The low rate of cure of certain cancers such as lung cancer, the most common causes of cancer death, is an important health problem. Early detection appears currently to be the only way of improving the high mortality rate, but is quite difficult because of the lack of symptoms in early disease. Moreover, lung cancer is mimicked in its in vivo image appearance by benign lesions and processes that lower the specificity of detection. Current imaging methods include chest x-ray, CT, and MRI. While these current methods are able to identify curable lung cancer they also result in many false positives. They are also limited in the size of the lung nodules they can detect. Using available criteria, sensitivity for lung cancer detection is high, but specificity and positive predictive value are only moderate. Thus there is a need for enhanced sensitivity and specificity for cancer cells. Our Anti-transferrin Receptor scFv-antibody fragment (TfRscFv) immunoliposome complex (scL) is a nanoconstruct (~100 nm) for delivery of gene therapy to tumors. It has been shown to target various types of human tumor cells in vivo when implanted as xenografts in mice and is now in Phase I clinical trials for delivery of wtp53. What we are proposing in this application is a quantum jump in diagnostic accuracy, an approach specific to cancer and best for small cancers such as lung cancer. The method we are developing is a nano- sized immunoliposome complex delivering superparamagnetic iron oxide particles (SPIO). Iron Oxide particles are both paramagnetic and super-paramagnetic, giving a biphasic response with both T1 and T2* features. This complex targets cancer cells with high selectivity. Thus the efficient delivery of SPIO directly into the tumor cells by the scL-SPIO complex of this application can increase the conspicuity of the lung tumor cells. Moreover, based on previous studies, the nanocomplex delivered contrast agent which is the focus of this application should accumulate within the cancer cells themselves remaining for an extended period (hours) allowing the contrast in non-cancer areas to wash out, further enhancing cancer conspicuity. In preliminary studies using an as yet unoptimized scL-SPIO complex, we demonstrated tumor cell specificity as compared to free SPIO, and enhanced image intensity. More importantly, in earlier studies with scL complexed with another imaging agent, gadopentate dimeglumine (gad-d), in a lung tumor model, the scL-gad-d (and not free gad-d) was able to enhance and identify lung tumors as small as 1-4 pixels (0.1-0.4mm), a size smaller than possible with current technology. No toxicity was found with this complex. In this application we will optimize the scL- SPIO complex and fully characterize its capabilities for use in early detection of lung cancer in a mouse model of human lung cancer and extend our studies to a mouse model of primary lung cancer. In collaboration with investigators at NIST and NCI we will also asses the magnetic properties of the complex and determine it sub cellular localization and trafficking through the cell. Our goal is to perform the majority of the studies necessary for filing an IND as we aim to move rapidly towards clinical trials. If cancer is detected early (e.g. Stage I), it can in many instances be cured (lower mortality). The challenge is to be able to find and positively identify the cancer at this early stage, particularly lung cancer. While the current methods of detection are good, they can only detect tumors of a certain size. Moreover, lung cancer is often mimicked during imaging by non-cancerous lesions, resulting in uncertainty and many false positives, which are often resolved only by following growth of the tumor. Thus there is a pressing need for imaging agents that increase sensitivity and specificity. Our tumor-specific nano complex delivery of an MR imaging agent, e.g. gad-d and iron oxide, has shown great promise in our preliminary studies in this regard, demonstrating that its high affinity for cancer cells in the lung can result in improved sensitivity in detecting tumors and in overall specificity. The development of an imaging agent that can lead to earlier detection is a high priority in the war on cancer and could lead to increased survival.
