Alternative pathway of transcriptional induction of p21WAF1/Cip1 by cyclosporine A in p53-deficient human glioblastoma cells

Effects of Postoperative Intravenous Cyclosporine Treatment on the Survival and Functional Performance Status of Patients With Glioblastoma: A Randomized, Triple-Blinded, Placebo-Controlled Clinical Trial

BACKGROUND

Glioblastoma is associated with low median survival time irrespective of maximal treatment. Previous in vitro studies have revealed tumor inhibitory effect of cyclosporine A. However, whether the addition of cyclosporine could improve survival among patients with glioblastoma is unknown. This study aimed to determine the impact of postoperation treatment with cyclosporine on the survival and performance status.

METHODS

In this randomized, triple-blinded, placebo-controlled trial, 118 patients with glioblastoma who underwent surgery were treated with standard chemoradiotherapy regimen. Patients were randomized to receive intravenous cyclosporine for 3 days postoperatively or placebo during the same period. The primary endpoint was the short-term effect of intravenous cyclosporine on survival and Karnofsky performance scores. Secondary endpoints were chemoradiotherapy toxicity and neuroimaging features.

RESULTS

The overall survival (OS) in the cyclosporine (17.03 ± 5.8, 95% confidence interval: 11-17.37 months) group was statistically lower than in the placebo (30.53 ± 4.9, 95% confidence interval: 8-32.3 months) groups (P = 0.049). However, compared to the placebo group, a statistically higher percentage of patients in the cyclosporine group were alive at 12 months follow-up. Also, progression-free survival in the cyclosporine group was significantly prolonged than in the placebo group (6.3 ± 4.07 months vs. 3.4 ± 2.98 months, P < 0.001). In the multivariate analysis, age <50 years (P = 0.022) and gross total resection (P = 0.03) were significantly associated with OS.

CONCLUSIONS

Our study results demonstrated that administering postoperative cyclosporine does not improve OS and functional performance status. Notably, the survival rate was significantly dependent on the patient age and the extent of glioblastoma resection.

Polymorphism rs2395655 affects LEDGF/p75 binding activity and p21WAF1/CIP1 gene expression in esophageal squamous cell carcinoma

p21WAF1/CIP1 (p21) plays critical roles in cell‐cycle regulation and DNA repair and is transcriptionally regulated through p53‐dependent or ‐independent pathways. Bioinformatic analysis predicated one stress‐response element (STRE) implicated in single nucleotide polymorphism (SNP) rs2395655 of the p21 promoter. Here, we investigated the transcriptional regulatory function of rs2395655 variant genotype and analyzed its associations with the p21 expression and clinical outcomes in esophageal squamous cell carcinoma (ESCC) patients. Luciferase assay results showed significantly increased transcriptional activity of the rs2395655 G allele‐containing p21 promoter compared with rs2395655 A allele‐containing counterpart, especially in ESCC cells with ectopic LEDGF/p75 expression. Furthermore electrophoretic mobility shift assay using the rs2395655 G or A allele‐containing probe and chromatin immunoprecipitation assay with specific anti‐LEDGF/p75 antibody indicated the potential binding activity of LEDGF/p75 with the STRE element implicated in rs2395655 G allele of the p21 promoter. Subsequent specific RNA interference‐mediated depletion or ectopic expression of LEDGF/p75 caused obviously down‐ or up‐regulated expression of p21 mRNA in ESCC cells harboring rs2395655 GG genotype but not cells with rs2395655 AA genotype. Furthermore, rs2395655 GG genotype carriers showed significantly elevated p21 protein expression and conferred survival advantage in both univariate and multivariate analyses in total 218 ESCC patients. Our findings suggest that LEDGF/p75 regulates the p21 expression in ESCC cells through interacting with STRE element implicated in polymorphism rs2395655 and the elevated p21 protein expression and rs2395655GG genotype may serve as positive prognostic factors for ESCC patients.

CD99 inhibits neural differentiation of human Ewing sarcoma cells and thereby contributes to oncogenesis

Ewing sarcoma (EWS) is an aggressive bone tumor of uncertain cellular origin. CD99 is a membrane protein that is expressed in most cases of EWS, although its function in the disease is unknown. Here we have shown that endogenous CD99 expression modulates EWS tumor differentiation and malignancy. We determined that knocking down CD99 expression in human EWS cell lines reduced their ability to form tumors and bone metastases when xenografted into immunodeficient mice and diminished their tumorigenic characteristics in vitro. Further, reduction of CD99 expression resulted in neurite outgrowth and increased expression of beta-III tubulin and markers of neural differentiation. Analysis of a panel of human EWS cells revealed an inverse correlation between CD99 and H-neurofilament expression, as well as an inverse correlation between neural differentiation and oncogenic transformation. As knockdown of CD99 also led to an increase in phosphorylation of ERK1/2, we suggest that the CD99-mediated prevention of neural differentiation of EWS occurs through MAPK pathway modulation. Together, these data indicate a new role for CD99 in preventing neural differentiation of EWS cells and suggest that blockade of CD99 or its downstream molecular pathway may be a new therapeutic approach for EWS.

Double stranded-RNA-mediated activation of P21 gene induced apoptosis and cell cycle arrest in renal cell carcinoma

Small double stranded RNAs (dsRNA) are a new class of molecules which regulate gene expression. Accumulating data suggest that some dsRNA can function as tumor suppressors. Here, we report further evidence on the potential of dsRNA mediated p21 induction. Using the human renal cell carcinoma cell line A498, we found that dsRNA targeting the p21 promoter significantly induced the expression of p21 mRNA and protein levels. As a result, dsP21 transfected cells had a significant decrease in cell viability with a concomitant G1 arrest. We also observed a significant increase in apoptosis. These findings were associated with a significant decrease in survivin mRNA and protein levels. This is the first report that demonstrates dsRNA mediated gene activation in renal cell carcinoma and suggests that forced over-expression of p21 may lead to an increase in apoptosis through a survivin dependent mechanism.

Stable interference of EWS-FLI1 in an Ewing sarcoma cell line impairs IGF-1/IGF-1R signalling and reveals TOPK as a new target

BACKGROUND

Ewing sarcoma is a paradigm of solid tumour -bearing chromosomal translocations resulting in fusion proteins that act as deregulated transcription factors. Ewing sarcoma translocations fuse the EWS gene with an ETS transcription factor, mainly FLI1. Most of the EWS-FLI1 target genes still remain unknown and many have been identified in heterologous model systems.

METHODS

We have developed a stable RNA interference model knocking down EWS-FLI1 in the Ewing sarcoma cell line TC71. Gene expression analyses were performed to study the effect of RNA interference on the genetic signature of EWS-FLI1 and to identify genes that could contribute to tumourigenesis.

RESULTS

EWS-FLI1 inhibition induced apoptosis, reduced cell migratory and tumourigenic capacities, and caused reduction in tumour growth. IGF-1 was downregulated and the IGF-1/IGF-1R signalling pathway was impaired. PBK/TOPK (T-LAK cell-originated protein kinase) expression was decreased because of EWS-FLI1 inhibition. We showed that TOPK is a new target gene of EWS-FLI1. TOPK inhibition prompted a decrease in the proliferation rate and a dramatic change in the cell's ability to grow in coalescence.

CONCLUSION

This is the first report of TOPK activity in Ewing sarcoma and suggests a significant role of this MAPKK-like protein kinase in the Ewing sarcoma biology.

Phosphorylated extracellular signal-regulated protein kinases 1 and 2 phosphorylate Sp1 on serine 59 and regulate cellular senescence via transcription of p21Sdi1/Cip1/Waf1

Expression of p21(Sdi1) downstream of p53 is essential for induction of cellular senescence, although cancer cell senescence can also occur in the p53 null condition. We report herein that senescence-associated phosphorylated extracellular signal-regulated protein kinases 1 and 2 (SA-pErk1/2) enhanced p21(Sdi1) transcription by phosphorylating Sp1 on Ser(59) downstream of protein kinase C (PKC) alpha. Reactive oxygen species (ROS), which was increased in cellular senescence, significantly activated both PKCalpha and PKCbetaI. However, PKCalpha, but not PKCbetaI, regulated ROS generation and cell proliferation in senescent cells along with activation of cdk2, proven by siRNAs. PKCalpha-siRNA also reduced SA-pErk1/2 expression in old human diploid fibroblast cells, accompanied with changes of senescence phenotypes to young cell-like. Regulation of SA-pErk1/2 was also confirmed by using catalytically active PKCalpha and its DN-mutant construct. These findings strongly suggest a new pathway to regulate senescence phenotypes by ROS via Sp1 phosphorylation between PKCalpha and SA-pErk1/2: employing GST-Sp1 mutants and MEK inhibitor analyses, we found that SA-pErk1/2 regulated Sp1 phosphorylation on the Ser(59) residue in vivo, but not threonine, in cellular senescence, which regulated transcription of p21(Sdi1) expression. In summary, PKCalpha, which was activated in senescent cells by ROS strongly activated Erk1/2, and the SA-pErk1/2 in turn phosphorylated Sp1 on Ser(59). Sp1-enhanced transcription of p21(Sdi1) resulted in regulation of cellular senescence in primary human diploid fibroblast cells.

Antitumor effect of dsRNA-induced p21(WAF1/CIP1) gene activation in human bladder cancer cells

We recently reported that synthetic dsRNAs targeting promoter regions can induce gene expression in a phenomenon referred to as dsRNA-induced gene activation/RNA activation (RNAa) [Li et al. Proc Natl Acad Sci U S A 2006;103:17337-42]. The present study investigates the in vitro antitumor activity RNAa can elicit through triggering the expression of cell cycle repressor protein p21(WAF1/CIP1) (p21) in human bladder cancer cells. Transfection of a 21-nucleotide dsRNA targeting the p21 promoter (dsP21) was used to induce p21 expression in T24 and J82 bladder cancer cell lines. Reverse transcription-PCR and Western blot analysis accessed the increase p21 mRNA and protein levels, respectively, in transfected cells. In association to p21 induction, dsP21 transfection significantly inhibited bladder cancer cell proliferation and clonogenicity. Further analysis of cell viability and cell cycle distribution revealed that dsP21 transfection also enhanced apoptotic cell death and caused an accumulation in the G(1) phase in both cell lines. In conclusion, p21 activation by RNAa has antitumor activity in vitro in bladder cancer cells. These results suggest that RNAa could be used for cancer treatment by targeted activation of tumor suppressor genes.