1. Respiratory Center, Asahikawa Medical University, Asahikawa, Hokkaido 078-8510, Japan
2. Center for Advanced Research and Education, Asahikawa Medical University, Asahikawa, Hokkaido 078-8510
3. Department of Surgical Pathology, Asahikawa Medical University Hospital, Asahikawa, Hokkaido 078-8510, Japan
4. Department of Otolaryngology-Head and Neck Surgery, Asahikawa Medical University, Asahikawa, Hokkaido 078-8510, Japan
5. Department of Pathology, Asahikawa Medical University, Asahikawa, Hokkaido 078-8510, Japan
6. Institute of Biomedical Research, Sapporo Higashi Tokushukai Hospital, Sapporo, Hokkaido 065-0033, Japan