NF-kB-mediated HER-2 overexpression in radioresistant breast cancer stem cells?

描述（由申请人提供）： 放射治疗仍然是主要的抗癌方式。最近的技术发展显着提高了肿瘤剂量输送的精度，使放射治疗成为一种更有效的肿瘤生长控制方法。然而，由于辐射诱导的适应性反应，这种治疗的有效性可能会受到肿瘤抗性的严重影响。据报道，肿瘤异质性在辐射诱导的细胞再增殖和辐射抵抗中发挥关键作用。临床上，乳腺癌治疗失败的主要原因与HER-2/neu（ErbB 2，EGFR家族成员）的过度表达有关。最近的数据进一步表明，乳腺癌干细胞（标记为CD 44 +/CD 24-/低的CSC）占总肿瘤细胞群的不到1%，能够自我更新并在放射治疗中存活。HER-2在HER-2阴性乳腺癌MCF-7细胞中的过度表达由于转录因子NF-κ B的活化而诱导辐射抗性。此外，HER-2激活的NF-kB反过来刺激HER-2基因表达，表明乳腺癌细胞在放疗中存活所需的环状HER-2-NF-kB-HER-2途径。HER-2在经辐照的异种移植肿瘤中被诱导，并且重要的是，HER-2优选地在经辐照的异种移植肿瘤和在分次剂量的辐射下存活的乳腺癌细胞中与CD 44+共活化，而不与CD 24-/低共活化。对144例乳腺癌患者的180个肿瘤进行免疫组化分析，发现HER-2阳性细胞数与CD 44+细胞数成正比，而与CD 24- /low细胞数无关，HER-2在复发浸润性肿瘤中更常见。因此，从放射抗性细胞系、异种移植肿瘤和乳腺癌标本获得的所有结果证明了放射抗性乳腺癌干细胞的新的和潜在的重要特征。所提出的研究的中心假设是，适应性辐射抗性是由辐射诱导的乳腺癌干细胞再增殖引起的，这是由于NF-κ B介导的HER-2过表达。本申请将测试和验证这种抗辐射乳腺癌干细胞的新生物标志物，即，NF-kB p65+/HER+/CD 44 +/CD 24-/low，以鉴定和再致敏放射抗性乳腺癌细胞。有三个具体目标：目的1、检测并证实乳腺癌放射抵抗干细胞的特征p65+/HER-2+/CD 44 +/CD 24-/low，目的2、通过小鼠体内成像分析，验证HER-2/CD 44+是检测乳腺癌放射抵抗干细胞的一种新的敏感的细胞表面标志物;目的3：探讨病理诊断的乳腺癌p65+/HER- 2+/CD 44 +/CD 24-/low和放射抵抗的特征。公共卫生相关性：使用新的细胞表面标志物阐明放射抗性乳腺癌干细胞将提供肿瘤适应性抗性的重要见解。p65+/HER-2+/CD 44 +/CD 24-/low这一新的乳腺癌耐辐射干细胞的特征如果被发现，将有望成为一种有效的检测和再致敏耐辐射乳腺癌细胞的方法，从而显著提高乳腺癌患者的总体治愈率。

DESCRIPTION (provided by applicant): Radiotherapy continues to be the major anti-cancer modality. Recent technical developments significantly increase the precision of tumor dose delivery, making radiotherapy a more efficient approach for tumor growth control. However, the effectiveness of this treatment may be severely compromised by tumor resistance due to radiation-induced adaptive response. Tumor heterogeneity is documented to play a key role in radiation-induced cell repopulation and radioresistance. In clinic, the major failure of breast cancer treatment is associated with the overexpression of HER-2/neu (ErbB2, a member of EGFR family). Recent data further suggest that breast cancer stem cells (CSCs with marker CD44+/CD24-/low) consisting of less than 1% of total tumor cell population are able to self-renew and survive the radiation therapy. Enforced overexpression of HER-2 in HER-2-negative breast cancer MCF-7 cells induces radioresistance due to activation of transcription factor NF-kB. In addition, HER-2-activated NF-kB in turn stimulates HER-2 gene expression, indicating a loop-like HER-2-NF-kB-HER-2 pathway required for breast cancer cells to survive radiotherapy. HER-2 is induced in irradiated xenograft tumors and, importantly, HER-2 is preferably co-activated with CD44+ but not with CD24-/low in irradiated xenograft tumors and breast cancer cells surviving the radiation with fractionated doses. Immunohistochemistry analysis of total 180 tumors from 144 breast cancer patients revealed that the number of HER-2-positive cells is proportionally related to the number of CD44+ but not CD24- /low cells, and HER-2 was more frequently detected in the recurrent invasive tumors. Thus, all of the results obtained from radioresistant cell lines, xenograft tumors and breast cancer specimens demonstrate a new and potentially important feature of radioresistant breast cancer stem cells. The central hypothesis of the proposed study is that adaptive radioresistance is caused by radiation- induced repopulation of breast cancer stem cells due to NF-kB-mediated HER-2 overexpression. This application will test and verify this novel biomarker of radioresistant breast cancer stem cells, i.e., NF-kB p65+/HER+/CD44+/CD24-/low, to identify and re-sensitize radioresistant breast cancer cells. There are three specific aims: Aim 1, to detect and confirm the radioresistant breast cancer stem cell feature, p65+/HER-2+/CD44+/CD24-/low in radioresistant breast cancer cells; Aim 2, to test that HER-2/CD44+ is a novel sensitive cell surface biomarker to detect radioresistant breast cancer stem cells by in vivo mouse imaging analysis; and Aim 3, to characterize the feature p65+/HER- 2+/CD44+/CD24-/low and radioresistance in pathologically diagnosed breast cancers. PUBLIC HEALTH RELEVANCE: Elucidation of radioresistant breast cancer stem cells using novel cell surface markers will provide critical insights of tumor adaptive resistance. The new feature of radioresistant breast cancer stem cells, p65+/HER-2+/CD44+/CD24-/low , if identified, will promise an efficient approach to detect and re-sensitize radioresistant breast cancer cells and thus may significantly enhance the overall cure rate of breast cancer patients.