Smoothened as a new therapeutic target for human osteosarcoma

ClC-3 chloride channel modulates the proliferation and migration of osteosarcoma cells via AKT/GSK3β signaling pathway

In cultured human osteosarcoma (OS) cells, we recently demonstrated that insulin-like growth factors (IGF-1)-induced MG-63 and 143B human OS cells proliferation were consistent with increasing ClC-3 expression, and ClC-3 was up-regulated in cells with high metastatic potency. Blockade of ClC-3 greatly suppressed the phosphorylation activation of Akt/GSK3β. We also found that blockade of ClC-3 effectively down-regulated the expression of cyclin D1 and cyclin E, and caused activation of p27(KIP) and p21(CIP). The synthesized effects on these proteins which play a major role in cell cycle regulation bring about G0/G1 cell cycle arrest in MG-63 cells, and finally abrogate the cell proliferation. Besides, ClC-3 deletion attenuates OS cell migration via down-regulation the expression of MMP-2 and MMP-9. Such information suggests that ClC-3 might be a potential target for anti-OS.

Regulatory network of differentially expressed genes in metastatic osteosarcoma

The present study aimed to investigate the possible molecular mechanisms underlying the pathogenesis of metastatic osteosarcoma (OS), by examining the microarray expression profiles of normal samples, and metastatic and non‑metastatic OS samples. The GSE9508 gene expression profile was downloaded from the Gene Expression Omnibus database, which included 11 human metastatic OS samples, seven non‑metastatic OS samples and five normal samples. Pretreatment of the data was performed using the BioConductor package in R language, and the differentially expressed genes (DEGs) were identified by a t‑test. Furthermore, function and pathway enrichment analyses of the DEGs were conducted using a molecule annotation system. A differential co‑expression network was also constructed, and the submodules were screened using MCODE in Cytoscape. A total of 965 genes were identified as DEGs in metastatic OS. The DEGs were shown to participate in the regulation of DNA‑dependent transcription, the composition of the nucleus, cytoplasm and membrane, and protein and nucleotide binding. Furthermore, the screened DEGs were significantly associated with the ribosome, axon guidance and the cytokine‑cytokine receptor interaction pathway. Certain hub genes were identified in the constructed differential co‑expression network, including matrix metalloproteinase 1 (MMP1), smoothened (SMO), ewing sarcoma breakpoint region 1 (EWSR1) and fasciculation and elongation protein ζ‑1 (FEZ1). Brain selective kinase 2 (BRSK2) and aldo‑keto reductase family 1 member B10 (AKRIB10) were present in the screened submodules. The results of the present study suggest that genes, including MMP1, SMO, EWSR1, FEZ1, BRSK2 and AKRIB10, may be potential targets for the diagnosis and treatment of metastatic OS.

Ribosomal protein S3 regulates GLI2-mediated osteosarcoma invasion

It has been reported that GLI2 promotes proliferation, migration, and invasion of mesenchymal stem cell and osteosarcoma cells. To examine the molecular mechanisms of GLI2-mediated osteosarcoma metastasis, we performed a microarray analysis. The gene encoding ribosomal protein S3 (RPS3) was identified as a target of GLI2. Real-time PCR revealed that RPS3 was upregulated in osteosarcoma cell lines compared with normal osteoblast cells. Knockdown of GLI2 decreased RPS3 expression, whereas forced expression of a constitutively active form of GLI2 upregulated the expression of RPS3. RPS3 knockdown by siRNA decreased the migration and invasion of osteosarcoma cells. Although forced expression of constitutively active GLI2 increased the migration of human mesenchymal stem cells, knockdown of RPS3 reduced the up-regulated migration. In contrast, forced expression of RPS3 increased migration and invasion of osteosarcoma cells. Moreover, reduction of migration by GLI2 knockdown was rescued by forced expression of RPS3. Immunohistochemical analysis showed that RPS3 expression was increased in primary osteosarcoma lesions with lung metastases compared with those without. These findings indicate that GLI2-RPS3 signaling may be a marker of invasive osteosarcoma and a therapeutic target for patients with osteosarcoma.

GLI2 is a novel therapeutic target for metastasis of osteosarcoma

Aberrant activation of the Hedgehog (Hh) pathway has been reported in several malignancies. We previously demonstrated that knockdown of GLI2 inhibited proliferation of osteosarcoma cells through regulation of the cell cycle. In this study, we analyzed the function of GLI2 in the pathogenesis of osteosarcoma metastasis. Immunohistochemical studies showed that GLI2 was overexpressed in patient osteosarcoma specimens. Knockdown of GLI2 inhibited migration and invasion of osteosarcoma cells. In contrast, the forced expression of constitutively active GLI2 in mesenchymal stem cells promoted invasion. In addition, xenograft models showed that knockdown of GLI2 decreased lung metastasis of osteosarcomas. To examine clinical applications, we evaluated the efficacy of arsenic trioxide (ATO), which is a Food and Drug Administration-approved antitumor drug, on osteosarcoma cells. ATO treatment suppressed the invasiveness of osteosarcoma cells by inhibiting the transcriptional activity of GLI2. In addition, the combination of Hh inhibitors including ATO, vismodegib and GANT61 prevented migration and metastasis of osteosarcoma cells. Consequently, our findings suggested that GLI2 regulated metastasis as well as the progression of osteosarcomas. Inhibition of the GLI2 transcription may be an effective therapeutic method for preventing osteosarcoma metastasis.

ΔNp63α enhances the oncogenic phenotype of osteosarcoma cells by inducing the expression of GLI2

Background

ΔNp63, a splice variant of p63, is overexpressed and exhibits oncogenic activity in many cancers including pancreatic and breast cancer and promotes cell survival by inhibiting apoptosis. Despite its role in tumorigenesis, mechanistic activity of ΔNp63 mediated oncogenic function in osteosarcoma is poorly understood.

Methods

The expression levels of p63 isoforms in osteosarcoma cell lines were identified using quantitative techniques. Expression profiling using microarray, siRNA mediated loss-of-function, and chromatin immunoprecipitation assays were employed to identify novel ΔNp63α targets in p63-null osteosarcoma SaOS-2 cells that were engineered to express ΔNp63α. The phenotype of SaOS-2-ΔNp63α cells was assessed using wound-healing, colony formation, and proliferation assays.

Results

The comparative expression analyses identified ΔNp63α as the predominant p63 isoform expressed by invasive OS cell lines. Phenotypic analyses of SaOS-2-ΔNp63α cells in vitro indicate that ΔNp63α imparted tumorigenic attributes upon tumor cells. Further, we show that in osteosarcoma cells ΔNp63α directly regulated the transcription factor GLI2, which is a component of the hedgehog signaling pathway, and that functional interactions between ΔNp63α and GLI2 confer oncogenic properties upon OS cells.

Conclusions

Here, we report that GLI2 is the novel target gene of ΔNp63α and that ΔNp63α-GLI2 crosstalk in osteosarcoma cells is a necessary event in osteosarcoma progression. Defining the exact mechanisms involved in this interaction that mediate the pathogenesis of osteosarcoma promises to identify targets for drug therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-559) contains supplementary material, which is available to authorized users.

Expression and clinical significance of Shh/Gli-1 in papillary thyroid carcinoma

The Sonic Hedgehog (Shh) pathway affects cancer initiation, progression, and metastasis, but its role in papillary thyroid carcinoma (PTC) remains elusive. To characterize expression and clinical significance of Shh and the transcription factor Gli-1-the key elements of the Shh pathway in PTC tissues-we immunohistochemically examined Shh/Gli-1 expression in PTC tissues from 142 patients, along with adjacent non-cancerous tissues as controls. We reviewed 142 patients' clinical characteristics and analyzed their relationship with expression of Shh/Gli-1. Shh and Gli-1 were expressed in 64.1 % (91/142) and 47.9 % (68/142) in PTC tissues, respectively, compared with 16.9 % (24/142) and 9.2 % (13/142) of adjacent non-cancerous tissues. Gli-1 expression was significantly associated with patients' ages (P < 0.05) and lymph node metastasis (P < 0.01). Increased Shh and Gli-1 expression was significantly associated with tumor-node-metastasis (TNM) stage (P < 0.01). Shh and Gli-1 were expressed in 79.2 and 60.4 %, respectively, of PTC tumors larger than 10 mm. Shh was significantly associated with tumor size (P < 0.01). Shh and Gli-1 were expressed in 72.5 and 65.2 %, respectively, of patients with lymph node metastasis. Overall, we found increased expression of the main initiator Shh and transcription factor Gli-1 in Shh pathway in PTC tissues. The expression of Shh/Gli-1 was significantly associated with tumor size, clinical staging, and lymph node metastasis, indicating that aberrant activation of the Shh pathway is important to PTC occurrence and progression. Potentially, Shh/Gli-1 could be a diagnostic indicator and a marker of therapeutic response.

Characterization of human gene locus CYYR1: a complex multi-transcript system

Cysteine/tyrosine-rich 1 (CYYR1) is a gene we previously identified on human chromosome 21 starting from an in-depth bioinformatics analysis of chromosome 21 segment 40/105 (21q21.3), where no coding region had previously been predicted. CYYR1 was initially characterized as a four-exon gene, whose brain-derived cDNA sequencing predicts a 154-amino acid product. In this study we provide, with in silico and in vitro analyses, the first detailed description of the human CYYR1 locus. The analysis of this locus revealed that it is composed of a multi-transcript system, which includes at least seven CYYR1 alternative spliced isoforms and a new CYYR1 antisense gene (named CYYR1-AS1). In particular, we cloned, for the first time, the following isoforms: CYYR1-1,2,3,4b and CYYR1-1,2,3b, which present a different 3' transcribed region, with a consequent different carboxy-terminus of the predicted proteins; CYYR1-1,2,4 lacks exon 3; CYYR1-1,2,2bis,3,4 presents an additional exon between exon 2 and exon 3; CYYR1-1b,2,3,4 presents a different 5' untranslated region when compared to CYYR1. The complexity of the locus is enriched by the presence of an antisense transcript. We have cloned a long transcript overlapping with CYYR1 as an antisense RNA, probably a non-coding RNA. Expression analysis performed in different normal tissues, tumour cell lines as well as in trisomy 21 and euploid fibroblasts has confirmed a quantitative and qualitative variability in the expression pattern of the multi-transcript locus, suggesting a possible role in complex diseases that should be further investigated.

Blocking signaling at the level of GLI regulates downstream gene expression and inhibits proliferation of canine osteosarcoma cells

The Hedgehog-GLI signaling pathway is active in a variety of human malignancies and is known to contribute to the growth and survival of human osteosarcoma cells. In this study, we examined the expression and regulation of GLI transcription factors in multiple canine osteosarcoma cell lines and analyzed the effects of inhibiting GLI with GANT61, a GLI-specific inhibitor. Compared with normal canine osteoblasts, real-time PCR showed that GLI1 and GLI2 were highly expressed in two out of three cell lines and correlated with downstream target gene expression of PTCH1and PAX6. Treatment of canine osteosarcoma cells with GANT61 resulted in decreased expression of GLI1, GLI2, PTCH1, and PAX6. Furthermore, GANT61 inhibited proliferation and colony formation in all three canine osteosarcoma cell lines. The finding that GLI signaling activity is present and active in canine osteosarcoma cells suggests that spontaneously arising osteosarcoma in dogs might serve as a good model for future preclinical testing of GLI inhibitors.

Aberrant hedgehog signaling and clinical outcome in osteosarcoma

Despite the importance of Hedgehog signaling in bone development, the relationship between Hedgehog pathway expression and osteosarcoma clinical characteristics and outcome has not been investigated. In this study of 43 high-grade human osteosarcoma samples, we detected high expression levels of the Hedgehog ligand gene, IHH, and target genes, PTCH1 and GLI1, in most samples. Further analysis in tumors of patients with localized disease at diagnosis identified coexpression of IHH and PTCH1 exclusively in large tumors. Higher levels of IHH were observed more frequently in males and patients with higher levels of GLI1 were more responsive to chemotherapy. Subgroup analysis by tumor size and IHH expression indicated that the well-known association between survival and tumor size was further refined when IHH levels were taken into consideration.

GLI2 induces genomic instability in human keratinocytes by inhibiting apoptosis

Abnormal Sonic Hedgehog signalling leads to increased transcriptional activation of its downstream effector, glioma 2 (GLI2), which is implicated in the pathogenesis of a variety of human cancers. However, the mechanisms underlying the tumorigenic role of GLI2 remain elusive. We demonstrate that overexpression of GLI2-β isoform, which lacks the N-terminal repressor domain (GLI2ΔN) in human keratinocytes is sufficient to induce numerical and structural chromosomal aberrations, including tetraploidy/aneuploidy and chromosomal translocations. This is coupled with suppression of cell cycle regulators p21^WAF1/CIP1 and 14-3-3σ, and strong induction of anti-apoptotic signalling, resulting in a reduction in the ability to eliminate genomically abnormal cells. Overexpression of GLI2ΔN also rendered human keratinocytes resistant to UVB-mediated apoptosis, whereas inhibition of B-cell lymphoma 2 (BCL-2) restored endogenous (genomic instability (GIN)) and exogenous (UVB) DNA damage-induced apoptosis. Thus, we propose that ectopic expression of GLI2 profoundly affects the genomic integrity of human epithelial cells and contributes to the survival of progenies with genomic alterations by deregulating cell cycle proteins and disabling the apoptotic mechanisms responsible for their elimination. This study reveals a novel role for GLI2 in promoting GIN, a hallmark of human tumors, and identifies potential mechanisms that may provide new opportunities for the design of novel forms of cancer therapeutic strategies.

Review of the molecular pathogenesis of osteosarcoma

Treating the osteosarcoma (OSA) remains a challenge. Current strategies focus on the primary tumor and have limited efficacy for metastatic OSA. A better understanding of the OSA pathogenesis may provide a rational basis for innovative treatment strategies especially for metastases. The aim of this review is to give an overview of the molecular mechanisms of OSA tumorigenesis, OSA cell proliferation, apoptosis, migration, and chemotherapy resistance, and how improved understanding might contribute to designing a better treatment target for OSA.

Involvement and targeted intervention of dysregulated Hedgehog signaling in osteosarcoma

BACKGROUND

During development, the Hedgehog pathway plays important roles regulating the proliferation and differentiation of chondrocytes, providing a template for growing bone. In this study, the authors investigated the components of dysregulated Hedgehog signaling as potential therapeutic targets for osteosarcoma.

METHODS

Small-molecule agonists and antagonists that modulate the Hedgehog pathway at different levels were used to investigate the mechanisms of dysregulation and the efficacy of Hedgehog blockade in osteosarcoma cell lines. The inhibitory effect of a small-molecule Smoothened (SMO) antagonist, IPI-926 (saridegib), also was examined in patient-derived xenograft models.

RESULTS

An inverse correlation was identified in osteosarcoma cell lines between endogenous glioma-associated oncogene 2 (GLI2) levels and Hedgehog pathway induction levels. Cells with high levels of GLI2 were sensitive to GLI inhibition, but not SMO inhibition, suggesting that GLI2 overexpression may be a mechanism of ligand-independent activation. In contrast, cells that expressed high levels of the Hedgehog ligand gene Indian hedgehog (IHH) and the target genes patched 1 (PTCH1) and GLI1 were sensitive to modulation of both SMO and GLI, suggesting ligand-dependent activation. In 2 xenograft models, active autocrine and paracrine, ligand-dependent Hedgehog signaling was identified. IPI-926 inhibited the Hedgehog signaling interactions between the tumor and the stroma and demonstrated antitumor efficacy in 1 of 2 ligand-dependent models.

CONCLUSIONS

The current results indicate that both ligand-dependent and ligand-independent Hedgehog dysregulation may be involved in osteosarcoma. It is the first report to demonstrate Hedgehog signaling crosstalk between the tumor and the stroma in osteosarcoma. The inhibitory effect of IPI-926 warrants additional research and raises the possibility of using Hedgehog pathway inhibitors as targeted therapeutics to improve treatment for osteosarcoma.

Hedgehog signaling induces osteosarcoma development through Yap1 and H19 overexpression

Osteosarcoma is one of the most common bone tumors. However, the genetic basis for its pathogenesis remains elusive. Here, we investigated the roles of Hedgehog (Hh) signaling in osteosarcoma development. Genetically-engineered mice with ubiquitous upregulated Hh signaling specifically in mature osteoblasts develop focal bone overgrowth, which greatly resembles the early stage of osteosarcoma. However, these mice die within three months, which prohibits further analysis of tumor progression. We therefore generated a mouse model with partial upregulated Hh signaling in mature osteoblasts and crossed it into a p53 heterozygous background to potentiate tumor development. We found that these mutant mice developed malignant osteosarcoma with high penetrance. Isolated primary tumor cells were mainly osteoblastic and highly proliferative with many characteristics of human osteosarcomas. Allograft transplantation into immunocompromised mice displayed high tumorigenic potential. More importantly, both human and mouse tumor tissues express high level of yes-associated protein 1 (Yap1), a potent oncogene that is amplified in various cancers. We show that inhibition of Hh signaling reduces Yap1 expression and knockdown of Yap1 significantly inhibits tumor progression. Moreover, long non-coding RNA H19 is aberrantly expressed and induced by upregulated Hh signaling and Yap1 overexpression. Our results demonstrate that aberrant Hh signaling in mature osteoblasts is responsible for the pathogenesis of osteoblastic osteosarcoma through Yap1 and H19 overexpression.

AEG-1 is a target of perifosine and is over-expressed in gastric dysplasia and cancers

BACKGROUND

Perifosine, an alkylphospholipid, is an Akt inhibitor which inhibits the growth of diverse cancer cells. We have reported its inhibitory effects on the growth of gastric cancer cells recently, but its molecular mechanisms are still largely unknown.

AIMS

The purpose of this study was to investigate the effect and regulatory mechanism of perifosine in gastric cancer.

METHODS

Cell viability was determined by sulforhodamine B assay after transiently transfected with AEG-1 specific siRNAs. qRT-PCR and western blot assay were used to determine the mRNA expression and proteins levels of cell signaling molecules examined. Immunohistochemistry was used to detect the AEG-1 expression in 87 gastric carcinomas, 60 dysplasia, and 47 normal gastric mucosa.

RESULTS

Perifosine decreased AEG-1 gene expression along with inhibition of Akt/GSK3β/C-MYC signaling pathway. Knockdown of AEG-1 using siRNA led to significant down-regulation of cyclin D1 expression at both mRNA level and protein level, and inhibited the growth of gastric cancer cells. AEG-1 expression was elevated in gastric dysplasia and cancer tissues compared to normal gastric mucosa (P < 0.01). AEG-1 over-expression correlated with diffuse type of gastric cancer and advanced tumor stages.

CONCLUSIONS

Perifosine inhibits the growth of gastric cancer cells possibly through inhibition of the Akt/GSK3β/C-MYC signaling pathway-mediated down-regulation of AEG-1 that subsequently down-regulated cyclin D1. AEG-1 may play an important role in the carcinogenesis and progression of gastric cancer and could be a therapeutic target of perifosine.

NVP-LDE225, a potent and selective SMOOTHENED antagonist reduces melanoma growth in vitro and in vivo

Melanoma is one of the most aggressive cancers and its incidence is increasing worldwide. So far there are no curable therapies especially after metastasis. Due to frequent mutations in members of the mitogen-activated protein kinase (MAPK) signaling pathway, this pathway is constitutively active in melanoma. It has been shown that the SONIC HEDGEHOG (SHH)-GLI and MAPK signaling pathway regulate cell growth in many tumors including melanoma and interact with each other in the regulation of cell proliferation and survival.

Here we show that the SHH-GLI pathway is active in human melanoma cell lines as they express downstream target of this pathway GLI1. Expression of GLI1 was significantly higher in human primary melanoma tissues harboring BRAF^V600E mutation than those with wild type BRAF. Pharmacologic inhibition of BRAF^V600E in human melanoma cell lines resulted in decreased expression of GLI1 thus demonstrating interaction of SHH-GLI and MAPK pathways. Inhibition of SHH-GLI pathway by the novel small molecule inhibitor of smoothened NVP-LDE225 was followed by inhibition of cell growth and induction of apoptosis in human melanoma cell lines, interestingly with both BRAF^V600E and BRAF^{Wild Type} status. NVP-LDE225 was potent in reducing cell proliferation and inducing tumor growth arrest in vitro and in vivo, respectively and these effects were superior to the natural compound cyclopamine.

Finally, we conclude that inhibition of SHH-GLI signaling pathway in human melanoma by the specific smoothened inhibitor NVP-LDE225 could have potential therapeutic application in human melanoma even in the absence of BRAF^V600E mutation and warrants further investigations.

Targeted therapies for bone sarcomas

Bone sarcomas include a very large number of tumour subtypes, which originate form bone and more particularly from mesenchymal stem cell lineage. Osteosarcoma, Ewing's sarcoma and chondrosarcoma, the three main bone sarcoma entities develop in a favourable microenvironment composed by bone cells, blood vessels, immune cells, based on the 'seed and soil theory'. Current therapy associates surgery and chemotherapy, however, bone sarcomas remain diseases with high morbidity and mortality especially in children and adolescents. In the past decade, various new therapeutic approaches emerged and target the tumour niche or/and directly the tumour cells by acting on signalling/metabolic pathways involved in cell proliferation, apoptosis or drug resistance. The present review gives a brief overview from basic to clinical assessment of the main targeted therapies of bone sarcoma cells.

Arsenic trioxide prevents osteosarcoma growth by inhibition of GLI transcription via DNA damage accumulation

The Hedgehog pathway is activated in various types of malignancies. We previously reported that inhibition of SMO or GLI prevents osteosarcoma growth in vitro and in vivo. Recently, it has been reported that arsenic trioxide (ATO) inhibits cancer growth by blocking GLI transcription. In this study, we analyzed the function of ATO in the pathogenesis of osteosarcoma. Real-time PCR showed that ATO decreased the expression of Hedgehog target genes, including PTCH1, GLI1, and GLI2, in human osteosarcoma cell lines. WST-1 assay and colony formation assay revealed that ATO prevented osteosarcoma growth. These findings show that ATO prevents GLI transcription and osteosarcoma growth in vitro. Flow cytometric analysis showed that ATO promoted apoptotic cell death. Comet assay showed that ATO treatment increased accumulation of DNA damage. Western blot analysis showed that ATO treatment increased the expression of γH2AX, cleaved PARP, and cleaved caspase-3. In addition, ATO treatment decreased the expression of Bcl-2 and Bcl-xL. These findings suggest that ATO treatment promoted apoptotic cell death caused by accumulation of DNA damage. In contrast, Sonic Hedgehog treatment decreased the expression of γH2AX induced by cisplatin treatment. ATO re-induced the accumulation of DNA damage attenuated by Sonic Hedgehog treatment. These findings suggest that ATO inhibits the activation of Hedgehog signaling and promotes apoptotic cell death in osteosarcoma cells by accumulation of DNA damage. Finally, examination of mouse xenograft models showed that ATO administration prevented the growth of osteosarcoma in nude mice. Because ATO is an FDA-approved drug for treatment of leukemia, our findings suggest that ATO is a new therapeutic option for treatment of patients with osteosarcoma.

Expression of smoothened protein in colon cancer and its prognostic value for postoperative liver metastasis

BACKGROUDS: The hedgehog (Hh) signaling pathway is composed of patched (PTCH) and smoothened (SMO), two transmembrane proteins, and downstream glioma-associated oncogene homolog (Gli) transcription factors. Hh signaling plays a pathological role in the occurrence and development of various cancers.

METHODS

To investigate the expression of SMO protein in colon cancer and its association with clinicopathological parameters and postoperative liver metastasis, immunohistochemistry was performed with paraffin-embedded specimens of 96 cases. Relationships between SMO protein expression and clinicopathological parameters, postoperative liver metastasis were analyzed.

RESULTS

IHC examination showed that SMO protein expression was significantly increased in colon cancer tissues compared to normal colon tissues (P = 0.042), positively related to lymph node metastases (P = 0.018) and higher T stages (P = 0.026). Postoperative live metastasis-free survival was significantly longer in the low SMO expression group than in those with high SMO expression (48.7 ± 8.02 months vs 28.0 ± 6.86 months, P=0.036). Multivariate analysis showed SMO expression level to be an independent prognostic factor for postoperative live metastasis-free survival (95% confidence interval [CI] =1.46-2.82, P = 0.008).

CONCLUSIONS

Our results suggest that in patients with colon cancer, the SMO expression level is an independent biomarker for postoperative liver metastasis, and SMO might play an important role in colon cancer progression.

Time-lapse imaging of neuroblastoma cells to determine cell fate upon gene knockdown

Neuroblastoma is the most common extra-cranial solid tumor of early childhood. Standard therapies are not effective in case of poor prognosis and chemotherapy resistance. To improve drug therapy, it is imperative to discover new targets that play a substantial role in tumorigenesis of neuroblastoma. The mitotic machinery is an attractive target for therapeutic interventions and inhibitors can be developed to target mitotic entry, spindle apparatus, spindle activation checkpoint, and mitotic exit. We present an elaborate analysis pipeline to determine cancer specific therapeutic targets by first performing a focused gene expression analysis to select genes followed by a gene knockdown screening assay of live cells. We interrogated gene expression studies of neuroblastoma tumors and selected 240 genes relevant for tumorigenesis and cell cycle. With these genes we performed time-lapse screening of gene knockdowns in neuroblastoma cells. We classified cellular phenotypes and used the temporal context of the perturbation effect to determine the sequence of events, particularly the mitotic entry preceding cell death. Based upon this phenotype kinetics from the gene knockdown screening, we inferred dynamic gene functions in mitosis and cell proliferation. We identified six genes (DLGAP5, DSCC1, SMO, SNRPD1, SSBP1, and UBE2C) with a vital role in mitosis and these are promising therapeutic targets for neuroblastoma. Images and movies of every time point of all screened genes are available at https://ichip.bioquant.uni-heidelberg.de.

Bone sarcomas: from biology to targeted therapies

Primary malignant bone tumours, osteosarcomas, and Ewing sarcomas are rare diseases which occur mainly in adolescents and young adults. With the current therapies, some patients remain very difficult to treat, such as tumour with poor histological response to preoperative CT (or large initial tumour volume for Ewing sarcomas not operated), patients with multiple metastases at or those who relapsed. In order to develop new therapies against these rare tumours, we need to unveil the key driving factors and molecular abnormalities behind the malignant characteristics and to broaden our understanding of the phenomena sustaining the metastatic phenotype and treatment resistance in these tumours. In this paper, starting with the biology of these tumours, we will discuss potential therapeutic targets aimed at increasing local tumour control, limiting metastatic spread, and finally improving patient survival.

Prevailing importance of the hedgehog signaling pathway and the potential for treatment advancement in sarcoma

The hedgehog signaling pathway is important in embryogenesis and post natal development. Constitutive activation of the pathway due to mutation of pathway components occurs in ~25% of medulloblastomas and also in basal cell carcinomas. In many other malignancies the therapeutic role for hedgehog inhibition though intriguing, based on preclinical data, is far from assured. Hedgehog inhibition is not an established part of the treatment paradigm of sarcoma but the scientific rationale for a possible benefit is compelling. In chondrosarcoma there is evidence of hedgehog pathway activation and an ontologic comparison between growth plate chondrocyte differentiation and different chondrosarcoma subtypes. Immunostaining epiphyseal growth plate for Indian hedgehog is particularly positive in the zone of pre-hypertrophic chondrocytes which correlates ontologically with conventional chondrosarcoma. In Ewing sarcoma/PNET tumors the Gli1 transcription factor is a direct target of the EWS-FLI1 oncoprotein present in 85% of cases. In many cases of rhabdomyosarcomas there is increased expression of Gli1 (Ragazzini et al., 2004). Additionally, a third of embryonal rhabdomyosarcomas have loss of Chr.9q22 that encompasses the patched locus (Bridge et al., 2000). The potential to treat osteosarcoma by inhibition of Gli2 and the role of the pathway in ovarian fibromas and other connective tissue tumors is also discussed (Nagao et al., 2011; Hirotsu et al., 2010). Emergence of acquired secondary resistance to targeted therapeutics is an important issue that is also relevant to hedgehog inhibition. In this context secondary resistance of medulloblastomas to treatment with a smoothened antagonist in two tumor mouse models is examined.

The activities of Smad and Gli mediated signalling pathways in high-grade conventional osteosarcoma

High-grade conventional osteosarcoma is a malignant tumour predominantly affecting adolescents and, despite multimodal intensive therapy, lethal for one third of the patients. Although there is currently detailed knowledge of normal skeletal development, this has not been integrated into research on the genesis of osteosarcoma. Recently we showed that the canonical Wnt pathway is not active in osteosarcoma and that its reactivation is disadvantageous to osteosarcoma cells. Since Wnt is regulating normal skeletogenesis together with other pathways, here we report on the activities of the bone morphogenic protein (BMP), the transforming growth factor beta (TGFβ) and the hedgehog (Hh) pathways in osteosarcoma. Human osteosarcoma samples (n=210), benign bone tumours of osteoblastic lineage called osteoblastoma (n=25) and osteosarcoma cell lines (n=19) were examined. For pathway activity luciferase transcriptional reporter assays and gene and protein expression analyses were performed. Immunohistochemical analysis of phosphorylated Smad1 and Smad2, the intracellular effectors of BMP and TGFβ, respectively, showed nuclear expression of both proteins in 70% of the osteosarcoma samples at levels comparable to osteoblastoma. Interestingly cases with lower expression showed significantly worse disease free survival. This may imply that drugs restoring impaired signalling pathways in osteosarcoma might change the tumour's aggressive clinical course, however targeted pathway modulation in vitro did not affect cell proliferation.

The utility of hedgehog signaling pathway inhibition for cancer

The Hedgehog (Hh) signaling pathway has been implicated in tumor initiation and metastasis across different malignancies. Major mechanisms by which the Hh pathway is aberrantly activated can be attributed to mutations of members of Hh pathway or excessive/inappropriate expression of Hh pathway ligands. The Hh signaling pathway also affects the regulation of cancer stem cells, leading to their capabilities in tumor formation, disease progression, and metastasis. Preliminary results of early phase clinical trials of Hh inhibitors administered as monotherapy demonstrated promising results in patients with basal cell carcinoma and medulloblastoma, but clinically meaningful anticancer efficacy across other tumor types seems to be lacking. Additionally, cases of resistance have been already observed. Mutations of SMO, activation of Hh pathway components downstream to SMO, and upregulation of alternative signaling pathways are possible mechanisms of resistance development. Determination of effective Hh inhibitor-based combination regimens and development of correlative biomarkers relevant to this pathway should remain as clear priorities for future research.

Role of hedgehog signaling in malignant pleural mesothelioma

PURPOSE

The aim of this study was to assess the activity of hedgehog signaling pathway in malignant pleural mesothelioma (MPM).

EXPERIMENTAL DESIGN

The expression of hedgehog signaling components was assessed by quantitative PCR and in situ hybridization in 45 clinical samples. Primary MPM cultures were developed in serum-free condition in 3% oxygen and were used to investigate the effects of smoothened (SMO) inhibitors or GLI1 silencing on cell growth and hedgehog signaling. In vivo effects of SMO antagonists were determined in an MPM xenograft growing in nude mice.

RESULTS

A significant increase in GLI1, sonic hedgehog, and human hedgehog interacting protein gene expression was observed in MPM tumors compared with nontumoral pleural tissue. SMO antagonists inhibited GLI1 expression and cell growth in sensitive primary cultures. This effect was mimicked by GLI1 silencing. Reduced survivin and YAP protein levels were also observed. Survivin protein levels were rescued by overexpression of GLI1 or constitutively active YAP1. Treatment of tumor-bearing mice with the SMO inhibitor HhAntag led to a significant inhibition of tumor growth in vivo accompanied by decreased Ki-67 and nuclear YAP immunostaining and a significant difference in selected gene expression profile in tumors.

CONCLUSIONS

An aberrant hedgehog signaling is present in MPM, and inhibition of hedgehog signaling decreases tumor growth indicating potential new therapeutic approach.

Accumulation of p62 in degenerated spinal cord under chronic mechanical compression: functional analysis of p62 and autophagy in hypoxic neuronal cells

Intracellular accumulation of altered proteins, including p62 and ubiquitinated proteins, is the basis of most neurodegenerative disorders. The relationship among the accumulation of altered proteins, autophagy, and spinal cord dysfunction by cervical spondylotic myelopathy has not been clarified. We examined the expression of p62 and autophagy markers in the chronically compressed spinal cord of tiptoe-walking Yoshimura mice. In addition, we examined the expression and roles of p62 and autophagy in hypoxic neuronal cells. Western blot analysis showed the accumulation of p62, ubiquitinated proteins, and microtubule-associated protein 1 light chain 3 (LC3), an autophagic marker, in the compressed spinal cord. Immunohistochemical examinations showed that p62 accumulated in neurons, axons, astrocytes, and oligodendrocytes. Electron microscopy showed the expression of autophagy markers, including autolysosomes and autophagic vesicles, in the compressed spinal cord. These findings suggest the presence of p62 and autophagy in the degenerated compressed spinal cord. Hypoxic stress increased the expression of p62, ubiquitinated proteins, and LC3-II in neuronal cells. In addition, LC3 turnover assay and GFP-LC3 cleavage assay showed that hypoxic stress increased autophagy flux in neuronal cells. These findings suggest that hypoxic stress induces accumulation of p62 and autophagy in neuronal cells. The forced expression of p62 decreased the number of neuronal cells under hypoxic stress. These findings suggest that p62 accumulation under hypoxic stress promotes neuronal cell death. Treatment with 3-methyladenine, an autophagy inhibitor decreased the number of neuronal cells, whereas lithium chloride, an autophagy inducer increased the number of cells under hypoxic stress. These findings suggest that autophagy promotes neuronal cell survival under hypoxic stress. Our findings suggest that pharmacological inducers of autophagy may be useful for treating cervical spondylotic myelopathy patients.

Targeted therapies in sarcomas: challenging the challenge

Sarcomas are a heterogeneous group of mesenchymal malignancies that very often lead to death. Nowadays, chemotherapy is the only available treatment for most sarcomas but there are few active drugs and clinical results still remain very poor. Thus, there is an imperious need to find new therapeutic alternatives in order to improve sarcoma patient's outcome. During the last years, there have been described a number of new molecular pathways that have allowed us to know more about cancer biology and tumorigenesis. Sarcomas are one of the tumors in which more advances have been made. Identification of specific chromosomal translocations, some important pathways characterization such as mTOR pathway or the insulin-like growth factor pathway, the stunning development in angiogenesis knowledge, and brand new agents like viruses have lead to the development of new therapeutic options with promising results. This paper makes an exhaustive review of preclinical and clinical evidence of the most recent targeted therapies in sarcomas and provides a future view of treatments that may lead to improve prognosis of patients affected with this disease.

Hedgehog inhibitor decreases chemosensitivity to 5-fluorouracil and gemcitabine under hypoxic conditions in pancreatic cancer

Pancreatic cancer is one of the deadliest types of cancer. Previously, we showed that hypoxia increases invasiveness through upregulation of Smoothened (Smo) transcription in pancreatic ductal adenocarcinoma (PDAC) cells. Here, we first evaluated whether hypoxia-induced increase in Smo contributes to the proliferation of PDAC cells. We showed that Smo, but not Gli1, inhibition decreases proliferation significantly under hypoxic conditions. To further investigate the effects of Smo on PDAC growth, cell cycle analysis was carried out. Inhibition of Smo under hypoxia led to G(0) /G(1) arrest and decreased S phase. As 5-fluorouracil (5-FU) and gemcitabine, which are first-line drugs for pancreatic cancer, are sensitive to S phase, we then evaluated whether cyclopamine-induced decreased S phase under hypoxia affected the chemosensitivity of 5-FU and gemcitabine in PDAC cells. Cyclopamine treatment under hypoxia significantly decreased chemosensitivity to 5-FU and gemcitabine under hypoxia in both in vitro and in vivo models. In contrast, cis-diamminedichloroplatinum, which is cell cycle-independent, showed significant synergistic effects. These results suggest that hypoxia-induced increase of Smo directly contributes to the proliferation of PDAC cells through a hedgehog/Gli1-independent pathway, and that decreased S phase due to the use of Smo inhibitor under hypoxia leads to chemoresistance in S phase-sensitive anticancer drugs. Our results could be very important clinically because a clinical trial using Smo inhibitors and chemotherapy drugs will begin in the near future.

Pathways involved in Drosophila and human cancer development: the Notch, Hedgehog, Wingless, Runt, and Trithorax pathway

Animal models are established tools to study basic questions of biology in a systematic way. They have greatly facilitated our understanding of the mechanisms by which nature forms and maintains organisms. Much of the knowledge on molecular changes underlying the development of organisms originates from research in the fruit fly model Drosophila melanogaster. Vertebrate models including the mouse and zebrafish model, but also other animal models coming from different corners of the animal kingdom have shown that much of the basic machinery of development is essentially identical, not just in all vertebrates but in all major phyla of invertebrates too. Moreover, key elements of this machinery have been demonstrated to be involved in recurrent molecular abnormalities detected in tumor-tissue from patients, indicating their implication in the genesis of human cancer. Thus, research in this field has become a common topic for both biologists and hemato-oncologists. In this review, we summarize current knowledge on some of these key elements and molecular pathways such as Notch, Hedgehog, Wingless, Runt, and Trithorax that have been originally described and studied in animal models and which seem to play a major role in the pathophysiology and targeted management of human cancer.

Therapeutic pipeline for soft-tissue sarcoma

INTRODUCTION

Soft-tissue sarcomas (STS) represent a heterogeneous group of malignant tumors originating from connective tissues. Over recent years, this heterogeneity has led to a molecular breakdown of STS and subsequent use of targeted agents in several molecularly defined subgroups. After the initial success of imatinib in gastrointestinal stromal tumors, several other compounds have shown promising activity in some but not all subgroups of sarcoma.

AREAS COVERED

This review discusses the rational and clinical results, when available, that support this subtype-directed approach. In the vast majority of cases, these agents have been tested only in patients with advanced disease; as chemotherapeutic agents are developed as non-histotype-specific therapies, they are not discussed here. The PubMed literature was searched using the terms 'sarcoma', 'angiogenesis', 'mTOR' and 'targeted agents'. Proceedings of the annual meeting of the American Society of Clinical Oncology as well as those of the Connective Tissue Oncology Society were also searched for relevant information.

EXPERT OPINION

Many agents are currently developed in a subtype-specific manner in STS and this represents a significant leap forward. However, much remains to be done to improve our understanding of the molecular biology of this heterogeneous group of diseases.

Expression of Sonic hedgehog during cell proliferation in the human cerebellum

The regulation of cell proliferation in the external granular layer (EGL) of the developing cerebellum is important for its normal patterning. An important signal that regulates EGL cell proliferation is Sonic hedgehog (Shh). Shh is secreted by the Purkinje cells (PC) and has a mitogenic effect on the granule cell precursors of the EGL. Deregulation of Shh signaling has been associated with abnormal development, and been implicated in medulloblastomas, which are tumors that arise from the cerebellum. Given the importance of the Shh pathway in cerebellum development and disease, there has been no systematic study of its expression pattern during human cerebellum development. In this study, we describe the expression pattern of Shh, its receptor patched, smoothened, and its effectors that belong to the Gli family of transcription factors, during normal human cerebellum development from 10 weeks of gestational age, and in medulloblastomas that represents a case of abnormal cell proliferation in the cerebellum. This expression pattern is compared to equivalent stages in the normal development of cerebellum in mouse, as well as in tumors. Important differences between human and mouse that reflect differences in the normal developmental program between the 2 species are observed. First, in humans there appears to be a stage of Shh signaling within the EGL, when the PC are not yet the source of Shh. Second, unlike in the postnatal mouse cerebellum, expression of Shh in the PC in the postnatal human cerebellum is downregulated. Finally, medulloblastomas in the human but not in patched heterozygote mouse express Shh. These results highlight cross-species differences in the regulation of the Shh signaling pathway.

HH/GLI signalling as a new therapeutic target for patients with oral squamous cell carcinoma

Aberrant activation of HH/GLI has recently been reported in multiple cancer types, yet its role in oral squamous cell carcinoma (OSCC) has not been investigated. In this study, we aimed to determine the role of HH/GLI in OSCC. Expression of GLI1 and GLI2 was examined in OSCC samples from 136 patients by immunohistochemistry and correlated with clinicopathology parameters and clinical outcomes of the patients. Two HH/GLI specific small molecule inhibitors cyclopamine and GANT61, were used to test the potential role of HH/GLI in OSCC. We found that GLI2, one of the main transcriptional activators of HH/GLI signalling, was expressed in 60 (44%) of the 136 OSCC samples and the expression was significantly associated with poor clinical outcomes. Only 44% of the patients whose tumours expressed GLI2 survived at 5years after surgery compared to 77% of those whose tumours lacked the GLI2 expression (P<0.0001). Both cyclopamine and GANT61 effectively inhibited GLI expression, slowed cell growth, promoted G1 arrest, increased apoptosis and inhibited migration of OSCC cells. Our results demonstrate that activation of HH/GLI pathway plays an important role in OSCC progression. Together with the finding that expression of GLI2 is strongly associated with a poor clinic outcome of OSCC patients, the data suggest that a subset of OSCC patients may benefit from anti-HH/GLI therapies.

Suppression of osteosarcoma cell invasion by chemotherapy is mediated by urokinase plasminogen activator activity via up-regulation of EGR1

BACKGROUND

The cellular and molecular mechanisms of tumour response following chemotherapy are largely unknown. We found that low dose anti-tumour agents up-regulate early growth response 1 (EGR1) expression. EGR1 is a member of the immediate-early gene group of transcription factors which modulate transcription of multiple genes involved in cell proliferation, differentiation, and development. It has been reported that EGR1 act as either tumour promoting factor or suppressor. We therefore examined the expression and function of EGR1 in osteosarcoma.

METHODS

We investigated the expression of EGR1 in human osteosarcoma cell lines and biopsy specimens. We next examined the expression of EGR1 following anti-tumour agents treatment. To examine the function of EGR1 in osteosarcoma, we assessed the tumour growth and invasion in vitro and in vivo.

RESULTS

Real-time PCR revealed that EGR1 was down-regulated both in osteosarcoma cell lines and osteosarcoma patients' biopsy specimens. In addition, EGR1 was up-regulated both in osteosarcoma patient' specimens and osteosarcoma cell lines following anti-tumour agent treatment. Although forced expression of EGR1 did not prevent osteosarcoma growth, forced expression of EGR1 prevented osteosarcoma cell invasion in vitro. In addition, forced expression of EGR1 promoted down-regulation of urokinase plasminogen activator, urokinase receptor, and urokinase plasminogen activity. Xenograft mice models showed that forced expression of EGR1 prevents osteosarcoma cell migration into blood vessels.

CONCLUSIONS

These findings suggest that although chemotherapy could not prevent osteosarcoma growth in chemotherapy-resistant patients, it did prevent osteosarcoma cell invasion by down-regulation of urokinase plasminogen activity via up-regulation of EGR1 during chemotherapy periods.