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Rho GTPases are over-expressed in human tumors
1Institute of Toxicology, Division of Applied Toxicology, University of Mainz, Germany. fritz@mail.uni-mainz.de
Abstract:
Small GTPases of the Rho family are involved in the regulation of a variety of cellular processes, such as the organization of the microfilamental network, cell-cell contact and malignant transformation. To address the question of whether Rho proteins are involved in carcinogenesis in man, we compared their expression in tumors from colon, breast and lung with that of the corresponding normal tissue originating from the same patient. As shown by Rho-specific 32P-ADP-ribosylation, as well as Western-blot analysis, the amount of RhoA protein was largely increased in all 3 types of tumors tested. The most dramatic differences in the expression of Rho GTPases were observed in breast tissue. All breast tumors analyzed showed high levels of RhoA, Rac and Cdc42 proteins, whereas in the corresponding normal tissue these Rho proteins were hardly or not detectable. Progression of breast tumors from WHO grade I to grade III was accompanied by a significant average increase in RhoA protein. Overall, increase in the amount of Rho GTPases, in particular RhoA, appears to be a frequent event in different types of human tumors. This supports the view that Rho GTPases are involved in human carcinogenesis.
Insights
Small GTPases, including RhoA, are frequently increased in human tumors. This suggests these proteins play a role in the development of cancers like breast, colon, and lung cancer.
Area of Science:
- Molecular Biology
- Oncology
- Cell Biology
Background:
- Small GTPases of the Rho family regulate crucial cellular functions, including cytoskeletal organization, cell adhesion, and malignant transformation.
- Their precise role in human carcinogenesis remains to be fully elucidated.
Purpose of the Study:
- To investigate the involvement of Rho proteins in human carcinogenesis.
- To compare Rho GTPase expression in various human tumors versus normal adjacent tissues.
Main Methods:
- Rho-specific 32P-ADP-ribosylation assays.
- Western-blot analysis to quantify Rho protein levels.
- Comparison of protein expression in tumor and normal tissues from the same patient.
Main Results:
- RhoA protein levels were significantly elevated in colon, breast, and lung tumors compared to normal tissues.
- Breast tumors exhibited the most pronounced differences, with high levels of RhoA, Rac, and Cdc42, which were barely detectable in normal breast tissue.
- A positive correlation was observed between the progression of breast tumors (WHO grade I to III) and increased RhoA protein levels.
Conclusions:
- Increased expression of Rho GTPases, particularly RhoA, is a common event in diverse human tumors.
- These findings support the hypothesis that Rho GTPases are implicated in the process of human carcinogenesis.