Combined MYC and P53 defects emerge at medulloblastoma relapse and define rapidly progressive, therapeutically targetable disease

Pediatric Targeted Therapy: Clinical Feasibility of Personalized Diagnostics in Children with Relapsed and Progressive Tumors

The "pediatric targeted therapy" (PTT) program aims to identify the presence and activity of druggable targets and evaluate the clinical benefit of a personalized treatment approach in relapsed or progressive tumors on an individual basis. 10 markers (HDAC2, HR23B, p-AKT, p-ERK, p-S6, p-EGFR, PDGFR-alpha/beta, p53 and BRAFV600E) were analyzed by immunohistochemistry. Pediatric patients with tumors independent of the histological diagnosis, with relapse or progression after treatment according to standard protocols were included. N = 61/145 (42%) cases were eligible for analysis between 2009 and 2013, the most common entities being brain tumors. Immunohistochemical stainings were evaluated by the H-Score (0-300). In 93% of the cases potentially actionable targets were identified. The expressed or activated pathways were histone deacetylase (HDACs; 83.0% of cases positive), EGFR (87.2%), PDGFR (75.9%), p53 (50.0%), MAPK/ERK (43.3%) and PI3K/mTOR (36.1%). Follow-up revealed partial or full implementation of PTT results in treatment decision-making in 41% of the cases. Prolonged disease stabilization responses in single cases were noticed, however, response rates did not differ from cases treated with other modalities. Further studies evaluating the feasibility and clinical benefit of personalized diagnostic approaches using paraffin material are warranted.

Biomarker-driven stratification of disease-risk in non-metastatic medulloblastoma: Results from the multi-center HIT-SIOP-PNET4 clinical trial

PURPOSE

To improve stratification of risk-adapted treatment for non-metastatic (M0), standard-risk medulloblastoma patients by prospective evaluation of biomarkers of reported biological or prognostic significance, alongside clinico-pathological variables, within the multi-center HIT-SIOP-PNET4 trial.

METHODS

Formalin-fixed paraffin-embedded tumor tissues were collected from 338 M0 patients (>4.0 years at diagnosis) for pathology review and assessment of the WNT subgroup (MBWNT) and genomic copy-number defects (chromosome 17, MYC/MYCN, 9q22 (PTCH1) and DNA ploidy). Clinical characteristics were reviewed centrally.

RESULTS

The favorable prognosis of MBWNT was confirmed, however better outcomes were observed for non-MBWNT tumors in this clinical risk-defined cohort compared to previous disease-wide clinical trials. Chromosome 17p/q defects were heterogeneous when assessed at the cellular copy-number level, and predicted poor prognosis when they occurred against a diploid (ch17(im)/diploid(cen)), but not polyploid, genetic background. These factors, together with post-surgical tumor residuum (R+) and radiotherapy delay, were supported as independent prognostic markers in multivariate testing. Notably, MYC and MYCN amplification were not associated with adverse outcome. In cross-validated survival models derived for the clinical standard-risk (M0/R0) disease group, (ch17(im)/diploid(cen); 14% of patients) predicted high disease-risk, while the outcomes of patients without (ch17(im)/diploid(cen)) did not differ significantly from MBWNT, allowing re-classification of 86% as favorable-risk.

CONCLUSIONS

Biomarkers, established previously in disease-wide studies, behave differently in clinically-defined standard-risk disease. Distinct biomarkers are required to assess disease-risk in this group, and define improved risk-stratification models. Routine testing for specific patterns of chromosome 17 imbalance at the cellular level, and MBWNT, provides a strong basis for incorporation into future trials.

Co-delivery of small molecule hedgehog inhibitor and miRNA for treating liver fibrosis

In liver fibrosis, secretion of growth factors and hedgehog (Hh) ligands by hepatic parenchyma upon repeated insults results in transdifferentiation of quiescent hepatic stellate cells (HSCs) into active myofibroblasts which secrete excessive amounts of extracellular matrix (ECM) proteins. An Hh inhibitor GDC-0449 and miR-29b1 can play an important role in treating liver fibrosis by inhibiting several pro-fibrotic genes. Our in-silico analysis indicate that miR-29b1 targets several profibrotic genes like collagen type I & IV, c-MYC, PDGF-β and PI3K/AKT which are upregulated in liver fibrosis. Common bile duct ligation (CBDL) resulted in an increase in Ptch-1, Shh and Gli-1 expression. miR-29b1 and GDC-0449 were co-formulated into micelles using methoxy poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate-graft-dodecanol-graft-tetraethylenepentamine) (mPEG-b-PCC-g-DC-g-TEPA) copolymer, and injected systemically into CBDL mice. High concentrations of GDC-0449 and miR-29b1 were delivered to liver cells as determined by in situ liver perfusion at 30 min post systemic administration of their micelle formulation. There was a significant decrease in collagen deposition in the liver and serum injury markers, leading to improvement in liver morphology. Combination therapy was more effective in providing hepatoprotection, lowering liver injury related serum enzyme levels, reducing fibrotic protein markers such as collagen, α-SMA, FN-1 and p-AKT compared to monotherapy. In conclusion, inhibition of Hh pathway and restoration of miR-29b1 have the potential to act synergistically in treating CBDL-induced liver fibrosis in mice.

Molecular and in vivo characterization of cancer-propagating cells derived from MYCN-dependent medulloblastoma

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. While the pathways that are deregulated in MB remain to be fully characterized, amplification and/or overexpression of the MYCN gene, which is has a critical role in cerebellar development as a regulator of neural progenitor cell fate, has been identified in several MB subgroups. Phenotypically, aberrant expression of MYCN is associated with the large-cell/anaplastic MB variant, which accounts for 5-15% of cases and is associated with aggressive disease and poor clinical outcome. To better understand the role of MYCN in MB in vitro and in vivo and to aid the development of MYCN-targeted therapeutics we established tumor-derived neurosphere cell lines from the GTML (Glt1-tTA/TRE-MYCN-Luc) genetically engineered mouse model. A fraction of GTML neurospheres were found to be growth factor independent, expressed CD133 (a marker of neural stem cells), failed to differentiate upon MYCN withdrawal and were highly tumorigenic when orthotopically implanted into the cerebellum. Principal component analyzes using single cell RNA assay data suggested that the clinical candidate aurora-A kinase inhibitor MLN8237 converts GTML neurospheres to resemble non-MYCN expressors. Correlating with this, MLN8237 significantly extended the survival of mice bearing GTML MB allografts. In summary, our results demonstrate that MYCN plays a critical role in expansion and survival of aggressive MB-propagating cells, and establish GTML neurospheres as an important resource for the development of novel therapeutic strategies.