基于碳酸酐酶9的超声乏氧分子成像监测乳腺癌内分泌治疗抵抗的实验研究

Endocrine drug therapy (tamoxifen) recently plays an important role in the therapy of patients with estrogen receptor(ER)-positive breast cancer. However,during the clinical intervention, about 40% to 50% of patients with ER-positive breast cancer underwent the anti-endocrine responsiveness. Extracellular acid microenvironment induced by tumor hypoxia may lead to the accumulation and absorption of basic drugs and is also considered as the main reason for resistance to the weak basic endocrine drug, such as tamoxifen.Carbonic anhydrase IX as a important factor that balances the acid-basic microenvironment outside the cell, reversibly transfers CO2 into carbonic acid , which increases the degree of extracellular acid and then has impact on the endocrine drug entering into tumor cells. CAIX has negative correlation with the effect of endocrine drug treatment. CAIX is also a sensitive tumor hypoxia inner marker, which can early detect the intratumor hypoxia and resistance of endocrine therapy. Based on the previous preparation of ultrasound targeted molecular and experience on its application in the in vivo experiment, we will construct a ultrasound molecular probe targeted tumor hypoxia.Its reliability of labeling the cells will be validated in vitro. Ultrasound imaging will be performed after injection of the molecular probe in mice with ER-positive breast cancer received drug therapy of tamoxifen to monitor the change of tumor hypoxia during different time points.The aim of the project is to investigate the feasibility and reliability of ultrasound molecular probe targeted tumor hypoxia in predicting and monitoring early response to tamoxifen in ER-positive breast cancer.

以他莫昔芬为代表的内分泌药物治疗是目前雌激素受体阳性乳腺癌患者的重要治疗手段。但在临床治疗过程中，仍有40-50%乳腺癌患者出现内分泌治疗抵抗。肿瘤性乏氧所导致的细胞外酸性微环境能够抑制碱性药物的累积和吸收，也是弱碱性内分泌药物出现耐药的主要原因之一。碳酸酐酶9作为肿瘤乏氧状态下调节细胞外酸碱平衡的重要因子，可逆性的催化二氧化碳转化为碳酸，使得细胞外酸性程度增加，影响内分泌药物进入肿瘤细胞内，与内分泌治疗效果成负相关，能够早期发现肿瘤内部的乏氧区域，提示内分泌抵抗。本研究拟在前期超声靶向分子探针成功制备及其在动物实验有效应用的基础上，构建基于碳酸酐酶9的靶向乏氧的超声分子探针，体外验证其标记乏氧细胞的可靠性，随后将其注入接受内分泌药物治疗的雌激素受体阳性的乳腺癌荷瘤裸鼠体内，在不同时间点行超声分子成像，监测肿瘤内部乏氧微环境变化，验证超声乏氧分子成像早期评估乳腺癌内分泌治疗抵抗的可行性。

他莫昔芬是ER阳性乳腺癌内分泌治疗的主要方式。然而，仍然有一定比例的乳腺癌出现内分泌治疗获得性耐药，并伴有肿瘤乏氧的形成。我们研究的目的就是通过探测他莫昔芬耐药的乏氧微环境变化，为此我们制备了PLGA-PEG-mAbCAIX 纳米级微泡形成超声靶向乏氧分子成像，早期评估乳腺癌内分泌耐药。我们首先检测55例内分泌治疗后复发的乳腺癌病例。体外检测MDA-MB-231，MCF-7以及T47D三种乳腺癌细胞系，检测他莫昔芬耐药后CAIX, HIF-1, GLUT1以及VEGF四个指标的变化。同时，我们发现乏氧指标带来的ATP水平的变化与他莫昔芬耐药相关。最重要的是，体内外实验发现PLGA-PEG-mAbCAIX 纳米级微泡能够有效探测乳腺癌细胞他莫昔芬处理后乏氧微环境变化，而且与荷瘤移植裸鼠的CAIX表达相关。进一步发现体内超声靶向分子显像能够早期探测乳腺癌裸鼠模型中内分泌治疗抵抗。因此，基于靶向乏氧的超声纳米级分子探针能够有效检测ER阳性乳腺癌他莫昔芬早期出现抵抗的过程，为临床及时调整治疗方案提供理论依据。