title: Novel anti-tumor mechanism of galanin receptor type 2 in head and neck squamous cell carcinoma cells.
abstract: Galanin and its receptors, GALR1 and GALR2, are known tumor suppressors and potential therapeutic targets in head and neck squamous cell carcinoma (HNSCC). Previously, we demonstrated that, in GALR1-expressing HNSCC cells, the addition of galanin suppressed tumor proliferation via upregulation of ERK1/2 and cyclin-dependent kinase inhibitors, whereas, in GALR2-expressing cells, the addition of galanin not only suppressed proliferation, but also induced apoptosis. In this study, we first transduced HEp-2 and KB cell lines using a recombinant adeno-associated virus (rAAV)-green fluorescent protein (GFP) vector and confirmed a high GFP expression rate (>90%) in both cell lines at the standard vector dose. Next, we demonstrated that GALR2 expression in the presence of galanin suppressed cell viability to 40-60% after 72 h in both cell lines. Additionally, the annexin V-positive rate and sub-G0/G1 phase population were significantly elevated in HEp-2 cells (mock vs GALR2: 12.3 vs 25.0% (P < 0.01) and 9.1 vs 32.0% (P < 0.05), respectively) after 48 h. These changes were also observed in KB cells, although to a lesser extent. Furthermore, in HEp-2 cells, GALR2-mediated apoptosis was caspase-independent, involving downregulation of ERK1/2, followed by induction of the pro-apoptotic Bcl-2 protein, Bim. These results illustrate that transient GALR2 expression in the presence of galanin induces apoptosis via diverse pathways and serves as a platform for suicide gene therapy against HNSCC.
authors.affiliation: Department of Otorhinolaryngology, Head and Neck Surgery, Graduate School of Medicine, University of the Ryukyus, Nishihara, Japan; Division of Genetic Therapeutics, Center for Molecular Medicine, Jichi Medical University, Shimotsuke, Japan; Department of Otolaryngology, Head and Neck Surgery, Jichi Medical University School of Medicine, Shimotsuke, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Uehara
authors.forename: Takeharu
authors.initials: T
authors.lastname: Kanazawa
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Mizukami
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Uchibori
authors.forename: Tomonori
authors.initials: T
authors.lastname: Tsukahara
authors.forename: Masashi
authors.initials: M
authors.lastname: Urabe
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kume
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Misawa
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Carey
authors.forename: Mikio
authors.initials: M
authors.lastname: Suzuki
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ichimura
authors.forename: Keiya
authors.initials: K
authors.lastname: Ozawa
mesh_terms: D017209:Apoptosis / Q000502:physiology; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015536:Down-Regulation; D016193:G1 Phase / Q000502:physiology; D019004:Galanin / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006258:Head and Neck Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007624:KB Cells; D020935:MAP Kinase Signaling System; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D044092:Receptor, Galanin, Type 2 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D016192:Resting Phase, Cell Cycle / Q000502:physiology; D015398:Signal Transduction; D000077195:Squamous Cell Carcinoma of Head and Neck; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D044092:Receptor, Galanin, Type 2; D025521:Tumor Suppressor Proteins; D019004:Galanin; D020169:Caspases
keywords: Adeno‐associated virus vector; Bim; extracellular signal‐regulated kinases 1/2; galanin receptor; head and neck squamous cell carcinoma