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Decrease in gamma-actin expression, disruption of actin microfilaments and alterations in cell adhesion systems
H Suzuki1, H Nagata, Y Shimada
1Department of Otorhinolaryngology, Chiba University School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba, 260, Japan.
Abstract:
In order to clarify how cytoskeletons and adhesion systems change through acquisition of metastatic capacity in a cancer cell, we examined the expressions of beta- and gamma-actin, the morphology of actin microfilaments and focal contacts, and also the expression of vinculin in a salivary gland adenocarcinoma cell clone cl-1, which acquired metastatic capacity, in comparison with its original clone HSGc lacking metastatic ability. Two-dimensional gel electrophoresis of Triton-insoluble fractions and combined Western blot analysis by immunostaining with anti actin-isoform antibodies showed that the expression of gamma-actin was somewhat lower than that of beta-actin in HSGc, and cl-1 expressed a comparable amount of beta-actin to HSGc, whereas gamma-actin expression by cl-1 was far less than that by HSGc. Northern blot analysis demonstrated that there was little difference in the level of beta-actin mRNA between HSGc and cl-1, while the level of gamma-actin was markedly decreased in cl-1 as compared with HSGc. In terms of morphology, cl-1 cells showed disruption of actin microfilaments and a decrease in the size and number of focal contacts on the cell surface. Furthermore, cl-1 showed decreased expression of vinculin, which became obscured even at the end of actin microfilaments. These results demonstrated that a decrease in gamma-actin, disruption of actin microfilaments, and suppression of focal contacts as well as vinculin take place in the transformation from a non-metastatic condition to a metastatic one in the human salivary gland adenocarcinoma cell clones. Thus, it was strongly suggested that these changes contribute to a decrease in cell adhesiveness and an increase in cell motility, which is probably a major cause for acquisition of metastatic potential.
Insights
Metastatic cancer cells show decreased gamma-actin expression and disrupted actin microfilaments. These changes in cytoskeleton and cell adhesion molecules like vinculin contribute to increased cell motility and metastatic potential.
Area of Science:
- Cell Biology
- Cancer Research
- Molecular Biology
Background:
- Cancer cell metastasis involves complex changes in cellular structure and adhesion.
- Understanding the molecular basis of metastasis is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate alterations in cytoskeletal proteins and adhesion molecules during the acquisition of metastatic capacity.
- To compare actin isoform expression, actin microfilament organization, and focal contact dynamics between metastatic and non-metastatic cancer cells.
Main Methods:
- Comparative analysis of beta- and gamma-actin expression using two-dimensional gel electrophoresis and Western blot.
- Assessment of actin microfilament morphology and focal contacts via microscopy.
- Evaluation of vinculin expression in metastatic and non-metastatic cell lines.
Main Results:
- Metastatic cells (cl-1) exhibited significantly reduced gamma-actin expression compared to non-metastatic cells (HSGc), with similar beta-actin levels.
- Northern blot analysis confirmed a marked decrease in gamma-actin mRNA in metastatic cells.
- Morphological changes included disrupted actin microfilaments, reduced focal contacts, and decreased vinculin expression in metastatic cells.
Conclusions:
- Acquisition of metastatic capacity in salivary gland adenocarcinoma is associated with decreased gamma-actin and impaired actin-based structures.
- Suppression of focal contacts and vinculin contributes to reduced cell adhesion and increased motility.
- These cytoskeletal and adhesion changes are key factors in the development of metastatic potential.