LncRNA TP53TG1 Promotes the Growth and Migration of Hepatocellular Carcinoma Cells via Activation of ERK Signaling

Abstract

Long non-coding RNA (lncRNA) TP53 target 1 (TP53TG1) was discovered as a TP53 target gene. TP53TG1 has been reported as having dual roles by exerting tumor-suppressive and oncogenic activities that vary depending on the cancer type. Yet, the role of TP53TG1 in hepatocellular carcinoma (HCC) is not fully understood. In this study, we performed both gain- and loss-of-function studies to determine the biological role of TP53TG1 in HCC. We found that the knockdown of TP53 in HCC cells caused the upregulation of TP53TG1. Furthermore, we found that the knockdown of TP53TG1 not only suppressed HCC cell proliferation and migration, but also reduced intrinsic ERK signaling. In contrast, the overexpression of TP53TG1 increased ERK activation and enhanced HCC proliferation. In conclusion, our study reveals an oncogenic role of TP53TG1 in HCC, which provides a novel insight into the cell-type-specific function of TP53TG1 in HCC.

Keywords: ERK pathway; TP53TG1; hepatocellular carcinoma; long non-coding RNA; oncogene.

Figure 1

TP53TG1 is regulated by TP53 in HepG2. (A–C) qPCR analysis of TP53, TP53TG1, and p21 (normalized to 18S) in HepG2 cells transfected with lacz siRNA or TP53 siRNAs (A), HepG2 cells transfected with lacz siRNA or TP53TG1 siRNAs (B), and HepG2 cells transfected with control or TP53TG1 overexpression adenovirus (C). Error bars represent SEM, n = 3, * p < 0.05 (si-RNA vs. si-lacz).

Figure 2

Knockdown of TP53TG1 suppresses cell proliferation and migration in HepG2. (A–C) The RNA expression level of TP53TG1 (normalized to 18S), n = 3 (A), proliferation rate, error bars represent SD, n = 6 (B) and migration rate, n = 3 (C) in HepG2 cells transfected with lacz siRNA or TP53TG1 siRNAs. * p < 0.05 (si-RNA vs. si-lacz).

Figure 3

Knockdown of TP53TG1 suppresses cell proliferation and migration in PLC/PRF/5. (A–C) The RNA expression level of TP53TG1 (normalized to 18S), n = 3 (A), proliferation rate, error bars represent SD, n = 6 (B) and migration rate, n = 3 (C) in PLC/PRF/5 cells transfected with lacz siRNA or TP53TG1 siRNAs. * p < 0.05 (si-RNA vs. si-lacz).

Figure 4

Knockdown of TP53TG1 inhibits ERK signaling. (A,B) Protein expression level (left) and quantification (right) of p-ERK1/p-ERK2 and ERK1/ERK2 in HepG2 cells (A) or PLC/PRF/5 cells (B) transfected with lacz siRNA or TP53TG1 siRNAs. The protein expression levels of p-ERK1 and p-ERK2 were normalized to ERK1 and EKR2, respectively. Error bars represent SEM, * p < 0.05 (si-RNA vs. si-lacz).

Figure 5

TP53TG1 works through the ERK pathway. (A,B) Protein expression level (top) and quantification (bottom) of p-ERK1/p-ERK2 and ERK1/ERK2 (A), and cell proliferation rate, error bars represent SD, n = 6 (B) in HepG2 cells treated with si-lacz, si-TP53TG1, si-lacz + LM22B-10, or si-TP53TG1 + LM22B-10. The protein expression levels of p-ERK1 and p-ERK2 were normalized to ERK1 and EKR2, respectively. * p < 0.05.

Figure 6

Overexpression of TP53TG1 increases cell proliferation and ERK activation in HepG2. (A–C) The RNA expression level of TP53TG1 (normalized to 18S), n = 3 (A), proliferation rate, error bars represent SD, n = 6 (B), and protein expression level of p-ERK1/p-ERK2 and ERK1/ERK2 (left) as well as qualification (right) (C) in HepG2 cells transfected with control or TP53TG1 overexpression adenovirus. The protein expression levels of p-ERK1 and p-ERK2 were normalized to ERK1 and EKR2, respectively. * p < 0.05.