Antimicrobial peptide LL-37 serves a function in the host defense against microbial invasion, and also regulates cell proliferation, immune activity and angiogenesis. Previous studies have reported that LL-37 participates in the development of numerous tumour types, such as ovarian cancer, lung cancer, melanoma and breast cancer. However, the function of LL-37 in the development of skin squamous cell carcinoma (SCC) has not yet been fully elucidated. The aim of the current study was to investigate how LL-37 promotes the expression of Y-box binding protein 1 (YB-1) in SCC. Short interfering RNA (siRNA) was used to inhibit the expression of YB-1, and in vitro MTT and Transwell migration assays were used to evaluate the effect of reduced YB-1 on the viability and invasion of A431 cells. A431 cells were stimulated with LL-37, and quantitative polymerase chain reaction, immunofluorescence and western blot analyses were used to detect changes in YB-1 expression. Mitogen-activated protein kinase kinase, mitogen-activated protein kinase and nuclear factor (NF)-κB signaling pathway inhibitors were also used to evaluate the mechanism of LL-37-induced YB-1 protein expression. It was found that YB-1 expression was increased in SCC tissue compared with normal tissue. Inhibiting YB-1 expression using siRNA significantly reduced the viability and suppressed the invasion of tumour cells (P<0.05 for both). LL-37 treatment at 0.05 µg/ml for 24 or 48 h significantly promoted YB-1 protein expression (P<0.05), and this was dependent on the NF-κB signaling pathway. In conclusion, the current study demonstrated that by upregulating the expression of YB-1, LL-37 can promote the occurrence and development of SCC, and this process involves the NF-κB signaling pathway.
Keywords: LL-37; Y-box binding protein 1; epidermis growth factor receptor; nuclear factor-κB; squamous cell carcinoma.