Decrease in tumor-cell attachment and in a 140-kDa fibronectin receptor correlate with greater expression of multiple...

Area of Science:

• Cell Biology
• Biochemistry
• Biophysics

Background:

• B16 melanoma cell adhesion is crucial for understanding tumor metastasis.
• Cell attachment is influenced by extracellular matrix proteins like fibronectin and surface properties.
• Previous studies indicate B16 cells exhibit differential adhesion based on substrate and fibronectin availability.

Purpose of the Study:

• To investigate general adhesion-related alterations in flattened versus poorly attached B16 melanoma cells.
• To identify specific protein changes associated with decreased cell substratum attachment.
• To explore the potential role of novel proteins in cell rounding and adhesion modulation.

Main Methods:

• Immune blotting of cell extracts to detect specific protein components.
• Surface iodination to assess external protein exposure.
• Metabolic labeling (35S-methionine) of cell aggregates.
• Analysis of matrix-associated components.

Main Results:

• Flattened cells showed a 140-kDa component, while rounded cells had increased 54-kDa species.
• Poorly adhering cells exhibited decreased external exposure of a 140-kDa fibronectin-binding protein.
• Poorly adhering cells showed increased labeling of multiple 34-kDa proteins via iodination.
• Cell aggregates on collagen gels revealed decreased 140-kDa and increased 54-kDa components compared to cells on fibronectin.

Conclusions:

• Two novel proteins, a 34-kDa species and a 54-kDa species, are identified in poorly adhering B16 melanoma cells.
• The 34-kDa protein increase is primarily detected on the cell surface, while the 54-kDa protein is associated with detergent-insoluble matrices.
• These proteins may play a role in cell rounding through transmembrane modulation involving surface membrane and cytoskeletal structures.