Prevalence of CD24 epigenetic silencing in breast tumors and ERalpha status

描述(申请人提供)：1.摘要三分之二的乳腺癌表达雌激素受体α(ER1)，并依赖ER1信号促进其生长。雌激素剥夺是治疗ER1阳性乳腺癌的有效方法。然而，内分泌治疗的内在和获得性抵抗仍然是ER1阳性肿瘤复发和死亡的重要原因。ER1下游靶基因的表观遗传沉默最近被认为是内分泌治疗抵抗的关键因素。例如，最近的几个发现证实了像HOXB13这样的ER1靶基因的表观遗传沉默的临床和治疗意义。CD24作为一种潜在的乳腺癌干细胞(BCSC)标记物，因其在乳腺癌的发生、转移过程中的负性作用而在乳腺癌研究中受到广泛关注。虽然CD24在原发肿瘤中有表达，但研究表明，CD24阴性细胞具有高度的致瘤性，其在阴性乳腺癌细胞中的过度表达会导致转移潜能的丧失。这表明CD24表达的丧失可能是获得转移潜能的关键。有趣的是，具有CD44阳性的CD24低/缺失标记组合(ESA？/LOW)的上皮细胞被认为是BCSCs。我们以前发表过，BCSCs在原发肿瘤中的高流行率有利于远处转移。同样，人乳腺上皮细胞的上皮间充质转化(EMT)导致CD24阴性表型，具有丰富的致瘤和转移潜能。我们先前发表的文章表明，雌激素抑制CD24的转录，ER1与CD24启动子中的回文ERE结合。最近的一项对17项独立乳腺癌研究的肿瘤学分析表明，ER1阳性和CD24表达之间存在强烈的负相关。这表明CD24的差异调控在雌激素介导的原发乳腺肿瘤信号转导中起关键作用。CD24是如何在乳腺肿瘤中沉默的，这是一个重要而尚未探索的问题。我们的初步研究提供了令人兴奋的证据，表明CD24在乳腺肿瘤中通过启动子超甲基化而在表观遗传学上沉默。到目前为止，还没有关于CD24在乳腺肿瘤中与周围正常组织相比沉默的频率和具体程度的数据。此外，其荷尔蒙影响以及临床和治疗意义尚不清楚。在进行昂贵和劳动密集型的大型流行病学研究之前，有必要建立可靠的初步数据，说明乳腺癌中CD24沉默的频率及其与ER1表达的相关性。这项初步研究将比较40例ER1阳性和40例阴性的乳腺肿瘤及其周围病理正常组织中CD24甲基化的频率。这项初步研究的成功完成将为我们未来广泛的流行病学研究提供重要的初步数据。我们拥有一支优秀的合作团队，其中包括乳腺癌、流行病学、表观遗传学和生物统计学方面的专家，他们对与我们合作感到兴奋。 与公共卫生相关：像他莫昔芬这样的内分泌疗法在激素受体阳性的乳腺癌绝经前妇女中仍然很重要，因为它对雌激素受体(ER1)阳性的妇女效果最好，不幸的是，据估计，接受他莫昔芬治疗5年的妇女中有三分之一将在15年内复发，这表明这些是内分泌抵抗型肿瘤，约占所有乳腺癌的四分之一。肿瘤中激素调节基因的沉默是导致这种耐药性的已知原因，这个试点项目将集中在乳腺肿瘤中荷尔蒙靶基因之一(CD24)与周围正常组织相比的沉默发生率及其与激素受体状态的相关性。这项先导性研究的结果将为计划未来更大规模的研究提供重要数据，以更好地了解这种沉默在治疗抵抗和临床结果中的作用。

DESCRIPTION (provided by applicant): 1. Abstract Two-thirds of breast cancers express estrogen receptor alpha (ER1) and rely upon ER1 signaling for their growth. Estrogen deprivation is a powerful treatment for ER1 positive breast cancers. However, intrinsic and acquired resistance to endocrine therapy remains a significant cause of disease relapse and mortality in ER1 positive tumors. Epigenetic silencing of ER1 downstream target genes is recently identified as a critical factor in endocrine therapy resistance. For example, several recent findings confirmed the clinical and therapeutic significance of the epigenetic silencing of ER1 target genes like HOXB13. CD24 is gaining significant attention in breast cancer research in connection with its negativity in breast tumor initiation, metastasis, and as a potential breast cancer stem cell (BCSC) marker. Though CD24 is expressed in primary tumors, several, studies have shown that CD24 negative cells are highly tumorigenic and its over- expression in negative breast cancer cells results in the loss of metastatic potential. This suggests that the loss of CD24 expression may be critical for gaining metastatic potential. Interestingly, epithelial cells with the CD44 positive CD24 low/absent marker combination (ESA????/low) are considered putative BCSCs. We have previously published that the high prevalence of BCSCs in primary tumors favors distant metastasis. Similarly epithelial mesenchymal transition (EMT) in human mammary epithelial cells resulted in CD24 negative phenotype with enriched tumor-initiating and metastatic potential. Our previous publication showed that estrogen represses CD24 transcription and ER1 binds to palindromic EREs in the CD24 promoter. A recent ONCOMINE analysis of 17 independent breast cancer studies suggested a strong inverse correlation between ER1 positivity and CD24 expression. This suggests the possibility that CD24 differential regulation is critical in estrogen-mediated signaling of primary breast tumors. How CD24 is getting silenced in breast tumors is an important and unexplored question. Our preliminary studies gave exciting evidence that CD24 is epigenetically silenced in breast tumors by promoter hypermethylation. To date there has been no data available regarding how frequently and specifically CD24 is silenced in breast tumors compared to the surrounding normal tissues. Also its hormonal influence as well as clinical and therapeutic significance is not known. Before performing expensive and labor intensive larger epidemiological studies, it is necessary to create reliable preliminary data on the frequency of CD24 silencing in breast cancer and its correlation to ER1 expression. This pilot study will compare the frequency of CD24 methylation in 40 ER1-positive and 40 negative breast tumors and their pathologically normal surrounding tissues. Successful completion of this pilot study will provide critical preliminary data for our future extensive epidemiological study. We have an excellent team of collaborators including experts in breast cancer, epidemiology, epigenetics, and biostatistics, who are excited to work with us. PUBLIC HEALTH RELEVANCE: Project Narrative Endocrine therapy like Tamoxifen treatment remains important in premenopausal women with hormone receptor positive breast cancer as it work best in women whose tumors are positive for estrogen receptor (ER1) and unfortunately it is estimated that one third of women treated with Tamoxifen for 5 years will have a recurrence within 15 years suggesting these are endocrine resistant tumors which represents about one-fourth of all breast cancers. Silencing of hormone regulated genes in tumors are known to cause this resistance and this pilot project will focus on the prevalence of the silencing of one of the hormone target genes (CD24) in breast tumors compared to the surrounding normal tissues and its correlation to hormone receptor status. Results from this pilot study will provide important data to plan future larger studies to better understand the role of this silencing in therapeutic resistance and clinical outcome.