Abstract:

Objective To discuss the expressions of procollagen-lysine， 2-oxoglutarate 5-dioxygenase 1 （PLOD1） in oral squamous cell carcinoma （OSCC） tissue and OSCC cells and its effect on the biological behavior of the OSCC cells， and to clarify the potential of PLOD1 as a prognostic biomarker for OSCC. Methods The expression level of PLOD1 mRNA in head and neck squamous cell carcinoma （HNSC） tissue and its correlation with the survival of the HNSC patients were analyzed by Tumor Immune Estimation Resource （TIMER）， Gene Expression Profiling Interactive Analysis （GEPIA）， and Kaplan-Meier Plotter databases. Immunohistochemistry method was used to detect the expression level of PLOD1 protein in 110 OSCC tissue and 64 adjacent tissue，and its association with clinicopathological characteristics and prognosis of the OSCC patients were analyzed； the diagnostic value of PLOD1 in OSCC was detected by area under the curve （AUC） of the receiver operating characteristic （ROC）. The expression levels of PLOD1 mRNA and protein in the human normal oral epithelial HOK cells and OSCC SCC15 and CAL27 cells were detected by real-time fluorescence quantitative PCR （RT-qPCR） and Western blotting methods. The small interfering RNA （siRNA） fragments were transfected into the SCC15 cells by liposome method and the cells were dividing into si-NC group （transfected with negative control si-NC） and si-PLOD1 group （transfected with si-PLOD1）； the proliferation activities， scratch healing rates， and numbers of invasion cells in two groups were detected by CCK-8 method， wound healing assay， and Transwell chamber assay， respectively. Results The public database analysis results showed that the expression level of PLOD1 mRNA in HNSC tissue was higher than that in adjacent tissue（P<0.05）； compared with low expression of PLOD1 group， the survival period of the HNSC patients in high expression of PLOD1 group was shorter （HR=1.41， P=0.018）. The PLOD1 protein was mainly expressed in cytoplasm of the OSCC cells， and the expression intensity of PLOD1 in OSCC tissue was higher than that in adjacent tissue （P<0.01）， and it was related to T stage and TNM stage of the OSCC patients （P=0.021， P=0.004）. The AUC of PLOD1 for diagnosing OSCC was 0.811， and the specificity was 63.64% and the sensitivity was 90.63%. The Kaplan-Meier survival analysis results showed that compared with low expression of PLOD1 group， the survival rate of the OSCC patients in high expression of PLOD1 group was decreased （P<0.01）.The COX regression analysis results showed that high expression of PLOD1 was an independent risk factor for the prognosis of OSCC （P=0.012）. The expression levels of PLOD1 mRNA and protein in the OSCC cells were higher than those in HOK cells （P<0.05）. Compared with si-NC group， the proliferation activity and scratch healing rate of the cells in si-PLOD1 group were decreased （P<0.05）， and the number of invasion cells was decreased（P<0.01）. Conclusion PLOD1 is highly expressed in the OSCC tissue and cells， and silencing of PLOD1 expression can inhibit the proliferation， migration， and invasion of the OSCC cells. PLOD1 may be a new therapeutic target and prognostic biomarker for OSCC.

Key words: Oral squamous cell carcinoma, Procollagen-lysine， 2-oxoglutarate 5-dioxygenase 1, Cell proliferation, Cell invasion, Prognosis