Giant ovarian cancer weighing 100 kg with poor prognosis.

We encountered a patient with giant ovarian cancer with a tumor weight of 100 kg. The patient's girth measured 198 cm after approximately 4 years' duration, and she complained of dyspnea and inability to walk. Adnectomy was performed with intensive intraoperative monitoring. The ovarian cancer was entirely adherent to the parietal peritoneum. However, 10 h after adnectomy, she died of massive abdominal bleeding from extremely redundant parietal peritoneum caused by disseminated intravascular coagulation.

ZAC, LIT1 (KCNQ1OT1) and p57KIP2 (CDKN1C) are in an imprinted gene network that may play a role in Beckwith-Wiedemann syndrome.

Loss of genomic imprinting is involved in a number of developmental abnormalities and cancers. ZAC is an imprinted gene expressed from the paternal allele of chromosome 6q24 within a region known to harbor a tumor suppressor gene for several types of neoplasia. p57(KIP2) (CDKN1C) is a maternally expressed gene located on chromosome 11p15.5 which encodes a cyclin-dependent kinase inhibitor that may also act as a tumor suppressor gene. Mutations in ZAC and p57KIP2 have been implicated in transient neonatal diabetes mellitus (TNDB) and Beckwith-Wiedemann syndrome, respectively. Patients with these diseases share many characteristics. Here we show that mouse Zac1 and p57Kip2 have a strikingly similar expression pattern. ZAC, a sequence-specific DNA-binding protein, binds within the CpG island of LIT1 (KCNQ1OT1), a paternally expressed, anti-sense RNA thought to negatively regulate p57(KIP2) in cis. ZAC induces LIT1 transcription in a methylation-dependent manner. Our data suggest that ZAC may regulate p57(KIP2) through LIT1, forming part of a novel signaling pathway regulating cell growth. Mutations in ZAC may, therefore, contribute to Beckwith-Wiedemann syndrome. Furthermore, we find changes in DNA methylation at the LIT1 putative imprinting control region in two patients with TNDB.

Epigenetic silencing of the imprinted gene ZAC by DNA methylation is an early event in the progression of human ovarian cancer.

ZAC is a paternally expressed, imprinted gene located on chromosome 6q24, within a region known to harbor a tumor suppressor gene for several types of neoplasia, including human ovarian cancer (HOC). We have failed to identify genetic mutations in the ZAC gene in tumor material. Many imprinted genes contain differentially allele-specific-methylated regions (DMR) and harbor promoter activity that is regulated by the DNA methylation. Aberrant DNA methylation is a common feature of neoplasia and changes in DNA methylation at the ZAC locus have been reported in some cases of HOC. We investigated the DNA methylation and ZAC mRNA expression levels in a larger sample of primary HOC material, obtained by laser capture microdissection. ZAC mRNA expression was reduced in the majority of samples and this correlated with hypermethylation of the ZAC-DMR. Treatment of hypermethylated cells lines with a demethylating agent restored ZAC expression. Our studies indicate that transcriptional silencing of ZAC is likely to be caused by DNA methylation in HOC. Forced expression of ZAC resulted in a reduction in proliferation and marked induction of apoptotic cell death. The ZAC-mediated apoptosis signal is p53-independent and eliminated by inhibitors of caspase 3, 8 and 9. Reduced expression of ZAC would therefore favor tumor progression. As there were no significant differences in either DNA methylation or expression of ZAC mRNA between localized and advanced tumors, our data indicates that loss of ZAC is a relatively early event in HOC. (Supplementary material for this article can be found on the International Journal of Cancer website at http://www.interscience.wiley.com/jpages/0020-7136/suppmat/index.html.)

K-Ras and H-Ras activation promote distinct consequences on endometrial cell survival.

A considerable amount of evidence indicates that Ras signaling contributes to the development of endometrial cancer. We previously demonstrated that endometrial cancer cells carrying oncogenic [(12)Val]K-ras were susceptible to apoptosis. The present study examined the role of K-and H-Ras in the induction of apoptosis using rat endometrial cells (RENT4 cells). We found that constitutively activated K-Ras promoted apoptotic cell death, whereas the H-Ras mutant rescued rat endometrial cells from apoptosis. Expression of a constitutively active form of Raf-1 (Raf-CAAX) promoted apoptosis, whereas expression of a constitutively active catalytic subunit of phosphoinositide 3-kinase, p110K227E, allowed cells to escape from apoptosis. Moreover, inhibition of the MEK-MAPK pathway by the specific inhibitor, UO126, rescued the cells from apoptosis, whereas the inhibition of phosphoinositide 3-kinase by its specific inhibitor, LY294002, promoted apoptosis in RENT4 cells expressing activated K-Ras. However, both inhibitors promoted apoptosis in RENT4 cells expressing activated H-Ras. This difference in the regulation of apoptosis by the MEK inhibitor between K-Ras- and H-Ras-expressing cells depended on the interaction of effector proteins downstream of each Ras isoform. Finally, to elucidate the role of downstream K-Ras signal pathways, we generated K-Ras effector domain mutants (K12V35S, K12V40C). We examined the incidence of apoptotic cell death induced by the K-Ras effector domain mutants (K12V35S, K12V40C). The relative ratio of phospho-MAPK to phospho-Akt compared with that of mock cells was higher in K12V35S cells than in K12V40C cells. Ectopic expression of K12V35S protein increased the proportion of apoptotic cells, and in turn, the expression of K12V40C protein decreased compared with the expression of K12V protein without the effector domain mutant. These results demonstrate that K- and H-Ras-mediated signaling pathways exert distinct effects on apoptosis and that K-Ras downstream Raf/MEK/MAPK pathway is required for the induction of apoptosis in endometrial cells. Coordination of the two pathways contributes to endometrial cell survival.