healthmedicinet

Research article

Marjolaine Ngollo, Andre Lebert, Aslihan Dagdemir, Gaelle Judes, Seher Karsli-Ceppioglu, Marine Daures, Jean Louis Kemeny, Frederique Penault-Llorca, Jean Paul Boiteux, Yves Jean Bignon, Laurent Guy and Dominique Bernard-Gallon

Abstract (provisional)

Background

It is well established that genetic and epigenetic alterations are common events in
prostate cancer, which may lead to aberrant expression of critical genes. The importance
of epigenetic mechanisms in prostate cancer carcinogenesis is increasingly evident.
In this study, the focus will be on histone modifications and the primary objectives
are to map H3K27me3 marks and quantify RAR beta 2, ER alpha, SRC3, RGMA, PGR, and
EZH2 gene expressions in prostate cancer tissues compared to normal tissues. In addition,
a data analysis was made in connection with the clinicopathological parameters.

Patients and methods: 71 normal specimens and 66 cancer prostate tissues were randomly
selected in order to assess the proportion of the repressive H3K27me3 chromatin marks
and gene expression. H3K27me3 level was evaluated by ChIP-qPCR and mRNA expression
using RT-qPCR between prostate cancer and normal tissues. Subsequently, western-blotting
was performed for protein detection. The analysis of variance (ANOVA) was performed,
and Tukey’s test was used to correct for multiple comparisons (p-value threshold of
0.05). The principal component analysis (PCA) and discriminant factorial analysis
(DFA) were used to explore association between H3K27me3 level and clinicopathological
parameters.

Results

The study demonstrated that H3K27me3 level was significantly enriched at RAR beta
2, ER alpha, PGR, and RGMA promoter regions in prostate cancer tissues compared to
normal tissues. After stratification by clinicopathological parameters, the H3K27me3
level was positively correlated with Gleason score, PSA levels and clinical stages
for RAR beta 2, ER alpha, PGR, and RGMA. High H3K27me3 mark was significantly associated
with decreased RAR beta 2, ER alpha, PGR and RGMA gene expressions in prostate cancer
sample compared to the normal one. Moreover, the results showed that mRNA level of
EZH2, AR and SRC3 are upregulated in prostate cancer compared to normal prostate tissues
and this correlates positively with Gleason score, PSA levels and clinical stages.
Obviously, these observations were confirmed by protein level using western-blot.

Conclusions

This data clearly demonstrated that H3K27me3 level correlated with aggressive tumor
features. Also this study revealed that reverse correlation of RAR beta 2, ER alpha,
PGR, and RGMA expressions with EZH2, SRC3, and AR expressions in prostate cancer tissues
suggests that these genes are the target of EZH2. Therefore, all therapeutic strategies
leading to histone demethylation with epigenetic drugs such as histone methyltransferase
inhibitor may be relevant treatments against prostate cancer.