In Vivo Simultaneous Imaging of Vascular Pool and Hypoxia with a HT-29 Tumor Model: the Application of Dual-Isotope SPECT/PET/CT
In Vivo Simultaneous Imaging of Vascular Pool and Hypoxia with a HT-29 Tumor Model: the Application of Dual-Isotope SPECT/PET/CT
复制标题
DOI：
--
复制
发表时间：
2015-12
期刊：
影响因子：
--
通讯作者：
Naoya Adachi;Yukie Yoshii;T. Furukawa;Mitsuyoshi Yoshimoto;Yasuto Takeuchi;M. Inubushi;H. Wakizaka;Z. Ming-rong;Atsushi B. Tsuji;Masashi Takahashi;Y. Fujibayashi;T. Saga
中科院分区：
文献类型：
--
作者：
Naoya Adachi;Yukie Yoshii;T. Furukawa;Mitsuyoshi Yoshimoto;Yasuto Takeuchi;M. Inubushi;H. Wakizaka;Z. Ming-rong;Atsushi B. Tsuji;Masashi Takahashi;Y. Fujibayashi;T. Saga
研究肿瘤中的血管和缺氧对了解肿瘤生物学，制定肿瘤治疗策略具有重要意义。------------------------------------------------------------------------ * 相应的作者。最近，一种使用矢量SPECT/PET/CT小动物扫描仪（MILabs）的成像技术已经被开发出来，可以使用分别用SPECT和PET核素标记的两种不同的示踪剂同时获得图像。本研究采用SPECT/PET/CT技术，采用99m tc标记的人血清白蛋白（99m Tc-HSA）检测血池，64 cu -二乙酰-双（N 4 -甲基硫代氨基脲）（64 Cu-ATSM）检测缺氧下的过度还原情况，建立了人结肠癌ht -29荷瘤小鼠模型同时观察血管和缺氧的方法。在体内实验之前，通过比较SPECT/PET/CT系统与标准系统在大范围放射性和不同含量比条件下检测到的放射性，对我们设置的99m Tc/ 64 Cu双同位素成像进行了模拟研究，以确认其定量性。对HT-29荷瘤小鼠进行了体内影像学研究。4只小鼠分别在扫描前1 h和10 min静脉注射64 Cu-ATSM （37 MBq）和99m Tc-HSA (18.5 MBq)，扫描前20 min；获得99m Tc/ 64cu双同位素SPECT/PET/CT图像。幻影实验表明，该体系即使在两种同位素共存且含量比在较大范围内变化的情况下也具有较高的定量，表明了体内实验的可行性。使用64个Cu-ATSM和99m Tc-HSA进行体内SPECT/PET/CT成像，可以看到每个探针的分布，并显示在HT-29肿瘤内64个Cu-ATSM高摄取区与99m Tc-HSA高摄取区几乎重叠。我们开发了一种使用体内双同位素SPECT/PET/CT成像同时显示ht -29肿瘤内血管和缺氧的方法。该方法将有助于小鼠肿瘤模型的肿瘤生物学研究和癌症治疗策略的开发。检查活体肿瘤内的血管和缺氧对了解肿瘤生物学和制定癌症治疗策略具有重要意义。对于高血管肿瘤，抗血管生成治疗和抗血管治疗是很有前途的方法。在抗血管生成治疗方面，抗血管内皮生长因子抗体贝伐单抗目前在全球范围内被临床使用[1-4]，在抗血管治疗方面，有一项使用康布司他汀A4磷酸的临床试验[10]。对于低血管肿瘤，通常伴有缺氧，强化治疗是必要的，因为据报道，肿瘤缺氧对化疗和放疗具有耐药性[6-8]。近年来，人们提出了几种治疗肿瘤缺氧区域损伤的方法，如低氧正电子发射断层扫描（PET）成像的强度调制放射治疗[9,10]和碳离子放射治疗，即使在缺氧的情况下，碳离子放射治疗也能通过高线性能量转移束损伤肿瘤细胞[11,12]。然而，考虑到目前癌症根治的难度，需要开发更有效的抗血管生成、抗血管和抗缺氧治疗的药物和治疗方法。此外，这些治疗方法的联合将是有效的方法，因为它们可以攻击肿瘤血管和缺氧密切相关。然而，在小鼠体内荷瘤模型中，仍难以准确准确地观察肿瘤血管和缺氧情况。最近，一种单光子发射计算机断层扫描/正电子发射断层扫描/计算机断层扫描（SPECT/PET/CT）成像技术，由MILabs （Utrecht, Netherlands）发射的VECTor小动物扫描仪，已被报道分别用SPECT和PET核素标记的两种示踪剂获得真正的同时图像。传统上，使用SPECT和PET进行双同位素成像研究是通过两个独立的系统独立获取每个图像[13,14]。相比之下，VECTor系统配备了一个集群针孔准直器，这大大减少了高能湮灭的针孔边缘穿透。-来自PET核素的光子，并使其能够探测到高能？以类似于SPECT核素的方式，从PET核素衍生出-光子，并通过基于光子能量分离图像，同时从正电子发射器和单光子发射器获得高分辨率图像[15,16]。因此，与测量湮灭光子巧合的典型PET系统相比，该系统具有制作PET核素图像的新概念。gordon等人报道，该系统显示出高空间分辨率，PET核素为0.8 mm， SPECT核素[15]为0.5 mm。Miwa等人也证实了使用该系统同时检测99m Tc和18f的性能[17]。在这项研究中，我们开发了一种方法，通过应用这种SPECT/PET/CT技术，可以同时观察肿瘤内血管和缺氧。我们使用99m Tc标记的人血清白蛋白（99m Tc- hsa），用SPECT核素99m Tc标记(半衰期= 6.0 h; 140 keV ？- x线：89%)通过检测血池[18]来显示肿瘤血管。99m tc - hsa在临床前和临床研究中均被报道在多种类型的癌症中检测肿瘤血池，包括结肠癌、肾细胞癌、肝肿瘤[19-21]。我们还使用了64 Cu-二乙酰-双（N 4 -甲基硫代氨基脲）（64 Cu- atsm），用PET核素64 Cu(半衰期= 12.7 h; ？+ -衰减：17.4%；吗?吗?腐烂:38.5%;电子捕获：43%)[22]，检测肿瘤缺氧。Cu- atsm用Cu放射性同位素（如60 Cu、62 Cu和64 Cu）标记，已被开发为靶向肿瘤缺氧区域的显像剂，用于PET[23-26]。许多研究表明，体内和体外肿瘤的缺氧条件与Cu-ATSM积累有关[26-29]。放射性标记的Cu-ATSM积累机制已被研究：Cu-ATSM分子尺寸小，膜通透性高，因此在缺氧等高度还原的细胞内条件下，Cu-ATSM迅速扩散到细胞内，被还原并被困在细胞内[24,29 -31]。一项62 Cu-ATSM的临床研究表明，高水平的缺氧诱导因子-1？（HIF-1）在脑胶质瘤患者的Cu-ATSM摄取区表达。在这项研究中，我们使用SPECT/PET/CT与99m Tc-HSA和64 Cu-ATSM同时进行体内成像，检测HT-29荷瘤小鼠模型的肿瘤血管和缺氧情况。
Investigation of vascularity and hypoxia in tumors is important in understanding cancer biology to developthe therapeutic strategies in cancer treatment. ------------------------------------------------------------------------ *Corresponding author . Recently, an imaging technology with the VECTor SPECT/PET/CT small-animal scanner (MILabs) has been developed to obtain simultaneous images usingtwodifferent tracers labeled with SPECT and PET nuclides, respectively. In this study, we developed amethod to simultaneously visualize vascularity and hypoxia witha human colon carcinoma HT-29tumor-bearing mouse model with 99m Tc-labeled human serum albumin ( 99m Tc-HSA) to detect blood pool, and 64 Cu-diacetyl-bis ( N 4 -methylthiosemicarbazone) ( 64 Cu-ATSM) to detect the over-reduced conditionsunder hypoxia, by applying this SPECT/PET/CT technology.Prior to the in vivo experiments, a phantom study was conducted to confirmquantitativity of the 99m Tc/ 64 Cu dual-isotope imaging with the SPECT/PET/CT system,by comparing radioactivities detected by SPECT/PET/CT system and those of standards under the conditions of wide range of radioactivities and various content ratios, in our settings. An in vivo imaging study was conducted with HT-29 tumor-bearing mice. Both 64 Cu-ATSM (37 MBq) and 99m Tc-HSA (18.5 MBq) were intravenously injected into a mouse (n = 4) at 1 h and 10 min, respectively, before scanning for 20 min; the 99m Tc/ 64 Cu dual-isotope SPECT/PET/CT images were then obtained.The phantom study demonstrated that this system has high quantitativity, even when 2 isotopes co-existed and the content ratio was changed over a wide range, indicating the feasibility for in vivo experiments. In vivo SPECT/PET/CT imaging with 64 Cu-ATSM and 99m Tc-HSA visualized the distribution of each probe and showed that 64 Cu-ATSM high-uptake regions barely overlapped with 99m Tc-HSA high-uptake regions within HT-29 tumors.We developed a method to simultaneously visualize vascularity and hypoxia within HT-29tumors using in vivo dual-isotope SPECT/PET/CT imaging. This methodology would be useful for studies oncancer biology with mouse tumor models anddevelopment of the treatment strategies against cancer. Examination of vascularity and hypoxia within in vivotumors is important in understanding the biology of cancer anddevelopmentof the therapeutic strategies in cancer treatment. For hypervascular tumors, antiangiogenic therapy and antivascular therapy are promising approaches. For antiangiogenic therapy, the anti-vascular endothelial growth factor antibody bevacizumab is now clinically used worldwide [1-4], and for antivascular therapy, a clinical trial withcombrestatin A4 phosphate is conducted[5]. For hypovascular tumor, which is usually associated with hypoxia, intensive treatment is necessary, since tumor hypoxia is reportedly resistant to chemotherapy and radiotherapy [6-8]. In recent years, several therapeutic methods have been proposedto damage to hypoxic regions within tumors, such as intensity modulated radiation therapy with hypoxia positron emission tomography (PET) imaging [9, 10], and carbon-ion radiotherapy, which is able to damage tumor cells even in the absence of oxygen by high linear energy transfer beam [11, 12]. However, considering the difficulty of cancer radical cure at the present moment, more effective drugs and treatment methods for antiangiogenic, antivascular, and antihypoxia therapies need to be developed. In addition, combinations of these therapies would be effective approaches, since they can attacktumor vascularity and hypoxia closely linked each other.However, it is still difficult to observe tumor vascularity and hypoxia both coincidently and concisely in in vivo tumor-bearing mouse model. Recently, a technology of single-photon emission computed tomography/positron emission tomography/computed tomography(SPECT/PET/CT) imaging with the VECTor small-animal scanner, launched from MILabs (Utrecht, Netherlands), has been reportedto obtain truly simultaneous images with twotracers labeled with SPECT and PET nuclides, respectively. Conventionally, dual-isotope imaging studies with SPECT and PET have been performed by obtaining each image independently with 2 separate systems [13, 14]. In contrast, the VECTor system is equipped with a clustered pinhole collimator, which dramatically reduces pinhole-edge penetration of high-energy annihilation ?-photons from PET nuclides and enables it to detect high-energy ?-photons derived from PET nuclides, in a manner similar to SPECT nuclides, and to obtain high-resolution images from positron emitters and single-photon emitters at the same time by separating the images based on the photon energy [15, 16]. Thus, this system has a novel concept to make images of PET nuclides, compared to the typical PET system, which measures the coincidence of annihilation ?-photons. Goorden et al. have reported that this system shows high spatial resolution, with 0.8 mm for PET nuclides and 0.5 mm for SPECT nuclides [15]. Miwa et al. also confirmed its performance in simultaneous detection of 99m Tc and 18 F using this system [17]. In this study, we developed a methodology to easily observe intratumoralvascularity and hypoxia in a simultaneous manner,by applyingthis SPECT/PET/CT technology. We used 99m Tc-labeled human serum albumin ( 99m Tc-HSA) labeled with a SPECT nuclide 99m Tc (half-life = 6.0 h; 140 keV ?-ray: 89%) to visualize tumor vascularity by detecting blood pool [18]. The 99m Tc-HSAhas been reported to detect tumor blood pool in many types of cancer, including colon cancer, renal cell carcinoma, and liver tumor in both preclinical and clinical studies [19-21]. We also used 64 Cu-diacetyl-bis ( N 4 -methylthiosemicarbazone) ( 64 Cu-ATSM), labeled with a PET nuclide 64 Cu (half-life = 12.7 h; ? + -decay: 17.4%; ? ? -decay: 38.5%; and electron capture: 43%) [22], to detect tumor hypoxia. The Cu-ATSM, labeled with Cu radioisotopes, such as 60 Cu, 62 Cu, and 64 Cu, has been developed as an imaging agent targeting hypoxic regions in tumors for use with PET [23-26].Many studies have demonstrated that Cu-ATSM accumulation is associated with hypoxic conditions of tumor in vitro and in vivo [26-29]. The mechanism of radiolabeled Cu-ATSM accumulation has been studied: Cu-ATSM has small molecular sizeand high membrane permeability, and thus rapidly diffuses into cells and is reduced and trapped within cells under highly reduced intracellular conditions such as hypoxia [24, 29-31]. A clinical study with 62 Cu-ATSM demonstrated that high levels of hypoxia-inducible factor-1? (HIF-1?) expression were found in Cu-ATSM uptake regions in the tumors of patients with glioma [32]. In this study, we performed simultaneous in vivo imaging using a SPECT/PET/CT with 99m Tc-HSA and 64 Cu-ATSM for detecting tumor vascularity and hypoxia with a HT-29 tumor-bearing mouse model.