A novel all-trans retinoic acid derivative inhibits proliferation and induces differentiation of human gastric carcinoma xenografts via up-regulating retinoic acid receptor β

Abstract

Objective: This study is to investigate the in vivo effects of 4-amino-2-trifluoromethyl-phenyl retinate (ATPR) on gastric carcinomas (GC).

Methods: Adult male nude mice were subcutaneously injected with SGC-7901 human gastric cancer cells. Tumor cell cycle was analyzed with flow cytometry. The expression levels of cycloxygenase 2 (COX-2) and carcinoembryonic antigen (CEA) in xenograft tumors were detected with immunohistochemistry. The mRNA and protein expression levels of nuclear retinoic acid receptor β (RARβ) were detected with RT-PCR and Western blot analysis, respectively.

Results: The mean survival time was dramatically increased in the ATPR treatment groups, in a dose-dependent manner. The in vivo results showed that, the xenograft tumor growth was significantly inhibited by the ATPR treatment. Moreover, the percentages of cells in the G0/G1 phase were significantly increased, while the percentages of cells in the S phase were significantly decreased, in the ATPR treatment groups. The serum levels of ALP and LDH were both dramatically decreased in the ATPR treatment groups. Furthermore, immunohistochemistry showed that, the expression levels of COX-2 and CEA were dramatically decreased in the ATPR treatment groups. Importantly, the mRNA and protein expression levels of RARβ in xenograft tumors were apparently increased by the ATPR treatment.

Conclusion: ATPR could inhibit proliferation and induce differentiation of human gastric carcinoma xenografts via up-regulating RARβ expression. ATPR might be a potential effective antitumor agent for the treatment of GC.

Keywords: 4-amino-2-trifluoromethyl-phenyl retinate (ATPR); antitumor effect; differentiation induction; gastric carcinoma; retinoic acid receptor β (RARβ).

Figure 1

Structure of 4-amino-2-trifluoromethyl-phenyl retinate (ATPR).

Figure 2

ATPR increased the survival time of xenograft mouse models. A. The Kaplan-Meier curve for survival. B. Mean survival time in of the xenograft mouse models. n = 8. Compared with the vehicle control group, *P < 0.05.

Figure 3

ATPR inhibited the growth of xenograft tumors in mouse models. (A) Representative photos of tumors in each group at 5 w after modeling. (B, C) Statistical analyses of the weight (B) and volume (C) of the xenograft tumors in mouse models. n = 8. Compared with the vehicle control group, *P < 0.05, **P < 0.01.

Figure 4

ATPR changed the tumor cell cycle in xenograft mouse models. A. Representative flow cytometric histograms for tumor cell cycle analysis. B. Statistical analysis of the cell proportions of the tumor cells. n = 8. Compared with the vehicle control group, *P < 0.05, **P < 0.01.

Figure 5

ATPR decreased the serum levels of ALP and LDH in xenograft mouse models. Serum levels of ALP (A) and LDH (B) were detected in the mouse models. n = 8. Compared with the vehicle control group, *P < 0.05, **P < 0.01.

Figure 6

ATPR decreased the expression levels of COX-2 and CEA in xenograft tumors. The expression levels of COX-2 (A) and CEA (B) in xenograft tumors were detected with immunohistochemistry (×400).

Figure 7

ATPR increased the expression levels of RARβ in xenograft tumors. The mRNA (A) and protein (B) expression levels of RARβ in xenograft tumors were detected with RT-PCR and Western blot analysis, respectively. n = 3. Compared with the vehicle control group, *P < 0.05, **P < 0.01.