Figure 1.

Laminin immunohistochemistry of developing melanoma A2058 spheroids (A) grown on laminin-containing Matrigel matrices (m) shows progressive development of internal patterned networks and small lumen-like spaces (region enclosed by the box is enlarged in B). Laminin also formed a mantle that enveloped the spheroids (arrows) and that appeared to associate with budding of minispheroids into the culture suspension (A, arrows). A2058 and A375 melanoma spheroids grown free in suspension also exhibited immunohistochemical laminin networks (C, arrows), unlike single adherent melanoma cells (D). RT-PCR of specific laminin α and β subunit chains confirmed that A2058 melanoma spheroid-forming cells expressed a different laminin subunit profile from A2058 melanoma adherent cells with increased expression of the α4 and β1 chains (E). In situ hybridization for the laminin α4 chain mRNA on A2058 melanoma spheroids confirms this finding (F, arrows indicate laminin expression). Asterisks indicate a greater than twofold increase in expression. Original magnification: ×400 (A and F); ×1600 (B, C, and D).