Comparison of the expression profile of metastasis-associated genes between primary and circulating cancer cells in oral squamous cell carcinoma.

Tumor metastasis is a complex process involving several distinct steps such as escape from a primary tumor, dissemination through the circulation, lodgment in small vessels at distinct sites, penetration of the vessel wall and growth in the new site as a secondary tumor. To compare the expression profile of metastasis-associated genes between circulating cancer cells in peripheral blood and cells in the primary lesion of oral squamous cell carcinoma (OSCC), we employed a combination analysis of laser captured microdissection (LCM) and immunomagnetic separation (IMS) techniques for capturing primary and circulating cancer cells, respectively. Total RNAs were then extracted from each cell and mRNA expression of CK19, matrix metalloproteinases (MMP-1, -2, -7, -9) and CD44, including its variant forms (CD44s, v6, v9), were analyzed by RT-PCR. Although CD44 including its variant forms were expressed in 20%(CD44s) to 30%(v6, v9) of the primary lesion, 40%(v6) to 90%(CD44s) of blood samples were CD44-positive. Furthermore, MMPs were expressed in 30%(MMP-1, -2) to 60%(MMP-7) of primary samples, whereas most blood samples were negative for the expression of MMPs. These results suggested that circulating cancer cells might express different characteristics after being released from the primary lesion.