Abstract
Glioblastoma Multiforme (GBM), the most common and lethal adult primary tumor of the brain, showed a link between Sonic Hedgehog (SHH) pathway in the resistance to temozolomide (TMZ). PTCH1, the SHH receptor, can tonically represses signaling by endocytosis. We asked how the decrease in PTCH1 in GBM cells could lead to TMZ-resistance. TMZ resistant GBM cells have increased PTCH1 mRNA and reduced protein. Knockdown of Dicer, a Type III RNAase, indicated that miRNAs can explain the decreased PTCH1 in TMZ resistant cells. Computational studies, real-time PCR, reporter gene studies, western blots, target protector oligos and ectopic expression identified miR-9 as the target of PTCH1 in resistant GBM cells with concomitant activation of SHH signaling. MiR-9 mediated increases in the drug efflux transporters, MDR1 and ABCG2. MiR-9 was increased in the tissues from GBM patients and in an early passage GBM cell line from a patient with recurrent GBM but not from a naïve patient. Pharmacological inhibition of SHH signaling sensitized the GBM cells to TMZ. Taken together, miR-9 targets PTCH1 in GBM cells by a SHH-independent method in GBM cells for TMZ resistance. The identified pathways could lead to new strategies to target GBM with combinations of drugs.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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3' Untranslated Regions / genetics
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ATP Binding Cassette Transporter, Subfamily B / genetics
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ATP Binding Cassette Transporter, Subfamily B / metabolism
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ATP Binding Cassette Transporter, Subfamily G, Member 2
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ATP-Binding Cassette Transporters / genetics
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ATP-Binding Cassette Transporters / metabolism
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Animals
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Antineoplastic Agents, Alkylating / pharmacology
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Blotting, Western
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Brain Neoplasms / genetics
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Brain Neoplasms / metabolism
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Brain Neoplasms / pathology
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Cell Line, Tumor
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Dacarbazine / analogs & derivatives*
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Dacarbazine / pharmacology
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Drug Resistance, Neoplasm / genetics*
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Gene Expression Regulation, Neoplastic
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Glioblastoma / genetics
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Glioblastoma / metabolism
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Glioblastoma / pathology
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HEK293 Cells
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Hedgehog Proteins / genetics*
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Hedgehog Proteins / metabolism
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Humans
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MicroRNAs / genetics*
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Neoplasm Proteins / genetics
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Neoplasm Proteins / metabolism
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Patched Receptors
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Patched-1 Receptor
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RNA Interference
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Receptors, Cell Surface / genetics*
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Receptors, Cell Surface / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Signal Transduction / genetics
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Temozolomide
Substances
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3' Untranslated Regions
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ABCB1 protein, human
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ABCG2 protein, human
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ATP Binding Cassette Transporter, Subfamily B
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ATP Binding Cassette Transporter, Subfamily G, Member 2
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ATP-Binding Cassette Transporters
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Antineoplastic Agents, Alkylating
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Hedgehog Proteins
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MIRN92 microRNA, human
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MicroRNAs
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Neoplasm Proteins
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PTCH1 protein, human
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Patched Receptors
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Patched-1 Receptor
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Receptors, Cell Surface
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SHH protein, human
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Dacarbazine
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Temozolomide