Copper-Mediated Mitochondrial Fission/Fusion Is Associated with Intrinsic Apoptosis and Autophagy in the Testis Tissues of Chicken

The aim of this study is to investigate whether copper (Cu) could induce testicular poisoning and influence the mitochondrial dynamics, apoptosis, and autophagy in chickens. For this purpose, thirty-six 1-day-old male Hy-line chickens were divided into control group (C group) and test group (Cu group). The chickens were exposed to 0 (C group) or 300 mg/kg (Cu group) of copper sulfate (CuSO₄) for 30, 60, and 90 days. CuSO₄ was added into the basal diet to make supplements. Testis tissues were subjected to observation of ultrastructure and detection of testis-related indexes. The results indicated that in the test group, the levels of the pro-apoptotic genes were up-regulated and the levels of the anti-apoptotic genes were down-regulated; the levels of mitochondrial fission-related genes markedly increased, and the levels of mitochondrial fusion-related genes were highly decreased; autophagy-related gene (autophagy-associated gene 4B (ATG4B), dynein, microtubule-associated protein 1 light chain 3 beta (LC3-II), ATG5, and beclin-1) levels were increased, while mammalian target of rapamycin (mTOR) and LC3-I levels were declined. The results of transmission electron microscopy (TEM) demonstrated that Cu induced mitochondrial fragmentation, which induced autophagy and apoptosis in chicken testes. In conclusion, CuSO₄ exposure can influence the mitochondrial dynamics balance and lead to mitochondria-initiated intrinsic pathway of apoptosis and autophagy, which triggers the testicular poisoning in chickens. What is more, there is a correlation among mitochondrial dynamics, apoptosis, and autophagy.

In situ 10-cell RNA sequencing in tissue and tumor biopsy samples

Single-cell transcriptomic methods classify new and existing cell types very effectively, but alternative approaches are needed to quantify the individual regulatory states of cells in their native tissue context. We combined the tissue preservation and single-cell resolution of laser capture with an improved preamplification procedure enabling RNA sequencing of 10 microdissected cells. This in situ 10-cell RNA sequencing (10cRNA-seq) can exploit fluorescent reporters of cell type in genetically engineered mice and is compatible with freshly cryoembedded clinical biopsies from patients. Through recombinant RNA spike-ins, we estimate dropout-free technical reliability as low as ~250 copies and a 50% detection sensitivity of ~45 copies per 10-cell reaction. By using small pools of microdissected cells, 10cRNA-seq improves technical per-cell reliability and sensitivity beyond existing approaches for single-cell RNA sequencing (scRNA-seq). Detection of low-abundance transcripts by 10cRNA-seq is comparable to random 10-cell groups of scRNA-seq data, suggesting no loss of gene recovery when cells are isolated in situ. Combined with existing approaches to deconvolve small pools of cells, 10cRNA-seq offers a reliable, unbiased, and sensitive way to measure cell-state heterogeneity in tissues and tumors.

Arsenic trioxide and/or copper sulfate induced apoptosis and autophagy associated with oxidative stress and perturbation of mitochondrial dynamics in the thymus of Gallus gallus

Arsenic (As) and copper (Cu) are ubiquitous environmental contaminants that are hazardous to the immune system. Our objective was to investigate the toxicity and potential mechanisms of thymus exposure to As and/or Cu. A chicken model was established by adding arsenic trioxide (As₂O₃; 30 mg/kg), copper sulfate (CuSO₄; 300 mg/kg), and simultaneously both elements in the basal diet. After the chickens were fed for 12 weeks, a significant reduction in antioxidant enzyme levels or production of malondialdehyde (MDA) emphasized the occurrence of oxidative stress. Furthermore, an imbalance in mitochondrial dynamics along with its abnormal structure certified mitochondrial dysfunction. Additionally, elevated levels of pro-apoptotic and autophagy genes and decreased levels of antiapoptotic genes were found in treated groups. Karyopyknosis and chromatin peripheral condensation were accompanied by an increased apoptosis ratio, as well as accumulation of autophagosomes, thus indicating that apoptosis and autophagy are involved in immune cell death. All of the above thymus lesions and index abnormalities occurred in a time-dependent manner, and the Cu and As co-administered groups showed more deteriorating effects than the Cu and As groups alone. Moreover, in the As or Cu group, the thymus tissue suffered different susceptibilities in oxidative toxicity, which needs further study. Collectively, our results manifested that co-exposure to As and Cu increased the oxidative burden and exacerbated mitochondrial dysfunction on the thymus. Additionally, apoptosis and autophagy may act as partners in inducing cell death in a cooperative manner in chicken thymus after As and/or Cu exposure.

[Influence of apatinib and VEGFR2-906T>C polymorphism on clinical outcomes of advanced non-small cell lung cancer patients]

Objective: To investigate the clinical outcomes of advanced non-small cell lung cancer (NSCLC) treated by apatinib regimens and the influence of VEGFR2-906T>C polymorphism. Methods: A total of 109 patients with advanced NSCLC who were treated by apatinib after three and more lines from March 2015 to December 2017 in the Department of Oncology of the First Affiliated Hospital of Zhengzhou University were included in this study. Overall response rates were evaluated after 2 cycles, then progression free survival (PFS) and overall survival (OS) were investigated, and safety data were recorded. Additionally, peripheral blood and the biopsy tissue specimens of some NSCLC patients were collected for the genotyping of genetic variation and VEGFR2 gene mRNA expression, respectively. The association between genotype and other characteristics and VEGFR2 gene mRNA expression were analyzed. The univariate analysis of genotypes and prognosis was carried out by Kaplan-Meier survival analysis, and multivariate analysis were adjusted by Cox regression analysis. Results: The treatment effect could be evaluated in all the 109 patients, among them, complete remission (CR) 0 case, partial remission (PR) 19 case, stable disease (SD) 58 case, progression disease (PD) 32 case. Overall response rate (ORR) was 17.43%, disease control rate (DCR) was 70.64%, median PFS was 4.35 months, median OS was 8.35 months. Of the polymorphisms analyzed, only -906T>C was of clinical significance. The prevalence of -906T>C in VEGFR2 among the study population were as follows: TT genotype 64 cases (58.72%), TC genotype 37 cases (33.94%), CC genotype 8 cases (7.34%), minor allele frequency of -906T>C was 0.24. The distribution of three genotypes was in accordance with Hardy-Weinberg Equilibrium (P=0.418). CC and TC genotype patients were merged in the comparison of clinical outcomes. The analysis of patients with different genotypes found that the ORR of CC/TC genotypes and TT genotypes were 13.33% and 20.31% (P=0.377), respectively. And the median PFS of patients with CC/TC genotype and TT genotype were 3.25 and 5.35 months, respectively, which was statistically significant (P=0.007). In terms of OS, the median OS of the two genotypes were 7.35 and 9.15 (P=0.014), respectively. Adjusted in multivariate Cox regression analysis of PFS, TC/CC genotypes were an independent factor for PFS (OR=1.83, P=0.015). The correlation between -906T>C and adverse reactions was not found in the safety analysis. Additionally, of the 69 biopsy tissue specimens, gene expression analysis was conducted. And the results show that the mRNA expression of VEGFR2 in cancer tissues of the patients with CC/TC genotypes were significantly higher than those of the TT genotype patients (P<0.001). Conclusions: Apatinib is safe and effective for patients with advanced non-small cell in multiline therapy. VEGFR2 -906T>C CC/TC genotype has a worse effect on apatinib multiline treatment in patients with advanced NSCLC.

GIDB: a knowledge database for the automated curation and multidimensional analysis of molecular signatures in gastrointestinal cancer

Gastrointestinal (GI) cancer is common, characterized by high mortality, and includes oesophagus, gastric, liver, bile duct, pancreas, rectal and colon cancers. The insufficient specificity and sensitivity of biomarkers is still a key clinical hindrance for GI cancer diagnosis and successful treatment. The emergence of `precision medicine', `basket trial' and `field cancerization' concepts calls for an urgent need and importance for the understanding of how organ system cancers occur at the molecular levels. Knowledge from both the literature and data available in public databases is informative in elucidating the molecular alterations underlying GI cancer. Currently, most available cancer databases have not offered a comprehensive discovery of gene-disease associations, molecular alterations and clinical information by integrated text mining and data mining in GI cancer. We develop GIDB, a panoptic knowledge database that attempts to automate the curation of molecular signatures using natural language processing approaches and multidimensional analyses. GIDB covers information on 8730 genes with both literature and data supporting evidence, 248 miRNAs, 58 lncRNAs, 320 copy number variations, 49 fusion genes and 2381 semantic networks. It presents a comprehensive database, not only in parallelizing supporting evidence and data integration for signatures associated with GI cancer but also in providing the timeline feature of major molecular discoveries. It highlights the most comprehensive overview, research hotspots and the development of historical knowledge of genes in GI cancer. Furthermore, GIDB characterizes genomic abnormalities in multilevel analysis, including simple somatic mutations, gene expression, DNA methylation and prognosis. GIDB offers a user-friendly interface and two customizable online tools (Heatmap and Network) for experimental researchers and clinicians to explore data and help them shorten the learning curve and broaden the scope of knowledge. More importantly, GIDB is an ongoing research project that will continue to be updated and improve the automated method for reducing manual work.

p53 and NF 1 loss plays distinct but complementary roles in glioma initiation and progression

Malignant glioma is one of the deadliest types of cancer. Understanding how the cell of origin progressively evolves toward malignancy in greater detail could provide mechanistic insights and lead to novel concepts for tumor prevention and therapy. Previously we have identified oligodendrocyte precursor cell (OPC) as the cell of origin for glioma following the concurrent deletion of p53 and NF1 using a mouse genetic mosaic system that can reveal mutant cells prior to malignancy. In the current study, we set out to deconstruct the gliomagenic process in two aspects. First, we determined how the individual loss of p53 or NF1 contributes to aberrant behaviors of OPCs. Second, we determined how signaling aberrations in OPCs progressively change from pre-malignant to transformed stages. We found that while the deletion of NF1 leads to mutant OPC expansion through increased proliferation and decreased differentiation, the deletion of p53 impairs OPC senescence. Signaling analysis showed that, while PI3K and MEK pathways go through stepwise over-activation, mTOR signaling remains at the basal level in pre-transforming mutant OPCs but is abruptly up-regulated in tumor OPCs. Finally, inhibiting mTOR via pharmacological or genetic methods, led to a significant blockade of gliomagenesis but had little impact on pre-transforming mutant OPCs, suggesting that mTOR is necessary for final transformation but not early progression. In summary, our findings show that deconstructing the tumorigenic process reveals specific aberrations caused by individual gene mutations and altered signaling events at precise timing during tumor progression, which may shed light on tumor-prevention strategies.

Enhanced 1,3-propanediol production in Klebsiella pneumoniae by a combined strategy of strengthening the TCA cycle and weakening the glucose effect

AIMS

This study aimed to strengthen the reducing equivalent generation in Klebsiella pneumoniae for improving 1,3-propanediol (PDO) production.

METHODS AND RESULTS

Disruption of the arcA gene activated the transcription levels of the TCA cycle genes and thus increased the NADH/NAD⁺ ratio by 54·2%, leading to the improved PDO titre and yield per cell from 16·1 g l^-1 and 4·0 g gDCW^-1 to 18·8 g l^-1 and 6·4 g gDCW^-1 respectively. Further ldhA gene deletion eliminated lactate accumulation and promoted the PDO titre to 19·9 g l^-1 . Finally, the glucose effect was weakened by deleting the crr gene to enhance the co-utilization of glucose and glycerol, resulting in the increased PDO production to 23·8 g l^-1 with the glycerol conversion rate of 59·5%. The PDO titre in bioreactor was promoted from 61·2 to 78·1 g l^-1 .

CONCLUSIONS

Deletions of the arcA and the crr genes showed positive effects on the TCA cycle activity and the co-utilization of glucose and glycerol, leading to the strengthened reducing equivalent generation and the improved PDO titre by 47·8% in shaker. The PDO titre in the bioreactor was enhanced to 78·1 g l^-1 .

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provided novel information on generating reducing equivalent for the PDO biosynthesis by strengthening the TCA cycle and weakening the glucose effect in K. pneumoniae.

Lineage-dependent spatial and functional organization of the mammalian enteric nervous system

The enteric nervous system (ENS) is essential for digestive function and gut homeostasis. Here we show that the amorphous neuroglia networks of the mouse ENS are composed of overlapping clonal units founded by postmigratory neural crest-derived progenitors. The spatial configuration of ENS clones depends on proliferation-driven local interactions of ENS progenitors with lineally unrelated neuroectodermal cells, the ordered colonization of the serosa-mucosa axis by clonal descendants, and gut expansion. Single-cell transcriptomics and mutagenesis analysis delineated dynamic molecular states of ENS progenitors and identified RET as a regulator of neurogenic commitment. Clonally related enteric neurons exhibit synchronous activity in response to network stimulation. Thus, lineage relationships underpin the organization of the peripheral nervous system.

Culture conditions defining glioblastoma cells behavior: what is the impact for novel discoveries?

In cancer research, the use of established cell lines has gradually been replaced by primary cell cultures due to their better representation of in vivo cancer cell behaviors. However, a major challenge with primary culture involves the finding of growth conditions that minimize alterations in the biological state of the cells. To ensure reproducibility and translational potentials for research findings, culture conditions need to be chosen so that the cell population in culture best mimics tumor cells in vivo. Glioblastoma (GBM) is one of the most aggressive and heterogeneous tumor types and the GBM research field would certainly benefit from culture conditions that could maintain the original plethora of phenotype of the cells. Here, we review culture media and supplementation options for GBM cultures, the rationale behind their use, and how much those choices affect drug-screening outcomes. We provide an overview of 120 papers that use primary GBM cultures and discuss the current predominant conditions. We also show important primary research data indicating that “mis-cultured” glioma cells can acquire unnatural drug sensitivity, which would have devastating effects for clinical translations. Finally, we propose the concurrent test of four culture conditions to minimize the loss of cell coverage in culture.

Genomewide differential expression profiling of long non-coding RNAs in androgenetic alopecia in a Chinese male population

BACKGROUND

Androgenetic alopecia (AGA), or male pattern baldness (MPB), is the most common form of hair loss in males. A combination of genetic and androgen causes have been suggested as factors that contribute to the development of AGA. However, the specific molecular mechanisms that underly AGA remain largely unknown. Long non-coding RNAs (lncRNAs), a new class of regulatory non-coding RNAs that are longer than 200 nucleotides, have been shown to play important roles in a number of cellular processes, including transcription, chromosome remodelling and post-transcriptional processing. The dysregulation of lncRNAs is associated with many forms of diseases, but it remains unknown whether lncRNAs are associated with AGA.

OBJECTIVE

The aim of this study was to identify AGA-associated lncRNAs and predict the potential roles of these lncRNAs in AGA.

METHODS

A genomewide microarray was used to identify lncRNAs that are differentially expressed between AGA and adjacent normal tissues. Real-time qRT-PCR was used to validate the microarray data.

RESULTS

A large number of lncRNAs were differentially expressed (fold change >2.4) between AGA and adjacent normal tissues. Of these, 770 were upregulated and 1373 were downregulated. Moreover, pathway analysis revealed that 53 functional pathways were associated with the upregulated transcripts, while 11 pathways were associated with the downregulated transcripts.

CONCLUSION

To our knowledge, this is the first study to investigate AGA-associated lncRNAs. lncRNA profiles are altered in AGA, and these lncRNAs and their target genes may serve as novel candidates for preventing and treating AGA.

Oncogenic effects of evolutionarily conserved noncoding RNA ECONEXIN on gliomagenesis

Accumulating studies have demonstrated the importance of long noncoding RNAs (lncRNAs) during oncogenic transformation. However, because most lncRNAs are currently uncharacterized, the identification of novel oncogenic lncRNAs is difficult. Given that intergenic lncRNA have substantially less sequence conservation patterns than protein-coding genes across species, evolutionary conserved intergenic lncRNAs are likely to be functional. The current study identified a novel intergenic lncRNA, LINC00461 (ECONEXIN) using a combined approach consisting of searching lncRNAs by evolutionary conservation and validating their expression in a glioma mouse model. ECONEXIN was the most highly conserved intergenic lncRNA containing 83.0% homology with the mouse ortholog (C130071C03Rik) for a region over 2500 bp in length within its exon 3. Expressions of ECONEXIN and C130071C03Rik were significantly upregulated in both human and mouse glioma tissues. Moreover, the expression of C130071C03Rik was upregulated even in precancerous conditions and markedly increased during glioma progression. Functional analysis of ECONEXIN in glioma cell lines, U87 and U251, showed it was dominantly located in the cytoplasm and interacted with miR-411-5p via two binding sites within ECONEXIN. Inhibition of ECONEXIN upregulated miR-411-5p together with the downregulation of its target, Topoisomerase 2 alpha (TOP2A), in glioma cell lines, resulting in decreased cell proliferation. Our data demonstrated that ECONEXIN is a potential oncogene that regulates TOP2A by sponging miR-411-5p in glioma. In addition, our investigative approaches to identify conserved lncRNA and their molecular characterization by validation in mouse tumor models may be useful to functionally annotate novel lncRNAs, especially cancer-associated lncRNAs.

A hybrid ontology-based information extraction system

Information Extraction is the process of automatically obtaining knowledge from plain text. Because of the ambiguity of written natural language, Information Extraction is a difficult task. Ontology-based Information Extraction (OBIE) reduces this complexity by including contextual information in the form of a domain ontology. The ontology provides guidance to the extraction process by providing concepts and relationships about the domain. However, OBIE systems have not been widely adopted because of the difficulties in deployment and maintenance. The Ontology-based Components for Information Extraction (OBCIE) architecture has been proposed as a form to encourage the adoption of OBIE by promoting reusability through modularity. In this paper, we propose two orthogonal extensions to OBCIE that allow the construction of hybrid OBIE systems with higher extraction accuracy and a new functionality. The first extension utilizes OBCIE modularity to integrate different types of implementation into one extraction system, producing a more accurate extraction. For each concept or relationship in the ontology, we can select the best implementation for extraction, or we can combine both implementations under an ensemble learning schema. The second extension is a novel ontology-based error detection mechanism. Following a heuristic approach, we can identify sentences that are logically inconsistent with the domain ontology. Because the implementation strategy for the extraction of a concept is independent of the functionality of the extraction, we can design a hybrid OBIE system with concepts utilizing different implementation strategies for extracting correct or incorrect sentences. Our evaluation shows that, in the implementation extension, our proposed method is more accurate in terms of correctness and completeness of the extraction. Moreover, our error detection method can identify incorrect statements with a high accuracy.

Culture conditions tailored to the cell of origin are critical for maintaining native properties and tumorigenicity of glioma cells

BACKGROUND

Cell culture plays a pivotal role in cancer research. However, culture-induced changes in biological properties of tumor cells profoundly affect research reproducibility and translational potential. Establishing culture conditions tailored to the cancer cell of origin could resolve this problem. For glioma research, it has been previously shown that replacing serum with defined growth factors for neural stem cells (NSCs) greatly improved the retention of gene expression profile and tumorigenicity. However, among all molecular subtypes of glioma, our laboratory and others have previously shown that the oligodendrocyte precursor cell (OPC) rather than the NSC serves as the cell of origin for the proneural subtype, raising questions regarding the suitability of NSC-tailored media for culturing proneural glioma cells.

METHODS

OPC-originated mouse glioma cells were cultured in conditions for normal OPCs or NSCs, respectively, for multiple passages. Gene expression profiles, morphologies, tumorigenicity, and drug responsiveness of cultured cells were examined in comparison with freshly isolated tumor cells.

RESULTS

OPC media-cultured glioma cells maintained tumorigenicity, gene expression profiles, and morphologies similar to freshly isolated tumor cells. In contrast, NSC-media cultured glioma cells gradually lost their OPC features and most tumor-initiating ability and acquired heightened sensitivity to temozolomide.

CONCLUSIONS

To improve experimental reproducibility and translational potential of glioma research, it is important to identify the cell of origin, and subsequently apply this knowledge to establish culture conditions that allow the retention of native properties of tumor cells.

Ret and Etv4 Promote Directed Movements of Progenitor Cells during Renal Branching Morphogenesis

Branching morphogenesis of the epithelial ureteric bud forms the renal collecting duct system and is critical for normal nephron number, while low nephron number is implicated in hypertension and renal disease. Ureteric bud growth and branching requires GDNF signaling from the surrounding mesenchyme to cells at the ureteric bud tips, via the Ret receptor tyrosine kinase and coreceptor Gfrα1; Ret signaling up-regulates transcription factors Etv4 and Etv5, which are also critical for branching. Despite extensive knowledge of the genetic control of these events, it is not understood, at the cellular level, how renal branching morphogenesis is achieved or how Ret signaling influences epithelial cell behaviors to promote this process. Analysis of chimeric embryos previously suggested a role for Ret signaling in promoting cell rearrangements in the nephric duct, but this method was unsuited to study individual cell behaviors during ureteric bud branching. Here, we use Mosaic Analysis with Double Markers (MADM), combined with organ culture and time-lapse imaging, to trace the movements and divisions of individual ureteric bud tip cells. We first examine wild-type clones and then Ret or Etv4 mutant/wild-type clones in which the mutant and wild-type sister cells are differentially and heritably marked by green and red fluorescent proteins. We find that, in normal kidneys, most individual tip cells behave as self-renewing progenitors, some of whose progeny remain at the tips while others populate the growing UB trunks. In Ret or Etv4 MADM clones, the wild-type cells generated at a UB tip are much more likely to remain at, or move to, the new tips during branching and elongation, while their Ret-/- or Etv4-/- sister cells tend to lag behind and contribute only to the trunks. By tracking successive mitoses in a cell lineage, we find that Ret signaling has little effect on proliferation, in contrast to its effects on cell movement. Our results show that Ret/Etv4 signaling promotes directed cell movements in the ureteric bud tips, and suggest a model in which these cell movements mediate branching morphogenesis.

Abstract B16: Deciphering individual roles of p53 and NF1 in the cell of origin for malignant glioma and the implications of targeted therapy

Glioma is currently an incurable disease. Identifying the cell of origin for glioma could provide critical insights for developing effective therapies. We previously used a mouse genetic system termed Mosaic Analysis using Double Markers (MADM) to introduce p53 and NF1 mutations into neural stem cells to determine which cell type is responsible for gliomagenesis. The unequivocal GFP-labeling of sparse mutant cells generated by MADM enabled us to study the entire course of tumor development, from pre-transforming stages to full malignancy. Based on thorough histological, transcriptomic, and genetic analyses we identified oligodendrocyte precursor cells (OPCs) as the cell of origin in this glioma model.

Here, we sought to understand the distinct role of p53 and NF1 in the transformation of OPCs since understanding these roles can give us a more thorough insight into how future therapies may be designed. The MADM system generates sparse GFP+ null and RFP+ sibling WT OPCs in an otherwise colorless, heterozygous mouse, allowing us to assess the impact of TSG loss on the capacity of cells to proliferate, survive, and differentiate. The loss of NF1 alone significantly increased mutant OPC proliferation with a proportional decrease in differentiation. However, massively over-expanded NF1-null OPCs did not transform into malignant gliomas, implicating the critical role of p53 in tumor suppression. Surprisingly, the loss of p53 alone had no effect on mutant OPC number, proliferation, or differentiation, suggesting that p53 function as a braking system that won't manifest its activity in the absence of driver mutation, such as NF1 loss. Next, we set out to test whether restoring either TSG function in tumor OPC cell lines would have any therapeutic efficacy. The restoration of wild type p53 led to a significant increase in both cell-cycle arrest and cell death. Since p53 function is commonly altered from mutations in patients, rather than complete loss of the protein, we tested whether restoring mutant p53 function with PRIMA-1 would have the same biological response as WT p53. We found that the restoration of mutant p53 function resulted in similar levels of cell cycle arrest and cell death as WT p53. This finding suggests that rescuing p53 function using small molecules may be of high value for future therapies. It also suggests that the loss of p53 activity is not a permanent fixture of tumor cells but that p53 can still exert it's tumor suppressor activity after transformation. Next we tested the therapeutic effects of the restoration of the GAP domain of NF1, which should reduce Ras activity in tumor OPCs. We found that the expression of WT but not the “GAP-dead” NF1-GAP led to a decrease in proliferation and an increase in differentiation of glioma cells. To test pharmacological compounds, we explore the possibility of targeting downstream effectors of Ras signaling, specifically mTOR inhibition because phospho-Akt level is elevated in tumor OPCs compared to WT OPCs. When we inhibited mTOR activity in MADM tumor mice at an age that is critical for mutant OPC expansion prior to transformation, we found that it blocked the ability of mutant OPCs to over-expand, suggesting that mTOR inhibition could potentially prevent gliomagenesis.

In summary our data demonstrates that while NF1 loss increases OPC proliferation and decreases differentiation, p53 loss is critical for transformation and that restoring the function of either of these pathways has profound effects on tumor OPC biology that could be translated into future therapeutic strategies.

Citation Format: Phillippe P. Gonzalez, Hui Zong. Deciphering individual roles of p53 and NF1 in the cell of origin for malignant glioma and the implications of targeted therapy. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr B16.

Abstract B01: Molecular evolutionary process of malignant glioma

Malignant gliomas are devastating, incurable brain tumors, with a bleak prognosis that improved little over the past decades. Many studies have been published describing genomic and transcriptomic alterations in malignant, fully formed gliomas. However, little is known of what takes place before the malignant stage, even though transformation of a normal cell into cancer is a multi-step process and, by the malignant stage, tumor cells have become very different from their original, untransformed ancestry. To gain insight into the driving forces of glioma and develop effective treatments, one must understand the entire process of tumorigenesis, for which it will be necessary to directly characterize the cell of origin of glioma at multiple time points throughout gliomagenesis.

We recently identified adult oligodendrocyte precursor cells (OPCs) as a cell of origin for malignant gliomas using a genetic mouse model that induces mutations in p53 and NF1, two of the most frequently mutated genes in human glioblastoma [Galvao et al., 2014, PNAS]. To ensure the introduction of mutations into adult but not neonatal OPCs, we used NG2-CreER that can specifically induce loxP-mediated recombination upon the administration of tamoxifen. Time course analysis revealed several distinct stages of gliomagenesis, starting with a rapid but transient hyper-proliferation shortly after tamoxifen administration, followed by a long dormancy period and ending with malignant transformation.

To further investigate the molecular changes during the pre-transforming stages, using the same mouse model, we developed a procedure based on laser capture microdissection to collect OPCs from the adult brain at distinct stages during gliomagenesis. We then used RNA sequencing to gain mechanistic insight into the successive stages of gliomagenesis. Our results show that, compared to tumor OPCs, the gene expression profile of pre-transforming mutant OPCs remains similar to that of wild-type OPCs, indicating that most transcriptional changes occur at the final transformation step. Interestingly, careful analysis revealed expression changes in hundreds of genes shortly after p53/NF1 mutagenesis. Using bioinformatics tools such as Gene Ontology (GO) terms, Gene Set Enrichment Analysis (GSEA) and Signaling Pathway Impact Analysis (SPIA), we are currently identifying the signaling pathways most affected at each time point to gain a better understanding of the molecular evolution from mutant OPCs to malignant glioma, which could provide critical insights on how to halt or even revert that process.

Citation Format: Rui P. Galvao, Susan Bassham, Thomas C. Nelson, Jason Sydes, Lauren K. Rosenfeld, William A. Cresko, Hui Zong. Molecular evolutionary process of malignant glioma. [abstract]. In: Proceedings of the AACR Special Conference: Advances in Brain Cancer Research; May 27-30, 2015; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2015;75(23 Suppl):Abstract nr B01.

MEK2 is a prognostic marker and potential chemo-sensitizing target for glioma patients undergoing temozolomide treatment

Although temozolomide (TMZ) is the first-line chemotherapeutic agent for glioblastoma, it is often non-curative due to drug resistance. To overcome the resistance of glioblastoma cells to TMZ, it is imperative to identify prognostic markers for outcome prediction and to develop chemo-sensitizing agents. Here, the gene expression profiles of TMZ-resistant and TMZ-sensitive samples were compared by microarray analysis, and mitogen-activated protein kinase kinase 2 (MEK2) was upregulated specifically in resistant glioma cells but not in sensitive tumor cells or non-tumor tissues. Moreover, a comprehensive analysis of patient data revealed that the increased level of MEK2 expression correlated well with the advancement of glioma grade and worse prognosis in response to TMZ treatment. Furthermore, reducing the level of MEK2 in U251 glioma cell lines or xenografted glioma models through shRNA-mediated gene knockdown inhibited cell proliferation and enhanced the sensitivity of cells toward TMZ treatment. Further analysis of tumor samples from glioma patients by real-time PCR indicated that an increased MEK2 expression level was closely associated with the activation of many drug resistance genes. Finally, these resistance genes were downregulated after MEK2 was silenced in vitro, suggesting that the mechanism of MEK2-induced chemo-resistance could be mediated by the transcriptional activation of these resistance genes. Collectively, our data indicated that the expression level of MEK2 could serve as a prognostic marker for glioma chemotherapy and that MEK2 antagonists can be used as chemo-sensitizers to enhance the treatment efficacy of TMZ.

Generation and applications of MADM-based mouse genetic mosaic system

Genetic mosaics describe organisms that contain cells with distinct genotypes related to somatic transposition, mitotic recombination, or genomic aberrations. Most, if not all, human cancers are genetic mosaics because cancer cells bear mutations that are absent in normal cells within the same body. While naturally occurring mutant cells in genetic mosaic animals are difficult to track down, a genetically engineered mosaic mouse model termed MADM (Mosaic Analysis with Double Markers) enables one to perform phenotypic analysis of mutant cells at single-cell resolution in vivo. While cancer modeling is the most obvious application, MADM is also highly suitable for studying developmental biology, neuroscience, and regenerative biology problems to investigate clonal contributions. Here we describe the construction of the MADM model on a specific chromosome through ES cell-based targeting of MADM cassettes into a pair of homologous chromosomes. We also detail procedures to verify the labeling efficiency of the newly established MADM model. Finally, we explain the breeding schemes and analytical principles that enable using MADM for in vivo phenotypic analysis at single-cell resolution.

Cell of origin for malignant gliomas and its implication in therapeutic development

Malignant glioma remains incurable despite tremendous advancement in basic research and clinical practice. The identification of the cell(s) of origin should provide deep insights into leverage points for one to halt disease progression. Here we summarize recent studies that support the notion that neural stem cell (NSC), astrocyte, and oligodendrocyte precursor cell (OPC) can all serve as the cell of origin. We also lay out important considerations on technical rigor for further exploring this subject. Finally, we share perspectives on how one could apply the knowledge of cell of origin to develop effective treatment methods. Although it will be a difficult battle, victory should be within reach as along as we continue to assimilate new information and facilitate the collaboration among basic scientists, translational researchers, and clinicians.

Luminal mitosis drives epithelial cell dispersal within the branching ureteric bud

The ureteric bud is an epithelial tube that undergoes branching morphogenesis to form the renal collecting system. Although development of a normal kidney depends on proper ureteric bud morphogenesis, the cellular events underlying this process remain obscure. Here, we used time-lapse microscopy together with several genetic labeling methods to observe ureteric bud cell behaviors in developing mouse kidneys. We observed an unexpected cell behavior in the branching tips of the ureteric bud, which we term "mitosis-associated cell dispersal." Premitotic ureteric tip cells delaminate from the epithelium and divide within the lumen; although one daughter cell retains a basal process, allowing it to reinsert into the epithelium at the site of origin, the other daughter cell reinserts at a position one to three cell diameters away. Given the high rate of cell division in ureteric tips, this cellular behavior causes extensive epithelial cell rearrangements that may contribute to renal branching morphogenesis.

MADM-ML, a mouse genetic mosaic system with increased clonal efficiency

Mosaic Analysis with Double Markers (MADM) is a mouse genetic system that allows simultaneous gene knockout and fluorescent labeling of sparse, clonally-related cells within an otherwise normal mouse, thereby circumventing embryonic lethality problems and providing single-cell resolution for phenotypic analysis in vivo. The clonal efficiency of MADM is intrinsically low because it relies on Cre/loxP-mediated mitotic recombination between two homologous chromosomes rather than within the same chromosome, as in the case of conditional knockout (CKO). Although sparse labeling enhances in vivo resolution, the original MADM labels too few or even no cells when a low-expressing Cre transgene is used or a small population of cells is studied. Recently, we described the usage of a new system, MADM-ML, which contains three mutually exclusive, self-recognizing loxP variant sites as opposed to a single loxP site present in the original MADM system (referred to as MADM-SL in this paper). Here we carefully compared the recombination efficiency between MADM-SL and MADM-ML using the same Cre transgene, and found that the new system labels significantly more cells than the original system does. When we established mouse medulloblastoma models with both the original and the new MADM systems, we found that, while the MADM-SL model suffered from varied tumor progression and incomplete penetrance, the MADM-ML model had consistent tumor progression and full penetrance of tumor formation. Therefore MADM-ML, with its higher recombination efficiency, will broaden the applicability of MADM for studying many biological questions including normal development and disease modeling at cellular resolution in vivo.

Abstract PR09: Fine temporal and spatial dissection of medulloblastoma progression with MADM, a mouse genetic mosaic model

Malignant cancers evolve over time with multiple contributing oncogenic mutations, and contain both tumor and niche cells. To understand when mutations contribute to malignant progression and how tumor and niche cell interact, we use a novel mouse genetic system termed MADM (Mosaic Analysis with Double Markers). MADM enables the tracking of tumorigenic cells from early stages with single cell resolution in vivo. Starting with a mouse heterozygous for a tumor suppressor gene (TSG), MADM can generate sporadic TSG-null cells via Cre-loxP mediated inter-chromosomal mitotic recombination events. Further, MADM unequivocally labels mutant cells with GFP, enabling lineage tracing of mutant cells with clear distinction from neighboring normal cells. Following cell division generating a mutant GFP+ cell, the sibling wildtype (WT) cell (RFP+) can also be assessed as an in situ internal control. We have applied MADM to model the Sonic Hedgehog (SHH)-subtype of medulloblastoma, the most common pediatric brain tumor.

In the developing cerebellum, unipotent granule neuron progenitors (GNPs) proliferate at the cerebellar surface in response to active Sonic hedgehog (SHH) signaling. Somatic mutation of the SHH receptor, Patched (Ptc), can lead to hyperactivation of the pathway, GNP overproliferation, and eventual malignancy. In addition to Ptc mutation, it has been reported that patients with medulloblastoma have a much worse prognosis when the tumor suppressor TRP53 (p53) is mutated. However, the timing of p53 contribution to tumorigenesis is still unclear. Here we used MADM to inactivate p53 in sporadic GNP cells in a Ptc heterozygous mouse model. To pinpoint the timing of p53 contribution to tumor progression, we performed a time course analysis of green-to-red cell number ratio (G/R ratio or mutant/wildtype). Our preliminary data suggest that the loss of p53 does not contribute to tumor progression until mid-stages of tumor progression since G/R ratio remains 1 in early lesions induced by the Ptc mutation.

For spatial organization of tumor and niche cells, we took advantage of the lineage tracing ability of MADM since all tumor cells should be green while neighboring normal cells should be non-labeled. Because the loss of heterzygousity is induced in unipotent GNPs, we expect the GFP+ tumor cells to maintain this identity. Surprisingly we find GFP+ cells in tumors consist of two cell types, GNPs and astrocytes, suggesting the trans-differentiation of some mutant GNPs into astrocytes. To confirm the human relevance of our findings, we performed double FISH-IF analysis of human patient samples for PTCH and our preliminary data indicated that GFAP+ astrocytes within tumors carried similar genomic aberrations to tumor GNPs, implicating the lineage relationship between these two cell types. Finally, in vitro co-culture experiment provided initial evidence that tumor GNP-derived astrocytes provide support to tumor GNPs, hinting at intricate cellular interactions in medulloblastoma.

In summary, our findings indicated that MADM provides great temporal and spatial resolution for cancer research. Our preliminary data suggest that tumor progression is not a linear process and distinct tumor suppressor genes act at different stages, and that tumor-niche interactions could be more complex than previously thought.

Citation Format: Brit Ventura, Maojin Yao, Ying Jiang, Kelsey Wahl, Fausto Rodriguez, Charles G. Eberhart, Hui Zong. Fine temporal and spatial dissection of medulloblastoma progression with MADM, a mouse genetic mosaic model. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr PR09.