THE 72 KDA TYPE-IV COLLAGENASE IS MODULATED VIA DIFFERENTIAL EXPRESSION OF ALPHA-V-BETA-3-INTEGRIN AND ALPHA-5-BETA-1-INTEGRIN DURING HUMAN-MELANOMA CELL INVASION

We have recently reported that concomitant with an increase in invasiveness, there is an increase in the expression and secretion of the matrix-degrading 72 kDa gelatinase A/type IV collagenase (MMP-2) in a moderately invasive human melanoma cell line (A375M) upon perturbation of the alpha(v)beta3, classic vitronectin receptor. In the present study, we have extended these observations to include a highly invasive and metastatic melanoma cell line (C8161) which expresses a comparable amount of the alpha5beta1 integrin (classic fibronectin receptor), but very little alpha(v)beta3 integrin on its surface. When perturbed with an anti-alpha5beta1 antibody, C8161 cells are 89% more invasive in vitro, and express and secrete increased levels of the gelatinase A. These changes were not elicited using antibodies to the alpha(v)beta3 integrin. In addition, a 73% increase in invasion of C8161 cells through a fibronectin-enhanced matrix occurred, which could be abrogated by neutralizing antibodies to gelatinase A. Furthermore, we attempted to transiently mimic the invasive phenotype of the C8161 cells by diminishing the alpha(v)beta3 integrin from the A375M cell surface through fluorescence-activated cell sorting selection or deoxynojirimycin treatment, and found these cells to be 30-50% more invasive than the parental population. These data suggest that alternative modulation and signaling events could be involved in melanoma tumor cell invasion as a result of the differential expression of integrins, and strictly cataloging the presence of these integrins is but an initial step in the analysis of their functional activity.