Tasmanian School of Medicine, College of Health and Medicine, University of Tasmania, Hobart, Tasmania, Australia, 7000; Menzies Institute for Medical Research, College of Health and Medicine, University of Tasmania, Hobart, Tasmania, Australia, 7000.
Tasmanian School of Medicine, College of Health and Medicine, University of Tasmania, Hobart, Tasmania, Australia, 7000.
Exp Cell Res. 2020 Jul 15;392(2):112055. doi: 10.1016/j.yexcr.2020.112055. Epub 2020 May 4.
Examination of epigenetic changes at the ITGB4 gene promoter reveals altered methylation at different stages of prostate tumour progression and these changes may, in part, explain the complex patterns of gene expression of this integrin observed. Transcriptional re-programming perturbs expression of cell adhesion molecules and underpins metastatic tumour cell behaviour. Decreasing expression of the cell adhesion molecule ITGB4, which encodes the beta subunit of the integrin, alpha6 beta4 (α6β4), has been correlated with increased tumour aggressiveness and metastasis in multiple tumour types including prostate cancer. Paradoxically, in vitro studies in tumour cell models demonstrate that ITGB4 mediates cell mobility and invasion. Herein we examined whether transcriptional re-programming by methylation influenced ITGB4 gene expression at different stages of prostate cancer progression. Bisulphite sequencing of a large CpG island in the ITGB4 gene promoter identified differentially methylated regions in prostate cancer cell lines representing a localised tumour (22Rv1), lymph node metastasis (LNCaP), and a bone metastasis (PC-3). The highest levels of methylation were observed in the CpG island surrounding the ITGB4 transcription start site in PC-3 cells, and this observation also correlated with higher gene expression of ITGB4 in these cells. Furthermore, PC-3 cells expressed two distinct transcripts, using an alternate transcription start site, which was not detected in other cell lines. In prostate tumour biopsy samples, patterns of methylation across the ITGB4 promoter were similar overall in matched primary and metastatic samples (n = 4 pairs), with a trend toward loss of methylation at specific sites in metastatic lesions.
检查 ITGB4 基因启动子上的表观遗传变化，揭示了前列腺肿瘤进展不同阶段的甲基化改变，这些变化可能部分解释了观察到的这种整合素基因表达的复杂模式。转录重编程扰乱了细胞黏附分子的表达，并为肿瘤转移细胞的行为提供了基础。细胞黏附分子 ITGB4 的表达减少，该基因编码整合素的β亚基 α6β4（α6β4），与多种肿瘤类型包括前列腺癌的肿瘤侵袭性和转移增加有关。矛盾的是，在肿瘤细胞模型的体外研究表明，ITGB4 介导细胞迁移和侵袭。在此，我们研究了甲基化是否通过转录重编程影响了前列腺癌进展不同阶段的 ITGB4 基因表达。用亚硫酸氢盐测序法对 ITGB4 基因启动子中的一个大 CpG 岛进行测序，鉴定出了在代表局限性肿瘤（22Rv1）、淋巴结转移（LNCaP）和骨转移（PC-3）的前列腺癌细胞系中存在差异甲基化区域。在 PC-3 细胞中，围绕 ITGB4 转录起始位点的 CpG 岛上观察到最高水平的甲基化，这一观察结果也与这些细胞中 ITGB4 的高基因表达相关。此外，PC-3 细胞使用一个替代的转录起始位点表达了两种不同的转录本，而在其他细胞系中则未检测到。在前列腺肿瘤活检样本中，ITGB4 启动子上的甲基化模式在匹配的原发和转移性样本中总体上相似（n=4 对），在转移性病变中存在特定位点甲基化丢失的趋势。
