From Isolated Tumour Cells to Overt Lymph Node Metastases: Biological and Imaging Studies on the Development of Experimental Lymph Node Metastases

Metastatic colonization and establishment of overt lymph node (LN) tumours indicates poor prognosis for cancer patients. However, the basic biology that influences the development of LN metastasis is poorly understood due to the lack of basic animal models. The following work provides a new lymph node experimental metastasis assay (LEMA) that permits the assessment of tumour cell fate after they arrest in draining LNs. In using this new model, we discovered that only 8% of the tumour cells that arrive in the LN are successful in forming overt tumours. This work also explored the use of imaging approaches to monitor the process on LN metastasis in mice. To study the in vivo growth of LN metastases, we used 3-dimensional high frequency ultrasound (HFUS). We observed that growth rates of LN tumours varied from mouse to mouse. Furthermore, HFUS allowed us to visualize small metastatic deposits and micrometastases and their growth over time. In order to provide some ground work for the development of magnetic resonance imaging (MRI) of lymph node metastases, we developed a gel phantom that simulated the metastatic colonization of LNs. By labeling cells with gadofluorine M (GdF, a positive contrast agent), we were able to demonstrate how MRI (3 Tesla) was able to quantitatively measure the abundance of GdF-labeled tumour cells. The research described herein will expedite future research by providing a new experimental lymph node metastasis assay and novel imaging techniques that will permit the study of metastasis development in the lymph node