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Somatic mutation during metastasis of a mouse fibrosarcoma line detected by DNA fingerprint analysis
T Takada1, S Suzuki, Y Sugawara
1First Department of Biochemistry, Niigata University School of Medicine.
Abstract:
Metastatic nodules were examined by DNA fingerprint analysis. The probes used, Pc-1 and Pc-2, detect mutations as shifts in bands of the minisatellite loci which are dispersed among chromosomes. Four clonal lines of a fibrosarcoma from an F1 mouse (C57BL/Ka x C3H/He) were selected for various metastatic potentials upon inoculation into syngeneic mice. These four lines exhibited many extra bands resulting from recombination and/or DNA slippage, indicating accumulation of mutations during the successive passages in mice. One of the four, a 505 cell line which had been passaged extensively in vitro and consisted of a heterogenous population, was inoculated into thirteen syngeneic mice, and gave rise to six lung metastatic nodules in two mice. All the nodules showed band-patterns distinct from one another, although nodules within a given mouse tended to show similar patterns. When a genetically tagged 505-05-01 clone was analyzed, three of nine metastatic nodules obtained also revealed new bands. These results strongly suggest that somatic mutations occur at a high frequency during metastasis, providing direct evidence of genetic instability of the tumor cells.
Insights
Tumor cells accumulate mutations during metastasis, as shown by DNA fingerprint analysis of fibrosarcoma nodules. This genetic instability provides direct evidence of high-frequency somatic mutations during the metastatic process.
Area of Science:
- Oncology
- Genetics
- Molecular Biology
Background:
- Metastasis involves complex cellular changes.
- Understanding the genetic alterations during metastasis is crucial for cancer research.
Purpose of the Study:
- To investigate the frequency and nature of genetic mutations during tumor metastasis.
- To provide direct evidence of genetic instability in metastatic tumor cells.
Main Methods:
- DNA fingerprint analysis using Pc-1 and Pc-2 probes to detect mutations in minisatellite loci.
- Selection and in vivo passage of fibrosarcoma clonal lines with varying metastatic potentials.
- Analysis of metastatic nodules derived from inoculated tumor cell lines.
Main Results:
- Fibrosarcoma clonal lines showed increased mutations (extra bands) after successive passages.
- Metastatic nodules exhibited distinct DNA band patterns, indicating genetic heterogeneity.
- A genetically tagged clone also revealed new bands in metastatic nodules, confirming ongoing mutation.
Conclusions:
- Somatic mutations occur at a high frequency during the metastatic process.
- Tumor cells display significant genetic instability during metastasis.
- DNA fingerprinting is a valuable tool for studying genetic changes in cancer progression.