PgmNr M300: The aggressive prostate cancer susceptibility gene HIST1H1A is a modulator of androgen receptor signaling and epithelial to mesenchymal transition.

Authors:
K. Williams 1 ; M. Lee 1 ; Y. Hu 2 ; J. Andreas 1 ; S. Zhang 1 ; N. Crawford 1


Institutes
1) NHGRI/NIH, Bethesda, MD; 2) NCI/NIH, Rockville, MD.


Abstract:

In 2016, approximately 190,000 new prostate cancer (PC) cases will be diagnosed, and over 26,000 men will succumb to PC. Presently, there is an urgent need to more precisely identify men at risk for aggressive PC. This study aims to characterize how germline variation modulates susceptibility to ‘neuroendocrine (NE) differentiation’, which is a marker of aggressive PC. Our earlier study identified aggressive PC susceptibility genes using the C57BL/6-Tg(TRAMP)8247Ng/J (TRAMP) mouse model of NE PC. We performed quantitative trait locus (QTL) mapping in transgene-positive (TRAMPxNOD/ShiLtJ) F2 intercross males (n=228), and expression QTL mapping using primary tumor microarray data (n=126) identified 35 aggressive PC candidate genes. Furthermore, in silico analysis identified HIST1H1A, which encodes the linker histone H1.1, as having an expression level associated with patient outcome in a human PC gene expression dataset, and harboring a SNP associated with lymph node metastasis in the PC genome-wide association study. Ectopic expression of HIST1H1A in the aggressive, androgen receptor (AR)-negative human prostate PC3-Luc cell line suppressed tumor growth in a xenograft flank assay (avg. tumor vol. = 311+/-69 mm3 vs. 565+/-193 mm3 for controls; P=1.01x10-4), and reduced dissemination in a systemic metastasis assay (avg. flux=4.45x108 vs. 1.01x109 for controls; P=0.035). Conversely, in the AR-positive LNCaP cell line, ectopic expression of HIST1H1A enhanced tumor growth.  Microarray analysis of the latter cell lines revealed that over 2,600 transcripts were significantly dysregulated in response to HIST1H1A over-expression (fold change +/- 1.5, false discovery rate < 0.05). Ingenuity Pathway Analysis revealed that both AR signaling and epithelial to mesenchymal transition (EMT) were significantly impacted.  Quantitative RT-PCR indicated that higher HIST1H1A levels were associated with suppression of epithelial gene expression (e.g., KRT18, TJP1) and activation of mesenchymal genes (e.g., SNAI2, VIM).  Immunoblot analysis revealed suppression of long-form AR expression and activation of the aggressive disease associated AR-V7 splice variant. Collectively, these data indicate that HIST1H1A affects aggressive PC by modulating AR signaling and EMT.  Ongoing work involves ATAC-seq analysis to determine how HIST1H1A dysregulation impacts PC-specific chromatin structure, as well as CRISPR/Cas9 knockout of Hist1h1a in mice.  These data demonstrate the use of systems genetics to provide insights into how hereditary variation influences aggressive PC susceptibility.