Acetylated HOXB13 Regulated Super Enhancer Genes Define Therapeutic Vulnerabilities of Castration-Resistant Prostate Cancer

Abstract

Purpose: Androgen receptor (AR) antagonism is exacerbated by HOXB13 in castration-resistant prostate cancers (CRPC). However, it is unclear when and how HOXB13 primes CRPCs for AR antagonism. By mass-spectrometry analysis of CRPC extract, we uncovered a novel lysine 13 (K13) acetylation in HOXB13 mediated by CBP/p300. To determine whether acetylated K13-HOXB13 is a clinical biomarker of CRPC development, we characterized its role in prostate cancer biology. Experimental Design: We identified tumor-specific acK13-HOXB13 signal enriched super enhancer (SE)-regulated targets. We analyzed the effect of loss of HOXB13K13-acetylation on chromatin binding, SE proximal target gene expression, self-renewal, enzalutamide sensitivity, and CRPC tumor growth by employing isogenic parental and HOXB13K13A mutants. Finally, using primary human prostate organoids, we evaluated whether inhibiting an acK13-HOXB13 target, ACK1, with a selective inhibitor (R)-9b is superior to AR antagonists in inhibiting CRPC growth. Results: acK13-HOXB13 promotes increased expression of lineage (AR, HOXB13), prostate cancer diagnostic (FOLH1), CRPC-promoting (ACK1), and angiogenesis (VEGFA, Angiopoietins) genes early in prostate cancer development by establishing tumor-specific SEs. acK13-HOXB13 recruitment to key SE-regulated targets is insensitive to enzalutamide. ACK1 expression is significantly reduced in the loss of function HOXB13K13A mutant CRPCs. Consequently, HOXB13K13A mutants display reduced self-renewal, increased sensitivity to enzalutamide, and impaired xenograft tumor growth. Primary human prostate tumor organoids expressing HOXB13 are significantly resistant to AR antagonists but sensitive to (R)-9b. Conclusions: In summary, acetylated HOXB13 is a biomarker of clinically significant prostate cancer. Importantly, PSMA-targeting agents and (R)-9b could be new therapeutic modalities to target HOXB13–ACK1 axis regulated prostate cancers.

Genetic variant in a BaP-activated super-enhancer increases prostate cancer risk by promoting AhR-mediated <i>FAM227A</i> expression

“…For example, rs539846 located in a SE affects chronic lymphocytic leukemia susceptibility through differential binding to RELA (NF-kappa-B subunit) and direct modulation of BMF expression, impacting the antiapoptotic protein B cell lymphoma 2 (BCL2) [ 9 ] . Moreover, many discoveries have been made regarding the effect of SEs on prostate cancer [ 21 – 22 ] . For instance, the acetylated homeobox B13 (HOXB13) plays a role in controlling ACK1 gene transcription in prostate cancer by establishing a CRPC-specific SE, thereby affecting tumor growth [ 22 ] .…”

“…Moreover, many discoveries have been made regarding the effect of SEs on prostate cancer [ 21 – 22 ] . For instance, the acetylated homeobox B13 (HOXB13) plays a role in controlling ACK1 gene transcription in prostate cancer by establishing a CRPC-specific SE, thereby affecting tumor growth [ 22 ] . In our current study, 22q-SE influenced prostate cancer susceptibility by altering the binding affinity of AhR and regulating the FAM227A expression.…”

Super-Enhancers and Their Parts: From Prediction Efforts to Pathognomonic Status

“…It has been demonstrated that increased expression of ACK1, one of the most remarkable SE-associated genes, overrides the loss of androgen stimulation, and human prostate tumour organoids expressing HOXB13 showed significant resistance to AR antagonists but were sensitive to (R)-9b, an ACK1 selective inhibitor [ 180 ].…”

“… ACK1 is a crucial regulator of CRPC growth, oncogene. FOLH1 is a ProCa diagnostic gene HOXB13 (acK13-HOXB1) HOXB13 acetylated by p300/CBP at lysine 13 (acK13-HOXB1) establishes tumour-specific SEs, and the following factors are likely to contribute to this: (1) acK13-HOXB significantly better binds chromatin remodelling proteins, bromodomain-containing proteins, and CTCF compared to unmodified HOXB13; (2) BRD9 specifically interacts only with acK13-HOXB13, not with HOXB13; (3) acK13-HOXB13 binding motif at SE region differs from unmodified protein Tumourigenesis (R)-9b, ACK1 inhibitor (shown on the prostate organoids) [ 180 ] Bladder cancer — UM-UC-3, T24 cells — LINC00162 LINC00162 is an SE lncRNA, located on 21q22.3. It is encoded by sequence overlapping with SE and is found to be significantly upregulated with the highest fold change in bladder cancer cell line compared to normal cell line in the SE lncRNA microarray expression analysis.…”

Symptomatic Benign Prostatic Hyperplasia with Suppressed Epigenetic Regulator HOXB13 Shows a Lower Incidence of Prostate Cancer Development

“…In contrast, dysregulated HOXB13 expression promotes androgen receptor-independent function and cancer cell proliferation [ 8 ]. Moreover, in cancer cells, HOXB13 promotes increased expression of AR and NKX3-1 through its central role in recruiting SWI/SNF chromatin remodelers to their cognate super-enhancers [ 9 ]. Conversely, targeting HOXB13-regulated transcriptional networks with bromodomain kinase inhibitors has shown therapeutic efficacy in castration-resistant prostate cancer models [ 8 ].…”