Minor intron splicing is critical for survival of lethal prostate cancer

The evolutionarily conserved minor spliceosome (MiS) is required for protein expression of ∼714 minor intron-containing genes (MIGs) crucial for cell-cycle regulation, DNA repair, and MAP-kinase signaling. We explored the role of MIGs and MiS in cancer, taking prostate cancer (PCa) as an exemplar. Both androgen receptor signaling and elevated levels of U6atac, a MiS small nuclear RNA, regulate MiS activity, which is highest in advanced metastatic PCa. siU6atac-mediated MiS inhibition in PCa in vitro model systems resulted in aberrant minor intron splicing leading to cell-cycle G1 arrest. Small interfering RNA knocking down U6atac was ∼50% more efficient in lowering tumor burden in models of advanced therapy-resistant PCa compared with standard antiandrogen therapy. In lethal PCa, siU6atac disrupted the splicing of a crucial lineage dependency factor, the RE1-silencing factor (REST). Taken together, we have nominated MiS as a vulnerability for lethal PCa and potentially other cancers.

Outcomes of a radiation sparing approach in medulloblastoma by subgroup in young children: an institutional review

OBJECTIVE

To describe disease outcomes including overall survival and relapse patterns by subgroup in young pediatric patients treated for medulloblastoma with a radiation-sparing approach.

METHODS

Retrospective analysis of clinical outcomes includes treatment, relapse, and salvage therapy and late effects in children treated for medulloblastoma with a radiation-sparing approach at British Columbia Children's Hospital (BCCH) between 2000 and 2020.

RESULTS

There were 30 patients (median age 2.8 years, 60% male) treated for medulloblastoma with a radiation-sparing approach at BCCH. Subgroups included Sonic Hedgehog (SHH) (n = 14), group 3 (n = 7), group 4 (n = 6), and indeterminate status (n = 3). Three- and 5-year event-free survival (EFS) were 49.0% (30.2-65.4%) and 42.0% (24.2-58.9%) and overall survival (OS) 66.0% (95% CI 46.0-80.1%) and 62.5% (95% CI 42.5 and 77.2%), respectively, with a median follow-up of 9.5 years. Relapse occurred in 12/25 patients following a complete response, of whom six (group 4: n = 4; group 3: n = 1; unknown: n = 1) were successfully salvaged with craniospinal axis (CSA) RT and remain alive at a median follow-up of 7 years. Disease/treatment-related morbidity included endocrinopathies (n = 8), hearing loss n = 16), and neurocognitive abnormalities (n = 9).

CONCLUSIONS

This radiation sparing treatment approach for young patients with medulloblastoma resulted in a durable cure in most patients with SHH subgroup medulloblastoma. In those patients with groups 3 and 4 medulloblastoma, relapse rates were high; however, most group 4 patients were salvaged with RT.

PI5P4Kα supports prostate cancer metabolism and exposes a survival vulnerability during androgen receptor inhibition

Phosphatidylinositol (PI)regulating enzymes are frequently altered in cancer and have become a focus for drug development. Here, we explore the phosphatidylinositol-5-phosphate 4-kinases (PI5P4K), a family of lipid kinases that regulate pools of intracellular PI, and demonstrate that the PI5P4Kα isoform influences androgen receptor (AR) signaling, which supports prostate cancer (PCa) cell survival. The regulation of PI becomes increasingly important in the setting of metabolic stress adaptation of PCa during androgen deprivation (AD), as we show that AD influences PI abundance and enhances intracellular pools of PI-4,5-P2. We suggest that this PI5P4Kα-AR relationship is mitigated through mTORC1 dysregulation and show that PI5P4Kα colocalizes to the lysosome, the intracellular site of mTORC1 complex activation. Notably, this relationship becomes prominent in mouse prostate tissue following surgical castration. Finally, multiple PCa cell models demonstrate marked survival vulnerability following stable PI5P4Kα inhibition. These results nominate PI5P4Kα as a target to disrupt PCa metabolic adaptation to castrate resistance.

Beyond PI3Ks: targeting phosphoinositide kinases in disease

Lipid phosphoinositides are master regulators of almost all aspects of a cell's life and death and are generated by the tightly regulated activity of phosphoinositide kinases. Although extensive efforts have focused on drugging class I phosphoinositide 3-kinases (PI3Ks), recent years have revealed opportunities for targeting almost all phosphoinositide kinases in human diseases, including cancer, immunodeficiencies, viral infection and neurodegenerative disease. This has led to widespread efforts in the clinical development of potent and selective inhibitors of phosphoinositide kinases. This Review summarizes our current understanding of the molecular basis for the involvement of phosphoinositide kinases in disease and assesses the preclinical and clinical development of phosphoinositide kinase inhibitors.

Clinically Tractable Outcome Prediction of non-WNT/non-SHH Medulloblastoma Based on TPD52 Immunohistochemistry in a Multicohort Study

PURPOSE

International consensus and the 2021 WHO classification recognize eight molecular subgroups among non-WNT/non-SHH (Group 3/4) medulloblastoma, representing ~60% of tumors. However, very few clinical centers worldwide possess the technical capabilities to determine DNA-methylation profiles or other molecular parameters of high-risk for Group 3/4 tumors. As a result, biomarker-driven risk stratification and therapy assignment constitutes a major challenge in medulloblastoma research. Here, we identify an immunohistochemistry (IHC) marker as a clinically tractable method for improved medulloblastoma risk stratification.

EXPERIMENTAL DESIGN

We bioinformatically analyzed published medulloblastoma transcriptomes and proteomes identifying as a potential biomarker TPD52, whose IHC prognostic value was validated across three Group 3/4 medulloblastoma clinical cohorts (n = 387) treated with conventional therapies.

RESULTS

TPD52 IHC positivity represented a significant independent predictor of early relapse and death for Group 3/4 medulloblastoma (HRs between 3.67-26.7 [95% CIs between 1.00-706.23], p = 0.05, 0.017 and 0.0058). Cross-validated survival models incorporating TPD52 IHC with clinical features outperformed existing state-of-the-art risk stratification schemes, and reclassified ~50% of patients into more appropriate risk categories. Finally, TPD52 immunopositivity was a predictive indicator of poor response to chemotherapy (HR 12.66 [95% CI 3.53-45.40], p < 0.0001), suggesting important implication for therapeutic choices.

CONCLUSIONS

The current study redefines the approach to risk stratification in Group 3/4 medulloblastoma in global practice. Since integration of TPD52 IHC in classification algorithms significantly improved outcome prediction, this test could be rapidly adopted for risk stratification on a global scale, independently of advanced but technically challenging molecular profiling techniques.

Histologic Correlates of Molecular Group 4 Pediatric Medulloblastoma: A Retrospective Canadian Review

INTRODUCTION

The World Health Organization currently classifies medulloblastoma (MB) into four molecular groups (WNT, SHH, Group 3 and Group 4) and four histologic subtypes (classic, desmoplastic nodular, MB with extensive nodularity, and large cell/anaplastic). "Classic" MB is the most frequent histology, but unfortunately it does not predict molecular group or patient outcome. While MB may exhibit additional histologic features outside of the traditional WHO subtypes, the clinical significance of such features, in a molecular context, is unclear.

METHODS

The clinicopathologic features of 120 pediatric MB were reviewed in the context of NanoString molecular grouping. Each case was evaluated for five ancillary histologic features, including: nodularity without desmoplasia (i.e., "biphasic", B-MB), rhythmic palisades, and focal anaplasia. Molecular and histological features were statistically correlated to clinical outcome using Chi-square, log-rank, and multivariate Cox regression analysis.

RESULTS

While B-MB (N = 32) and rhythmic palisades (N = 12) were enriched amongst non-WNT/SHH MB (especially Group 4), they were not statistically associated with outcome. In contrast, focal anaplasia (N = 12) was not associated with any molecular group, but did predict unfavorable outcome.

CONCLUSION

These data nominate B-MB as a surrogate marker of Groups 3 and particularly 4 MB, which may earmark a clinically significant subset of cases.

EMBR-21. CLINICALLY TRACTABLE OUTCOME PREDICTION OF GROUP 3/4 MEDULLOBLASTOMA BASED ON TPD52 IMMUNOHISTOCHEMISTRY: A MULTICOHORT STUDY

Background

International consensus and the 2021 WHO classification recognize eight molecular subtypes among Group 3/4 medulloblastoma (representing ~60% of tumors). However, very few clinical centers worldwide possess the technical capabilities to determine DNA-methylation patterns or other molecular parameters of high-risk for Group 3/4 tumors. As a result, biomarker-driven risk stratification and therapy assignment constitutes a major challenge in medulloblastoma research. Here, we identify an immunohistochemistry (IHC) marker as a clinically tractable method for improved medulloblastoma risk-stratification.

Patients and Methods

We bioinformatically analyzed published medulloblastoma transcriptomes and proteomes identifying as a potential biomarker TPD52, whose IHC prognostic value was validated across three Group 3/4 medulloblastoma clinical cohorts (n = 387) treated with conventional therapies. Risk stratification and prediction capability were computed utilizing uni- and multivariate survival analysis. Newly developed risk classifiers including TPD52 IHC were compared to state-of-the-art risk stratification schemes in terms of prediction error, area under the time-dependent receiver operating characteristic (ROC) curves and C-statistic. Biomarker-driven prognostic stratification models identified were cross validated in different cohorts.

Results

TPD52 IHC positivity represents a significant independent predictor of early relapse and death for Group 3/4 medulloblastoma (HRs between 3.67–26.7 [95% CIs between 1.00–706.23], p = 0.05, 0.017 and 0.0058). Cross-validated survival models incorporating TPD52 IHC with clinical features outperformed existing disease risk-stratification schemes, and reclassified ~50% of patients into more appropriate risk categories. Finally, TPD52 immunopositivity is a predictive indicator of poor response to chemotherapy (HR 12.66 [95% CI 3.53–45.40], p < 0.0001), suggesting important implication for therapeutic choices.

Conclusion

The current study redefines the approach to risk-stratification in Group 3/4 medulloblastoma. Integration of TPD52 IHC in classification algorithms significantly improves outcome prediction and can be rapidly adopted for risk stratification on a global scale, independently of advanced but technically challenging molecular profiling techniques.

PI5P4Ks drive metabolic homeostasis through peroxisome-mitochondria interplay

PI5P4Ks are a class of phosphoinositide kinases that phosphorylate PI-5-P to PI-4,5-P₂. Distinct localization of phosphoinositides is fundamental for a multitude of cellular functions. Here, we identify a role for peroxisomal PI-4,5-P₂ generated by the PI5P4Ks in maintaining energy balance. We demonstrate that PI-4,5-P₂ regulates peroxisomal fatty acid oxidation by mediating trafficking of lipid droplets to peroxisomes, which is essential for sustaining mitochondrial metabolism. Using fluorescent-tagged lipids and metabolite tracing, we show that loss of the PI5P4Ks significantly impairs lipid uptake and β-oxidation in the mitochondria. Further, loss of PI5P4Ks results in dramatic alterations in mitochondrial structural and functional integrity, which under nutrient deprivation is further exacerbated, causing cell death. Notably, inhibition of the PI5P4Ks in cancer cells and mouse tumor models leads to decreased cell viability and tumor growth, respectively. Together, these studies reveal an unexplored role for PI5P4Ks in preserving metabolic homeostasis, which is necessary for tumorigenesis.

Prostate Power Play: Does Pik3ca Accelerate Pten-Deficient Cancer Progression?

<b/> PI3K pathway alterations are frequently recurrent in metastatic prostate cancer and are associated with the development of currently incurable castration-resistant disease. Candidate inhibitors that target single PI3K pathway members lack efficacy as demonstrated in multiple clinical trials. In this issue, Pearson and colleagues examine the functional importance of co-occurring PIK3CA and PTEN aberrations using a novel mouse model and demonstrate a synergistic acceleration of tumorigenesis that may be responsible for de novo metastatic prostate cancer. Cancer Discov; 8(6); 682-5. ©2018 AACRSee related article by Pearson et al., p. 764.

Abstract A078: Towards understanding noncanonical phosphatidylinositol kinases in the maintenance of prostate metabolism

An estimated 1 in 7 men will develop prostate cancer (PCa) with many progressing to advanced castrate-resistant disease. Unlike other tissue types, normal prostate cell growth and development is heavily dependent on the androgen receptor (AR) signaling pathway. While the introduction of novel AR antagonists for clinical treatment has improved outcomes, most castration-resistant prostate cancer (CRPC) patients ultimately develop resistance to these therapies. A need exists to better understand the mechanisms that control the transition of prostate cells from a hormone-dependent to castrate-resistant state.

Androgens strongly influence the metabolic state of PCa cells to favor sustained cellular growth. We hypothesize there are effectors working in conjunction with AR to coordinate alterations to androgen-dependent metabolism that are linchpins in the orchestration of the transition to CRPC. Leading candidates are members of phosphoinositol (PI) pathways, which have a high frequency of alteration in PCa (i.e phosphoinositide 3-kinase (PI3K)). Herein we explore a family of poorly understood lipid kinases called the type II phosphatidylinositol-5-phosphate 4-kinases (PI5P4Ks) and predict them to be critical regulators of cancer cell survival. PI5P4Ks are druggable targets that act by phosphorylating the lipid phosphatidylinositol-5-phosphate (PI 5-P) at the 4 position of the inositol ring to generate phosphatidylinositol-4,5-bisphosphate (PI-4,5-P2; PIP2). We implicate the three PI5P4K isoforms (PI5P4Kα, PI5P4Kβ, and PI5P4Kγ) encoded by the genes PIP4K2A, B, and C, to be important regulators of cancer metabolism that play a role in the maintenance of prostate biology and oncogenesis.

Analysis of transcript data revealed expression of PIP4K2A, B, and C in primary PCa patient samples, which was correlated with an AR activation gene signature and hotspot tumor suppressor deletion. As well, isoform expression was assessed for differential expression in relation to an integrated neuroendocrine prostate cancer mRNA score (TCGA; n=333). PI5P4Kα and PI5P4Kβ protein was detected in primary and advanced prostate cancer using optimized antibodies of patient tissue TMAs (n= 72). Using in vitro LNCaP cell models, siRNA knockdown systems were tested to evaluate the molecular consequence of targeting PIP4K2A and PIP4K2B in androgen-dependent systems. Stable knockdown using fluorescently labeled lentiviral shRNA constructs significantly reduced proliferation of shPIP4K2 treated cells. As well, we have produced a prostate-specific PI5P4K knockout mouse model by expressing probasin-driven Cre in a homozygous 129/SvEv Pip4k2aflx/flx murine strain. Finally, implementation of a discovery-based metabolomic platform (Metabolon HD4) was used to profile the overall shift in metabolite species that results from downregulating the expression of PIP4K2A in androgen-dependent cell models.

In summary, we have developed novel insights into the role of a family of noncanonical PI kinases in prostate biology. There are a growing number of PI3K/AKT inhibitors being tested in combination with androgen deprivation therapy in clinical trials, but there is still almost nothing known about the potential crosstalk of the greater PI kinase network. These data convincingly implicate a fundamental role for PI5P4Ks in PCa androgen signaling and metabolism, as well as lay the foundation of phenotypic understanding of what PI5P4K is responsible for in the prostate.

Citation Format: Joanna Triscott, Matteo Benelli, Verena Sailer, Davide Prandi, Brooke Emerling, Francesca Demichelis, Lewis Cantley, Mark A. Rubin. Towards understanding noncanonical phosphatidylinositol kinases in the maintenance of prostate metabolism [abstract]. In: Proceedings of the AACR Special Conference: Prostate Cancer: Advances in Basic, Translational, and Clinical Research; 2017 Dec 2-5; Orlando, Florida. Philadelphia (PA): AACR; Cancer Res 2018;78(16 Suppl):Abstract nr A078.

Personalized In Vitro and In Vivo Cancer Models to Guide Precision Medicine

Precision medicine is an approach that takes into account the influence of individuals' genes, environment, and lifestyle exposures to tailor interventions. Here, we describe the development of a robust precision cancer care platform that integrates whole-exome sequencing with a living biobank that enables high-throughput drug screens on patient-derived tumor organoids. To date, 56 tumor-derived organoid cultures and 19 patient-derived xenograft (PDX) models have been established from the 769 patients enrolled in an Institutional Review Board-approved clinical trial. Because genomics alone was insufficient to identify therapeutic options for the majority of patients with advanced disease, we used high-throughput drug screening to discover effective treatment strategies. Analysis of tumor-derived cells from four cases, two uterine malignancies and two colon cancers, identified effective drugs and drug combinations that were subsequently validated using 3-D cultures and PDX models. This platform thereby promotes the discovery of novel therapeutic approaches that can be assessed in clinical trials and provides personalized therapeutic options for individual patients where standard clinical options have been exhausted.Significance: Integration of genomic data with drug screening from personalized in vitro and in vivo cancer models guides precision cancer care and fuels next-generation research. Cancer Discov; 7(5); 462-77. ©2017 AACR.See related commentary by Picco and Garnett, p. 456This article is highlighted in the In This Issue feature, p. 443.

Concise review: bullseye: targeting cancer stem cells to improve the treatment of gliomas by repurposing disulfiram

Cancer stem cells (CSCs) are thought to be at the root of cancer recurrence because they resist conventional therapies and subsequently reinitiate tumor cell growth. Thus, targeting CSCs could be the bullseye to successful cancer therapeutics in the future. Brain tumors are some of the most challenging types of cancer to treat and the median survival following the initial diagnosis is 12-18 months. Among the different types of brain tumors, glioblastoma (GBM) is considered the most aggressive and remains extremely difficult to treat. Despite surgery, radiation, and chemotherapy, most patients develop refractory disease. Temozolomide (TMZ) is a chemotherapy used to treat GBM however resistance develops in most patients. The underlying mechanisms for TMZ resistance (TMZ-resistant) involve the expression of DNA repair gene O(6)-methylguanine-DNA methyltransferase. CSC genes such as Sox-2, BMI-1, and more recently Y-box binding protein-1 also play a role in resistance. In order to develop novel therapies for GBM, libraries of small interfering RNAs and off-patent drugs have been screened. Over the past few years, several independent laboratories identified disulfiram (DSF) as an off-patent drug that kills GBM CSCs. Reportedly DSF has several modes of action including its ability to inhibit aldehyde dehydrogenases, E3 ligase, polo-like kinase 1, and NFkB. Due to the fact that GBM is a disease of heterogeneity, chemotherapy with multitargeting properties may be the way of the future. In broader terms, DSF kills CSCs from a range of different cancer types further supporting the idea of repurposing it for "target practice."

FoxG1 interacts with Bmi1 to regulate self-renewal and tumorigenicity of medulloblastoma stem cells

Brain tumors represent the leading cause of childhood cancer mortality, of which medulloblastoma (MB) is the most frequent malignant tumor. Recent studies have demonstrated the presence of several MB molecular subgroups, each distinct in terms of prognosis and predicted therapeutic response. Groups 1 and 2 are characterized by relatively good clinical outcomes and activation of the Wnt and Shh pathways, respectively. In contrast, groups 3 and 4 ("non-Shh/Wnt MBs") are distinguished by metastatic disease, poor patient outcome, and lack a molecular pathway phenotype. Current gene expression platforms have not detected brain tumor-initiating cell (BTIC) self-renewal genes in groups 3 and 4 MBs as BTICs typically comprise a minority of tumor cells and may therefore go undetected on bulk tumor analyses. Since increasing BTIC frequency has been associated with increasing tumor aggressiveness and poor patient outcome, we investigated the subgroup-specific gene expression profile of candidate stem cell genes within 251 primary human MBs from four nonoverlapping MB transcriptional databases (Amsterdam, Memphis, Toronto, Boston) and 74 NanoString-subgrouped MBs (Vancouver). We assessed the functional relevance of two genes, FoxG1 and Bmi1, which were significantly enriched in non-Shh/Wnt MBs and showed these genes to mediate MB stem cell self-renewal and tumor initiation in mice. We also identified their transcriptional regulation through reciprocal promoter occupancy in CD15+ MB stem cells. Our work demonstrates the application of stem cell data gathered from genomic platforms to guide functional BTIC assays, which may then be used to develop novel BTIC self-renewal mechanisms amenable to therapeutic targeting.

Overcoming resistance to Sonic Hedgehog inhibition by targeting p90 ribosomal S6 kinase in pediatric medulloblastoma

BACKGROUND

Molecular subtyping has allowed for the beginning of personalized treatment in children suffering from medulloblastoma (MB). However, resistance inevitably emerges against these therapies, particularly in the Sonic Hedgehog (SHH) subtype. We found that children with SHH subtype have the worst outcome underscoring the need to identify new therapeutic targets.

PROCEDURE

High content screening of a 129 compound library identified agents that inhibited SHH MB growth. Lead molecular target levels, p90 ribosomal S6 kinase (RSK) were characterized by immunoblotting and qRT-PCR. Comparisons were made to human neural stem cells (hNSC). Impact of inhibiting RSK with the small molecule BI-D1870 or siRNA was assessed in growth assays (monolayer, neurosphere, and soft agar). NanoString was used to detect RSK in a cohort of 66 patients with MB. To determine BI-D1870 pharmacokinetics/pharmacodynamics, 100 mg/kg was I.P. injected into mice and tissues were collected at various time points.

RESULTS

Daoy, ONS76, UW228, and UW426 MB cells were exquisitely sensitive to BI-D1870 but unresponsive to SHH inhibitors. Anti-tumor growth corresponded with inactivation of RSK in MB cells. BI-D1870 had no effect on hNSCs. Inhibiting RSK with siRNA or BI-D1870 suppressed growth, induced apoptosis, and sensitized cells to SHH agents. Notably, RSK expression is correlated with SHH patients. In mice, BI-D1870 was well-tolerated and crossed the blood-brain barrier (BBB).

CONCLUSIONS

RSK inhibitors are promising because they target RSK which is correlated with SHH patients as well as cause high levels of apoptosis to only MB cells. Importantly, BI-D1870 crosses the BBB, acting as a scaffold for development of more long-lived RSK inhibitors.

Personalizing the treatment of pediatric medulloblastoma: Polo-like kinase 1 as a molecular target in high-risk children

Medulloblastoma is the most common malignant brain tumor in children. This disease is heterogeneous and is composed of four subtypes of medulloblastoma [WNT, Sonic Hedgehog (SHH), Group 3, and Group 4]. An immediate goal is to identify novel molecular targets for the most aggressive forms of medulloblastoma. Polo-like kinase 1 (PLK1) is an oncogenic kinase that controls cell cycle and proliferation, making it a strong candidate for medulloblastoma treatment. In this study, pediatric medulloblastomas were subtyped in two patient cohorts (discovery cohort, n = 63 patients; validation cohort, n = 57 patients) using NanoString nCounter analysis and PLK1 mRNA was assessed. We determined that the SHH and Group 3 subtypes were independently associated with poor outcomes in children as was PLK1 using Cox regression analyses. Furthermore, we screened a library of 129 compounds in clinical trials using a model of pediatric medulloblastoma and determined that PLK1 inhibitors were the most promising class of agents against the growth of medulloblastoma. In patient-derived primary medulloblastoma isolates, the PLK1 small-molecule inhibitor BI2536 suppressed the self-renewal of cells with high PLK1 but not low PLK1 expression. PLK1 inhibition prevented medulloblastoma cell proliferation, self-renewal, cell-cycle progression, and induced apoptosis. In contrast, the growth of normal neural stem cells was unaffected by BI2536. Finally, BI2536 extended survival in medulloblastoma-bearing mice with efficacy comparable with Headstart, a standard-of-care chemotherapy regimen. We conclude that patients with medulloblastoma expressing high levels of PLK1 are at elevated risk. These preclinical studies pave the way for improving the treatment of medulloblastoma through PLK1 inhibition.

Recurrence patterns across medulloblastoma subgroups: an integrated clinical and molecular analysis

BACKGROUND

Recurrent medulloblastoma is a therapeutic challenge because it is almost always fatal. Studies have confirmed that medulloblastoma consists of at least four distinct subgroups. We sought to delineate subgroup-specific differences in medulloblastoma recurrence patterns.

METHODS

We retrospectively identified a discovery cohort of all recurrent medulloblastomas at the Hospital for Sick Children (Toronto, ON, Canada) from 1994 to 2012 (cohort 1), and established molecular subgroups using a nanoString-based assay on formalin-fixed paraffin-embedded tissues or frozen tissue. The anatomical site of recurrence (local tumour bed or leptomeningeal metastasis), time to recurrence, and survival after recurrence were assessed in a subgroup-specific manner. Two independent, non-overlapping cohorts (cohort 2: samples from patients with recurrent medulloblastomas from 13 centres worldwide, obtained between 1991 and 2012; cohort 3: samples from patients with recurrent medulloblastoma obtained at the NN Burdenko Neurosurgical Institute [Moscow, Russia] between 1994 and 2011) were analysed to confirm and validate observations. When possible, molecular subgrouping was done on tissue obtained from both the initial surgery and at recurrence.

RESULTS

Cohort 1 consisted of 30 patients with recurrent medulloblastomas; nine with local recurrences, and 21 with metastatic recurrences. Cohort 2 consisted of 77 patients and cohort 3 of 96 patients with recurrent medulloblastoma. Subgroup affiliation remained stable at recurrence in all 34 cases with available matched primary and recurrent pairs (five pairs from cohort 1 and 29 pairs from cohort 2 [15 SHH, five group 3, 14 group 4]). This finding was validated in 17 pairs from cohort 3. When analysed in a subgroup-specific manner, local recurrences in cohort 1 were more frequent in SHH tumours (eight of nine [89%]) and metastatic recurrences were more common in group 3 and group 4 tumours (17 of 20 [85%] with one WNT, p=0·0014, local vs metastatic recurrence, SHH vs group 3 vs group 4). The subgroup-specific location of recurrence was confirmed in cohort 2 (p=0·0013 for local vs metastatic recurrence, SHH vs group 3 vs group 4,), and cohort 3 (p<0·0001). Treatment with craniospinal irradiation at diagnosis was not significantly associated with the anatomical pattern of recurrence. Survival after recurrence was significantly longer in patients with group 4 tumours in cohort 1 (p=0·013) than with other subgroups, which was confirmed in cohort 2 (p=0·0075), but not cohort 3 (p=0·70).

INTERPRETATION

Medulloblastoma does not change subgroup at the time of recurrence, reinforcing the stability of the four main medulloblastoma subgroups. Significant differences in the location and timing of recurrence across medulloblastoma subgroups have potential treatment ramifications. Specifically, intensified local (posterior fossa) therapy should be tested in the initial treatment of patients with SHH tumours. Refinement of therapy for patients with group 3 or group 4 tumours should focus on metastases.

Abstract 3552: Subgroup-specific pattern of recurrence in medulloblastoma

Background: Medulloblastoma constitutes the most common malignant brain tumor of childhood. Although multimodel treatment strategies, encompassing surgery, chemotherapy, and radiation, results in up to 80% five-year overall survival, recurrent medulloblastoma is almost always uniformly fatal. Recent integrated genomic studies have shown that medulloblastoma comprises 4 clinical and biologically distinct variants. We sought to delineate subgroup-specific differences in recurrent medulloblastoma.

Methods: We identified a discovery cohort of all recurrent medulloblastomas at the Hospital for Sick Children between 1994-2012, and subgrouped cases using nanoString. Clinical details were ascertained via retrospective chart review. Our findings were confirmed through analysis of an independent validation cohort of 85 recurrences. Primary and recurrent matched pairs were evaluated where possible.

Results: Twenty-nine recurrent cases were identified, ten with a local recurrence within the tumor bed only, and 19 recurred with metastases. Notably, SHH tumors recurred more frequently in the tumor bed (8/11, 73%) whereas Group 3 and Group 4 developed with metastatic relapses more frequently (16/18, 89%; p&lt;0.01). Late recurrences were observed more commonly in Group 4 cases with a mean time to recurrence of 3.2 years compared to under two years for both SHH and Group 3 (p&lt;0.004), with a tendency to a prolonged interval to death post-recurrence in Group 4 cases (p=0.07). Spinal metastases in the absence of supratentorial metastases were observed in three non-SHH recurrences. The presence of metastases at diagnosis and histology were not predictive factors of recurrence site. In an independent validation cohort of 85 recurrences, 13 recurrences appeared in the tumor bed only of which nine were SHH and 72 recurred with metastases. Of these metastatic relapses, only three SHH tumors were observed, while 36 and 33 belonged to Group 3 or Group4 (p&lt;0.001), respectively. Strikingly, in all instances where matched primary and recurrent pairs were available, the subgroup affiliation remained stable at recurrence.

Conclusions: Significant differences in the pattern of recurrence exist across medulloblastoma subgroups. Longer surveillance periods across the entire neuro-axis may be required for Group 4 patients even in the absence of local tumor bed or supratentorial recurrence. Intensified local therapy should be considered upon initial treatment for SHH patients.

Citation Format: Vijay Ramaswamy, Marc Remke, Eric Bouffet, David Shih, Claudia Faria, Ulrich Schüller, Sri Gururangan, Roger McLendon, Nada Jabado, Adam Fontebasso, Sandra Dunn, Joanna Triscott, Cynthia Hawkins, Uri Tabori, Kari Codispoti, Roger Packer, Stefan M. Pfister, Andrey Korshunov, Michael D. Taylor. Subgroup-specific pattern of recurrence in medulloblastoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3552. doi:10.1158/1538-7445.AM2013-3552

Disulfiram, a drug widely used to control alcoholism, suppresses the self-renewal of glioblastoma and over-rides resistance to temozolomide

Glioblastomas (GBM) are associated with high rates of relapse. These brain tumors are often resistant to chemotherapies like temozolomide (TMZ) and there are very few treatment options available to patients. We recently reported that polo-like kinase-1 (PLK1) is associated with the proliferative subtype of GBM; which has the worst prognosis. In this study, we addressed the potential of repurposing disulfiram (DSF), a drug widely used to control alcoholism for the past six decades. DSF has good safety profiles and penetrates the blood-brain barrier. Here we report that DSF inhibited the growth of TMZ resistant GBM cells, (IC90=100 nM), but did not affect normal human astrocytes. At similar DSF concentrations, self-renewal was blocked by ~100% using neurosphere growth assays. Likewise the drug completely inhibited the self-renewal of the BT74 and GBM4 primary cell lines. Additionally, DSF suppressed growth and self-renewal of primary cells from two GBM tumors. These cells were resistant to TMZ, had unmethylated MGMT, and expressed high levels of PLK1. Consistent with its role in suppressing GBM growth, DSF inhibited the expression of PLK1 in GBM cells. Likewise, PLK1 inhibition with siRNA, or small molecules (BI-2536 or BI-6727) blocked growth of TMZ resistant cells. Our studies suggest that DSF has the potential to be repurposed for treatment of refractory GBM.

Polo-like kinase 1 inhibition kills glioblastoma multiforme brain tumor cells in part through loss of SOX2 and delays tumor progression in mice

Glioblastoma multiforme (GBM) ranks among the deadliest types of cancer and given these new therapies are urgently needed. To identify molecular targets, we queried a microarray profiling 467 human GBMs and discovered that polo-like kinase 1 (PLK1) was highly expressed in these tumors and that it clustered with the proliferative subtype. Patients with PLK1-high tumors were more likely to die from their disease suggesting that current therapies are inactive against such tumors. This prompted us to examine its expression in brain tumor initiating cells (BTICs) given their association with treatment failure. BTICs isolated from patients expressed 110-470 times more PLK1 than normal human astrocytes. Moreover, BTICs rely on PLK1 for survival because the PLK1 inhibitor BI2536 inhibited their growth in tumorsphere cultures. PLK1 inhibition suppressed growth, caused G(2) /M arrest, induced apoptosis, and reduced the expression of SOX2, a marker of neural stem cells, in SF188 cells. Consistent with SOX2 inhibition, the loss of PLK1 activity caused the cells to differentiate based on elevated levels of glial fibrillary acidic protein and changes in cellular morphology. We then knocked glial fibrillary acidic protein (GFAP) down SOX2 with siRNA and showed that it too inhibited cell growth and induced cell death. Likewise, in U251 cells, PLK1 inhibition suppressed cell growth, downregulated SOX2, and induced cell death. Furthermore, BI2536 delayed tumor growth of U251 cells in an orthotopic brain tumor model, demonstrating that the drug is active against GBM. In conclusion, PLK1 level is elevated in GBM and its inhibition restricts the growth of brain cancer cells.

Effect of VAL-083, a novel N7 alkylating agent, on growth of temolozomide-resistant primary adult glioblastoma multiforme (GBM) cells providing a new potential treatment option for GBM

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Background: Glioblastoma (GBM) remains one of the most difficult tumors to treat first because many new agents fail to cross the blood brain barrier (BBB), and second due to intrinsic drug resistance. Temozolomide (TMZ) is a front-line therapy for the treatment of GBM; however, it is often ineffective due to drug inactivation by O6-methylguanine-DNA methyltransferase (MGMT). Cancer stem cells (CSC) are a subpopulation of the tumor that resist therapy and give rise to relapse. Here we describe VAL-083, a novel alkylating agent that creates N7 methylation on DNA, and readily crosses the BBB. VAL-083 is currently undergoing human clinical trials in the USA in refractory GBM patients. We previously described how VAL-083 can overcome resistance associated with MGMT in cell lines, and targets brain tumor CSCs. This demonstrates that VAL-083 has the potential to surpass the standard-of-care. Methods: To provide further preclinical support for VAL-083 we examined the effect of VAL-083 on primary adult GBM cells in culture, isolated fresh following surgical resection, in cases where clinical activity of TMZ was known to be limited and high expression of MGMT had been observed. Results: VAL-083 (5uM) inhibited cell growth in these primary adult GBMs that did not show significant sensitivity to TMZ in vitro. VAL-083 also inhibited the growth of CSCs by 100% in neurosphere growth assays. Conclusions: In summary, VAL-083 demonstrates in vitro efficacy against primary adult GBM cells where TMZ has limited activity thereby further supporting the potential of VAL-083 to surpas the standard-of-care.

Abstract 811: VAL083, a novel N7 alkylating agent, surpasses temozolomide activity and inhibits cancer stem cells providing a new potential treatment option for glioblastoma multiforme

Glioblastoma (GBM) remains one of the most difficult tumors to treat in part because many new agents fail to cross the blood brain barrier (BBB) and secondly due to intrinsic drug resistance. Temozolomide (TMZ) is a front-line therapy for the treatment of GBM, however, it is often ineffective due to drug inactivation by O6-methylguanine-DNA methyltransferase (MGMT). Cancer stem cells (CSC) are a subpopulation of the tumor that resist therapy and give rise to relapse. Here we described VAL083 a novel alkylating agent that creates N7 methylation on DNA, which was initially intriguing because it crosses the BBB. We addressed how it compared to TMZ, whether it could be used to overcome MGMT-driven drug resistance and if it has activity against CSCs. Addressing these questions provides further preclinical support for VAL083, which is currently undergoing human clinical trials in the USA against refractory GBM. VAL083 inhibited U251 and SF188 cell growth in monolayer and as neurospheres better then TMZ and caused apoptosis after 72 hrs. In a 10-day colony formation assay, VAL083 (5uM) suppressed SF188 growth by ∼95%. T98G cells are classically TMZ resistant and express MGMT yet VAL083 inhibited their growth in monolayer after 72 hrs in a dose-dependent manner (IC50&lt;5 uM). VAL083 also inhibited the growth of CSCs by 100% in neurosphere growth assays. In summary, VAL083 has better in vitro efficacy than TMZ against brain tumor cells, can overcome resistance associated with MGMT, and targets brain tumor CSCs demonstrating that it has the potential to surpass the standard-of-care.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 811. doi:1538-7445.AM2012-811

YB-1 bridges neural stem cells and brain tumor-initiating cells via its roles in differentiation and cell growth

The Y-box binding protein 1 (YB-1) is upregulated in many human malignancies including glioblastoma (GBM). It is also essential for normal brain development, suggesting that YB-1 is part of a neural stem cell (NSC) network. Here, we show that YB-1 was highly expressed in the subventricular zone (SVZ) of mouse fetal brain tissues but not in terminally differentiated primary astrocytes. Conversely, YB-1 knockout mice had reduced Sox-2, nestin, and musashi-1 expression in the SVZ. Although primary murine neurospheres were rich in YB-1, its expression was lost during glial differentiation. Glial tumors often express NSC markers and tend to loose the cellular control that governs differentiation; therefore, we addressed whether YB-1 served a similar role in cancer cells. YB-1, Sox-2, musashi-1, Bmi-1, and nestin are coordinately expressed in SF188 cells and 9/9 GBM patient-derived primary brain tumor-initiating cells (BTIC). Silencing YB-1 with siRNA attenuated the expression of these NSC markers, reduced neurosphere growth, and triggered differentiation via coordinate loss of GSK3-β. Furthermore, differentiation of BTIC with 1% serum or bone morphogenetic protein-4 suppressed YB-1 protein expression. Likewise, YB-1 expression was lost during differentiation of normal human NSCs. Consistent with these observations, YB-1 expression increased with tumor grade (n = 49 cases). YB-1 was also coexpressed with Bmi-1 (Spearmans 0.80, P > 0.001) and Sox-2 (Spearmans 0.66, P > 0.001) based on the analysis of 282 cases of high-grade gliomas. These proteins were highly expressed in 10/15 (67%) of GBM patients that subsequently relapsed. In conclusion, YB-1 correlatively expresses with NSC markers where it functions to promote cell growth and inhibit differentiation.

Is telemedicine a subset of medical informatics?

Informatics has a key characteristic of a new discipline in a technically transient environment--there is no universal definition of it. This is not surprising, given its complex and diverse nature. In a broad sense informatics is the interface between developing technologies and the decision sciences, in particular clinical sciences. Telemedicine has no universally accepted definition either. Telemedicine requires the use of electronic communication networks for the transmission of information and data related to the diagnosis and treatment of, as well as education about, medical conditions. The debate ensues over whether it is or is not a subset of medical informatics. The care of the elderly diploma programme is a telemedicine project within the department of family medicine at the University of Alberta; it is a distance learning programme directed towards educating and training physicians in rural Alberta. This project provided us with the practical experience of addressing both informatics and telemedicine issues jointly.

Dilemmas in care of the elderly

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Artificial neural networks that use single-photon emission tomography to identify patients with probable Alzheimer's disease

Single-photon emission tomographic (SPET) images using technetium-99m labelled hexamethyl-propylene amine oxime were obtained from 97 patients diagnosed as having Alzheimer's disease, as well as from a comparison group of 64 normal subjects. Multiple linear regression was used to predict subject type (Alzheimer's vs comparison) using scintillation counts from 14 different brain regions as predictors. These results were disappointing: the regression equation accounted for only 33.5% of the variance between subjects. However, the same data were also used to train parallel distributed processing (PDP) networks of different sizes to classify subjects. In general, the PDP networks accounted for substantially more (up to 95%) of the variance in the data, and in many instances were able to distinguish perfectly between the two subjects. These results suggest two conclusions. First, SPET images do provide sufficient information to distinguish patients with Alzheimer's disease from a normal comparison group. Second, to access this diagnostic information, it appears that one must take advantage of the ability of PDP networks to detect higher-order nonlinear relationships among the predictor variables.

Cerebral aetiology of urinary urge incontinence in elderly people

We have examined 73 elderly incontinent patients (mean age 79 years) and 27 continent subjects (mean age 78 years) of similar cognitive status. Among the incontinent patients, 20 were shown objectively to have urge incontinence with normal bladder filling sensation, 14 had objectively demonstrated urge incontinence with reduced bladder sensation, and 39 had other types of incontinence. We compared cognitive function (by Mini-mental State Examination: MMSE) and regional brain perfusion (by SPECT scanning) in these four groups. Patients with objectively demonstrated urge incontinence and reduced bladder sensation stood out as being different from the rest: their mean MMSE score was significantly lower than that of any of the other three groups; perfusion of the frontal cortex was significantly poorer than that in the continent and other incontinent groups; global cortical perfusion was significantly poorer than in the other incontinence groups. This was not found in patients with urge incontinence and normal bladder sensation. The observations support the hypothesis that in elderly people urge incontinence with reduced bladder sensation can be a consequence of cortical neuropathy, especially in the frontal lobes.