title: Nicotine induces self-renewal of pancreatic cancer stem cells via neurotransmitter-driven activation of sonic hedgehog signalling.
abstract: A small subpopulation of pancreatic cancer cells with characteristics of stem cells drive tumour initiation, progression and metastasis. A better understanding of the regulation of cancer stem cells may lead to more effective cancer prevention and therapy. We have shown that the proliferation and migration of pancreatic cancer cell lines is activated by the nicotinic receptor-mediated release of stress neurotransmitters, responses reversed by γ-aminobutyric acid (GABA). However, the observed cancer inhibiting effects of GABA will only succeed clinically if GABA inhibits pancreatic cancer stem cells (PCSCs) in addition to the more differentiated cancer cells that comprise the majority of cancer tissues and cell lines. Using PCSCs isolated from two pancreatic cancer patients by cell sorting and by spheroid formation assay from pancreatic cancer cell line Panc-1, we tested the hypothesis that nicotine induces the self-renewal of PCSCs. Nicotinic acetylcholine receptors (nAChRs) α3, α4, α5 and α7 were expressed and chronic exposure to nicotine increased the protein expression of these receptors. Immunoassays showed that PCSCs produced the stress neurotransmitters epinephrine and norepinephrine and the inhibitory neurotransmitter GABA. Chronic nicotine significantly increased the production of stress neurotransmitters and sonic hedgehog (SHH) while inducing Gli1 protein and decreasing GABA. GABA treatment inhibited the induction of SHH and Gli1. Spheroid formation and 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliumbromide assays showed significant nicotine-induced increases in self renewal and cell proliferation, responses blocked by GABA. Our data suggest that nicotine increases the SHH-mediated malignant potential of PCSCs and that GABA prevents these effects.
authors.affiliation: Experimental Oncology Laboratory, Department of Biomedical & Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA.
authors.forename: Mohammed H
authors.initials: MH
authors.lastname: Al-Wadei
authors.affiliation: Experimental Oncology Laboratory, Department of Biomedical & Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA.
authors.forename: Jheelam
authors.initials: J
authors.lastname: Banerjee
authors.affiliation: Experimental Oncology Laboratory, Department of Biomedical & Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA.
authors.forename: Hussein A N
authors.initials: HA
authors.lastname: Al-Wadei
authors.affiliation: Experimental Oncology Laboratory, Department of Biomedical & Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN, USA. Electronic address: hmsch@utk.edu.
authors.forename: Hildegard M
authors.initials: HM
authors.lastname: Schuller
mesh_terms: D021441:Carcinoma, Pancreatic Ductal / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D000066673:Cell Self Renewal / Q000187:drug effects*; D002469:Cell Separation / Q000379:methods; D004305:Dose-Response Relationship, Drug; D053823:Hedgehog Proteins / Q000378:metabolism*; D006801:Humans; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D011978:Receptors, Nicotinic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D018874:Spheroids, Cellular; D014157:Transcription Factors / Q000378:metabolism; D000071676:Zinc Finger Protein GLI1; D005680:gamma-Aminobutyric Acid / Q000378:metabolism* / Q000494:pharmacology
chemical_list: C400551:GLI1 protein, human; D053823:Hedgehog Proteins; D018722:Nicotinic Agonists; D011978:Receptors, Nicotinic; C509239:SHH protein, human; D014157:Transcription Factors; D000071676:Zinc Finger Protein GLI1; D005680:gamma-Aminobutyric Acid; D009538:Nicotine
keywords: Cancer stem cells; GABA; Nicotinic receptors; Pancreatic cancer; Sonic hedgehog; Stress neurotransmitters