Inhibition of AP-1 transcriptional activity blocks the migration, invasion, and experimental metastasis of murine osteosarcoma

Surgical Tumor Resection Deregulates Hallmarks of Cancer in Resected Tissue and the Surrounding Microenvironment

Surgery exposes tumor tissue to severe hypoxia and mechanical stress leading to rapid gene expression changes in the tumor and its microenvironment, which remain poorly characterized. We biopsied tumor and adjacent normal tissues from patients with breast (n = 81) and head/neck squamous cancers (HNSC; n = 10) at the beginning (A), during (B), and end of surgery (C). Tumor/normal RNA from 46/81 patients with breast cancer was subjected to mRNA-Seq using Illumina short-read technology, and from nine patients with HNSC to whole-transcriptome microarray with Illumina BeadArray. Pathways and genes involved in 7 of 10 known cancer hallmarks, namely, tumor-promoting inflammation (TNF-A, NFK-B, IL18 pathways), activation of invasion and migration (various extracellular matrix-related pathways, cell migration), sustained proliferative signaling (K-Ras Signaling), evasion of growth suppressors (P53 signaling, regulation of cell death), deregulating cellular energetics (response to lipid, secreted factors, and adipogenesis), inducing angiogenesis (hypoxia signaling, myogenesis), and avoiding immune destruction (CTLA4 and PDL1) were significantly deregulated during surgical resection (time points A vs. B vs. C). These findings were validated using NanoString assays in independent pre/intra/post-operative breast cancer samples from 48 patients. In a comparison of gene expression data from biopsy (analogous to time point A) with surgical resection samples (analogous to time point C) from The Cancer Genome Atlas study, the top deregulated genes were the same as identified in our analysis, in five of the seven studied cancer types. This study suggests that surgical extirpation deregulates the hallmarks of cancer in primary tumors and adjacent normal tissue across different cancers.

IMPLICATIONS

Surgery deregulates hallmarks of cancer in human tissue.

Temporal chromatin accessibility changes define transcriptional states essential for osteosarcoma metastasis

The metastasis-invasion cascade describes the series of steps required for a cancer cell to successfully spread from its primary tumor and ultimately grow within a secondary organ. Despite metastasis being a dynamic, multistep process, most omics studies to date have focused on comparing primary tumors to the metastatic deposits that define end-stage disease. This static approach means we lack information about the genomic and epigenomic changes that occur during the majority of tumor progression. One particularly understudied phase of tumor progression is metastatic colonization, during which cells must adapt to the new microenvironment of the secondary organ. Through temporal profiling of chromatin accessibility and gene expression in vivo, we identify dynamic changes in the epigenome that occur as osteosarcoma tumors form and grow within the lung microenvironment. Furthermore, we show through paired in vivo and in vitro CRISPR drop-out screens and pharmacological validation that the upstream transcription factors represent a class of metastasis-specific dependency genes. While current models depict lung colonization as a discrete step within the metastatic cascade, our study shows it is a defined trajectory through multiple epigenetic states, revealing new therapeutic opportunities undetectable with standard approaches.

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Osteosarcoma and Metastasis

Osteosarcoma is the most common primary bone malignancy in adolescents. Its high propensity to metastasize is the leading cause for treatment failure and poor prognosis. Although the research of osteosarcoma has greatly expanded in the past decades, the knowledge and new therapy strategies targeting metastatic progression remain sparse. The prognosis of patients with metastasis is still unsatisfactory. There is resonating urgency for a thorough and deeper understanding of molecular mechanisms underlying osteosarcoma to develop innovative therapies targeting metastasis. Toward the goal of elaborating the characteristics and biological behavior of metastatic osteosarcoma, it is essential to combine the diverse investigations that are performed at molecular, cellular, and animal levels from basic research to clinical translation spanning chemical, physical sciences, and biology. This review focuses on the metastatic process, regulatory networks involving key molecules and signaling pathways, the role of microenvironment, osteoclast, angiogenesis, metabolism, immunity, and noncoding RNAs in osteosarcoma metastasis. The aim of this review is to provide an overview of current research advances, with the hope to discovery druggable targets and promising therapy strategies for osteosarcoma metastasis and thus to overcome this clinical impasse.

Deciphering genes associated with diffuse large B-cell lymphoma with lymphomatous effusions: A mutational accumulation scoring approach

Introduction

Earlier studies have shown that lymphomatous effusions in patients with diffuse large B-cell lymphoma (DLBCL) are associated with a very poor prognosis, even worse than for non-effusion-associated patients with stage IV disease. We hypothesized that certain genetic abnormalities were associated with lymphomatous effusions, which would help to identify related pathways, oncogenic mechanisms, and therapeutic targets.

Methods

We compared whole-exome sequencing on DLBCL samples involving solid organs (n = 22) and involving effusions (n = 9). We designed a mutational accumulation-based approach to score each gene and used mutation interpreters to identify candidate pathogenic genes associated with lymphomatous effusions. Moreover, we performed gene-set enrichment analysis from a microarray comparison of effusion-associated versus non-effusion-associated DLBCL cases to extract the related pathways.

Results

We found that genes involved in identified pathways or with high accumulation scores in the effusion-based DLBCL cases were associated with migration/invasion. We validated expression of 8 selected genes in DLBCL cell lines and clinical samples: MUC4, SLC35G6, TP53BP2, ARAP3, IL13RA1, PDIA4, HDAC1 and MDM2, and validated expression of 3 proteins (MUC4, HDAC1 and MDM2) in an independent cohort of DLBCL cases with (n = 31) and without (n = 20) lymphomatous effusions. We found that overexpression of HDAC1 and MDM2 correlated with the presence of lymphomatous effusions, and HDAC1 overexpression was associated with the poorest prognosis. 

Conclusion

Our findings suggest that DLBCL associated with lymphomatous effusions may be associated mechanistically with TP53-MDM2 pathway and HDAC-related chromatin remodeling mechanisms.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40364-021-00330-8.

Transcription activation depends on the length of the RNA polymerase II C-terminal domain

Eukaryotic RNA polymerase II (Pol II) contains a tail‐like, intrinsically disordered carboxy‐terminal domain (CTD) comprised of heptad‐repeats, that functions in coordination of the transcription cycle and in coupling transcription to co‐transcriptional processes. The CTD repeat number varies between species and generally increases with genome size, but the reasons for this are unclear. Here, we show that shortening the CTD in human cells to half of its length does not generally change pre‐mRNA synthesis or processing in cells. However, CTD shortening decreases the duration of promoter‐proximal Pol II pausing, alters transcription of putative enhancer elements, and delays transcription activation after stimulation of the MAP kinase pathway. We suggest that a long CTD is required for efficient enhancer‐dependent recruitment of Pol II to target genes for their rapid activation.

MUC 15 Promotes Osteosarcoma Cell Proliferation, Migration and Invasion through Livin, MMP-2/MMP-9 and Wnt/β-Catenin Signal Pathway

Objective: To investigate the high expression of MUC15 in promoting proliferation, migration and invasion in osteosarcoma (OS) cell and its potential mechanism.

Methods: The expressions of MUC15 in OS patients were analyzed from GEO Datasets, tumor cell lines and clinical samples. The roles of MUC15 in OS were explored by CCK-8, flow cytometry, transwell and western blot assay, respectively.

Results: MUC15 was highly expressed in osteosarcoma, and there was a significant negative correlation between MUC15 and the prognosis. Knockdown of MUC15 in HOS and U-2OS could promote tumor cell apoptosis, down-regulate the expression of MMP2/9, reduce the epithelial interstitial transition and silence the Wnt/b-Catenin signal pathway.

Conclusion: The high-expression of MUC15 promotes the proliferation, migration and invasion of osteosarcoma through anti-apoptosis, increasing the invasive ability by epithelial interstitial transition, and activating the Wnt/b-Catenin signal pathway.

Role of c-Fos in orthodontic tooth movement: an in vivo study using transgenic mice

Objectives

The transcription factor c-Fos controls the differentiation of osteoclasts and is expressed in periodontal ligament cells after mechanical stimulation in vitro. However, it is unclear how c-Fos regulates orthodontic tooth movement (OTM) in vivo. The aim of this study was therefore to analyse OTM in transgenic mice with overexpression of c-Fos.

Materials and methods

We employed c-Fos transgenic mice (c-Fos tg) and wild-type littermates (WT) in a model of OTM induced by Nitinol tension springs that were bonded between the left first maxillary molars and the upper incisors. The unstimulated contralateral side served as an internal control. Mice were analysed by contact radiography, micro-computed tomography, decalcified histology and histochemistry.

Results

Our analysis of the unstimulated side revealed that alveolar bone and root morphology were similar between c-Fos tg and control mice. However, we observed more osteoclasts in the alveolar bone of c-Fos tg mice as tartrate-resistant acid phosphatase (TRAP)-positive cells were increased by 40%. After 12 days of OTM, c-Fos tg mice exhibited 62% increased tooth movement as compared with WT mice. Despite the faster tooth movement, c-Fos tg and WT mice displayed the same amount of root resorption. Importantly, we did not observe orthodontically induced tissue necrosis (i.e. hyalinization) in c-Fos tg mice, while this was a common finding in WT mice.

Conclusion

Overexpression of c-Fos accelerates tooth movement without causing more root resorption.

Clinical relevance

Accelerated tooth movement must not result in more root resorption as higher tissue turnover may decrease the amount of mechanically induced tissue necrosis.

Electronic supplementary material

The online version of this article (10.1007/s00784-020-03503-1) contains supplementary material, which is available to authorized users.

Positively selected enhancer elements endow osteosarcoma cells with metastatic competence

Metastasis results from a complex set of traits acquired by tumor cells, distinct from those necessary for tumorigenesis. Here, we investigate the contribution of enhancer elements to the metastatic phenotype of osteosarcoma. Through epigenomic profiling, we identify substantial differences in enhancer activity between primary and metastatic human tumors and between near isogenic pairs of highly lung metastatic and nonmetastatic osteosarcoma cell lines. We term these regions metastatic variant enhancer loci (Met-VELs). Met-VELs drive coordinated waves of gene expression during metastatic colonization of the lung. Met-VELs cluster nonrandomly in the genome, indicating that activity of these enhancers and expression of their associated gene targets are positively selected. As evidence of this causal association, osteosarcoma lung metastasis is inhibited by global interruptions of Met-VEL-associated gene expression via pharmacologic BET inhibition, by knockdown of AP-1 transcription factors that occupy Met-VELs, and by knockdown or functional inhibition of individual genes activated by Met-VELs, such as that encoding coagulation factor III/tissue factor (F3). We further show that genetic deletion of a single Met-VEL at the F3 locus blocks metastatic cell outgrowth in the lung. These findings indicate that Met-VELs and the genes they regulate play a functional role in metastasis and may be suitable targets for antimetastatic therapies.

37LRP induces invasion in hypoxic lung adenocarcinoma cancer cells A549 through the JNK/ERK/c-Jun signaling cascade

We previously reported that 37-kDa laminin receptor precursor involved in metastasis of lung adenocarcinoma cancer cells. In this study, we further revealed that hypoxia induced 37-kDa laminin receptor precursor expression and activation of extracellular signal-regulated protein kinase, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase in lung adenocarcinoma cancer cells. In addition, we further demonstrated that the c-Jun N-terminal kinase inhibitor SP600125 and extracellular signal-regulated protein kinase inhibitor U0126 blocked the c-Jun activity and abolished hypoxia-induced 37-kDa laminin receptor precursor expression and promoter activity in a concentration-dependent manner. However, the p38 mitogen-activated protein kinase inhibitor did not affect 37-kDa laminin receptor precursor expression and c-Jun activity in response to hypoxia. Furthermore, downregulated c-Jun expression by short interfering RNA could also inhibit hypoxia-induced 37-kDa laminin receptor precursor expression and transcriptional activity. The inhibition of 37-kDa laminin receptor precursor expression by SP600125 and U0126 could be rescued by c-Jun overexpression. Studies using luciferase promoter constructs revealed a significant increase in the activity of promoter binding in the cells exposed to hypoxia, which was lost in the cells with mutation of the activator protein 1 binding site. Electrophoresis mobility shift assay and chromatin immunoprecipitation demonstrated a functional activator protein 1 binding site within 37-kDa laminin receptor precursor gene regulatory sequence located at -271 relative to the transcriptional initiation point. Hypoxia-induced invasion of A549 cells was inhibited by the pharmacologic inhibitors of c-Jun N-terminal kinase (SP600125) and extracellular signal-regulated protein kinase (U0126) as well as 37-kDa laminin receptor precursor-specific siRNA or antibody. Our results suggest that hypoxia-elicited c-Jun/activator protein 1 regulates 37-kDa laminin receptor precursor expression, which modulates migration and invasion of lung adenocarcinoma cells.

Deciphering signaling networks in osteosarcoma pathobiology

Osteosarcoma is the most frequent type of primary bone tumors among children and adolescents. During the past years, little progress has been made regarding prognosis of osteosarcoma patients, especially for those with metastatic disease. Genomic instability and gene alterations are common, but current data do not reveal a consistent and repeatable pattern of osteosarcoma development, thus paralleling the tumor's high heterogeneity. Critical signal transduction pathways have been implicated in osteosarcoma pathobiology and are being evaluated as therapeutic targets, including receptor activator for nuclear factor-κB (RANK), Wnt, Notch, phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin, and mechanotransduction pathways. Herein, we recapitulate and discuss recent advances in the context of molecular mechanisms and signaling networks that contribute to osteosarcoma progression and metastasis, towards patient-tailored and novel-targeted treatments.

Genetic factors conferring metastasis in osteosarcoma

Osteosarcoma (OS) is a deadly bone malignancy affecting mostly children and adolescents. OS has outstandingly complex genetic alterations likely due to p53-independent genomic instability. Based on analysis of recent published research we claim existence of various genetic mechanisms of osteosarcomagenesis conferring great variability to different OS properties including metastatic potential. We also propose a model explaining how diverse genetic mechanisms occur and providing a framework for future research. P53-independent preexisting genomic instability, which precedes and frequently causes TP53 genetic alterations, is central in our model. In addition, our analyses reveal a possible cooperation between aberrantly activated HIF-1α and AP-1 genetic pathways in OS metastasis. We also review the involvement of noncoding RNA genes in OS metastasis.

Significance of MTA1 in the molecular characterization of osteosarcoma

Osteosarcoma is the most common malignant bone tumor in children and characterized by aggressive biologic behavior of metastatic propensity to the lung. Change of treatment paradigm brings survival benefit; however, 5-year survival rate is still low in patients having metastastatic foci at diagnosis for a few decades. Metastasis-associated protein (MTA) family is a group of ubiquitously expressed coregulators, which influences on tumor invasiveness or metastasis. MTA1 has been investigated in various cancers including osteosarcoma, and its overexpression is associated with high-risk features of cancers. In this review, we described various molecular studies of osteosarcoma, especially associated with MTA1.

IL-1β-specific recruitment of GCN5 histone acetyltransferase induces the release of PAF1 from chromatin for the de-repression of inflammatory response genes

To determine the functional specificity of inflammation, it is critical to orchestrate the timely activation and repression of inflammatory responses. Here, we explored the PAF1 (RNA polymerase II associated factor)-mediated signal- and locus-specific repression of genes induced through the pro-inflammatory cytokine interleukin (IL)-1β. Using microarray analysis, we identified the PAF1 target genes whose expression was further enhanced by PAF1 knockdown in IL-1β–stimulated HepG2 hepatocarcinomas. PAF1 bound near the transcription start sites of target genes and dissociated on stimulation. In PAF1-deficient cells, more elongating RNA polymerase II and acetylated histones were observed, although IL-1β–mediated activation and recruitment of nuclear factor κB (NF-κB) were not altered. Under basal conditions, PAF1 blocked histone acetyltransferase general control non-depressible 5 (GCN5)-mediated acetylation on H3K9 and H4K5 residues. On IL-1β stimulation, activated GCN5 discharged PAF1 from chromatin, allowing productive transcription to occur. PAF1 bound to histones but not to acetylated histones, and the chromatin-binding domain of PAF1 was essential for target gene repression. Moreover, IL-1β–induced cell migration was similarly controlled through counteraction between PAF1 and GCN5. These results suggest that the IL-1β signal-specific exchange of PAF1 and GCN5 on the target locus limits inappropriate gene induction and facilitates the timely activation of inflammatory responses.

Activator protein-1 inhibition by 3-[(dodecylthiocarbonyl)methyl]-glutamaride impairs invasion and radiosensitizes osteosarcoma cells in vitro

Osteosarcoma (OS) is the most common primary malignant bone tumor. Despite advances in neoadjuvant multi-agent chemotherapy, the outcome of patients has not significantly improved in the last decades, making the search for more effective therapeutic agents imperative. In the present study, we explored the possibility of using activator protein-1 inhibition by 3-[(dodecylthiocarbonyl)methyl]-glutarimide (DTCM-g) as a new therapeutic strategy in two OS cell lines, HOS and MG-63. Our results showed that low concentrations (2.5, 5, 10, and 20 μg/mL) of the drug significantly decreased cell proliferation and clonogenic capacity, albeit it did not significantly induce cell death. DTCM-g also decreased cell invasiveness, and inhibited PDPN, MMP-2, TIMP1, and TIMP2 expressions. Moreover, our results showed that DTCM-g synergized with ionizing radiation in both cell lines while chemosensitized MG-63 cells to doxorubicin treatment. Even though additional laboratorial and preclinical tests are still needed to support our data, we demonstrate that DTCM-g inhibits growth in OS cells, increases the cytotoxicity of other commonly used agents, and may possess antimetastatic activity.

Galectin-3 increases the motility of mouse melanoma cells by regulating matrix metalloproteinase-1 expression

Although mounting evidence indicates the involvement of galectin-3 in cancer progression and metastasis, the underlying molecular mechanisms remain largely unknown. In this study, we investigated the effect and possible mechanism of galectin-3 on the migration and invasion of B16F10, a metastatic melanoma cell line, in which galectin-3 and matrix metalloproteinase- 1 (MMP-1) were both found to be highly expressed. Knockdown of galectin-3 with specific siRNA reduced migration and invasion, which was associated with reduced expression of MMP-1. To further investigate the underlying mechanism, we examined the effect of galectin-3 knockdown on the activity of AP-1, a transcriptional factor regulating MMP-1 expression. We found that galectin-3 directly interacted with AP-1 and facilitated the binding of this complex to the MMP-1 promoter that drives MMP-1 transcription. Moreover, silencing of galectin-3 inhibited binding of fra-1 and c-Jun to promoter sites of MMP-1 gene. Consistent with these in vitro findings, our in vivo study demonstrated that galectin-3 shRNA treatment significantly reduced the total number of mouse lung metastatic nodules. Taken together, galectin- 3 facilitates cell migration and invasion in melanoma in vitro and can induce metastasis in vivo, in part through, regulating the transcription activity of AP-1 and thereby up-regulating MMP-1 expression.

Insidious role of nitric oxide in migration/invasion of colon cancer cells by upregulating MMP-2/9 via activation of cGMP-PKG-ERK signaling pathways

Nitric oxide (NO), an uncharged free radical is implicated in various physiological and pathological processes. The present study is an investigation on the effect of NO on proliferation, apoptosis and migration of colon cancer cells. Colon adenocarcinoma cells, WiDr, were used for the in vitro experiments. Tissues from colon adenocarcinoma, adjacent normal and inflammatory tissue and lymph node with metastasis were evaluated for iNOS, MMP-2/9 and Fra-1/Fra-2. NO increases the proliferation of cancer cells and simultaneously prevents apoptosis. Expression of MMP-2/9, RhoB and Rac-1 was enhanced by NO in a time dependent manner. Further, NO increased phosphorylation of ERK1/2 and induced nuclear translocation of Fra-1 and Fra-2. Electrophoretic mobility shift analysis and use of deletion mutant promoter constructs identified role of AP-1 in NO-mediated regulation of MMP-2/9. iNOS, MMP-2/9, Fra-1 and Fra-2 in normal and colon adenocarcinoma tissues were analyzed and it was found that increased expression of these proteins in cancer when compared to normal provides support to our in vitro findings. The study showed that the NO-cGMP-PKG promotes MMP-2/9 expression by activating ERK-1/2 and AP-1. This study reveals the insidious role of NO in imparting tumor aggressiveness.

Histone H3 phosphorylation, immediate-early gene expression, and the nucleosomal response: a historical perspective1This article is part of Special Issue entitled Asilomar Chromatin and has undergone the Journal’s usual peer review process

Histone H3 is modified at serines 10 and 28 in interphase cells following activation of the RAS-MAPK or p38-MAPK pathways by growth factors or stress. These modifications are involved in the regulation of immediate-early genes, including Jun and Fos, whose increased expression is a trademark of various cancers. This review outlines the series of discoveries that led to the characterization of these modifications, the kinase, MSK1/2, which is activated by both MAPK pathways and directs phosphorylation of H3, and the mechanistic function of these modifications in transcriptional activation. Research examining the effect of deregulated MSK1/2 in human disorders, namely cancer, is evaluated. Recently, a number of reports proposed novel, intervening pathways leading to enrichment of phosphorylated serine 10 and 28 and the activation of MSK1/2. These novel pathways predict an even more complicated signalling mechanism for cell growth, apoptosis, and the immune response, suggesting that MSK1/2 is intrinsically responsible for an even greater number of biological processes. This review proposes that MSK1/2 is an optimal target for cancer therapy, based on its fundamental role in transmitting external signals into varied responses involved in cancer development.

Upregulation of equine matrix metalloproteinase 1 by bovine papillomavirus type 1 is through the transcription factor activator protein-1

Equine sarcoids represent the most common skin tumours in equids worldwide, characterized by extensive invasion and infiltration of lymphatics, rare regression and high recurrence after surgical intervention. Bovine papillomavirus type 1 (BPV-1) activity is necessary for the transformation phenotype of equine fibroblasts. Among the many changes induced by BPV-1, matrix metalloproteinase 1 (MMP-1) upregulation contributes to the invasiveness of equine fibroblasts. However, it is not yet known how BPV-1 proteins regulate equine MMP-1 expression. To elucidate this mechanism, the equine MMP-1 promoter was cloned and analysed. A putative activator protein-1 (AP-1)-binding site was demonstrated to be crucial for upregulated MMP-1 promoter activity by BPV-1. BPV-1 E6 and E7 proteins increased MMP-1 promoter activity, and inhibition of BPV-1 gene expression by small interfering RNA significantly reduced the promoter activity. c-Jun and Fra-1, two components of the AP-1 transcription factor complex, were overexpressed and activated by BPV-1 in equine fibroblasts. Finally, BPV-1 E5, E6 and E7 proteins increased MMP-1 mRNA and protein expression. In conclusion, the expression of MMP-1 can be enhanced by BPV-1 oncoproteins E6 and E7 through the AP-1 transcription factor and by E5 via an indirect mechanism. These findings shed light on the mechanism of BPV-1-mediated equine fibroblast infiltration and indicate that both BPV-1 oncoproteins and AP-1 could be potential targets for equine sarcoid therapy.

RegNetB: predicting relevant regulator-gene relationships in localized prostate tumor samples

Background

A central question in cancer biology is what changes cause a healthy cell to form a tumor. Gene expression data could provide insight into this question, but it is difficult to distinguish between a gene that causes a change in gene expression from a gene that is affected by this change. Furthermore, the proteins that regulate gene expression are often themselves not regulated at the transcriptional level. Here we propose a Bayesian modeling framework we term RegNetB that uses mechanistic information about the gene regulatory network to distinguish between factors that cause a change in expression and genes that are affected by the change. We test this framework using human gene expression data describing localized prostate cancer progression.

Results

The top regulatory relationships identified by RegNetB include the regulation of RLN1, RLN2, by PAX4, the regulation of ACPP (PAP) by JUN, BACH1 and BACH2, and the co-regulation of PGC and GDF15 by MAZ and TAF8. These target genes are known to participate in tumor progression, but the suggested regulatory roles of PAX4, BACH1, BACH2, MAZ and TAF8 in the process is new.

Conclusion

Integrating gene expression data and regulatory topologies can aid in identifying potentially causal mechanisms for observed changes in gene expression.

Animal models of osteosarcoma

Appendicular osteosarcoma (OS) is a primary mesenchymal tumor arising from malignantly transformed osteoblasts. In people, OS is the most common nonhematopoietic, primary skeletal neoplasm diagnosed in adolescents and is the second leading cause of cancer-related fatalities within this age group. Despite aggressive therapeutic management, including limb-sparing surgeries and dose-intense systemic chemotherapies, 30-40% of patients will experience progressive metastatic disease within 5 years of diagnosis. In order to reduce the fatality rate associated with recurrent or metastatic OS, a more thorough understanding of OS pathogenesis and biology is required. Towards this pursuit, comparative animal models of OS have been developed and are actively being studied to expand our fundamental understanding of OS. It is anticipated that specific animal models of OS, which most accurately recapitulate the natural disease process in people, will be most useful for advancing our understanding of OS biology, and will facilitate the discovery of disease pathogenesis and the identification of novel therapeutic strategies for managing this lethal metastatic bone sarcoma.

The molecular pathogenesis of osteosarcoma: a review

Osteosarcoma is the most common primary malignancy of bone. It arises in bone during periods of rapid growth and primarily affects adolescents and young adults. The 5-year survival rate for osteosarcoma is 60%-70%, with no significant improvements in prognosis since the advent of multiagent chemotherapy. Diagnosis, staging, and surgical management of osteosarcoma remain focused on our anatomical understanding of the disease. As our knowledge of the molecular pathogenesis of osteosarcoma expands, potential therapeutic targets are being identified. A comprehensive understanding of these mechanisms is essential if we are to improve the prognosis of patients with osteosarcoma through tumour-targeted therapies. This paper will outline the pathogenic mechanisms of osteosarcoma oncogenesis and progression and will discuss some of the more frontline translational studies performed to date in search of novel, safer, and more targeted drugs for disease management.

Downregulation of AP-1 gene expression is an initial event in the oridonin-mediated inhibition of colorectal cancer: studies in vitro and in vivo

BACKGROUND AND AIM

Oridonin is the active ingredient isolated from the Chinese herb Rabdosia rubescens. We used both in vivo and in vitro approaches to elucidate the underlying mechanism of the oridonin-mediated inhibition of colorectal cancer.

METHODS

Two colorectal cell lines, Lovo and SW480, were treated with oridonin in solution. The effect of this treatment on the inhibition of the cell proliferation rate was determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. The changes in gene expression that occurred in both cell lines in response to treatment with oridonin were determined via an illumine expression sensor. Additionally, a colorectal cancer colostomy implantation model was established. Animals were injected intraperitoneally with an oridonin solution.

RESULTS

The treatment of Lovo and SW480 cells with oridonin inhibited cell proliferation in a dose-dependent manner. Furthermore, the rate of inhibition increased with prolonged treatment. The growth rate of the colorectal cancer colostomy implantation model was significantly lower than control cells when treated with oridonin (P<0.001), which meant that oridonin treatment had a significant effect on the tumor growth rate. In the tumor model, activator protein-1 (AP-1) was the only gene found to be downregulated after oridonin treatment by the gene expression sensor. After 4 weeks of treatment, AP-1, nuclear factor-κB (NF-κB) and P38 were all found to be downregulated.

CONCLUSIONS

Our study confirmed the inhibitory effects of oridonin on colorectal cancer. These results indicate that the downregulation of AP-1 might be an initial response to treatment by oridonin. This regulation could, in turn, affect the expression of the NF-κB and mitogen-activated protein kinase pathways, thereby inhibiting tumor growth.

A dominant-negative c-jun mutant inhibits lung carcinogenesis in mice

Lung cancer is the leading cause of cancer mortality in the United States and worldwide. The identification of key regulatory and molecular mechanisms involved in lung tumorigenesis is therefore critical to increase our understanding of this disease and could ultimately lead to targeted therapies to improve prevention and treatment. Induction of members of the activator protein-1 (AP-1) transcription factor family has been described in human non-small cell lung carcinoma. Activation of AP-1 can either stimulate or repress transcription of multiple gene targets, ultimately leading to increased cell proliferation and inhibition of apoptosis. In the present study, we show induction of AP-1 in carcinogen-induced mouse lung tumors compared with surrounding normal lung tissue. We then used a transgenic mouse model directing conditional expression of the dominant-negative c-jun mutant TAM67 in lung epithelial cells to determine the effect of AP-1 inhibition on mouse lung tumorigenesis. Consistent with low AP-1 activity in normal lung tissue, TAM67 expression had no observed effects in adult mouse lung. TAM67 decreased tumor number and overall lung tumor burden in chemically induced mouse lung tumor models. The most significant inhibitory effect was observed on carcinoma burden compared with lower-grade lesions. Our results support the concept that AP-1 is a key regulator of mouse lung tumorigenesis, and identify AP-1-dependent transcription as a potential target to prevent lung tumor progression.