Morphological and biochemical analysis of the secretory pathway in melanoma cells with distinct metastatic potential

In this report, we have investigated whether alterations of the morphologic al and functional aspects of the biosecretory membrane system are associate d with the metastatic potential of tumor cells. To this end, we have analyz ed the morphology of the Golgi complex, the cytoskeleton organization and m embrane trafficking steps of the secretory pathway in two human melanoma A3 75 cell line variants with low (A375-P) and high metastatic (A375-MM) poten tial. Immunofluorescence analysis showed that in A375-P cells, the Golgi co mplex showed a collapsed morphology, Conversely, in A375-MM cells, the Golg i complex presented a reticular and extended morphology. At the ultrastruct ural level, the Golgi complex of A375-P cells was fragmented and cisternae were swollen. When the cytoskeleton was analyzed, the microtubular network appeared normal in both cell variants, whereas actin stress fibers were lar gely absent in A375-P, but not in A375-MM cells. In addition, the F-actin c ontent in A375-P cells was significantly lower than in A375-MM cells. These morphological differences in A375-P cells were accompanied by acceleration and an increase in the endoplasmic reticulum to Golgi and the trans-Golgi network to cell surface membrane transport, respectively. Our results indic ate that in human A375 melanoma cells, metastatic potential correlates with a well-structured morphofunctional organization of the Golgi complex and a ctin cytoskeleton, (C) 1999 Federation of European Biochemical Societies.