Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor, with a median survival of about one year1. This poor prognosis is due to therapeutic resistance and tumor recurrence following surgical removal. Precisely how recurrence occurs is unknown. Using a genetically-engineered mouse model of glioma, we identify a subset of endogenous tumor cells that are the source of new tumor cells after the drug, temozolomide (TMZ), is administered to transiently arrest tumor growth. A Nestin-ΔTK-IRES-GFP (Nes-ΔTK-GFP) transgene that labels quiescent subventricular zone adult neural stem cells also labels a subset of endogenous glioma tumor cells. Upon arrest of tumor cell proliferation with TMZ, pulse-chase experiments demonstrate a tumor re-growth cell hierarchy originating with the Nes-ΔTK-GFP transgene subpopulation. Ablation of the GFP+ cells with chronic ganciclovir administration significantly arrested tumor growth and combined TMZ-ganciclovir treatment impeded tumor development. These data indicate the existence of a relatively quiescent subset of endogenous glioma cells that are responsible for sustaining long-term tumor growth through the production of transient populations of highly proliferative cells.

CNS deletion of Pten in the mouse has revealed its roles in controlling cell size and number, thus providing compelling etiology for macrocephaly and Lhermitte-Duclos disease. PTEN mutations in individuals with autism spectrum disorders (ASD) have also been reported, although a causal link between PTEN and ASD remains unclear. In the present study, we deleted Pten in limited differentiated neuronal populations in the cerebral cortex and hippocampus of mice. Resulting mutant mice showed abnormal social interaction and exaggerated responses to sensory stimuli. We observed macrocephaly and neuronal hypertrophy, including hypertrophic and ectopic dendrites and axonal tracts with increased synapses. This abnormal morphology was associated with activation of the Akt/mTor/S6k pathway and inactivation of Gsk3beta. Thus, our data suggest that abnormal activation of the PI3K/AKT pathway in specific neuronal populations can underlie macrocephaly and behavioral abnormalities reminiscent of certain features of human ASD.

SUMMARY Malignant astrocytomas are infiltrative and incurable brain tumors. Despite profound therapeutic implications, the identity of the cell(s) of origin has not been rigorously determined. We previously reported mouse models based on conditional inactivation of human astrocytoma-relevant tumor suppressors p53, Nf1, and Pten, wherein through somatic loss of heterozygosity, mutant mice develop tumors with 100% penetrance. In the present study, we show that tumor suppressor inactivation in neural stem/progenitor cells is both necessary and sufficient to induce astrocytoma formation. We demonstrate in vivo that transformed cells and their progeny undergo infiltration and multi-lineage differentiation during tumorigenesis. Tumor suppressor heterozygous neural stem/progenitor cultures from pre-symptomatic mice show aberrant growth advantage and altered differentiation, thus identifying a pre-tumorigenic cell population. Significance Identification of the original cell that gives rise to a tumor and whether it is a limited cell type has crucial implications for understanding cancer development. This knowledge is also requisite for rigorous investigation of tumor initiation mechanisms. Using fully penetrant mouse models, we identify neural stem/progenitor cells as cancer-initiating cells and derive insight into the behavior of these tumors. We also report malignant astrocytoma mouse models wherein tumor suppressor inactivation at embryonic, early postnatal, or adult ages induces tumor formation, and demonstrates the capacity of tumor cells to differentiate within the tumor. Our studies on pre-symptomatic mutant progenitor cultures indicate that the disease could be disseminating and acquire growth advantage long before the onset of clinical manifestations.

Rationale: The COVID-19 cases increased very fast in January and February 2020. The mortality among critically ill patients, especially the elder ones, is relatively high. Considering many patients died of severe inflammation response, it is urgent to develop effective therapeutic strategies for these patients. The human umbilical cord mesenchymal stem cells (hUCMSCs) have shown good capabilities to modulate the immune response and repair the injured tissue. Therefore, investigating the potential of hUCMSCs to the treatment of COVID-19 critically ill patients is necessary. Patient concerns: A 65-year-old woman felt fatigued and had a fever with body temperature of 38.2 ° C, coughed up white foaming sputum. After 1 day, she had chest tightness with SPO 2 of 81%, and blood pressure of 160/91 mm Hg. Diagnose: According to the guideline for the diagnosis and treatment of 2019 novel coronavirus infected pneumonia (Trial 4th Edition), COVID-19 was diagnosed, based on the real-time RT-PCR test of SARS-CoV-2. Interventions: After regular treatment for 12 days, the inflammation symptom of the patient was still very severe and the potential side effects of corticosteroid were observed. Then, allogenic hUCMSCs were given 3 times (5 × 10 7 cells each time) with a 3-day interval, together with thymosin α1 and antibiotics daily injection. Outcomes: After these treatments, most of the laboratory indexes and CT images showed remission of the inflammation symptom. The patient was subsequently transferred out of ICU, and the throat swabs test reported negative 4 days later. Lessons: These results indicated the clinical outcome and good tolerance of allogenic hUCMSCs transfer.

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We previously reported that central nervous system (CNS) inactivation of Nf1 and p53 tumor suppressor genes in mice results in the development of low-grade to high-grade progressive astrocytomas. When the tumors achieve high grade, they are frequently accompanied by Akt activation, reminiscent of the frequent association of PTEN mutations in human high-grade glioma. In the present study, we introduced CNS heterozygosity of Pten into the Nf1/p53 astrocytoma model. Resulting mice had accelerated morbidity, shortened survival, and full penetrance of high-grade astrocytomas. Haploinsufficiency of Pten accelerated formation of grade 3 astrocytomas, whereas loss of Pten heterozygosity and Akt activation coincided with progression into grade 4 tumors. These data suggest that successive loss of each Pten allele may contribute to de novo formation of high-grade astrocytoma and progression into glioblastoma, respectively, thus providing insight into the etiology of primary glioblastoma. The presence of ectopically migrating neural stem/progenitor lineage cells in presymptomatic Pten-deficient mutant brains supports the notion that these tumors may arise from stem/progenitor cells. [Cancer Res 2008;68(9):3286-94]

The microRNA159 (miR159) family represses the conserved GAMYB-like genes that encode R2R3 MYB domain transcription factors that have been implicated in gibberellin (GA) signaling in anthers and germinating seeds. In Arabidopsis (Arabidopsis thaliana), the two major miR159 family members, miR159a and miR159b, are functionally specific for two GAMYB-like genes, MYB33 and MYB65. These transcription factors have been shown to be involved in anther development, but there are differing reports about their role in the promotion of flowering and little is known about their function in seed germination. To understand the function of this pathway, we identified the genes and processes controlled by these GAMYB-like genes. First, we demonstrate that miR159 completely represses MYB33 and MYB65 in vegetative tissues. We show that GA does not release this repression and that these transcription factors are not required for flowering or growth. By contrast, in the absence of miR159, the deregulation of MYB33 and MYB65 in vegetative tissues up-regulates genes that are highly expressed in the aleurone and GA induced during seed germination. Confirming that these genes are GAMYB-like regulated, their expression was reduced in myb33.myb65.myb101 seeds. Aleurone vacuolation, a GA-mediated programmed cell death process required for germination, was impaired in these seeds. Finally, the deregulation of MYB33 and MYB65 in vegetative tissues inhibits growth by reducing cell proliferation. Therefore, we conclude that miR159 acts as a molecular switch, only permitting the expression of GAMYB-like genes in anthers and seeds. In seeds, these transcription factors participate in GA-induced pathways required for aleurone development and death.

Malignant Peripheral Nerve Sheath Tumors (MPNSTs) are soft tissue sarcomas that arise in connective tissue surrounding peripheral nerves. They occur sporadically in a subset of patients with Neurofibromatosis type-1 (NF1). MPNSTs are highly aggressive, therapeutically resistant, and typically fatal. Using comparative transcriptome analysis, we identified CXCR4, a G protein-coupled receptor, as highly expressed in mouse models of NF1-deficient MPNSTs, but not in non-transformed precursor cells. The chemokine receptor CXCR4 and its ligand, CXCL12, promote MPNST growth by stimulating cyclin D1 expression and cell cycle progression through PI3-Kinase (PI3K) and β-catenin signaling. Suppression of CXCR4 activity, either by shRNA or pharmacological inhibition decreases MPNST cell growth in culture and inhibits tumorigenesis in allografts and in spontaneous genetic mouse models of MPNST. We further demonstrate conservation of these activated molecular pathways in human MPNSTs. Our findings indicate a role for CXCR4 in NF1-associated MPNST development, and identify a novel therapeutic target.