Effects of cancer-testis antigen, TFDP3, on cell cycle regulation and its mechanism in L-02 and HepG2 cell lines in vitro

Abstract

TFDP3, also be known as HCA661, was one of the cancer-testis antigens, which only expressed in human tissues. The recent researches about TFDP3 mostly focused on its ability to control the drug resistance and apoptosis of tumor cells. However, the role of TFDP3 in the progress of the cell cycle is rarely involved. In this study, we examined the expression of TFDP3 in human liver tissues firstly. After that, we detect the expression of TFDP3 at the RNA level and protein level in L-02 cell line and HepG2 cell line, and the location of TFDP3 was defined by immunofluorescence technique. Furthermore, we synchronized the cells to G1 phase, S phase and G2 phase, and arrested cell mitosis. The localization of TFDP3 and co-localization with E2F1 molecules in different phases of hepatocyte lines. Finally, TFDP3 gene knockout was performed on L-02 and HepG2 cell lines, and detected the new cell cycles by flow cytometry. The result showed that the expression of TFDP3 molecule is negative in normal liver tissue, but positive in immortalized human hepatocyte cell line, and the expression level is lower than in hepatocellular carcinoma cell line. The expression level of TFDP3 was in the dynamic change of L-02 and HepG2 cell lines, and was related to the phase transition. TFDP3 can bind to E2F1 molecule to form E2F/TFDP3 complex; and the localizations of TFDP3 and E2F1 molecules and the co-localization were different in different phases of cell cycle in the nucleus and cytoplasm, which indicated that the E2F/TFDP3 complex involved in the process of regulating the cell cycle. By knocking down the TFDP3 expression level in L-02 and HepG2 cell lines, the cell cycle would be arrested in S phase, which confirmed that TFDP3 can be a potential target for tumor therapy.

Development and validation of epithelial mesenchymal transition-related prognostic model for hepatocellular carcinoma

“…TFDP3 is a new transcription regulator of E2F, which can inhibit the binding and transcriptional activity of E2F with DNA. Jiao et al’s study indicated that the E2F/TFDP3 complex was involved in cell cycle regulation [ 45 ].…”

TFDP3 as E2F Unique Partner, Has Crucial Roles in Cancer Cells and Testis

“…Most E2Fs, TFDP1 and TFDP2 are predominately nuclear, but E2F4 and E2F5 show cell cycle-specific localization ( 33 – 35 ). Furthermore, we found that subcellular location of TFDP3 is cell cycle specific, it is expressed in the nucleus in G1 phase and at the end of mitosis, in the cytoplasm in S phase and G2 phase ( 15 ). Thus, in quiescent cells, repressed E2F4 and E2F5 interacted mainly with TFDP1 or TFDP2, binding with E2F-targeted promoters and blocking the transcription of cell cycle-related genes.…”

“…As expected, we verified that TFDP3 is expressed in the nucleus mainly at the end of mitosis phase, diffusively in G1 phase, and in the cytoplasm in G2 phase. Moreover, we detected that TFDP3 is highly expressed in S phase by Western blot of synchronous cells ( 15 ). Interestingly, a study of TFDP3 in prostate cancer emphasized that TFDP3 was coexpressed with E2F1.…”

“…Therefore, TFDP3 functions as an inhibitor of E2F-regulated cell cycle progress. Accumulated evidences showed that knocking down the TFDP3 in L-02 and HepG2 cell lines by siRNA interference, the cells are blocked in the S phase, consequently TFDP3 participates in the process of G1 phase entry into S phase ( 15 ). Furthermore, the DNA-binding activity of TFDP3 is required for the cell cycle effects ( 2 ).…”

“…Indeed, knocking down the endogenic TFDP3 increases the proportion of cells in S phase. The properties of the TFDP3/E2F1 complex appear to be more related to the induction of G2 cells ( 2 , 15 ).…”