Two small molecule compounds, LLL12 and FLLL32, exhibit potent inhibitory activity on STAT3 in human rhabdomyosarcoma cells
Chang-Ching Wei1, Sarah Ball, Li Lin
1Department of Pediatrics, China Medical University Hospital, Taichung, Taiwan, R.O.C. longus@seed.net.tw
Abstract:
Signal transducers and activators of transcription 3 (STAT3) signaling is persistently activated in many types of cancer cells, and represents a valid target for anticancer drug design. However, few reports have described the constitutive activation of STAT3 in human sarcoma cells. In this study, we demonstrate that the STAT3 signaling pathway is constitutively activated in human rhabodomyosarcoma cells (RH28, RH30, and RD2). We also investigated the inhibitory effects of two newly developed small molecules, LLL12 and FLLL32, on the STAT3 signaling pathway in human rhabodomyosarcoma cells. Both LLL12 and FLLL32 downregulated STAT3 constitutively and interleukin-6 (IL-6) stimulated phosphorylated STAT3 (p-STAT3). The inhibition of STAT3 via LLL12 and FLLL32 was confirmed by the inhibition of STAT3 DNA binding activity. The downstream targets of STAT3, cyclin D1, Bcl-xL, and survivin were also downregulated by LLL12 and FLLL 32 at both messenger RNA and protein levels. The potency of LLL12 and FLLL32 to inhibit proliferation/viability in human rhabodomyosarcoma cells (RH28, RH30, and RD2) was higher than that of the 5 previously reported Janus kinase 2 (JAK2)/STAT3 inhibitors (LLL3, WP1066, Stattic, S3I-201, and AG490) and curcumin. Thus, in this study, we investigated the inhibitory effects of two STAT3 inhibitors, LLL12 and FLLL32, on the STAT3 signaling pathway in human rhabodomyosarcoma cells; we also demonstrated their higher potency in inhibiting proliferation on human rhabodomyosarcoma cells as compared to other five JAK2/STAT3 inhibitors and curcumin.
Insights
Signal transducer and activator of transcription 3 (STAT3) is activated in rhabdomyosarcoma. New small molecules LLL12 and FLLL32 inhibit STAT3 signaling and show greater potency against cancer cell proliferation than existing drugs.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Signal transducer and activator of transcription 3 (STAT3) signaling is frequently activated in various cancers, making it a potential therapeutic target.
- Constitutive STAT3 activation is not well-documented in human sarcoma, particularly rhabdomyosarcoma.
Purpose of the Study:
- To investigate the constitutive activation of STAT3 in human rhabdomyosarcoma cells.
- To evaluate the inhibitory effects of novel small molecules, LLL12 and FLLL32, on the STAT3 pathway in these cells.
- To compare the efficacy of LLL12 and FLLL32 against other known STAT3 inhibitors and curcumin in rhabdomyosarcoma models.
Main Methods:
- Assessed STAT3 signaling pathway activation in human rhabdomyosarcoma cell lines (RH28, RH30, RD2).
- Treated cells with LLL12 and FLLL32 to measure downregulation of phosphorylated STAT3 (p-STAT3) and STAT3 DNA binding activity.
- Quantified messenger RNA and protein levels of STAT3 downstream targets, including cyclin D1, Bcl-xL, and survivin.
- Compared the antiproliferative and cell viability effects of LLL12 and FLLL32 with existing JAK2/STAT3 inhibitors and curcumin.
Main Results:
- STAT3 signaling was found to be constitutively activated in human rhabdomyosarcoma cells.
- LLL12 and FLLL32 effectively downregulated both basal and interleukin-6 (IL-6) stimulated p-STAT3 levels.
- Inhibition of STAT3 DNA binding activity was confirmed for LLL12 and FLLL32.
- Downregulation of STAT3 downstream targets (cyclin D1, Bcl-xL, survivin) at mRNA and protein levels was observed.
- LLL12 and FLLL32 demonstrated superior potency in inhibiting proliferation and viability compared to five other JAK2/STAT3 inhibitors and curcumin.
Conclusions:
- The STAT3 signaling pathway is constitutively active in human rhabdomyosarcoma.
- LLL12 and FLLL32 are potent inhibitors of STAT3 signaling in rhabdomyosarcoma cells.
- These novel compounds exhibit greater efficacy in inhibiting rhabdomyosarcoma cell proliferation than currently available agents, suggesting therapeutic potential.
