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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 overexpression was an early genetic event during ovarian tumorigenesis.A. PIK3CA mRNA expression was significantly up-regulated in the established epithelial ovarian cancer cell lines (n = 15) compared with primary cultured ovarian surface epithelial cells (n = 6, p = 0.041). mRNA expression was measured by real-time RT-PCR. B. mRNA expression level of PIK3CA was significantly upregulated in ovarian cancer specimens compared with normal control ovarian epithelium. Normal ovarian epithelium was isolated by laser-capture microdissection. There was no further significant increase of PIK3CA mRNA expression after malignant transformation among different stages of ovarian cancer.
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pone-0004295-g001: PIK3CA overexpression was an early genetic event during ovarian tumorigenesis.A. PIK3CA mRNA expression was significantly up-regulated in the established epithelial ovarian cancer cell lines (n = 15) compared with primary cultured ovarian surface epithelial cells (n = 6, p = 0.041). mRNA expression was measured by real-time RT-PCR. B. mRNA expression level of PIK3CA was significantly upregulated in ovarian cancer specimens compared with normal control ovarian epithelium. Normal ovarian epithelium was isolated by laser-capture microdissection. There was no further significant increase of PIK3CA mRNA expression after malignant transformation among different stages of ovarian cancer.

Mentions: In many human tumors, including epithelial ovarian cancer [23], [25], [26], [27], [28], [29], [30], PIK3CA activation is a critical oncogenic event and can be mediated by multiple genetic/genomic alterations such as gene copy number amplification [23], gain of functional mutations [24], and transcriptional up-regulation [33], [34], [35]. However, the function of PIK3CA activation during the process of malignant transformation of OSE is still not well understood. Our previous studies indicate that mRNA expression of PIK3CA is significantly up-regulated in the early-stage of ovarian cancer development, strongly suggesting that PIK3CA might be involved in OSE transformation [25]. To confirm our previous finding, we first compared expression levels of PIK3CA mRNA in established epithelial ovarian cancer cell lines (n = 15) with primary cultures of immortalized human ovarian surface epitheliums (IOSEs, n = 6). Consistently, we found that mRNA levels in epithelial tumor cell lines were significantly higher than in IOSEs (p = 0.041, Figure 1A). Next, we examined mRNA expression of PIK3CA in microdissected normal human ovarian epithelium (n = 4) as well as epithelial ovarian cancer specimens including FIGO stages I (n = 16), II (n = 8), III (n = 31) and IV (n = 11). We found that mRNA expression level of PIK3CA was significantly upregulated in ovarian cancer specimens compared to normal control ovarian epithelium (p<0.02), and there was no further significant increase after malignant transformation among different stages of ovarian cancer (p>0.05, Figure 1B), which is consistent with our previous observation [25]. To further confirm PIK3CA is indeed expressed in early-stage ovarian cancer, we also examined the protein product of PIK3CA gene, p110α, by immunohistochemical staining in early malignant transformed human ovarian surface epithelium. We found that p110α was highly detectable in the early malignant transformed human ovarian surface epithelium (Figure 2A and B). Taken together, these results indicate that PIK3CA overexpression is in fact an early genetic event during ovarian oncogenesis, thus suggesting that PIK3CA activation might be causally involved in this process.


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 overexpression was an early genetic event during ovarian tumorigenesis.A. PIK3CA mRNA expression was significantly up-regulated in the established epithelial ovarian cancer cell lines (n = 15) compared with primary cultured ovarian surface epithelial cells (n = 6, p = 0.041). mRNA expression was measured by real-time RT-PCR. B. mRNA expression level of PIK3CA was significantly upregulated in ovarian cancer specimens compared with normal control ovarian epithelium. Normal ovarian epithelium was isolated by laser-capture microdissection. There was no further significant increase of PIK3CA mRNA expression after malignant transformation among different stages of ovarian cancer.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2629728&req=5

pone-0004295-g001: PIK3CA overexpression was an early genetic event during ovarian tumorigenesis.A. PIK3CA mRNA expression was significantly up-regulated in the established epithelial ovarian cancer cell lines (n = 15) compared with primary cultured ovarian surface epithelial cells (n = 6, p = 0.041). mRNA expression was measured by real-time RT-PCR. B. mRNA expression level of PIK3CA was significantly upregulated in ovarian cancer specimens compared with normal control ovarian epithelium. Normal ovarian epithelium was isolated by laser-capture microdissection. There was no further significant increase of PIK3CA mRNA expression after malignant transformation among different stages of ovarian cancer.
Mentions: In many human tumors, including epithelial ovarian cancer [23], [25], [26], [27], [28], [29], [30], PIK3CA activation is a critical oncogenic event and can be mediated by multiple genetic/genomic alterations such as gene copy number amplification [23], gain of functional mutations [24], and transcriptional up-regulation [33], [34], [35]. However, the function of PIK3CA activation during the process of malignant transformation of OSE is still not well understood. Our previous studies indicate that mRNA expression of PIK3CA is significantly up-regulated in the early-stage of ovarian cancer development, strongly suggesting that PIK3CA might be involved in OSE transformation [25]. To confirm our previous finding, we first compared expression levels of PIK3CA mRNA in established epithelial ovarian cancer cell lines (n = 15) with primary cultures of immortalized human ovarian surface epitheliums (IOSEs, n = 6). Consistently, we found that mRNA levels in epithelial tumor cell lines were significantly higher than in IOSEs (p = 0.041, Figure 1A). Next, we examined mRNA expression of PIK3CA in microdissected normal human ovarian epithelium (n = 4) as well as epithelial ovarian cancer specimens including FIGO stages I (n = 16), II (n = 8), III (n = 31) and IV (n = 11). We found that mRNA expression level of PIK3CA was significantly upregulated in ovarian cancer specimens compared to normal control ovarian epithelium (p<0.02), and there was no further significant increase after malignant transformation among different stages of ovarian cancer (p>0.05, Figure 1B), which is consistent with our previous observation [25]. To further confirm PIK3CA is indeed expressed in early-stage ovarian cancer, we also examined the protein product of PIK3CA gene, p110α, by immunohistochemical staining in early malignant transformed human ovarian surface epithelium. We found that p110α was highly detectable in the early malignant transformed human ovarian surface epithelium (Figure 2A and B). Taken together, these results indicate that PIK3CA overexpression is in fact an early genetic event during ovarian oncogenesis, thus suggesting that PIK3CA activation might be causally involved in this process.

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