Prognostic effect of programmed cell death ligand 1/programmed cell death 1 expression in cancer stem cells of human oral squamous cell carcinoma

Keita Todoroki; Yushi Abe; Katsuhisa Matsuo; Hidetoshi Nomura; Akihiko Kawahara; Yoshiaki Nakamura; Moriyoshi Nakamura; Naoko Seki; Jingo Kusukawa

doi:10.3892/ol.2024.14213

Prognostic effect of programmed cell death ligand 1/programmed cell death 1 expression in cancer stem cells of human oral squamous cell carcinoma

Oncol Lett. 2024 Jan 4;27(2):79. doi: 10.3892/ol.2024.14213. eCollection 2024 Feb.

Authors

Keita Todoroki^{1

2}, Yushi Abe^{1

2}, Katsuhisa Matsuo^{1

2}, Hidetoshi Nomura¹, Akihiko Kawahara³, Yoshiaki Nakamura⁴, Moriyoshi Nakamura¹, Naoko Seki¹, Jingo Kusukawa¹

Affiliations

¹ Dental and Oral Medical Center, Kurume University, School of Medicine, Kurume, Fukuoka 830-0011, Japan.
² Department of Dental and Oral Surgery, Takagi Hospital, Kouhoukai Medical Corporation, Okawa, Fukuoka 831-0016, Japan.
³ Department of Diagnostic Pathology, Kurume University Hospital, Kurume, Fukuoka 830-0011, Japan.
⁴ Department of Dentistry and Oral Surgery, Oita Saiseikai Hita Hospital, Hita, Oita 877-1292, Japan.

Abstract

The relationship between cancer stem cells (CSCs) in oral squamous cell carcinoma (OSCC) and programmed cell death ligand 1 (PD-L1)/programmed cell death 1 (PD-1) remains unclear. Therefore, the present study aimed to clarify the association between the CD44v3^high/CD24^low immunophenotype of CSCs in OSCC and PD-L1/PD-1 co-expression, and to assess the prognostic effect of CSCs in terms of immune checkpoint molecules. Formalin-fixed, paraffin-embedded tissue samples and clinicopathological data from 168 patients with OSCC were retrospectively retrieved. Immunohistochemical staining and reverse transcription quantitative polymerase chain reaction were applied to a tissue microarray of the invasive front of each case. Semi-automated cell counting was used to assess CD44v3, CD24, PD-L1 and PD-1 expression by immunohistochemistry (IHC) using a digital image analysis program. Associations between immunological markers and clinicopathological variables were estimated. Patients with the CSC immunophenotype CD44v3^high/CD24^low, and patients with a high PD-L1/PD-1-positive cell density in the tumor parenchyma and stroma had significantly lower survival rates. Furthermore, patients with the CSC immunophenotype (CD44v3^high/CD24^low) and high PD-L1/PD-1 co-expression had even lower survival rates (P<0.01, log-rank test). Notably, there was a positive correlation between CD44v3 and PD-L1 expression (τ=0.1096, P=0.0366, Kendall rank correlation coefficient) and a negative correlation between CD24 and PD-1 expression (τ=-0.1387, P=0.0089, Kendall rank correlation coefficient). Additionally, the high CD44v3 expression group, as determined by IHC, exhibited significantly decreased expression of U2 small nuclear RNA auxiliary factor 1 (U2AF1) at the mRNA level compared with that in the low CD44v3 expression group (P<0.001, Mann-Whitney U test), and U2AF1 and PD-L1 mRNA expression exhibited a significant negative correlation (τ=-0.3948, P<0.001, Kendall rank correlation coefficient). In conclusion, CSCs in OSCC may evade host immune mechanisms and maintain CSC stemness via PD-L1/PD-1 co-expression, resulting in unfavorable clinical outcomes.

Keywords: CD24; CD44v3; CSC; OSCC; immune checkpoint inhibitors; programmed cell death 1; programmed cell death ligand 1.

Grants and funding

This study was supported by a Grant-in-Aid for Scientific Research (grant no. 20K18714) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.