Aberrant expression of semaphorin 6B affects cell phenotypes in thyroid carcinoma by activating the Notch signalling pathway.

Abstract

Numerous semaphorins have been widely clarified to be involved in the development of multiple cancers. However, semaphorin 6B (SEMA6B) has not yet been extensively reported in cancers, especially in thyroid carcinoma. Thyroid carcinoma RNA-Seq dataset from the TCGA database was used to assess the expression of SEMA6B in tissues, as well as its clinical significance. We adopted qRT-PCR and western blot analyses to measure the mRNA and protein expression of SEMA6B in thyroid carcinoma cells. The biological roles of SEMA6B in thyroid carcinoma cells were examined through cell counting kit 8, clone formation, and Transwell assays. Also, GSEA was used to identify the gene sets modulated by SEMA6B, which is further verified by western blot. According to the public dataset from the TCGA database, we found that the expression of SEMA6B was upregulated in thyroid carcinoma tissues compared to adjacent non-tumour tissues, and a high level of SEMA6B resulted in a poorer prognosis compared to the low-level SEMA6B group. Functional experiments showed that silencing SEMA6B suppressed the B-CPAP cells viability, invasiveness, and motility, whereas up-regulating SEMA6B in FTC-133 cells led to opposite outcomes. Furthermore, knockdown of SEMA6B in B-CPAP cells could significantly elevate the protein expression of NUMB and reduce the expression of NOTCH1, HES1, and Cyclin D1. Conversely, overexpression of SEMA6B in FTC-133 cells presented opposite results on the protein expression of these Notch signalling pathway-related markers. Our findings demonstrated that SEMA6B exerts a tumourigenic effect in thyroid carcinoma partly by activating Notch signalling pathway, which provides a possible biomarker for the therapeutic intervention in thyroid carcinoma.