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The p53R172H mutant does not enhance hepatocellular carcinoma development and progression.

Ahronian LG, Driscoll DR, Klimstra DS, Lewis BC - PLoS ONE (2015)

Bottom Line: However, shRNA-mediated knockdown of mutant p53 in p53R172H-expressing HCC cell lines resulted in decreased cell migration and anchorage-independent growth.These data suggest that pathways regulated by these p53 family members are similarly impacted by p53R172H in mutant expressing cells, and by alternate mechanisms in p53 cells, resulting in equivalent phenotypes.Taken together these data point to the importance of p63 and p73 in constraining HCC progression.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.

ABSTRACT
Hepatocellular carcinoma is a highly deadly malignancy, accounting for approximately 800,000 deaths worldwide every year. Mutation of the p53 tumor suppressor gene is a common genetic change in HCC, present in 30% of cases. p53R175H (corresponding to p53R172H in mice) is a hotspot for mutation that demonstrates "prometastatic" gain-of-function in other cancer models. Since the frequency of p53 mutation increases with tumor grade in HCC, we hypothesized that p53R172H is a gain-of-function mutation in HCC that contributes to a decrease in tumor-free survival and an increase in metastasis. In an HCC mouse model, we found that p53R172H/flox mice do not have decreased survival, increased tumor incidence, or increased metastasis, relative to p53flox/flox littermates. Analysis of cell lines derived from both genotypes indicated that there are no differences in anchorage-independent growth and cell migration. However, shRNA-mediated knockdown of mutant p53 in p53R172H-expressing HCC cell lines resulted in decreased cell migration and anchorage-independent growth. Thus, although p53 mutant-expressing cells and tumors do not have enhanced properties relative to their p53 counterparts, p53R172H-expressing HCC cells depend on this mutant for their transformation. p53 mutants have been previously shown to bind and inhibit the p53 family proteins p63 and p73. Interestingly, we find that the levels of p63 and p73 target genes are similar in p53 mutant and p53 HCC cells. These data suggest that pathways regulated by these p53 family members are similarly impacted by p53R172H in mutant expressing cells, and by alternate mechanisms in p53 cells, resulting in equivalent phenotypes. Consistent with this, we find that p53 HCC cell lines display lower levels of the TA isoforms of p63 and p73 and higher levels of ΔNp63. Taken together these data point to the importance of p63 and p73 in constraining HCC progression.

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Related in: MedlinePlus

Cell lines derived from p53R172H-expressing HCCs do not display enhanced properties when compared to p53- HCCs.A) Immunoblots demonstrating expression of p53 and p21 in selected mouse tumor-derived cell lines. B) Transwell migration assay of HCC cell lines derived from p53fl/fl and p53R172H tumors. C) Soft agar colony formation assay of HCC cell lines derived from p53fl/fl and p53R172H tumors.
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pone.0123816.g002: Cell lines derived from p53R172H-expressing HCCs do not display enhanced properties when compared to p53- HCCs.A) Immunoblots demonstrating expression of p53 and p21 in selected mouse tumor-derived cell lines. B) Transwell migration assay of HCC cell lines derived from p53fl/fl and p53R172H tumors. C) Soft agar colony formation assay of HCC cell lines derived from p53fl/fl and p53R172H tumors.

Mentions: We generated a collection of HCC cell lines isolated from tumors induced in p53 and p53 mutant livers. Eight (8) tumor cell lines, 4 from each group, were compared to determine whether the presence of p53R172H enhanced transformation-associated phenotypes in vitro. p53R172H tumor-derived cell lines expressed p53 as expected, while p53fl/fl cell lines had no detectable p53 (Fig 2A). Importantly, expression of the p53 target gene p21 was not induced in p53R172H cell lines relative to p53fl/fl lines following gemcitabine treatment, consistent with the absence of functional p53 protein (Fig 2A).


The p53R172H mutant does not enhance hepatocellular carcinoma development and progression.

Ahronian LG, Driscoll DR, Klimstra DS, Lewis BC - PLoS ONE (2015)

Cell lines derived from p53R172H-expressing HCCs do not display enhanced properties when compared to p53- HCCs.A) Immunoblots demonstrating expression of p53 and p21 in selected mouse tumor-derived cell lines. B) Transwell migration assay of HCC cell lines derived from p53fl/fl and p53R172H tumors. C) Soft agar colony formation assay of HCC cell lines derived from p53fl/fl and p53R172H tumors.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4401698&req=5

pone.0123816.g002: Cell lines derived from p53R172H-expressing HCCs do not display enhanced properties when compared to p53- HCCs.A) Immunoblots demonstrating expression of p53 and p21 in selected mouse tumor-derived cell lines. B) Transwell migration assay of HCC cell lines derived from p53fl/fl and p53R172H tumors. C) Soft agar colony formation assay of HCC cell lines derived from p53fl/fl and p53R172H tumors.
Mentions: We generated a collection of HCC cell lines isolated from tumors induced in p53 and p53 mutant livers. Eight (8) tumor cell lines, 4 from each group, were compared to determine whether the presence of p53R172H enhanced transformation-associated phenotypes in vitro. p53R172H tumor-derived cell lines expressed p53 as expected, while p53fl/fl cell lines had no detectable p53 (Fig 2A). Importantly, expression of the p53 target gene p21 was not induced in p53R172H cell lines relative to p53fl/fl lines following gemcitabine treatment, consistent with the absence of functional p53 protein (Fig 2A).

Bottom Line: However, shRNA-mediated knockdown of mutant p53 in p53R172H-expressing HCC cell lines resulted in decreased cell migration and anchorage-independent growth.These data suggest that pathways regulated by these p53 family members are similarly impacted by p53R172H in mutant expressing cells, and by alternate mechanisms in p53 cells, resulting in equivalent phenotypes.Taken together these data point to the importance of p63 and p73 in constraining HCC progression.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.

ABSTRACT
Hepatocellular carcinoma is a highly deadly malignancy, accounting for approximately 800,000 deaths worldwide every year. Mutation of the p53 tumor suppressor gene is a common genetic change in HCC, present in 30% of cases. p53R175H (corresponding to p53R172H in mice) is a hotspot for mutation that demonstrates "prometastatic" gain-of-function in other cancer models. Since the frequency of p53 mutation increases with tumor grade in HCC, we hypothesized that p53R172H is a gain-of-function mutation in HCC that contributes to a decrease in tumor-free survival and an increase in metastasis. In an HCC mouse model, we found that p53R172H/flox mice do not have decreased survival, increased tumor incidence, or increased metastasis, relative to p53flox/flox littermates. Analysis of cell lines derived from both genotypes indicated that there are no differences in anchorage-independent growth and cell migration. However, shRNA-mediated knockdown of mutant p53 in p53R172H-expressing HCC cell lines resulted in decreased cell migration and anchorage-independent growth. Thus, although p53 mutant-expressing cells and tumors do not have enhanced properties relative to their p53 counterparts, p53R172H-expressing HCC cells depend on this mutant for their transformation. p53 mutants have been previously shown to bind and inhibit the p53 family proteins p63 and p73. Interestingly, we find that the levels of p63 and p73 target genes are similar in p53 mutant and p53 HCC cells. These data suggest that pathways regulated by these p53 family members are similarly impacted by p53R172H in mutant expressing cells, and by alternate mechanisms in p53 cells, resulting in equivalent phenotypes. Consistent with this, we find that p53 HCC cell lines display lower levels of the TA isoforms of p63 and p73 and higher levels of ΔNp63. Taken together these data point to the importance of p63 and p73 in constraining HCC progression.

Show MeSH
Related in: MedlinePlus