Downregulation of programmed cell death 10 is associated with tumor cell proliferation, hyperangiogenesis and peritumoral edema in human glioblastoma

Background

Neovascularization and peritumoral edema are hallmarks of glioblastoma (GBM). Programmed cell death 10 (PDCD10) plays a pivotal role in regulating apoptosis, neoangiogenesis and vessel permeability and is implicated in certain tumor signaling pathways. However, little is known about PDCD10 in GBM. We aimed to investigate the expression pattern of PDCD10 and to identify the association of its expression with some molecular and clinical parameters in human GBM.

Methods

mRNA and protein expression of PDCD10 were examined respectively by real-time RT-PCR and Western blotting in GBM (n = 27), astrocytoma grade II (n = 13) and control (n = 11). The protein level of p-Akt and GFAP was detected by Western blot. Double-imunofluorecent staining was performed to reveal the cellular expression profile of PDCD10. Brain edema and microvascular density (MVD) were respectively analyzed based on pre-operative MRI and after laminin immnostaining. MGMT promoter methylation was detected by methylation specific PCR.

Results

mRNA and protein levels of PDCD10 were significantly downregulated in GBM, concomitantly accompanied by the activation of Akt. PDCD10 immunoreactivity was absent in proliferating tumor cells, endothelial cells and GFAP-positive cells, but exclusively present in the hypoxic pseudopalisading cells which underwent apoptosis. Moreover, loss of PDCD10 was associated with a higher MVD and a more severe peritumoral edema but not with MGMT promoter methylation in GBM.

Conclusion

We report for the first time that PDCD10 expression is downregulated in GBM, which is associated with the activation of Akt signaling protein. PDCD10 is potentially implicated in tumor proliferation and apoptosis, hyperangiogenesis and peritumoral edema in GBM.

Loss of endothelial programmed cell death 10 activates glioblastoma cells and promotes tumor growth

BACKGROUND

Neo-angiogenesis is a hallmark of glioblastoma (GBM) and is sustained by autocrine and paracrine interactions between neoplastic and nonneoplastic cells. Programmed cell death 10 (PDCD10) is ubiquitously expressed in nearly all tissues and plays crucial roles in regulating angiogenesis and apoptosis. We recently discovered the absence of PDCD10 expression in the tumor vessels of GBM patients. This raised the hypothesis that loss of endothelial PDCD10 affected GBM cell phenotyping and tumor progression.

METHODS

Endothelial PDCD10 was silenced by siRNA and lentiviral shRNA. The tumor cell phenotype was studied in direct and indirect co-culture of endothelial cells (ECs) with U87 or LN229. Angiogenic protein array was performed in the media of PDCD10-silenced ECs. Tumor angiogenesis and tumor growth were investigated in a human GBM xenograft mouse model.

RESULTS

Endothelial silence of PDCD10 significantly stimulated tumor cell proliferation, migration, adhesion, and invasion and inhibited apoptosis in co-cultures. Stable knockdown of endothelial PDCD10 increased microvessel density and the formation of a functional vascular network, leading to a 4-fold larger tumor mass in mice. Intriguingly, endothelial deletion of PDCD10 increased (≥2-fold) the release of 20 of 55 tested proangiogenic factors including VEGF, which in turn activated Erk1/2 and Akt in GBM cells.

CONCLUSIONS

For the first time, we provide evidence that loss of endothelial PDCD10 activates GBM cells and promotes tumor growth, most likely via a paracrine mechanism. PDCD10 shows a tumor-suppressor-like function in the cross talk between ECs and tumor cells and is potentially implicated in GBM progression.

The functional Aquaporin 1 -783G/C-polymorphism is associated with survival in patients with glioblastoma multiforme

BACKGROUND

Despite a dismal prognosis, variability exists regarding the survival-time in patients with glioblastoma-multiforme (GBM), which may be explained by genetic variation. A possible candidate-gene for such variation is Aquaporin-1 (AQP1), since Aquaporin-1-expression influences the pathogenesis and outcome of various malignancies. Functional genetic variants in the promoter of AQP1, modifying Aquaporin-1-expression, could be associated with altered survival in patients with GBM.

METHODS

We sequenced the human AQP1-promoter to detect novel sequence variants, which might impact on Aquaporin-1-expression and tested the hypothesis, that functional single nucleotide polymorphisms are associated with different survival-times of patients suffering from GBM.

RESULTS

Sequencing the AQP1-promoter revealed a novel -783G/C-polymorphism. Reporter-assays showed that substitution of G for C was associated both with increased transcriptional-activation of the AQP1-promoter by serum and with increased AQP1 mRNA expression. Finally, we assessed in a cohort of 155 Caucasian patients with GBM whether the functional single-nucleotide-783G/C-polymorphism is associated with survival-time. Cox-regression analyses revealed the AQP1 -783G/C genotype status as an independent prognostic-factor when jointly considering other predictors of survival. Homozygous CC subjects had a significantly worse outcome compared to GC/GG genotypes (hazard ratio: 3.09; 95% CI, 1.43-6.65; P = 0.004).

CONCLUSIONS

Our findings suggest the novel AQP1 polymorphism as a survival prognosticator in patients suffering from GBM that could help to identify a subgroup of patients at high risk for death. Further studies are necessary to reveal the exact molecular mechanisms.

Expression of aquaporin 5 and the AQP5 polymorphism A(-1364)C in association with peritumoral brain edema in meningioma patients

Aquaporins (AQP) are a growing family of water-channel proteins, numbering 13 to date. Recent studies have reported AQP1 and AQP4 to be involved in the development and resorption of brain edemas of different origin. Other AQPs have also been detected in brain tissue, but their impact on brain edema remains to be shown. To evaluate a possible role of AQP5 in brain edema, we investigated the association of AQP5 expression and the functional AQP5 promoter polymorphism A(-1364)C with occurrence and intensity of peritumoral edema in meningioma patients. Peritumoral edema was classified in three degrees based on preoperative imaging in 89 meningioma patients treated at the University Hospital Essen between 2003 and 2006. AQP5 expression was assessed immunohistochemically in tumor tissue obtained during neurosurgical tumor resection. Genotypes of the A(-1364)C polymorphism were determined using the "slowdown" polymerase chain reaction. Higher levels of AQP5 expression were significantly correlated with the AQP5-1364 AA genotype (P = 0.02). AQP5 expression was positively correlated with edema (P = 0.04). AQP5 genotypes were not significantly associated with the occurrence, but with the intensity of peritumoral brain edema (P = 0.04). In our cohort, 40 % of patients with grade I, 66.7 % with grade II, and 76.5 % with grade III edema possessed at least one A allele. Development and intensity of peritumoral edema in meningiomas are associated with AQP5 expression. The intensity of edema correlates with the AQP5 A(-1364)C genotype. This suggests AQP5 as an interesting new candidate involved in peritumoral brain edema in meningioma patients.

Correlation of aquaporin-1 water channel protein expression with tumor angiogenesis in human astrocytoma

Aquaporin-1 (AQP1) is a water channel protein, widely expressed in epithelial and endothelial cells, known to be associated with invasion, angiogenesis, cell migration and formation of tumour oedema in several malignancies. We investigated the pattern of immunohistochemical expression of AQP1 in human astrocytomas and its role in tumour angiogenesis and infiltration. Immunohistochemical staining of AQP1 was performed in astrocytomas of grade II, III and IV. Intensity and pattern of expression were analysed. Non-neoplastic brain tissues served as control. There was a significant increase in the intensity of AQP1 expression from low-grade to high-grade astrocytomas (p<0.0001). Despite intense expression of AQP1 in astrocytoma grade IV, we observed strong regional differences. AQP1 up-regulation was predominantly located perivascularly, in areas of tumour infiltration, distant from the necrotic tumour core. AQP1 expression correlates with the grade of malignancy and is associated with angiogenesis, as well as with invasion of grade IV tumour in areas of tumour infiltration. Suppression of AQP1 expression could be a potential means of reducing invasion of glioma cells.

Role of the GNAS1 T393C polymorphism in patients with glioblastoma multiforme

The T393C polymorphism of the GNAS1 locus, which encodes the Gαs protein, has recently been found to be associated with patient outcome in various malignancies. We investigated the association between GNAS1 genotype and survival among patients suffering from glioblastoma multiforme (GBM). One hundred and sixty-two patients with GBM were retrospectively investigated. Inclusion criteria were availability of DNA and, for surviving patients, a follow-up of at least 24 months. The results were analysed based on clinical data, type of surgical intervention, adjuvant therapy, and 2-year survival. At the 2-year follow up, 79.6% of patients had died. Two-year survival rates were as follows: CC-homozygous patients, 15.8%; CT-heterozygous patients, 23.1%; and TT-homozygous patients, 18.2% (p = 0.461). Subgroup analysis revealed different 2-year survival rates in the group that underwent stereotactic biopsy, with 0% for CC-homozygous, 2.8% for CT-heterozygous, and 15.4% survival for TT-homozygous patients, but the differences were not statistically significant (p = 0.229). Our results indicate that there is no association between the GNAS1 T393C polymorphism and 2-year survival among patients with GBM.

Association of the CC genotype of the regulatory BCL2 promoter polymorphism (-938C>A) with better 2-year survival in patients with glioblastoma multiforme

OBJECT

Bcl-2 plays a key role in the downregulation of apoptosis and proliferation and leads to increased chemoresistance in glioblastoma multiforme (GBM). The authors investigated the role of a common regulatory single-nucleotide polymorphism (-938C>A), which is located in the inhibitory P2 promoter of BCL2.

METHODS

Data from 160 patients suffering from GBM were retrospectively evaluated. Study inclusion criteria consisted of available DNA and, in patients still alive, a follow-up of at least 24 months. Results were analyzed with respect to the basic clinical data, type of surgical intervention (gross-total resection [GTR] versus stereotactic biopsy [SB]), adjuvant therapy, MGMT promoter methylation, and survival at the 2-year follow-up.

RESULTS

At the 2-year follow-up, 127 (79.4%) of the 160 patients had died. Kaplan-Meier curves revealed a significantly higher rate of survival for homo- and heterozygous C-allele carriers (p = 0.031). In the GTR group, the survival rate was 47.1% for homozygous C-allele carriers, 32.0% for heterozygous C-allele carriers, and only 21.4% for homozygous A-allele carriers (p = 0.024). The SB group showed no genotype-dependent differences. Multivariable Cox regression revealed that the BCL2 (-938AA) genotype was an independent negative prognostic factor for 2-year survival in the GTR group according to the BCL2 (-938CC) genotype reference group (hazard ratio 2.50, 95% CI 1.14-5.48, p = 0.022).

CONCLUSIONS

These results suggested that the (-938C>A) polymorphism is a survival prognosticator as well as a marker for a high-risk group among patients with GBM who underwent GTR.

Cerebellar activation patterns in deaf participants for perception of sign language and written text

To address the influence of language presentation on cerebellar activation, hearing volunteers were compared with deaf individuals using functional magnetic resonance imaging during observation of German sign language and text reading. In deaf participants, German sign language revealed activation of the auditory and language-related areas including the medial temporal gyrus (BA 21) and Crus I. In normal hearing participants not understanding German sign language, Crus I was less activated during observation of German sign language but strongly activated during text reading and accompanied by activation of the medial temporal gyrus. Our results indicate that cerebellar activation in Crus I corresponds to language perception as correlated with cortical activation in language-related areas and is not dependent on the mode of language presentation.

Cross-modal plasticity in deaf subjects dependent on the extent of hearing loss

Cross-modal plasticity in deaf subjects is still discussed controversial. We tried to figure out whether the plasticity is dependent on the extent of hearing loss. Three groups of volunteers, comprising twelve individuals each, were investigated. They were characterized by three distinctive features, one had normal hearing, the other one lost hearing and the third had only minimal residual hearing ability. All participants, except those of group one, were capable of using German Sign Language (GSL). The groups were studied with functional MRI in a standard block design during individuals' watching sign language videos alternating with black frame. During sign language conditions, deaf subjects revealed a significant activation of the auditory cortex in both hemispheres comprising Brodmann areas (BA) 42 and 22 corresponding to the secondary associative auditory areas. Additionally, activation of the angular and supramarginal gyrus was seen. Activation of the primary auditory cortex was revealed in deaf subjects with total hearing loss during sign language tasks but not in subjects with residual hearing ability. In conclusion our results indicate a cortical reorganization of the auditory cortex comprising primary auditory fields only present in subjects with total hearing loss.