Stable Expression of the Sodium Iodide Symporter (NIS) in Metastatic Cancer Cells: A Novel Imaging Tool

Abstract

In most cancer patients, tumor metastasis to distant organs is the leading cause of death. Tumor cells dissociated from the primary site generally first encounter the lung, making it a significant site of tumor metastasis. We have generated a construct containing the cDNA for the rat sodium iodide symporter (NIS) and stably expressed it in mouse melanoma (B16F0) cells. Intravenous injection of these genetically‐modified B16F0 cells resulted in black tumor nodules throughout the lungs after 14–21 days. Hematoxylin and eosin staining showed numerous mitotic figures in these tumor nodules indicating cell proliferation. In addition, tumor cells were found surrounding capillaries suggesting both angiogenesis and possible routes for metastasis. High resolution in vivo imaging of cancer tumors in large opaque animals is extremely difficult. The high energy X‐rays produced by synchrotron light are capable of overcoming this obstacle and producing in vivo images of these metastatic tumors with much greater sensitivity. Thus, in this study we have developed a novel animal model using these modified tumor cells to accumulate iodine as a contrast agent for in vivo synchrotron imaging of metastatic lung cancer.