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Electrophoretic heterogeneity of pigmented hamster melanoma cells
1Jagiellonian University, Institute of Molecular Biology, Kraków, Poland.
Abstract:
Pigmented hamster melanoma tumors growing in situ contain two subpopulations of melanoma cells that have different electrophoretic mobilities (EPM). A mild neuraminidase treatment, which removes sialic acid residues from the cell surface glycoproteins, reduces the EPM of both groups of melanoma cells yielding an electrophoretically uniform population. This shows that the differences in the EPM between the subpopulations of pigmented melanoma cells stem from the different content of sialic acid residues on the cell surface. The relationship between the different EPM melanoma cell subpopulations was, therefore, examined during tumor growth, development, and formation of metastases. The relative content of cells having high electrophoretic mobility, the "fast moving" cells, increases as the tumors grow larger. However, tumors of the same diameter contain nearly the same fraction of "fast moving" cells despite their age. The proportion of the "fast moving" cells is significantly higher in the central part than in the outermost layer of pigmented melanoma tumors. These data suggest that the development of "fast moving" cells is promoted by some size-dependent changes in the intratumor environment. In vivo selection of melanoma cells for their ability to colonize lungs renders tumors that reveal elevated metastatic potential and contain a significantly higher fraction of cells possessing high electrophoretic mobility than the parent tumor. Moreover, the metastatic nodules contain a remarkably elevated fraction of the "fast moving" cells. The reported correlation between the "fast moving" cell fraction and the metastatic potential suggests that the relative content of cells having high electrophoretic mobility may determine the metastaticity of pigmented hamster melanoma.
Insights
Pigmented hamster melanoma tumors exhibit two cell subpopulations with distinct electrophoretic mobilities (EPM), differing in sialic acid content. The proportion of high-mobility cells correlates with tumor size and metastatic potential.
Area of Science:
- Oncology
- Cell Biology
- Biochemistry
Background:
- Pigmented hamster melanoma tumors present distinct cell subpopulations.
- Electrophoretic mobility (EPM) differences are attributed to cell surface sialic acid content.
Purpose of the Study:
- To investigate the relationship between melanoma cell subpopulations with varying EPM.
- To examine the role of these subpopulations in tumor growth, development, and metastasis.
Main Methods:
- Neuraminidase treatment to alter cell surface sialic acid.
- Analysis of electrophoretic mobility (EPM) of melanoma cell subpopulations.
- Correlation of EPM cell fraction with tumor size, location, and metastatic potential.
Main Results:
- Neuraminidase treatment equalizes EPM, confirming sialic acid as the basis for mobility differences.
- The fraction of high-mobility ('fast moving') cells increases with tumor size.
- High-mobility cells are more prevalent in central tumor regions and metastatic nodules.
- Tumor metastatic potential correlates positively with the proportion of high-mobility cells.
Conclusions:
- Melanoma cell subpopulations with differing sialic acid content contribute to tumor heterogeneity.
- Tumor microenvironment, potentially influenced by size, promotes the development of high-mobility cells.
- The fraction of high-mobility cells is a potential indicator of melanoma metastaticity.