Vitamin D inhibits the proliferation of Oral Squamous Cell Carcinoma by suppressing lncRNA LUCAT1 through the MAPK pathway

Background: Oral squamous cell carcinoma (OSCC) is the most common type of oral cancer worldwide. Recent studies have suggested that vitamin D (VitD) is associated with a reduced risk of many chronic illnesses, including cancer. However, the role of vitamin D in OSCC has rarely been reported. Materials and Methods: The effect of vitamin D and control treatment were examined by cell clone formation assay. Using RNA-seq, we globally identified VitD-regulated long noncoding RNAs (lncRNAs). The expression of LUCAT1 in OSCC tissues and cell lines was examined by qRT-PCR. The correlation between LUCAT1 expression level and clinicopathological characteristics was analyzed. The biological roles of LUCAT1 in OSCC cell proliferation was determined by CCK8 and cell colony formation. The role of LUCAT1 in OSCC growth was further confirmed by mouse xenograft tumor model. Combined with the literature, the mechanism of action of LUICAT1 was verified by western blot. Results: In this study, we observed that VitD inhibited tumour cell growth in OSCC. We found that lncRNA LUCAT1 was downregulated by VitD and served as an important mediator of VitD in inhibiting OSCC cell proliferation. Moreover, we observed that the expression of LUCAT1 was significantly upregulated in OSCC tissues compared to non-tumour tissues. We further demonstrated that LUCAT1 promoted the proliferation of oral cancer cells by enhancing the activation of the mitogen protein kinase (MAPK) signalling pathway. Conclusion: In summary, our results show that VitD inhibited the growth of OSCC cells through the LUCAT1-MAPK signalling pathway. Our study suggested that VitD could suppress the progression of oral cancer, and LUCAT1 may be a potential tumour marker for the diagnosis and prognosis of OSCC.