Si-Jun-Zi-Tang combined with temozolomide produces synergistic anti-melanoma effects via inhibiting MGMT and ATR/CHK1 pathways

Sze-Man Amy Li, Xiu-Qiong Fu, Xiao-Qi Wang, Jing-Xuan Bai, Ying-Jie Chen, Ying Wu, Jia-Ying Wu, Lut-Yi Wong, Xiao-Yun Fan, Rui-Xuan Han, Li Wang, Zhi-Ling Yu

Research output: Contribution to conferenceConference abstractpeer-review


Introduction: Malignant melanoma is one of the deadliest cancers in the world.
Temozolomide (TMZ) is a commonly used therapeutic drug in treating melanoma.
However, it has severe toxicities. Si-Jun-Zi-Tang (SJZT) is a traditional Chinese
medicine formula which tonifies “Qi” in human body. When combined with chemotherapeutic drugs, SJZT can enhance their efficacy. Whether SJZT enhances
TMZ’s anti-melanoma effects is a question to be answered. In this study, we investigated the anti-melanoma effects and mechanisms of SJZT in combination with TMZ (SJZT-plus-TMZ).

Methods and results: SJZT extract was prepared by reflux-extraction using 95%
ethanol. CCK8 assays showed that SJZT synergizes the cytotoxicity of TMZ in A375
and A2058 melanoma cells, and SJZT-plus-TMZ exerts less cytotoxicity in normal
HaCaT keratinocyte cells than in melanoma cells. Comet assays demonstrated that
SJZT enhances TMZ’ effects in inducing DNA damage. In a B16 melanoma-bearing
mouse model, SJZT synergizes TMZ in inhibiting melanoma growth. Additionally, we found that SJZT reduces hepatotoxicity of TMZ, indicated by lowered serum levels of ALT and AST. Network pharmacology predicted that MGMT and Chk1 are the key proteins responsible for the synergistic anti-melanoma effects of SJZT-plus-TMZ. It was reported that inhibition of MGMT or ATR/Chk1 signaling sensitizes melanoma cells to TMZ. Immunoblotting demonstrated that SJZT-plus-TMZ lowers protein levels of MGMT, phospho-ATR (Ser428), total Chk1, phospho-Chk1 (Ser296, Ser317, Ser345) and phospho-cdc25c (Ser216) in A375 cells. RT-qPCR revealed that SJZT-plus-TMZ lowers the mRNA level of Chk1 but not MGMT. Immunoblotting showed that SJZT-plus-TMZ accelerates MGMT proteasomal degradation.

Conclusions: Our results indicate that SJZT synergizes the anti-melanoma effects and lowers hepatotoxicity of TMZ; and inhibition of the ATR/Chk1 pathway and
acceleration of proteasomal degradation of MGMT are involved in the synergistic
effects of the combination. Findings of this study suggest that SJZT-plus-TMZ can be developed into a highly effective anti-melanoma agent with low toxicity.
Original languageEnglish
Number of pages2
Publication statusPublished - 30 Oct 2022
EventThe Global Conference on Evidence-based Traditional Medicine, GCETM 2022 - Virtual, Penang, Malaysia
Duration: 29 Oct 202230 Oct 2022


ConferenceThe Global Conference on Evidence-based Traditional Medicine, GCETM 2022
Internet address

User-Defined Keywords

  • Si-Jun-Zi-Tang
  • temozolomide
  • melanoma
  • MGMT
  • ATR/Chk1 signaling


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