Proto-oncogene RTL4 promotes tumorigenesis and invasiveness of papillary thyroid cancer

Although the prognosis of papillary thyroid carcinoma (PTC) is good, its widespread prevalence still degrades the quality of life of tens of thousands of patients. PTC can even be life-threatening as a result of its aggressiveness and metastasis.

Using complete transcriptome sequence analysis, cutting-edge research has revealed many tumor-associated genes. These related genes help us better understand the tumorigenesis and progression of PTC. We discovered that retrotransposon Gag like 4 (RTL4) is a novel potential PTC-associated gene. By Quantitative real-time polymerase chain reaction (qRT-PCR), we observed an obvious upregulation of RTL4 in PTC tissue. And, we validated the expression characteristics of RTL4 using data from the Cancer Genome Atlas (TCGA). Furthermore, we down-regulated RTL4 expression levels in relevant cell lines and studied the biological function of the RTL4 line in PTC by cell proliferation, colony formation, migration and invasion assays.

In the present study, high expression of RTL4 suggested lymph node metastasis (P = 0.028) and was associated with the pathological type (P = 0.001). RTL4 had the validity of distinguishing PTC tissues and normal tissues showed an AUC of 87.53% for the TCGA data set. The downregulation of RTL4 in the PTC cell lines distinctly inhibited cell colony formation, proliferation, migration, and invasion.

The result revealed RTL4 is closely related to the occurrence and development of PTC. RTL4 may participate in the HOTAIR-miR-206-ZCCHC16 ceRNA regulatory network and be regulated and play a role in the ceRNA regulatory network. It may be used as a target or indicator for the treatment and prognosis of PTC.