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: Takayuki Uehara, Takeharu Kanazawa, Hiroaki Mizukami, Ryosuke Uchibori, Tomonori Tsukahara, Masashi Urabe, Akihiro Kume, Kiyoshi Misawa, Thomas E Carey, Mikio Suzuki, Keiichi Ichimura, Keiya Ozawa
• Journal: Cancer science (Cancer Sci) Vol. 105 Issue 1 Pg. 72-80 (Jan 2014) ISSN: 1349-7006 [Electronic] England
• PMID: 24168112 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2013 The Authors. Cancer Science published by Wiley Publishing Asia Pty Ltd on behalf of Japanese Cancer Association.

Chemical References

• Apoptosis Regulatory Proteins
• BCL2L11 protein, human
• Bcl-2-Like Protein 11
• Membrane Proteins
• Proto-Oncogene Proteins
• Proto-Oncogene Proteins c-bcl-2
• Receptor, Galanin, Type 2
• Tumor Suppressor Proteins
• Galanin
• Caspases

Topics

• Apoptosis (physiology)
• Apoptosis Regulatory Proteins (genetics, metabolism)
• Bcl-2-Like Protein 11
• Carcinoma, Squamous Cell (genetics, metabolism, pathology)
• Caspases (genetics, metabolism)
• Cell Line, Tumor
• Cell Proliferation
• Down-Regulation
• G1 Phase (physiology)
• Galanin (genetics, metabolism)
• Gene Expression
• Head and Neck Neoplasms (genetics, metabolism, pathology)
• Humans
• KB Cells
• MAP Kinase Signaling System
• Membrane Proteins (genetics, metabolism)
• Proto-Oncogene Proteins (genetics, metabolism)
• Proto-Oncogene Proteins c-bcl-2 (genetics, metabolism)
• Receptor, Galanin, Type 2 (biosynthesis, genetics, metabolism)
• Resting Phase, Cell Cycle (physiology)
• Signal Transduction
• Squamous Cell Carcinoma of Head and Neck
• Tumor Suppressor Proteins (biosynthesis, genetics, metabolism)
• Up-Regulation