Small-Molecule Natural Product Physachenolide C Potentiates Immunotherapy Efficacy by Targeting BET Proteins.

Abstract

Screening for sensitizers of cancer cells to TRAIL-mediated apoptosis identified a natural product of the 17β-hydroxywithanolide (17-BHW) class, physachenolide C (PCC), as a promising hit. In this study, we show that PCC was also able to sensitize melanoma and renal carcinoma cells to apoptosis in response not only to TRAIL, but also to the synthetic polynucleotide poly I:C, a viral mimetic and immune activator, by reducing levels of antiapoptotic proteins cFLIP and Livin. Both death receptor and TLR3 signaling elicited subsequent increased assembly of a proapoptotic ripoptosome signaling complex. Administration of a combination of PCC and poly I:C in human M14 melanoma xenograft and a syngeneic B16 melanoma model provided significant therapeutic benefit as compared with individual agents. In addition, PCC enhanced melanoma cell death in response to activated human T cells in vitro and in vivo in a death ligand-dependent manner. Biochemical mechanism-of-action studies established bromo and extraterminal domain (BET) proteins as major cellular targets of PCC. Thus, by targeting of BET proteins to reduce antiapoptotic proteins and enhance caspase-8-dependent apoptosis of cancer cells, PCC represents a unique agent that can potentially be used in combination with various immunotherapeutic approaches to promote tumor regression and improve outcome. SIGNIFICANCE: These findings demonstrate that PCC selectively sensitizes cancer cells to immune-mediated cell death, potentially improving the efficacy of cancer immunotherapies. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/12/3374/F1.large.jpg.

• Authors: Poonam Tewary, Alan D Brooks, Ya-Ming Xu, E M Kithsiri Wijeratne, Ashley L Babyak, Timothy C Back, Raj Chari, Christine N Evans, Curtis J Henrich, Thomas J Meyer, Elijah F Edmondson, Maria T Prudente de Aquino, Thanigaivelan Kanagasabai, Anil Shanker, A A Leslie Gunatilaka, Thomas J Sayers
• Journal: Cancer research (Cancer Res) Vol. 81 Issue 12 Pg. 3374-3386 (06 15 2021) ISSN: 1538-7445 [Electronic] United States
• PMID: 33837043 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, N.I.H., Intramural, Research Support, Non-U.S. Gov't)
• Copyright: ©2021 American Association for Cancer Research.

Chemical References

• Antineoplastic Agents, Phytogenic
• BRD4 protein, human
• Biological Products
• Cell Cycle Proteins
• Interferon Inducers
• Transcription Factors
• Withanolides
• physachenolide C
• Poly I-C

Topics

• Animals
• Antineoplastic Agents, Phytogenic (pharmacology)
• Apoptosis
• Biological Products (pharmacology)
• Carcinoma, Renal Cell (drug therapy, immunology, pathology)
• Cell Cycle Proteins (antagonists & inhibitors)
• Cell Proliferation
• Drug Therapy, Combination
• Female
• Humans
• Immunotherapy (methods)
• Interferon Inducers (pharmacology)
• Kidney Neoplasms (drug therapy, immunology, pathology)
• Male
• Melanoma, Experimental (drug therapy, immunology, pathology)
• Mice
• Mice, Inbred BALB C
• Mice, Nude
• Poly I-C (pharmacology)
• Transcription Factors (antagonists & inhibitors)
• Tumor Cells, Cultured
• Withanolides (pharmacology)
• Xenograft Model Antitumor Assays