High expression of apolipoprotein C1 promotes proliferation and inhibits apoptosis of papillary thyroid carcinoma cells by activating the JAK2/STAT3 signaling pathway

doi:10.12122/j.issn.1673-4254.2025.02.17

Abstract

Abstract:

Objective To investigate the expression of apolipoprotein C1 (APOC1) in papillary thyroid carcinoma (PTC) and its effects on proliferation and apoptosis of PTC cells. Methods The expression level of APOC1 in PTC and its impact on prognosis were analyzed using GEPIA 2 and Kaplan-Meier databases. Immunohistochemistry (IHC) and Western blotting were used to detect the expression of APOC1 in PTC and adjacent tissues and in 3 PTC cell lines and normal thyroid Nthyori 3-1 cells. In TPC-1 and BCPAP cells, the effect of Lipofectamine 2000-mediated transfection with APOC1 siRNA or an APOC1-overexpressing plasmid on cell growth and colony formation ability were examined by observing the growth curves and using colony-forming assay. The changes in cell cycle and apoptosis of the transfected cells were analyzed with flow cytometry. RT-qPCR and Western blotting were used to detect the changes in expressions of P21, P27, CDK4, cyclin D1, Bcl-2, Bax, caspase-3 and caspase-9 and the key proteins in the JAK2/STAT3 signaling pathway. Results APOC1 expression was significantly higher in PTC tissues and the 3 PTC cell lines than in the adjacent tissues and Nthyori 3-1 cells, respectively. In TPC-1 and BCPAP cells, APOC1 knockdown obviously reduced cell proliferative activity, increased the percentage of G0/G1 phase cells, lowered the percentages of S and G2 phase cells, promoted cell apoptosis, and downregulated mRNA and protein expression levels of CDK4, cyclin D1 and Bcl-2 and the protein levels of p-JAK2 and p-STAT3. APOC1 overexpression in the cells produced the opposite effects on cell proliferation, apoptosis, cell cycle and the mRNA and protein expressions. The application of AG490, a JAK2 inhibitor, strongly attenuated APOC1 overexpression-induced activation of the JAK2/STAT3 signaling pathway in BCPAP cells. Conclusion APOC1 overexpression promotes proliferation and inhibits apoptosis of PTC cells possibly by activating the JAK2/STAT3 signaling pathway and accelerating cell cycle progression.

Key words: papillary thyroid carcinoma, apolipoprotein C1, proliferation, apoptosis, JAK2/STAT3 signaling pathway

Yu BIN, Ziwen LI, Suwei ZUO, Sinuo SUN, Min LI, Jiayin SONG, Xu LIN, Gang XUE, Jingfang WU. High expression of apolipoprotein C1 promotes proliferation and inhibits apoptosis of papillary thyroid carcinoma cells by activating the JAK2/STAT3 signaling pathway[J]. Journal of Southern Medical University, 2025, 45(2): 359-370.

Figures/Tables 14

Tab.1 Primer sequences for RT-qPCR

Gene	Sequence
APOC1	F:5'-CTGGTGGTGGTTCTGTCGAT-3'
	R:5'-TCACTCTGTTTGATGCGGCT-3'
β-actin	F:5'-CCTGGGCATGGAGTCCTGTG-3'
	R:5'-AGGGGCCGGACTCGTCATAC-3'

Fig.1 Bioinformatic analysis of APOC1 expression in PTC and Adjacent tissues. A: Analysis of expression levels of APOC1 in PTC tissues and adjacent tissues using GEPIA 2 database (*P<0.05). B, C: Analysis of the relationship between APOC1 mRNA expression and patient prognosis using Kaplan-Meier database.

Fig.2 Expression of APOC1 in clinical samples of PTC and adjacent tissues. A: Western blotting for detecting APOC1 expression in PTC tissues and adjacent tissues. B: Quantitative analysis of expression level. ***P<0.001 vs adjacent tissue.

Fig.3 Immunohistochemical detection of APOC1 expression in PTC and Adjacent tissue. A: APOC1 positive signal in PTC tissue (brown) in the cytoplasm. B: Negative expression of APOC1 in adjacent tissue.

Fig.4 Immunocytochemical detection of APOC1 protein in TPC-1, K1, BCPAP and Nthyori 3-1 cells. A: Negative expression of APOC1 in normal thyiod follicular epithelial Nthyori 3-1 cells. B-D: Positive signals of APOC1 in the 3 PTC cell lines located in the cytoplasm.

Fig.5 Western blotting and RT-qPCR for detecting APOC1 expression in K1, TPC-1, BCPAP and Nthyori 3-1 cells. A,B: Expression levels of APOC1 protein in different cell lines detected by Western blotting. C: Expression levels of APOC1 mRNA in different cell lines. ***P<0.001, ****P<0.0001 vs Nthyori 3-1 cells (n=3).

Fig.6 Expression of APOC1 protein and mRNA in TPC-1 cells with APOC1 knockdown. A,B: Expression levels of APOC1 protein in TPC-1 cells with APOC1 knockdown detected by Western blotting. C: Expression levels of APOC1 mRNA in TPC-1 cells with APOC1 knockdown. *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001 vs shRNAC (n=3).

Fig.7 Decreased APOC1 expressions at both protein and mRNA levels in TPC-1 cells with APOC1 knockdown. A, B: Expression levels of APOC1 protein in shRNAC group, shRNA1 group, and shRNA2 group. C: Expression levels of APOC1 mRNA in the shRNAC group, shRNA1 group, and shRNA2 group. *P<0.05, **P<0.01, ***P<0.001 vs shRNAC (n=3).

Fig.8 Increased APOC1 protein and mRNA levels in BCPAP cells with APOC1 overexpression. A, B: Expression levels of APOC1 protein in OENC and OE groups. C: Expression levels of APOC1 mRNA in OENC and OE groups. **P<0.01, ****P<0.0001 vs OENC (n=3).

Fig.9 Effect of APOC1 knockdown and overexpresison on PTC cell proliferation. A, C: Colony formation assay of the transfected cells. B,D: Number of cell clusters in the transfected cells. E,G: Growth curves of the transfected cells. F,H: Cell confluence of the transfected cells. *P<0.05,**P<0.01,***P<0.001, ****P<0.001 vs shRNAC/OENC (n=3).

Fig.10 Effect of APOC1 knockdown and overexpresison on cell cycle. A, C: Cell cycle diagrams of the cells with APOC1 knockdown and overexpresison. B, D: Analysis of cell cycle percentage. *P<0.05, **P<0.01, ***P<0.001 vs shRNAC/OENC (n=3).

Fig.11 Effect of APOC1 knockdown and overexpresison on cell apoptosis. A,C: Cell apoptosis maps of cells with APOC1 knockdown and overexpresison. B,D: Percentages of apoptotic cells each group.**P<0.01, ***P<0.001 vs shRNAC/OENC (n=3).

Fig.12 Effect of APOC1 knockdown and overexpresison on expresisons of cell cycle and apoptosis-related proteins and their mRNA levels. A-C: Cell cycle-related protein and mRNA expression levels of in cells with APOC1 knockdown. D-F: Cell cycle-related protein and mRNA expression levels in APOC1 knockdown group. G-I: Apoptosis-related protein and mRNA expression levels in APOC1 overexpression group. J-L: Apoptosis-related protein and mRNA expression levels in APOC1 knockdown group. *P<0.05, **P<0.01,***P<0.001, ****P<0.0001 vs shRNAC/OENC (n=3).

Fig.13 APOC1 knockdown and overexpresison on expressions of key proteins in the JAK2/STAT3 signaling pathway detected by Western blotting. A,B: Expression levels of key proteins in the JAK2/STAT3 signaling pathway in APOC1 knockdown group. C,D: Expression levels of key proteins in the JAK2/STAT3 signaling pathway in APOC1 overexpression group. **P<0.01, ***P<0.001, ****P<0.0001 vs shRNAC/OENC (n=3).

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