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The fruit fly Drosophila and the fish Xiphophorus as model systems for cancer studies
1Department of Development Genetics, Deutsches Krebsforschungszentrum, (German Cancer Research Center), Heidelberg.
Abstract:
Genetic and molecular analyses of Drosophila have shown that tumorigenesis may arise from inactivation of single genes controlling cell growth and differentiation. Recessive mutations in a series of genes interrupt the differentiation of primordial cells and result in overgrowth, producing either hyperplasia or neoplasia. In mutant animals tumours form in either the optic centres of the larval brain, the imaginal discs or the haemopoietic organs. In Drosophila 17 genetic loci giving rise to neoplasia and six loci producing hyperplasia have been identified. The lethal(2)giant larvae gene constitutes the prototype of these genes. Its molecular cloning and analysis have demonstrated that the tumor phenotype results from a lack of gene function. Furthermore, tumour prevention was achieved by introducing a normal copy of l(2)gl into the genome of l(2)gl- deficient animals, showing that the l(2)gl gene behaves as a tumour suppressor or anti-oncogene. Melanomas of genetic origin develop in interspecies hybrids of the fish Xiphophorus. The melanoma appears when a sex linked chromosomal gene (Tu) is present among the progeny animals lacking an autosomal locus Differentiation, which acts as a tumour suppressor gene. A sequence homologous to the erb-B gene can be associated to the sex chromosomal Tu locus. This gene encodes a receptor tyrosine kinase related to the EGF-receptor, and its activation and overexpression are thought to play a critical part in melanoma formation.
Insights
Tumor suppressor genes, like lethal(2)giant larvae in Drosophila, prevent overgrowth when mutated. Restoring gene function halts tumor development, highlighting their critical role in cell growth regulation.
Area of Science:
- Genetics
- Molecular Biology
- Developmental Biology
Background:
- Tumorigenesis can result from mutations in genes controlling cell growth and differentiation.
- In Drosophila, mutations in specific genes lead to hyperplasia or neoplasia in various tissues.
- Genetic models like Drosophila and Xiphophorus fish offer insights into cancer development.
Purpose of the Study:
- To investigate the genetic and molecular basis of tumorigenesis.
- To identify and characterize tumor suppressor genes.
- To understand the mechanisms of tumor formation and prevention.
Main Methods:
- Genetic and molecular analyses in Drosophila.
- Identification of genetic loci associated with hyperplasia and neoplasia.
- Gene cloning and functional analysis of the lethal(2)giant larvae gene.
- Analysis of genetic melanoma in Xiphophorus fish hybrids.
Main Results:
- 17 loci for neoplasia and 6 for hyperplasia identified in Drosophila.
- The lethal(2)giant larvae (l(2)gl) gene functions as a tumor suppressor.
- Tumor prevention achieved by reintroducing a functional l(2)gl gene.
- A sex-linked gene (Tu) and a homologous sequence to erb-B are associated with melanoma in Xiphophorus.
Conclusions:
- Inactivation of single genes can initiate tumorigenesis.
- Tumor suppressor genes play a crucial role in preventing uncontrolled cell proliferation.
- The l(2)gl gene in Drosophila and the Differentiation locus in Xiphophorus act as tumor suppressors.
- Aberrant receptor tyrosine kinase signaling, potentially via erb-B, contributes to melanoma formation.