Keiichi Isaka

Hypoxia-Inducible Factor 1 Mediates Upregulation of Telomerase (hTERT)

ABSTRACT Hypoxia occurs during the development of the placenta in the first trimester and correlates with both trophoblast differentiation and the induction of telomerase activity through hTERT expression. We sought to determine the mechanism of regulation of hTERT expression during hypoxia. We show that hypoxia-inducible factor 1α (HIF-1α) and hTERT expression in the human placenta decrease with gestational age and that these are overexpressed in preeclamptic placenta, a major complication of pregnancy. Hypoxia not only transactivates the hTERT promoter activity but also enhances endogenous hTERT expression. The hTERT promoter region between −165 and +51 contains two HIF-1 consensus motifs, and in vitro reporter assays show that these are essential for hTERT transactivation by HIF-1. Introduction of an antisense oligonucleotide for HIF-1 diminishes hTERT expression during hypoxia, indicating that upregulation of hTERT by hypoxia is directly mediated through HIF-1. Our results provide persuasive evidence that the regulation of hTERT promoter activity by HIF-1 represents a mechanism for trophoblast growth during hypoxia and suggests that this may be a generalized response to hypoxia in various human disorders including resistance to cancer therapeutics by upregulating telomerase.

Differential expression of matrilysin-1 (MMP-7), 92 kD gelatinase (MMP-9), and metalloelastase (MMP-12) in oral verrucous and squamous cell cancer.

Squamous cell carcinoma (SCC) of the oral cavity is a highly invasive tumour of stratified squamous epithelium that spreads through degradation of the basement membrane (BM) and extracellular matrix (ECM). There are currently no reliable tissue or serum markers to predict whether the tumour has metastasized at the time of diagnosis. Verrucous carcinoma (VC) of the oral cavity is a rare low‐grade variant of oral SCC that penetrates into the subepithelial connective tissue. Many matrix metalloproteinases (MMPs), such as MMP‐1, ‐2, ‐7, ‐9, ‐13, and ‐14, as well as integrin receptors have been implicated in cancer invasion. Integrin αvβ6 is induced in SCC and appears to be involved in up‐regulation of MMP‐9 expression by oral keratinocytes and promotion of their migration. The aim of this study was to investigate whether the pattern of MMP expression or that of αvβ6 integrin contributes to the differences in the biological behaviour of oral SCC and VC. The results show that the less aggressive nature of oral VC may be connected to its MMP expression profile. Typically, VCs were devoid of epithelial MMP‐3, ‐7, ‐9, ‐12 and ‐13 expression, compared with SCCs. MMP‐19 was expressed by epithelial keratinocytes in hyperproliferative areas of verrucous hyperplasia, VC, and SCC, but was absent in the invasive cancer cell nests of SCC. MMP‐26 was expressed by hyperproliferative keratinocytes in VC as well as by invasive cancer cells in SCCs. MMP‐10 was expressed widely in the epithelium of all SCC specimens. αvβ6 integrin expression was also detected in some cases of epithelial hyperplasia but was significantly more abundant in cancers at the invasive front. The absence of MMP‐7, ‐9 and ‐12 from epithelial cells may serve as a good prognostic marker of non‐invasive oral carcinoma. Blocking the activity of invasion‐specific MMPs or αvβ6 integrin might offer novel therapeutic modalities in early‐stage oral carcinoma. Copyright

HIF-1-mediated activation of telomerase in cervical cancer cells

Hypoxia-inducible factor 1 (HIF-1) is a key regulator of O2 homeostasis, which regulates the expression of several genes linked to angiogenesis and energy metabolism. Tumor hypoxia has been shown to be associated with poor prognosis in a variety of tumors, and HIF-1 induced by hypoxia plays pivotal roles in tumor progression. The presence of putative HIF-1-binding sites on the promoter of human telomerase reverse transcriptase gene (hTERT) prompted us to examine the involvement of HIF-1 in the regulation of hTERT and telomerase in tumor hypoxia. The telomeric repeat amplification protocol (TRAP) assay revealed that hypoxia activated telomerase in cervical cancer ME180 cells, with peak induction at 24–48 h of hypoxia. Notably, hTERT mRNA expression was upregulated at 6–12 h of hypoxia, concordant with the elevation of HIF-1 protein levels at 6 h. hTERT protein levels were subsequently upregulated at 24 h and later. Luciferase assays using reporter plasmids containing hTERT core promoter revealed that hTERT transcription was significantly activated in hypoxia and by HIF-1 overexpression, and that the two putative binding sites within the core promoter are responsible for this activation. Chromatin immunoprecipitation assay identified the specific binding of HIF-1 to these sites (competing with c-Myc), which was enhanced in hypoxia. The present findings suggest that hypoxia activates telomerase via transcriptional activation of hTERT, and that HIF-1 plays a critical role as a transcription factor. They also suggest the existence of novel mechanisms of telomerase activation in cancers, and have implications for the molecular basis of hypoxia-induced tumor progression and HIF-1-based cancer gene therapy.

Human arylhydrocarbon receptor repressor (AHRR) gene: genomic structure and analysis of polymorphism in endometriosis

AbstractThe diversity of biological effects resulting from exposure to dioxin may reflect the ability of this environmental pollutant to alter gene expression by binding to the arylhydrocarbon receptor (AHR) gene and related genes. AHR function may be regulated by structural variations in AHR itself, in the AHR repressor (AHRR), in the AHR nuclear translocator (ARNT), or in AHR target molecules such as cytochrome P-4501A1 (CYP1A1) and glutathione S-transferase. Analysis of the genomic organization of AHRR revealed an open reading frame consisting of a 2094-bp mRNA encoded by ten exons. We found one novel polymorphism, a substitution of Ala by Pro at codon 185 (GCC to CCC), in exon 5 of the AHRR gene; among 108 healthy unrelated Japanese women, genotypes Ala/Ala, Ala/Pro, and Pro/Pro were represented, respectively, by 20 (18.5%), 49 (45.4%), and 39 (36.1%) individuals. We did not detect previously published polymorphisms of ARNT (D511N) or the CYP1A1 promoter (G-469A and C-459T) in our subjects, suggesting that these polymorphisms are rare in the Japanese population. No association was found between uterine endometriosis and any polymorphisms in the AHRR, AHR, ARNT, or CYP1A1 genes analyzed in the present study.

Increased heterogeneity of chromosome 17 aneuploidy in endometriosis

OBJECTIVE Endometriosis is a complex gynecologic disorder that may display features similar to malignancy, including aggressive growth and localized invasion of the myometrium or spread to various organs outside the uterus. Molecular studies of cancer have demonstrated that genomic instability involving chromosome 17 plays a role in the development and progression of various tumor types. These involve gain and/or loss, deletions, and mutations of candidate tumor suppressor genes (eg, BRCA1 and p53 ) on chromosome 17. STUDY DESIGN We used a 2-color fluorescence in situ hybridization method for analysis of endometriotic and normal archival tissue. Centromere-specific and locus-specific p53 probes localized to chromosome 17 were selected to study 8 patients with late-stage (severe) endometriosis. Single cells localized to endometriotic lesions or normal endometrial glands were analyzed and identified as normal or abnormal on the basis of the distribution of fluorescence in situ hybridization signals. RESULTS Overall, chromosome 17 aneuploidy was significantly greater (P <.05) in the endometriosis specimens (mean of 65%) than in normal endometrial cells (mean of 25%). No significant difference (P =.1071) in the distribution of fluorescence in situ hybridization signals was observed among the 5 normal endometrial specimens. However, significant differences (P <. 0001) were observed between the 8 endometriosis tissue specimens. CONCLUSION We found increased heterogeneity of chromosome 17 aneuploidy in endometriosis. These findings support a multistep pathway involving somatic genetic alterations in the development and progression of this common disease.

Expression of a Novel Human Gene, Human Wings Apart-Like (hWAPL), Is Associated with Cervical Carcinogenesis and Tumor Progression

In Drosophila melanogaster, the wings apart-like (wapl) gene encodes a protein that regulates heterochromatin structure. Here, we characterize a novel human homologue of wapl (termed human WAPL; hWAPL). The hWAPL mRNA was predominantly expressed in uterine cervical cancer, with weak expression in all other normal and tumor tissues examined. hWAPL expression in benign epithelia was confined to the basal cell layers, whereas in dysplasias it increasingly appeared in more superficial cell layers and showed a significant correlation with severity of dysplasia. Diffuse hWAPL expression was found in all invasive squamous cell carcinomas examined. In addition, NIH3T3 cells overexpressing hWAPL developed into tumors on injection into nude mice. Furthermore, repression of hWAPL expression by RNA interference induced cell death in SiHa cells. These results demonstrate that hWAPL is associated with cell growth, and the hWAPL expression may play a significant role in cervical carcinogenesis and tumor progression.

Matrix metalloproteinase‐26 is expressed in human endometrium but not in endometrial carcinoma

The human matrix metalloproteinase (MMP)‐26, also called matrilysin‐2 or endometase, has been isolated as a matrilysin (MMP‐7) homolog. Matrix metalloproteinase‐26 was expressed in tissue samples from the placenta and endometrial tumors and its expression may be related to the development of endometrial carcinomas.

USP15 plays an essential role for caspase-3 activation during Paclitaxel-induced apoptosis.

Paclitaxel (also known as Taxol) is a well-known anticancer agent that blocks cell mitosis and kills tumor cells, and is often used in clinic to treat cancers. Despite the success of Paclitaxel, the development of drug resistance prevents its clinical applicability. Here, we screened an siRNA library against the entire human genomes using HeLa cells, and have find that lack of USP15 (ubiquitin-specific protease 15) causes Paclitaxel resistance. We also observed the decreased expression of USP15 in Paclitaxel-resistant human ovarian cancer samples. In addition, we have demonstrated that USP15 plays an essential role for stability and activity of caspase-3 during Paclitaxel-induced apoptosis. Thus, USP15 may be a candidate diagnostic marker and therapeutic target for Paclitaxel-resistant cancers.

Umbilical Cord Milking Stabilizes Cerebral Oxygenation and Perfusion in Infants Born before 29 Weeks of Gestation

OBJECTIVE To investigate the effects of umbilical cord milking at birth on cerebral perfusion and systemic perfusion in very low birth weight (VLBW) infants. STUDY DESIGN Cerebral tissue oxygenation index and cerebral fractional tissue oxygen extraction were monitored in 50 stable VLBW infants (gestational age <29 weeks, birth weight <1250 g), with 26 allocated to the milked group and 24 to the control group. We used near-infrared spectroscopy 3-6, 12, 18, 24, 36, 48, and 72 hours after birth. Left ventricular end-diastolic dimension, left ventricular ejection fraction, left ventricle (LV) Tei index (measurement of left ventricular systolic and diastolic function), left ventricular cardiac output, and superior vena cava flow were measured concurrently using echocardiography. RESULTS There were no significant differences in gestational age and birth weight between the 2 groups. Hematocrit, left ventricular end-diastolic dimension, left ventricular cardiac output, and superior vena cava flow were higher in the milked group than in the control group, with improvement in the LV Tei index despite the absence of left ventricular ejection fraction changes within 24 hours after birth. Tissue oxygenation index increased and cerebral fractional tissue oxygen extraction decreased in the milked group within 24 hours after birth. CONCLUSION Umbilical cord milking stabilized cerebral oxygenation and perfusion in VLBW infants by improving LV diastolic function by increasing LV preload.

The correlation of TERT expression with c-myc expression in cervical cancer

Recently putative catalytic telomerase subunit was identified as telomerase reverse transcriptase (TERT). Several reports showed that TERT expression correlated with telomerase activity. It has also been found that c-myc can induce telomerase activation through TERT expression. We examined expression of TERT and c-myc and their correlation in cervical cancers by reverse transcription-polymerase chain reaction (RT-PCR). It was found that TERT and c-myc expression was observed mostly in malignancies and expression of c-myc was concordant for positivity and negativity with TERT. These results support recent studies that c-myc expression is closely associated with TERT and telomerase activity. c-myc up-regulation may play an important role in activation of TERT and telomerase.