title: Programmed cell death protein 1 and programmed death-ligand 1 are expressed on the surface of some small-cell lung cancer lines.
abstract: BACKGROUND
  Programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) play a major role in suppressing the immune system during the formation of the PD-1/PD-L1 pathway, which transmits an inhibitory signal to reduce T cell activity. PD-L1 is often expressed in various malignant tumors. In contrast, PD-1 is generally observed in activated lymphocytes and myeloid-derived dendritic cells. Of the malignant cells, only Jurkat cells under special conditions and angioimmunoblastic T-cell lymphoma tissue cells express PD-1 on their surface.
  
  
  METHODS
  To clarify whether the PD-1/PD-L1 pathway participates in the immunotolerance of small-cell lung cancer (SCLC) cells, we examined the expressions of PD-1 and PD-L1 on the cell surface of SCLC cell lines using flow cytometry and reverse transcription polymerase chain reaction.
  
  
  RESULTS
  Among the four SCLC cell lines examined, only SBC-3 expressed both PD-1 and PD-L1.
  
  
  CONCLUSIONS
  We demonstrated that both PD-1 and PD-L1 molecules were co-expressed on the surface of SCLC cells. Although the biological implications of this remain unclear, we speculate that PD-1 and its ligand on the SCLC cells may participate in the growth inhibition of tumor cells as reported in cytotoxic T cells.
authors.affiliation: Department of General Internal Medicine 4, Kawasaki Medical School 2-1-80 Nakasange, Kita-ku, Okayama 700-8505, Japan.
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Yamane
authors.affiliation: Department of General Internal Medicine 4, Kawasaki Medical School 2-1-80 Nakasange, Kita-ku, Okayama 700-8505, Japan ; Department of Allergy and Respiratory Medicine (Thoracic Oncology), Okayama University Hospital 2-5-1, Shikata-cho, Kitaku, Okayama, 700-8558, Japan.
authors.forename: Hideko
authors.initials: H
authors.lastname: Isozaki
authors.affiliation: Department of General Internal Medicine 4, Kawasaki Medical School 2-1-80 Nakasange, Kita-ku, Okayama 700-8505, Japan.
authors.forename: Masami
authors.initials: M
authors.lastname: Takeyama
authors.affiliation: Department of General Internal Medicine 4, Kawasaki Medical School 2-1-80 Nakasange, Kita-ku, Okayama 700-8505, Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Ochi
authors.affiliation: Department of Allergy and Respiratory Medicine (Thoracic Oncology), Okayama University Hospital 2-5-1, Shikata-cho, Kitaku, Okayama, 700-8558, Japan.
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Kudo
authors.affiliation: Department of General Internal Medicine 4, Kawasaki Medical School 2-1-80 Nakasange, Kita-ku, Okayama 700-8505, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Honda
authors.affiliation: Department of General Internal Medicine 4, Kawasaki Medical School 2-1-80 Nakasange, Kita-ku, Okayama 700-8505, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Yamagishi
authors.affiliation: Department of Allergy and Respiratory Medicine (Thoracic Oncology), Okayama University Hospital 2-5-1, Shikata-cho, Kitaku, Okayama, 700-8558, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Kubo
authors.affiliation: Department of Allergy and Respiratory Medicine (Thoracic Oncology), Okayama University Hospital 2-5-1, Shikata-cho, Kitaku, Okayama, 700-8558, Japan.
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kiura
authors.affiliation: Department of General Internal Medicine 4, Kawasaki Medical School 2-1-80 Nakasange, Kita-ku, Okayama 700-8505, Japan.
authors.forename: Nagio
authors.initials: N
authors.lastname: Takigawa
keywords: PD-1; PD-L1; Small-cell lung cancer; cell line; co-expression