IN-VITRO INVASION OF SMALL-CELL LUNG-CANCER CELL-LINES CORRELATES WITH EXPRESSION OF EPIDERMAL GROWTH-FACTOR RECEPTOR

Formation of metastasis is a multistep process involving attachment to the basement membrane, local proteolysis and migration into surroundi ng tissues, lymph or bloodstream. In the present study, we have analys ed the correlation between in vitro invasion and presence of the epide rmal growth factor receptor (EGFR) in a panel of 21 small-cell lung ca ncer (SCLC) cell lines. We have previously reported that ten of these cell lines expressed EGFR protein detected by radioreceptor and affini ty labelling assays. In 11 small-cell lung cancer (SCLC) cell lines, E GFR mRNA was detected by Northern blot analysis. In vitro invasion in a Boyden chamber assay was found in all EGFR-positive cell lines, wher eas no invasion was detected in the EGFR-negative cell lines. Quantifi cation of the in vitro invasion in 12 selected SCLC cell lines demonst rated that, in the EGFR-positive cell lines, between 5% and 16% of the cells added to the upper chamber were able to traverse the Matrigel m embrane. Expression of several matrix metalloproteases (MMP), of tissu e inhibitor of MMP (TIMP) and of cathepsin B was evaluated by immunopr ecipitation, Western blot analysis and reverse transcriptase polymeras e chain reaction (RI-PCR). However, in vitro invasive SCLC cell lines could not be distinguished from non-invasive cell lines based on the e xpression pattern of these molecules, In six SCLC cell lines, in vitro invasion was also determined in the presence of the EGFR-neutralizing monoclonal antibody mAb528, The addition of this antibody resulted in a significant reduction of the in vitro invasion in three selected EG FR-positive cell lines, Our results show that only EGFR-positive SCLC cell lines had the in vitro invasive phenotype, and it is therefore su ggested that the EGFR might play an important role for the invasion po tential of SCLC cell lines.