Prostate cancer-associated SPOP mutations confer resistance to BET inhibitors through stabilization of BRD4.

Abstract

The bromodomain and extraterminal (BET) family of proteins comprises four members-BRD2, BRD3, BRD4 and the testis-specific isoform BRDT-that largely function as transcriptional coactivators and play critical roles in various cellular processes, including the cell cycle, apoptosis, migration and invasion. BET proteins enhance the oncogenic functions of major cancer drivers by elevating the expression of these drivers, such as c-Myc in leukemia, or by promoting the transcriptional activities of oncogenic factors, such as AR and ERG in prostate cancer. Pathologically, BET proteins are frequently overexpressed and are clinically linked to various types of human cancer; they are therefore being pursued as attractive therapeutic targets for selective inhibition in patients with cancer. To this end, a number of bromodomain inhibitors, including JQ1 and I-BET, have been developed and have shown promising outcomes in early clinical trials. Although resistance to BET inhibitors has been documented in preclinical models, the molecular mechanisms underlying acquired resistance are largely unknown. Here we report that cullin-3SPOP earmarks BET proteins, including BRD2, BRD3 and BRD4, for ubiquitination-mediated degradation. Pathologically, prostate cancer-associated SPOP mutants fail to interact with and promote the degradation of BET proteins, leading to their elevated abundance in SPOP-mutant prostate cancer. As a result, prostate cancer cell lines and organoids derived from individuals harboring SPOP mutations are more resistant to BET-inhibitor-induced cell growth arrest and apoptosis. Therefore, our results elucidate the tumor-suppressor role of SPOP in prostate cancer in which it acts as a negative regulator of BET protein stability and also provide a molecular mechanism for resistance to BET inhibitors in individuals with prostate cancer bearing SPOP mutations.

• Authors: Xiangpeng Dai, Wenjian Gan, Xiaoning Li, Shangqian Wang, Wei Zhang, Ling Huang, Shengwu Liu, Qing Zhong, Jianping Guo, Jinfang Zhang, Ting Chen, Kouhei Shimizu, Francisco Beca, Mirjam Blattner, Divya Vasudevan, Dennis L Buckley, Jun Qi, Lorenz Buser, Pengda Liu, Hiroyuki Inuzuka, Andrew H Beck, Liewei Wang, Peter J Wild, Levi A Garraway, Mark A Rubin, Christopher E Barbieri, Kwok-Kin Wong, Senthil K Muthuswamy, Jiaoti Huang, Yu Chen, James E Bradner, Wenyi Wei
• Journal: Nature medicine (Nat Med) Vol. 23 Issue 9 Pg. 1063-1071 (Sep 2017) ISSN: 1546-170X [Electronic] United States
• PMID: 28805820 (Publication Type: Journal Article)

Chemical References

• (+)-JQ1 compound
• Azepines
• BRD2 protein, human
• BRD3 protein, human
• BRD4 protein, human
• BRDT protein, human
• CUL3 protein, human
• Cell Cycle Proteins
• Cullin Proteins
• Nuclear Proteins
• RNA-Binding Proteins
• Repressor Proteins
• SPOP protein, human
• Transcription Factors
• Triazoles
• dBET1 compound
• Benzodiazepines
• Thalidomide
• molibresib
• Protein Serine-Threonine Kinases

Topics

• Apoptosis
• Azepines
• Benzodiazepines
• Cell Cycle Proteins
• Cell Proliferation
• Cullin Proteins
• Drug Resistance, Neoplasm (genetics)
• HEK293 Cells
• HeLa Cells
• Humans
• Immunoblotting
• Immunoprecipitation
• Male
• Molecular Targeted Therapy
• Nuclear Proteins (genetics, metabolism)
• Prostatic Neoplasms (drug therapy, genetics, metabolism)
• Protein Serine-Threonine Kinases
• RNA-Binding Proteins
• Repressor Proteins (genetics)
• Thalidomide (analogs & derivatives)
• Transcription Factors (metabolism)
• Triazoles
• Ubiquitination