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Molecular and functional characteristics of ovarian surface epithelial cells transformed by KrasG12D and loss of Pten in a mouse model in vivo.

Mullany LK, Fan HY, Liu Z, White LD, Marshall A, Gunaratne P, Anderson ML, Creighton CJ, Xin L, Deavers M, Wong KK, Richards JS - Oncogene (2011)

Bottom Line: Ovarian cancer is a complex and deadly disease that remains difficult to detect at an early curable stage.Furthermore, although some oncogenic (Kras, Pten/PI3K and Trp53) pathways that are frequently mutated, deleted or amplified in ovarian cancer are known, how these pathways initiate and drive specific morphological phenotypes and tumor outcomes remain unclear.We propose that elevated TRP53 and miR-34a-c may exert negatively regulatory effects that reduce the proliferative potential of OSE cells leading to the low-grade serous adenocarcinoma phenotype.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA.

ABSTRACT
Ovarian cancer is a complex and deadly disease that remains difficult to detect at an early curable stage. Furthermore, although some oncogenic (Kras, Pten/PI3K and Trp53) pathways that are frequently mutated, deleted or amplified in ovarian cancer are known, how these pathways initiate and drive specific morphological phenotypes and tumor outcomes remain unclear. We recently generated Pten(fl/fl); Kras(G12D); Amhr2-Cre mice to disrupt the Pten gene and express a stable mutant form of Kras(G12D) in ovarian surface epithelial (OSE) cells. On the basis of histopathologic criteria, the mutant mice developed low-grade ovarian serous papillary adenocarcinomas at an early age and with 100% penetrance. This highly reproducible phenotype provides the first mouse model in which to study this ovarian cancer subtype. OSE cells isolated from ovaries of mutant mice at 5 and 10 weeks of age exhibit temporal changes in the expression of specific Mullerian epithelial marker genes, grow in soft agar and develop ectopic invasive tumors in recipient mice, indicating that the cells are transformed. Gene profiling identified specific mRNAs and microRNAs differentially expressed in purified OSE cells derived from tumors of the mutant mice compared with wild-type OSE cells. Mapping of transcripts or genes between the mouse OSE mutant data sets, the Kras signature from human cancer cell lines and the human ovarian tumor array data sets, documented significant overlap, indicating that KRAS is a key driver of OSE transformation in this context. Two key hallmarks of the mutant OSE cells in these mice are the elevated expression of the tumor-suppressor Trp53 (p53) and its microRNA target, miR-34a-c. We propose that elevated TRP53 and miR-34a-c may exert negatively regulatory effects that reduce the proliferative potential of OSE cells leading to the low-grade serous adenocarcinoma phenotype.

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Temporal changes in OSE cell morphology and expression of specific genes associated with the serous adenocarcinoma phenotype in the Pten;KrasG12D;Amhr2-cre mice. A.) H&E and immuno-labeling of ovarian sections from WT and mutant mice at 5 and 10 weeks of age. B.) Gene expression patterns in whole ovaries of WT or tumor bearing (T) Pten;KrasG12D;Amhr2-cre mice at 5 and 10 weeks of age.
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Figure 1: Temporal changes in OSE cell morphology and expression of specific genes associated with the serous adenocarcinoma phenotype in the Pten;KrasG12D;Amhr2-cre mice. A.) H&E and immuno-labeling of ovarian sections from WT and mutant mice at 5 and 10 weeks of age. B.) Gene expression patterns in whole ovaries of WT or tumor bearing (T) Pten;KrasG12D;Amhr2-cre mice at 5 and 10 weeks of age.

Mentions: Histological sections prepared from ovaries of control mice at 5 and 10 weeks of age show that the OSE cell layer is comprised on a single layer of meso-epithelial cells as reported by others (Auersperg N, Wong AST, et al., 2001, Orsulic S, Li Y, et al., 2002). These cells stain for the epithelial cell markers cytokeratin 8 (Fan HY, Liu Z, et al., 2009) and for E-cadherin (CDH1) but not for vimentin (Figure 1A). In contrast, the OSE layer present in ovaries of the Ptenfl/fl;KrasG12D;Amhr2-Cre mice exhibits visible changes in morphology with obvious epithelial cell hyperplasia evident as early as 3 weeks of age in some ovaries and at 5 weeks in all ovaries. By 10 weeks of age, all mice exhibited low-grade serous, papillary-like adenocarcinomas as classified by expert pathologists (Fig. 1A). Of note, the OSE tumor cells stain for cytokeratin 8 (Fan HY, Liu Z, et al., 2009) and vimentin but not for E-cadherin (Figure 1A) suggesting that the cells have undergone an epithelial to mesenchymal type of transformation (Lee JM, Dedhar S, et al., 2006). Furthermore, the OSE tumor cells do not stain for calretinin, a marker of mesotheliomas and do not exhibit atypic nuclear morphology observed in high-grade adenocarcinomas (Supplemental Figure 1). However, the tumor OSE cells do stain positive for estrogen receptor alpha (ESR1), providing additional evidence that these tumors represent low-grade adenocarcinomas (Supplemental Figure 1) (Wong KK, Lu KH, et al., 2007).


Molecular and functional characteristics of ovarian surface epithelial cells transformed by KrasG12D and loss of Pten in a mouse model in vivo.

Mullany LK, Fan HY, Liu Z, White LD, Marshall A, Gunaratne P, Anderson ML, Creighton CJ, Xin L, Deavers M, Wong KK, Richards JS - Oncogene (2011)

Temporal changes in OSE cell morphology and expression of specific genes associated with the serous adenocarcinoma phenotype in the Pten;KrasG12D;Amhr2-cre mice. A.) H&E and immuno-labeling of ovarian sections from WT and mutant mice at 5 and 10 weeks of age. B.) Gene expression patterns in whole ovaries of WT or tumor bearing (T) Pten;KrasG12D;Amhr2-cre mice at 5 and 10 weeks of age.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3139785&req=5

Figure 1: Temporal changes in OSE cell morphology and expression of specific genes associated with the serous adenocarcinoma phenotype in the Pten;KrasG12D;Amhr2-cre mice. A.) H&E and immuno-labeling of ovarian sections from WT and mutant mice at 5 and 10 weeks of age. B.) Gene expression patterns in whole ovaries of WT or tumor bearing (T) Pten;KrasG12D;Amhr2-cre mice at 5 and 10 weeks of age.
Mentions: Histological sections prepared from ovaries of control mice at 5 and 10 weeks of age show that the OSE cell layer is comprised on a single layer of meso-epithelial cells as reported by others (Auersperg N, Wong AST, et al., 2001, Orsulic S, Li Y, et al., 2002). These cells stain for the epithelial cell markers cytokeratin 8 (Fan HY, Liu Z, et al., 2009) and for E-cadherin (CDH1) but not for vimentin (Figure 1A). In contrast, the OSE layer present in ovaries of the Ptenfl/fl;KrasG12D;Amhr2-Cre mice exhibits visible changes in morphology with obvious epithelial cell hyperplasia evident as early as 3 weeks of age in some ovaries and at 5 weeks in all ovaries. By 10 weeks of age, all mice exhibited low-grade serous, papillary-like adenocarcinomas as classified by expert pathologists (Fig. 1A). Of note, the OSE tumor cells stain for cytokeratin 8 (Fan HY, Liu Z, et al., 2009) and vimentin but not for E-cadherin (Figure 1A) suggesting that the cells have undergone an epithelial to mesenchymal type of transformation (Lee JM, Dedhar S, et al., 2006). Furthermore, the OSE tumor cells do not stain for calretinin, a marker of mesotheliomas and do not exhibit atypic nuclear morphology observed in high-grade adenocarcinomas (Supplemental Figure 1). However, the tumor OSE cells do stain positive for estrogen receptor alpha (ESR1), providing additional evidence that these tumors represent low-grade adenocarcinomas (Supplemental Figure 1) (Wong KK, Lu KH, et al., 2007).

Bottom Line: Ovarian cancer is a complex and deadly disease that remains difficult to detect at an early curable stage.Furthermore, although some oncogenic (Kras, Pten/PI3K and Trp53) pathways that are frequently mutated, deleted or amplified in ovarian cancer are known, how these pathways initiate and drive specific morphological phenotypes and tumor outcomes remain unclear.We propose that elevated TRP53 and miR-34a-c may exert negatively regulatory effects that reduce the proliferative potential of OSE cells leading to the low-grade serous adenocarcinoma phenotype.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA.

ABSTRACT
Ovarian cancer is a complex and deadly disease that remains difficult to detect at an early curable stage. Furthermore, although some oncogenic (Kras, Pten/PI3K and Trp53) pathways that are frequently mutated, deleted or amplified in ovarian cancer are known, how these pathways initiate and drive specific morphological phenotypes and tumor outcomes remain unclear. We recently generated Pten(fl/fl); Kras(G12D); Amhr2-Cre mice to disrupt the Pten gene and express a stable mutant form of Kras(G12D) in ovarian surface epithelial (OSE) cells. On the basis of histopathologic criteria, the mutant mice developed low-grade ovarian serous papillary adenocarcinomas at an early age and with 100% penetrance. This highly reproducible phenotype provides the first mouse model in which to study this ovarian cancer subtype. OSE cells isolated from ovaries of mutant mice at 5 and 10 weeks of age exhibit temporal changes in the expression of specific Mullerian epithelial marker genes, grow in soft agar and develop ectopic invasive tumors in recipient mice, indicating that the cells are transformed. Gene profiling identified specific mRNAs and microRNAs differentially expressed in purified OSE cells derived from tumors of the mutant mice compared with wild-type OSE cells. Mapping of transcripts or genes between the mouse OSE mutant data sets, the Kras signature from human cancer cell lines and the human ovarian tumor array data sets, documented significant overlap, indicating that KRAS is a key driver of OSE transformation in this context. Two key hallmarks of the mutant OSE cells in these mice are the elevated expression of the tumor-suppressor Trp53 (p53) and its microRNA target, miR-34a-c. We propose that elevated TRP53 and miR-34a-c may exert negatively regulatory effects that reduce the proliferative potential of OSE cells leading to the low-grade serous adenocarcinoma phenotype.

Show MeSH
Related in: MedlinePlus