School of Medicine, University of California, Davis, CA, USA.
Int J Cancer. 2013 Apr 1;132(7):1613-23. doi: 10.1002/ijc.27837. Epub 2012 Oct 11.
Noninvasive localized measurement of extracellular pH in cancer tissues can have a significant impact on the management of cancer. Despite its significance, there are limited approaches for rapid and noninvasive measurement of local pH in a clinical environment. In this study, we demonstrate the potential of noninvasive topical delivery of Alexa-647 labeled pHLIP (pH responsive peptide conjugated with Alexa Fluor(®) 647) to image changes in extracellular pH associated with head and neck squamous cell carcinoma using widefield and high resolution imaging. We report a series of preclinical analyses to evaluate the optical contrast achieved after topical delivery of Alexa-647 labeled pHLIP in intact fresh human tissue specimens using widefield and high-resolution fluorescence imaging. Using topical delivery, Alexa-647 labeled pHLIP can be rapidly delivered throughout the epithelium of intact tissues with a depth exceeding 700 µm. Following labeling with Alexa-647 labeled pHLIP, the mean fluorescent contrast increased four to eight fold higher in clinically abnormal tissues as compared to paired clinically normal biopsies. Furthermore, the imaging approach showed significant differences in fluorescence contrast between the cancer and the normal biopsies across diverse patients and different anatomical sites (unpaired comparison). The fluorescence contrast differences between clinically abnormal and normal tissues were in agreement with the pathologic evaluation. Topical application of fluorescently labeled pHLIP can detect and differentiate normal from cancerous tissues using both widefield and high resolution imaging. This technology will provide an effective tool to assess tumor margins during surgery and improve detection and prognosis of head and neck cancer.
非侵入性的局部测量癌症组织中的细胞外 pH 值对癌症的治疗具有重要影响。尽管其意义重大，但在临床环境中，快速和非侵入性地测量局部 pH 值的方法有限。在这项研究中，我们展示了非侵入性局部递送 Alexa-647 标记的 pHLIP（与 Alexa Fluor®647 缀合的 pH 响应肽）的潜力，以使用广角和高分辨率成像来成像与头颈部鳞状细胞癌相关的细胞外 pH 值变化。我们报告了一系列临床前分析，以评估在完整的新鲜人体组织标本中使用广角和高分辨率荧光成像进行局部递送后获得的光学对比度。使用局部递送，Alexa-647 标记的 pHLIP 可以快速递送到完整组织的上皮中，深度超过 700 µm。用 Alexa-647 标记的 pHLIP 标记后，与配对的临床正常活检相比，临床异常组织中的平均荧光对比度增加了四到八倍。此外，该成像方法在不同患者和不同解剖部位之间显示出癌症和正常活检之间荧光对比度的显著差异（非配对比较）。荧光对比度异常组织与正常组织之间的差异与病理评估一致。荧光标记的 pHLIP 的局部应用可以使用广角和高分辨率成像来检测和区分正常组织和癌组织。这项技术将为手术期间评估肿瘤边缘提供有效的工具，并提高对头颈癌的检测和预后。
