Search

Up to 80% of meningiomas are classified as clinically low-grade, however, a subset of these ‘benign’ cases will ultimately recur and require additional treatment. The role of molecular subgroup in meningioma recurrence has not been thoroughly investigated, despite correlations of this variable with other clinical features. Indeed, epigenetic and transcriptional evidence supports involvement of distinct oncogenic processes within each subgroup, and as shown in other brain tumors, this may result in divergent clinical courses. In the present study, we classified 429 meningiomas into six established molecular subgroups based on genomic driver, and investigated associations of each subgroup with tumor recurrence. At two years of follow-up, we observed differences in progression free survival curves among relatively aggressive (NF2-loss, PI3K-activated, Hedgehog-activated) and quiescent (KLF4-mutant, SMARCB1-mutant, POLR2A-mutant) subgroups (log rank p = 4.3 x 10-2), with the former group recurring at a rate 14x higher. We found PI3K-activated meningiomas recurred significantly earlier than other subgroups (average time to recurrence of 19.2 months; p = 2.2 x 10-2), though we observed an intermediate long-term outcome relative to the Hedgehog and NF2 lesions. Overall, Hedgehog tumors recurred significantly more frequently than other low-grade meningiomas (adj. p = 3.1 x 10-2), and this subgroup was found to be an independent predictor of progression free survival using cox proportional hazards modelling (HR = 3.1; p = 2.4 x 10-2). By contrast, the aggressiveness of NF2 meningiomas was found to depend upon gender, WHO grade, and elevated Ki-67 index, and this subgroup was not an independent prognostic predictor. Our results suggest molecular subgroup is predictive of recurrence in low-grade meningiomas, and thus is an important consideration in post-operative management decisions. Routine genotyping to detect Hedgehog and PI3K mutant lesions may identify patients that would benefit from closer follow-up and consideration of adjuvant therapies.

BACKGROUND Medulloblastoma is an aggressive pediatric brain tumor that is associated with misactivation of the Hedgehog (HH) pathway. Our lab has shown that CDK6, a critical activator of the cell cycle, is a direct transcriptional target of oncogenic HH signaling, and that inhibiting CDK6 blocks the growth of HH-associated medulloblastoma in mice. A clinical trial exploring the efficacy of CDK6 inhibition in medulloblastoma patients is underway, but prior attempts to target the HH pathway in medulloblastoma have been encumbered by resistance to molecular monotherapy. Thus, we sought to identify mechanisms of resistance to CDK6 inhibition in HH-associated medulloblastoma. METHODS We performed orthogonal CRISPR and CRISPR interference screens in HH-associated medulloblastoma cells treated with pharmacologic inhibitors of CDK6 in vitro, and RNA-sequencing of HH-associated medulloblastomas with genetic deletion of CDK6 in vivo. Mechanistic and functional validation of resistance pathways was performed using CRISPR interference, immunoblotting, immunofluorescence, genetics, and pharmacology. Lipid quantification was carried out by ultra-high performance liquid chromatography-tandem mass spectrometry. RESULTS Our results reveal that decreased ribosomal protein expression underlies resistance to CDK6 inhibition in HH-associated medulloblastoma, leading to endoplasmic reticular (ER) stress and activation of the unfolded protein response (UPR). We show that ER stress and the UPR increase the activity of enzymes producing Smoothened-activating sterol lipids that sustain oncogenic HH signaling in medulloblastoma despite CDK6 inhibition. These discoveries suggest that combination molecular therapy against CDK6 and HSD11ß2, an enzyme producing Smoothened-activating lipids, may be an effective treatment for HH-associated medulloblastoma. In support of this hypothesis, we demonstrate that concurrent genetic deletion or pharmacological inhibition of CDK6 and HSD11ß2 additively blocks the growth of multiple models of HH-associated medulloblastoma in mice. CONCLUSIONS Smoothened-activating lipid biosynthesis underlies resistance to CDK6 inhibition in HH-associated medulloblastoma, revealing a novel combination therapy to treat the most common malignant brain tumor in children.

Breast cancer is the second leading cause of brain metastases in women; patients with breast cancer brain metastasis (BCBM) survive an average of 6–18 months following diagnosis. Cancer stem cells are thought to be one of the driving forces behind distant metastasis, treatment resistance, and late-stage recurrence. The hedgehog-smoothened pathway has been identified as an important mediator of breast cancer stem cells (BCSC); however, FDA-approved therapies targeting smoothened have demonstrated limited clinical efficacy in breast cancer. Despite advances made in understanding BCSC, it is still challenging to effectively target BCSC underscoring the need to identify and inhibit novel mediators of BCSC for treating BCBM patients. Our laboratory recently reported that truncated glioma-associated oncogene homolog 1 (tGLI1) promotes preferential metastasis to the brain in breast cancer by activating BCSC and astrocytes in the tumor microenvironment (Oncogene 39:64–78, 2020). tGLI1 was discovered in our laboratory as an alternatively spliced GLI1 that functions as a tumor-specific gain-of-function transcription factor and terminal effector of the hedgehog pathway. We found that tGLI1 knockdown abrogated BCBM, providing the rationale to therapeutically target tGLI1. Cell-based chemical screens followed by validations demonstrated that ketoconazole, an FDA-approved azole antifungal, specifically inhibits tGLI1 leading to suppression of BCSC in vitro and BCBM in vivo. Based on these data, we opened a window-of-opportunity study in patients with BCBM to determine if ketoconazole penetrates the blood-brain barrier (BBB) and alters tGLI1 signaling in humans (NCT03796273). Preliminary sample analysis has confirmed tGLI1 expression in collected BCBM samples. To help identify more effective tGLI1 inhibitors, we screened 63 azole compounds for tGLI1-selectivity and identified four additional compounds as potential tGLI1 inhibitors. Animal studies were performed to compare the efficacy of these four compounds with ketoconazole in suppressing BCBM. Collectively, these data establish tGLI1 as an actionable target for BCBM.

Sonic Hedgehog (SHH) medulloblastoma originates from the cerebellar granule neuron progenitor (CGNP) population that depends on Hedgehog signaling for its expansion. While SHH tumors are characterized by an overall deregulation of this pathway, they also exhibit aberrations that are specific for patient age. To investigate if the developmental stage of the tumor cell-of-origin can account for these age-specific lesions, we compared transcriptomes from developing mouse CGNPs and observed highly dynamic gene expression changes as function of age. Cross-species comparison with a cohort of SHH medulloblastoma showed partial maintenance of these patterns in the different medulloblastoma patient-age groups. In particular, we found low primary cilia expression in early CGNPs and infant medulloblastoma, which coincided with insensitivity to Smoothened manipulation. Together, these findings can explain the absence of SMOOTHENED mutations in infant patients and suggest that drugs targeting the SHH pathway downstream of SMOOTHENED will be most appropriate for infant patients.

Atelerix albiventris (Wagner, 1841) is an erinaceid with variable common names but is most widely known as the four-toed hedgehog. One of 4 members of the genus Atelerix, A. albiventris is the smallest of the African hedgehogs. These nocturnal insectivores are sexually dimorphic and widespread, and are not a species of special conservation concern. Native to equatorial Africa, they inhabit steppes, savannas, grasslands, and agricultural fields. A. albiventris has been domesticated and is widely used in biomedical research and sold in the exotic pet trade.

SUMMARY The dentitions of representatives of the principal families of Insectivora are described and their functions and the types of lateral jaw movement present are deduced from a study of the wear patterns on the crowns of the teeth. The Tenrecoida are compared with the Talpidae and Soricidae, and it is concluded that whereas the latter families have teeth which are capable of both cutting and grinding actions, the Tenrecoidea are specialized for a pure cutting action. The Erinaceidae and Macroscelididae are specialized for a grinding action, with some variation in the latter family, while the Tupaiidae are again generalized. Consideration is given to the differing types of horizontal jaw movement encountered.

The morphological and physiological characters of strains of Trichophyton terrestre isolated from the cutaneous appendages of hedgehogs are described. The strains grow slowly, forming granular furrowed colonies and producing a wine-coloured pigment in the medium. They appear to form a homogeneous group showing several characters which distinguish them from soil isolates. Their failure to grow in sterile soil and certain other attributes suggest that these organisms are true inhabitants of the skin of hedgehogs rather than contaminants from the soil. No pathogenic effects in guinea-pigs hedgehog or human skin could be demonstrated.