The role of PD-L1 gene silencing on growth, migration, and apoptosis in oral squamous carcinoma cell line HN-5

Introduction and Importance: Oral Cavity Squamous Cell Carcinoma (OCSCC) presents a major risk to worldwide health. Its advancement is often associated with elevated concentrations of Programmed Cell Death Protein 1 (PD-1) and Programmed Death-Ligand 1 (PD-L1), which create an immunosuppressive environment, hindering the capability of the immune system to fight tumors. By targeting PD-L1 through gene silencing, there is potential to enhance immune responses against OCSCC and inhibit tumor growth. This study explores the impact of PD-L1 suppression on the HN-5 OCSCC cell line, with a focus on cell growth, apoptosis, cell cycle progression, and migration. Methods: We evaluated the effects of PD-L1 gene silencing on the proliferation and survival of HN-5 cells using the MTT assay. Flow cytometry was utilized to investigate apoptosis induction and cell cycle arrest in cells with reduced PD-L1 expression. A wound healing test was performed to assess the impact of PD-L1 silencing on the movement of OCSCC cells. Additionally, Quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) was conducted to analyze the expression of genes related to apoptosis. Results: The use of PD-L1 small interfering RNA (siRNA) effectively lowered PD-L1 mRNA levels in HN-5 cells, resulting in reduced cell proliferation. Knockdown of PD-L1 leading to enhanced apoptosis and a halt in the cell cycle during the G1 phase. Further analysis indicated that silencing PD-L1 upregulated Caspase-9 (CAS-9), cellular Myelocytomatosis oncogene (c-Myc), and Bcl-2-associated X protein (Bax), while lowering the levels of B-Cell Lymphoma 2 (BCL-2). The migratory ability of cells treated with PD-L1 siRNA was significantly diminished compared to control cells. Conclusion: I n summary, our findings suggest that knocking down PD-L1 in the HN-5 cell line could serve as a promising approach for treating oral cavity squamous cell carcinoma (OCSCC). This highlights how crucial the PD-1/PD-L1 pathway is in the formation and progression of these types of tumors.