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Absence of WAF1 mutations in a variety of human malignancies
M Shiohara1, W S el-Deiry, M Wada
1Division of Hematology/Oncology, Cedars-Sinai Medical Center, UCLA School of Medicine 90048.
Abstract:
A newly cloned gene named wild-type p53-activated fragment 1 (WAF1; also known as p21, Pic-1, Cip-1, or SDI1) is directly regulated by p53 and can itself suppress tumor cell growth in culture. Induction of expression of WAF1 may be an important means by which cells with DNA injury arrest their growth to repair DNA or undergo apoptosis. Based on the hypothesis that mutations of this gene may play a role in carcinogenesis, we have studied 351 DNAs from 14 kinds of malignancies, as well as 36 human transformed cell lines, for alterations of WAF1 gene by single-strand conformation polymorphism analysis of polymerase chain reaction amplification of the DNA coding region of the WAF1 gene. No abnormal band shifts of WAF1 were noted in any of the samples or cell lines, but three major variants in exons 2 and 3 of the gene were found that are consistent with the existence of two different DNA polymorphisms. Sequence analysis of the amplified products producing these three variants in each exon from normal DNAs confirmed the presence of the polymorphisms in the WAF1 gene. Of 290 selected tumor samples previously evaluated for p53 mutations by single-strand conformation polymorphism, 90% had no detectable p53 alterations. In summary, mutations within the coding portion of the WAF1 gene were undetectable in a large series of human tumors, many of which had a normal p53 gene. This suggests that WAF1 alterations are generally caused indirectly, through p53 mutations rather than through intragenic mutation of the WAF1 itself.
Insights
Mutations in the WAF1 gene were not found in human tumors. Instead, alterations in WAF1 are likely caused by changes in the p53 gene, impacting cell growth and cancer development.
Area of Science:
- Molecular Biology
- Cancer Genetics
Background:
- The wild-type p53-activated fragment 1 (WAF1) gene, also known as p21, is regulated by p53 and can inhibit tumor cell growth.
- WAF1 induction is a key mechanism for cells with DNA damage to arrest growth for repair or undergo apoptosis.
Purpose of the Study:
- To investigate potential mutations in the WAF1 gene in various human malignancies and transformed cell lines.
- To determine if WAF1 gene alterations contribute to carcinogenesis.
Main Methods:
- Single-strand conformation polymorphism (SSCP) analysis of polymerase chain reaction (PCR) amplified WAF1 gene coding regions.
- Analysis of 351 tumor DNAs from 14 cancer types and 36 human transformed cell lines.
- Sequencing of amplified products to confirm DNA polymorphisms.
Main Results:
- No abnormal band shifts indicating mutations were detected in WAF1 across all tested samples.
- Three major variants were identified, consistent with two DNA polymorphisms in exons 2 and 3 of the WAF1 gene.
- In a subset of tumors previously analyzed for p53 mutations, 90% showed no p53 alterations.
Conclusions:
- Intragenic mutations within the coding region of the WAF1 gene are not a common cause of cancer.
- WAF1 alterations in cancer are likely a consequence of indirect mechanisms, primarily through mutations in the p53 gene, rather than direct WAF1 mutations.