Molecular and cytogenetic studies strongly implicate the plasticity of the cancer cell genome in malignant progression. Gene amplification is one prominent example of this genetic flexibility which is peculiar to malignant cells. The overexpression of proto oncogenes mediated by gene amplification has now been described in a variety of tumors of human and rodent origin, and in some cases it has been shown how such overproduction can engender increased invasiveness, ability to evade immune surveillance, etc. In addition, there is now ample documentation in human tumors in vivo that gene amplification can lead to resistance to a variety of antineoplastic agents alone, or in combination. Therefore, understanding the mechanisms of gene amplification could lead to a better understanding of how the control mechanisms which insure genetic stability in normal cells are abrogated in cancer cells, and the types of conditions which favor the occurrence of the amplification process. Such information could lead to new strategies of drug delivery to avoid development of resistance by this mechanism. This proposal presents experiments to investigate the nature of the earliest molecular products produced by gene amplification. Specifically, it will be tested whether submicroscopic, autonomously replicating circular elements are commonly generated as a first step. This hypothesis is formulated on the basis of previous work from this laboratory which demonstrated that such elements can be precursors of minute chromosomes. The structure of such elements will be analyzed using physical and molecular cloning methods designed to study genetic regions spanning hundreds of kilobases, and the hypothesis that such elements comprise functional replication domains will be tested. A replication origin present in one such element described previously in this lab will be isolated and analyzed in order to deduce how its structure contributes to regulated replication. Finally, a gene transfer method is proposed for identifying regions of the human genome associated with the capacity for high frequency gene amplication. By analogy with previous results from this lab, this approach could enable isolation of a human replication origin for further molecular characterization.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM027754-12
Application #
3275011
Study Section
Molecular Cytology Study Section (CTY)
Project Start
1980-04-01
Project End
1993-03-31
Budget Start
1991-04-01
Budget End
1992-03-31
Support Year
12
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Salk Institute for Biological Studies
Department
Type
DUNS #
005436803
City
La Jolla
State
CA
Country
United States
Zip Code
92037
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Carroll, S M; Trotter, J; Wahl, G M (1991) Replication timing control can be maintained in extrachromosomally amplified genes. Mol Cell Biol 11:4779-85
Ruiz, J C; Wahl, G M (1990) Chromosomal destabilization during gene amplification. Mol Cell Biol 10:3056-66
Wahl, G M (1989) The importance of circular DNA in mammalian gene amplification. Cancer Res 49:1333-40
Ruiz, J C; Choi, K H; von Hoff, D D et al. (1989) Autonomously replicating episomes contain mdr1 genes in a multidrug-resistant human cell line. Mol Cell Biol 9:109-15
Ruiz, J C; Wahl, G M (1988) Formation of an inverted duplication can be an initial step in gene amplification. Mol Cell Biol 8:4302-13

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