OBJECTIVETo study the metastasis-associated molecules differentially expressed in highly and poorly metastatic sublines and the mechanism of metastasis in lung giant cell carcinoma.

METHODSHighly and poorly metastatic sublines (PLA801D and PLA801C)were used as metastasis model. Cell motility and invasion assay in vitro were first compared between the two sublines. Then, gelatin zymography analysis was used to determine the MMP-2 and MMP-9 activity. The protein expression level of secreted MMP-2, MMP-9, TIMP-1, TIMP-2 and intracellular expression level of p53, p16, PCNA, CD44(V6) isomeride, E-cadherin, CK18, nm23-H1 as well as the mRNA expression level of MMP-2, MMP-9, TIMP-1, TIMP-2, VEGF were compared through Western blot. Semi-quantitative RT-PCR analysis was used to determine the intracellular mRNA expression of MMP-2, MMP-9, TIMP-1, TIMP-2 and VEGF.

RESULTSThe in vitro cell invasion potential of highly metastatic subline PLA801D was significantly higher than that of poorly metastatic subline PLA801C by about 4 folds, while the cell motility potential was similar. The secreted MMP-2 activity was notably higher in PLA801D, which was initiated by the higher expression of MMP-2 at protein and mRNA level. In addition, the expression level of p53, PCNA, CK18 protein and VEGF mRNA were significantly higher, while the expression level of p16, E-cadherin and nm23-H1 protein were significantly lower in PLA801D. Some molecules such as MMP-9, TIMP-1, TIMP-2, CD44(V6) isomeride, which had been reported to be associated with tumor metastasis, were not observed to change significantly between the two sublines.

CONCLUSIONThere are significant differences in metastatic potential and phenotypes between highly and poorly metastatic sublines of lung giant cell carcinoma. Some differentially expressed molecules might be playing roles in promoting or inhibiting metastasis of lung giant cell carcinoma, which may be useful to elucidate the mechanism of metastasis.