated significant overexpression both IL6 (19.7-fold) and STAT3 (1.6 fold) in Group A. High overexpression of STAT3 driven genes IL8 (30-fold), SOCS3 (14-fold) and BIRC3 (8.5-fold) provided additional proof of IL6/STAT3 pathway activation in Group A. Furthermore, IL6 and IL8 gene expression was shown to be significantly higher (FDR<0.05) than any other type of pediatric or adult brain tumor or normal brain, suggesting that this phenotype is unique to Group A EPN. Western blot analysis of whole tumor samples from Groups A and B showed a significantly elevated ratio of pSTAT3 to total STAT3 in the Group A tumors compared to the Group B, denoting activation of STAT3. Measurement of IL6 secretion from primary ex-vivo tumor cells, isolated by flow sorting of disaggregated surgical tumor samples, showed a significantly higher secretion by tumors cells from Group A patients compared to Group B. To further investigate the role of the IL6/STAT3 pathway, we utilized a novel EPN cell line (811) established from a multiple recurrent EPN, with the transcriptome characteristics of a Group A EPN. This cell line secretes large amounts of IL6, considerably more than glioblastoma (GBM) cell line U87 in which the IL6/STAT3 pathway has been extensively studied. This cell line induced a contact-independent polarization of myeloid cells to a pro-inflammatory phenotype. HLA-matched donor CD14+ that we treated with 811 conditioned media showed a 9.2-fold increase in IL8 secretion (p=0.027). Demonstrating the mitogenic role of STAT3 activation in EPN, we showed 811 is more sensitive to STAT3 inhibition by S31-201 (IC50 = 81uM) than breast cancer and GBM cell lines. PhosphoSTAT3 and the downstream targets of the pathway, SOCS3 and Mcl-1 are significantly reduced in a dose dependent manner in response to S31-201. S3I-201 treatment of 811 and an EPN short-term cell line were shown to cause a significant dose-dependent increase in Caspase-3/7 cleavage demonstrating apoptosis as a result of STAT3 inhibition.

To conclude: The IL6/STAT3 pathway is active in Group A EPN and is important in maintaining tumor growth in a pro-inflammatory microenvironment. Effective design of Group A-targeted immunotherapy for children with EPN may require alleviation of this potentially immunosuppressive pathway.

Citation Format: Andrea Griesinger, Andrew M. Donson, Diane Birks, Vladimir Amani, Rebecca Josephson, Kathleen Dorris, Philip Reigan, Michael Handler, Nicholas Foreman. Activation of the IL6/STAT3 pathway in childhood ependymoma is associated with a pro-inflammatory tumor microenvironment and a poor prognosis. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B69.

Advancing precision medicine through multi-omics: An integrated approach to tumor profiling

While technological breakthroughs of the last decade have greatly advanced our understanding of the cancer genome, they have also revealed the immense complexity and heterogeneity of tumors. The key to further advancing our understanding and treatment of cancer is to distinguish between genes and pathways that drive tumorigenesis (driver events) and neutral, passenger events. A growing body of evidence has shown that not all DNA-level alterations have biological implications, making it necessary to examine multiple ꞌomics levels including the transcriptome and proteome, to identify critical driver events. In this webinar, our expert panel will discuss how using a multi-omics–based approach to cancer research can advance our understanding of cancer biology as well as lead to the discovery of novel biomarkers.

Identification of targets for rational pharmacological therapy in childhood craniopharyngioma

Introduction

Pediatric adamantinomatous craniopharyngioma (ACP) is a histologically benign but clinically aggressive brain tumor that arises from the sellar/suprasellar region. Despite a high survival rate with current surgical and radiation therapy (75–95 % at 10 years), ACP is associated with debilitating visual, endocrine, neurocognitive and psychological morbidity, resulting in excheptionally poor quality of life for survivors. Identification of an effective pharmacological therapy could drastically decrease morbidity and improve long term outcomes for children with ACP.

Results

Using mRNA microarray gene expression analysis of 15 ACP patient samples, we have found several pharmaceutical targets that are significantly and consistently overexpressed in our panel of ACP relative to other pediatric brain tumors, pituitary tumors, normal pituitary and normal brain tissue. Among the most highly expressed are several targets of the kinase inhibitor dasatinib – LCK, EPHA2 and SRC; EGFR pathway targets – AREG, EGFR and ERBB3; and other potentially actionable cancer targets – SHH, MMP9 and MMP12. We confirm by western blot that a subset of these targets is highly expressed in ACP primary tumor samples.

Conclusions

We report here the first published transcriptome for ACP and the identification of targets for rational therapy. Experimental drugs targeting each of these gene products are currently being tested clinically and pre-clinically for the treatment of other tumor types. This study provides a rationale for further pre-clinical and clinical studies of novel pharmacological treatments for ACP. Development of mouse and cell culture models for ACP will further enable the translation of these targets from the lab to the clinic, potentially ushering in a new era in the treatment of ACP.

Molecular Classification of Ependymal Tumors across All CNS Compartments, Histopathological Grades, and Age Groups

Ependymal tumors across age groups are currently classified and graded solely by histopathology. It is, however, commonly accepted that this classification scheme has limited clinical utility based on its lack of reproducibility in predicting patients' outcome. We aimed at establishing a uniform molecular classification using DNA methylation profiling. Nine molecular subgroups were identified in a large cohort of 500 tumors, 3 in each anatomical compartment of the CNS, spine, posterior fossa, supratentorial. Two supratentorial subgroups are characterized by prototypic fusion genes involving RELA and YAP1, respectively. Regarding clinical associations, the molecular classification proposed herein outperforms the current histopathological classification and thus might serve as a basis for the next World Health Organization classification of CNS tumors.

Cerebral radiation necrosis in pediatric patients

Radiation necrosis is a well-described toxicity following radiation therapy in the brain. There is little data regarding the incidence of radiation necrosis in pediatric patients. We retrospectively reviewed our experience with 101 children with solid brain tumors. Radiation necrosis was diagnosed by examination of magnetic resonance imaging. Median follow-up for all patients was 13 months (range 3-51). Radiation necrosis occurred in 5% (5/101) of cases with a median time to onset of 1.2 months. In three of these children, the child was symptomatic, requiring management with steroids and bevacizumab. Radiation necrosis did not correlate with the administration of chemotherapy, age at treatment, or planning treatment volume. Our experience with pediatric patients treated with radiotherapy for solid brain tumor suggests that children may have an increased likelihood to develop radiation necrosis compared to adults.

Pilomyxoid astrocytoma treated successfully with vemurafenib

The BRAF V600E missense mutation is known to be present in a subset of central nervous system tumors. We report a patient with a BRAF V600E mutated pilomyxoid astrocytoma who failed multiple conventional chemotherapy regimens. Treatment with vemurafenib, a molecularly targeted therapy against the mutant BRAF V600E kinase, combined with vinblastine resulted in tumor regression. Furthermore, this patient experienced almost immediate progression of disease after holding vemurafenib for only 2-3 weeks, suggesting that the tumor response is vemurafenib dependent. This population of patients may benefit from targeted therapy and testing of individual tumors for BRAF mutations is justified.