Tumor-specific agents for cancer imaging

描述(申请人提供)：该项目建议使用基于四吡咯的结合物来荧光标记结直肠肿瘤病灶。结直肠癌是第二种最常见的内部恶性肿瘤，在美国有超过50,000人死于这种疾病。由于早期疾病缺乏外部迹象或症状，对早期癌症的敏感识别是预防性筛查的关键。目前的筛查技术，主要是结肠镜检查，可以发现大腺瘤性病变，但往往会漏掉至少两种形式的早期结直肠癌：小腺瘤(5 Mm)和扁平病变。激光共聚焦内窥镜目前被用于原位组织学检查，作为内窥镜检查的补充。然而，使用这项技术仍有多达三分之一的腺瘤被遗漏，因为目前使用的荧光显像剂非选择性地对正常和肿瘤粘膜组织进行染色。在这个项目中，我们建议合成和研究选择性靶向结肠癌细胞的新的卟啉和酞菁荧光标记物。具体地说，我们的策略涉及靶向表皮生长因子受体(EGF-R)和人类癌胚抗原(CEA)，这两种受体都在结肠癌细胞中过度表达。我们提出的研究是基于我们对一个小的卟啉和酞菁-多肽结合物以及一个酞菁-CEA结合物的初步研究。我们的具体目标是：(1a)合成一系列新的与EGF-R多肽配体和抗CEA单抗偶联的卟啉和Pc，以增强结肠癌的靶向性；(1b)利用人结肠癌细胞体外评价新的结合物；(2a)将有希望的结合物暴露在结肠癌与周围结肠癌的器官培养中；(2b)直接将选定的结合物注射到裸鼠原位生长的结肠癌中；以及(2c)将选定的显像剂局部注射到直肠黏膜上，并研究它们的体内荧光发射和结肠癌细胞选择性。卟啉作为生物分子的标记物和光动力疗法的治疗剂已经使用了100多年，但目前已知的卟啉并不是肿瘤靶标。天然生成的卟啉大环在620-660 nm范围内吸收和发射，而酞菁则进一步吸收和发射到近红外区域(670-750 nm)，在那里光线穿透组织更深，其他分子的干扰最小，自发荧光最小。拟议的研究具有极高的相关性，因为它们可以更有效地及早发现CRC，从而大大降低CRC的发病率和死亡率。此外，这些研究可能为开发更有效的肿瘤靶向显像剂和化疗药物奠定基础。 公共卫生相关性：我们建议的计划与公共健康密切相关，因为癌症仍然是全国第二大最常见的死亡原因，尤其是结直肠癌，是第二大最常见的内部恶性肿瘤。有效的早期发现肿瘤以及肿瘤浸润区和肿瘤转移将对治疗计划、肿瘤治疗反应和整体治疗结果产生巨大影响，将以最小的成本增加癌症治疗的成功率，并将提高患者的生活质量。

DESCRIPTION (provided by applicant): This project proposes to use tetrapyrrole-based conjugates to fluorescently label colorectal tumor foci. Colorectal cancer is the second most common solid internal malignancy and over 50,000 deaths in the U.S. are attributable to this disease. Since the early disease lacks outward signs or symptoms, sensitive recognition of early cancers is key to preventative screening. Current screening techniques, primarily colonoscopy, identify large adenomatous lesions but often miss at least two forms of early colorectal cancer: small adenomas (<5 mm) and flat lesions. Confocal laser endomicroscopy is currently being used for in situ histology as a complement to endoscopy. However up to one-third of adenomas are still missed using this technique, because the fluorescent imaging agents currently in use non-selectively stain normal as well as neoplastic mucosal tissue. In this project we propose to synthesize and investigate new porphyrin and phthalocyanine fluorescent markers that selectively target colon cancer cells. Specifically our strategy involves the targeting of epidermal growth factor receptors (EGF-R) and human carcinoembryonic antigen (CEA), both over-expressed in colon cancer cells. Our proposed research is based on our preliminary investigations of a small library of porphyrin- and phthalocyanine-peptide conjugates and one phthalocyanine-CEA conjugate. Our Specific Aims are: (1a) To synthesize a new series of porphyrins and Pc conjugated to EGF-R peptide ligands and anti-CEA MAb in order to enhance colon cancer targeting; (1b) to evaluate the new conjugates in vitro using human colon carcinoma cells; (2a) to expose promising conjugates to a organ culture of colon cancer with surrounding colon; (2b) to directly inject selected conjugates into colon tumors grown orthotopically in nude mice; and (2c) to instill topically onto rectal mucosa selected imaging agents and investigate their in vivo fluorescence emission and CRC tumor cell selectivity. Porphyrins have been used for over 100 years as labels for biomolecules and as treatment agents by photodynamic therapy, but currently known porphyrins are not tumor-targeted. While naturally occurring porphyrin macrocycles absorb and emit within the 620-660 nm range, phthalocyanines absorb and emit further into the near-IR region (670-750 nm) where light penetrates deeper through tissues and interference from other molecules and autofluorescence is minimized. The proposed studies are of extremely high relevance since they could lead to a much more effective early detection of CRC which could greatly reduce the incidence and mortality of CRC. Furthermore, these studies could form the basis for the development of more efficient tumor-targeted imaging agents and chemotherapeutics. PUBLIC HEALTH RELEVANCE: Our proposed program is of great relevance to public health since cancer is still the second most common cause of death in the Nation and, in particular colorectal cancer, is the second most common solid internal malignancy. The effective early detection of tumors as well as tumor infiltrative areas and tumor metastasis will have an enormous impact on treatment planning, tumor response to treatment and overall treatment outcome, will increase the success of cancer treatment with minimal cost, and will increase the patient's quality of life.