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手段。最近的技术发展显著提高了肿瘤剂量传递的精确度，使放射治疗成为更有效的控制肿瘤生长的方法。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耐药性的严重影响。肿瘤的异质性被证明在辐射诱导的细胞再繁殖和辐射抵抗中起着关键作用。临床上，乳腺癌治疗的主要失败与HER-2/neu(ErbB2，EGFR家族成员)的过度表达有关。最近的数据进一步表明，标记为CD44+/CD24-/Low的乳腺癌干细胞(CSCs)在总肿瘤细胞总数中所占比例不到1%，能够自我更新并在放射治疗中存活。在HER-2阴性的乳腺癌MCF-7细胞中强制过表达HER-2可通过激活转录因子NF-kB而诱导放射抵抗。此外，HER-2激活的核因子-kB反过来刺激HER-2基因的表达，表明乳腺癌细胞在放射治疗中生存所需的HER-2-NF-kB-HER-2途径。HER-2在照射后的异种移植瘤中被诱导，重要的是，在照射后的异种移植瘤和乳腺癌细胞中，HER-2最好与CD44+共激活，而不是与CD24-/Low共激活。对144例乳腺癌患者的180个肿瘤进行免疫组织化学分析，发现HER-2阳性细胞数与CD44+细胞数呈正相关，而与CD24-/Low细胞数无相关性，且HER-2阳性细胞数在复发的浸润性肿瘤中更常见。因此，从辐射抵抗细胞系、异种移植瘤和乳腺癌样本中获得的所有结果都表明了辐射抵抗乳腺癌干细胞的一个新的和潜在的重要特征。这项研究的中心假设是，适应性放射抵抗是由核因子-kB介导的HER-2过表达导致的辐射诱导的乳腺癌干细胞再繁殖引起的。这项应用将测试和验证这种新型的抗辐射乳腺癌干细胞生物标记物，即NF-kB p65+/HER+/CD44+/CD24-/low，以识别和重新敏化抗辐射乳腺癌细胞。目的1，检测和确认耐辐射乳腺癌干细胞的特征p65+/HER-2+/CD44+/CD24-/low；目的2，检测HER-2/CD44+是一种新的敏感的细胞表面生物标志物，通过小鼠体内成像分析检测耐辐射的乳腺癌干细胞；目的3，鉴定p65+/Her-2+/CD44+/CD24-/low特征及其在病理诊断乳腺癌中的放射抵抗。

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.