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Multi-focal control of mitochondrial gene expression by oncogenic MYC provides potential therapeutic targets in cancer.

ABSTRACT: Despite ubiquitous activation in human cancer, essential downstream effector pathways of the MYC transcription factor have been difficult to define and target. Using a structure/function-based approach, we identified the mitochondrial RNA polymerase (POLRMT) locus as a critical downstream target of MYC. The multifunctional POLRMT enzyme controls mitochondrial gene expression, a process required both for mitochondrial function and mitochondrial biogenesis. We further demonstrate that inhibition of this newly defined MYC effector pathway causes robust and selective tumor cell apoptosis, via an acute, checkpoint-like mechanism linked to aberrant electron transport chain complex assembly and mitochondrial reactive oxygen species (ROS) production. Fortuitously, MYC-dependent tumor cell death can be induced by inhibiting the mitochondrial gene expression pathway using a variety of strategies, including treatment with FDA-approved antibiotics. In vivo studies using a mouse model of Burkitt's Lymphoma provide pre-clinical evidence that these antibiotics can successfully block progression of MYC-dependent tumors.

SUBMITTER: Oran AR

PROVIDER: S-EPMC5340124 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Multi-focal control of mitochondrial gene expression by oncogenic MYC provides potential therapeutic targets in cancer.

Oran Amanda R AR Adams Clare M CM Zhang Xiao-Yong XY Gennaro Victoria J VJ Pfeiffer Harla K HK Mellert Hestia S HS Seidel Hans E HE Mascioli Kirsten K Kaplan Jordan J Gaballa Mahmoud R MR Shen Chen C Rigoutsos Isidore I King Michael P MP Cotney Justin L JL Arnold Jamie J JJ Sharma Suresh D SD Martinez-Outschoorn Ubaldo E UE Vakoc Christopher R CR Chodosh Lewis A LA Thompson James E JE Bradner James E JE Cameron Craig E CE Shadel Gerald S GS Eischen Christine M CM McMahon Steven B SB

Oncotarget 20161101 45

Despite ubiquitous activation in human cancer, essential downstream effector pathways of the MYC transcription factor have been difficult to define and target. Using a structure/function-based approach, we identified the mitochondrial RNA polymerase (POLRMT) locus as a critical downstream target of MYC. The multifunctional POLRMT enzyme controls mitochondrial gene expression, a process required both for mitochondrial function and mitochondrial biogenesis. We further demonstrate that inhibition o ...[more]

PMID: 27590350

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Project description:Mammary tumorigenesis is associated with the increased expression of several proteins in the focal adhesion complex, including focal adhesion kinase (FAK) and various integrins. Aberrant expression of these molecules occurs concomitant with the conversion of TGF-beta function from a tumor suppressor to a tumor promoter. We previously showed that interaction between beta3 integrin and TbetaR-II facilitates TGF-beta-mediated oncogenic signaling, epithelial-mesenchymal transition (EMT), and metastasis. However, the molecular mechanisms by which the focal adhesion complex contributes to beta3 integrin:TbetaR-II signaling and the oncogenic conversion of TGF-beta remain poorly understood.FAK expression and activity were inhibited in normal and malignant mammary epithelial cells (MECs) either genetically by using lentiviral-mediated delivery of shRNAs against FAK, or pharmacologically through in vitro and in vivo use of the FAK inhibitors, PF-562271 and PF-573228. Altered Smad2/3 and p38 MAPK activation, migration, EMT, and invasion in response to TGF-beta1 were monitored in FAK-manipulated cells. TbetaR-II expression was increased in metastatic breast cancer cells by retroviral transduction, and the metastasis of FAK- and TbetaR-II-manipulated tumors was monitored by using bioluminescent imaging.TGF-beta stimulation of MECs stabilized and activated FAK in a beta3 integrin- and Src-dependent manner. Furthermore, by using the human MCF10A breast cancer progression model, we showed that increased FAK expression in metastatic breast cancer cells mirrored the acquisition of enhanced activation of p38 MAPK by TGF-beta. Administering FAK inhibitors or rendering metastatic breast cancer cells FAK deficient abrogated the interaction between beta3 integrin and TbetaR-II, thereby preventing TGF-beta from (a) activating p38 MAPK; (b) stimulating MEC invasion, migration, and EMT; and (c) inducing early primary tumor dissemination to the lungs. Finally, in contrast to FAK depletion, adjuvant FAK chemotherapy of mammary tumors decreased their growth in part by diminished macrophage tumor infiltration.Our studies identify an essential function for FAK in mediating the interaction between beta3 integrin and TbetaR-II, and thus in facilitating the oncogenic conversion of TGF-beta required for mammary tumor metastasis. Furthermore, this study establishes chemotherapeutic targeting of FAK as an effective, two-pronged approach in preventing tumor progression both by decreasing innate immune cell infiltration, and by inhibiting early TGF-beta-dependent metastasis.

Dataset Information

Multi-focal control of mitochondrial gene expression by oncogenic MYC provides potential therapeutic targets in cancer.

Publications

Multi-focal control of mitochondrial gene expression by oncogenic MYC provides potential therapeutic targets in cancer.

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