PAQR3 Inhibits the Proliferation and Tumorigenesis in Esophageal Cancer Cells

Abstract

Progestin and adipoQ receptor family member III (PAQR3), a member of the PAQR family, is frequently downregulated in different types of human cancer. However, its expression and functions in esophageal cancer are still unknown. This study aimed to explore the expression of PAQR3 in esophageal cancer cell lines and to investigate the role of PAQR3 in the development of esophageal cancer. Our data showed that PAQR3 is expressed in low amounts in human esophageal cancer cell lines. Overexpression of PAQR3 significantly suppressed the proliferation, migration, and invasion of esophageal cancer cells. In addition, overexpression of PAQR3 downregulated the protein expression levels of RAF1, p-MEK1, and p-ERK1/2 in esophageal cancer cells. Furthermore, overexpression of PAQR3 attenuated the tumor growth in a tumor xenograft model. In conclusion, we demonstrated that overexpression of PAQR3 suppresses cell proliferation, migration, and invasion in esophageal cancer in vitro and in vivo. Therefore, PAQR3 may act as a therapeutic target for human esophageal cancer.

Figure 1

PAQR3 is lowly expressed in human esophageal cancer cell lines. (A) The mRNA expression of PAQR3 in esophageal cancer cell lines was analyzed by qRT-PCR. (B) The mRNA expression of PAQR3 was detected in esophageal cancer cell lines by Western blot analysis and quantified using Image-Pro Plus 6.0 software. Data are expressed as mean ± SD. n = 3. *p < 0.05 versus HEEC group.

Figure 2

Overexpression of PAQR3 inhibits esophageal cancer cell proliferation. EC9706 cells were infected with PAQR3 or vector for 24 h. (A) The mRNA expression of PAQR3 was detected by qRT-PCR. (B) The protein expression of PAQR3 was evaluated using Western blotting. (C) Cell proliferation was determined by the CCK-8 assay. Data are expressed as mean ± SD. n = 3. *p < 0.05 versus vector group.

Figure 3

Overexpression of PAQR3 inhibits esophageal cancer cell migration and invasion. EC9706 cells were infected with PAQR3 or vector for 24 h. (A) The migration of EC9706 cells was determined using in vitro Transwell migration assay. (B) The invasion of EC9706 cells was determined using in vitro Transwell insert invasion assay. (C) The protein levels of E-cadherin, N-cadherin, and vimentin were determined by Western blot. The relative protein levels were quantified using Image-Pro Plus 6.0 software. Data are expressed as mean ± SD. n = 3. *p < 0.05 versus vector group.

Figure 4

Overexpression of PAQR3 inhibits the activation of the RAF/MEK/ERK pathway in esophageal cancer cells. EC9706 cells were infected with PAQR3 or vector for 24 h. (A) Protein levels of RAF1, MEK1, p-MEK1, ERK1/2, and p-ERK1/2 were determined by Western blot. (B) The relative protein levels were quantified using Image-Pro Plus 6.0 software. EC9706 cells were infected with PAQR3 or vector in the presence or absence of the MEK-specific inhibitor U0126 (1 μM) for 24 h. (C) Cell proliferation was detected by the CCK-8 assay. (D) Cell invasion was evaluated by the in vitro Transwell insert invasion assay. Data are expressed as mean ± SD. n = 3. *p < 0.05.

Figure 5

Overexpression of PAQR3 attenuates the growth of xenograft tumor. Infected EC9706 cells at 1 × 10⁶ cells/0.1 ml were injected subcutaneously into the flank of nude mice. (A) Tumor weights were measured at day 20. (B) Tumor volumes were calculated in each group every 5 days from day 0 to day 20. Data are expressed as mean ± SD. n = 5. *p < 0.05 versus vector group.