STK15 polymorphisms and association with risk of invasive ovarian cancer.
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STK15 is a putative oncogene that codes for a centrosome-associated, serine/threonine kinase, the normal function of which is to ensure accurate segregation of chromosomes during mitosis. Amplification of STK15 has been reported in ovarian tumors, suggesting a role in ovarian cancer pathology. STK15 is polymorphic with two single nucleotide substitutions (449t/a and 527g/a) in evolutionarily conserved regions causing amino acid changes (F31I and V57I). Two other nucleotide substitutions (287c/g and 1891g/c) of unknown significance are in 5' and 3' untranslated regions (UTR), respectively. To learn more about the involvement of STK15 in ovarian cancer, we genotyped and haplotyped these polymorphisms in three population-based ovarian cancer case-control studies from the United Kingdom, United States, and Denmark with 1,821 combined cases and 2,467 combined controls and calculated risks for developing ovarian cancer. Genotypes of individual polymorphisms in control groups of the United Kingdom, United States, and Denmark conformed to Hardy-Weinberg equilibrium. In combined cases and combined controls, rare allele frequencies were 0.23 and 0.21 for I31, 0.16 and 0.17 for I57, 0.08 and 0.07 for 5' UTR g, and 0.25 and 0.24 for 3' UTR c, respectively. Using FF common homozygotes of F31I as comparator, there was increased ovarian cancer risk to FI heterozygotes (odds ratio, 1.18; 95% confidence interval, 1.01-1.36), II homozygotes (odds ratio, 1.25; 95% confidence interval, 0.89-1.75), and I31 allele carriers (odds ratio, 1.17; 95% confidence interval, 1.02-1.35) in the combined group data. For either V57I, 5' UTR C/G, or 3' UTR G/C, all genotypic ovarian cancer risks were essentially in unity relative to their respective common homozygotes, VV, cc, or gg. Haplotype analysis of combined group data revealed seven haplotypes with frequencies between 0.02 and 0.5, with c-F-V-g the most common. None of the haplotype-specific risks significantly differed from unity relative to c-F-V-g. These results suggest a model of dominant inheritance of ovarian cancer risk by the I31 allele of F31I and that the I31 allele may be a common ovarian cancer susceptibility allele of low penetrance. (+info)
G2 cell cycle arrest, down-regulation of cyclin B, and induction of mitotic catastrophe by the flavoprotein inhibitor diphenyleneiodonium.
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Because proliferation of eukaryotic cells requires cell cycle-regulated chromatid separation by the mitotic spindle, it is subject to regulation by mitotic checkpoints. To determine the mechanism of the antiproliferative activity of the flavoprotein-specific inhibitor diphenyleneiodonium (DPI), I have examined its effect on the cell cycle and mitosis. Similar to paclitaxel, exposure to DPI causes an accumulation of cells with a 4N DNA content. However, unlike the paclitaxel-mediated mitotic block, DPI-treated cells are arrested in the cell cycle prior to mitosis. Although DPI-treated cells can arrest with fully separated centrosomes at opposite sides of the nucleus, these centrosomes fail to assemble mitotic spindle microtubules and they do not accumulate the Thr(288) phosphorylated Aurora-A kinase marker of centrosome maturation. In contrast with paclitaxel-arrested cells, DPI impairs cyclin B1 accumulation. Release from DPI permits an accumulation of cyclin B1 and progression of the cells into mitosis. Conversely, exposure of paclitaxel-arrested mitotic cells to DPI causes a precipitous drop in cyclin B and Thr(288) phosphorylated Aurora-A levels and leads to mitotic catastrophe in a range of cancerous and noncancerous cells. Hence, the antiproliferative activity of DPI reflects a novel inhibitory mechanism of cell cycle progression that can reverse spindle checkpoint-mediated cell cycle arrest. (+info)
Overexpression of Aurora-A contributes to malignant development of human esophageal squamous cell carcinoma.
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PURPOSE: Aurora-A/STK15/BTAK, a centrosome-associated oncogenic protein, is implicated in the control of mitosis. Overexpression of Aurora-A has been shown to result in chromosomal aberration and genomic instability. Multiple lines of evidence indicate that Aurora-A induces cell malignant transformation. In the current study, we are interested in investigating the expression of Aurora-A in human esophageal squamous cell carcinoma (ESCC) and characterizing the association of Aurora-A with ESCCmalignant progression. EXPERIMENTAL DESIGN: Aurora-A protein expression was examined in 84 ESCC tissues and 81 paired normal adjacent tissues by either immunohistochemistry or Western blot analysis. In addition, a gene-knockdown small interfering RNA technique was used in ESCC cells to investigate whether Aurora-A contributes to the ability of a tumor to grow invasively. RESULTS: The amount of Aurora-A protein in ESCC was considerably higher than that in normal adjacent tissues. Overexpression of Aurora-A was observed in 57 of 84 (67.5%) ESCC samples. In contrast, <2% of normal adjacent tissue displayed high expression of Aurora-A. Interestingly, overexpression of Aurora-A seemed to correlate with the invasive malignancy of ESCC. Disruption of endogenous Aurora-A using small interfering RNA technique substantially suppressed cell migrating ability. CONCLUSION: The findings presented in this report show that Aurora-A expression is elevated in human esophageal squamous cell carcinoma and is possibly associated with tumor invasion, indicating that overexpression of Aurora-A may contribute to ESCC occurrence and progression. (+info)
Synergistic effects of STK15 gene polymorphisms and endogenous estrogen exposure in the risk of breast cancer.
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STK15 is a member of a family of serine/threonine kinases that act as key regulators of chromosome segregation and cytokinesis. Over expression of the STK15 gene leads to centrosome amplification, chromosomal instability, aneuploidy, and transformation. It has been reported that the 91T --> A (Phe --> Ile at codon 31) polymorphism in the STK15 gene affects the function of this gene. We hypothesized that this polymorphism may interact with endogenous estrogen exposure in the risk of breast cancer and evaluated this hypothesis in a population-based, case-control study conducted among Chinese women in Shanghai. Genotyping assays were completed for 1,102 incident cases and 1,186 community controls. Participation and blood donation rates were over 90% and 80%, respectively. Elevated risks of breast cancer were found to be associated with the Phe/Ile [odds ratio (OR), 1.3; 95% confidence interval (CI), 1.0-1.7] and Ile/Ile (OR, 1.2; 95% CI, 0.9-1.6) genotypes at codon 31 of the STK15 gene, although the ORs were not statistically significant. The risk associated with this polymorphism was modified by factors related to endogenous estrogen exposure, such as high body mass index (BMI), high waist-to-hip ratio, long duration of lifetime menstruation, or long duration of menstruation before first live birth. In particular, a statistically significant interaction was found between BMI and the STK15 Phe(31)Ile polymorphism (P = 0.02) and a positive association with breast cancer risk for the Ile allele was found only among overweight (BMI >/= 25 kg/m(2)) women with adjusted ORs (95% CIs) of 3.3 (1.4-7.7) and 4.1 (1.7-9.8) associated with the Phe/Ile and Ile/Ile genotypes (Pfor trend <0.01), respectively. The findings from this study are consistent with the evidence from invitro and in vivo experiments, implicating an etiologic role of the STK15 gene in human breast cancer, and provide evidence for the modifying effects of genetic background on human cancer risk. (+info)
Estrogen mediates Aurora-A overexpression, centrosome amplification, chromosomal instability, and breast cancer in female ACI rats.
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Estrogens play a crucial role in the causation and development of sporadic human breast cancer (BC). Chromosomal instability (CIN) is a defining trait of early human ductal carcinoma in situ (DCIS) and is believed to precipitate breast oncogenesis. We reported earlier that 100% of female ACI (August/Copenhagen/Irish) rats treated with essentially physiological serum levels of 17beta-estradiol lead to mammary gland tumors with histopathologic, cellular, molecular, and ploidy changes remarkably similar to those seen in human DCIS and invasive sporadic ductal BC. Aurora-A (Aur-A), a centrosome kinase, and centrosome amplification have been implicated in the origin of aneuploidy via CIN. After 4 mo of estradiol treatment, levels of Aur-A and centrosomal proteins, gamma-tubulin and centrin, rose significantly in female ACI rat mammary glands and remained elevated in mammary tumors at 5-6 mo of estrogen treatment. Centrosome amplification was initially detected at 3 mo of treatment in focal dysplasias, before DCIS. At 5-6 mo, 90% of the mammary tumor centrosomes were amplified. Comparative genomic hybridization revealed nonrandom amplified chromosome regions in seven chromosomes with a frequency of 55-82% in 11 primary tumors each from individual rats. Thus, we report that estrogen is causally linked via estrogen receptor alpha to Aur-A overexpression, centrosome amplification, CIN, and aneuploidy leading to BC in susceptible mammary gland cells. (+info)
Identification of V23RalA-Ser194 as a critical mediator for Aurora-A-induced cellular motility and transformation by small pool expression screening.
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Human Aurora kinases have three gene family members: Aurora-A, Aurora-B, and Aurora-C. It is not yet established what the specificity of these kinases are and what signals relayed by their reactions. Therefore, we employed small pool expression screening to search for downstream substrates of Aurora-A. Interestingly, all of the identified Aurora-A substrates were resistant to serve as substrates for Aurora-B or Aurora-C, suggesting that these Aurora family members may have distinct substrate specificity for propagation of diverse signaling pathways, even though they share a conserved catalytic kinase domain. Of the candidate substrates, Aurora-A could increase the functional activity of RalA. Mutational analysis revealed that RalA-Ser194 was the phosphorylation site for Aurora-A. Ectopic expression of V23RalA-WT could enhance collagen I-induced cell migration and anchorage-independent growth in Madin-Darby canine kidney (MDCK) Aurora-A stable cell lines. In contrast, overexpression of V23RalA-S194A in MDCK Aurora-A-stable cell lines abolished the intrinsic migration and transformation abilities of Aurora-A. To our knowledge, this is the first systematic search for the downstream substrates of Aurora-A kinase. Moreover, these results support the notion that Aurora-A may act in concert with V23RalA through protein phosphorylation on Ser194 to promote collagen I-induced cell motility and anchorage-independent growth in MDCK epithelial cells. (+info)
The clinical significance of Aurora-A/STK15/BTAK expression in human esophageal squamous cell carcinoma.
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PURPOSE: Aurora-A/STK15/BTAK (Aurora-A) encodes a Serine/Threonine kinase associated with chromosomal distribution, and its up-regulation induces chromosomal instability thereby leading to aneuploidy and cell transformation in several types of cancer. In this study, we investigated the role of Aurora-A in human esophageal squamous cell carcinoma (ESCC). EXPERIMENTAL DESIGN: The expression levels of Aurora-A mRNA were compared in 33 ESCC tissues with that in corresponding normal esophageal epithelium by semiquantitative reverse transcription-PCR, and the distribution patterns and expression levels of Aurora-A protein were immunohistochemically investigated in the ESCC tumors of 142 patients. The results were then separately compared with the clinicopathologic findings of the patients, and the expression of Aurora-A was examined in nine ESCC cell lines and a normal esophageal epithelial cell line using Western blot analysis. RESULTS: The up-regulation of Aurora-A mRNA was found in 30% (10 of 33) of the tumors by semiquantitative reverse transcription-PCR, and protein up-regulation was found in 53% (75 of 142) of the patients by immunohistochemistry. mRNA and protein up-regulation of Aurora-A were correlated with distant lymph node metastasis (P = 0.05 and P = 0.04, respectively), and patients with Aurora-A mRNA or protein up-regulation had a poorer prognosis (P = 0.003 and P = 0.0009, respectively). Furthermore, multivariate analysis revealed that up-regulation of the Aurora-A protein was an independent prognostic factor. In addition, Aurora-A expression in all ESCC cell lines was higher than that in a normal esophageal epithelial cell line. CONCLUSIONS: The up-regulation of Aurora-A expression may reflect the malignant behavior of ESCC and may prove useful information as a prognostic factor for ESCC patients. (+info)
Aurora-A/STK15 T+91A is a general low penetrance cancer susceptibility gene: a meta-analysis of multiple cancer types.
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STK15 (Aurora-A) is a serine/threonine kinase involved in mitotic chromosomal segregation. A genetic variant in STK15 T+91A (resulting in the amino acid substitution F31I) is associated with increased aneuploidy in colon tumors and cell transformation in vitro. Since this polymorphism plays a role in mitotic control-a process critical for all cancer types-we conducted association analyses for risk of cancer development of the colon, breast, prostate, skin, lung and esophagus in 10 independent case-control populations. We carried out a meta-analysis of these 10 case-control studies together with 5 additional published studies for a total of 9549 cases of breast, colon, ovarian, prostate, lung, esophageal and non-melanoma skin cancer and 8326 population or hospital-based controls. Meta-analysis of three colorectal cancer studies showed an increased risk in T+91A homozygotes (OR=1.50; 95% CI of 1.14-1.99). Meta-analysis of four breast cancer studies showed increased risk for T+91A homozygotes (OR=1.35, 95% CI of 1.12-1.64). The results of the multiple cancer type meta-analysis for all 15 studies combined were significant for cancer risk in both homozygotes and heterozygotes. The T+91A heterozygotes show an OR of 1.10 (95% CI of 1.03-1.18, P-value=0.006) and the T+91A homozygotes show an OR of 1.40 (95% CI of 1.22-1.59, P-value<0.001) for cancer risk. These results confirm that the STK15 T+91A variant is a low penetrance cancer susceptibility allele affecting multiple cancer types, and provide genetic evidence from large-scale human population studies that genetic stability at the chromosome level is an important determinant of cancer susceptibility. The data also underline the advantages of comparative association studies involving study populations from different ethnic groups for determination of disease risk. (+info)