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Role of disrupted gap junctional intercellular communication in detection and characterization of carcinogens
1Unit of Multistage Carcinogenesis, International Agency for Research on Cancer, Lyon, France.
Abstract:
Results from short-term tests for carcinogens and our advanced knowledge on cellular and molecular mechanisms of carcinogenesis strongly suggest that carcinogens do not induce genetic changes necessarily by directly interacting with DNA. Therefore, it is not surprising to see that many carcinogens are not detectable by available genetic toxicology tests. Thus, it has become necessary to study nongenotoxic mechanisms of carcinogenesis and to provide methods to predict those carcinogens which escape from conventional mutation tests. One possible nongenotoxic mechanism of carcinogenesis which is supported by abundant experimental evidence is inhibition of gap junctional intercellular communication. Many, but not all, tumor-promoting agents have been shown to inhibit the communication of cultured cells as well as in vivo. Molecular mechanisms of gap junctional intercellular communication control revealed that connexin (gap junction) genes form a family of tumor suppressor genes. Control mechanisms of expression as well as function of connexins are vulnerable to various carcinogenic insults, notably to nongenetoxic carcinogens. Thus, studies on the role of connexins in cell growth and carcinogenesis may prove to be useful for establishing a mechanism-based test to detect certain types of nongenotoxic carcinogens.
Insights
Many carcinogens evade genetic toxicology tests by not directly damaging DNA. This study explores the role of gap junction communication and connexins in nongenotoxic carcinogenesis, suggesting new detection methods.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- Carcinogens may cause cancer through non-DNA-damaging mechanisms, evading standard genetic toxicology tests.
- Inhibition of gap junctional intercellular communication is a recognized nongenotoxic mechanism implicated in tumor promotion.
- Connexin genes, crucial for cell communication, function as tumor suppressors and are vulnerable to carcinogenic insults.
Purpose of the Study:
- To investigate the role of nongenotoxic mechanisms in carcinogenesis, specifically focusing on gap junctional intercellular communication.
- To explore the involvement of connexins in cell growth and their potential as biomarkers for nongenotoxic carcinogens.
- To develop mechanism-based tests for detecting carcinogens that escape conventional mutation assays.
Main Methods:
- Review of experimental evidence on the inhibition of gap junctional intercellular communication by tumor promoters.
- Analysis of molecular mechanisms controlling connexin gene expression and function.
- Evaluation of connexins' role in cell growth regulation and carcinogenesis.
Main Results:
- Many tumor promoters inhibit gap junctional intercellular communication in cellular and in vivo models.
- Connexins are identified as a family of tumor suppressor genes, with their regulation being susceptible to carcinogenic agents.
- Disruption of connexin function is linked to uncontrolled cell growth and cancer development.
Conclusions:
- Nongenotoxic mechanisms, such as the inhibition of gap junctional intercellular communication, are critical in carcinogenesis.
- Connexins play a vital role in preventing cancer, and their dysfunction is a hallmark of certain carcinogenic processes.
- Studying connexins offers a promising avenue for developing novel assays to identify specific types of nongenotoxic carcinogens.