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Expression of activated PIK3CA in ovarian surface epithelium results in hyperplasia but not tumor formation.

Liang S, Yang N, Pan Y, Deng S, Lin X, Yang X, Katsaros D, Roby KF, Hamilton TC, Connolly DC, Coukos G, Zhang L - PLoS ONE (2009)

Bottom Line: The consistent result was also observed in primary cultured OSEs.Although enforced expression of PIK3CA could not induce OSE anchorage-independent growth, it significantly increased anchorage-independent growth of OSE transformed by mutant K-ras.While PIK3CA activation may not be able to initiate OSE transformation, we conclude that activation of PIK3CA may be an important molecular event contributing to the maintenance of OSE transformation initiated by oncogenes such as K-ras.

View Article: PubMed Central - PubMed

Affiliation: Center for Research on the Early Detection and Cure of Ovarian Cancer, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America.

ABSTRACT

Background: The Phosphatidylinositol 3'-kinase is a key regulator in various cancer-associated signal transduction pathways. Genetic alterations of its catalytic subunit alpha, PIK3CA, have been identified in ovarian cancer. Our in vivo data suggests that PIK3CA activation is one of the early genetic events in ovarian cancer. However, its role in malignant transformation of ovarian surface epithelium (OSE) is largely unclear.

Methodology/principal findings: Using the Müllerian inhibiting substance type II receptor (MISIIR) promoter, we generated transgenic mice that expressed activated PIK3CA in the Müllerian epithelium. Overexpression of PIK3CA in OSE induced remarkable hyperplasia, but was not able to malignantly transform OSE in vivo. The consistent result was also observed in primary cultured OSEs. Although enforced expression of PIK3CA could not induce OSE anchorage-independent growth, it significantly increased anchorage-independent growth of OSE transformed by mutant K-ras.

Conclusions/significance: While PIK3CA activation may not be able to initiate OSE transformation, we conclude that activation of PIK3CA may be an important molecular event contributing to the maintenance of OSE transformation initiated by oncogenes such as K-ras.

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Related in: MedlinePlus

PIK3CA was overexpressed in OSE of PIK3CA-Tg mouse.A. Ovarian surface epithelial cells were microdissected by laser capture microdissection technology. B. PIK3CA mRNA expression in OSEs from WT or PIK3CA-Tg OSEs was analyzed by real-time RT-PCR. The primers were able to detected both wt PIK3CA cDNA and cDNA from transgene expression (myr-PIK3CA).
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pone-0004295-g006: PIK3CA was overexpressed in OSE of PIK3CA-Tg mouse.A. Ovarian surface epithelial cells were microdissected by laser capture microdissection technology. B. PIK3CA mRNA expression in OSEs from WT or PIK3CA-Tg OSEs was analyzed by real-time RT-PCR. The primers were able to detected both wt PIK3CA cDNA and cDNA from transgene expression (myr-PIK3CA).

Mentions: To confirm overexpression of PIK3CA in the OSEs of transgenic mouse, we microdissected the OSE cells from PIK3CA-Tg and WT mice using laser capture microdissetion (LCM, Figure 6A). Total RNA was isolated, and PIK3CA mRNA expression was measured by real-time RT-PCR. We found that PIK3CA mRNA expression level was 18.5-fold higher in OSEs from PIK3CA-Tg mice (200.93 ±89.47 relative expression unit) than from WT mice (10.87 ± 7.28 relative expression unit, p = 0.009, Figure 6B). In addition, by immunohistochemistry (using two different antibodies), we confirmed that p110α was highly expressed in the OSE of the PIK3CA-Tg mice (data not shown). Then, we followed up the ovarian tumor development in PIK3CA-Tg mice. We found that expression of the activated PIK3CA resulted in hyperplasia in mouse OSE and a paucity of follicles in four month-old female mice. Female transgenic PIK3CA-Tg mice exhibited subfertility. Figure 7A shows the typical OSE in 5-month control female mice. The Cytokeratin (an epithelial marker) positive OSE was observed on the surface of ovary as a monolayer. In the PIK3CA-Tg mice, hyperplasia was found in the OSE, and the epithelial origin of the lesions was confirmed by Cytokeratin staining (Figure 7B). Hyperplasia was found in more than 50% of the PIK3CA-Tg mice after four months post-birth, and in 100% of the PIK3CA-Tg mice after ten months post-birth. There were no invaginations or papillary structures observed in the OSE of PIK3CA-Tg mice. In the control mice, no significant hyperplasia in OSE was observed even after 12 months of post-birth. These results suggest that expression of activated PIK3CA in OSE induced hyperplasia of the OSE. We monitored for ovarian tumor development in both the transgenic and control mouse lines. A total of 218 female PIK3CA-Tg mice (#6: n = 94; #22: n = 44 and #26: n = 80) were evaluated (at least 30 mice of each line were followed for more than 18 months) and no epithelial ovarian tumors were observed. There was no difference in life span between the transgenic mice and control lines. This finding indicates that expression of activated PIK3CA in OSE causes hyperplasia in vivo but not tumor formation.


Expression of activated PIK3CA in ovarian surface epithelium results in hyperplasia but not tumor formation.

Liang S, Yang N, Pan Y, Deng S, Lin X, Yang X, Katsaros D, Roby KF, Hamilton TC, Connolly DC, Coukos G, Zhang L - PLoS ONE (2009)

PIK3CA was overexpressed in OSE of PIK3CA-Tg mouse.A. Ovarian surface epithelial cells were microdissected by laser capture microdissection technology. B. PIK3CA mRNA expression in OSEs from WT or PIK3CA-Tg OSEs was analyzed by real-time RT-PCR. The primers were able to detected both wt PIK3CA cDNA and cDNA from transgene expression (myr-PIK3CA).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2629728&req=5

pone-0004295-g006: PIK3CA was overexpressed in OSE of PIK3CA-Tg mouse.A. Ovarian surface epithelial cells were microdissected by laser capture microdissection technology. B. PIK3CA mRNA expression in OSEs from WT or PIK3CA-Tg OSEs was analyzed by real-time RT-PCR. The primers were able to detected both wt PIK3CA cDNA and cDNA from transgene expression (myr-PIK3CA).
Mentions: To confirm overexpression of PIK3CA in the OSEs of transgenic mouse, we microdissected the OSE cells from PIK3CA-Tg and WT mice using laser capture microdissetion (LCM, Figure 6A). Total RNA was isolated, and PIK3CA mRNA expression was measured by real-time RT-PCR. We found that PIK3CA mRNA expression level was 18.5-fold higher in OSEs from PIK3CA-Tg mice (200.93 ±89.47 relative expression unit) than from WT mice (10.87 ± 7.28 relative expression unit, p = 0.009, Figure 6B). In addition, by immunohistochemistry (using two different antibodies), we confirmed that p110α was highly expressed in the OSE of the PIK3CA-Tg mice (data not shown). Then, we followed up the ovarian tumor development in PIK3CA-Tg mice. We found that expression of the activated PIK3CA resulted in hyperplasia in mouse OSE and a paucity of follicles in four month-old female mice. Female transgenic PIK3CA-Tg mice exhibited subfertility. Figure 7A shows the typical OSE in 5-month control female mice. The Cytokeratin (an epithelial marker) positive OSE was observed on the surface of ovary as a monolayer. In the PIK3CA-Tg mice, hyperplasia was found in the OSE, and the epithelial origin of the lesions was confirmed by Cytokeratin staining (Figure 7B). Hyperplasia was found in more than 50% of the PIK3CA-Tg mice after four months post-birth, and in 100% of the PIK3CA-Tg mice after ten months post-birth. There were no invaginations or papillary structures observed in the OSE of PIK3CA-Tg mice. In the control mice, no significant hyperplasia in OSE was observed even after 12 months of post-birth. These results suggest that expression of activated PIK3CA in OSE induced hyperplasia of the OSE. We monitored for ovarian tumor development in both the transgenic and control mouse lines. A total of 218 female PIK3CA-Tg mice (#6: n = 94; #22: n = 44 and #26: n = 80) were evaluated (at least 30 mice of each line were followed for more than 18 months) and no epithelial ovarian tumors were observed. There was no difference in life span between the transgenic mice and control lines. This finding indicates that expression of activated PIK3CA in OSE causes hyperplasia in vivo but not tumor formation.

Bottom Line: The consistent result was also observed in primary cultured OSEs.Although enforced expression of PIK3CA could not induce OSE anchorage-independent growth, it significantly increased anchorage-independent growth of OSE transformed by mutant K-ras.While PIK3CA activation may not be able to initiate OSE transformation, we conclude that activation of PIK3CA may be an important molecular event contributing to the maintenance of OSE transformation initiated by oncogenes such as K-ras.

View Article: PubMed Central - PubMed

Affiliation: Center for Research on the Early Detection and Cure of Ovarian Cancer, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America.

ABSTRACT

Background: The Phosphatidylinositol 3'-kinase is a key regulator in various cancer-associated signal transduction pathways. Genetic alterations of its catalytic subunit alpha, PIK3CA, have been identified in ovarian cancer. Our in vivo data suggests that PIK3CA activation is one of the early genetic events in ovarian cancer. However, its role in malignant transformation of ovarian surface epithelium (OSE) is largely unclear.

Methodology/principal findings: Using the Müllerian inhibiting substance type II receptor (MISIIR) promoter, we generated transgenic mice that expressed activated PIK3CA in the Müllerian epithelium. Overexpression of PIK3CA in OSE induced remarkable hyperplasia, but was not able to malignantly transform OSE in vivo. The consistent result was also observed in primary cultured OSEs. Although enforced expression of PIK3CA could not induce OSE anchorage-independent growth, it significantly increased anchorage-independent growth of OSE transformed by mutant K-ras.

Conclusions/significance: While PIK3CA activation may not be able to initiate OSE transformation, we conclude that activation of PIK3CA may be an important molecular event contributing to the maintenance of OSE transformation initiated by oncogenes such as K-ras.

Show MeSH
Related in: MedlinePlus