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Expression of full-length p53 and its isoform Deltap53 in breast carcinomas in relation to mutation status and clinical parameters.

Baumbusch LO, Myhre S, Langerød A, Bergamaschi A, Geisler SB, Lønning PE, Deppert W, Dornreiter I, Børresen-Dale AL - Mol. Cancer (2006)

Bottom Line: Patients expressing mutated full-length p53 and non-mutated (wild-type) Deltap53, "mutational hybrids", showed a slightly higher frequency of patients with distant metastasis at time of diagnosis compared to other patients with p53 mutations, but otherwise did not differ significantly in any other clinical parameter.Expression of p53 is accompanied by the functionally different isoform Deltap53 at the mRNA level in cell lines and human breast tumors.Investigations of "mutational hybrid" patients highlighted that wild-type Deltap53 does not compensates for mutated p53, but rather may be associated with a worse prognosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Genetics, Institute for Cancer Research, Rikshospitalet-Radiumhospitalet Medical Center, 0310 Oslo, Norway. lars.baumbusch@medisin.uio.no

ABSTRACT

Background: The tumor suppressor gene p53 (TP53) controls numerous signaling pathways and is frequently mutated in human cancers. Novel p53 isoforms suggest alternative splicing as a regulatory feature of p53 activity.

Results: In this study we have analyzed mRNA expression of both wild-type and mutated p53 and its respective Deltap53 isoform in 88 tumor samples from breast cancer in relation to clinical parameters and molecular subgroups. Three-dimensional structure differences for the novel internally deleted p53 isoform Deltap53 have been predicted. We confirmed the expression of Deltap53 mRNA in tumors using quantitative real-time PCR technique. The mRNA expression levels of the two isoforms were strongly correlated in both wild-type and p53-mutated tumors, with the level of the Deltap53 isoform being approximately 1/3 of that of the full-length p53 mRNA. Patients expressing mutated full-length p53 and non-mutated (wild-type) Deltap53, "mutational hybrids", showed a slightly higher frequency of patients with distant metastasis at time of diagnosis compared to other patients with p53 mutations, but otherwise did not differ significantly in any other clinical parameter. Interestingly, the p53 wild-type tumors showed a wide range of mRNA expression of both p53 isoforms. Tumors with mRNA expression levels in the upper or lower quartile were significantly associated with grade and molecular subtypes. In tumors with missense or in frame mutations the mRNA expression levels of both isoforms were significantly elevated, and in tumors with nonsense, frame shift or splice mutations the mRNA levels were significantly reduced compared to those expressing wild-type p53.

Conclusion: Expression of p53 is accompanied by the functionally different isoform Deltap53 at the mRNA level in cell lines and human breast tumors. Investigations of "mutational hybrid" patients highlighted that wild-type Deltap53 does not compensates for mutated p53, but rather may be associated with a worse prognosis. In tumors, both isoforms show strong correlations in different mutation-dependent mRNA expression patterns.

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Correlation between mRNA expression level of full-length p53 versus Δp53 in breast carcinomas with various p53 mutations. p53 and Δp53 mRNA expression levels of mutated p53 in human breast tumors are shown with p53 relative mRNA expression in a.u. (arbitrary units) on x-axis and Δp53 on y-axis. Different mutation types are indicated by various symbols. "Mutational hybrids", mutations represented on full-length p53, but removed in Δp53, are marked with open symbols. Mutations present in both isoforms are specified with filled symbols. The shape of the symbols indicate the various mutation types: ■, □ missense mutations, ◊ in frame mutations, ▲, Δ nonsense mutations, * frame shift mutations, ● splice mutations, - mutations in the splice cassette (the two samples full-filling this criteria are highlighted with their sample ID). Horizontal lines show borders between the median values of the relative mRNA expression subgroups: MII vs Wt vs MI. The regression line for missense mutations is drawn with an equation y = 1.03x - 0.12 and a regression coefficient of 0.89. (1 low p53 value in this sample might be due to mutation in p53 primer binding site, 2 low Δp53 value in this sample might be due to mutation in Δp53 primer binding site – for details see Additional file 2).
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Figure 6: Correlation between mRNA expression level of full-length p53 versus Δp53 in breast carcinomas with various p53 mutations. p53 and Δp53 mRNA expression levels of mutated p53 in human breast tumors are shown with p53 relative mRNA expression in a.u. (arbitrary units) on x-axis and Δp53 on y-axis. Different mutation types are indicated by various symbols. "Mutational hybrids", mutations represented on full-length p53, but removed in Δp53, are marked with open symbols. Mutations present in both isoforms are specified with filled symbols. The shape of the symbols indicate the various mutation types: ■, □ missense mutations, ◊ in frame mutations, ▲, Δ nonsense mutations, * frame shift mutations, ● splice mutations, - mutations in the splice cassette (the two samples full-filling this criteria are highlighted with their sample ID). Horizontal lines show borders between the median values of the relative mRNA expression subgroups: MII vs Wt vs MI. The regression line for missense mutations is drawn with an equation y = 1.03x - 0.12 and a regression coefficient of 0.89. (1 low p53 value in this sample might be due to mutation in p53 primer binding site, 2 low Δp53 value in this sample might be due to mutation in Δp53 primer binding site – for details see Additional file 2).

Mentions: Comparison of the mRNA levels of the two isoforms p53 and Δp53 in 88 tumors samples revealed a high correlation in both mutated and non-mutated tumors with a correlation coefficient of r2 = 0.86 for wild-type and r2 = 0.85 for mutant tumors, respectively (Figure 5A and 5B). The expression levels of Δp53 mRNA in the two tumor samples with in frame (FU27), or with a frame shift (FU08) mutation located in the splice cassette were very low (Figure 6), further confirming the existence of Δp53 in the other human tumor samples.


Expression of full-length p53 and its isoform Deltap53 in breast carcinomas in relation to mutation status and clinical parameters.

Baumbusch LO, Myhre S, Langerød A, Bergamaschi A, Geisler SB, Lønning PE, Deppert W, Dornreiter I, Børresen-Dale AL - Mol. Cancer (2006)

Correlation between mRNA expression level of full-length p53 versus Δp53 in breast carcinomas with various p53 mutations. p53 and Δp53 mRNA expression levels of mutated p53 in human breast tumors are shown with p53 relative mRNA expression in a.u. (arbitrary units) on x-axis and Δp53 on y-axis. Different mutation types are indicated by various symbols. "Mutational hybrids", mutations represented on full-length p53, but removed in Δp53, are marked with open symbols. Mutations present in both isoforms are specified with filled symbols. The shape of the symbols indicate the various mutation types: ■, □ missense mutations, ◊ in frame mutations, ▲, Δ nonsense mutations, * frame shift mutations, ● splice mutations, - mutations in the splice cassette (the two samples full-filling this criteria are highlighted with their sample ID). Horizontal lines show borders between the median values of the relative mRNA expression subgroups: MII vs Wt vs MI. The regression line for missense mutations is drawn with an equation y = 1.03x - 0.12 and a regression coefficient of 0.89. (1 low p53 value in this sample might be due to mutation in p53 primer binding site, 2 low Δp53 value in this sample might be due to mutation in Δp53 primer binding site – for details see Additional file 2).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1636663&req=5

Figure 6: Correlation between mRNA expression level of full-length p53 versus Δp53 in breast carcinomas with various p53 mutations. p53 and Δp53 mRNA expression levels of mutated p53 in human breast tumors are shown with p53 relative mRNA expression in a.u. (arbitrary units) on x-axis and Δp53 on y-axis. Different mutation types are indicated by various symbols. "Mutational hybrids", mutations represented on full-length p53, but removed in Δp53, are marked with open symbols. Mutations present in both isoforms are specified with filled symbols. The shape of the symbols indicate the various mutation types: ■, □ missense mutations, ◊ in frame mutations, ▲, Δ nonsense mutations, * frame shift mutations, ● splice mutations, - mutations in the splice cassette (the two samples full-filling this criteria are highlighted with their sample ID). Horizontal lines show borders between the median values of the relative mRNA expression subgroups: MII vs Wt vs MI. The regression line for missense mutations is drawn with an equation y = 1.03x - 0.12 and a regression coefficient of 0.89. (1 low p53 value in this sample might be due to mutation in p53 primer binding site, 2 low Δp53 value in this sample might be due to mutation in Δp53 primer binding site – for details see Additional file 2).
Mentions: Comparison of the mRNA levels of the two isoforms p53 and Δp53 in 88 tumors samples revealed a high correlation in both mutated and non-mutated tumors with a correlation coefficient of r2 = 0.86 for wild-type and r2 = 0.85 for mutant tumors, respectively (Figure 5A and 5B). The expression levels of Δp53 mRNA in the two tumor samples with in frame (FU27), or with a frame shift (FU08) mutation located in the splice cassette were very low (Figure 6), further confirming the existence of Δp53 in the other human tumor samples.

Bottom Line: Patients expressing mutated full-length p53 and non-mutated (wild-type) Deltap53, "mutational hybrids", showed a slightly higher frequency of patients with distant metastasis at time of diagnosis compared to other patients with p53 mutations, but otherwise did not differ significantly in any other clinical parameter.Expression of p53 is accompanied by the functionally different isoform Deltap53 at the mRNA level in cell lines and human breast tumors.Investigations of "mutational hybrid" patients highlighted that wild-type Deltap53 does not compensates for mutated p53, but rather may be associated with a worse prognosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Genetics, Institute for Cancer Research, Rikshospitalet-Radiumhospitalet Medical Center, 0310 Oslo, Norway. lars.baumbusch@medisin.uio.no

ABSTRACT

Background: The tumor suppressor gene p53 (TP53) controls numerous signaling pathways and is frequently mutated in human cancers. Novel p53 isoforms suggest alternative splicing as a regulatory feature of p53 activity.

Results: In this study we have analyzed mRNA expression of both wild-type and mutated p53 and its respective Deltap53 isoform in 88 tumor samples from breast cancer in relation to clinical parameters and molecular subgroups. Three-dimensional structure differences for the novel internally deleted p53 isoform Deltap53 have been predicted. We confirmed the expression of Deltap53 mRNA in tumors using quantitative real-time PCR technique. The mRNA expression levels of the two isoforms were strongly correlated in both wild-type and p53-mutated tumors, with the level of the Deltap53 isoform being approximately 1/3 of that of the full-length p53 mRNA. Patients expressing mutated full-length p53 and non-mutated (wild-type) Deltap53, "mutational hybrids", showed a slightly higher frequency of patients with distant metastasis at time of diagnosis compared to other patients with p53 mutations, but otherwise did not differ significantly in any other clinical parameter. Interestingly, the p53 wild-type tumors showed a wide range of mRNA expression of both p53 isoforms. Tumors with mRNA expression levels in the upper or lower quartile were significantly associated with grade and molecular subtypes. In tumors with missense or in frame mutations the mRNA expression levels of both isoforms were significantly elevated, and in tumors with nonsense, frame shift or splice mutations the mRNA levels were significantly reduced compared to those expressing wild-type p53.

Conclusion: Expression of p53 is accompanied by the functionally different isoform Deltap53 at the mRNA level in cell lines and human breast tumors. Investigations of "mutational hybrid" patients highlighted that wild-type Deltap53 does not compensates for mutated p53, but rather may be associated with a worse prognosis. In tumors, both isoforms show strong correlations in different mutation-dependent mRNA expression patterns.

Show MeSH
Related in: MedlinePlus