Brain tumors are the leading cause of cancer-related death in childhood. Diffuse intrinsic pontine glioma (DIPG) arises in the pons of the brainstem and is universally fatal, comprising nearly 15% of all pediatric brain tumors.1 Despite international endeavors to improve outcome, DIPGs show poor response to conventional radiation and chemotherapeutic strategies used in adults.2 Only within the last decade have studies really begun to describe differences between adult and pediatric diseases, underscoring the need for better targeted therapies. Most recently, our group made a major breakthrough in the understanding of DIPG biology by identifying three molecular subgroups: MYCN, Silent and H3K27M.3 The MYCN subgroup has no recurrent mutations but is characterized by chromothripsis on chromosome 2p leading to amplification of MYCN and ID2. The Silent subgroup is featured by a lower mutation rate and fewer copy number alterations than the other two subgroups. The H3K27M subgroup is the largest and harbors a K27M mutation in either H3F3A (H3.3) or the HIST1H3 family (H3.1). These findings highlight the potential importance of epigenetic dysregulation in DIPG pathogenesis. However, H3K27M tumors harbor additional alterations while MYCN and Silent subgroup tumors have relatively fewer recurrent genetic alterations, strongly suggesting that H3K27M alone is likely insufficient to drive malignant transformation. Additional mechanisms, including those beyond the traditional epigenetic and genetic modifications within the nuclear genome (nDNA), are likely to be required. Unlike normal cells that rely primarily on mitochondrial oxidative phosphorylation (OXPHOS) to generate the energy needed for cellular processes, cancer cells depend on aerobic glycolysis to support their uncontrolled growth even in the presence of ample oxygen, a phenomenon termed “the Warburg effect.”4 Abnormal OXPHOS and aerobic metabolism as a result of mitochondrial dysfunction are considered robust metabolic hallmarks of many cancer entities. Numerous somatic mutations in the mitochondrial genome (mtDNA) as well as mtDNA copy number changes have been increasingly observed across a broad spectrum of primary malignancies, including adult brain tumors.5 Mounting evidence has demonstrated that mtDNA sequence and content variations are associated with neoplastic transformation, tumor progression and metastasis, chemo/radioresistance, and disease prognosis.6 Due to decreased expression of mtDNA-encoded polypeptides and compromised function of respiratory enzyme complexes, either qualitative or quantitative alterations in mtDNA could elicit a decline in mitochondrial respiratory activity and cause persistent defects in the OXPHOS system accompanied by generation of excessive reactive oxygen species (ROS). This in turn further damages mtDNA, accelerates its mutational rate, and eventually establishes a vicious cycle amplifying mitochondrial dysfunction and oxidative stress. This scenario has been proposed to positively contribute to cancer initiation and/or progression.5,6 Despite a huge explosion of DIPG genomic and transcriptomic data and tremendous efforts in characterizing the biological significance of recurrent mutations in nDNA, to date, no study has investigated mtDNA mutations and copy number changes in DIPG or their potential as therapeutic targets. We hypothesize that mtDNA alterations and consequent impairment of mitochondrial and OXPHOS functions by themselves or in a cooperative fashion with nDNA mutations are important for the initiation and/or progression of DIPG. Work proposed in this study aims to screen pathogenic “driver” mutations in the entire mitochondrial genome of DIPG tumors by harnessing the advantage of targeted next-generation sequencing (NGS) technology and to elucidate the molecular mechanisms underlying their involvement in DIPG carcinogenesis (Aim 1). The potential to exploit altered mtDNA copy number as a novel therapeutic target in DIPG will be evaluated in Aim 2. This preclinical work will determine if manipulating mtDNA copy number or stimulating mitochondrial biogenesis is capable of rescuing the metabolic function of defective mitochondria in DIPG and thus reverse the malignant phenotype. Targeted whole mitochondrial genome sequencing may lead to the identification of a set of frequent mtDNA mutations that may play a primary and causative role in DIPG development. Our innovative approach of targeting aberrant mtDNA content in combination with conventional therapies will provide clues for designing novel therapeutic strategies. Our group is a leader in the field of DIPG and being part of the largest pediatric neuro-oncology team in Canada and active contributors in the DIPG collaborative, we are ideally situated to translate discoveries made through this project into novel early diagnostic tools and more effective therapeutic trials for this devastating disease.
Brain tumors are the leading cause of cancer-related death in childhood. Diffuse intrinsic pontine glioma (DIPG) arises in the pons of the brainstem and is universally fatal, comprising nearly 15% of all pediatric brain tumors.1 Despite international endeavors to improve outcome, DIPGs show poor response to conventional radiation and chemotherapeutic strategies used in adults.2 Only within the last decade have studies really begun to describe differences between adult and pediatric diseases, underscoring the need for better targeted therapies. Most recently, our group made a major breakthrough in the understanding of DIPG biology by identifying three molecular subgroups: MYCN, Silent and H3K27M.3 The MYCN subgroup has no recurrent mutations but is characterized by chromothripsis on chromosome 2p leading to amplification of MYCN and ID2. The Silent subgroup is featured by a lower mutation rate and fewer copy number alterations than the other two subgroups. The H3K27M subgroup is the largest and harbors a K27M mutation in either H3F3A (H3.3) or the HIST1H3 family (H3.1). These findings highlight the potential importance of epigenetic dysregulation in DIPG pathogenesis. However, H3K27M tumors harbor additional alterations while MYCN and Silent subgroup tumors have relatively fewer recurrent genetic alterations, strongly suggesting that H3K27M alone is likely insufficient to drive malignant transformation. Additional mechanisms, including those beyond the traditional epigenetic and genetic modifications within the nuclear genome (nDNA), are likely to be required. Unlike normal cells that rely primarily on mitochondrial oxidative phosphorylation (OXPHOS) to generate the energy needed for cellular processes, cancer cells depend on aerobic glycolysis to support their uncontrolled growth even in the presence of ample oxygen, a phenomenon termed “the Warburg effect.”4 Abnormal OXPHOS and aerobic metabolism as a result of mitochondrial dysfunction are considered robust metabolic hallmarks of many cancer entities. Numerous somatic mutations in the mitochondrial genome (mtDNA) as well as mtDNA copy number changes have been increasingly observed across a broad spectrum of primary malignancies, including adult brain tumors.5 Mounting evidence has demonstrated that mtDNA sequence and content variations are associated with neoplastic transformation, tumor progression and metastasis, chemo/radioresistance, and disease prognosis.6 Due to decreased expression of mtDNA-encoded polypeptides and compromised function of respiratory enzyme complexes, either qualitative or quantitative alterations in mtDNA could elicit a decline in mitochondrial respiratory activity and cause persistent defects in the OXPHOS system accompanied by generation of excessive reactive oxygen species (ROS). This in turn further damages mtDNA, accelerates its mutational rate, and eventually establishes a vicious cycle amplifying mitochondrial dysfunction and oxidative stress. This scenario has been proposed to positively contribute to cancer initiation and/or progression.5,6 Despite a huge explosion of DIPG genomic and transcriptomic data and tremendous efforts in characterizing the biological significance of recurrent mutations in nDNA, to date, no study has investigated mtDNA mutations and copy number changes in DIPG or their potential as therapeutic targets. We hypothesize that mtDNA alterations and consequent impairment of mitochondrial and OXPHOS functions by themselves or in a cooperative fashion with nDNA mutations are important for the initiation and/or progression of DIPG. Work proposed in this study aims to screen pathogenic “driver” mutations in the entire mitochondrial genome of DIPG tumors by harnessing the advantage of targeted next-generation sequencing (NGS) technology and to elucidate the molecular mechanisms underlying their involvement in DIPG carcinogenesis (Aim 1). The potential to exploit altered mtDNA copy number as a novel therapeutic target in DIPG will be evaluated in Aim 2. This preclinical work will determine if manipulating mtDNA copy number or stimulating mitochondrial biogenesis is capable of rescuing the metabolic function of defective mitochondria in DIPG and thus reverse the malignant phenotype. Targeted whole mitochondrial genome sequencing may lead to the identification of a set of frequent mtDNA mutations that may play a primary and causative role in DIPG development. Our innovative approach of targeting aberrant mtDNA content in combination with conventional therapies will provide clues for designing novel therapeutic strategies. Our group is a leader in the field of DIPG and being part of the largest pediatric neuro-oncology team in Canada and active contributors in the DIPG collaborative, we are ideally situated to translate discoveries made through this project into novel early diagnostic tools and more effective therapeutic trials for this devastating disease.
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Curabitur ut ipsum non odio malesuada vulputate. Morbi maximus, est eu lobortis molestie, tortor sapien hendrerit nisi, in cursus odio diam ut odio. Fusce pulvinar volutpat velit. Aliquam erat volutpat. Integer rhoncus mollis suscipit. Praesent non ipsum mollis, finibus nunc a, scelerisque nibh. In feugiat iaculis velit, eu semper lacus dignissim nec. Praesent vitae nisi leo. Cras venenatis dictum magna ut semper. Sed eget eros nibh. Sed vitae quam sed dolor faucibus elementum. Curabitur interdum porttitor finibus. Nullam tincidunt odio lectus, sit amet rhoncus libero dapibus sed. Sed mollis egestas enim, vel porta tortor volutpat eget.
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Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Donec faucibus, turpis sit amet maximus dapibus, sapien nisl bibendum turpis, pharetra commodo tellus libero vel nulla. Sed nec velit viverra, congue sapien et, gravida libero. Proin eget ante eget turpis egestas accumsan. Aliquam arcu nibh, aliquam rhoncus vulputate in, pellentesque at sem. Maecenas cursus tempus nibh id tempus. Mauris dolor sapien, lacinia sit amet condimentum at, dapibus eget lectus. Phasellus vel pellentesque ex. Nunc aliquam in ligula at tristique. In mollis suscipit felis eu finibus. Nullam non dignissim nibh, nec suscipit ex. Suspendisse tincidunt et mauris id finibus. Aliquam vehicula a sem quis venenatis.
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Sed at tortor et tortor tincidunt feugiat id in dui. Vivamus eget justo nisl. Aenean congue laoreet nisl a elementum. Nunc consectetur velit non ligula sollicitudin, quis eleifend urna sollicitudin. Sed tincidunt, nisl quis varius venenatis, dui massa condimentum tellus, sed sollicitudin diam magna mollis augue. Sed venenatis commodo purus id malesuada. Aenean volutpat elit vel gravida consectetur. Vestibulum diam quam, lacinia ac tortor eget, tincidunt dapibus dui. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Proin nisl leo, pretium sed arcu imperdiet, hendrerit sollicitudin sem. Duis non magna at nunc sagittis ullamcorper a id est. Maecenas cursus nisl in faucibus hendrerit.
Sed hendrerit vitae purus et tempor. Aenean vitae varius velit. Nullam aliquet ipsum elit. Mauris vestibulum purus et metus imperdiet, quis gravida eros pretium. Curabitur rutrum nunc vitae tincidunt condimentum. Aenean sit amet augue velit. Nunc tristique quis lorem id pharetra. Pellentesque sollicitudin, eros sed egestas rutrum, nulla nisl sodales elit, ut imperdiet nunc lectus sit amet nulla. Ut malesuada finibus libero. Curabitur mi dolor, sollicitudin quis bibendum quis, dictum sed enim.
Pellentesque nibh erat, egestas sit amet sagittis malesuada, rhoncus at neque. Mauris maximus commodo tortor, non egestas magna finibus vitae. Sed hendrerit nulla vel venenatis tempor. Suspendisse tristique tincidunt libero et placerat. Nam tincidunt condimentum lorem, vel pharetra est iaculis sed. Nullam ac tincidunt orci. Quisque pharetra ut sem sit amet aliquam. Phasellus risus libero, varius in condimentum vel, commodo id ipsum. Aliquam in metus cursus, mattis diam ut, aliquam magna. Suspendisse facilisis dui et orci varius, suscipit facilisis augue dapibus. In eget nibh ipsum. Suspendisse eget pharetra est, quis condimentum felis. Fusce scelerisque congue libero, sed aliquam mi elementum a. Etiam scelerisque ante non auctor porta. Nam eu nunc id ex finibus dictum. Praesent dui ex, dictum ac massa eget, rutrum gravida nisi.
Sed egestas arcu in dui euismod, eget faucibus massa iaculis. Etiam efficitur lectus et purus lobortis, ac blandit eros rutrum. Proin bibendum consectetur leo vel gravida. Etiam et ultricies sapien. Nam lacinia tellus erat, id facilisis est consequat et. Morbi quis risus in neque iaculis pharetra ut consectetur libero. Aenean feugiat tempor mi eu posuere.
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer gravida non felis non euismod. Fusce finibus aliquet consequat. Nam ac metus bibendum, iaculis purus sed, suscipit ligula. Proin et nisi libero. Mauris non urna urna. Nullam augue eros, fringilla sed mauris vitae, porta tincidunt risus. Aliquam sed tincidunt sem. Quisque lacinia quam tortor, imperdiet efficitur odio iaculis in. Sed ultricies condimentum volutpat. Vivamus dignissim faucibus porta.
Curabitur ut ipsum non odio malesuada vulputate. Morbi maximus, est eu lobortis molestie, tortor sapien hendrerit nisi, in cursus odio diam ut odio. Fusce pulvinar volutpat velit. Aliquam erat volutpat. Integer rhoncus mollis suscipit. Praesent non ipsum mollis, finibus nunc a, scelerisque nibh. In feugiat iaculis velit, eu semper lacus dignissim nec. Praesent vitae nisi leo. Cras venenatis dictum magna ut semper. Sed eget eros nibh. Sed vitae quam sed dolor faucibus elementum. Curabitur interdum porttitor finibus. Nullam tincidunt odio lectus, sit amet rhoncus libero dapibus sed. Sed mollis egestas enim, vel porta tortor volutpat eget.
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Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer gravida non felis non euismod. Fusce finibus aliquet consequat. Nam ac metus bibendum, iaculis purus sed, suscipit ligula. Proin et nisi libero. Mauris non urna urna. Nullam augue eros, fringilla sed mauris vitae, porta tincidunt risus. Aliquam sed tincidunt sem. Quisque lacinia quam tortor, imperdiet efficitur odio iaculis in. Sed ultricies condimentum volutpat. Vivamus dignissim faucibus porta.
Curabitur ut ipsum non odio malesuada vulputate. Morbi maximus, est eu lobortis molestie, tortor sapien hendrerit nisi, in cursus odio diam ut odio. Fusce pulvinar volutpat velit. Aliquam erat volutpat. Integer rhoncus mollis suscipit. Praesent non ipsum mollis, finibus nunc a, scelerisque nibh. In feugiat iaculis velit, eu semper lacus dignissim nec. Praesent vitae nisi leo. Cras venenatis dictum magna ut semper. Sed eget eros nibh. Sed vitae quam sed dolor faucibus elementum. Curabitur interdum porttitor finibus. Nullam tincidunt odio lectus, sit amet rhoncus libero dapibus sed. Sed mollis egestas enim, vel porta tortor volutpat eget.