Regulation of myeloid leukemia factor-1 interacting protein (MLF1IP) expression in glioblastoma

Rat and Mouse Brain Tumor Models for Experimental Neuro-Oncology Research

Rodent brain tumor models have been useful for developing effective therapies for glioblastomas (GBMs). In this review, we first discuss the 3 most commonly used rat brain tumor models, the C6, 9L, and F98 gliomas, which are all induced by repeated injections of nitrosourea to adult rats. The C6 glioma arose in an outbred Wistar rat and its potential to evoke an alloimmune response is a serious limitation. The 9L gliosarcoma arose in a Fischer rat and is strongly immunogenic, which must be taken into consideration when using it for therapy studies. The F98 glioma may be the best of the 3 but it does not fully recapitulate human GBMs because it is weakly immunogenic. Next, we discuss a number of mouse models. The first are human patient-derived xenograft gliomas in immunodeficient mice. These have failed to reproduce the tumor-host interactions and microenvironment of human GBMs. Genetically engineered mouse models recapitulate the molecular alterations of GBMs in an immunocompetent environment and “humanized” mouse models repopulate with human immune cells. While the latter are rarely isogenic, expensive to produce, and challenging to use, they represent an important advance. The advantages and limitations of each of these brain tumor models are discussed. This information will assist investigators in selecting the most appropriate model for the specific focus of their research.

Overexpression of MLF1IP promotes colorectal cancer cell proliferation through BRCA1/AKT/p27 signaling pathway

BACKGROUND AND OBJECTIVE

MLF1IP has been correlated with the progression and prognosis of a few tumors. However, the role of MLF1IP in colorectal cancer remains unclear. Here, we examined the expression and function of MLF1IP in colorectal cancer and investigated possible molecular mechanisms.

METHODS

MLF1IP expressions in colorectal cancer tissues and cell lines were detected by quantitative real-time PCR, western blotting, and immunohistochemistry. In vitro and in vivo assays were performed to explore the function and underlying molecular mechanisms of MLF1IP in colorectal cancer.

RESULTS

The expression levels of MLF1IP were significantly up-regulated in colorectal cancer tissues and CRC cell lines (P < 0.05). High expression of MLF1IP was significantly associated with TNM stage, T classification, lymph node involvement, distant metastasis, and poor patient survival (all P < 0.05). Overexpressing MLF1IP promoted while silencing MLF1IP inhibited, the proliferation and clonogenicity of colorectal cancer cells and tumorigenicity in NOD/SCID mice (P < 0.05). In addition, we demonstrated that the pro-proliferative effect of MLF1IP on colorectal cancer cells was associated with mediating the G1-to-S phase transition. MLF1IP knockdown enhanced BRCA1 activity concomitantly with p-AKT downregulation and p27 upregulation, while overexpression of MLF1IP has the opposite effect. Moreover, upregulation of BRCA1 can partially abolish the proliferative activity of MLF1IP.

CONCLUSIONS

These findings suggest that MLF1IP may promote proliferation and tumorigenicity of colorectal cancer cells via BRCA1/AKT/p27 signaling axis, and thereby provides potential targets for colorectal cancer therapy.

Centromere protein U enhances the progression of bladder cancer by promoting mitochondrial ribosomal protein s28 expression

Bladder cancer is one of the most common types of cancer. Most gene mutations related to bladder cancer are dominantly acquired gene mutations and are not inherited. Previous comparative transcriptome analysis of urinary bladder cancer and control samples has revealed a set of genes that may play a role in tumor progression. Here we set out to investigate further the expression of two candidate genes, centromere protein U (CENPU) and mitochondrial ribosomal protein s28 (MRPS28) to better understand their role in bladder cancer pathogenesis. Our results confirmed that CENPU is up-regulated in human bladder cancer tissues at mRNA and protein levels. Gain-of-function and loss-of-function studies in T24 human urinary bladder cancer cell line revealed a hierarchical relationship between CENPU and MRPS28 in the regulation of cell viability, migration and invasion activity. CENPU expression was also up-regulated in in vivo nude mice xenograft model of bladder cancer and mice overexpressing CENPU had significantly higher tumor volume. In summary, our findings identify CENPU and MRPS28 in the molecular pathogenesis of bladder cancer and suggest that CENPU enhances the progression of bladder cancer by promoting MRPS28 expression.

CENP-50 is required for papilloma development in the two-stage skin carcinogenesis model

CENP‐50/U is a component of the CENP‐O complex (CENP‐O/P/Q/R/U) and localizes to the centromere throughout the cell cycle. Aberrant expression of CENP‐50/U has been reported in many types of cancers. However, as Cenp‐50/U‐deficient mice die during early embryogenesis, its functions remain poorly understood in vivo. To investigate the role of Cenp‐50/U in skin carcinogenesis, we generated Cenp‐50/U conditional knockout (K14Cre^ER‐Cenp‐50/U^fl/fl) mice and subjected them to the 7,12‐dimethylbenz(a)anthracene (DMBA)/terephthalic acid (TPA) chemical carcinogenesis protocol. As a result, early‐stage papillomas decreased in Cenp‐50/U‐deficient mice. In contrast, Cenp‐50/U‐deficient mice demonstrated almost the same carcinoma incidence as control mice. Furthermore, mRNA expression analysis using DMBA/TPA‐induced papillomas and carcinomas revealed that Cenp‐50/U expression levels in papillomas were significantly higher than in carcinomas. These results suggest that Cenp‐50/U functions mainly in early papilloma development and it has little effect on malignant conversion.

Proneural and mesenchymal glioma stem cells display major differences in splicing and lncRNA profiles

Therapy resistance and recurrence in high-grade gliomas are driven by their populations of glioma stem cells (GSCs). Thus, detailed molecular characterization of GSCs is needed to develop more effective therapies. We conducted a study to identify differences in the splicing profile and expression of long non-coding RNAs in proneural and mesenchymal GSC cell lines. Genes related to cell cycle, DNA repair, cilium assembly, and splicing showed the most differences between GSC subgroups. We also identified genes distinctly associated with survival among patients of mesenchymal or proneural subgroups. We determined that multiple long non-coding RNAs with increased expression in mesenchymal GSCs are associated with poor survival of glioblastoma patients. In summary, our study established critical differences between proneural and mesenchymal GSCs in splicing profiles and expression of long non-coding RNA. These splicing isoforms and lncRNA signatures may contribute to the uniqueness of GSC subgroups, thus contributing to cancer phenotypes and explaining differences in therapeutic responses.

Reduced CENPU expression inhibits lung adenocarcinoma cell proliferation and migration through PI3K/AKT signaling

CENPU (centromere protein U), a centromere component essential for mitosis, relates with some cancers progression. However, it is not well illustrated in lung adenocarcinoma (LAC). Here, we aimed to investigate the potential effect of CENPU on LAC progression and prognosis. In this experiment, expression level of CENPU and association between its expression and LAC patients' clinicopathological characteristics and prognosis were analyzed. The proliferation, migration and invasive abilities of LAC cells were determined by CCK-8, colony formation, transwell assays. Western blot was used to detect PI3K/AKT signaling key proteins. We found CENPU level was overexpressed in LAC tissues on comparing normal tissues. Moreover, CENPU overexpression correlated with clinicopathological variables and predicted an independent prognostic indicator in LAC patients. Functionally, CENPU downregulation significantly inhibited LAC cell proliferation, migration and invasion in, which was possibly mediated by PI3K/AKT pathway inactivation. Our findings insinuate targeting CENPU may be a potential therapeutic strategy for LAC.

Centromere protein U expression promotes non-small-cell lung cancer cell proliferation through FOXM1 and predicts poor survival

Purpose

Centromere protein U (CENPU) abnormally exhibits high expression in various types of human tumor tissues and participates in tumor progression; however, its expression pattern and biological function in lung cancer have not yet been elucidated. In the present study, we explored the clinical significance and biological function of CENPU in lung cancer.

Materials and methods

The Cancer Genome Atlas (TCGA) data analyses, quantitative real-time PCR (RT-PCR), and Western blotting were performed to quantify CENPU and FOXM1 expression in non-small-cell lung cancer (NSCLC) samples. Survival data were obtained from Kaplan–Meier plotter or PROGgene V2 prognostic database. The function of CENPU in lung cancer cell proliferation was determined using 5-ethynyl-2′-deoxyuridine (EdU), Cell Counting Kit-8 (CCK-8), and cell cycle assays, and the underlying mechanism was determined through bioinformatic analyses and validated by in vitro siRNA or plasmid transfection experiments.

Results

CENPU was abnormally overexpressed in NSCLC samples compared with matched paired normal tissues. Higher expression of CENPU predicted worse overall survival (OS) and relapse-free survival (RFS) in NSCLC patients. Knockdown of CENPU expression by siRNA significantly inhibited proliferation and delayed cell cycle progression of lung cancer cells. To figure out the mechanism, bioinformatic analyses were performed and the results showed that the transcription factor, FOXM1, positively correlated with CENPU. Further in vitro experiments indicated that FOXM1 was the possible downstream transcription factor of CENPU as the knockdown of CENPU led to lower expression of FOXM1 and the overexpression of FOXM1 significantly reversed the inhibition of proliferation caused by CENPU knockdown. Furthermore, FOXM1 was highly expressed in NSCLC. The knockdown of FOXM1 also attenuated proliferation and induced G1 arrest in lung cancer cells.

Conclusion

CENPU was highly expressed in NSCLC tissues, wherein it promoted lung cancer cell proliferation via the transcription factor, FOXM1, which could be a potential target for therapeutic strategies.

The effect of centromere protein U silencing by lentiviral mediated RNA interference on the proliferation and apoptosis of breast cancer

Centromere protein U (CENPU) is a novel transcriptional repressor that is associated with different types of cancer. However, its function in breast cancer is poorly understood. In the present study, it was identified that CENPU was highly expressed in breast cancer tissues compared with expression in normal breast tissues (P=0.001). Furthermore, the CENPU mRNA level in tumors was often elevated, compared with the matched adjacent normal breast cancer tissue specimens in the dataset from The Cancer Genome Atlas database (n=106; P<0.001). To understand the function of CENPU in human breast carcinogenesis, its effects on the proliferation, apoptosis and cell cycle progression of MDA-MB-231 cells were examined using the lentiviral-mediated CENPU knockdown approach. The RNA and protein expression levels in the transfected cells were monitored using reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. The mRNA and protein expression levels of the CENPU gene were significantly lower in the CENPU-shRNA transfected cells than in the control (P<0.01), indicating successful gene expression knockdown. Post-transfection, cell counting and MTT analysis revealed that the proliferation activity was significantly suppressed in CENPU knockdown cells relative to the control (P<0.01). Additionally, fluorescence activated cell sorting analysis revealed that the (G2+S) phase fraction was significantly declined in CENPU knockdown cells relative to the control; while the G1 phase fraction was significantly increased (P<0.01) and the percentage of the apoptotic cells was significantly increased (P<0.01). In conclusion, downregulation of CENPU gene expression may inhibit cell proliferation and cell cycle progression, and increase the apoptosis of the breast cancer cells. These results suggested a possible function of this protein in breast cancer pathogenesis and prognosis.

Centromere protein U is a potential target for gene therapy of human bladder cancer

To investigate the role of centromere protein U (CENPU) in human bladder cancer (BCa), CENPU gene expression was evaluated in human BCa tissues. We used real-time quantitative PCR (qPCR) and found that CENPU gene expression in human BCa tissues was higher compared to that observed in cancer-adjacent normal tissues. High CENPU expression was found to be strongly correlated with tumor size and TNM stage. Kaplan-Meier survival analysis indicated that high CENPU levels were associated with reduced survival. We used a lentivirus to silence endogenous CENPU gene expression in the BCa T24 cell line. CENPU knockdown was confirmed by qPCR. Cellomic imaging and BrdU assays showed that cell proliferation was significantly reduced in the CENPU-silenced cells compared to that noted in the control cells. Flow cytometry revealed that in the CENPU-silenced cells the cell cycle was arrested at the G1 phase relative to that in the control cells. In addition, apoptosis was significantly increased in the CENPU-silenced cells. Giemsa staining showed that CENPU-silenced cells, compared to control cells, displayed a significantly lower number of cell colonies. The genome-wide effect of CENPU knockdown showed that a total of 1,274 differentially expressed genes was found, including 809 downregulated genes and 465 upregulated genes. Network analysis by Ingenuity Pathway Analysis (IPA) resulted in 25 distinct signaling pathways, including the top-ranked network: ‘Cellular compromise, organismal injury and abnormalities, skeletal and muscular disorders’. In-depth IPA analysis revealed that CENPU was associated with the HMGB1 signaling pathway. qPCR and western blot analysis demonstrated that in the HMGB1 signaling pathway, CENPU knockdown downregulated expression levels of ILB, CXCL8, RAC1 and IL1A. In conclusion, our data may provide a potential pathway signature for therapeutic targets with which to treat BCa.

MLF1IP is correlated with progression and prognosis in luminal breast cancer

Myeloid leukemia factor 1-interacting protein (MLF1IP) has been found to be involved in the progression of several malignancies. The potential correlation between MLF1IP and clinical outcome in patients with luminal breast cancer, however, remains unknown. In the present study, we demonstrated that MLF1IP was significantly upregulated in luminal breast cancer tissue compared with adjacent normal tissue both in validated cohort and TCGA cohort. Upregulated expression of MLF1IP was correlated with more often lymph node metastasis and negative progesterone receptor expression in TCGA cohorts. Kaplan-Meier analysis indicated that patients with high MLF1IP expression had significantly lower overall survival. Moreover, multivariate analysis revealed that high MLF1IP expression was independent high risk factor as well as old age (>60) and distant metastasis. This study provides new insights and evidences that MLF1IP over-expression plays important roles in progression of luminal breast cancer. However, the precise cellular mechanisms for MLF1IP in luminal breast cancer need to be further explored.

MLF1 interacting protein: a potential gene therapy target for human prostate cancer?

Here, we investigated the role of one gene that has been previously associated with human prostate carcinoma cells-myelodysplasia/myeloid leukemia factor 1 interacting protein (MLF1IP)-in order to better ascertain its role in human prostate carcinogenesis. The prostate cancer cell line PC-3 was lentivirally transfected to silence endogenous MLF1IP gene expression, which was confirmed by real-time quantitative PCR (RT-qPCR). Cellomics ArrayScan VTI imaging and MTT assays were conducted to assess cell proliferation. Cell cycle phase arrest and apoptosis were assayed by flow cytometry. Colony formation was assessed by fluorescence microscopy. MLF1IP gene expression was also analyzed by RT-qPCR in sixteen prostate cancer tissue samples and six healthy control prostate tissue samples from human patients. Cell proliferation was significantly inhibited in MLF1IP-silenced cells relative to control cells. G1 phase, S and G2/M phase cell counts were not significantly changed in MLF1IP-silenced cells relative to control cells. Apoptosis was significantly increased in MLF1IP-silenced cells, while MLF1IP-silenced cells displayed a significantly reduced number of cell colonies, compared to control cells. The 16 human prostate cancer tissue samples revealed no clear upregulation or downregulation in MLF1IP gene expression. MLF1IP significantly promotes prostate cancer cell proliferation and colony formation and significantly inhibits apoptosis without affecting cell cycle phase arrest. Further study is required to conclusively determine whether MLF1IP is upregulated in human prostate cancer tumors and to determine the precise cellular mechanism(s) for MLF1IP in prostate carcinogenesis.

Military personnel with chronic symptoms following blast traumatic brain injury have differential expression of neuronal recovery and epidermal growth factor receptor genes

Objective: Approximately one-quarter of military personnel who deployed to combat stations sustained one or more blast-related, closed-head injuries. Blast injuries result from the detonation of an explosive device. The mechanisms associated with blast exposure that give rise to traumatic brain injury (TBI), and place military personnel at high risk for chronic symptoms of post-concussive disorder (PCD), post-traumatic stress disorder (PTSD), and depression are not elucidated.

Methods: To investigate the mechanisms of persistent blast-related symptoms, we examined expression profiles of transcripts across the genome to determine the role of gene activity in chronic symptoms following blast-TBI. Active duty military personnel with (1) a medical record of a blast-TBI that occurred during deployment (n = 19) were compared to control participants without TBI (n = 17). Controls were matched to cases on demographic factors including age, gender, and race, and also in diagnoses of sleep disturbance, and symptoms of PTSD and depression. Due to the high number of PCD symptoms in the TBI+ group, we did not match on this variable. Using expression profiles of transcripts in microarray platform in peripheral samples of whole blood, significantly differentially expressed gene lists were generated. Statistical threshold is based on criteria of 1.5 magnitude fold-change (up or down) and p-values with multiple test correction (false discovery rate <0.05).

Results: There were 34 transcripts in 29 genes that were differentially regulated in blast-TBI participants compared to controls. Up-regulated genes included epithelial cell transforming sequence and zinc finger proteins, which are necessary for astrocyte differentiation following injury. Tensin-1, which has been implicated in neuronal recovery in pre-clinical TBI models, was down-regulated in blast-TBI participants. Protein ubiquitination genes, such as epidermal growth factor receptor, were also down-regulated and identified as the central regulators in the gene network determined by interaction pathway analysis.

Conclusion: In this study, we identified a gene-expression pathway of delayed neuronal recovery in military personnel a blast-TBI and chronic symptoms. Future work is needed to determine if therapeutic agents that regulate these pathways may provide novel treatments for chronic blast-TBI-related symptoms.

A novel approach to the discovery of survival biomarkers in glioblastoma using a joint analysis of DNA methylation and gene expression

Glioblastoma multiforme (GBM) is the most aggressive of all brain tumors, with a median survival of less than 1.5 years. Recently, epigenetic alterations were found to play key roles in both glioma genesis and clinical outcome, demonstrating the need to integrate genetic and epigenetic data in predictive models. To enhance current models through discovery of novel predictive biomarkers, we employed a genome-wide, agnostic strategy to specifically capture both methylation-directed changes in gene expression and alternative associations of DNA methylation with disease survival in glioma. Human GBM-associated DNA methylation, gene expression, IDH1 mutation status, and survival data were obtained from The Cancer Genome Atlas. DNA methylation loci and expression probes were paired by gene, and their subsequent association with survival was determined by applying an accelerated failure time model to previously published alternative and expression-based association equations. Significant associations were seen in 27 unique methylation/expression pairs with expression-based, alternative, and combinatorial associations observed (10, 13, and 4 pairs, respectively). The majority of the predictive DNA methylation loci were located within CpG islands, and all but three of the locus pairs were negatively correlated with survival. This finding suggests that for most loci, methylation/expression pairs are inversely related, consistent with methylation-associated gene regulatory action. Our results indicate that changes in DNA methylation are associated with altered survival outcome through both coordinated changes in gene expression and alternative mechanisms. Furthermore, our approach offers an alternative method of biomarker discovery using a priori gene pairing and precise targeting to identify novel sites for locus-specific therapeutic intervention.

Subcellular localization of full-length human myeloid leukemia factor 1 (MLF1) is independent of 14-3-3 proteins

Myeloid leukemia factor 1 (MLF1) is associated with the development of leukemic diseases such as acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). However, information on the physiological function of MLF1 is limited and mostly derived from studies identifying MLF1 interaction partners like CSN3, MLF1IP, MADM, Manp and the 14-3-3 proteins. The 14-3-3-binding site surrounding S34 is one of the only known functional features of the MLF1 sequence, along with one nuclear export sequence (NES) and two nuclear localization sequences (NLS). It was recently shown that the subcellular localization of mouse MLF1 is dependent on 14-3-3 proteins. Based on these findings, we investigated whether the subcellular localization of human MLF1 was also directly 14-3-3-dependent. Live cell imaging with GFP-fused human MLF1 was used to study the effects of mutations and deletions on its subcellular localization. Surprisingly, we found that the subcellular localization of full-length human MLF1 is 14-3-3-independent, and is probably regulated by other as-yet-unknown proteins.

Met kinetic signature derived from the response to HGF/SF in a cellular model predicts breast cancer patient survival

To determine the signaling pathways leading from Met activation to metastasis and poor prognosis, we measured the kinetic gene alterations in breast cancer cell lines in response to HGF/SF. Using a network inference tool we analyzed the putative protein-protein interaction pathways leading from Met to these genes and studied their specificity to Met and prognostic potential. We identified a Met kinetic signature consisting of 131 genes. The signature correlates with Met activation and with response to anti-Met therapy (p<0.005) in in-vitro models. It also identifies breast cancer patients who are at high risk to develop an aggressive disease in six large published breast cancer patient cohorts (p<0.01, N>1000). Moreover, we have identified novel putative Met pathways, which correlate with Met activity and patient prognosis. This signature may facilitate personalized therapy by identifying patients who will respond to anti-Met therapy. Moreover, this novel approach may be applied for other tyrosine kinases and other malignancies.

20,23-dihydroxyvitamin D3, novel P450scc product, stimulates differentiation and inhibits proliferation and NF-kappaB activity in human keratinocytes

We have examined effects of the 20,23-dihydroxyvitamin D3 (20,23(OH)2D3), on differentiation and proliferation of human keratinocytes and the anti-inflammatory potential of 20,23(OH)2D3 from its action on nuclear factor-kappaB (NF-kappaB). 20,23(OH)2D3 inhibited growth of keratinocytes with a potency comparable to that for 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Cell cycle analysis showed that this inhibition was associated with G1/G0 and G2/M arrests. 20,23(OH)2D3 stimulated production of involucrin mRNA and inhibited production of cytokeratin 14 mRNA in a manner similar to that seen for 1,25(OH)2D3. Flow cytometry showed that these effects were accompanied by increased involucrin protein expression, and an increase in the cell size and granularity. Silencing of the vitamin D receptor (VDR) by corresponding siRNA abolished the stimulatory effect on involucrin gene expression demonstrating an involvement of VDR in 20,23(OH)2D3 action. This mode of action was further substantiated by stimulation of CYP24 gene expression and stimulation of the CYP24 promoter-driven reporter gene activity. 20,23(OH)2D3 displayed several fold lower potency for induction of CYP24 gene expression than 1,25(OH)2D3. Finally, 20,23(OH)2D3 inhibited the transcriptional activity of NF-kappaB in keratinocytes as demonstrated by EMSA, NF-kappaB-driven reporter gene activity assays and measurements of translocation of p65 from the cytoplasm to the nucleus. These inhibitory effects were connected with stimulation of the expression of IkappaBalpha with subsequent sequestration of NF-kappaB in the cytoplasm and consequent attenuation of transcriptional activity. In summary, we have characterized 20,23(OH)2D3 as a novel secosteroidal regulator of keratinocytes proliferation and differentiation and a modifier of their immune activity.

20-Hydroxycholecalciferol, product of vitamin D3 hydroxylation by P450scc, decreases NF-kappaB activity by increasing IkappaB alpha levels in human keratinocytes

The side chain of vitamin D3 is hydroxylated in a sequential manner by cytochrome P450scc (CYP11A1) to form 20-hydroxycholecalciferol, which can induce growth arrest and differentiation of both primary and immortalized epidermal keratinocytes. Since nuclear factor-κB (NF-κB) plays a pivotal role in the regulation of cell proliferation, differentiation and apoptosis, we examined the capability of 20-hydroxycholecalciferol to modulate the activity of NF-κB, using 1,25-dihydroxycholecalciferol (calcitriol) as a positive control. 20-hydroxycholecalciferol inhibits the activation of NFκB DNA binding activity as well as NF-κB-driven reporter gene activity in keratinocytes. Also, 20-hydroxycholecalciferol induced significant increases in the mRNA and protein levels of the NF-κB inhibitor protein, IκBα, in a time dependent manner, while no changes in total NF-κB-p65 mRNA or protein levels were observed. Another measure of NF-κB activity, p65 translocation from the cytoplasm into the nucleus was also inhibited in extracts of 20-hydroxycholecalciferol treated keratinocytes. Increased IκBα was concomitantly observed in cytosolic extracts of 20-hydroxycholecalciferol treated keratinocytes, as determined by immunoblotting and immunofluorescent staining. In keratinocytes lacking vitamin D receptor (VDR), 20-hydroxycholecalciferol did not affect IκBα mRNA levels, indicating that it requires VDR for its action on NF-κB activity. Comparison of the effects of calcitrol, hormonally active form of vitamin D3, with 20-hydrocholecalciferol show that both agents have a similar potency in inhibiting NF-κB. Since NF-κB is a major transcription factor for the induction of inflammatory mediators, our findings indicate that 20-hydroxycholecalciferol may be an effective therapeutic agent for inflammatory and hyperproliferative skin diseases.

Rat brain tumor models in experimental neuro-oncology: the C6, 9L, T9, RG2, F98, BT4C, RT-2 and CNS-1 gliomas

In this review we will describe eight commonly used rat brain tumor models and their application for the development of novel therapeutic and diagnostic modalities. The C6, 9L and T9 gliomas were induced by repeated injections of methylnitrosourea (MNU) to adult rats. The C6 glioma has been used extensively for a variety of studies, but since it arose in an outbred Wistar rat, it is not syngeneic to any inbred strain, and its potential to evoke an alloimmune response is a serious limitation. The 9L gliosarcoma has been used widely and has provided important information relating to brain tumor biology and therapy. The T9 glioma, although not generally recognized, was and probably still is the same as the 9L. Both of these tumors arose in Fischer rats and can be immunogenic in syngeneic hosts, a fact that must be taken into consideration when used in therapy studies, especially if survival is the endpoint. The RG2 and F98 gliomas were both chemically induced by administering ethylnitrosourea (ENU) to pregnant rats, the progeny of which developed brain tumors that subsequently were propagated in vitro and cloned. They are either weakly or non-immunogenic and have an invasive pattern of growth and uniform lethality, which make them particularly attractive models to test new therapeutic modalities. The CNS-1 glioma was induced by administering MNU to a Lewis rat. It has an infiltrative pattern of growth and is weakly immunogenic, which should make it useful in experimental neuro-oncology. Finally, the BT4C glioma was induced by administering ENU to a BD IX rat, following which brain cells were propagated in vitro until a tumorigenic clone was isolated. This tumor has been used for a variety of studies to evaluate new therapeutic modalities. The Avian Sarcoma Virus (ASV) induced tumors, and a continuous cell line derived from one of them designated RT-2, have been useful for studies in which de novo tumor induction is an important requirement. These tumors also are immunogenic and this limits their usefulness for therapy studies. It is essential to recognize the limitations of each of the models that have been described, and depending upon the nature of the study to be conducted, it is important that the appropriate model be selected.

20-Hydroxyvitamin D3, a product of vitamin D3 hydroxylation by cytochrome P450scc, stimulates keratinocyte differentiation

It has been shown that mammalian cytochrome P450scc can metabolize vitamin D3 to 20-hydroxyvitamin D3 (20(OH)D3) and 20,22(OH)2D3. To define the biological significance of this pathway, we tested the effects of 20(OH)D3 on the differentiation program of keratinocytes and on the expression of enzymes engaged in vitamin D3 metabolism. Immortalized HaCaT and adult human epidermal keratinocytes were used as a model and the effects of 20(OH)D3 were compared with those of 25(OH)D3 and 1,25(OH)2D3. 20(OH)D3 inhibited proliferation and caused G2/M arrest. 20(OH)D3 stimulated involucrin and inhibited cytokeratin 14 expression. The potency of 20(OH)D3 was comparable to that of 1,25(OH)2D3. 20(OH)D3 decreased the expression of cytochrome P450 enzyme (CYP)27A1 and CYP27B1, however, having only slight effect on CYP24. The effect of 20(OH)D3 was dependent on the vitamin D receptor (VDR). As shown by electrophoretic mobility shift assay, 20(OH)D3 stimulated the binding of nuclear proteins to the VDRE. Transfection of cells with VDR-specific siRNA decreased 20(OH)D3-stimulated transcriptional activity of the VDRE promoter and the expression of involucrin and CYP24 mRNA. Therefore, the above studies identify 20(OH)D3 as a biologically active secosteroid that induces keratinocyte differentiation. These data imply that the previously unreported pathway of vitamin D3 metabolism by P450scc may have wider biological implications depending, for example, on the extent of adrenal gland or cutaneous metabolism.

Comparison of Gene Sets for Expression Profiling: Prediction of Metastasis from Low-Malignant Breast Cancer

PURPOSE

In the low-risk group of breast cancer patients, a subgroup experiences metastatic recurrence of the disease. The aim of this study was to examine the performance of gene sets, developed mainly from high-risk tumors, in a group of low-malignant tumors.

EXPERIMENTAL DESIGN

Twenty-six tumors from low-risk patients and 34 low-malignant T2 tumors from patients with slightly higher risk have been examined by genome-wide gene expression analysis. Nine prognostic gene sets were tested in this data set.

RESULTS

A 32-gene profile (HUMAC32) that accurately predicts metastasis has previously been developed from this data set. In the present study, six of the eight other gene sets have prognostic power in the low-malignant patient group, whereas two have no prognostic value. Despite a relatively small overlap between gene sets, there is high concordance of classification of samples. This, together with analysis of functional gene groups, indicates that the same pathways may be represented by several of the gene sets. However, the results suggest that low-risk patients may be classified more accurately with gene signatures developed especially for this patient group.

CONCLUSION

Several gene sets, mainly developed in high-risk cancers, predict metastasis from low-malignant cancer.

Self-regulated Plk1 recruitment to kinetochores by the Plk1-PBIP1 interaction is critical for proper chromosome segregation

The polo-box domain (PBD) of mammalian polo-like kinase 1 (Plk1) is essential in targeting its catalytic activity to specific subcellular structures critical for mitosis. The mechanism underlying Plk1 recruitment to the kinetochores and the role of Plk1 at this site remain elusive. Here, we demonstrate that a PBD-binding protein, PBIP1, is crucial for recruiting Plk1 to the interphase and mitotic kinetochores. Unprecedentedly, Plk1 phosphorylated PBIP1 at T78, creating a self-tethering site that specifically interacted with the PBD of Plk1, but not Plk2 or Plk3. Later in mitosis, Plk1 also induced PBIP1 degradation in a T78-dependent manner, thereby enabling itself to interact with other components critical for proper kinetochore functions. Absence of the p-T78-dependent Plk1 localization induced a chromosome congression defect and compromised the spindle checkpoint, ultimately leading to aneuploidy. Thus, Plk1 self-regulates the Plk1-PBIP1 interaction to timely localize to the kinetochores and promote proper chromosome segregation.