Determining the chromatin accessibility profiles of functionally distinct SHH-medulloblastoma sub-populations
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ABSTRACT: Using FACS sorting on SOX2-eGFP and MKi67-RFP mice on a Ptch1+/- background, we identified cycling& non-cycling stem cells and tumor bulk subpopulations in endpoint mouse SHH-subgroup medulloblastoma tumors, and determined their chromatin accessibility progiles to identify unique regulators of cell state.
Project description:Zebrafish SHH MB tumors were generated by CRISPR-Cas9-mediated mutation of ptch1 in the context of tp53 heterozygous and tp53 mutant animals. Gene expression of the entire brain for ptch1 crispant animals and tp53 mutant control animals was analyzed by RNA-seq.
Project description:The identification of Lgr5 as an intestinal stem cell marker has made it possible to isolate and study primary stem cells from small intestine. Using the cell cycle specific expression og the mKi67 gene, we generated a novel Ki67-RFP knock-in allele which identifies dividing cells. Using Lgr5-GFP;Ki67-RFP mice, we isolated CBCs with distinct Wnt signaling levels and cell cycle features, and analyzed their global gene expression pattern using microarrays. We concluded that the cycling Lgr5hi stem cells exit the cell cycle in transition into the secretory lineage. Lgr5med Ki67low intermediate precursors reside in the zone of differentiation, resemble quiescent stem cells and generate the Dll1+ secretory precursors and the label retaining cells. Our findings support the cycling stem cell hypothesis and highlight the heterogeneity of early progenitors during lineage commitment. We used cell fractions of intestines from Lgr5-EGFP-ires-CreERT2 mice, expressing GFP under the control of the Lgr5 promoter, and Ki67-TagRFP mice where the RFP is fused to the C-terminus of the endogenous Ki67 gene. RNA was isolated from several FACS sorted cell populations of combinations expressing different levels of GFP and RFP: GFP high RFP high (Lgr5hi Ki67hi), GFP high RFP low (Lgr5hi Ki67low), GFP medium RFP high (Lgr5med Ki67high) and GFP medium RFP low (Lgr5med Ki67low). Purified RNA was processed, hybridized, and scanned according to the manufacturerM-bM-^@M-^Ys protocol and were hybridized on Affymetrix Mouse Gene ST 1.1 arrays).
Project description:The identification of Lgr5 as an intestinal stem cell marker has made it possible to isolate and study primary stem cells from small intestine. Using the cell cycle specific expression og the mKi67 gene, we generated a novel Ki67-RFP knock-in allele which identifies dividing cells. Using Lgr5-GFP;Ki67-RFP mice, we isolated CBCs with distinct Wnt signaling levels and cell cycle features, and analyzed their global gene expression pattern using microarrays. We concluded that the cycling Lgr5hi stem cells exit the cell cycle in transition into the secretory lineage. Lgr5med Ki67low intermediate precursors reside in the zone of differentiation, resemble quiescent stem cells and generate the Dll1+ secretory precursors and the label retaining cells. Our findings support the cycling stem cell hypothesis and highlight the heterogeneity of early progenitors during lineage commitment.
Project description:Germline loss-of-function (LOF) variants in Elongator complex protein 1 (ELP1) are the most prevalent predisposing genetic events in childhood medulloblastoma (MB), accounting for ~30% of the Sonic Hedgehog (SHH) 3 subtype. The underlying mechanism(s) by which germline ELP1 deficiency provokes SHH-MB pathogenesis remain unknown. Genetically engineered mice mimicking heterozygous germline Elp1 LOF (Elp1HET) seen in affected germline carriers exhibit hallmark features of cancer predisposition in cerebellar granule neuron progenitors (GNPs), including increased DNA replication stress, genomic instability, accelerated cell cycle, and stalled differentiation. Orthotopic transplantation of Elp1HET GNPs harboring somatic Ptch1 inactivation yielded SHH-MB-like tumors with compromised p53 signaling, providing an explanation for the exclusivity of ELP1-associated MBs in SHH-3 subtype. Preclinical treatment of ELP1-mutant patient-derived xenografts with an FDA-approved HDM2 inhibitor reactivated p53-dependent apoptosis and extended survival. Our findings functionally substantiate the role of ELP1 deficiency in SHH-MB predisposition and nominate therapeutics that overcome p53 inhibition as a rational treatment option.
Project description:Germline loss-of-function (LOF) variants in Elongator complex protein 1 (ELP1) are the most prevalent predisposing genetic events in childhood medulloblastoma (MB), accounting for ~30% of the Sonic Hedgehog (SHH) 3 subtype. The underlying mechanism(s) by which germline ELP1 deficiency provokes SHH-MB pathogenesis remain unknown. Genetically engineered mice mimicking heterozygous germline Elp1 LOF (Elp1HET) seen in affected germline carriers exhibit hallmark features of cancer predisposition in cerebellar granule neuron progenitors (GNPs), including increased DNA replication stress, genomic instability, accelerated cell cycle, and stalled differentiation. Orthotopic transplantation of Elp1HET GNPs harboring somatic Ptch1 inactivation yielded SHH-MB-like tumors with compromised p53 signaling, providing an explanation for the exclusivity of ELP1-associated MBs in SHH-3 subtype. Preclinical treatment of ELP1-mutant patient-derived xenografts with an FDA-approved HDM2 inhibitor reactivated p53-dependent apoptosis and extended survival. Our findings functionally substantiate the role of ELP1 deficiency in SHH-MB predisposition and nominate therapeutics that overcome p53 inhibition as a rational treatment option.
Project description:Aberrant activation of the Hedgehog (Hh) signaling pathway is implicated in the pathogenesis of many cancers, including medulloblastoma and basal cell carcinoma (BCC). In this study, using neonatally irradiated Ptch1+/- mice as a model of Hh-dependent tumors, we investigated the in vivo effects of MK-4101, a novel SMO antagonist, for treatment of medulloblastoma and BCC. Results clearly demonstrate a robust antitumor activity of MK-4101, achieved through the inhibition of proliferation and induction of extensive apoptosis in tumor cells. Of note, beside antitumor activity on transplanted tumors, MK-4101 was highly efficacious against primary medulloblastoma and BCC developing in the cerebellum and skin of Ptch1+/- mice. By identifying the changes induced by MK-4101 in gene expression profiles in tumors, we also elucidate the mechanism of action of this novel, orally administrable compound. MK-4101 targets the Hh pathway in the tumor cells, showing the maximum inhibitory effect on Gli1 activity. MK-4101 also induced deregulation of cell cycle and block of DNA replication in tumors. Members of the IGF and Wnt signaling pathways , were among the most highly deregulated genes by MK-4101, suggesting that the interplay among Hh, IGF and Wnt is crucial in Hh-dependent tumorigenesis. Altogether, the results of this preclinical study support a therapeutic opportunity for MK-4101 in the treatment of Hh-driven cancers, also providing useful information for combination therapy with drugs targeting pathways cooperating with Hh oncogenic activity. Gene expression data was generated (in replicates) from Medulloblastoma allografts collected at various time points and following low (40mpk) or high (80 mpk) or vehicle single dose (QD) or mutiple dose (BID) treatment with a SHH pathway inhibitor.
Project description:SUFU alterations are commonly detected in human SHH subgroup of medulloblastoma. Here we profile the gene expression of P13 wildtype and Sufu KO cerebellum, as well as Ptch1 KO MB in biological triplicate.
Project description:Medulloblastoma (MB) is the most prevalent pediatric cerebral cancer, but is rare in adults. The vast majority of MB arises sporadically but some few cases occur in association with germline alterations in genes such as PTCH1, SUFU, APC, and TP53. Additional genes are responsible for MB predisposition including some that have probably not been described so far either due to the rarity of the cases and/or to the low penetrance. Here we report the case of a 27 years old woman affected by Pitt Hopkins syndrome due to a heterozygous germline pathogenic variant in TCF4 who has developed a Sonic Hedgehog (SHH)-driven MB. Somatic loss of function variants of TCF4 have been identified in SHH MB especially among adults and this case raises the question of a predisposition to late-onset SHH MB associated with TCF4 germline alteration.
Project description:Aberrant activation of the Hedgehog (Hh) signaling pathway is implicated in the pathogenesis of many cancers, including medulloblastoma and basal cell carcinoma (BCC). In this study, using neonatally irradiated Ptch1+/- mice as a model of Hh-dependent tumors, we investigated the in vivo effects of MK-4101, a novel SMO antagonist, for treatment of medulloblastoma and BCC. Results clearly demonstrate a robust antitumor activity of MK-4101, achieved through the inhibition of proliferation and induction of extensive apoptosis in tumor cells. Of note, beside antitumor activity on transplanted tumors, MK-4101 was highly efficacious against primary medulloblastoma and BCC developing in the cerebellum and skin of Ptch1+/- mice. By identifying the changes induced by MK-4101 in gene expression profiles in tumors, we also elucidate the mechanism of action of this novel, orally administrable compound. MK-4101 targets the Hh pathway in the tumor cells, showing the maximum inhibitory effect on Gli1 activity. MK-4101 also induced deregulation of cell cycle and block of DNA replication in tumors. Members of the IGF and Wnt signaling pathways , were among the most highly deregulated genes by MK-4101, suggesting that the interplay among Hh, IGF and Wnt is crucial in Hh-dependent tumorigenesis. Altogether, the results of this preclinical study support a therapeutic opportunity for MK-4101 in the treatment of Hh-driven cancers, also providing useful information for combination therapy with drugs targeting pathways cooperating with Hh oncogenic activity.