Pramila Paudyal

The aim of this study was to develop the near infrared fluorescence (NIRF)-based imaging agent for the visualization of vascular endothelial growth factor (VEGF) in colon cancer. AlexaFluor 750 conjugating with bevacizumab, and injected intravenously into nude mice bearing VEGF over-expressing HT29 human colorectal cancer. Optical imaging was performed at 15 min, 24 h and 48 h post injection. Immunofluorescences staining of the tumor sections were performed. HT29 colorectal cancer xenografts were clearly visualized with bevacizumab-AlexaFluor 750. Ex vivo analysis showed 2.1 ± 0.4%, 37.6 ± 6.3% and 38.5 ± 6.2% injected dose/g accumulated in the tumors at 15 min, 24 h and 48 h respectively. Tumor uptake was significantly decreased in pretreated with excess of bevacizumab (p = 0.002). Immunofluorescence analysis showed strong staining of anti-CD 31 antibody around the blood vessels. Anti-VEGF-A and bevacizumab showed heterogeneous expression throughout the tumor. Current study successfully detected the VEGF expression in HT29 colorectal cancer xenografts, signifying as a potential agent for non-invasive imaging of VEGF expression, which may be applied in clinical practice.

Non‐small cell lung carcinomas (NSCLC) overexpress the Her2/neu gene in approximately 59% of cases. Trastuzumab, a humanized monoclonal antibody, interferes with Her2 signaling and is approved for the treatment of Her2/neu overexpressing breast cancer. However, its therapeutic use in Her2/neu overexpressing NSCLC remains obscure. The present study aimed to determine the role of ⁶⁴Cu‐labeled trastuzumab positron emission tomography (PET) for non‐invasive imaging of Her2/neu expression in NSCLC. Trastuzumab was conjugated with the bifunctional chelator 1, 4, 7, 10‐tetraazacyclododecane‐1, 4, 7, 10‐tetraacetic acid (DOTA) and radiolabeled with ⁶⁴Cu. The molecular specificity of DOTA‐trastuzumab was determined in NSCLC cell lines with Her2/neu overexpression (NCI‐H2170) and negative expression (NCI‐H520). Imaging of Her2/neu expression was performed in NCI‐H2170 tumor‐bearing mice with ⁶⁴Cu‐DOTA‐trastuzumab PET and ⁶⁴Cu‐DOTA‐IgG. In vitro studies revealed specific binding of DOTA‐trastuzumab in the Her2/neu positive NCI‐H2170 cells, while no binding was seen in the Her2/neu negative NCI‐H520 cell line. Biodistribution and PET studies revealed a significantly high accumulation of ⁶⁴Cu‐DOTA‐trastuzumab in the Her2/neu overexpressing NCI‐H2170 tumor at 24 and 48 h post‐injection (21.4 ± 1.4% and 23.2 ± 5.1% injection dose/gram (% ID/g), respectively). PET imaging of Her2/neu negative NCI‐H520 tumors showed much less uptake of ⁶⁴Cu‐DOTA‐trastuzumab (4.0% ID/g). The NCI‐H2170 tumor uptake of ⁶⁴Cu‐DOTA‐trastuzumab was significantly higher than that of ⁶⁴Cu‐DOTA‐IgG (P < 0.0001). ⁶⁴Cu‐DOTA‐trastuzumab showed a very clear image of a Her2/neu positive tumor and appeared to be effective as a PET tracer for imaging of Her2/neu gene expression in NSCLC, suggesting its potential clinical use for identifying patients that might benefit from trastuzumab‐based therapy.(Cancer Sci 2010; 101: 1045–1050)