Allelic imbalance on chromosome 2q and alterations of the caspase 8 gene in neuroblastoma

Metastasis in neuroblastoma: the MYCN question

Oncogenic drivers like MYCN in neuroblastoma subsets continues to present a significant challenge owing to its strong correlation with high-risk metastatic disease and poor prognosis. However, only a limited number of MYCN-regulatory proteins associated with tumor initiation and progression have been elucidated. In this minireview, I summarize the recent progress in understanding the functional role of MYCN and its regulatory partners in neuroblastoma metastasis.

Cancer Immunoediting: Elimination, Equilibrium, and Immune Escape in Solid Tumors

Emphasizing the dynamic processes between cancer and host immune system, the initially discovered concept of cancer immunosurveillance has been replaced by the current concept of cancer immunoediting consisting of three phases: elimination, equilibrium, and escape. Solid tumors composed of both cancer and host stromal cells are an example how the three phases of cancer immunoediting functionally evolve and how tumor shaped by the host immune system gets finally resistant phenotype. The elimination, equilibrium, and escape have been described in this chapter in details, including the role of immune surveillance, cancer dormancy, disruption of the antigen-presenting machinery, tumor-infiltrating immune cells, resistance to apoptosis, as well as the function of tumor stroma, microvesicles, exosomes, and inflammation.

Lamellipodin-RICTOR Signaling Mediates Glioblastoma Cell Invasion and Radiosensitivity Downstream of EGFR

Glioblastoma is a tumor type of unmet need despite the development of multimodal treatment strategies. The main factors contributing to the poor prognosis of glioblastoma patients are diverse genetic and epigenetic changes driving glioblastoma persistence and recurrence. Complemented are these factors by extracellular cues mediated through cell surface receptors, which further aid in fostering pro-invasion and pro-survival signaling contributing to glioblastoma therapy resistance. The underlying mechanisms conferring this therapy resistance are poorly understood. Here, we show that the cytoskeleton regulator Lamellipodin (Lpd) mediates invasiveness, proliferation and radiosensitivity of glioblastoma cells. Phosphoproteome analysis identified the epidermal growth factor receptor (EGFR) signaling axis commonly hyperactive in glioblastoma to depend on Lpd. Mechanistically, EGFR signaling together with an interaction between Lpd and the Rapamycin-insensitive companion of mammalian target of rapamycin (RICTOR) jointly regulate glioblastoma radiosensitivity. Collectively, our findings demonstrate an essential function of Lpd in the radiation response and invasiveness of glioblastoma cells. Thus, we uncover a novel Lpd-driven resistance mechanism, which adds an additional critical facet to the complex glioblastoma resistance network.

Cytotoxic Efficacy and Resistance Mechanism of a TRAIL and VEGFA-Peptide Fusion Protein in Colorectal Cancer Models

TNF-related apoptosis-inducing ligand (TRAIL) is a type II transmembrane protein capable of selectively inducing apoptosis in cancer cells by binding to its cognate receptors. Here, we examined the anticancer efficacy of a recently developed chimeric AD-O51.4 protein, a TRAIL fused to the VEGFA-originating peptide. We tested AD-O51.4 protein activity against human colorectal cancer (CRC) models and investigated the resistance mechanism in the non-responsive CRC models. The quantitative comparison of apoptotic activity between AD-O51.4 and the native TRAIL in nine human colorectal cancer cell lines revealed dose-dependent toxicity in seven of them; the immunofluorescence-captured receptor abundance correlated with the extent of apoptosis. AD-O51.4 reduced the growth of CRC patient-derived xenografts (PDXs) with good efficacy. Cell lines that acquired AD-O51.4 resistance showed a significant decrease in surface TRAIL receptor expression and apoptosis-related proteins, including Caspase-8, HSP60, and p53. These results demonstrate the effectiveness of AD-O51.4 protein in CRC preclinical models and identify the potential mechanism underlying acquired resistance. Progression of AD-O51.4 to clinical trials is expected.

Association of RASSF1A, DCR2, and CASP8 Methylation with Survival in Neuroblastoma: A Pooled Analysis Using Reconstructed Individual Patient Data

Neuroblastoma (NB) is a heterogeneous tumor affecting children. It shows a wide spectrum of clinical outcomes; therefore, development of risk stratification is critical to provide optimum treatment. Since epigenetic alterations such as DNA methylation have emerged as an important feature of both development and progression in NB, in this study, we aimed to quantify the effect of methylation of three distinct genes (RASSF1A, DCR2, and CASP8) on overall survival in NB patients. We performed a systematic review using PubMed, Embase, and Cochrane libraries. Individual patient data was retrieved from extracted Kaplan–Meier curves. Data from studies was then merged, and analysis was done on the full data set. Seven studies met the inclusion criteria. Methylation of the three genes had worse overall survival than the unmethylated arms. Five-year survival for the methylated arm of RASSF1A, DCR2, and CASP8 was 63.19% (95% CI 56.55-70.60), 57.78% (95% CI 47.63-70.08), and 56.39% (95% CI 49.53-64.19), respectively, while for the unmethylated arm, it was 93.10% (95% CI 87.40–99.1), 84.84% (95% CI 80.04-89.92), and 83.68% (95% CI 80.28-87.22), respectively. In conclusion, our results indicate that in NB patients, RASSF1A, DCR2, and CASP8 methylation is associated with poor prognosis. Large prospective studies will be necessary to confirm definitive correlation between methylation of these genes and survival taking into account all other known risk factors. (PROSPERO registration number CRD42017082264).

Association of CASP8 polymorphisms and cancer susceptibility: A meta-analysis

Caspase-8 plays is an essential enzyme in apoptosis pathway. Several investigation have been done to identify the relation between CASP8 polymorphisms and different human cancers, but, the findings are still debated. The aim of the current investigation is to assess if CASP8 rs3834129 (-652 6N insertion/deletion), rs1045485 G > C, rs3769818 G > A, rs6723097 A > C, rs3769821 T > C, rs13113 T > A, rs3769825 G > A, rs2293554 A > C, and rs10931936 C > T polymorphisms are linked to susceptibility of cancer. Our team has extracted the eligible studies up to July 4, 2019, from different sources. Pooled odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were estimated to quantitatively evaluate the association between CASP8 polymorphisms and cancer susceptibility. Our results showed that the rs3834129 and rs1045485 polymorphisms meaningfully reduced the risk of cancer, while the rs3769818, rs3769821 and rs3769825 polymorphisms considerably increased cancer susceptibility. No association of rs6723097, rs13113, rs2293554 and rs10931936 polymorphisms was observed with cancer susceptibility. The CASP8 rs3834129 polymorphism reduced the risk of gastrointestinal, digestive tract, colorectal, breast and lung cancers. Furthermore, the cancer risk was decreased in Asian and Caucasian populations as well as population- and hospital-based studies due to this polymorphism. There was not any relation between this gene polymorphism and the risk of prostate and cervical cancer development. Regarding the CASP8 rs1045485 polymorphism, the reduced breast cancer risk along with the risk of cancer in Caucasians, population- and hospital-based studies were observed.

ING5 inhibits cancer aggressiveness by inhibiting Akt and activating p53 in prostate cancer

Prostate cancer (PCa) is one of the most common types of cancer in men. In several recent studies, chromosomal deletions in the q arm of chromosome 2, where ING5 resides within, have been identified in various cancer types including PCa. In this study, we investigate the role of ING5 as a tumor suppressor in PCa. We examined the expression level of ING5 in tissue samples and cell lines using quantitative real-time polymerase chain reaction and western blot analysis. We tested the in vitro tumor suppressor potential of ING5 in PC3 and LNCaP cells stably overexpressing it using cell viability, colony formation, migration, invasion, and apoptosis assays. We then investigated the effects of ING5 on the Akt and p53 signaling using western blot analysis. We show that ING5 is significantly downregulated in PCa tumor tissue samples and cell lines compared with the corresponding controls. In vitro assays demonstrate that ING5 effectively suppresses proliferative, clonogenic, migratory, and invasive potential and induce apoptosis in PCa cells. ING5 may potentially exert its anti-tumor potential by inhibiting AKT and inducing p53 signaling pathways. Our findings demonstrate that ING5 possesses tumor suppressor roles in vitro, pointing its importance during the prostatic carcinogenesis processes.

Copy number variation in archival melanoma biopsies versus benign melanocytic lesions

BACKGROUND

Skin melanocytes can give rise to benign and malignant neoplasms. Discrimination of an early melanoma from an unusual/atypical benign nevus can represent a significant challenge. However, previous studies have shown that in contrast to benign nevi, melanoma demonstrates pervasive chromosomal aberrations.

OBJECTIVE

This substantial difference between melanoma and benign nevi can be exploited to discriminate between melanoma and benign nevi.

METHODS

Array-comparative genomic hybridization (aCGH) is an approach that can be used on DNA extracted from formalin-fixed paraffin-embedded (FFPE) tissues to assess the entire genome for the presence of changes in DNA copy number. In this study, high resolution, genome-wide single-nucleotide polymorphism (SNP) arrays were utilized to perform comprehensive and detailed analyses of recurrent copy number aberrations in 41 melanoma samples in comparison with 21 benign nevi.

RESULTS

We found statistically significant copy number gains and losses within melanoma samples. Some of the identified aberrations are previously implicated in melanoma. Moreover, novel regions of copy number alterations were identified, revealing new candidate genes potentially involved in melanoma pathogenesis.

CONCLUSIONS

Taken together, these findings can help improve melanoma diagnosis and introduce novel melanoma therapeutic targets.

CASP8 SNP D302H (rs1045485) is associated with worse survival in MYCN-amplified neuroblastoma patients

Background

Neuroblastoma is a pediatric cancer that exhibits a wide clinical spectrum ranging from spontaneous regression in low-risk patients to fatal disease in high-risk patients. The identification of single nucleotide polymorphisms (SNPs) may help explain the heterogeneity of neuroblastoma and assist in identifying patients at higher risk for poor survival. SNPs in the TP53 pathway are of special importance, as several studies have reported associations between TP53 pathway SNPs and cancer. Of note, less than 2% of neuroblastoma tumors have a TP53 mutation at diagnosis.

Patients and Methods

We selected 21 of the most frequently studied SNPs in the TP53 pathway and evaluated their association with outcome in 500 neuroblastoma patients using TaqMan allelic discrimination assays.

Results and Conclusion

We investigated the impact of 21 SNPs on overall survival, event-free survival, age at diagnosis, MYCN status, and stage of the disease in 500 neuroblastoma patients. A missense SNP in exon 10 of the CASP8 gene SNP D302H was associated with worse overall and event-free survival in patients with MYCN-amplified neuroblastoma tumors.

Mitochondrial dysfunction in cancer

Mitochondria are semi-autonomous organelles of eukaryotic cells. They perform crucial functions such as generating most of the cellular energy through the oxidative phosphorylation (OXPHOS) system and some other metabolic processes. In addition, mitochondria are involved in regulation of cell death and reactive oxygen species (ROS) generation. Also, mitochondria play important roles in carcinogenesis via altering energy metabolism, resistance to apoptosis, increase of production of ROS and mtDNA (mitochondrial genome) changes. Studies have suggested that aerobic glycolysis is high in malignant tumors. Probably, it correlates with high glucose intake of cancerous tissues. This observation is contrary to Warburg's theory that the main way of energy generation in cancer cells is non-oxidative glycolysis. Further studies have suggested that in tumor cells both oxidative phosphorylation and glycolysis were active at various rates.

An increase of intracellular oxidative stress induces damage of cellular structure and somatic mutations. Further studies confirmed that permanent activity of oxidative stress and the influence of chronic inflammation damage the healthy neighboring epithelium and may lead to carcinogenesis. For instance, chronic inflammatory bowel disease could be related to high risk of colon adenocarcinoma.

The data have shown a role of ROS generation, mtDNA or nDNA alterations and abnormal apoptotic machinery in endometrial cancer progress. Recent studies suggest that mtDNA mutations might play a potential role in endometrial cancer progress and indicate an increase of mitochondrial biogenesis in this cancer. The investigators suggested that MtCOI and MtND6 alteration has an influence on assembly of respiratory complexes in endometrial cancer.

In many human cancers, there is a deregulation of the balance between cell growth and death. The tumor cells can avoid apoptosis through a loss of balance between anti- and pro-apoptotic proteins, reduced caspase function and impaired death receptor signaling. Over-expression of the anti-apoptotic BCL-2 gene has also been identified in numerous cancers including colon, thyroid, breast and endometrial cancer. Most studies have found low BCL-2 family gene expression, which could be a sign of blocking apoptosis in breast and endometrial cancer. Moreover, BCL-2 gene expression is correlated with the degree of aggressiveness and differentiation in endometrial cancer. As a result, it could be a valuable predictor of disease progression.

Identification of a secondary promoter of CASP8 and its related transcription factor PURα

Caspase-8 (CASP8) is an essential initiator of apoptosis and is associated with many diseases in humans including esophageal squamous cell carcinoma. CASP8 produces a variety of transcripts, which might perform distinct functions. However, the cis and trans transcriptional determinants that control CASP8 expression remain poorly defined. Using a series of luciferase reporter assays, we identified a novel secondary promoter of CASP8 within chr2: 202,122,236 to 202,123,227 and 25 kb downstream of the previously described CASP8 promoter. ENCODE ChIP-seq data for this novel promoter region revealed several epigenetic features, including high levels of histone H3 lysine 27 acetylation and lysine 4 methylation, as well as low levels of CpG island methylation. We developed a mass spectrometry based strategy to identify transcription factors that contribute to the function of the secondary promoter. We found that the transcription activator protein PURα is specifically involved in the transcriptional activation of the secondary promoter and may exert its function by forming a complex with E2F-1 and RNA polymerase II. PURα can bind to both DNA and RNA, and functions in the initiation of DNA replication, regulation of transcription. We observed that knockdown of PURα expression decreased the transcriptional activity of the secondary promoter and mRNA expression of CASP8 isoform G. Although the physiologic roles of this secondary promoter remain unclear, our data may help explain the complexity of CASP8 transcription and suggest that the various caspase 8 isoforms may have distinct regulations and functions.

RASSF1A methylation may have two biological roles in neuroblastoma tumorigenesis depending on the ploidy status and age of patients

RASSF1A methylation was frequent in neuroblastomas found in infants by mass-screening or infants and children diagnosed clinically, whereas CASP8 and DCR2 methylation was only frequent in tumors in children. When classified according to the ploidy status, RASSF1A and PCDHB methylation was only associated with MYCN amplification and poor outcomes in infants with a clinically diagnosed diploid, not triploid tumor. RASSF1A and PCDHB methylation was associated with poor outcomes in children with triploid and diploid tumors, respectively, and with MYCN amplification in children with diploid tumor. RASSF1A methylation may have two biological roles based on the ploidy status and patient's age.

Genome-wide approach to identify second gene targets for malignant rhabdoid tumors using high-density oligonucleotide microarrays

Malignant rhabdoid tumor (MRT) is a rare and highly lethal cancer that mainly affects infants and young children. The majority of MRT are characterized by loss of function of SMARCB1 on chromosome 22q11.2. However, little is known about genetic changes other than SMARCB1 alterations that are responsible for the development and/or progression of MRT. To explore additional gene targets in MRT, we analyzed 21 MRT specimens (12 fresh tumors and 9 MRT-derived cell lines) using high-density single nucleotide polymorphism genotyping microarrays. Although MRT genomes are characterized by common 22q11.2 deletions, affecting the SMARCB1 locus with a frequency of 95.2% (20/21 specimens), other genetic changes have been less frequent. Of the 20 specimens with deletions of 22q11.2, eight specimens showed uniparental disomy of the SMARCB1 locus with homozygous deletions or gene mutations. High-resolution analysis also disclosed the recurrent hemizygous/homozygous deletions of 7q35–q36.1, involving the CNTNAP2 locus in three specimens. Mutations analysis of CNTNAP2 showed a novel R157C missense mutation in a primary case, and methylation analysis showed recurrent hypermethylation of CNTNAP2 in three of nine cell lines. These results demonstrated that CNTNAP2 is one of the additional gene targets, other than SMARCB1, in MRT.

Amplification and deletion of the RAPH1 gene in breast cancer patients

Lamellipodin protein (Lpd), encoded by the RAPH1 gene, modulates the assembly of actin cytoskeleton through its binding to the Ena/VASPs proteins, and acts in cellular motility and lamelipodial protrusion. The region where RAPH1 gene is located (2q33) is deleted in various types of cancer and the gene expression changes in tumors when compared to normal tissues. Amplifications and deletions of the RAPH1 gene were investigated in breast carcinoma samples, in order to determine the possible relationship of the gene with breast cancer tumorigenesis and lymph node metastasis. RAPH1 gene alterations were determined by relative quantification, standard curve method using Real-time PCR technique in samples of tumor and peripheral blood from 52 patients. Regression and correlation analyses were conducted using gene alterations and clinicopathological data. All samples analyzed were altered, with 63.5 % deletion cases and 36.5 % amplification cases. The logistic regression and correlation analysis with clinicopathological data did not show significant results. The results suggest that although the RAPH1 gene was deleted or amplified in all samples, the Lpd does not seem to play a major role in tumorigenesis of mammary carcinomas and probably other proteins, also involved in the process of cellular motility and metastasis, are acting more effectively for or against the migration of breast tumor cells.

Methylation of TMEFF2 gene in tissue and serum DNA from patients with non-small cell lung cancer

Lung cancer remains a global health problem with a high mortality rate. CpG island methylation is a common aberration frequently associated with gene silencing in multiple tumor types, emerging as a highly promising biomarker. The transmembrane protein with a single EGF-like and two follistatin domains (TMEFF2) is epigenetically silenced in numerous tumor types, suggesting a potential role as a potential tumor suppressor. However, the role of TMEFF2 in lung cancer remains to be fully elucidated. We explored the methylation status of TMEFF2 gene in 139 patients with non-small cell lung cancer (NSCLC) and the feasibility of detecting circulating methylated DNA as a screening tool for NSCLC using methylation-specific PCR in 316 patients and 50 age-matched health controls. TMEFF2 methylation in tumor tissues was found in 73 of the 139 NSCLCs (52.5%) and was related to gene expression. The frequency of TMEFF2 methylation was higher in females and never-smokers than in males and smokers with borderline significance (65.8% vs 47.8%, p = 0.06; 65.7% vs 48.1%, p = 0.07). Notably, in adenocarcinomas, TMEFF2 methylation was significantly more frequent in tumors without EGFR mutation than those with EGFR mutation (adjusted odds ratio = 7.13, 95% confidence interval = 2.05-24.83, P = 0.002). Furthermore, TMEFF2 methylation was exclusively detected in the serum of NSCLC patients at a frequency of 9.2% (29/316). These findings suggest that methylation-associated down-regulation of TMEFF2 gene may be involved in lung tumorigenesis and TMEFF2 methylation can serve as a specific blood-based biomarker for NSCLC.

Aberrant activation of ALK kinase by a novel truncated form ALK protein in neuroblastoma

Anaplastic lymphoma kinase (ALK) was originally identified from a rare subtype of non-Hodgkin's lymphomas carrying t(2;5)(p23;q35) translocation, where ALK was constitutively activated as a result of a fusion with nucleophosmin (NPM). Aberrant ALK fusion proteins were also generated in inflammatory fibrosarcoma and a subset of non-small-cell lung cancers, and these proteins are implicated in their pathogenesis. Recently, ALK has been demonstrated to be constitutively activated by gene mutations and/or amplifications in sporadic as well as familial cases of neuroblastoma. Here we describe another mechanism of aberrant ALK activation observed in a neuroblastoma-derived cell line (NB-1), in which a short-form ALK protein (ALK(del2-3)) having a truncated extracellular domain is overexpressed because of amplification of an abnormal ALK gene that lacks exons 2 and 3. ALK(del2-3) was autophosphorylated in NB-1 cells as well as in ALK(del2-3)-transduced cells and exhibited enhanced in vitro kinase activity compared with the wild-type kinase. ALK(del2-3)-transduced NIH3T3 cells exhibited increased colony-forming capacity in soft agar and tumorigenicity in nude mice. RNAi-mediated ALK knockdown resulted in the growth suppression of ALK(del2-3)-expressing cells, arguing for the oncogenic role of this mutant. Our findings provide a novel insight into the mechanism of deregulation of the ALK kinase and its roles in neuroblastoma pathogenesis.

Drug-induced caspase 8 upregulation sensitises cisplatin-resistant ovarian carcinoma cells to rhTRAIL-induced apoptosis

Background:

Drug resistance is a major problem in ovarian cancer. Triggering apoptosis using death ligands such as tumour necrosis factor-related apoptosis inducing ligand (TRAIL) might overcome chemoresistance.

Methods:

We investigated whether acquired cisplatin resistance affects sensitivity to recombinant human (rh) TRAIL alone or in combination with cisplatin in an ovarian cancer cell line model consisting of A2780 and its cisplatin-resistant subline CP70.

Results:

Combining cisplatin and rhTRAIL strongly enhanced apoptosis in both cell lines. CP70 expressed less caspase 8 protein, whereas mRNA levels were similar compared with A2780. Pre-exposure of particularly CP70 to cisplatin resulted in strongly elevated caspase 8 protein and mRNA levels. Caspase 8 mRNA turnover and protein stability in the presence or absence of cisplatin did not differ between both cell lines. Cisplatin-induced caspase 8 protein levels were essential for the rhTRAIL-sensitising effect as demonstrated using caspase 8 small-interfering RNA (siRNA) and caspase-8 overexpressing constructs. Cellular FLICE-inhibitory protein (c-FLIP) and p53 siRNA experiments showed that neither an altered caspase 8/c-FLIP ratio nor a p53-dependent increase in DR5 membrane expression following cisplatin were involved in rhTRAIL sensitisation.

Conclusion:

Cisplatin enhances rhTRAIL-induced apoptosis in cisplatin-resistant ovarian cancer cells, and induction of caspase 8 protein expression is the key factor of rhTRAIL sensitisation.

The connections between neural crest development and neuroblastoma

Neuroblastoma (NB), the most common extracranial solid tumor in childhood, is an extremely heterogeneous disease both biologically and clinically. Although significant progress has been made in identifying molecular and genetic markers for NB, this disease remains an enigmatic challenge. Since NB is thought to be an embryonal tumor that is derived from precursor cells of the peripheral (sympathetic) nervous system, understanding the development of normal sympathetic nervous system may highlight abnormal events that contribute to NB initiation. Therefore, this review focuses on the development of the peripheral trunk neural crest, the current understanding of how developmental factors may contribute to NB and on recent advances in the identification of important genetic lesions and signaling pathways involved in NB tumorigenesis and metastasis. Finally, we discuss how future advances in identification of molecular alterations in NB may lead to more effective, less toxic therapies, and improve the prognosis for NB patients.

Changes in Activities of Caspase-8 and Caspase-9 in Human Cervical Malignancy

Introduction

The apoptotic process of programmed cell death and its dysfunctions in a variety of human diseases, including cervical cancer, has become the focus of extensive scientific research. Caspases are considered key factors in the execution of apoptosis, although there are many aspects of their role to be elucidated. It has been found that disturbance of initiator caspase-8 and caspase-9 expression or function may contribute to cancer formation/progression, and inactivation of them could promote resistance to current treatment approaches. In our research, the activities of caspase-8 and caspase-9 have been estimated during the progression of human cervical malignancy.

Materials and Methods

The experimental material includes human cervical tissue samples (normal and pathological), in which enzyme activities have been measured colorimetrically.

Results

Activities of caspase-8 and caspase-9 presented the highest increase, compared to the controls, in the low-grade squamous intraepithelial lesion samples (statistically significant, P < 0.01 by t test). The activities diminished in the high-grade squamous intraepithelial lesion and even more in the cancer samples but remained higher than the controls.

Conclusion

The observed changes in the activities of caspase-8 and caspase-9 could be attributed to their involvement in the cervical tissue's effort to resist malignancy progression.

Phase I study of decitabine with doxorubicin and cyclophosphamide in children with neuroblastoma and other solid tumors: a Children's Oncology Group study

BACKGROUND

Demethylating agents may alter the expression of genes involved in chemotherapy resistance. We conducted a phase I trial to determine the toxicity and molecular effects of the demethylating agent, decitabine, followed by doxorubicin and cyclophosphamide in children with refractory solid tumors.

PROCEDURE

Stratum A included children with any solid tumor; Stratum B included neuroblastoma patients only. Patients received a 1-hr decitabine infusion for 7 days, followed by doxorubicin (45 mg/m(2)) and cyclophosphamide (1 g/m(2)) on day 7. Pharmacokinetic studies were performed after the first dose of decitabine. Biological studies included methylation and gene expression analyses of caspase-8, MAGE-1 and fetal hemoglobin (HbF), and expression profiling of pre- and post-treatment peripheral blood and bone marrow cells.

RESULTS

The maximum-tolerated dose of decitabine was 5 mg/m(2)/day for 7 days. Dose-limiting toxicities at 10 mg/m(2)/day were neutropenia and thrombocytopenia. Decitabine exhibited rapid clearance from plasma. Three of 9 patients in Stratum A and 4/12 patients in Stratum B had stable disease for > or = 4 months. Sustained MAGE-1 demethylation and increased HbF expression were observed in the majority of patients post-treatment (12/20 and 14/16, respectively). Caspase-8 promoter demethylation and gene expression were seen in 2/7 bone marrow samples. Differentially expressed genes were identified by microarray analysis.

CONCLUSION

Low-dose decitabine when combined with doxorubicin/cyclophosphamide has tolerable toxicity in children. However, doses of decitabine capable of producing clinically relevant biologic effects were not well tolerated with this combination. Alternative strategies of combining demethylating agents with non-cytotoxic, biologically targeted agents such as histone deacetylase inhibitors should be explored.

Caspase-8 association with the focal adhesion complex promotes tumor cell migration and metastasis

Caspase-8 is a proapoptotic protease that suppresses neuroblastoma metastasis by inducing programmed cell death. Paradoxically, caspase-8 can also promote cell migration among nonapoptotic cells; here, we show that caspase-8 can promote metastasis when apoptosis is compromised. Migration is enhanced by caspase-8 recruitment to the cellular migration machinery following integrin ligation. Caspase-8 catalytic activity is not required for caspase-8-enhanced cell migration; rather, caspase-8 interacts with a multiprotein complex that can include focal adhesion kinase and calpain 2 (CPN2), enhancing cleavage of focal adhesion substrates and cell migration. Caspase-8 association with CPN2/calpastatin disrupts calpastatin-mediated inhibition of CPN2. In vivo, knockdown of either caspase-8 or CPN2 disrupts metastasis among apoptosis-resistant tumors. This unexpected molecular collaboration provides an explanation for the continued or elevated expression of caspase-8 observed in many tumors.

Oncogenic mutations of ALK kinase in neuroblastoma

Neuroblastoma in advanced stages is one of the most intractable paediatric cancers, even with recent therapeutic advances. Neuroblastoma harbours a variety of genetic changes, including a high frequency of MYCN amplification, loss of heterozygosity at 1p36 and 11q, and gain of genetic material from 17q, all of which have been implicated in the pathogenesis of neuroblastoma. However, the scarcity of reliable molecular targets has hampered the development of effective therapeutic agents targeting neuroblastoma. Here we show that the anaplastic lymphoma kinase (ALK), originally identified as a fusion kinase in a subtype of non-Hodgkin's lymphoma (NPM-ALK) and more recently in adenocarcinoma of lung (EML4-ALK), is also a frequent target of genetic alteration in advanced neuroblastoma. According to our genome-wide scans of genetic lesions in 215 primary neuroblastoma samples using high-density single-nucleotide polymorphism genotyping microarrays, the ALK locus, centromeric to the MYCN locus, was identified as a recurrent target of copy number gain and gene amplification. Furthermore, DNA sequencing of ALK revealed eight novel missense mutations in 13 out of 215 (6.1%) fresh tumours and 8 out of 24 (33%) neuroblastoma-derived cell lines. All but one mutation in the primary samples (12 out of 13) were found in stages 3-4 of the disease and were harboured in the kinase domain. The mutated kinases were autophosphorylated and displayed increased kinase activity compared with the wild-type kinase. They were able to transform NIH3T3 fibroblasts as shown by their colony formation ability in soft agar and their capacity to form tumours in nude mice. Furthermore, we demonstrate that downregulation of ALK through RNA interference suppresses proliferation of neuroblastoma cells harbouring mutated ALK. We anticipate that our findings will provide new insights into the pathogenesis of advanced neuroblastoma and that ALK-specific kinase inhibitors might improve its clinical outcome.

Aberrant methylation of candidate tumor suppressor genes in neuroblastoma

CpG island hypermethylation has been recognized as an alternative mechanism for tumor suppressor gene inactivation. In this study, we performed methylation-specific PCR (MSP) to investigate the methylation status of 10 selected tumor suppressor genes in neuroblastoma. Seven of the investigated genes (CD44, RASSF1A, CASP8, PTEN, ZMYND10, CDH1, PRDM2) showed high frequencies (> or =30%) of methylation in 33 neuroblastoma cell lines. In 42 primary neuroblastoma tumors, the frequencies of methylation were 69%, CD44; 71%, RASSF1A; 56%, CASP8; 25%, PTEN; 15%, ZMYND10; 8%, CDH1; and 0%, PRDM2. Furthermore, CASP8 and CDH1 hypermethylation was significantly associated with poor event-free survival. Meta-analysis of 115 neuroblastoma tumors demonstrated a significant correlation between CASP8 methylation and MYCN amplification. In addition, there was a correlation between ZMYND10 methylation and MYCN amplification. The MSP data, together with optimized mRNA re-expression experiments (in terms of concentration and time of treatment and use of proper reference genes) further strengthen the notion that epigenetic alterations could play a significant role in NB oncogenesis. This study thus warrants the need for a global profiling of gene promoter hypermethylation to identify genome-wide aberrantly methylated genes in order to further understand neuroblastoma pathogenesis and to identify prognostic methylation markers.

Comparison of different techniques for the detection of genetic risk-identifying chromosomal gains and losses in neuroblastoma

Neuroblastoma (NB) is a pediatric neoplasia that shows complex combinations of acquired genetic aberrations. The specific genes and the molecular mechanisms responsible for development and progression of NB remain poorly understood. Our main objective is to compare the results obtained with different techniques for the detection of genomic data in 20 patients with NB using the information obtained to select the appropriate technique in routine analysis for the therapeutic stratification. The genetic methods used in this study are multiprobe fluorescence in situ hybridization (FISH) assay, metaphasic comparative genomic hybridization (mCGH), array comparative genomic hybridization (aCGH), and the multiplex ligation-dependent probe amplification (MLPA). Genomic copy number abnormalities were used to group the cases in four categories: MYCN amplification cases; 11q deletion tumors; cases with partial chromosome gains or losses and samples with entire chromosome alterations. The data obtained from the multigenomic techniques showed a high degree of concordance and our findings support the hypothesis that NB consists of biologically distinct subgroups that differ by genetic characteristics of prognostic relevance. FISH will be essential for the mandatory study of MYCN status. The use of MLPA as routine technique is an advantage procedure for detecting the implication of the common genetic alterations in NB.

Array comparative genomic hybridization analysis of olfactory neuroblastoma

Olfactory neuroblastoma is an unusual neuroectodermal malignancy, which is thought to arise at the olfactory membrane of the sinonasal tract. Due to its rarity, little is understood regarding its molecular and cytogenetic abnormalities. The aim of the current study is to identify specific DNA copy number changes in olfactory neuroblastoma. Thirteen dissected tissue samples were analyzed using array comparative genomic hybridization. Our results show that gene copy number profiles of olfactory neuroblastoma samples are complex. The most frequent changes included gains at 7q11.22-q21.11, 9p13.3, 13q, 20p/q, and Xp/q, and losses at 2q31.1, 2q33.3, 2q37.1, 6q16.3, 6q21.33, 6q22.1, 22q11.23, 22q12.1, and Xp/q. Gains were more frequent than losses, and high-stage tumors showed more alterations than low-stage olfactory neuroblastoma. Frequent changes in high-stage tumors were gains at 13q14.2-q14.3, 13q31.1, and 20q11.21-q11.23, and loss of Xp21.1 (in 66% of cases). Gains at 5q35, 13q, and 20q, and losses at 2q31.1, 2q33.3, and 6q16-q22, were present in 50% of cases. The identified regions of gene copy number change have been implicated in a variety of tumors, especially carcinomas. In addition, our results indicate that gains in 20q and 13q may be important in the progression of this cancer, and that these regions possibly harbor genes with functional relevance in olfactory neuroblastoma.

TRAIL-R deficiency in mice enhances lymph node metastasis without affecting primary tumor development

TRAIL is a promising anticancer agent due to its ability to selectively induce apoptosis in established tumor cell lines but not nontransformed cells. Herein, we demonstrate a role for the apoptosis-inducing TRAIL receptor (TRAIL-R) as a metastasis suppressor. Although mouse models employing tumor transplantation have shown that TRAIL can reduce tumor growth, autochthonous tumor models have generated conflicting results with respect to the physiological role of the TRAIL system during tumorigenesis. We used a multistage model of squamous cell carcinoma to examine the role of TRAIL-R throughout all steps of tumor development. DMBA/TPA-treated TRAIL-R-deficient mice showed neither an increase in number or growth rate of benign papillomas nor an increase in the rate of progression to squamous cell carcinoma. However, metastasis to lymph nodes was significantly enhanced, indicating a role for TRAIL-R specifically in the suppression of metastasis. We also found that adherent TRAIL-R-expressing skin carcinoma cells were TRAIL resistant in vitro but were sensitized to TRAIL upon detachment by inactivation of the ERK signaling pathway. As detachment from the primary tumor is an obligatory step in metastasis, this provides a possible mechanism by which TRAIL-R could inhibit metastasis. Hence, treatment of cancer patients with agonists of the apoptosis-inducing receptors for TRAIL may prove useful in reducing the incidence of metastasis.

Onconase induces caspase-independent cell death in chemoresistant neuroblastoma cells

The efficacy of Onconase on the growth of a panel of chemosensitive and chemoresistant neuroblastoma cell lines was investigated. Onconase decreased cell viability of chemosensitive (IMR-32, UKF-NB-3) and chemoresistant neuroblastoma cell lines characterised by high expression of P-glycoprotein (P-gp) (UKF-NB-3(r)DOX(20)) or by high P-gp expression in combination with mutated p53 (UKF-NB-3(r)VCR(10), Be(2)-C), in a similar manner. Moreover, Onconase caused cell cycle block in G1 phase and induced caspase-independent cell death. Transmission electron microscope investigations suggested that Onconase-induced autophagy contributes to Onconase-induced cell death. Antitumour activity of Onconase against naïve and drug-resistant neuroblastoma xenografts was confirmed in animals.

Targeting caspase 8 to reduce the formation of metastases in neuroblastoma

The clinical challenge in neuroblastoma is the presence of metastasis at diagnosis in the majority of patients. Caspase 8 is an integral protein in death receptor-associated apoptosis, and loss of caspase 8 via the epigenetic phenomenon of methylation in neuroblastoma has led to increased resistance to chemotherapy. Recent evidence suggests that caspase 8 loss may also contribute to a metastatic phenotype; thus, caspase 8 may prove to be an attractive target for therapy both in treating primary tumours as well as preventing and treating metastatic lesions. Numerous methods have been described to manipulate caspase 8 levels both in vitro and in vivo, and investigation into caspase 8 isoforms may also bring forth additional therapeutic targets.

Multiple mechanisms underlie resistance of leukemia cells to Apo2 Ligand/TRAIL

Targeting death receptors with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has the remarkable potential to selectively kill malignant cells whereas normal cells are largely unaffected by this treatment. However, some tumor cells, including leukemia cells, exhibit resistance to this molecule. To investigate the basis for resistance of leukemia cells to the zinc-bound form of Apo2 ligand (Apo2L)/TRAIL, which is currently being evaluated in clinical trial, we isolated several resistant HL60 clones from parental HL60 cells by selection using the recombinant Apo2L/TRAIL. Differing resistance mechanisms were identified and characterized in these Apo2L/TRAIL-resistant clones. In one case, the level of the cell-surface death receptor DR4, but not DR5, was significantly decreased. However, these cells did undergo apoptosis in response to another form of recombinant TRAIL, histidine-tagged TRAIL, suggesting differing contributions of DR4 and DR5 in the response to these two forms of TRAIL. In the case of other clones, expression of procaspase-8 protein was lost and this was associated with a novel Leu(22)-->Phe(22) point mutation in CASP-8 gene. These results show that cells within a given tumor can have widely distinct mechanisms underlying resistance to Apo2L/TRAIL.

Fine deletion mapping of chromosome 2q21-37 shows three preferentially deleted regions in oral cancer

We analysed the loss of heterozygosity (LOH) of long arm of chromosome 2 by using 16 polymorphic microsatellite markers in 39 matched oral normal and cancer tissues, and defined the deletional mapping of the region with putative tumor suppressor genes. LOH was detected at least one location in 33 of 39 (85%) tumor tissues. Frequent deletions were detected at the locations of microsatellite markers, D2S2304 (35%), D2S111 (40%), D2S155 (35%), D2S1327 (29%), D2S164 (29%), D2S125 (68%) and D2S140 (32%). Three preferentially deleted regions at 2q21-24, 2q33-35 and 2q37.3 were observed. Several candidate tumor suppressor genes in these regions such as LRP1B, CASP8, CASP10, BARD1, ILKAP, PPP1R7, and ING5, are located. Further molecular analysis of each gene should be performed to clarify their roles in oral carcinogenesis.

Mutations of the PTPN11 and RAS genes in rhabdomyosarcoma and pediatric hematological malignancies

PTPN11 has been identified as a causative gene in Noonan syndrome (NS), responsible for about 50% of cases of NS. Given the association between NS and an increased risk of some malignancies, notably leukemia and probably some solid tumors including neuroblastoma (NB) and rhabdomyosarcoma (RMS), recent studies have reported that gain-of-function somatic mutations in PTPN11 occur in some hematological malignancies, especially de novo juvenile myelomonocytic leukemia (JMML) and in some solid tumors such as NB, although at a low frequency. In a screen for mutations of PTPN11 in 7 cell lines and 30 fresh tumors of RMS and in 25 cell lines and 40 fresh tumors of NB, we identified a missense mutation (A72T) in an embryonal RMS patient. In the RMS samples, we also detected mutations of NRAS in 1 cell line and 1 patient; both mutations were in embryonal RMSs and had no PTPN11 mutations. No mutations of PTPN11 were detected in NB. In 95 leukemia cell lines and 261 fresh leukemia samples including 22 JMMLs, 9 kinds of missense mutations were detected in 17 leukemia samples, which included 11 (50.0%) mutations in JMML samples and lower frequencies in other hematological malignancies. Furthermore, we identified 4 (18.2%) NRAS mutations and 1 (4.5%) KRAS mutation in 5 JMML samples, 1 of which had a concomitant PTPN11 mutation. Our data suggest that mutations of PTPN11 as well as RAS play a role in the pathogenesis of not only myeloid hematological malignancies but also a subset of RMS malignancies.

Mutational analysis of proapoptotic caspase-9 gene in common human carcinomas

Mounting evidence indicates that deregulation of apoptosis is involved in the mechanisms of cancer development. Caspase-9 plays a crucial role in the initiation phase of the intrinsic apoptosis pathway. To explore the possibility that the genetic alterations of caspase-9 might be involved in the development of human cancers, we analyzed the entire coding region and all splice sites of the human caspase-9 gene for the detection of somatic mutations in a series of 353 cancers, including 180 gastric, 104 colorectal and 69 lung adenocarcinomas. Overall, we detected three somatic mutations of caspase-9, but all of the mutations were silent mutations. The mutations were observed in 2 of 104 colorectal carcinomas and 1 of 180 gastric carcinomas. These data indicate that the caspase-9 gene is rarely mutated in gastric, colorectal and lung adenocarcinomas, and suggest that caspase-9 gene mutation may not contribute to the pathogenesis of these cancers.

Molecular mediators of cell death in multistep carcinogenesis: a path to targeted therapy

A consistent, if not invariant, feature of cancer cells is the acquired ability to evade apoptosis. The pioneering work of Dr. Stan Korsmeyer was invaluable in characterizing the molecular foundations of cell death signaling mechanisms during normal development and during multistep carcinogenesis. This foundation now forms the basis for the rational design of therapeutic strategies to selectively activate cell death in cancer cell populations. These strategies are currently being evaluated in an increasing number of clinical trials targeting diverse tumor types.

Previously unidentified complex cytogenetic changes found in a pediatric case of solid-pseudopapillary neoplasm of the pancreas

Solid pseudopapillary neoplasm of the pancreas (SPNP) is a rare tumor with low malignant potential found in adolescent girls and young women. The pathogenesis of SPNP remains uncertain and its management is controversial. Genetic changes associated with SPNP have seldom been reported. We describe here the cytogenetic investigation of a case of SPNP in a 13-year-old girl whose tumor cells revealed two unrelated clones: one clone characterized by complex karyotypic changes, including breakpoints in two common fragile sites at chromosome 2, band q33, and chromosome 4, band q31, and the second clone defined by partial monosomy for chromosome X. Loss of heterozygosity for HRAS was also identified by array comparative genomic hybridization (a-CGH). These cumulative changes seem insufficient for activation of cell transformation, but could possibly play a role in priming the cell for future mutagenic events.

Therapeutic Modulation of Akt Activity and Antitumor Efficacy of Interleukin-12 Against Orthotopic Murine Neuroblastoma

BACKGROUND

Patients with advanced neuroblastoma have a poor prognosis. The antiapoptotic protein Akt has been implicated as a possible mediator of the resistance of human neuroblastoma cells to apoptosis; the proapoptotic protein Bid, is inhibited by activated Akt. Neuroblastoma has demonstrated responsiveness to immunotherapeutic approaches in preclinical studies, prompting investigation of new therapeutic strategies based on potentiation of the host immune response, including the use of systemic cytokines.

METHODS

We examined the antitumor efficacy and mechanisms of action of the central immunoregulatory cytokine interleukin-12 (IL-12) in mice bearing established orthotopic neuroblastoma tumors derived from murine TBJ and Neuro-2a cells. Cohorts of mice (10 mice/group) bearing established orthotopic neuroblastoma tumors were injected intraperitoneally with IL-12 or vehicle and monitored for survival. IL-12-induced apoptosis within the tumor microenvironment was investigated using ribonuclease protection assays, nuclear staining, and electron microscopy. Protein expression was determined via Western blot analysis and enzyme-linked immunosorbent assays. Confocal microscopy was used to examine the distribution of overexpressed Bid-enhanced green fluorescent protein fusion protein (Bid-EGFP) in TBJ cells. All statistical tests were two-sided.

RESULTS

IL-12 induced complete tumor regression and long-term survival of 8 (80%) of 10 mice bearing established neuroblastoma tumors compared with 1 (10%) of 10 control mice (P = .0055) and profound tumor cell apoptosis in vivo despite the fact that TBJ and Neuro-2a cells were resistant to receptor-mediated apoptosis in vitro. These cells expressed high levels of phosphorylated Akt, a key prosurvival molecule, and Akt inhibitors sensitized neuroblastoma cells to apoptosis mediated by IL-12-inducible cytokines including tumor necrosis factor-alpha and interferon-gamma in vitro. IL-12 increased the expression of proapoptotic genes and decreased Akt phosphorylation within established TBJ tumors in conjunction with activation and subcellular translocation of Bid.

CONCLUSIONS

Our results suggest that IL-12 overcomes a potentially critical mechanism of tumor self-defense in vivo by inhibiting Akt activity and imply that IL-12 may possess unique therapeutic activity against tumors that express high levels of activated Akt.

Cloning and Functional Characterization of the Murine Caspase-3 Gene Promoter

Several studies have shown that the levels of caspase-3 are upregulated under different conditions of apoptosis. Previously, we have shown that activation of T cells through the TCR leads to the upregulation of caspase-3 levels. These findings highlight the importance of regulating the expression of caspase-3 in order to prevent premature cell death. To better understand the regulation of the caspase-3 gene, a portion of the 5'- untranslated region was cloned, sequenced, and characterized. The segment of the 5'-flanking region of the caspase-3 gene was also cloned upstream of a luciferase reporter gene, demonstrating that this fragment contains promoter activity. Higher luciferase expression was found with several of the promoter deletion constructs in Jurkat T cells but not the mouse Neuro-2A neuroblastoma cell line, suggesting the presence of a T-cell-specific regulated region. The importance of these sequences is further supported by the genomic organization of the human and mouse caspase-3 promoter regions. These findings demonstrated that the -2245/+14 region of the caspase-3 promoter shows constitutive levels of expression, and that several regions of the promoter play a role in basal regulation. Finally, some of the conserved transcription factor binding sites identified between the human and mouse promoters appear to play an important role in lymphoid cells.

Caspase-8 levels correlate with the expression of signal transducer and activator of transcription 1 in high-grade but not lower grade neuroblastoma

BACKGROUND

Previous studies in advanced-stage neuroblastoma (NB) have shown a link between the silencing of caspase-8 and methylation of a regulatory region at the boundary between caspase-8 exon 3 and intron 3. However, a number of recent studies from NB cell lines have shown that the transcriptional regulation of caspase-8 may reside with interferon gamma-sensitive promoters through the action of transcription factors, such as signal transducer and activator of transcription 1 (STAT-1). In this study, the authors tested the hypothesis that there is a correlation between caspase-8 and STAT-1 protein expression levels that may be linked to methylation of the regulatory elements of either of these genes.

METHODS

Thirty clinical tumor samples of all stages, including 13 samples from patients with Stage 4 disease, were analyzed by quantitative immunoblotting for caspase-8 and STAT-1. The DNA methylation status of putative caspase-8 and STAT-1 regulatory elements were determined by bisulfite-modified sequencing analysis.

RESULTS

A significant correlation was observed between caspase-8 and STAT-1 protein levels in Stage 4 NB samples but not in lower stage NB samples. Caspase-8 and STAT-1 protein levels varied widely across all stages of NB and did not correlate with methylation of these genes.

CONCLUSIONS

A strong correlation was observed between STAT-1 levels and caspase-8 levels in clinical Stage 4 NB. This suggests that STAT-1 or similar transcription factors, and not methylation, may play a role in controlling caspase-8 levels in this illness. No evidence of such a correlation between caspase-8 and STAT-1 levels was observed in lower clinical stages, suggesting that mechanisms controlling caspase-8 expression in NB vary with clinical stage.

Potentiation of neuroblastoma metastasis by loss of caspase-8

Neuroblastoma, the most common paediatric solid tumour, arises from defective neural crest cells. Genetic alterations occur frequently in the most aggressive neuroblastomas. In particular, deletion or suppression of the proapoptotic enzyme caspase-8 is common in malignant, disseminated disease, although the effect of this loss on disease progression is unclear. Here we show that suppression of caspase-8 expression occurs during the establishment of neuroblastoma metastases in vivo, and that reconstitution of caspase-8 expression in deficient neuroblastoma cells suppressed their metastases. Caspase-8 status was not a predictor of primary tumour growth; rather, caspase-8 selectively potentiated apoptosis in neuroblastoma cells invading the collagenous stroma at the tumour margin. Apoptosis was initiated by unligated integrins by means of a process known as integrin-mediated death. Loss of caspase-8 or integrin rendered these cells refractory to integrin-mediated death, allowed cellular survival in the stromal microenvironment, and promoted metastases. These findings define caspase-8 as a metastasis suppressor gene that, together with integrins, regulates the survival and invasive capacity of neuroblastoma cells.

Shugoshin, a guardian for sister chromatid segregation

To ensure sister chromatids to be equally transmitted to daughter cells, it is imperative that physical association of sister chromatids is maintained during S, G2, and early mitosis until the onset of anaphase. Cohesion of sister chromatids in eukaryotes is largely achieved by the cohesin complex. In vertebrates, cohesin molecules are dissociated from chromosome arms but not from centromeres during prophase by the so-called prophase pathway. Although it remains unclear what is the molecular basis by which centromeric cohesin is retained, a flurry of recent studies have shed light on a family of proteins named Shugoshin (Sgo) that are evolutionarily conserved across eukaryotes. Sgo1 functions as a protector of centromeric cohesin during meiosis in yeast and during mitosis in high eukaryotes. Suppression of Sgo1 function results in premature separation of sister chromatids in both meiosis and mitosis. The discovery of members of the Sgo family may help to explain how centromeric cohesin is protected from dissociation from DNA until the onset of anaphase. Given the importance of chromosome cohesion in the maintenance of genomic stability, further characterization of Sgo1 and related molecules may also open up new avenues of research for developing new strategies for cancer intervention.

Mammalian initiator apoptotic caspases

Caspases are a conserved family of cysteine proteases. They play diverse roles in inflammatory responses and apoptotic pathways. Among the caspases is a subgroup whose primary function is to initiate apoptosis. Within their long prodomains, caspases-2, -9 and -12 contain a caspase activation and recruitment domain while caspases-8 and -10 bear death effector domains. Activation follows the recruitment of the procaspase molecule via the prodomain to a high molecular mass complex. Despite sharing some common features, other aspects of the biochemistry, substrate specificity, regulation and signaling mechanisms differ between initiator apoptotic caspases. Defects in expression or activity of these caspases are related to certain pathological conditions including neurodegenerative disorders, autoimmune diseases and cancer.

Caspase 8 is absent or low in many ex vivo gliomas

BACKGROUND

Better treatments are required urgently for patients with malignant glioma, which currently is incurable. Death ligands, such as tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), may offer promise for the treatment high-grade glioma if such ligands induce apoptotic signaling in vivo in glioma cells. Caspase 8 is required for death ligand signaling, and its levels may influence the sensitivity of glioma cells to death ligands. It also may act as a tumor suppressor protein. The authors analyzed caspase 8 expression levels in ex vivo glioma specimens and explored potential mechanisms of its regulation.

METHODS

Eleven glioblastomas, 5 anaplastic astrocytomas, and 3 low-grade astrocytomas were studied. The levels of caspase 8, caspase 10, cellular FLICE inhibitory protein (c-FLIP), and signal transducer and activator of transcription (STAT)-1 were assayed using quantitative immunoblotting. Caspase 8 mRNA was measured by Northern blot analysis. The methylation status of the caspase 8 gene was determined by bisulfate modification of genomic DNA, cloning, and sequencing. Statistical analyses were performed using nonparametric (Spearman) correlations.

RESULTS

Some ex vivo glioma samples lacked detectable caspase 8, with many expressing barely detectable levels. No tumors expressed significant amounts of caspase 10 or c-FLIP. A strong association was found between caspase 8 mRNA and protein levels. Neither expression of the transcription factor STAT-1 nor caspase 8 gene methylation correlated with caspase 8 levels.

CONCLUSIONS

The absence of caspase 8 protein in many resected glioma samples implied that many patients with glioma may not benefit from death ligand-based treatments, unless caspase 8 (or caspase 10) protein expression can be elevated. Demethylating agents are unlikely to boost caspase 8 levels in glioma cells, but treatments that increase caspase 8 mRNA levels may up-regulate expression of the protein.

Large-scale Transcriptome Analyses Reveal New Genetic Marker Candidates of Head, Neck, and Thyroid Cancer

A detailed genome mapping analysis of 213,636 expressed sequence tags (EST) derived from nontumor and tumor tissues of the oral cavity, larynx, pharynx, and thyroid was done. Transcripts matching known human genes were identified; potential new splice variants were flagged and subjected to manual curation, pointing to 788 putatively new alternative splicing isoforms, the majority (75%) being insertion events. A subset of 34 new splicing isoforms (5% of 788 events) was selected and 23 (68%) were confirmed by reverse transcription-PCR and DNA sequencing. Putative new genes were revealed, including six transcripts mapped to well-studied chromosomes such as 22, as well as transcripts that mapped to 253 intergenic regions. In addition, 2,251 noncoding intronic RNAs, eventually involved in transcriptional regulation, were found. A set of 250 candidate markers for loss of heterozygosis or gene amplification was selected by identifying transcripts that mapped to genomic regions previously known to be frequently amplified or deleted in head, neck, and thyroid tumors. Three of these markers were evaluated by quantitative reverse transcription-PCR in an independent set of individual samples. Along with detailed clinical data about tumor origin, the information reported here is now publicly available on a dedicated Web site as a resource for further biological investigation. This first in silico reconstruction of the head, neck, and thyroid transcriptomes points to a wealth of new candidate markers that can be used for future studies on the molecular basis of these tumors. Similar analysis is warranted for a number of other tumors for which large EST data sets are available.

Caspase-8 gene is frequently inactivated by the frameshift somatic mutation 1225_1226delTG in hepatocellular carcinomas

Evidence exists that alterations of the genes encoding apoptosis-related proteins contribute to either development or progression of human cancers. Caspase-8 plays a crucial role in the initiation phase of apoptosis. To explore the possibility that the genetic alteration of caspase-8 gene is involved in the development of hepatocellular carcinomas (HCCs), we have analysed the entire coding region of human caspase-8 gene for the detection of somatic mutations by polymerase chain reaction-single-strand conformation polymorphism in 69 HCCs with low-grade dysplastic nodule (LGDN, n=2) or high-grade dysplastic nodule (HGDN, n=2) or without any dysplastic nodules (n=65). Overall, we detected a total of nine somatic mutations in 69 HCCs (13.0%). Interestingly, all of the nine mutations were an identical frameshift mutation with two base-pair deletion (1225_1226delTG), which would result in a premature termination of amino-acid synthesis in the p10 protease subunit. In a patient sample, we detected the 1225_1226delTG mutation both in HCC and LDGN lesions, suggesting that caspase-8 mutation could be involved in the early stage of HCC carcinogenesis. We expressed the tumor-derived caspase-8 mutant in the cells and found that the mutant abolished cell death activity of caspase-8. Our data indicate that caspase-8 gene is frequently mutated in HCC and the majority of the mutations may be the frameshift mutation 1225_1226delTG. Also, the data suggest that caspase-8 gene mutation might lead to the loss of its cell death function and contribute to the pathogenesis of HCC.

CASPASE-8 Gene Is Inactivated by Somatic Mutations in Gastric Carcinomas

Several lines of evidence indicate that deregulation of apoptosis is involved in the mechanisms of cancer development. Caspase-8 activation plays a central role in the initiation phase of apoptosis. The aim of this study was to explore the possibility that genetic alteration of CASPASE-8 gene is involved in the development of human cancers, including gastric cancers. We have analyzed the entire coding region of human CASPASE-8 gene for the detection of somatic mutations in 162 gastric carcinomas (40 early and 122 advanced cancers), 185 non–small cell lung cancers, 93 breast carcinomas, and 88 acute leukemias by PCR-single-strand conformation polymorphism. Of the cancers analyzed, 13 cancers harbored CASPASE-8 somatic mutations. Interestingly, all of the mutations were detected in the advanced gastric cancers (10.7% of the 122 samples). We expressed the tumor-derived caspase-8 mutants in 293T, 293, and HT1080 cells and found that most of the mutants (9 of the 10 mutations tested) markedly decreased the cell death activity of caspase-8. In addition, in the cells with the inactivating caspase-8 mutants, cleavage of poly(ADP-ribose)polymerase was markedly reduced compared with that of wild-type caspase-8. The occurrence of CASPASE-8 mutation and the inactivation of cell death activity by the mutants suggest that CASPASE-8 gene mutation may affect the pathogenesis of gastric cancers, especially at the late stage of gastric carcinogenesis.

Lessons from TRAIL-resistance mechanisms in colorectal cancer cells: paving the road to patient-tailored therapy

Colorectal cancer is one of the leading causes of cancer-related deaths worldwide. Intrinsic, as well as acquired, resistance to chemotherapy remains a major problem in the treatment of this disease. It is, therefore, of great importance to develop new, patient-tailored, treatment strategies for colorectal cancer patients. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) acts through the pro-apoptotic DR4 and DR5 receptors in tumor cells without harming normal cells and will soon be tested in clinical trials as a novel anti-cancer agent. However, not all human colon cancer cell lines are sensitive to TRAIL due to intrinsic or acquired TRAIL-resistance. This review discusses the mechanisms and modulation of TRAIL-resistance in colon cancer cells. Cell sensitivity to TRAIL can be affected by TRAIL-receptor expression at the cell membrane, DR4/DR5 ratio and functionality of TRAIL-receptors. Additional intracellular factors leading to TRAIL-resistance affect the caspase 8/c-FLIP ratio, such as loss of caspase 8 and caspase 10 due to mutations or gene methylation, CARP-dependent degradation of active caspase 8 and changes in caspase 8 or c-FLIP expression levels. Further downstream in the TRAIL apoptotic pathway, Bax mutations, or increased expression of IAP family members, in particularly XIAP and survivin, also cause resistance. Chemotherapeutic drugs, NSAIDs, interferon-gamma and proteasome inhibitors can overcome TRAIL-resistance by acting on TRAIL-receptor expression or changing the expression of pro- or anti-apoptotic proteins.

Altered expression and deletion of RMO1 in osteosarcoma

In order to increase our understanding of the molecular events underlying osteosarcoma progression, the expression of approximately 950 genes was examined in 24 primary and metastatic osteosarcoma tumor specimens. A gene, RMO1, was isolated with decreased expression in metastatic samples. Real-Time PCR corroborated this pattern, revealing lower expression in the primary sample in 6 of 7 cases for which both primary and metastatic osteosarcoma samples were available from the same patient (p = 0.034). RMO1 is located at 2q33, a region of frequent loss of heterozygosity in cancer, and exhibited loss of heterozygosity in 6 out of 9 primary osteosarcoma tumor samples (67%). Loss of heterozygosity is evident in primary tumors while the decrease in gene expression is seen in the metastatic samples, indicating that these 2 events are separately implicated in cancer progression. Cloning of RMO1 revealed an open reading frame with multiple splice forms with significant homology to GRB7, 10 and 14 and MIG10 in the region containing a Pleckstrin homology domain and a Ras association domain, suggestive of a role in cell signaling and migration. Northern blot analysis indicated that RMO1 mRNA is ubiquitously expressed in tissues except for peripheral blood leukocytes. These data suggest that RMO1 may be a candidate for a protein involved in inhibiting tumor progression.