Reduced expression of AMPK-ß1 during tumor progression enhances the oncogenic capacity of advanced ovarian cancer.

AMP-activated protein kinase (AMPK) is a key energy sensor that is involved in regulating cell metabolism. Our previous study revealed that the subunits of the heterotimeric AMPK enzyme are diversely expressed during ovarian cancer progression. However, the impact of the variable expression of these AMPK subunits in ovarian cancer oncogenesis remains obscure. Here, we provide evidence to show that reduced expression of the AMPK-ß1 subunit during tumor progression is associated with the increased oncogenic capacity of advanced ovarian cancer cells. Immunohistochemical analysis revealed that AMPK-ß1 levels were reduced in advanced-stage (P = 0.008), high-grade (P = 0.013) and metastatic ovarian cancers (P = 0.008). Intriguingly, down-regulation of AMPK-ß1 was progressively reduced from tumor stages 1 to 3 of ovarian cancer. Functionally, enforced expression of AMPK-ß1 inhibited ovarian-cancer-cell proliferation, anchorage-independent cell growth, cell migration and invasion. Conversely, depletion of AMPK-ß1 by siRNA enhanced the oncogenic capacities of ovarian cancer cells, suggesting that the loss of AMPK-ß1 favors the aggressiveness of ovarian cancer. Mechanistically, enforced expression of AMPK-ß1 increased AMPK activity, which, in turn, induced cell-cycle arrest via inhibition of AKT/ERK signaling activity as well as impaired cell migration/invasion through the suppression of JNK signaling in ovarian cancer cells. Taken together, these findings suggest that the reduced expression of AMPK-ß1 confers lower AMPK activity, which enhances the oncogenic capacity of advanced-stage ovarian cancer.

Physiological ß-catenin signaling controls self-renewal networks and generation of stem-like cells from nasopharyngeal carcinoma.

BACKGROUND: A few reports suggested that low levels of Wnt signaling might drive cell reprogramming, but these studies could not establish a clear relationship between Wnt signaling and self-renewal networks. There are ongoing debates as to whether and how the Wnt/ß-catenin signaling is involved in the control of pluripotency gene networks. Additionally, whether physiological ß-catenin signaling generates stem-like cells through interactions with other pathways is as yet unclear. The nasopharyngeal carcinoma HONE1 cells have low expression of ß-catenin and wild-type expression of p53, which provided a possibility to study regulatory mechanism of stemness networks induced by physiological levels of Wnt signaling in these cells. RESULTS: Introduction of increased ß-catenin signaling, haploid expression of ß-catenin under control by its natural regulators in transferred chromosome 3, resulted in activation of Wnt/ß-catenin networks and dedifferentiation in HONE1 hybrid cell lines, but not in esophageal carcinoma SLMT1 hybrid cells that had high levels of endogenous ß-catenin expression. HONE1 hybrid cells displayed stem cell-like properties, including enhancement of CD24(+) and CD44(+) populations and generation of spheres that were not observed in parental HONE1 cells. Signaling cascades were detected in HONE1 hybrid cells, including activation of p53- and RB1-mediated tumor suppressor pathways, up-regulation of Nanog-, Oct4-, Sox2-, and Klf4-mediated pluripotency networks, and altered E-cadherin expression in both in vitro and in vivo assays. qPCR array analyses further revealed interactions of physiological Wnt/ß-catenin signaling with other pathways such as epithelial-mesenchymal transition, TGF-ß, Activin, BMPR, FGFR2, and LIFR- and IL6ST-mediated cell self-renewal networks. Using ß-catenin shRNA inhibitory assays, a dominant role for ß-catenin in these cellular network activities was observed. The expression of cell surface markers such as CD9, CD24, CD44, CD90, and CD133 in generated spheres was progressively up-regulated compared to HONE1 hybrid cells. Thirty-four up-regulated components of the Wnt pathway were identified in these spheres. CONCLUSIONS: Wnt/ß-catenin signaling regulates self-renewal networks and plays a central role in the control of pluripotency genes, tumor suppressive pathways and expression of cancer stem cell markers. This current study provides a novel platform to investigate the interaction of physiological Wnt/ß-catenin signaling with stemness transition networks.

Epigenetic alteration of the metallothionein 1E gene in human endometrial carcinomas.

Aberrant expression of metallothioneins (MTs) has been observed in several human tumors. In our microarray analysis, MT-1E was found to have much lower expression in endometrial cancer cells as compared with other types of cancer cells generated from the cervix, ovary or prostate. The result was confirmed by quantitative RT-PCR analysis of the MT-1E levels in individual cancer cells. Treatment of endometrial cancer cells with 5-azacytidine could reactivate MT-1E expression. We further analyzed the DNA methylation status of the promoter region of MT-1E using methylation-sensitive restriction enzymes HhaI and HpaII, followed by PCR. Promoter hypermethylation was detected in 42.4% (53/125) of the endometrial carcinoma samples, whilst none of the 38 normal tissues or hyperplasia samples were methylated. The mRNA levels of MT-1E were significantly lower in the methylation-positive than in the methylation-negative samples. Endometrial carcinoma samples with low MT-1E expression coincidently had low levels of estrogen receptor-alpha expression and vice versa. This phenomenon was not observed in the expression pattern between estrogen receptor-beta and MT-1E. There was no significant correlation between MT-1E methylation and any clinical parameters. In conclusion, a high frequency of cancer-specific hypermethylation of MT-1E was found in endometrial carcinomas. Its functional consequence in the development of endometrial cancer warrants further investigation.

Single nucleotide polymorphism of pi-class glutathione s-transferase and susceptibility to endometrial carcinoma.

PURPOSE: Endometrial carcinoma is the most common gynecologic cancer in developed countries. Prolonged unopposed estrogen exposure has been identified as the major risk factor. The pi-class glutathione S-transferase (GSTP1) is a phase II metabolic enzyme that is important in the detoxification of a wide range of electrophiles including carcinogenic steroid-hormone intermediates generated through oxidative metabolism. In this study, we aimed at determining the association between the GSTP1 polymorphism and the risk of endometrial carcinoma in a Chinese population. EXPERIMENTAL DESIGN: Genotyping of 180 cases and 200 age-matched controls were assessed by PCR-RFLP approach and confirmed by direct sequencing. RESULTS: Statistical analysis showed that patients of valine allele carriers had 2.03-fold of increased risk of developing endometrial carcinoma (P < 0.01). The allele frequencies for the Ile and Val variants between the cancer cases and controls were also significantly different (P < 0.01; odds ratio, 1.59; 95% confidence interval, 1.13-2.23). Such association was shown in endometrial cancers as a group and in type I endometrioid adenocarcinoma but not the type II nonendometrioid adenocarcinoma. In addition, the Val allele was found significantly associated with high-grade endometrial cancer and/or endometrial cancer of deep myometrial invasion (P < 0.01). Interestingly, the relatively low frequency of Val/Val genotype in both the cancer cases and controls, in parallel with the lower incidence of endometrial cancer in Chinese, was observed when compared with those in Caucasians. CONCLUSIONS: Our findings suggested that the GSTP1 Ile(105)Val polymorphism was associated with an increased risk of endometrial cancer. Further studies may be required to explore the possible significance of these polymorphisms on GSTP1-related metabolism that may affect the susceptibility of Asians to endometrial carcinoma.

Promoter methylation and differential expression of pi-class glutathione S-transferase in endometrial carcinoma.

Pi-class glutathione S-transferase (GSTP1), located on chromosome 11q13, codes for a phase II metabolic enzyme that detoxifies reactive electrophilic intermediates. The protein also interacts with steroid hormones in the human body. The role of GSTP1 in endometrial carcinoma has not been reported. In this study, we aimed at determining the expression of GSTP1 in relation to the epigenetic and genetic changes of the gene in endometrial carcinoma. The GSTP1 protein and mRNA expression was assessed by immunohistochemistry on tissue microarray and quantitative real-time reverse transcriptase-polymerase chain reaction, respectively. Its methylation status was studied by methylation-specific polymerase chain reaction and bisulfite sequencing. Possible mutations in coding region of GSTP1 were assessed by cDNA sequencing. Ninety-seven cases of endometrial carcinoma with available tissue blocks and clinical data were studied. Our results showed that 68.0% (66 of 97) of the cases showed reduced protein expression while 64% (16 of 25) showed reduced mRNA expression; 30.9% (30 of 97) of the cases demonstrated methylated alleles in at least one of the six methylation-specific polymerase chain reaction reactions. The methylation status significantly correlated with reduced protein expression (P = 0.008) and reduced mRNA expression (P = 0.003). Methylation at non-CpG sites including CpCpG trinucleotides and CpT dinucleotides were also observed. cDNA sequencing did not reveal genetic alterations in coding region of the gene. The extent of myometrial invasion was found to be significantly correlated with both the methylation status (P = 0.009) and the protein expression (P = 0.036) of the GSTP1 gene. We postulated that hypermethylation of the GSTP1 gene promoter region may act as a dynamic regulation mechanism contributing to reduced GSTP1 expression, which is associated with myometrial invasion potential of the endometrial carcinoma.

p73 expression is associated with the cellular radiosensitivity in cervical cancer after radiotherapy.

Apoptosis is one of the causes of cell death in cervical cancer following radiotherapy. By studying the gene expression profile with cDNA apoptotic array, the p73 gene was found overexpressed in radiosensitive cervical cancers when compared with radioresistant ones. To investigate the role of the p73 gene in relation to clinical assessment of radiosensitivity in cervical cancer based on the findings of residual tumor cells in cervical biopsies after completion of radiotherapy, we studied the protein expression of p73 in 59 cervical cancers after radiotherapy and 68 normal cervices using immunohistochemistry. The expression of p73 was found to be significantly increased in cancer samples and, more importantly, in those samples sensitive to radiotherapy (P < 0.001). The overexpression of p73 actually predicted a better prognosis in cervical cancer patients (P < 0.001). To investigate the possible involvement of p73 downstream genes, the protein expressions of p21 and Bax were studied. The expression of p21, but not Bax, was found to be positively correlated with the expression of p73 (P = 0.001). Furthermore, the epigenetic regulation of p73 expression via DNA methylation was also investigated in 103 cervical cancers and 124 normals. Hypermethylation of p73 gene was observed in 38.8% of cervical cancers, and it was significantly associated with reduced or absent p73 expression (P < 0.001). Reactivation of p73 expression in two cervical cancer cell lines by demethylation treatment supported the role of methylation in the regulation of p73 expression. Our findings suggested that p73 expression was related to the radiosensitivity of cervical cancer cells and may play an important role in the regulation of cellular radiosensitivity.

Detection of mitochondrial DNA mutations in gestational trophoblastic disease.

Mitochondrial DNA (mtDNA) mutations have been implicated in a wide range of human disease. However, its role in gestational trophoblastic disease remains unclear. In this study, the entire mitochondrial genome of 10 hydatidiform moles (HM) and one choriocarcinoma were examined by automated DNA sequencing after amplification by polymerase chain reaction. MtDNA sequences obtained separately from disease tissues (HM and choriocarcinoma) and patients' tissues were compared. Of the 133 neutral sequence variants identified, 41 have not been reported to date. Large or small-scale deletion or insertion was not detected in any of the samples studied. A total of six (five in the D-loop and one in the 16S rRNA gene) somatic point mutations were detected in the choriocarcinoma sample, in contrast to none being detected in the HM samples. Somatic mtDNA instability was detected in the D-loop region in three cases of HM as well as in the choriocarcinoma sample. Somatic mtDNA instability appeared in the same nucleotide position, from 303 to 309, within the Conserved Sequence Block II resulting in alteration in length of the homopolymorphic C-tract, reflecting microsatellite instability. The results suggest that mtDNA instability may be an early event occurring at a premalignant stage. Occurrence of multiple somatic mtDNA mutations in choriocarcinoma suggests that mtDNA mutations might play an important role in the molecular pathogenesis of invasive gestational trophoblastic disease.

Promoter hypermethylation of multiple genes in hydatidiform mole and choriocarcinoma.

The methylation status of genes in hydatidiform mole and choriocarcinoma and its significance is relatively unexplored. We investigated the methylation status of the promoter regions of six genes, p16, HIC-1, TIMP3, GSTP1, death-associated protein kinase (DAPK), and E-cadherin in 54 hydatidiform moles, five choriocarcinomas, and 10 first trimester placenta by methylation-specific polymerase chain reaction (PCR). Immunohistochemical expression of p16, TIMP3, and E-cadherin, and quantitative real-time RT-PCR of p16 was also performed. Among the six genes examined, the promoter region of four genes (E-cadherin, HIC-1, p16, TIMP3) in choriocarcinoma and three genes (E-cadherin, HIC-1, p16) in hydatidiform mole exhibited aberrant methylation whereas none was hypermethylated in normal placenta. There was a significant correlation between methylation and reduced expression of p16, E-cadherin, and TIMP3 (P < 0.001). Fifteen of the 54 patients with hydatidiform mole developed gestational trophoblastic neoplasia requiring chemotherapy. Promoter hypermethylation of p16 alone, or combined with E-cadherin, was significantly correlated to such development (P = 0.001, 0.0005, respectively). Hypermethylation of multiple genes, especially p16, might be related to the subsequent development of gestational trophoblastic neoplasia.

LTBP-2 confers pleiotropic suppression and promotes dormancy in a growth factor permissive microenvironment in nasopharyngeal carcinoma.

This study identified LTBP-2 as a pleiotropic tumor suppressor in nasopharyngeal carcinoma, which safeguards against critical malignant behaviors of tumor cells. LTBP-2 expression was significantly decreased or lost in up to 100% of NPC cell lines (7/7) and 80% of biopsies (24/30). Promoter hypermethylation was found to be involved in LTBP-2 silencing. Using a tetracycline-regulated inducible expression system, we unveiled functional roles of LTBP-2 in suppressing colony formation, anchorage-independent growth, cell migration, angiogenesis, VEGF secretion, and tumorigenicity. Three-dimensional culture studies suggested the involvement of LTBP-2 in maintenance of tumor cell dormancy in a growth factor favorable microenvironment.

Semi-quantitative fluorescent PCR analysis identifies PRKAA1 on chromosome 5 as a potential candidate cancer gene of cervical cancer.

OBJECTIVE: Comparative genomic hybridization has frequently detected amplification of chromosome 5p in cervical cancer, but candidate cancer genes within the region are rarely known. Therefore, we pursued to identify potential candidate gene related to cervical cancer development. METHODS: A series of 128 cervical tumor samples were examined by semi-quantitative fluorescent differential PCR for copy number changes on three candidate genes (PRKAA1, CTNND2 and POLS) mapped to chromosome 5p and one gene (ERBIN) mapped to chromosome 5q12.3. The impact of gene copy number was later analyzed in relation to HPV infection, tumor stage or tumor radiosensitivity. RESULTS: DNA copy numbers of PRKAA1, CTNND2 and ERBIN were significantly different from normal controls (P < 0.05). DNA copy number changes did not correlate with HPV infection, tumor stages or tumor radiosensitivity. Using RT-PCR, PRKAA1 mRNA expression in seven tumor samples with known 5p amplification was amplified from 3- to 15-fold. Over-expression of PRKAA1 was further confirmed by immunohistochemical staining on 125 paraffin-embedded cervical cancer tissues. The expression level in cervical tumor was significantly higher than that in normal epithelium (P < 0.001). CONCLUSIONS: PRKAA1 gene codes for the catalytic alpha 1 subunit of the AMP-activated protein kinase which is an important cellular metabolic stress regulator. It might assist tumor cells growth under stress. Thus, PRKAA1 may be one of the potential candidate genes for cervical carcinogenesis.

Differential expression of insulin-like growth factor binding protein 1 and ferritin light polypeptide in gestational trophoblastic neoplasia: combined cDNA suppression subtractive hybridization and microarray study.

BACKGROUND: Hydatidiform mole (HM), the most common type of gestational trophoblastic diseases, can be considered as placenta with abnormal chromosome composition with potential of malignant transformation. Few biologic markers can predict subsequent development of persistent gestational trophoblastic neoplasia (GTN) requiring chemotherapy. METHODS: Suppression subtractive hybridization (SSH) combined with cDNA microarray was used to compare the differential expression pattern of HM that spontaneously regressed and that subsequently developed metastatic GTN. Tissue-specific chips were constructed from the subtracted cDNA libraries, followed by cDNA microarray analysis. Verification by quantitative RNA analysis by real-time polymerase chain reaction (PCR) and immunohistochemical analysis was performed in 23 genotyped complete HM. RESULTS: Sixteen differentially expressed transcripts were identified. Quantitative RNA analysis confirmed down-regulation of ferritin light polypeptide (FTL) (P = 0.037) and insulin-like growth factor binding protein 1 (IGFBP1) (P = 0.037) in HM that subsequently developed GTN when compared with those HM that regressed. Immunohistochemical analysis further confirmed reduced IGFBP1 protein (P = 0.03) expression in HM that developed GTN. CONCLUSIONS: Findings showed that reduced expression of genes related to cell invasion and immunosuppression, especially FTL and IGFBP1, were associated with development of GTN, and this finding may provide a better understanding of the pathogenesis of GTN. The potential application of FTL and IGFBP1 in management of patients with HM should be explored.

Epigenetic and genetic alterations of p33ING1b in ovarian cancer.

p33ING1b is a candidate tumor suppressor gene and a nuclear protein. We investigated whether genetic and epigenetic mechanisms affect p33ING1b expression in ovarian cancer thus contributing toward its pathogenesis. A total of 111 ovarian cancers collected from Beijing and Hong Kong were used for this study. Weak or negative p33ING1b protein expression was demonstrated by immunohistochemistry on tissue microarray in 28/111 cases. Real-time quantitative RT-PCR also showed overall significant reduction of p33ING1b mRNA expression (P = 0.0137), with 53.1% (17/32) cases showing 2- to 5-fold reduction and absence of expression. The reduction of mRNA expression in cancer correlated with decreased p33ING1b protein expression (P < 0.0001). While no p33ING1b mutation was found, allelic loss at the p33ING1b locus was demonstrated in 25% (8/32) cases. The allelic loss profiles also showed statistical significant correlation with reduction of p33ING1b protein and mRNA expression (P = 0.031 and 0.030). Promoter methylation as assessed by methylation specific PCR was found in 23.9% (21/88) cases analyzed. Bisulfite sequencing results confirmed the p33ING1b promoter methylation status of these methylation positive cases. Statistical significant correlation between methylation and mRNA expression (P = 0.006) was demonstrated. Treatment with demethylating drug, 5'-aza-2'-deoxycytidine, resulted in dosage-dependent elevated mRNA expression of p33ING1b in ovarian cancer cell lines. This is the first study reporting epigenetic mechanism regulating the p33ING1b expression. Our findings support that genetic and epigenetic alteration of p33ING1b are likely to contribute towards the pathogenesis of ovarian cancers.

Mcl-1 expression in gestational trophoblastic disease correlates with clinical outcome: a differential expression study.

BACKGROUND: Hydatidiform moles (HMs) are abnormal pregnancies with a propensity for developing persistent disease in the form of gestational trophoblastic neoplasia (GTN), which requires chemotherapy. In previous studies, the authors demonstrated that low apoptotic activity was correlated with the progression of HM to GTN, and they hypothesized that some apoptosis-related genes may determine this progression. METHODS: The differential expression of apoptotic genes in HMs that subsequently developed into GTN was compared with the same expression in HMs that spontaneously regressed using a human apoptosis array; then, the expression was evaluated with real-time quantitative polymerase chain reaction analysis and immunohistochemistry using 54 clinical samples from patients with HMs who had follow-up data available. RESULTS: Using an apoptosis array, greater expression of Mcl-1, which is an antiapoptotic gene, was detected in HMs that subsequently developed into GTN. It was confirmed that the levels of Mcl-1 RNA expression (P = 0.017) and Mcl-1 protein expression (P < 0.001) in HMs that developed into persistent disease and required chemotherapy were significantly greater compared with the levels in HMs that regressed. Moreover, Mcl-1 immunoreactivity, which was detected predominantly in cytotrophoblasts, was correlated with the apoptotic index, as assessed with M30 cytoDeath immunohistochemistry, which is a good indicator of apoptotic events in the early-stage disease. CONCLUSIONS: The current results demonstrated that Mcl-1, as identified by a cyclic DNA array, may play a role in the pathogenesis of HMs and may have potential as a useful marker for predicting the clinical behavior of HMs.

Metastatic trophoblastic disease after an initial diagnosis of partial hydatidiform mole: genotyping and chromosome in situ hybridization analysis.

BACKGROUND: Hydatidiform mole (HM) is classified into partial (PHM) and complete (CHM) subtypes according to histopathologic and genetic criteria. Traditionally, it is believed that PHM carries a better prognosis and rarely develops metastasis. However, making a distinction between PHM and CHM using histologic criteria alone may be difficult. METHODS: The authors used fluorescent microsatellite genotyping following laser-capture microdissection and chromosome in situ hybridization (CISH) to perform a genetic analysis of six patients with histologically diagnosed PHM who subsequently developed metastatic gestational trophoblastic neoplasia. RESULTS: Patients ranged in age from 25 years to 44 years (mean, 33.2 years). The gestational age of the molar pregnancies varied from 6 weeks to 20 weeks. All six patients had pulmonary metastases, with additional liver metastasis in two patients. Among the six patients with histologically diagnosed PHM, it was found that four patients had a diploid karyotype and no maternal alleles; thus, their neoplasms actually were CHM. Maternal genome was detected in the remaining two patients consistent with a biparental origin, and these patients had a triploid karyotype. CISH findings in all patients correlated with the genotyping findings. Triploid HM had maternally derived alleles, whereas diploid HMs were purely androgenetic. CONCLUSIONS: In the current study, which may be the largest series of genetically analyzed metastatic PHMs to date, the difficulty of histologic distinction between PHM and CHM was confirmed. Molecular analysis may help to refine the classification of HM. Although the current findings support the belief that most aggressive trophoblastic diseases are derived from CHM, a small number of PHMs do progress to metastatic disease. Thus, the current study reaffirmed that all patients with HM should be followed closely irrespective of histologic subclassification.

Analysis of gestational trophoblastic disease by genotyping and chromosome in situ hybridization.

Hydatidiform mole is classified into partial and complete subtypes according to histopathological and genetic criteria. Distinction between the two by histology alone may be difficult. Genetically, a complete mole is diploid without maternal contribution, whereas a partial mole is triploid with a maternal chromosome complement. To assess the accuracy of histological diagnosis by correlating with the genetic composition, we performed fluorescent microsatellite genotyping to detect the presence or absence of maternal genome in a hydatidiform mole and carried out chromosome in situ hybridization to analyze the ploidy. For genotyping analysis, paraffin sections of 36 complete and nine partial moles, diagnosed according to histological criteria, were microdissected and DNA was separately extracted from the decidua and molar villi. Six pairs of primers that flank polymorphic microsatellite repeat sequences on five different chromosomes were used. In all, 34 cases, including 31 complete moles and three partial moles diagnosed histologically, showed no maternal contribution by genotyping; thus these could be genetically considered as complete mole. The other 11 cases (five complete moles and six partial moles previously diagnosed by histology) showed the presence of maternal contribution and were genetically diagnosed as partial moles. The genotyping results correlated with histological evaluation in 88% (37/45) of hydatidiform mole and correlated with chromosome in situ hybridization findings in all the cases, that is, triploid hydatidiform moles had maternal-derived alleles, while diploid hydatidiform moles were purely androgenetic. Compared with genetic diagnosis, histological evaluation was more reliable for the diagnosis of a complete mole (91%, 31/34) than that of a partial mole (55%, 6/11) (P=0.0033). Seven complete moles and three partial moles diagnosed genetically developed gestational trophoblastic neoplasia. To conclude, genotyping and chromosome in situ hybridization can provide reliable adjunct to histology for the classification of a hydatidiform mole, especially in cases with difficult histological evaluation and early gestational age. As a partial mole still carries a risk of developing gestational trophoblastic neoplasia, follow-up is considered necessary for both complete and partial moles.