Chapter 23, Problem 26
A study by Bose and colleagues [(1998). Blood 92:3362–3367] and a previous study by Biernaux and others [(1996). Bone Marrow Transplant 17:(Suppl. 3) S45–S47] showed that BCR-ABL fusion gene transcripts can be detected in 25 to 30 percent of healthy adults who do not develop chronic myelogenous leukemia (CML). Explain how these individuals can carry a fusion gene that is transcriptionally active and yet do not develop CML.
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As part of a cancer research project, you have discovered a gene that is mutated in many metastatic tumors. After determining the DNA sequence of this gene, you compare the sequence with those of other genes in the human genome sequence database. Your gene appears to code for an amino acid sequence that resembles sequences found in some serine proteases. Conjecture how your new gene might contribute to the development of highly invasive cancers.
Mutations in tumor-suppressor genes are associated with many types of cancers. In addition, epigenetic changes (such as DNA methylation) of tumor-suppressor genes are also associated with tumorigenesis [Otani et al. (2013). Expert Rev Mol Diagn 13:445–455].
Knowing that tumors release free DNA into certain surrounding body fluids through necrosis and apoptosis Kloten et al. [(2013). Breast Cancer Res. 15(1):R4] outline an experimental protocol for using human blood as a biomarker for cancer and as a method for monitoring the progression of cancer in an individual.
Mutations in tumor-suppressor genes are associated with many types of cancers. In addition, epigenetic changes (such as DNA methylation) of tumor-suppressor genes are also associated with tumorigenesis [Otani et al. (2013). Expert Rev Mol Diagn 13:445–455].
How might hypermethylation of the TP53 gene promoter influence tumorigenesis?
Those who inherit a mutant allele of the RB1 tumor-suppressor gene are at risk for developing a bone cancer called osteosarcoma. You suspect that in these cases, osteosarcoma requires a mutation in the second RB1 allele, and you have cultured some osteosarcoma cells and obtained a cDNA clone of a normal human RB1 gene. A colleague sends you a research paper revealing that a strain of cancer-prone mice develop malignant tumors when injected with osteosarcoma cells, and you obtain these mice. Using these three resources, what experiments would you perform to determine (a) whether osteosarcoma cells carry two RB1 mutations, (b) whether osteosarcoma cells produce any pRB protein, and (c) if the addition of a normal RB1 gene will change the cancer-causing potential of osteosarcoma cells?
What evidence indicates that mutations in human DNA mismatch repair genes are related to certain forms of cancer?
The table in this problem summarizes some of the data that have been collected on mutations in the BRCA1 tumor-suppressor gene in families with a high incidence of both early-onset breast cancer and ovarian cancer.
Predisposing Mutations in BRCA1
Kindred Codon Nucleotide Coding Effect Frequency in
Change Control
Chromosomes
1901 24 -11 bp Frameshift 0/180
or splice
2082 1313 C→T Gln→Stop 0/170
1910 1756 Extra C Frameshift 0/162
2099 1775 T→G Met→Arg 0/120
2035 NA* ? Loss of NA*
transcript _
Source: (1994). Science 266:66–71. © AAAS.
Note the coding effect of the mutation found in kindred group 2082. This results from a single base-pair substitution. Draw the normal double-stranded DNA sequence for this codon (with the 5' and 3' ends labeled), and show the sequence of events that generated this mutation, assuming that it resulted from an uncorrected mismatch event during DNA replication.