A TCM formula assists temozolomide in anti-melanoma therapy by suppressing the STAT3 signaling pathway

Ethnopharmacological relevance

Temozolomide (TMZ) is a first-line therapeutic medication for melanoma. Nonetheless, it exhibits a relatively elevated toxicity profile, and falls short in terms of both effectiveness and median survival rate. Clinical research has demonstrated that the integration of traditional Chinese medicine (TCM) with chemotherapy in the treatment of melanoma can enhance efficacy and reduce toxicity. A TCM formula (SLE) containing Lonicera japonica Thunb. and Robinia pseudoacacia L. has shown anti-melanoma properties through the inhibition of STAT3 phosphorylation. In the genesis and advancement of melanoma, the STAT3 signaling pathway is essential.

Aim of the study

The aim of this study was to evaluate the effect of SLE combined with TMZ (SLE/TMZ) in inhibiting melanoma, and to explore the contribution of inhibiting the STAT3 signaling pathway in this effect.

Materials and methods

Both A375 cells and B16F10 tumor-bearing mice were used for in vitro and in vivo experiments, respectively. In vitro assays included CCK8, crystal violet staining, flow cytometry, qRT-PCR, and Western blotting. Animal experiment indicators included tumor volume, tumor weight, mouse weight, and the proportion of mouse immune cells.

Results

SLE/TMZ inhibited the proliferation and growth of A375 cells, and also induced apoptosis. Additionally, SLE/TMZ synergistically inhibited tumor growth in the B16F10 melanoma mouse model and had immunomodulatory effects, increasing the proportion of Th, Tc, and NK cells and decreasing the proportion of MDSCs in the spleen of melanoma-bearing mice. qRT-PCR and Western blotting results confirmed that SLE/TMZ inhibited STAT3 phosphorylation and regulated its downstream factors, including Bcl2, Mcl1, CCND1, MYC, MMP2, MMP9, VEGFA, and FGF2. The inhibitory effect of SLE/TMZ on melanoma cell growth was considerably lessened when STAT3 was overexpressed at the cellular level.

Conclusion

Synergistic anti-melanoma effects of SLE/TMZ have been observed in animal and cellular models. One of the mechanisms of SLE/TMZ that underlies its anti-melanoma actions is inhibition of the STAT3 pathway. This work offers pre-clinical pharmacological backing for the advancement of SLE as a therapeutic agent to be used in conjunction with TMZ for the treatment of melanoma.