ADT-OH, a Hydrogen Sulfide-Releasing Donor, Induces Apoptosis of Melanoma Cells and Inhibits Melanoma Development In Vivo

Background: Melanoma is one of the most lethal malignancies. The lack of apoptosis in cancer cells usually leads to therapeutic resistance to melanoma. Hydrogen sulfide (H2S) is now widely recognized as the third endogenous gasotransmitter, playing critical roles in cancer biological processes especially in inducing apoptosis in cancer cells. Thereafter, the aim of this study was to evaluate the effect of the combination of H2S-donor ADT-OH with other proapoptotic agent in treatment of melanoma.   Methods: The killing effect and the underlying mechanism of ADT-OH on wild-type and FADD knockout melanoma cell lines were evaluated by CCK8, apoptosis and immunofluorescence analyses. Tumor xenograft growth, tumor tissue HE and immunofluorescence analyses were measured in vivo.   Findings: ADT-OH inhibited IκBα degradation, resulting in reduced NF-κB activation. More importantly, ADT-OH could suppress the ubiquitin degradation of FADD and increase its protein level in five different types of cancer cell lines through downregulating MKRN1 expression, an E3 ubiquitin ligase of FADD. Additionally, ADT-OH had no significant therapeutic effect on FADD knockout melanoma cells. However, tumor-specific delivery of FADD through a recombinant Salmonella strain VNP-FADD combined with ADT-OH at a low dosage inhibited tumor growth and induced cancer cell apoptosis significantly by using a mouse xenograft model.   Interpretation: ADT-OH might be a promising cancer therapeutic drug that warrants further investigation into its potential clinical applications.   Funding Statement: Chinese National Natural Sciences Foundation (81773099, 81570790), the National Key Research Program by Ministry of Science and Technology (2014CB744501), the National Key R&D Program of China (2017YFA0506000). Declaration of Interests: The authors declare no potential conflicts of interest. Ethics Approval Statement: Animal care and use were performed strictly in accordance with the ethical guidelines by the Nanjing University Animal Care and Use Committee, and the study protocol was approved by the local institution review board.