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Dexamethasone and OLT1177 Cooperate in the Reduction of Melanoma Growth by Inhibiting STAT3 Functions
Alberto Dinarello1, Taylor S Mills1, Isak W Tengesdal1,2
1Department of Medicine, University of Colorado, Aurora, Denver, CO 80045, USA.
Abstract:
The NLRP3 inflammasome is a multimolecular complex that processes inactive IL-1β and IL-18 into proinflammatory cytokines. OLT1177 is an orally active small compound that specifically inhibits NLRP3. Here, B16F10 melanoma were implanted in mice and treated with OLT1177 as well as combined with the glucocorticoid dexamethasone. At sacrifice, OLT1177 treated mice had significantly smaller tumors compared to tumor-bearing mice treated with vehicle. However, the combined treatment of OLT1177 plus dexamethasone revealed a greater suppression of tumor growth. This reduction was accompanied by a downregulation of nuclear and mitochondrial STAT3-dependent gene transcription and by a significant reduction of STAT3 Y705 and S727 phosphorylations in the tumors. In vitro, the human melanoma cell line 1205Lu, stimulated with IL-1α, exhibited significantly lower levels of STAT3 Y705 phosphorylation by the combination treatment, thus affecting the nuclear functions of STAT3. In the same cells, STAT3 serine 727 phosphorylation was also lower, affecting the mitochondrial functions of STAT3. In addition, metabolic analyses revealed a marked reduction of ATP production rate and glycolytic reserve in cells treated with the combination of OLT1177 plus dexamethasone. These findings demonstrate that the combination of OLT1177 and dexamethasone reduces tumor growth by targeting nuclear as well as mitochondrial functions of STAT3.
Insights
The NLRP3 inflammasome inhibitor OLT1177 combined with dexamethasone effectively suppressed melanoma tumor growth. This combination therapy targets both nuclear and mitochondrial STAT3 functions, reducing tumor progression.
Area of Science:
- Immunology
- Oncology
- Pharmacology
Background:
- The NLRP3 inflammasome activates pro-inflammatory cytokines IL-1β and IL-18.
- OLT1177 is an orally available small molecule inhibitor of NLRP3.
- Melanoma progression involves complex inflammatory and signaling pathways.
Purpose of the Study:
- To investigate the anti-tumor efficacy of OLT1177 alone and in combination with dexamethasone in melanoma.
- To elucidate the underlying molecular mechanisms, focusing on STAT3 signaling and cellular metabolism.
Main Methods:
- B16F10 melanoma mouse model and 1205Lu human melanoma cell line were used.
- Tumor growth was measured after treatment with OLT1177, dexamethasone, or combination therapy.
- STAT3 phosphorylation (Y705 and S727) and gene transcription were analyzed.
- In vitro metabolic analyses (ATP production, glycolytic reserve) were performed.
Main Results:
- Combined OLT1177 and dexamethasone significantly reduced tumor growth compared to OLT1177 alone.
- The combination therapy downregulated STAT3-dependent gene transcription and reduced STAT3 phosphorylation at Y705 and S727.
- In vitro studies showed decreased STAT3 phosphorylation and impaired cellular metabolism (ATP production, glycolytic reserve) with combination treatment.
Conclusions:
- Combination therapy of OLT1177 and dexamethasone demonstrates enhanced suppression of melanoma tumor growth.
- This synergistic effect is mediated by targeting both nuclear and mitochondrial functions of STAT3.
- The findings highlight a potential therapeutic strategy for melanoma by combining NLRP3 inhibition with dexamethasone.
