15-Deoxy-Δ(12,14)-prostaglandin J2 Induces Apoptosis and Upregulates SOCS3 in Human Thyroid Cancer Cells

Abstract

The cyclopentenone prostaglandin 15-deoxy-Δ(12,14)-prostaglandin J2 (15d-PGJ2) is a natural ligand of peroxisome proliferator-activated receptor gamma (PPAR-γ) and a potential mediator of apoptosis in cancer cells. In the present study, we evaluated the effect of 15d-PGJ2 in human thyroid papillary carcinoma cells (TPC-1) using different doses of 15d-PGJ2 (0.6 to 20 μM) to determine IC50 (9.3 μM) via the MTT assay. The supernatant culture medium of the TPC-1 cells that was treated either with 15d-PGJ2 or with vehicle (control) for 24 hours was assessed for IL-6 secretion via CBA assay. RT-qPCR was used to evaluate mRNA expression of IL-6, SOCS1, SOCS3, and STAT3. TPC-1 cells treated with 15d-PGJ2 decreased the secretion and expression of IL-6 and STAT3, while it increased SOCS1 and SOCS3. Overall, we demonstrated that 15d-PGJ2 downregulated IL-6 signaling pathway and led TPC-1 cells into apoptosis. In conclusion, 15d-PGJ2 shows the potential to become a new therapeutic approach for thyroid tumors.

Figure 1

15d-PGJ₂ decreased the viability of TPC-1 cells. TPC-1 cells were treated with 15d-PGJ₂. (a) represents the cell culture without treatment. (b) Cells treated with 10 μM of 15d-PGJ₂. (c) Viability of the TPC-1 cells treated with 15d-PGJ₂ in the concentrations of 0 to 20 μM. (d) IC₅₀ from cell viability following treatment with 15d-PGJ₂. The data are presented as means ± standard deviation of three replicates from at least three independent tests. An asterisk  ^∗ indicates statistically significant difference from the control (^∗ P > 0.01; ^∗∗∗ P > 0.001).

Figure 2

Fibroblast (FG11) cell proliferation under 15d-PGJ₂ treatment. FG11 cells were treated with 5 to 15 μM of 15d-PGJ₂. The data are presented as means ± standard deviation of three replications from at least three independent tests. 15d-PGJ₂ did not show significant difference from the control at the doses of 5 μM, 10 μM, and 15 μM.

Figure 3

15d-PGJ₂ induced apoptosis in TPC-1 cells. The Annexin V assay revealed that 15d-PGJ₂ induced 47% apoptosis in TPC-1 compared to 5% in the control group. The data are presented as means ± standard deviation of three replicates from at least three independent tests.  ^∗∗∗Statistically significant difference from the control (P > 0.001).

Figure 4

Decreased relative IL-6 mRNA expression and release, TPC-1 cells treated with 15d-PGJ₂. TPC-1 cells were treated with 15d-PGJ₂ (9,8 μM) for 0 to 24 h. (a) shows the relative IL-6 expression. (b) Quantitative IL-6 released by TPC-1 cells treated with 15d-PGJ₂ against the control group. The data are presented as means ± standard deviation of three replicates from at least three independent tests. An asterisk  ^∗ indicates statistically significant difference from the control group (^∗ P > 0.01; ^∗∗∗ P > 0.001).

Figure 5

SOCS3 and SOCS1 increased in TPC-1 cells treated with 15d-PGJ₂. TPC-1 cells were treated with 15d-PGJ₂ (9,8 μM) for 0 to 24 h. (a) shows the relative expression of SOCS3 (b), SOCS1 (c), and STAT3 (c) in the first two hours of treatment and decreased STAT3 four hours after the treatment (c). The date are presented as means ± standard deviation of three replicates from at least three independent tests. An asterisk  ^∗ indicates statistically significant difference from the control (^∗ P > 0.01; ^∗∗∗ P > 0.001).