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Nuclear envelope structural defect underlies the main cause of aneuploidy in ovarian carcinogenesis

View Article: PubMed Central - PubMed

ABSTRACT

Background: The Cancer Atlas project has shown that p53 is the only commonly (96 %) mutated gene found in high-grade serous epithelial ovarian cancer, the major histological subtype. Another general genetic change is extensive aneuploidy caused by chromosomal numerical instability, which is thought to promote malignant transformation. Conventionally, aneuploidy is thought to be the result of mitotic errors and chromosomal nondisjunction during mitosis. Previously, we found that ovarian cancer cells often lost or reduced nuclear lamina proteins lamin A/C, and suppression of lamin A/C in cultured ovarian epithelial cells leads to aneuploidy. Following up, we investigated the mechanisms of lamin A/C-suppression in promoting aneuploidy and synergy with p53 inactivation.

Results: We found that suppression of lamin A/C by siRNA in human ovarian surface epithelial cells led to frequent nuclear protrusions and formation of micronuclei. Lamin A/C-suppressed cells also often underwent mitotic failure and furrow regression to form tetraploid cells, which frequently underwent aberrant multiple polar mitosis to form aneuploid cells. In ovarian surface epithelial cells isolated from p53 mice, transient suppression of lamin A/C produced massive aneuploidy with complex karyotypes, and the cells formed malignant tumors when implanted in mice.

Conclusions: Based on the results, we conclude that a nuclear envelope structural defect, such as the loss or reduction of lamin A/C proteins, leads to aneuploidy by both the formation of tetraploid intermediates following mitotic failure, and the reduction of chromosome (s) following nuclear budding and subsequent loss of micronuclei. We suggest that the nuclear envelope defect, rather than chromosomal unequal distribution during cytokinesis, is the main cause of aneuploidy in ovarian cancer development.

No MeSH data available.


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p53 inactivation and lamin A/C suppression result in aneuploidy and complex karyotypes. Primary p53 knockout MOSE cells were transfected with control or siRNA (si-Lam A) to suppress lamin A/C expression. The cells were maintained and passaged for 2 months in culture, and then subjected to chromosome analysis. Chromosome number counting and cytogenetic analysis were performed in 50 metaphase spreads for each cell preparation. At least 10 chromosome spreads from each preparation were randomly selected and estimated for chromosome number, and 2 appropriate samples were used for karyotyping. a and b, 2 representative examples of chromosome spreads from p53 (-/-) and siRNA-lamin A/C-treated MOSE cells are shown. c and d, 2 examples of karyotyping from p53 (-/-) and siRNA-lamin A/C-treated cells are shown
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Fig3: p53 inactivation and lamin A/C suppression result in aneuploidy and complex karyotypes. Primary p53 knockout MOSE cells were transfected with control or siRNA (si-Lam A) to suppress lamin A/C expression. The cells were maintained and passaged for 2 months in culture, and then subjected to chromosome analysis. Chromosome number counting and cytogenetic analysis were performed in 50 metaphase spreads for each cell preparation. At least 10 chromosome spreads from each preparation were randomly selected and estimated for chromosome number, and 2 appropriate samples were used for karyotyping. a and b, 2 representative examples of chromosome spreads from p53 (-/-) and siRNA-lamin A/C-treated MOSE cells are shown. c and d, 2 examples of karyotyping from p53 (-/-) and siRNA-lamin A/C-treated cells are shown

Mentions: Indeed, chromosome analysis of metaphase spreads indicated aneuploidy and wide range of chromosomal number distribution in the lamin A/C-suppressed p53-deficient MOSE cells, such as 56, 60, 63, 67, 80, 81, 82, 84, 89, and 94 chromosomes, determined in 10 randomly selected metaphase spreads. Two of the examples are shown (Fig. 3a, b). Chromosome identification in two samples revealed complex karyotypes in the lamin A/C-suppressed p53-deficient MOSE cells (Fig. 3c, d), and a marker chromosome was observed in one sample (Fig. 3c). For comparison, metaphases from p53 knockout MOSE cells (without prior lamin A/C-siRNA treatment) were found to be largely near diploid (40 chromosomes) to tetraploid (80 chromosomes), and karyotyping by the cytogenetic core facility indicated that obvious structural abnormalities were not observed, but subtle abnormalities cannot be ruled out (quoted from the facility report).Fig. 3


Nuclear envelope structural defect underlies the main cause of aneuploidy in ovarian carcinogenesis
p53 inactivation and lamin A/C suppression result in aneuploidy and complex karyotypes. Primary p53 knockout MOSE cells were transfected with control or siRNA (si-Lam A) to suppress lamin A/C expression. The cells were maintained and passaged for 2 months in culture, and then subjected to chromosome analysis. Chromosome number counting and cytogenetic analysis were performed in 50 metaphase spreads for each cell preparation. At least 10 chromosome spreads from each preparation were randomly selected and estimated for chromosome number, and 2 appropriate samples were used for karyotyping. a and b, 2 representative examples of chromosome spreads from p53 (-/-) and siRNA-lamin A/C-treated MOSE cells are shown. c and d, 2 examples of karyotyping from p53 (-/-) and siRNA-lamin A/C-treated cells are shown
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Related In: Results  -  Collection

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Fig3: p53 inactivation and lamin A/C suppression result in aneuploidy and complex karyotypes. Primary p53 knockout MOSE cells were transfected with control or siRNA (si-Lam A) to suppress lamin A/C expression. The cells were maintained and passaged for 2 months in culture, and then subjected to chromosome analysis. Chromosome number counting and cytogenetic analysis were performed in 50 metaphase spreads for each cell preparation. At least 10 chromosome spreads from each preparation were randomly selected and estimated for chromosome number, and 2 appropriate samples were used for karyotyping. a and b, 2 representative examples of chromosome spreads from p53 (-/-) and siRNA-lamin A/C-treated MOSE cells are shown. c and d, 2 examples of karyotyping from p53 (-/-) and siRNA-lamin A/C-treated cells are shown
Mentions: Indeed, chromosome analysis of metaphase spreads indicated aneuploidy and wide range of chromosomal number distribution in the lamin A/C-suppressed p53-deficient MOSE cells, such as 56, 60, 63, 67, 80, 81, 82, 84, 89, and 94 chromosomes, determined in 10 randomly selected metaphase spreads. Two of the examples are shown (Fig. 3a, b). Chromosome identification in two samples revealed complex karyotypes in the lamin A/C-suppressed p53-deficient MOSE cells (Fig. 3c, d), and a marker chromosome was observed in one sample (Fig. 3c). For comparison, metaphases from p53 knockout MOSE cells (without prior lamin A/C-siRNA treatment) were found to be largely near diploid (40 chromosomes) to tetraploid (80 chromosomes), and karyotyping by the cytogenetic core facility indicated that obvious structural abnormalities were not observed, but subtle abnormalities cannot be ruled out (quoted from the facility report).Fig. 3

View Article: PubMed Central - PubMed

ABSTRACT

Background: The Cancer Atlas project has shown that p53 is the only commonly (96 %) mutated gene found in high-grade serous epithelial ovarian cancer, the major histological subtype. Another general genetic change is extensive aneuploidy caused by chromosomal numerical instability, which is thought to promote malignant transformation. Conventionally, aneuploidy is thought to be the result of mitotic errors and chromosomal nondisjunction during mitosis. Previously, we found that ovarian cancer cells often lost or reduced nuclear lamina proteins lamin A/C, and suppression of lamin A/C in cultured ovarian epithelial cells leads to aneuploidy. Following up, we investigated the mechanisms of lamin A/C-suppression in promoting aneuploidy and synergy with p53 inactivation.

Results: We found that suppression of lamin A/C by siRNA in human ovarian surface epithelial cells led to frequent nuclear protrusions and formation of micronuclei. Lamin A/C-suppressed cells also often underwent mitotic failure and furrow regression to form tetraploid cells, which frequently underwent aberrant multiple polar mitosis to form aneuploid cells. In ovarian surface epithelial cells isolated from p53 mice, transient suppression of lamin A/C produced massive aneuploidy with complex karyotypes, and the cells formed malignant tumors when implanted in mice.

Conclusions: Based on the results, we conclude that a nuclear envelope structural defect, such as the loss or reduction of lamin A/C proteins, leads to aneuploidy by both the formation of tetraploid intermediates following mitotic failure, and the reduction of chromosome (s) following nuclear budding and subsequent loss of micronuclei. We suggest that the nuclear envelope defect, rather than chromosomal unequal distribution during cytokinesis, is the main cause of aneuploidy in ovarian cancer development.

No MeSH data available.


Related in: MedlinePlus