Expression of FHIT in primary cultures of human epithelial ovarian tumors and malignant ovarian ascites

Multicellular detachment generates metastatic spheroids during intra-abdominal dissemination in epithelial ovarian cancer

Ovarian cancer is the most lethal gynecological cancer, where survival rates have had modest improvement over the last 30 years. Metastasis of cancer cells is a major clinical problem, and patient mortality occurs when ovarian cancer cells spread beyond the confinement of ovaries. Disseminated ovarian cancer cells typically spread within the abdomen, where ascites accumulation aids in their transit. Metastatic ascites contain multicellular spheroids, which promote chemo-resistance and recurrence. However, little is known about the origin and mechanisms through which spheroids arise. Using live-imaging of 3D culture models and animal models, we report that epithelial ovarian cancer (EOC) cells, the most common type of ovarian cancer, can spontaneously detach as either single cells or clusters. We report that clusters are more resistant to anoikis and have a potent survival advantage over single cells. Using in vivo lineage tracing, we found that multicellular spheroids arise preferentially from collective detachment, rather than aggregation in the abdomen. Finally, we report that multicellular spheroids from collective detachment are capable of seeding intra-abdominal metastases that retain intra-tumoral heterogeneity from the primary tumor.

Functional role of the Tau protein in epithelial ovarian cancer cells

Aim

The microtubule‐associated Tau protein is a marker of paclitaxel sensitivity in ovarian cancer. The aim of the present study was to elucidate the function of the Tau protein in epithelial ovarian cancer.

Methods

The correlation between Tau protein expression and the response to paclitaxel by using several ovarian cancer cell lines was investigated.

Results

A Western blot showed that the expression level of the Tau protein was the highest in the TOV112D cells. A cell‐counting kit showed that the proliferation rates were more inhibited in the cells with down‐regulated Tau protein than in the control cells, both with and without paclitaxel treatment. The proliferation rates of the control cells and the TOV112D cells also were compared with Tau protein overexpression. The level of cell proliferation was more inhibited in the cells that overexpressed the Tau protein, compared to the control cells, both with and without paclitaxel treatment. It was shown that both the down‐regulation and the overexpression of the Tau protein were related to the inhibition of TOV112D cell proliferation. Early and late apoptosis of the TOV112D cells that were transfected with Tau cDNA plasmid construct or Tau small interfering RNA significantly increased.

Conclusion

These findings suggest that the molecular targeting of the Tau protein could be a potential treatment for ovarian cancer.

A low, non-toxic dose of paclitaxel can prevent dendritic cell-precursors from becoming tolerogenic dendritic cells with impaired functions

Tumor infiltrating dendritic cells (TIDCs) are thought to be potent antigen-presenting cells able to activate tumor-specific cytotoxic T lymphocytes (CTLs) or tolerogenic DCs that suppress immune reaction against tumors to escape. We have recently reported that majority of these TIDCs were DEC-205(+) DCs having a cross-presenting ability of captured tumor antigens to CD8(+) T cells via class I MHC (MHC-I) molecules, nevertheless, when the TIDCs expressed down-modulated costimulatory molecules, such as CD80 and CD86, they will inhibit the priming and activation of immune effectors (Immunol. Cell Biol., 91: 545-555, 2013). Here, we show that DC-precursors (preDCs) but not the established DCs become tolerogenic DCs expressing down-regulated costimulatory molecules having low responsiveness to LPS or tumor cells, when exposed to soluble factors released from the encountered ovarian tumors in the early phase of their development. However, we found that we could reduce the secretion of those soluble factors with a low, nontoxic concentration of paclitaxel (PTX) and we could stop the preDCs to be tolerogenic DCs and maintain DC functions. These findings indicate that we could prevent the induction of tolerogenic DCs from preDCs by using low, non-toxic doses of anti-cancer drugs to establish DCs that effectively elicit tumor-specific CTLs.

Covering your bases: inheritance of DNA methylation in plant genomes

Cytosine methylation is an important base modification that is inherited across mitotic and meiotic cell divisions in plant genomes. Heritable methylation variants can contribute to within-species phenotypic variation. Few methylation variants were known until recently, making it possible to begin to address major unanswered questions: the extent of natural methylation variation within plant genomes, its effects on phenotypic variation, its degree of dependence on genotype, and how it fits into an evolutionary context. Techniques like whole-genome bisulfite sequencing (WGBS) make it possible to determine cytosine methylation states at single-base resolution across entire genomes and populations. Application of this method to natural and novel experimental populations is revealing answers to these long-standing questions about the role of DNA methylation in plant genomes.

VGLL3 expression is associated with a tumor suppressor phenotype in epithelial ovarian cancer

Previous studies have implicated vestigial like 3 (VGLL3), a chromosome 3p12.3 gene that encodes a putative transcription co-factor, as a candidate tumor suppressor gene (TSG) in high-grade serous ovarian carcinomas (HGSC), the most common type of epithelial ovarian cancer. A complementation analysis based on microcell-mediated chromosome transfer (MMCT) using a centric fragment of chromosome 3 (der3p12-q12.1) into the OV-90 ovarian cancer cell line haploinsufficient for 3p and lacking VGLL3 expression was performed to assess the effect on tumorigenic potential and growth characteristics. Genetic characterization of the derived MMCT hybrids revealed that only the hybrid that contained an intact VGLL3 locus exhibited alterations of tumorigenic potential in a nude mouse xenograft model and various in vitro growth characteristics. Only stable OV-90 transfectant clones expressing low levels of VGLL3 were derived. These clones exhibited an altered cytoplasmic morphology characterized by numerous single membrane bound multivesicular-bodies (MVB) that were not attributed to autophagy. Overexpression of VGLL3 in OV-90 was achieved using a lentivirus-based tetracycline inducible gene expression system, which also resulted in MVB formation in the infected cell population. Though there was no significant differences in various in vitro and in vivo growth characteristics in a comparison of VGLL3-expressing clones with empty vector transfectant controls, loss of VGLL3 expression was observed in tumors derived from mouse xenograft models. VGLL3 gene and protein expression was significantly reduced in HGSC samples (>98%, p < 0.05) relative to either normal ovarian surface epithelial cells or epithelial cells of the fallopian tube, possible tissues of origin of HGSC. Also, there appeared to be to be more cases with higher staining levels in stromal tissue component from HGSC cases that had a prolonged disease-free survival. The results taken together suggest that VGLL3 is involved in tumor suppressor pathways, a feature that is characterized by the absence of VGLL3 expression in HGSC samples.

The tumour suppressor SOX11 is associated with improved survival among high grade epithelial ovarian cancers and is regulated by reversible promoter methylation

Background

The neural transcription factor SOX11 has been described as a prognostic marker in epithelial ovarian cancers (EOC), however its role in individual histological subtypes and tumour grade requires further clarification. Furthermore, methylation-dependent silencing of SOX11 has been reported for B cell lymphomas and indicates that epigenetic drugs may be used to re-express this tumour suppressor, but information on SOX11 promoter methylation in EOC is still lacking.

Methods

SOX11 expression and clinicopathological data was compared using χ² test in a cohort of 154 cases of primary invasive EOC. Kaplan-Meier analysis and the log rank test were applied to evaluate ovarian cancer-specific survival (OCSS) and overall survival (OS) in strata, according to SOX11 expression. Also, the methylation status of the SOX11 promoter was determined by sodium bisulfite sequencing and methylation specific PCR (MSP). Furthermore, the effect of ectopic overexpression of SOX11 on proliferation was studied through [3H]-thymidine incorporation.

Results

SOX11 expression was associated with an improved survival of patients with high grade EOC, although not independent of stage. Further analyses of EOC cell lines showed that SOX11 mRNA and protein were expressed in two of five cell lines, correlating with promoter methylation status. Demethylation was successfully performed using 5'-Aza-2'deoxycytidine (5-Aza-dC) resulting in SOX11 mRNA and protein expression in a previously negative EOC cell line. Furthermore, overexpression of SOX11 in EOC cell lines confirmed the growth regulatory role of SOX11.

Conclusions

SOX11 is a functionally associated protein in EOC with prognostic value for high-grade tumours. Re-expression of SOX11 in EOC indicates a potential use of epigenetic drugs to affect cellular growth in SOX11-negative tumours.

Human ovarian surface epithelial cells immortalized with hTERT maintain functional pRb and p53 expression

OBJECTIVE

Cell immortalization is considered to be a prerequisite status for carcinogenesis. Normal human ovarian surface epithelial (OSE) cells, which are thought to be the origin of most of human ovarian carcinomas, have a very limited lifespan in culture. Establishment of immortalized OSE cell lines has, in the past, required inactivation of pRb and p53 functions. However, this often leads to increased chromosome instability during prolonged culture.

MATERIALS AND METHODS

In this study, we have used a retroviral infection method to overexpress human telomerase reverse transcriptase (hTERT) gene, in primary normal OSE cells, under optimized culture conditions.

RESULTS

In vitro and in vivo analysis of hTERT-immortalized cell lines confirmed their normal epithelial characteristics. Gene expression profiles and functional analysis of p16(INK4A), p15(INK4B), pRb and p53 confirmed the presence of their intact functions. Our study suggests that inactivation of pRb and p53 is not necessary for OSE immortalization. Furthermore, down-regulation of p15(INK4B) in the immortalized cells may indicate a functional role for this protein in them.

CONCLUSION

These immortal OSE cell lines are likely to be an important tool for studying human OSE biology and carcinogenesis.

Transfer of chromosome 3 fragments suppresses tumorigenicity of an ovarian cancer cell line monoallelic for chromosome 3p

Multiple chromosome 3p tumor suppressor genes (TSG) have been proposed in the pathogenesis of ovarian cancer based on complex patterns of 3p loss. To attain functional evidence in support of TSGs and identify candidate regions, we applied a chromosome transfer method involving cell fusions of the tumorigenic OV90 human ovarian cancer cell line, monoallelic for 3p and an irradiated mouse cell line containing a human chromosome 3 in order to derive OV90 hybrids containing normal 3p fragments. The resulting hybrids showed complete or incomplete suppression of tumorigenicity in nude mouse xenograft assays, and varied in their ability to form colonies in soft agarose and three-dimensional spheroids in a manner consistent with alteration of their in vivo tumorigenic phenotypes. Expression microarray analysis identified a set of common differentially expressed genes, such as SPARC, DAB2 and VEGF, some of which have been shown implicated in ovarian cancer. Genotyping assays revealed that they harbored normal 3p fragments, some of which overlapped candidate TSG regions (3p25-p26, 3p24 and 3p14-pcen) identified previously in loss of heterozygosity analyses of ovarian cancers. However, only the 3p12-pcen region was acquired in common by all hybrids where expression microarray analysis identified differentially expressed genes. The correlation of 3p12-pcen transfer and tumor suppression with a concerted re-programming of the cellular transcriptome suggest that the putative TSG may have affected key underlying events in ovarian cancer.

Effusion cytology in ovarian cancer: new molecular methods as aids to diagnosis and prognosis

Carcinoma of the ovary is the leading cause of death from gynecologic cancer in western countries. Ovarian carcinoma is commonly associated with the accumulation of fluid that contains malignant cells in the peritoneal and pleural cavities. This article details the current knowledge regarding the diagnostic and biologic characteristics of ovarian carcinoma cells in effusions, and the genotypic and phenotypic differences between solid primary tumors and metastatic lesions. Finally, we present a new approach, by which the analysis of fresh frozen viable cells allows us to study in vivo the links between expression and activity of extracellular mediators, membrane receptors, intracellular signaling, and transcription factors, and their potential therapeutic and prognostic significance.

Tumor suppressor genes on chromosome 3p involved in the pathogenesis of lung and other cancers

Loss of heterozygosity (LOH) involving several chromosome 3p regions accompanied by chromosome 3p deletions are detected in almost 100% of small (SCLCs) and more than 90% of non-small (NSCLCs) cell lung cancers. In addition, these changes appear early in the pathogenesis of lung cancer and are found as clonal lesions in the smoking damaged respiratory epithelium including histologically normal epithelium as well as in epithelium showing histologic changes of preneoplasia. These 3p genetic alterations lead to the conclusion that the short arm of human chromosome 3 contains several tumor suppressor gene(s) (TSG(s)). Although the first data suggesting that 3p alterations were involved in lung carcinogenesis were published more than 10 years ago, only recently has significant progress been achieved in identifying the candidate TSGs and beginning to demonstrate their functional role in tumor pathogenesis. Some of the striking results of these findings has been the discovery of multiple 3p TSGs and the importance of tumor acquired promoter DNA methylation as an epigenetic mechanism for inactivating the expression of these genes in lung cancer. This progress, combined with the well known role of smoking as an environmental causative risk factor in lung cancer pathogenesis, is leading to the development of new diagnostic and therapeutic strategies which can be translated into the clinic to combat and prevent the lung cancer epidemic. It is clear now that genetic and epigenetic abnormalities of several genes residing in chromosome region 3p are important for the development of lung cancers but it is still obscure how many of them exist and which of the numerous candidate TSGs are the key players in lung cancer pathogenesis. We review herein our current knowledge and describe the most credible candidate genes.

Transcriptional profiling reveals that several common fragile-site genes are downregulated in ovarian cancer

Previous transcriptional profiling analysis of 14 primary ovarian tumors identified approximately 12,000 genes as decreased in expression by at least twofold in one or more of the tumors sampled. Among those genes were several known to be mapped to common fragile sites (CFSs), some of which had previously been shown to exhibit a loss of expression in ovarian carcinoma. Therefore, we selected a subset of genes to determine whether they localized within CFSs. Of the 262 genes that were downregulated at least twofold in 13 of 14 tumors, 10 genes were selected based on the following criteria: localization to a CFS band; documented aberrations in at least one malignancy; and feasibility of scoring breakage at the specific CFS. Fluorescence in situ hybridization analysis was performed using bacterial artificial chromosome clones encompassing portions of the genes to determine the position of the genes relative to their corresponding CFSs. Nine genes were determined to localize within seven previously uncloned CFSs. Semiquantitative reverse-transcription/polymerase chain reaction analysis of the cell lines and primary ovarian tumors validated the downregulation of seven of the 10 genes. We identified portions of seven uncloned CFSs and provide data to suggest that several of the genes mapping within CFSs may be inactivated in ovarian cancer.

Altered gene expression in immunogenic poorly differentiated thyroid carcinomas from RET/PTC3p53-/- mice

Cancers develop and progress via activation of oncogenes and loss of tumor suppressor genes, a progression that can be recapitulated through cross breeding mouse strains harboring genetic mutations. To define the role of RET/PTC3, p53 and Fhit in thyroid carcinogenesis, we intercrossed RET/PTC3 transgenics with p53-/- mice. This new strain, RET/PTC3p53-/-, succumb to rapidly growing and strikingly large multilobed thyroid tumors containing mixtures of both well and poorly differentiated, highly proliferative follicular epithelial cells. Interestingly, transplanted tumors from RET/PTC3p53-/- mice grew in SCID but not syngeneic immunocompetent mice indicating that these advanced tumors were immunogenic. RET/PTC3 protein expression was reduced to undetectable levels in tumors of older mice suggesting that the continued elevated expression of RET/PTC3 may not be necessary for tumor progression. Similarly, expression of Fhit protein was reduced in early tumors and undetected in older tumors irrespective of tumor histopathology. In contrast to RET/PTC3p53-/- mice, RET/PTC3Fhit-/- mice did not develop advanced thyroid carcinomas. These studies support a model of human thyroid cancer whereby thyroid epithelium expresses RET/PTC3 protein at early stages of tumor development, followed by the reduction of RET/PTC3 and loss of p53 function with progressive reduction of Fhit protein expression coincident with malignant progression.