Clinical Efficacy of ONC201 in H3K27M-Mutant Diffuse Midline Gliomas Is Driven by Disruption of Integrated Metabolic and Epigenetic Pathways

Patients with H3K27M-mutant diffuse midline glioma (DMG) have no proven effective therapies. ONC201 has recently demonstrated efficacy in these patients, but the mechanism behind this finding remains unknown. We assessed clinical outcomes, tumor sequencing, and tissue/cerebrospinal fluid (CSF) correlate samples from patients treated in two completed multisite clinical studies. Patients treated with ONC201 following initial radiation but prior to recurrence demonstrated a median overall survival of 21.7 months, whereas those treated after recurrence had a median overall survival of 9.3 months. Radiographic response was associated with increased expression of key tricarboxylic acid cycle-related genes in baseline tumor sequencing. ONC201 treatment increased 2-hydroxyglutarate levels in cultured H3K27M-DMG cells and patient CSF samples. This corresponded with increases in repressive H3K27me3 in vitro and in human tumors accompanied by epigenetic downregulation of cell cycle regulation and neuroglial differentiation genes. Overall, ONC201 demonstrates efficacy in H3K27M-DMG by disrupting integrated metabolic and epigenetic pathways and reversing pathognomonic H3K27me3 reduction.

SIGNIFICANCE

The clinical, radiographic, and molecular analyses included in this study demonstrate the efficacy of ONC201 in H3K27M-mutant DMG and support ONC201 as the first monotherapy to improve outcomes in H3K27M-mutant DMG beyond radiation. Mechanistically, ONC201 disrupts integrated metabolic and epigenetic pathways and reverses pathognomonic H3K27me3 reduction. This article is featured in Selected Articles from This Issue, p. 2293.

Receptor tyrosine kinase (RTK) targeting in pediatric high-grade glioma and diffuse midline glioma: Pre-clinical models and precision medicine

Pediatric high-grade glioma (pHGG), including both diffuse midline glioma (DMG) and non-midline tumors, continues to be one of the deadliest oncologic diagnoses (both henceforth referred to as “pHGG”). Targeted therapy options aimed at key oncogenic receptor tyrosine kinase (RTK) drivers using small-molecule RTK inhibitors has been extensively studied, but the absence of proper in vivo modeling that recapitulate pHGG biology has historically been a research challenge. Thankfully, there have been many recent advances in animal modeling, including Cre-inducible transgenic models, as well as intra-uterine electroporation (IUE) models, which closely recapitulate the salient features of human pHGG tumors. Over 20% of pHGG have been found in sequencing studies to have alterations in platelet derived growth factor-alpha (PDGFRA), making growth factor modeling and inhibition via targeted tyrosine kinases a rich vein of interest. With commonly found alterations in other growth factors, including FGFR, EGFR, VEGFR as well as RET, MET, and ALK, it is necessary to model those receptors, as well. Here we review the recent advances in murine modeling and precision targeting of the most important RTKs in their clinical context. We additionally provide a review of current work in the field with several small molecule RTK inhibitors used in pre-clinical or clinical settings for treatment of pHGG.

Everolimus improves the efficacy of dasatinib in PDGFRα-driven glioma

Pediatric and adult high-grade gliomas (HGGs) frequently harbor PDGFRA alterations. We hypothesized that cotreatment with everolimus may improve the efficacy of dasatinib in PDGFRα-driven glioma through combinatorial synergism and increased tumor accumulation of dasatinib. We performed dose-response, synergism, P-glycoprotein inhibition, and pharmacokinetic studies in in vitro and in vivo human and mouse models of HGG. Six patients with recurrent PDGFRα-driven glioma were treated with dasatinib and everolimus. We found that dasatinib effectively inhibited the proliferation of mouse and human primary HGG cells with a variety of PDGFRA alterations. Dasatinib exhibited synergy with everolimus in the treatment of HGG cells at low nanomolar concentrations of both agents, with a reduction in mTOR signaling that persisted after dasatinib treatment alone. Prolonged exposure to everolimus significantly improved the CNS retention of dasatinib and extended the survival of PPK tumor-bearing mice (mutant TP53, mutant PDGFRA, H3K27M). Six pediatric patients with glioma tolerated this combination without significant adverse events, and 4 patients with recurrent disease (n = 4) had a median overall survival of 8.5 months. Our results show that the efficacy of dasatinib treatment of PDGFRα-driven HGG was enhanced with everolimus and suggest a promising route for improving targeted therapy for this patient population.

Abstract 4037: The pattern of extracellular vesicles secretion and their role in head and neck squamous cell carcinoma

Head and Neck Squamous Cell Carcinoma (HNSCC) is a keratinocytic neoplasm that is considered to be one of the six most common malignancies worldwide. It represents more than 90% of all cancers that occur throughout the upper aerodigestive tract. Unfortunately, HNSCC is still related to a high rate of morbidity and mortality. The poor prognosis of HNSCC shows remarkable association with local invasion and subsequent metastasis. Recent evidences have shown that the tumor development and the metastatic process are supported by extracellular vesicles (EVs), which are released from the tumor cells to the blood or lymphatic system. The molecular mechanisms involved in EVs biogenesis and secretion are, however, poorly understood. Herein, we sought to evaluate the pathways that govern EVs formation and the crucial mechanism that regulates EVs’ release by HNSCC cells. In addition, we tried to recognize the role of HNSCC EVs upon dysplastic keratinocytes and microenvironment cells such as endothelial cells. EVs derived from three HNSCC cell lines (SCC-9, Cal27 and FaDu) were isolated by ultracentrifugation and quantified using Nanoparticle Tracking Analysis (NTA - NanoSight®). A screen targeting for the components of EVs’ biogenesis in the HNSCC cell lines through western blotting was also performed and lysosomal compartment was followed by immunofluorescence in live cells. Finally, the invasion and angiogenic potential of dysplastic keratinocytes (DOK cell line) and endothelial cells (HUVEC cell line) were evaluated, respectively, after treatment with EVs secreted by HNSCC cell lines. Comparing the three cell lines, FaDu cells presented higher expression of proteins responsible for EVs formation (p<0.05), such as Flotilin-1, Tsg101, VPS36 and also Rab7, a small GTPase that directs vesicles to lysosomes. However, FaDu cells secreted less EVs than SCC-9 and Cal27, as well as it showed lower levels of Vps4, required for formation of multivesicular bodies. Immunofluorescence experiments showed the presence of numerous perinuclear clusters positive for LAMP-1 (lysosome marker) in FaDu and Cal27 cells, while SCC-9 showed LAMP1-positive organelles dispersed throughout its cytoplasm. These findings indicate that the majority of EVs formed by FaDu cells can be driven to lysosome compartment instead of being released to the extracellular milieu. Interestingly, when DOK and HUVEC cells were treated with the same number of EVs derived from HNSCC cell lines, SCC-9 EVs enhanced the invasion and angiogenic potential of keratinocytes and endothelial cells, respectively. Taken together, our data highlights a possible role for Rab7 protein in the negative regulation of EVs secretion by HNSCC cell lines. Moreover, the results provided by the in vitro functional assays suggest the clinical importance of regulating EVs secretion for the controlling of HNSCC tumor aggressivenes.

Citation Format: Fernanda S. Giudice, Bruna R. Rodrigues, Tonielli C. Lacerda, Rodrigo T. Cartaxo, Antuani R. Baptistella, Marcos V. S. Dias, Luiz P. Kowalski, Vilma R. Martins. The pattern of extracellular vesicles secretion and their role in head and neck squamous cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4037. doi:10.1158/1538-7445.AM2015-4037

Crosstalk between kinases, phosphatases and miRNAs in cancer

Reversible phosphorylation of proteins, performed by kinases and phosphatases, is the major post translational protein modification in eukaryotic cells. This intracellular event represents a critical regulatory mechanism of several signaling pathways and can be related to a vast array of diseases, including cancer. Cancer research has produced increasing evidence that kinase and phosphatase activity can be compromised by mutations and also by miRNA silencing, performed by small non-coding and endogenously produced RNA molecules that lead to translational repression. miRNAs are believed to target about one-third of human mRNAs while a single miRNA may target about 200 transcripts simultaneously. Regulation of the phosphorylation balance by miRNAs has been a topic of intense research over the last years, spanning topics going as far as cancer aggressiveness and chemotherapy resistance. By addressing recent studies that have shown miRNA expression patterns as phenotypic signatures of cancers and how miRNA influence cellular processes such as apoptosis, cell cycle control, angiogenesis, inflammation and DNA repair, we discuss how kinases, phosphatases and miRNAs cooperatively act in cancer biology.