Increased expression of S100A6 is associated with decreased metastasis and inhibition of cell migration and anchorage independent growth in human osteosarcoma

Regulation of human papillomavirus E6 oncoprotein function via a novel ubiquitin ligase FBXO4

Previous studies have shown that E6 interacts with the E6-associated protein (E6AP) ubiquitin-protein ligase and directs its ubiquitylation activity toward several specific cellular proteins, one of the most important of which is p53. Interestingly, E6AP not only aids in the E6-directed degradation of cellular substrates but also stabilizes the E6 protein by protecting it from proteasome-mediated degradation. However, there is no information available about the ubiquitin ligases that regulate the stability and activity of the human papillomavirus (HPV) E6 oncoprotein in the absence of E6AP. Therefore, to identify these novel ubiquitin ligases, we performed high-throughput human siRNA library screen against ubiquitin ligases in clustered regularly interspaced palindromic repeat (CRISPR)-edited E6AP-knockout human embryonic kidney (HEK) 293 cells, stably expressing green fluorescent protein (GFP)-tagged HPV-18E6. We found a number of ubiquitin ligases that increase the expression of GFP-tagged 18E6 upon their knockdown in the absence of E6AP. Upon validation of the interaction of 18E6 with these ubiquitin ligases in cervical cancer-derived cell lines, we found that the knockdown of ubiquitin ligase F-box protein 4 (FBXO4), together with E6AP knockdown, leads to a dramatic increase in the levels of endogenous HPV-18E6 oncoprotein. Furthermore, our data demonstrate that the combined knockdown of FBXO4 and E6AP not only rescues the protein levels of E6 but also induces high levels of cell death in a p53-dependent manner in the HPV-positive cervical cancer cell line, HeLa. These results indicate a close interplay between FBXO4, E6AP, and p53 in the regulation of cell survival in HPV-positive cervical tumor-derived cells.

IMPORTANCE

E6-associated protein (E6AP)-mediated stabilization of human papillomavirus (HPV) E6 plays a crucial role in the development and progression of cervical and other HPV-associated cancers. This study, for the first time, identifies a novel ubiquitin ligase, FBXO4 that targets the degradation of HPV E6 oncoprotein in the absence of E6AP in cervical cancer-derived cell lines. This may have significant implications for our understanding of HPV-associated cancers by providing deeper insights into the intricate interplay between viral proteins and host cellular machinery and the development of targeted therapies.

S100a6 knockdown promotes the differentiation of dental epithelial cells toward the epidermal lineage instead of the odontogenic lineage

Tooth development is a complex process involving various signaling pathways and genes. Recent findings suggest that ion channels and transporters, including the S100 family of calcium-binding proteins, may be involved in tooth formation. However, our knowledge in this regard is limited. Therefore, this study aimed to investigate the expression of S100 family members and their functions during tooth formation. Tooth germs were extracted from the embryonic and post-natal mice and the expression of S100a6 was examined. Additionally, the effects of S100a6 knockdown and calcium treatment on S100a6 expression and the proliferation of SF2 cells were examined. Microarrays and single-cell RNA-sequencing indicated that S100a6 was highly expressed in ameloblasts. Immunostaining of mouse tooth germs showed that S100a6 was expressed in ameloblasts but not in the undifferentiated dental epithelium. Additionally, S100a6 was localized to the calcification-forming side in enamel-forming ameloblasts. Moreover, siRNA-mediated S100a6 knockdown in ameloblasts reduced intracellular calcium concentration and the expression of ameloblast marker genes, indicating that S100a6 is associated with ameloblast differentiation. Furthermore, S100a6 knockdown inhibited the ERK/PI3K signaling pathway, suppressed ameloblast proliferation, and promoted the differentiation of the dental epithelium toward epidermal lineage. Conclusively, S100a6 knockdown in the dental epithelium suppresses cell proliferation via calcium and intracellular signaling and promotes differentiation of the dental epithelium toward the epidermal lineage.

S100A6: molecular function and biomarker role

S100A6 (also called calcyclin) is a Ca2+-binding protein that belongs to the S100 protein family. S100A6 has many functions related to the cytoskeleton, cell stress, proliferation, and differentiation. S100A6 also has many interacting proteins that are distributed in the cytoplasm, nucleus, cell membrane, and outside the cell. Almost all these proteins interact with S100A6 in a Ca2+-dependent manner, and some also have specific motifs responsible for binding to S100A6. The expression of S100A6 is regulated by several transcription factors (such as c-Myc, P53, NF-κB, USF, Nrf2, etc.). The expression level depends on the specific cell type and the transcription factors activated in specific physical and chemical environments, and is also related to histone acetylation, DNA methylation, and other epigenetic modifications. The differential expression of S100A6 in various diseases, and at different stages of those diseases, makes it a good biomarker for differential diagnosis and prognosis evaluation, as well as a potential therapeutic target. In this review, we mainly focus on the S100A6 ligand and its transcriptional regulation, molecular function (cytoskeleton, cell stress, cell differentiation), and role as a biomarker in human disease and stem cells.

The Role of S100A6 in Human Diseases: Molecular Mechanisms and Therapeutic Potential

S100A6, also known as calcyclin, is a low-molecular-weight Ca2+-binding protein from the S100 family that contains two EF-hands. S100A6 is expressed in a variety of mammalian cells and tissues. It is also expressed in lung, colorectal, pancreatic, and liver cancers, as well as other cancers such as melanoma. S100A6 has many molecular functions related to cell proliferation, the cell cycle, cell differentiation, and the cytoskeleton. It is not only involved in tumor invasion, proliferation, and migration, but also the pathogenesis of other non-neoplastic diseases. In this review, we focus on the molecular mechanisms and potential therapeutic targets of S100A6 in tumors, nervous system diseases, leukemia, endometriosis, cardiovascular disease, osteoarthritis, and other related diseases.

S100A6 participates in initiation of autoimmune encephalitis and is under epigenetic control

INTRODUCTION

Autoimmune encephalitis (AE) is caused by autoantibodies attacking neuronal cell surface antigens and/or synaptic antigens. We previously demonstrated that S100A6 was hypomethylated in patients with AE and that it promoted B lymphocyte infiltration through the simulated blood-brain barrier (BBB). In this study, we focused on the epigenetic regulation of S100A6, the process by which S100A6 affects B lymphocyte infiltration, and the therapeutic potential of S100A6 antibodies.

METHODS

We enrolled and collected serum from 10 patients with AE and 10 healthy control (HC) subjects. Promoter methylation and 5-azacytidine treatment assays were conducted to observe the methylation process of S100A6. The effect of S100A6 on B lymphocytes was analyzed using an adhesion assay and leukocyte transendothelial migration (LTEM) assay. A LTEM assay was also used to compare the effects of the serum of HCs, serum of AE patients, S100A6 recombinant protein, and S100A6 antibodies on B lymphocytes.

RESULT

The promoter methylation and 5-azacytidine treatment assays confirmed that S100A6 was regulated by DNA methylation. The adhesion study demonstrated that the addition of S100A6 enhanced adhesion between B lymphocytes and a BBB endothelial cell line in a concentration-dependent manner. The LTEM assay showed that the serum of AE patients, as well as S100A6, promoted B lymphocyte infiltration and that this effect could be attenuated by S100A6 antibodies.

CONCLUSION

We clarified that S100A6 was under epigenetic regulation in patients with AE and that it helped B lymphocytes to adhere to and infiltrate the BBB endothelial layer, which could be counteracted by S100A6 antibodies. Therefore, the methylation profile of S100A6 could be a marker of the activity of AE, and countering the effect of S100A6 may be a potential treatment target for AE.

S100A6 Protein-Expression and Function in Norm and Pathology

S100A6, also known as calcyclin, is a calcium-binding protein belonging to the S100 protein family. It was first identified and purified more than 30 years ago. Initial structural studies, focused mostly on the mode and affinity of Ca²⁺ binding and resolution of the resultant conformational changes, were soon complemented by research on its expression, localization and identification of binding partners. With time, the use of biophysical methods helped to resolve the structure and versatility of S100A6 complexes with some of its ligands. Meanwhile, it became clear that S100A6 expression was altered in various pathological states and correlated with the stage/progression of many diseases, including cancers, indicative of its important, and possibly causative, role in some of these diseases. This, in turn, prompted researchers to look for the mechanism of S100A6 action and to identify the intermediary signaling pathways and effectors. After all these years, our knowledge on various aspects of S100A6 biology is robust but still incomplete. The list of S100A6 ligands is growing all the time, as is our understanding of the physiological importance of these interactions. The present review summarizes available data concerning S100A6 expression/localization, interaction with intracellular and extracellular targets, involvement in Ca²⁺-dependent cellular processes and association with various pathologies.

HPV-18E6 Inhibits Interactions between TANC2 and SNX27 in a PBM-Dependent Manner and Promotes Increased Cell Proliferation

While a great deal is known about the role of the E6 PDZ binding motif (PBM) in modulating the cellular proteins involved in regulating cell polarity, much less is known about the consequences of E6's interactions with SNX27 and the endocytic sorting machinery. We reasoned that a potential consequence of such interactions could be to affect the fate of multiple SNX27 endosomal partners, such as transmembrane proteins or soluble accessory proteins.

SNHG1 functions as an oncogenic lncRNA and promotes osteosarcoma progression by up-regulating S100A6 via miR-493-5p

The mechanism behind the aberrant expression of S100A6 in osteosarcoma is seldom reported so far. This study sought to explore the regulatory axis targeting S100A6 involved in osteosarcoma progression. Clinical samples collected from osteosarcoma patients were used to detect the expressions of SNHG1, miR-493-5p, and S100A6 by western bolt analysis and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The effects of S100A6 on proliferation and osteogenic differentiation were investigated by the CCK-8 assay, colony formation assay, Ethynyl deoxyuridine staining, matrix mineralization assay, and alkaline phosphatase assay. The potential of lncRNAs/miRNAs targeting S100A6 was identified by the bioinformatics approach, and the results were verified by the dual luciferase assay and RNA immunoprecipitation assay. Both and rescue experiments were performed to investigate the regulatory relationship between the identified lncRNAs and S100A6. The results showed that S100A6 is highly expressed in osteosarcoma. S100A6 overexpression not only increases the proliferation but also reduces the osteogenic differentiation of osteosarcoma cells, while S1006A silence exerts the opposite effects. Then, SNHG1 is identified to directly interact with miR-493-5p to attenuate miR-493-5p binding to the 3'-untranslated region of S100A6. Notably, S100A6 silence partially rescues the effect of SNHG1 overexpression on proliferation and osteogenic differentiation of osteosarcoma cells. Furthermore, the suppressive role of SNHG1 silence in the growth of osteosarcoma xenograft tumors is countered by S100A6 overexpression. Collectively, this study reveals that S100A6 plays an important role in osteosarcoma progression, and SNHG1 promotes S100A6 expression by competitively sponging miR-493-5p.

Identification S100A9 as a potential biomarker in neuroblastoma

BACKGROUND

More than half of Neuroblastoma (NB) patients presented with distant metastases and the relapse of metastatic patients was up to 90%. It is urgent to explore a biomarker that could facilitate the prediction of metastasis in NB patients.

METHODS AND RESULTS

In the present study, we systematically analyzed Gene Expression Omnibus datasets and focused on identifying the critical molecular networks and novel key hub genes implicated in NB metastasis. In total, 176 up-regulated and 19 down-regulated differentially expressed genes (DEGs) were identified. Based on these DEGs, a PPI network composed of 150 nodes and 452 interactions was established. Through PPI network identification combined with qRT-PCR, ELISA and IHC, S100A9 was screened as an outstanding gene. Furthermore, in vitro tumorigenesis assays demonstrated that S100A9 overexpression enhanced the proliferation, migration and invasion of NB cells.

CONCLUSIONS

Taken together, our findings suggested that S100A9 could participate in NB tumorigenesis and progression. In addition, S100A9 has the potential to be used as a promising clinical biomarker in the prediction of NB metastasis.

Advances in the study of cancer metastasis and calcium signaling as potential therapeutic targets

Metastasis is still the primary cause of cancer-related mortality. However, the underlying mechanisms of cancer metastasis are not yet fully understood. Currently, the epithelial-mesenchymal transition, metabolic remodeling, cancer cell intercommunication and the tumor microenvironment including diverse stromal cells, are reported to affect the metastatic process of cancer cells. Calcium ions (Ca²⁺) are ubiquitous second messengers that manipulate cancer metastasis by affecting signaling pathways. Diverse transporter/pump/channel-mediated Ca²⁺ currents form Ca²⁺ oscillations that can be decoded by Ca²⁺-binding proteins, which are promising prognostic biomarkers and therapeutic targets of cancer metastasis. This paper presents a review of the advances in research on the mechanisms underlying cancer metastasis and the roles of Ca²⁺-related signals in these events.

Long non‑coding RNA FOXD2‑AS1 regulates the tumorigenesis and progression of breast cancer via the S100 calcium binding protein A1/Hippo signaling pathway

Breast cancer is one of the most prevalent cancer types and is accompanied by a high incidence and mortality rate, severely threatening women's health globally. Long non‑coding RNA forkhead box D2 adjacent apposite strand RNA 1 (lncRNA FOXD2‑AS1) has been identified to function as an oncogene in human cancers; however, it has rarely been investigated in breast cancer. The aim of the present study was to investigate the role of FOXD2‑AS1 in breast cancer, and to clarify the underlying mechanisms. The expression of FOXD2‑AS1 in breast cancer cell lines was first quantified by reverse transcription‑quantitative PCR, and the biological function of FOXD2‑AS1 was then determined. Cellular proliferative ability was determined by Cell Counting kit‑8 assay, and wound healing and Transwell assays were conducted to assess the cell migratory and invasive ability. Corresponding protein expression levels were determined by western blot analysis. In addition, experimental animal models were established by the subcutaneous injection of MDA‑MB‑468 cells into the right axillary lymph nodes of BALB/c nude mice, and the effects of FOXD2‑AS1 on tumor growth were observed. The results indicated that FOXD2‑AS1 expression was upregulated in breast cancer cell lines, and that FOXD2‑AS1 downregulation significantly inhibited the proliferation, migration and invasiveness of MCF‑7 and MDA‑MB‑468 cells. S100 calcium binding protein A1 (S100A1) was also upregulated in breast cancer cell lines and was positively regulated by FOXD2‑AS1. Furthermore, the inhibition of S100A1 and the overexpression of the serine/threonine‑protein kinase, large tumor suppressor homolog 1 (LATS1), inhibited the FOXD2‑AS1‑induced cellular proliferation, migration and invasiveness in breast cancer. Experimental mouse models revealed that FOXD2‑AS1 downregulation significantly inhibited tumor growth, and that the levels of phosphorylated (p‑)YAP and p‑LATS1 were upregulated by FOXD2‑AS1 knockdown, indicating that the inhibition of FOXD2‑AS1 activated Hippo/yes‑associated protein signaling. On the whole, the findings of the present study suggest that the FOXD2‑AS1/S100A1/Hippo axis is involved in the tumorigenesis and progression of breast cancer. In the future, these may contribution to the identification of more effective breast cancer treatments.

Discovery of Druggable Host Factors Critical to Plasmodium Liver-Stage Infection

Plasmodium parasites undergo an obligatory and asymptomatic developmental stage within the liver before infecting red blood cells to cause malaria. The hijacked host pathways critical to parasite infection during this hepatic phase remain poorly understood. Here, we implemented a forward genetic screen to identify over 100 host factors within the human druggable genome that are critical to P. berghei infection in hepatoma cells. Notably, we found knockdown of genes involved in protein trafficking pathways to be detrimental to parasite infection. The disruption of protein trafficking modulators, including COPB2 and GGA1, decreases P. berghei parasite size, and an immunofluorescence study suggests that these proteins are recruited to the Plasmodium parasitophorous vacuole in infected hepatocytes. These findings reveal that various host intracellular protein trafficking pathways are subverted by Plasmodium parasites during the liver stage and provide new insights into their manipulation for growth and development.

Monensin inhibits cell proliferation and tumor growth of chemo-resistant pancreatic cancer cells by targeting the EGFR signaling pathway

Pancreatic ductal adenocarcinoma (PDAC) is one of the most deadly malignancies with <5% five-year survival rate due to late diagnosis, limited treatment options and chemoresistance. There is thus an urgent unmet clinical need to develop effective anticancer drugs to treat pancreatic cancer. Here, we study the potential of repurposing monensin as an anticancer drug for chemo-resistant pancreatic cancer. Using the two commonly-used chemo-resistant pancreatic cancer cell lines PANC-1 and MiaPaCa-2, we show that monensin suppresses cell proliferation and migration, and cell cycle progression, while solicits apoptosis in pancreatic cancer lines at a low micromole range. Moreover, monensin functions synergistically with gemcitabine or EGFR inhibitor erlotinib in suppressing cell growth and inducing cell death of pancreatic cancer cells. Mechanistically, monensin suppresses numerous cancer-associated pathways, such as E2F/DP1, STAT1/2, NFkB, AP-1, Elk-1/SRF, and represses EGFR expression in pancreatic cancer lines. Furthermore, the in vivo study shows that monensin blunts PDAC xenograft tumor growth by suppressing cell proliferation via targeting EGFR pathway. Therefore, our findings demonstrate that monensin can be repurposed as an effective anti-pancreatic cancer drug even though more investigations are needed to validate its safety and anticancer efficacy in pre-clinical and clinical models.

Prognostic Roles of mRNA Expression of S100 in Non-Small-Cell Lung Cancer

The S100 protein family is involved in cancer cell invasion and metastasis, but its prognostic value in non-small-cell lung cancer (NSCLC) has not been elucidated. In the present study we investigated the prognostic role of mRNA expression of each individual S100 in NSCLC patients through the Kaplan-Meier plotter (KM plotter) database. Expression of 14 members of the S100 family correlated with overall survival (OS) for all NSCLC patients; 18 members were associated with OS in adenocarcinoma, but none were associated with OS in squamous cell carcinoma. In particular, high mRNA expression level of S100B was associated with better OS in NSCLC patients. The prognostic value of S100 according to smoking status, pathological grades, clinical stages, and chemotherapeutic treatment of NSCLC was further assessed. Although the results should be further verified in clinical trials our findings provide new insights into the prognostic roles of S100 proteins in NSCLC and might promote development of S100-targeted inhibitors for the treatment of NSCLC.

A review of S100 protein family in lung cancer

S100 protein family, representing 25 relatively small calcium binding proteins, has been reported to be involved in multiple stages of tumorigenesis and progression. These proteins are considered having potential value to be adopted as novel biomarkers in the detection and accurate prediction of many kinds of tumors, including lung cancer. As the one having the highest morbidity and mortality among all cancers, lung carcinoma is still occult for detection, especially at early stage. S100 proteins take participation in the lung neoplasia through playing intracellular and/or extracellular functions, therefore getting involved in a variety of biological processes such as differentiation, proliferation, and migration. A few members have also been testified to modulate TGF-β/Smad-3 mediated transcriptional activity of target genes involved in tumor promotion. In addition to that, a number of proteins in this family have already been reported to experience an abnormal trend in lung cancer at cell, serum and tissue levels. Thus, S100 proteins may serve as effective biomarkers for suspected or already diagnosed lung cancer patients. In future, S100 protein family might be applied as therapeutic targets in clinical treatment of lung cancer. In this review, we firstly summed up the biological and clinical evidence connecting S100 proteins and lung cancer, which has not been summarized before.

Immunohistochemical Validation of Spontaneously Arising Canine Osteosarcoma as a Model for Human Osteosarcoma

Osteosarcoma (OS) originates from bone-forming mesenchymal cells and represents one of the primary bone tumours. It is the most common primary bone tumour in dogs and man. The characterization of an appropriate natural disease animal model to study human OS is essential to elucidate the pathogenesis of the disease. This study aimed to validate canine OS as a model for the human disease by evaluating immunohistochemically the expression of markers known to be important in human OS. The immunohistochemical panel included vimentin, alkaline phosphatase (ALP), desmin, S100, neuron-specific enolase (NSE), runt-related transcription factor 2 (Runx2) and bone morphogenetic protein 4 (BMP4). Immunohistochemistry was conducted on formalin-fixed, paraffin wax-embedded tissue sections from 59 dogs with confirmed primary OS. Vimentin, ALP, Runx2 and BMP4 were highly expressed by all tumours, while desmin, S100 and NSE were expressed variably. The findings were similar to those described previously for human OS and suggest that canine OS may represent a useful model for the study of the human disease.

Anthelmintic mebendazole enhances cisplatin's effect on suppressing cell proliferation and promotes differentiation of head and neck squamous cell carcinoma (HNSCC)

Head and neck squamous cell carcinoma (HNSCC) is one of the most common and aggressive types of human cancers worldwide. Nearly a half of HNSCC patients experience recurrence within five years of treatment and develop resistance to chemotherapy. Thus, there is an urgent clinical need to develop safe and novel anticancer therapies for HNSCC. Here, we investigate the possibility of repurposing the anthelmintic drug mebendazole (MBZ) as an anti-HNSCC agent. Using the two commonly-used human HNSCC lines CAL27 and SCC15, we demonstrate MBZ exerts more potent anti-proliferation activity than cisplatin in human HNSCC cells. MBZ effectively inhibits cell proliferation, cell cycle progression and cell migration, and induces apoptosis of HNSCC cells. Mechanistically, MBZ can modulate the cancer-associated pathways including ELK1/SRF, AP1, STAT1/2, MYC/MAX, although the regulatory outcomes are context-dependent. MBZ also synergizes with cisplatin in suppressing cell proliferation and inducing apoptosis of human HNSCC cells. Furthermore, MBZ is shown to promote the terminal differentiation of CAL27 cells and keratinization of CAL27-derived xenograft tumors. Our results are the first to demonstrate that MBZ may exert its anticancer activity by inhibiting proliferation while promoting differentiation of certain HNSCC cancer cells. It's conceivable the anthelmintic drug MBZ can be repurposed as a safe and effective agent used in combination with other frontline chemotherapy drugs such as cisplatin in HNSCC treatment.

Calcium-regulatory proteins as modulators of chemotherapy in human neuroblastoma

Neuroblastoma (NB) is a pediatric cancer treated with poly-chemotherapy including platinum complexes (e.g. cisplatin (CDDP), carboplatin), DNA alkylating agents, and topoisomerase I inhibitors (e.g. topotecan (TOPO)). Despite aggressive treatment, NB may become resistant to chemotherapy. We investigated whether CDDP and TOPO treatment of NB cells interacts with the expression and function of proteins involved in regulating calcium signaling. Human neuroblastoma cell lines SH-SY5Y, IMR-32 and NLF were used to investigate the effects of CDDP and TOPO on cell viability, apoptosis, calcium homeostasis, and expression of selected proteins regulating intracellular calcium concentration ([Ca²⁺]_i). In addition, the impact of pharmacological inhibition of [Ca²⁺]_i-regulating proteins on neuroblastoma cell survival was studied. Treatment of neuroblastoma cells with increasing concentrations of CDDP (0.1−10 μM) or TOPO (0.1 nM−1 μM) induced cytotoxicity and increased apoptosis in a concentration- and time-dependent manner. Both drugs increased [Ca²⁺]_i over time. Treatment with CDDP or TOPO also modified mRNA expression of selected genes encoding [Ca²⁺]_i-regulating proteins. Differentially regulated genes included S100A6, ITPR1, ITPR3, RYR1 and RYR3. With FACS and confocal laser scanning microscopy experiments we validated their differential expression at the protein level. Importantly, treatment of neuroblastoma cells with pharmacological modulators of [Ca²⁺]_i-regulating proteins in combination with CDDP or TOPO increased cytotoxicity. Thus, our results confirm an important role of calcium signaling in the response of neuroblastoma cells to chemotherapy and suggest [Ca²⁺]_i modulation as a promising strategy for adjunctive treatment.

S100A6 protein: functional roles

S100A6 protein belongs to the A group of the S100 protein family of Ca2+-binding proteins. It is expressed in a limited number of cell types in adult normal tissues and in several tumor cell types. As an intracellular protein, S100A6 has been implicated in the regulation of several cellular functions, such as proliferation, apoptosis, the cytoskeleton dynamics, and the cellular response to different stress factors. S100A6 can be secreted/released by certain cell types which points to extracellular effects of the protein. RAGE (receptor for advanced glycation endproducts) and integrin β1 transduce some extracellular S100A6's effects. Dosage of serum S100A6 might aid in diagnosis in oncology.

Effects of S100A6 gene silencing on the biological features of eutopic endometrial stromal cells and β‑catenin expression

Protein expression levels of S100 calcium binding protein A6 (S100A6) are increased in various malignancies and are associated with tumor behavior; however, the association between S100A6 and endometriosis remains to be elucidated. In order to investigate the influence of S100A6 protein, recombinant lentivirus siS100A6 was used to transfect the eutopic endometrial stromal cells. CCK-8 assay was performed to identify the proliferation ability of cell and the cell migration was detected by Transwell assay. Flow cytometry was performed to detect cell apoptosis, and western blotting and reverse transcription-quantitative polymerase chain reaction were performed to identify the expression of β-catenin. The present study investigated the role of S100A6 in endometriosis and its interaction with β-catenin by transfecting eutopic endometrial stromal cells with a recombinant lentivirus containing S100A6-specific small interfering RNA. Inhibition of S100A6 expression had a significant antiproliferative effect and reduced the migratory ability of eutopic endometrial stromal cells, and induced their apoptosis. In addition, inhibition of S100A6 expression suppressed β-catenin expression. These results suggested that inhibition of S100A6 may represent a promising novel approach for the targeted therapy of endometriosis.

Characterization of the metastatic phenotype of a panel of established osteosarcoma cells

Osteosarcoma (OS) is the most common bone tumor in pediatric patients. Metastasis is a major cause of mortality and morbidity. The rarity of this disease coupled with the challenges of drug development for metastatic cancers have slowed the delivery of improvements in long-term outcomes for these patients. In this study, we collected 18 OS cell lines, confirmed their expression of bone markers and complex karyotypes, and characterized their in vivo tumorgenicity and metastatic potential. Since prior reports included conflicting descriptions of the metastatic and in vivo phenotypes of these models, there was a need for a comparative assessment of metastatic phenotypes using identical procedures in the hands of a single investigative group. We expect that this single characterization will accelerate the study of this metastatic cancer. Using these models we evaluated the expression of six previously reported metastasis-related OS genes. Ezrin was the only gene consistently differentially expressed in all the pairs of high/low metatstatic OS cells. We then used a subtractive gene expression approach of the high and low human metastatic cells to identify novel genes that may be involved in OS metastasis. PHLDA1 (pleckstrin homology-like domain, family A) was identified as one of the genes more highly expressed in the high metastatic compared to low metastatic cells. Knocking down PHLDA1 with siRNA or shRNA resulted in down regulation of the activities of MAPKs (ERK1/2), c-Jun N-terminal kinases (JNK), and p38 mitogen-activated protein kinases (MAPKs). Reducing the expression of PHLDA1 also delayed OS metastasis progression in mouse xenograft models.

Antibiotic monensin synergizes with EGFR inhibitors and oxaliplatin to suppress the proliferation of human ovarian cancer cells

Ovarian cancer is the most lethal gynecologic malignancy with an overall cure rate of merely 30%. Most patients experience recurrence within 12–24 months of cure and die of progressively chemotherapy-resistant disease. Thus, more effective anti-ovarian cancer therapies are needed. Here, we investigate the possibility of repurposing antibiotic monensin as an anti-ovarian cancer agent. We demonstrate that monensin effectively inhibits cell proliferation, migration and cell cycle progression, and induces apoptosis of human ovarian cancer cells. Monensin suppresses multiple cancer-related pathways including Elk1/SRF, AP1, NFκB and STAT, and reduces EGFR expression in ovarian cancer cells. Monensin acts synergistically with EGFR inhibitors and oxaliplatin to inhibit cell proliferation and induce apoptosis of ovarian cancer cells. Xenograft studies confirm that monensin effectively inhibits tumor growth by suppressing cell proliferation through targeting EGFR signaling. Our results suggest monensin may be repurposed as an anti-ovarian cancer agent although further preclinical and clinical studies are needed.

Diagnostic significance of S100A2 and S100A6 levels in sera of patients with non-small cell lung cancer

Biochemical markers play a significant role in the diagnosis of lung cancer. Recent studies have demonstrated a link involving S100 Calcium Binding Proteins (S100A2, S100A6) and non-small cell lung cancer (NSCLC), but the expediency of their serum levels in NSCLC has not been established. In this study, we evaluate the potential of serum S100A2 and S100A6 levels as diagnostic markers for NSCLC. Enzyme-linked immunosorbent assay (ELISA) was performed to detect the levels of S100A2 and S100A6 in 141 NSCLC patients and 150 healthy subjects. Serum levels of the two proteins in patients with NSCLC were higher compared to healthy controls (P = 0.0002 for S100A2 and P < 0.0001 for S100A6). Moreover, the levels of S100A2 and S100A6 were higher in the sera of stage I/II NSCLC patients compared to healthy controls with P = 0.01 and <0.0001, respectively. Receiver operating characteristic (ROC) analysis showed that S100A2 could distinguish NSCLC patients from healthy controls (AUC = 0.646), and S100A6 could also identify NSCLC (AUC = 0.668). Meanwhile, these two proteins showed notable capabilities for distinguishing stage I/II NSCLC from healthy controls (AUC = 0.708 for S100A2 and AUC = 0.702 for S100A6). Our results indicate that serum levels of S100A2 and S100A6 are significantly elevated in early stage NSCLC and may have the potential for NSCLC biomarker. Further studies with large sample population would help validate our findings.

Visfatin promotes osteosarcoma cell migration and invasion via induction of epithelial-mesenchymal transition

Visfatin is considered to be a biomarker in various types of cancers. However, no evidence has been reported for the direct effect of visfatin on osteosarcoma cell metastasis. The aims of the present study were to investigate the influence of visfatin on the migration and invasion of osteosarcoma cells and clarify the underlying mechanism. The expression levels of epithelial-mesenchymal transition (EMT) markers, as well as the transcriptional factor Snail-1, were first detected at both the protein and mRNA levels in U2OS osteosarcoma cells after stimulation of visfatin. Then the expression of NF-κB (p65) was detected by western blot analysis, and siRNA of Snail-1 and inhibitor of NF-κB were used to investigate the effect of visfatin. Finally, migration and invasion of the cells were detected respectively by scratch wound healing and transwell assays. Visfatin downregulated E-cadherin and upregulated N-cadherin in concentration- and time-dependent manners at the protein and mRNA levels. The expression of Snail-1 was also upregulated. Moreover, visfatin also promoted the nuclear translocation of the NF-κB pathway. Administration of siRNA of Snail-1 and the inhibitor BAY11-7082 validated the roles of Snail-1 and NF-κB in the visfatin-induced regulation of EMT markers. Migration and invasion of U2OS osteosarcoma cells were promoted following the application of visfatin. These results demonstrated that visfatin enhances the migration and invasion of osteosarcoma cells via the NF-κB/Snail-1/EMT pathway.

14-3-3ε and ζ regulate neurogenesis and differentiation of neuronal progenitor cells in the developing brain

During brain development, neural progenitor cells proliferate and differentiate into neural precursors. These neural precursors migrate along the radial glial processes and localize at their final destination in the cortex. Numerous reports have revealed that 14-3-3 proteins are involved in many neuronal activities, although their functions in neurogenesis remain unclear. Here, using 14-3-3ε/ζ double knock-out mice, we found that 14-3-3 proteins are important for proliferation and differentiation of neural progenitor cells in the cortex, resulting in neuronal migration defects and seizures. 14-3-3 deficiency resulted in the increase of δ-catenin and the decrease of β-catenin and αN-catenin. 14-3-3 proteins regulated neuronal differentiation into neurons via direct interactions with phosphorylated δ-catenin to promote F-actin formation through a catenin/Rho GTPase/Limk1/cofilin signaling pathway. Conversely, neuronal migration defects seen in the double knock-out mice were restored by phosphomimic Ndel1 mutants, but not δ-catenin. Our findings provide new evidence that 14-3-3 proteins play important roles in neurogenesis and neuronal migration via the regulation of distinct signaling cascades.

S100A6 as a potential serum prognostic biomarker and therapeutic target in gastric cancer

BACKGROUND

Increased expression of S100A6 in many cancer tissues and its association with tumor behavior and patient prognosis were demonstrated, and there are no studies analyzing the serum levels of S100A6 in patients with gastric cancer (GC).

AIM

Serum S100A6 levels were investigated as a marker of tumor aggressiveness in patients with GC, and the S100A6 gene was examined as a potential therapeutic target in GC.

METHODS

Serum S100A6 levels were detected in 103 GC patients and 72 healthy subjects by ELISA. Clinicopathological features of GC patients were analyzed in correlation to serum S100A6 levels. Two small interfering RNAs against S100A6 (siRNA1-S100A6 and siRNA2-S100A6) were generated and transfected into SGC7901 cells using pSUPER gfp-neo vector, and the effects of S100A6 knockdown on cell proliferation, invasion and apoptosis were evaluated in vitro. The effects of S100A6 silencing on tumor growth and metastasis were evaluated in vivo in a pseudo-metastatic GC nude mouse model.

RESULTS

Serum S100A6 levels were significantly higher in GC patients than in healthy controls (P < 0.001). Serum S100A6 levels were significantly correlated with lymph node metastasis, TNM stage, perineural invasion and vascular invasion. Serum S100A6 level was an independent predictor of overall survival. SiRNA-mediated silencing of S100A6 significantly induced apoptosis and decreased proliferation, clone formation and the invasiveness of GC SGC7901 cells in vitro and significantly reduced tumor volume and number in vivo (P < 0.01).

CONCLUSION

Serum S100A6 level may serve as a potential prognostic biomarker in GC. Inhibition of S100A6 decreased the metastatic potential of GC cells.

Bone morphogenetic protein 2 inhibits the proliferation and growth of human colorectal cancer cells

Colorectal cancer (CRC) is one of the most deadly cancers worldwide. Significant progress has been made in understanding the molecular pathogenesis of CRC, which has led to successful early diagnosis, surgical intervention and combination chemotherapy. However, limited therapeutic options are available for metastatic and/or drug-resistant CRC. While the aberrantly activated Wnt/β-catenin pathway plays a critical initiating role in CRC development, disruption of the bone morphogenetic protein (BMP) pathway causes juvenile polyposis syndrome, suggesting that BMP signaling may play a role in CRC development. However, conflicting results have been reported concerning the possible roles of BMP signaling in sporadic colon cancer. Here, we investigated the effect of BMP2 on the proliferation, migration, invasiveness and tumor growth capability of human CRC cells. Using an adenovirus vector that overexpresses BMP2 and the piggyBac transposon-mediated stable BMP2 overexpression CRC line, we found that exogenous BMP2 effectively inhibited HCT116 cell proliferation and colony formation. BMP2 was shown to suppress colon cancer cell migration and invasiveness. Under a low serum culture condition, forced expression of BMP2 induced a significantly increased level of apoptosis in HCT116 cells. Using a xenograft tumor model, we found that forced expression of BMP2 in HCT116 cells suppressed tumor growth, accompanied by decreased cell proliferation activity. Taken together, our results strongly suggest that BMP2 plays an important inhibitory role in governing the proliferation and aggressive features of human CRC cells.

Joining S100 proteins and migration: for better or for worse, in sickness and in health

The vast diversity of S100 proteins has demonstrated a multitude of biological correlations with cell growth, cell differentiation and cell survival in numerous physiological and pathological conditions in all cells of the body. This review summarises some of the reported regulatory functions of S100 proteins (namely S100A1, S100A2, S100A4, S100A6, S100A7, S100A8/S100A9, S100A10, S100A11, S100A12, S100B and S100P) on cellular migration and invasion, established in both culture and animal model systems and the possible mechanisms that have been proposed to be responsible. These mechanisms involve intracellular events and components of the cytoskeletal organisation (actin/myosin filaments, intermediate filaments and microtubules) as well as extracellular signalling at different cell surface receptors (RAGE and integrins). Finally, we shall attempt to demonstrate how aberrant expression of the S100 proteins may lead to pathological events and human disorders and furthermore provide a rationale to possibly explain why the expression of some of the S100 proteins (mainly S100A4 and S100P) has led to conflicting results on motility, depending on the cells used.

Separate and combined effects of DNMT and HDAC inhibitors in treating human multi-drug resistant osteosarcoma HosDXR150 cell line

Understanding the molecular mechanisms underlying multi-drug resistance (MDR) is one of the major challenges in current cancer research. A phenomenon which is common to both intrinsic and acquired resistance, is the aberrant alteration of gene expression in drug-resistant cancers. Although such dysregulation depends on many possible causes, an epigenetic characterization is considered a main driver. Recent studies have suggested a direct role for epigenetic inactivation of genes in determining tumor chemo-sensitivity. We investigated the effects of the inhibition of DNA methyltransferase (DNMT) and hystone deacethylase (HDAC), considered to reverse the epigenetic aberrations and lead to the re-expression of de novo methylated genes in MDR osteosarcoma (OS) cells. Based on our analysis of the HosDXR150 cell line, we found that in order to reduce cell proliferation, co-treatment of MDR OS cells with DNMT (5-Aza-dC, DAC) and HDAC (Trichostatin A, TSA) inhibitors is more effective than relying on each treatment alone. In re-expressing epigenetically silenced genes induced by treatments, a very specific regulation takes place which suggests that methylation and de-acetylation have occurred either separately or simultaneously to determine MDR OS phenotype. In particular, functional relationships have been reported after measuring differential gene expression, indicating that MDR OS cells acquired growth and survival advantage by simultaneous epigenetic inactivation of both multiple p53-independent apoptotic signals and osteoblast differentiation pathways. Furthermore, co-treatment results more efficient in inducing the re-expression of some main pathways according to the computed enrichment, thus emphasizing its potential towards representing an effective therapeutic option for MDR OS.

Establishing an osteosarcoma associated protein-protein interaction network to explore the pathogenesis of osteosarcoma

Background

The aim of this study was to establish an osteosarcoma (OS) associated protein-protein interaction network and explore the pathogenesis of osteosarcoma.

Methods

The gene expression profile GSE9508 was downloaded from the Gene Expression Omnibus database, including five samples of non-malignant bone (the control), seven samples for non-metastatic patients (six of which were analyzed in duplicate), and 11 samples for metastatic patients (10 of which were analyzed in duplicate). Differentially expressed genes (DEGs) between osteosarcoma and control samples were identified by packages in R with the threshold of |logFC (fold change)| > 1 and false discovery rate < 0.05. Osprey software was used to construct the interaction network of DEGs, and genes at protein-protein interaction (PPI) nodes with high degrees were identified. The Database for Annotation, Visualization and Integrated Discovery and WebGestalt software were then used to perform functional annotation and pathway enrichment analyses for PPI networks, in which P < 0.05 was considered statistically significant.

Results

Compared to the control samples, the expressions of 42 and 341 genes were altered in non-metastatic OS and metastatic OS samples, respectively. A total of 15 significantly enriched functions were obtained with Gene Ontology analysis (P < 0.05). The DEGs were classified and significantly enriched in three pathways, including the tricarboxylic acid cycle, lysosome and axon guidance. Genes such as HRAS, IDH3A, ATP6ap1, ATP6V0D2, SEMA3F and SEMA3A were involved in the enriched pathways.

Conclusions

The hub genes from metastatic OS samples are not only bio-markers of OS, but also help to improve therapies for OS.

Peromyscus (deer mice) as developmental models

Deer mice (Peromyscus) are the most common native North American mammals, and exhibit great natural genetic variation. Wild-derived stocks from a number of populations are available from the Peromyscus Genetic Stock Center (PGSC). The PGSC also houses a number of natural variants and mutants (many of which appear to differ from Mus). These include metabolic, coat-color/pattern, neurological, and other morphological variants/mutants. Nearly all these mutants are on a common genetic background, the Peromyscus maniculatus BW stock. Peromyscus are also superior behavior models in areas such as repetitive behavior and pair-bonding effects, as multiple species are monogamous. While Peromyscus development generally resembles that of Mus and Rattus, prenatal stages have not been as thoroughly studied, and there appear to be intriguing differences (e.g., longer time spent at the two-cell stage). Development is greatly perturbed in crosses between P. maniculatus (BW) and Peromyscus polionotus (PO). BW females crossed to PO males produce growth-restricted, but otherwise healthy, fertile offspring which allows for genetic analyses of the many traits that differ between these two species. PO females crossed to BW males produce overgrown but severely dysmorphic conceptuses that rarely survive to late gestation. There are likely many more uses for these animals as developmental models than we have described here. Peromyscus models can now be more fully exploited due to the emerging genetic (full linkage map), genomic (genomes of four stocks have been sequenced) and reproductive resources.

Increased expression of S100A6 promotes cell proliferation and migration in human hepatocellular carcinoma

High levels of S100A6 have been associated with poor outcome in some types of human cancers, but the role of S100A6 in the molecular pathogenesis of these cancers is largely unknown. This study was performed to explore the expression and functional roles of S100A6 in hepatocellular carcinoma (HCC). The expression level of S100A6 in HCC tumor and corresponding peritumoral tissues were determined by immunohistochemistry analysis. The potential functions of S100A6 in tumorigenesis and metastasis were analyzed by cell proliferation, migration, and invasion assays in human liver cancer cells. Moreover, through expression and purification of S100A6 recombinant protein tagged with cell-penetrating peptide, we analyzed its complex extracellular/intracellular effects in a S100A6-silenced cellular model. As a result, the expression of S100A6 was up-regulated in human HCC compared with adjacent peritumoral tissues. S100A6 silencing inhibited the growth and motility of HCC cells, while intracellular re-expression of S100A6 could rescue the proliferation and migration defects. Intracellular over-expression of S100A6 resulted in down-regulation of E-cadherin expression and promoted nuclear accumulation of β-catenin. Moreover, we found that the enhanced cell proliferation and motility after S100A6 stimulation were dependent on the activation of PI3K/AKT pathway. These results suggest that S100A6 may be involved in promotion and progression of human liver cancer.

KEY MESSAGES

S100A6 is overexpressed in human hepatocellular carcinoma clinical specimens. S100A6 promotes proliferation and migration of human hepatoma cells. Overexpression of S100A6 results in alteration of E-cadherin and β-catenin. The multi-effects of S100A6 may be mediated in part by PI3K/AKT pathway activation.

Phosphoproteomics of collagen receptor networks reveals SHP-2 phosphorylation downstream of wild-type DDR2 and its lung cancer mutants

Collagen is an important extracellular matrix component that directs many fundamental cellular processes including differentiation, proliferation and motility. The signalling networks driving these processes are propagated by collagen receptors such as the β1 integrins and the DDRs (discoidin domain receptors). To gain an insight into the molecular mechanisms of collagen receptor signalling, we have performed a quantitative analysis of the phosphorylation networks downstream of collagen activation of integrins and DDR2. Temporal analysis over seven time points identified 424 phosphorylated proteins. Distinct DDR2 tyrosine phosphorylation sites displayed unique temporal activation profiles in agreement with in vitro kinase data. Multiple clustering analysis of the phosphoproteomic data revealed several DDR2 candidate downstream signalling nodes, including SHP-2 (Src homology 2 domain-containing protein tyrosine phosphatase 2), NCK1 (non-catalytic region of tyrosine kinase adaptor protein 1), LYN, SHIP-2 [SH2 (Src homology 2)-domain-containing inositol phosphatase 2], PIK3C2A (phosphatidylinositol-4-phosphate 3-kinase, catalytic subunit type 2α) and PLCL2 (phospholipase C-like 2). Biochemical validation showed that SHP-2 tyrosine phosphorylation is dependent on DDR2 kinase activity. Targeted proteomic profiling of a panel of lung SCC (squamous cell carcinoma) DDR2 mutants demonstrated that SHP-2 is tyrosine-phosphorylated by the L63V and G505S mutants. In contrast, the I638F kinase domain mutant exhibited diminished DDR2 and SHP-2 tyrosine phosphorylation levels which have an inverse relationship with clonogenic potential. Taken together, the results of the present study indicate that SHP-2 is a key signalling node downstream of the DDR2 receptor which may have therapeutic implications in a subset of DDR2 mutations recently uncovered in genome-wide lung SCC sequencing screens.

IGFBP5 domains exert distinct inhibitory effects on the tumorigenicity and metastasis of human osteosarcoma

Osteosarcoma (OS) is the most common primary malignancy of bone. We investigated the roles of insulin-like growth factor binding protein 5 (IGFBP5) domains in modulating OS tumorigenicity and metastasis. The N-terminal (to a lesser extent the C-terminal) domain inhibited cell proliferation and induced apoptosis while the C-terminal domain inhibited cell migration and invasion. The Linker domain had no independent effects. In vivo, the N-terminal domain decreased tumor growth without affecting pulmonary metastases while the C-terminal domain inhibited tumor growth and metastases. In summary, the N- and C-terminal domains modulated OS tumorigenic phenotypes while the C-terminal domain inhibited OS metastatic phenotypes.

Ginseng saponin metabolite 20(S)-protopanaxadiol inhibits tumor growth by targeting multiple cancer signaling pathways

Plant-derived active constituents and their semi-synthetic or synthetic analogs have served as major sources of anticancer drugs. 20(S)-protopanaxadiol (PPD) is a metabolite of ginseng saponin of both American ginseng (Panax quinquefolius L.) and Asian ginseng (Panax ginseng C.A. Meyer). We previously demonstrated that ginsenoside Rg3, a glucoside precursor of PPD, exhibits anti-proliferative effects on HCT116 cells and reduces tumor size in a xenograft model. Our subsequent study indicated that PPD has more potent antitumor activity than that of Rg3 in vitro although the mechanism underlying the anticancer activity of PPD remains to be defined. Here, we investigated the mechanism underlying the anticancer activity of PPD in human cancer cells in vitro and in vivo. PPD was shown to inhibit growth and induce cell cycle arrest in HCT116 cells. The in vivo studies indicate that PPD inhibits xenograft tumor growth in athymic nude mice bearing HCT116 cells. The xenograft tumor size was significantly reduced when the animals were treated with PPD (30 mg/kg body weight) for 3 weeks. When the expression of previously identified Rg3 targets, A kinase (PRKA) anchor protein 8 (AKAP8L) and phosphatidylinositol transfer protein α (PITPNA), was analyzed, PPD was shown to inhibit the expression of PITPNA while upregulating AKAP8L expression in HCT116 cells. Pathway-specific reporter assays indicated that PPD effectively suppressed the NF-κB, JNK and MAPK/ERK signaling pathways. Taken together, our results suggest that the anticancer activity of PPD in colon cancer cells may be mediated through targeting NF-κB, JNK and MAPK/ERK signaling pathways, although the detailed mechanisms underlying the anticancer mode of PPD action need to be fully elucidated.

Protein kinase C epsilon and genetic networks in osteosarcoma metastasis

Osteosarcoma (OS) is the most common primary malignant tumor of the bone, and pulmonary metastasis is the most frequent cause of OS mortality. The aim of this study was to discover and characterize genetic networks differentially expressed in metastatic OS. Expression profiling of OS tumors, and subsequent supervised network analysis, was performed to discover genetic networks differentially activated or organized in metastatic OS compared to localized OS. Broad trends among the profiles of metastatic tumors include aberrant activity of intracellular organization and translation networks, as well as disorganization of metabolic networks. The differentially activated PRKCε-RASGRP3-GNB2 network, which interacts with the disorganized DLG2 hub, was also found to be differentially expressed among OS cell lines with differing metastatic capacity in xenograft models. PRKCε transcript was more abundant in some metastatic OS tumors; however the difference was not significant overall. In functional studies, PRKCε was not found to be involved in migration of M132 OS cells, but its protein expression was induced in M112 OS cells following IGF-1 stimulation.

DISC1-related signaling pathways in adult neurogenesis of the hippocampus

Disrupted-in-schizophrenia 1 (DISC1) is a multifunctional scaffold protein which plays an important role in neurogenesis and neural development in the adult brain, especially in the dentate gyrus (DG) of the hippocampus. Accumulated research has unveiled the role of DISC1 in several aspects of neural development and neurogenesis, such as neuronal maturation, proliferation, migration, positioning, differentiation, dendritic growth, axonal outgrowth, and synaptic plasticity. Studies on the function of this protein have explored multiple facets, including variants and missense mutants in genetics, proteins interactivity and signaling pathways in molecular biology, and pathogenesis and treatment targets of major mental illness, and more. In this review, we present several signaling pathways discussed in recent research, such as the AKT signaling pathway, GABA signaling pathway, GSK3β signaling pathway, Wnt signaling pathway, and NMDA-R signaling pathway. DISC1 interacts, directly or indirectly, with these signaling pathways and they co-regulate the process of adult neurogenesis in the hippocampus.

Peromyscus as a Mammalian epigenetic model

Deer mice (Peromyscus) offer an opportunity for studying the effects of natural genetic/epigenetic variation with several advantages over other mammalian models. These advantages include the ability to study natural genetic variation and behaviors not present in other models. Moreover, their life histories in diverse habitats are well studied. Peromyscus resources include genome sequencing in progress, a nascent genetic map, and >90,000 ESTs. Here we review epigenetic studies and relevant areas of research involving Peromyscus models. These include differences in epigenetic control between species and substance effects on behavior. We also present new data on the epigenetic effects of diet on coat-color using a Peromyscus model of agouti overexpression. We suggest that in terms of tying natural genetic variants with environmental effects in producing specific epigenetic effects, Peromyscus models have a great potential.

Insulin-like growth factor binding protein 5 suppresses tumor growth and metastasis of human osteosarcoma

Osteosarcoma (OS) is the most common primary malignancy of bone. There is a critical need to identify the events that lead to the poorly understood mechanism of OS development and metastasis. The goal of this investigation is to identify and characterize a novel marker of OS progression. We have established and characterized a highly metastatic OS subline that is derived from the less metastatic human MG63 line through serial passages in nude mice via intratibial injections. Microarray analysis of the parental MG63, the highly metastatic MG63.2 subline, as well as the corresponding primary tumors and pulmonary metastases revealed insulin-like growth factor binding protein 5 (IGFBP5) to be one of the significantly downregulated genes in the metastatic subline. Confirmatory quantitative RT-PCR on 20 genes of interest demonstrated IGFBP5 to be the most differentially expressed and was therefore chosen to be one of the genes for further investigation. Adenoviral mediated overexpression and knockdown of IGFBP5 in the MG63 and MG63.2 cell lines, as well as other OS lines (143B and MNNG/HOS) that are independent of our MG63 lines, were employed to examine the role of IGFBP5. We found that overexpression of IGFBP5 inhibited in vitro cell proliferation, migration and invasion of OS cells. Additionally, IGFBP5 overexpression promoted apoptosis and cell cycle arrest in the G1 phase. In an orthotopic xenograft animal model, overexpression of IGFBP5 inhibited OS tumor growth and pulmonary metastases. Conversely, siRNA-mediated knockdown of IGFBP5 promoted OS tumor growth and pulmonary metastases in vivo. Immunohistochemical staining of patient-matched primary and metastatic OS samples demonstrated decreased IGFBP5 expression in the metastases. These results suggest 1) a role for IGFBP5 as a novel marker that has an important role in the pathogenesis of OS, and 2) that the loss of IGFBP5 function may contribute to more metastatic phenotypes in OS.

Tetrandrine inhibits Wnt/β-catenin signaling and suppresses tumor growth of human colorectal cancer

As one of the most common malignancies, colon cancer is initiated by abnormal activation of the Wnt/β-catenin pathway. Although the treatment options have increased for some patients, overall progress has been modest. Thus, there is a great need to develop new treatments. We have found that bisbenzylisoquinoline alkaloid tetrandrine (TET) exhibits anticancer activity. TET is used as a calcium channel blocker to treat hypertensive and arrhythmic conditions in Chinese medicine. Here, we investigate the molecular basis underlying TET's anticancer activity. We compare TET with six chemotherapy drugs in eight cancer lines and find that TET exhibits comparable anticancer activities with camptothecin, vincristine, paclitaxel, and doxorubicin, and better than that of 5-fluorouracil (5-FU) and carboplatin. TET IC₅₀ is ≤5 μM in most of the tested cancer lines. TET exhibits synergistic anticancer activity with 5-FU and reduces migration and invasion capabilities of HCT116 cells. Furthermore, TET induces apoptosis and inhibits xenograft tumor growth of colon cancer. TET treatment leads to a decrease in β-catenin protein level in xenograft tumors, which is confirmed by T-cell factor/lymphocyte enhancer factor and c-Myc reporter assays. It is noteworthy that HCT116 cells with allelic oncogenic β-catenin deleted are less sensitive to TET-mediated inhibition of proliferation, viability, and xenograft tumor growth. Thus, our findings strongly suggest that the anticancer effect of TET in colon cancer may be at least in part mediated by targeting β-catenin activity. Therefore, TET may be used alone or in combination as an effective anticancer agent.

Lysophosphatidic acid acyltransferase β (LPAATβ) promotes the tumor growth of human osteosarcoma

Background

Osteosarcoma is the most common primary malignancy of bone with poorly characterized molecular pathways important in its pathogenesis. Increasing evidence indicates that elevated lipid biosynthesis is a characteristic feature of cancer. We sought to investigate the role of lysophosphatidic acid acyltransferase β (LPAATβ, aka, AGPAT2) in regulating the proliferation and growth of human osteosarcoma cells. LPAATβ can generate phosphatidic acid, which plays a key role in lipid biosynthesis as well as in cell proliferation and survival. Although elevated expression of LPAATβ has been reported in several types of human tumors, the role of LPAATβ in osteosarcoma progression has yet to be elucidated.

Methodology/Principal Findings

Endogenous expression of LPAATβ in osteosarcoma cell lines is analyzed by using semi-quantitative PCR and immunohistochemical staining. Adenovirus-mediated overexpression of LPAATβ and silencing LPAATβ expression is employed to determine the effect of LPAATβ on osteosarcoma cell proliferation and migration in vitro and osteosarcoma tumor growth in vivo. We have found that expression of LPAATβ is readily detected in 8 of the 10 analyzed human osteosarcoma lines. Exogenous expression of LPAATβ promotes osteosarcoma cell proliferation and migration, while silencing LPAATβ expression inhibits these cellular characteristics. We further demonstrate that exogenous expression of LPAATβ effectively promotes tumor growth, while knockdown of LPAATβ expression inhibits tumor growth in an orthotopic xenograft model of human osteosarcoma.

Conclusions/Significance

Our results strongly suggest that LPAATβ expression may be associated with the aggressive phenotypes of human osteosarcoma and that LPAATβ may play an important role in regulating osteosarcoma cell proliferation and tumor growth. Thus, targeting LPAATβ may be exploited as a novel therapeutic strategy for the clinical management of osteosarcoma. This is especially attractive given the availability of selective pharmacological inhibitors.

Synergistic antitumor effect of the activated PPARgamma and retinoid receptors on human osteosarcoma

PURPOSE

Osteosarcoma is the most common primary malignancy of bone. The long-term survival of osteosarcoma patients hinges on our ability to prevent and/or treat recurrent and metastatic lesions. Here, we investigated the activation of peroxisome proliferator-activated receptor gamma (PPARgamma) and retinoid receptors as a means of differentiation therapy for human osteosarcoma.

EXPERIMENTAL DESIGN

We examined the endogenous expression of PPARgamma and retinoid receptors in a panel of osteosarcoma cells. Ligands or adenovirus-mediated overexpression of these receptors were tested to inhibit proliferation and induce apoptosis of osteosarcoma cells. Osteosarcoma cells overexpressing the receptors were introduced into an orthotopic tumor model. The effect of these ligands on osteoblastic differentiation was further investigated.

RESULTS

Endogenous expression of PPARgamma and isotypes of retinoic acid receptor (RAR) and retinoid X receptor (RXR) is detected in most osteosarcoma cells. Troglitazone, 9-cis retinoic acid (RA), and all-trans RA, as well as overexpression of PPARgamma, RARalpha, and RXRalpha, inhibit osteosarcoma cell proliferation and induce apoptosis. A synergistic inhibitory effect on osteosarcoma cell proliferation is observed between troglitazone and retinoids, as well as with the overexpression pairs of PPARgamma/RARalpha, or PPARgamma/RXRalpha. Overexpression of PPARgamma, RARalpha, RXRalpha, or in combinations inhibits osteosarcoma tumor growth and cell proliferation in vivo. Retinoids (and to a lesser extent, troglitazone) are shown to promote osteogenic differentiation of osteosarcoma cells and mesenchymal stem cells.

CONCLUSIONS

Activation of PPARgamma, RARalpha, and RXRalpha may act synergistically on inhibiting osteosarcoma cell proliferation and tumor growth, which is at least partially mediated by promoting osteoblastic differentiation of osteosarcoma cells.

Mitotic arrest defective protein 2 expression abnormality and its clinicopathologic significance in human osteosarcoma

Osteosarcoma is the most common primary malignancy of bone. Overexpression of mitotic arrest defective protein 2 (MAD2) is found in many human neoplasms, but its role in the oncogenesis of osteosarcoma is an untouched topic. The objective of this research was to observe the expression of MAD2 in human osteosarcoma and explore its clinicopathologic significance. MAD2 expression was analyzed in 48 primary osteosarcoma cases (19 osteoblastic osteosarcomas, 17 chondroblastic osteosarcomas and 12 fibroblastic osteosarcomas) using immunohistochemistry. A total of 20 normal bone specimens formed a control group. MAD2 was commonly overexpressed in human osteosarcoma. Immunopositivity was higher in tumors with lower differentiation and higher clinical stage. Increased expression of MAD2 was associated with earlier metastasis and poorer survival. Our findings provide evidence that MAD2 contributes to the pathogenesis and development of human osteosarcoma, Testing may have a clinical role in predicting prognosis, selecting appropriate chemotherapeutic strategies and providing novel strategies for osteosarcoma therapy.

Serum S100A6 concentration predicts peritoneal tumor burden in mice with epithelial ovarian cancer and is associated with advanced stage in patients

BACKGROUND

Ovarian cancer is the 5th leading cause of cancer related deaths in women. Five-year survival rates for early stage disease are greater than 94%, however most women are diagnosed in advanced stage with 5 year survival less than 28%. Improved means for early detection and reliable patient monitoring are needed to increase survival.

METHODOLOGY AND PRINCIPAL FINDINGS

Applying mass spectrometry-based proteomics, we sought to elucidate an unanswered biomarker research question regarding ability to determine tumor burden detectable by an ovarian cancer biomarker protein emanating directly from the tumor cells. Since aggressive serous epithelial ovarian cancers account for most mortality, a xenograft model using human SKOV-3 serous ovarian cancer cells was established to model progression to disseminated carcinomatosis. Using a method for low molecular weight protein enrichment, followed by liquid chromatography and mass spectrometry analysis, a human-specific peptide sequence of S100A6 was identified in sera from mice with advanced-stage experimental ovarian carcinoma. S100A6 expression was documented in cancer xenografts as well as from ovarian cancer patient tissues. Longitudinal study revealed that serum S100A6 concentration is directly related to tumor burden predictions from an inverse regression calibration analysis of data obtained from a detergent-supplemented antigen capture immunoassay and whole-animal bioluminescent optical imaging. The result from the animal model was confirmed in human clinical material as S100A6 was found to be significantly elevated in the sera from women with advanced stage ovarian cancer compared to those with early stage disease.

CONCLUSIONS

S100A6 is expressed in ovarian and other cancer tissues, but has not been documented previously in ovarian cancer disease sera. S100A6 is found in serum in concentrations that correlate with experimental tumor burden and with clinical disease stage. The data signify that S100A6 may prove useful in detecting and/or monitoring ovarian cancer, when used in concert with other biomarkers.

S100A6 binds to annexin 2 in pancreatic cancer cells and promotes pancreatic cancer cell motility

Background:

High levels of S100A6 have been associated with poor outcome in pancreatic cancer patients. The functional role of S100A6 is, however, poorly understood.

Methods:

Immunoprecipitation followed by two-dimensional gel electrophoresis and mass spectrometry were undertaken to identify S100A6 interacting proteins in pancreatic cancer cells. Immunohistochemistry and coimmunofluorescence were performed to examine expression or colocalisation of proteins. siRNA was used to deplete specific proteins and effects on motility were measured using Boyden Chamber and wound healing assays.

Results:

Our proteomic screen to identify S100A6 interacting proteins revealed annexin 11, annexin 2, tropomyosin β and a candidate novel interactor lamin B1. Of these, annexin 2 was considered particularly interesting, as, like S100A6, it is expressed early in the development of pancreatic cancer and overexpression occurs with high frequency in invasive cancer. Reciprocal immunoprecipitation confirmed the interaction between annexin 2 and S100A6 and the proteins colocalised, particularly in the plasma membrane of cultured pancreatic cancer cells and primary pancreatic tumour tissue. Analysis of primary pancreatic cancer specimens (n=55) revealed a strong association between high levels of cytoplasmic S100A6 and the presence of annexin 2 in the plasma membrane of cancer cells (P=0.009). Depletion of S100A6 was accompanied by diminished levels of membrane annexin 2 and caused a pronounced reduction in the motility of pancreatic cancer cells.

Conclusion:

These findings point towards a functional role for S100A6 that may help explain the link between S100A6 expression in pancreatic cancer and aggressive disease.