Related Experiment Videos
The raf oncogene is associated with a radiation-resistant human laryngeal cancer
Abstract:
In order to identify the genetic factors associated with the radiation-resistant human laryngeal carcinoma cell line (SQ-20B), tumor cell DNA was transfected into NIH/3T3 cells. A high incidence (six out of six) of raf sequences was found in transfected NIH/3T3 clones and the tumorigenic potential of SQ-20B DNA could be linked to genomic fragments that represent most of the kinase domain of human c-raf-1. An apparently unaltered 3.5-kilobase pair (kb) human c-raf transcript was identified in SQ-20B cells but was not observed in the transfected NIH/3T3 cell clones. Two new transcripts (4.2 kb and 2.6 kb) were found in tumorigenic clones; the large transcript was missing in a very poorly tumorigenic clone. Cytogenetic analysis indicated that the normal autosomes of chromosome 3 were absent in SQ-20B karyotypes and had formed apparently stable marker chromosomes. Unlike the recipient NIH/3T3 cell line, 30 percent of the transformed clone-1 metaphases had minute and double-minute chromosomes representative of amplified DNA sequences. The frequency of the c-raf-1 identification by NIH/3T3 transfection of SQ-20B DNA suggests the presence of some genetic abnormality within this locus.
Insights
Genetic abnormalities in radiation-resistant laryngeal cancer cells (SQ-20B) were identified using NIH/3T3 transfection. The human c-raf-1 gene, particularly its kinase domain, was strongly implicated in the tumor
Area of Science:
- Molecular Biology
- Genetics
- Oncology
Background:
- Human laryngeal carcinoma cell line SQ-20B exhibits radiation resistance.
- Identifying genetic factors contributing to radioresistance is crucial for cancer treatment.
Purpose of the Study:
- To identify genetic factors responsible for the radiation resistance of the SQ-20B human laryngeal carcinoma cell line.
- To investigate the role of the c-raf-1 gene in tumorigenesis and radioresistance.
Main Methods:
- Transfection of tumor cell DNA into NIH/3T3 cells.
- Analysis of raf sequences in transfected clones.
- Identification and characterization of c-raf transcripts.
- Cytogenetic analysis of SQ-20B cells and transformed clones.
Main Results:
- High incidence of raf sequences in transfected NIH/3T3 clones, linking tumorigenic potential to human c-raf-1 kinase domain fragments.
- Identification of a 3.5 kb c-raf transcript in SQ-20B cells, with new 4.2 kb and 2.6 kb transcripts in tumorigenic clones.
- Cytogenetic analysis revealed absence of normal chromosome 3 autosomes in SQ-20B cells and the presence of minute and double-minute chromosomes in transformed clones, indicating DNA amplification.
Conclusions:
- The genetic abnormality within the c-raf-1 locus is strongly suggested by its frequent identification via NIH/3T3 transfection of SQ-20B DNA.
- The findings implicate alterations in c-raf-1 and chromosome 3 in the radiation resistance and tumorigenic potential of laryngeal carcinoma.
- Further investigation into these genetic aberrations may reveal therapeutic targets for overcoming radioresistance in laryngeal cancer.