Prognostic value of Mdm2, p53 and p16 in patients with astrocytomas

Expression of long intergenic non-coding RNA, regulator of reprogramming, and its prognostic value in patients with glioblastoma

BACKGROUND

Long intergenic non-coding RNA, regulator of reprogramming ( LINC-ROR) is a newly identified cytoplasmic long non-coding RNA (lncRNA), which has been found to be dysregulated in different cancers. The present work aimed to quantify LINC-ROR expression profile and assess the tumor proteins p53 and caspase 3 expressions in glioblastoma tissue specimens compared to non-cancer tissues, and to correlate these expression levels with the available clinicopathological and survival data.

METHODS

LINC-ROR relative expression in 57 glioblastoma cancer tissues and 10 non-cancer tissues was quantified by real-time polymerase chain reaction (qPCR). In addition, methylation-specific PCR of O-6-methylguanine-DNA methyltransferase ( MGMT) promoter and immunohistochemical expression of apoptosis related proteins: p53 and caspase 3 were performed.

RESULTS

The up-regulation of LINC-ROR was encountered in 89.5% of patients. The higher expression of LINC-ROR was associated with poor disease progression-free and overall survival as well as a younger age of patients ( P=0.036). p53 protein was expressed only in glioblastoma but not in non-cancer tissues while caspase 3 was weakly expressed in most non-cancer tissues and in varying degrees in glioblastoma (24% weak, 30% moderate, and 16% strong expression). The Kaplan-Meier survival plot illustrated poor survival in glioblastoma patients with over-expressed LINC-ROR ( P=0.010) and down-regulated p53 ( P=0.002). Multivariate analysis showed that glioblastoma patients were clustered into two distinct groups based on LINC-ROR expression profile, p53 staining levels and patients' overall survival.

CONCLUSIONS

LINC-ROR up-regulation may have a role in glioblastoma tumorigenesis and could be a potential prognostic marker for this fatal disease.

Impact of 9p deletion and p16, Cyclin D1, and Myc hyperexpression on the outcome of anaplastic oligodendrogliomas

Objective

To study the presence of 9p deletion and p16, cyclin D1 and Myc expression and their respective diagnostic and prognostic interest in oligodendrogliomas.

Methods

We analyzed a retrospective series of 40 consecutive anaplastic oligodendrogliomas (OIII) from a single institution and compared them to a control series of 10 low grade oligodendrogliomas (OII). Automated FISH analysis of chromosome 9p status and immunohistochemistry for p16, cyclin D1 and Myc was performed for all cases and correlated with clinical and histological data, event free survival (EFS) and overall survival (OS).

Results

Chromosome 9p deletion was observed in 55% of OIII (22/40) but not in OII. Deletion was highly correlated to EFS (median = 29 versus 53 months, p<0.0001) and OS (median = 48 versus 83 months, p<0.0001) in both the total cohort and the OIII population. In 9p non-deleted oligodendrogliomas, p16 hyperexpression correlated with a shorter OS (p = 0.02 in OII and p = 0.0001 in OIII) whereas lack of p16 expression was correlated to a shorter EFS and OS in 9p deleted OIII (p = 0.001 and p = 0.0002 respectively). Expression of Cyclin D1 was significantly higher in OIII (median expression 45% versus 14% for OII, p = 0.0006) and was correlated with MIB-1 expression (p<0.0001), vascular proliferation (p = 0.002), tumor necrosis (p = 0.04) and a shorter EFS in the total cohort (p = 0.05). Hyperexpression of Myc was correlated to grade (median expression 27% in OII versus 35% in OIII, p = 0.03), and to a shorter EFS in 9p non-deleted OIII (p = 0.01).

Conclusion

Chromosome 9p deletion identifies a subset of OIII with significantly worse prognosis. The combination of 9p status and p16 expression level identifies two distinct OIII populations with divergent prognosis. Hyperexpression of Bcl1 and Myc appears highly linked to anaplasia but the prognostic value is unclear and should be investigated further.

Zinc and zinc-containing biomolecules in childhood brain tumors

Zinc ions are essential cofactors of a wide range of enzymes, transcription factors, and other regulatory proteins. Moreover, zinc is also involved in cellular signaling and enzymes inhibition. Zinc dysregulation, deficiency, over-supply, and imbalance in zinc ion transporters regulation are connected with various diseases including cancer. A zinc ion pool is maintained by two types of proteins: (i) zinc-binding proteins, which act as a buffer and intracellular donors of zinc and (ii) zinc transporters responsible for zinc fluxes into/from cells and organelles. The decreased serum zinc ion levels have been identified in patients suffering from various cancer diseases, including head and neck tumors and breast, prostate, liver, and lung cancer. On the contrary, increased zinc ion levels have been found in breast cancer and other malignant tissues. Zinc metalloproteomes of a majority of tumors including brain ones are still not yet fully understood. Current knowledge show that zinc ion levels and detection of certain zinc-containing proteins may be utilized for diagnostic and prognostic purposes. In addition, these proteins can also be promising therapeutic targets. The aim of the present work is an overview of the importance of zinc ions, zinc transporters, and zinc-containing proteins in brain tumors, which are, after leukemia, the second most common type of childhood cancer and the second leading cause of death in children after accidents.

Expression and Prognostic Significance of p53 in Glioma Patients: A Meta-analysis

Glioma is a brain tumor deriving from the neoplastic glial cells or neuroglia. Due to its resistance to anticancer drugs and different disease progress of individuals, patients with high-grade glioma are difficult to completely cure, leading to a poor prognosis and low overall survival. Therefore, there is an urgent need to look for prognostic and diagnostic indicators that can predict glioma grades. P53 is one of the widely studied biomarkers in human glioma. The purpose of this study was to comprehensively evaluate the significance of p53 expression in glioma grades and overall survival. We searched commonly used electronic databases to retrieve related articles of p53 expression in glioma. Overall, a total of 21 studies including 1322 glioma patients were finally screened out. We observed that the frequency of p53 immuno-positivity was higher in high-grade patients than that in low-grade category (63.8 vs. 41.6 %), and our statistic analysis indicated that p53 expression was associated with pathological grade of glioma (OR 2.93, 95 % CI 1.87-4.60, P < 0.00001). This significant correction was also found in 1-, 3- and 5-year overall survival. However, no positive relationship was found between age, sex, tumor size and p53 expression in patients with glioma. In conclusion, our results suggested that p53 immunohistochemical expression might have an effective usefulness in predicting the prognosis in patients with glioma.

Association of p53 rs1042522, MDM2 rs2279744, and p21 rs1801270 polymorphisms with retinoblastoma risk and invasion in a Chinese population

Single nucleotide polymorphisms (SNPs) of p53 rs1042522, MDM2 rs2279744 and p21 rs1801270, all in the p53 pathway, which plays a crucial role in DNA damage and genomic instability, were reported to be associated with cancer risk and pathologic characteristics. This case-control study was designed to analyse the association between these SNPs and retinoblastoma (RB) in a Chinese Han population. These SNPs in 168 RB patients and 185 adult controls were genotyped using genomic DNA from venous blood. No significant difference was observed in allele or genotypic frequencies of these SNPs between Chinese RB patients and controls (all P > 0.05). However, the rs1042522 GC genotype showed a protective effect against RB invasion, as demonstrated by event-free survival (HR = 0.53, P = 0.007 for GC versus GG/CC). This effect was significant for patients with a lag time >1 month and no pre-enucleation treatment (P = 0.007 and P = 0.010, respectively), indicating an interaction between p53 rs1042522 and clinical characteristics, including lag time and pre-enucleation treatment status. Thus, the rs1042522 SNP may be associated with RB invasion in the Han Chinese population; however, further large and functional studies are needed to assess the validity of this association.

Efficient inhibition of human glioma development by RNA interference-mediated silencing of PAK5

Glioma is the most common type of primary intracranial tumor and is highly lethal due to its pathogenetic location, high invasiveness, and poor prognosis. Even combined surgery and chemoradiotherapy do not effectively rescue glioma patients. Molecular target therapy is considered a safe and promising therapy for glioma. The identification of a novel, effective target protein in gliomas is of great interest. We found that PAK5 was highly expressed in the tumor tissues of glioma patients and human glioma cell lines. We then used a lentivirus-delivered short hairpin RNA to stably silence PAK5 expression in glioma cells and explore its influence. The results showed that the inhibition of PAK5 reduced cell viability and delayed the cell cycle at the G0/G1 phase in the glioma cells with PAK5 high expression. In addition, silencing PAK5 expression in U87 cells weakened their colony formation ability and in vivo tumorigenesis ability. Further studies demonstrated that PAK5 inhibition led to an increase in cleaved caspase 3 and a decrease in β-catenin. In conclusion, our results suggest that the inhibition of PAK5 by RNA interference might efficiently suppress tumor development of glioma cells with PAK5 high expression. This finding provides a novel, promising therapeutic target for glioma treatment.

Expression of high-mobility group AT-hook protein 2 and its prognostic significance in malignant gliomas

High-mobility group AT-hook protein 2 (HMGA2) is an architectural transcription factor associated with malignancy, invasiveness, and poor prognosis in a variety of human neoplasms. This study investigated HMGA2 expression and prognostic value in human gliomas. We also correlated HMGA2 expression with Ki-67 labeling index and matrix metalloproteinase-2. Expression of HMGA2 in 78 human gliomas and 7 human normal brain samples was studied using immunohistochemistry, and 29 gliomas were randomly selected and studied along with the normal brain by real-time quantitative polymerase chain reaction and Western blot analysis. Expression of HMGA2 protein was significantly higher in glioblastoma multiforme (World Health Organization [WHO] grade IV; P = .007) and anaplastic astrocytoma (WHO grade III; P = .037) than in diffuse astrocytoma (WHO grade II). Expression of HMGA2 correlated significantly with expression of Ki-67 (r = 0.415, P < .01) and matrix metalloproteinase-2 (r = 0.363, P < .01), but not with patient sex and age. The real-time quantitative polymerase chain reaction and Western blot analysis revealed similar results. Patients with tumors expressing HMGA2 at a higher level had a significantly shorter progression-free survival time (11.2 months versus 18.8 months; P = .021). Expression of HMGA2 significantly correlates with tumor cell proliferation, invasion, and survival in gliomas. The results suggest that HMGA2 has an important role in the treatment and prognosis of these cancers.

Vertebrate animal models of glioma: understanding the mechanisms and developing new therapies

Glioblastoma Multiforme (GBM) is recognized as one of the most deadly cancers characterized by cellular atypia, severe necrosis, and high rate of angiogenesis. In this review, we discuss a diversified group of GBM xenograft models and compare them with the genetically engineered mouse (GEM) model systems. Next, we describe common genetic defects observed in GBM and numerous GEM models that recapitulate these abnormalities. Finally, we focus on the clinical value of other vertebrate animal models such as the canine model by examining their contributions to GBM research.

HMGA1 expression in human gliomas and its correlation with tumor proliferation, invasion and angiogenesis

High-mobility group A1 (HMGA1) protein is an architectural transcription factor widely expressed during embryonic development and tumor progression. The purpose of this research was to investigate the expression of HMGA1 in malignant gliomas with different WHO classification and to study the correlation of HMGA1 expression with tumor proliferation, invasion, and angiogenesis. Expression of HMGA1, Ki-67, MMP-9, VEGF-A, and MVD in malignant gliomas and their correlation were studied in 60 samples of different WHO classification by use of immunohistochemistry, and in 27 randomly selected samples by use of real-time quantitative PCR. Immunohistochemistry results showed that nuclear immunostaining of HMGA1 protein was not observed in normal brain tissues but was observed in 96.7% (58 of 60) of malignant gliomas including high (+++) in 15 (25.0%), moderate (++) in 28 (46.7%), and negligible to low (0-+) in 17 (28.3%) samples. Expression of HMGA1 protein was significantly higher in glioblastoma multiforme than in WHO grade II (P = 0.002) and WHO grade III gliomas (P = 0.024). HMGA1 protein expression correlated significantly with expression of Ki-67 (r = 0.530, P = 0.000), MMP-9 (r = 0.508, P = 0.000), VEGF-A (r = 0.316, P = 0.014), and MVD (r = 0.321, P = 0.012), but not with sex (r = 0.087, P = 0.510) and age (r = -0.121, P = 0.358). Real-time quantitative PCR results, also, were indicative of HMGA1 overexpression in glioblastoma multiforme compared with WHO grade II (P = 0.043) and WHO grade III (P = 0.031) gliomas. HMGA1 gene expression correlated significantly with gene expression of Ki-67 (r = 0.429, P = 0.025), MMP-9 (r = 0.443, P = 0.024), and VEGF-A (r = 0.409, P = 0.034). These results indicated that expression of HMGA1 correlates significantly with malignancy, proliferation, invasion, and angiogenesis of gliomas. We conclude that HMGA1 may be a potential biomarker and rational therapeutic target for human tumors.

Distinct molecular signatures in pediatric infratentorial glioblastomas defined by aCGH

Glioblastomas (GBM) are rare in children, but reportedly have more varied outcome which suggests differences in tumor etiology compared to typical GBM of adults. To investigate this we performed high resolution array comparative genomic hybridization (aCGH) analysis on three pediatric infratentorial GBM, ages 3.5, 7 and 14 years. Two of these tumors occurred in the brainstem and one in the spinal cord. While histologically typical, one brainstem tumor showed mainly pleomorphic astrocytic cells, whereas the other brainstem and spinal tumors showed a GFAP positive small cell component. Whole chromosomal gains (#1 and #2) and loss (#20) were seen only in the pleomorphic brainstem GBM, which also showed a high level of segmental genomic copy number changes. Segmental loss involving chromosome 8 was seen in all three tumors (Chr8;133039446-136869494, Chr8;pter-3581577, and Chr8;pter-30480019 respectively), whereas loss involving chromosome 16 was seen in only 2 cases with small cell components (Chr16;31827239-qter and Chr16;pter-29754532). Segmental gain of chromosome 7 was shared only between the 2 brainstem cases (Chr7;17187166-qter and Chr7;69824947-qter). Chromosome 17 showed segmental gain of 17q in the backdrop of loss of 17p only in case 1. Segmental gain of chromosome 1q was seen only in case 2. The spinal GBM showed a relatively stable karyotype with a unique loss of Chr19;32848902-qter. None of the frequent losses, gains and amplifications known to occur in adult GBM were identified, suggesting that pediatric infratentorial glioblastomas show a molecular karyotype that was more characteristic of pediatric embryonal tumors than adult GBM.

Effects of the single nucleotide polymorphism at MDM2 309 on breast cancer patients with/without BRCA1/2 mutations

BACKGROUND

A germ line single nucleotide polymorphism (SNP) in the first intron of the gene encoding MDM2 at position 309, an important modulator of p53, has been described. BRCA1/2 mutation have been associated with increased rates of breast cancers with mutated P53. It was shown that the presence of MDM2 309 SNP correlated with younger cancer onset age in individuals with a p53 mutations. The differential effects of this SNP were also linked to estrogen receptor activation. Here we report on our study of 453 Ashkenazi breast cancer patients of whom 180 were positive for the known Ashkenazi BRCA1/2 mutations

METHODS

DNA from breast cancer patients was obtained for analysis of one of the three common BRCA1/2 mutations and MDM2 SNP309. Data regarding cancer onset and death ages was obtained from our database and Statistical analysis was performed using the SPSS statistical package (SPCC Inc., Chicago, IL), and JMP software (SAS Institute, Cary, NC).

RESULTS

The percentage of MDM2 SNP309 in control and BRCA 1/2 population which is similar to that reported for other Jewish Ashkenazi populations at 52.2% for the heterozygotes and 25.0% for MDM2SNP309G/G and 22.8% for MDM2SNP309T/T.There was not a statistical significant difference in median age of disease onset in the different MDM2 SNP309 subgroups of the BRCA1/2 carriers. When we further divided the group into under and above 51 years old ( presumed menopause age) in the BRCA1 positive subset we found that there were less patients of the MDM2SNP309 G/G versus the MDM2SNP309 T/T in the over 51 patient group (p = 0.049). This result has been obtained in a relatively small subgroup and is of borderline statistical significance. Interestingly, in the BRCA1/2 mutation carriers, we found a survival advantage for patients harboring the SNP309 G/G genotype (p = 0.0086) but not for the 272 patients not harbouring this mutations.

CONCLUSION

MDM2SNP309G/G main effect on BRCA1/2 positive mutation carriers is linked to its effect on patients survival. Further research is needed in order to understand the reason for this difference.

Nestin and CD133: valuable stem cell-specific markers for determining clinical outcome of glioma patients

AIM

Gliomas represent the most frequent neoplasm of the central nervous system. Unfortunately, surgical cure of it is practically impossible and their clinical course is primarily determined by the biological behaviors of the tumor cells. The aim of this study was to investigate the correlation of the stem cell markers Nestin and CD133 expression with the grading of gliomas, and to evaluate their prognostic value.

METHODS

The tissue samples consisted of 56 low- (WHO grade II), 69 high- (WHO grade III, IV) grade gliomas, and 10 normal brain tissues. The expression levels of Nestin and CD133 proteins were detected using SABC immunohistochemical analysis. Then, the correlation of the two markers' expression with gliomas' grading of patients and their prognostic value were determined.

RESULTS

Immunohistochemical analysis with anti-Nestin and anti-CD133 antibodies revealed dense and spotty staining in the tumor cells and their expression levels became significantly higher as the glioma grade advanced (p < 0.05). There was a positive correlation between the two markers' expression in different gliomas tissues (rs = 0.89). The low expression of the two markers significantly correlated with long survival of the glioma patients (p < 0.05). The survival rate of the patients with Nestin+/CD133+ expression was the lowest (p < 0.01), and the multivariate analysis confirmed that conjoined expression of Nestin+/CD133+ and Nestin-/CD133- were independent prognostic indicators of gliomas (both p < 0.01, Cox proportional hazard regression model).

CONCLUSION

These results collectively suggest that Nestin and CD133 expression may be an important feature of human gliomas. A combined detection of Nestin/CD133 co-expression may benefit us in the prediction of aggressive nature of this tumor.

Pediatric glioblastomas: a histopathological and molecular genetic study

Glioblastoma multiforme (GBM) occurs rarely in children. Relatively few studies have been performed on molecular properties of pediatric GBMs. Our objective in this study was to evaluate the genetic alterations in pediatric GBM (age < or = 18 years) with special reference to p53, p16, and p27 protein expression, alterations of the epidermal growth factor receptor (EGFR), and deletion of the phosphate and tensin homolog gene (PTEN). Thirty cases of childhood GBMs reported between January 2002 and June 2007 were selected, and slides stained with hematoxylin and eosin were reviewed. Immunohistochemical staining was performed for EGFR, p53, p16, and p27, and tumor proliferation was assessed by calculating the MIB-1 labeling index (LI). Fluorescence in situ hybridization analysis was performed to evaluate for EGFR amplification and PTEN deletion. Histopathological features and MIB-1 LI were similar to adult GBMs. p53 protein expression was observed in 63%. Although EGFR protein overexpression was noted in 23% of cases, corresponding amplification of the EGFR gene was rare (5.5%). Deletion of the PTEN gene was also equally rare (5.5%). One case showed polysomy (chromosomal gains) of chromosomes 7 and 10. Loss of p16 and p27 immunoexpression was observed in 68% and 54% of cases, respectively. In pediatric de novo/primary GBMs, deletion of PTEN and EGFR amplification are rare, while p53 alterations are more frequent compared to primary adult GBMs. Frequency of loss of p16 and p27 immunoexpression is similar to their adult counterparts. This suggests that pediatric malignant gliomas are distinctly different from adult GBMs, highlighting the need for identification of molecular targets that may be adopted for future novel therapeutic strategies.

Correlation analysis between the expression of P21WAF1/CIP1, P16 proteins and human glioma

AIM

Glioma is the most common neoplasm of the brain. Unfortunately, surgical cure of it is practically impossible and clinical course is primarily determined by the biological behaviour of the tumour cells. The purpose of this study was to investigate the correlation between the expression levels of P21WAF1/CIP1, P16 proteins and the grading of glioma.

METHODS

T98G human glioma cell line, normal human astrocyte (HA) cell line, tumour tissue samples from 70 patients suffering from glioma and normal brain tissues from 20 cases with brain contusion were investigated. The expression levels of P21WAF1/CIP1 and P16 proteins were detected using SABC immunohistochemical staining and semi-quantitive reverse transcriptase polymerase chain reaction (RT-PCR) assay. Then, the correlation of the two markers' expression with glioma grading of patients was analysed.

RESULTS

The expression levels of P21WAF1/CIP1 and P16 proteins in the T98G cell line were much lower than that in the HA cell line. Their positive expression rates in glioma tissues were 55.71% and 42.86% respectively, and a significant increase was observed in normal brain tissues (p = 0.012, 0.008). Combined with the result of semi-quantitive RT-PCR, we could demonstrate that the expression intensity of P21WAF1/CIP1 and P16 decreased with the glioma grade increase. Co-expression of them was also found in glioma and normal brain tissues. Furthermore, there was a negative correlation between the two markers' expression and glioma grading of patients (rs = -0.68, -0.56).

CONCLUSIONS

The positive expression rate and co-expression rate of P21WAF1/CIP1 and P16 proteins could reflect the malignant grade of glioma to some extent, and they can be considered as a sensitive index for glioma grading.

Expression of the Polycomb-Group protein BMI1 and correlation with p16 in astrocytomas an immunohistochemical study on 80 cases

A number of studies on the putative relation between Polycomb-Group (PcG) proteins overexpression and carcinogenesis have been published recently. BMI1, the prototype PcG gene, is critically involved in cell cycle control and differentiation, and despite the regulatory role demonstrated in central nervous system (CNS) development, its implication in brain tumorigenesis is scarcely known. Moreover, to the best of our knowledge, large studies on human brain tumors tissue are lacking. To gain a new insight, we tested 80 primary brain astrocytomas for BMI1 expression using immunohistochemistry and established a correlation with the expression of p16, a negatively regulated target of BMI1 function. Fifty-four cases (72.5%) were BMI1 + /p16-, and 22 cases (27.5%) were BMI1 + /p16+. Slight non-significant differences were noted in the expression profile between grades II, III, and IV astrocytomas. However, when the 22 BMI1 + /p16+ tumors were examined cytologically, a substantial proportion contained a significant gemistocytic component, which is thought to be an adverse prognostic factor or to display a high degree of anaplasia, suggesting a common molecular mechanism of BMI1/p16 pathway disruption, which may have prognostic implications.

Epidemiology of brain tumors

Brain tumors seemed to have increased in incidence over the past 30 years, but the rise probably results from use of new neuroimaging techniques. Treatments have not improved prognosis for rapidly fatal brain tumors. Established brain tumor risk factors (exposure to ionizing radiation, rare mutations of penetrant genes, and familial history) explain only a small proportion of brain tumors, and only one of these potentially is modifiable. Genetic and environmental characteristics likely play a role in familial aggregation of glioma and these factors are not identified. New concepts in brain tumor etiology and clinical management are the goal of research, with an aim at eradicating this devastating disease.

P53 gene mutation and expression of MDM2, P53, P16 protein and their relationship in human glioma

To investigate the effect of P53 protein accumulation and p53 gene mutation in the pathogenesis of glioma and to study the role of MDM2, P53 and P16 protein in glioma formation and progression and their relationship with each other, LSAB immunohistochemical staining method and non-isotopic PCR-SSCP techniques were used to detect the expression of MDM2, P53 and P16 protein and p53 gene mutation in 48 cases of gliomas. The results showed that the positive expression rate of MDM2, P53 and the negative rate of P16 was 22.9%, 41.7% and 60.4%, respectively. The latter two in high grade (grade III, IV) gliomas had a significantly higher rate than in the low grade (grade II) gliomas. Moreover, the co-expression of MDM2 and P53 protein was confirmed in only 1 of 48 cases. No significant difference was found in the rate of the expression of MDM2 between high grade and low grade gliomas (P > 0.1). PCR-SSCP results showed that mutation of 5-8 exons of p53 gene was detected in 17 out of 48 cases (35.42%). Mutation was detected in 16 of 20 cases of positive p53 expression, and another one was detected in 28 cases of negative expression cases. The correlation between p53 mutation and p53 immunopositivity was observed in 89.6% of the cases. P53 gene mutation and the level of MDM2, P53 and P16 protein were not related to age, gender of the patients, tumor location and size. It is concluded that the mutation of p53 and deletion of p16 might play important roles in the tumorigenesis of gliomas and it was significantly associated with the grade of tumor differentiation. P53 protein accumulation can indirectly reflect p53 mutation. MDM2 amplification and overexpression might be an early event in the growth of human gliomas.

Perinuclear leucine-rich repeats and immunoglobulin-like domain proteins (LRIG1-3) as prognostic indicators in astrocytic tumors

We have previously characterized three human leucine-rich repeats and immunoglobulin-like domains (LRIG) genes and proteins, named LRIG1-3 and proposed that they may act as suppressors of tumor growth. The LRIG1 transmembrane protein antagonizes the activity of epidermal growth factor receptor family receptor tyrosine kinases. In this study, we evaluated the mRNA expression level of LRIG1-3 in human glioma cell lines and control-matched glioma tissues, characterized the sub-cellular localization of an LRIG3-GFP fusion protein, and analyzed the relationship between sub-cellular localization of LRIG1-3 and clinical parameters in 404 astrocytic tumors by immunohistochemistry. LRIG1-3 mRNA was detected in all human glioma cell lines and matched glioma samples, with large differences in the expression levels. Ectopically expressed LRIG3-GFP localized to perinuclear and cytoplasmic compartments, and to the cell surface of transfected glioma cells. Perinuclear staining of LRIG1-3 was associated with low WHO grade and better survival of the patients. Perinuclear staining of LRIG3 was associated with a lower proliferation index and was in addition to tumor grade, an independent prognostic factor. Furthermore, within the groups of grade III and grade IV tumors, perinuclear staining of LRIG3 significantly correlated with better survival. These results indicate that expression and sub-cellular localization of LRIG1-3 might be of importance in the pathogenesis and prognosis of astrocytic tumors.

Study of a novel brain relatively specific gene LRRC4 involved in glioma tumorigenesis suppression using the Tet-on system

LRRC4 is a novel relatively specific gene, which displays significant down-regulation in primary brain tumor biopsies and has the potential to suppress brain tumor growth. In this study, we investigated the growth inhibitory effect of LRRC4 on tumorigencity in vivo and on cell proliferation in vitro by a tetracycline-inducible expression system. Results showed that LRRC4 significantly reduced the growth and malignant grade of xenografts arising from glioblastoma U251MG cells. Cell proliferation was markedly inhibited after U251MG Tet-on-LRRC4 cell induction with doxycycline. Flow cytometry and Western blot analysis demonstrated that LRRC4 mediated a delay of the cell cycle in late G1, possibly through up-regulating the expressions of p21Waf1/cip1 and p27Kip1 and down-regulating the expressions of cyclin-dependent kinase 2, retinoblastoma protein and epidermal growth factor receptors. Together, these findings provide clues to the function of LRRC4 as a negative regulator of cell growth and underscore a link between the above-mentioned cyclins, cyclin-associated molecules and tumorigenicity.