BMP-induced growth suppression in colon cancer cells is mediated by p21WAF1 stabilization and modulated by RAS/ERK

Insights into the Role of Gremlin-1, a Bone Morphogenic Protein Antagonist, in Cancer Initiation and Progression

The bone morphogenic protein (BMP) antagonist Gremlin-1 is a biologically significant regulator known for its crucial role in tissue differentiation and embryonic development. Nevertheless, it has been reported that Gremlin-1 can exhibit its function through BMP dependent and independent pathways. Gremlin-1 has also been reported to be involved in organ fibrosis, which has been correlated to the development of other diseases, such as renal inflammation and diabetic nephropathy. Based on growing evidence, Gremlin-1 has recently been implicated in the initiation and progression of different types of cancers. Further, it contributes to the stemness state of cancer cells. Herein, we explore the recent findings on the role of Gremlin-1 in various cancer types, including breast, cervical, colorectal, and gastric cancers, as well as glioblastomas. Additionally, we highlighted the impact of Gremlin-1 on cellular processes and signaling pathways involved in carcinogenesis. Therefore, it was suggested that Gremlin-1 might be a promising prognostic biomarker and therapeutic target in cancers.

Aberrant expression of the extracellular matrix component Biglycan regulated by Hedgehog signalling promotes colorectal cancer cell proliferation

Hedgehog (Hh) signalling plays essential roles in regulating embryonic development and contributes to tumour initiation, growth and progression in multiple cancers. The detailed mechanism by which Hh signalling participates in tumour growth warrants thorough study, although several downstream target genes have been identified. Herein, a set of novel targets of Hh signalling was identified in multiple types of tumour cells via RNA-Seq analysis. Among these targets, the expression regulation and oncogenic function of the extracellular matrix component biglycan (BGN) were investigated. Further investigation verified that Hh signalling activates the expression of BGN via the transcription factor Gli2, which directly binds to the promoter region of BGN. Functional assays revealed that BGN facilitates tumour cell growth and proliferation in colorectal cancer (CRC) cells, and xenograft assays confirmed that BGN also promotes tumour growth . Moreover, analysis of clinical CRC samples showed that both the protein and mRNA levels of BGN are increased in CRC tissues compared to those in adjacent tissues, and higher expression of BGN is correlated with poorer prognosis of CRC patients, further confirming the function of BGN in CRC. Taken together, aberrantly activated Hh signalling increases the expression of BGN, possibly regulates the extracellular matrix, and thereby promotes tumour growth in CRC.

Cancer-associated fibroblasts in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of mortality among cancers. Many aspects of this cancer are under investigation to find established markers of diagnosis, prognosis, and also potential drug targets. In this review article, we are going to discuss the possible solution to all these aims by investigating the literature about cancer-associated fibroblasts (CAFs) involved in CRC. Moreover, we are going to review their interaction with the tumor microenvironment (TME) and vitamin D and their role in tumorigenesis and metastasis. Moreover, we are going to expand more on some markers produced by them or related to them including FAP, a-SMA, CXCL12, TGF- β, POSTN, and β1-Integrin. Some signaling pathways related to CAFs are as follows: FAK, AKT, activin A, and YAP/TAZ. Some genes related to the CAFs which are found to be possible therapeutic targets include COL3A1, JAM3, AEBP1 and, CAF-derived TGFB3, WNT2, and WNT54.

Hyperoside suppresses BMP-7-dependent PI3K/AKT pathway in human hepatocellular carcinoma cells

Background

New therapeutics for hepatocellular carcinoma (HCC) are urgently needed and searching for new anti-cancer compounds in plant medicines may represent a promising approach. The present study was conducted to clarify the role of hyperoside (HP) and its underlying molecular mechanism in a cancer cell.

Methods

Bone morphogenetic protein 7 (BMP-7) protein expression was measure in Human HCC tissue. In in vitro experiments, HP effects on cell proliferation and the mechanism were investigated deeply.

Results

The result showed a higher expression of BMP-7 in human HCC compared to adjacent noncancerous counterparts, and that silencing of BMP-7 suppressed HepG2 cell proliferation, suggesting BMP-7 plays an anti-cancer role in HCC. Furthermore, we found that HP could induce cell cycle arrest in proliferating HepG2 cells at the G1 phase by decreasing BMP-7 expression and that the phosphorylation of AKT and expression of PI3K were significantly down-regulated upon treatment of HP or BMP-7 knockdown. In addition, silencing of BMP-7 abrogated the difference of AKT phosphorylation between cells with and without HP treatment.

Conclusions

Our results indicated that HP suppressed cell proliferation by inhibiting the BMP-7-dependent PI3K/AKT signaling pathway in HepG2 HCC cells, and either HP supplement or targeting BMP-7 might be a promising treatment against HCC.

A four-gene signature associated with clinical features can better predict prognosis in prostate cancer

Prostate cancer (PCa) is one of the most deadly urinary tumors in men globally, and the 5‐year over survival is poor due to metastasis of tumor. It is significant to explore potential biomarkers for early diagnosis and personalized therapy of PCa. In the present study, we performed an integrated analysis based on multiple microarrays in the Gene Expression Omnibus (GEO) dataset and obtained differentially expressed genes (DEGs) between 510 PCa and 259 benign issues. The weighted correlation network analysis indicated that prognostic profile was the most relevant to DEGs. Then, univariate and multivariate COX regression analyses were conducted and four prognostic genes were obtained to establish a four‐gene prognostic model. And the predictive effect and expression profiles of the four genes were well validated in another GEO dataset, The Cancer Genome Atlas and the Human Protein Atlas datasets. Furthermore, combination of four‐gene model and clinical features was analyzed systematically to guide the prognosis of patients with PCa to a largest extent. In summary, our findings indicate that four genes had important prognostic significance in PCa and combination of four‐gene model and clinical features could achieve a better prediction to guide the prognosis of patients with PCa.

Neurexophilin and PC-esterase domain family member 4 (NXPE4) and prostate androgen-regulated mucin-like protein 1 (PARM1) as prognostic biomarkers for colorectal cancer

Owing to the high morbidity and mortality, novel biomarkers in the occurrence and development of colorectal cancer (CRC) are needed nowadays. In this study, the CRC-related datasets were downloaded from the Gene Expression Omnibus (GEO) database and The Cancer Genome Atlas (TCGA) database. After screening the differentially expressed genes (DEGs) in R software, a total of 238 upregulated and 199 downregulated DEGs were revealed simultaneously. Then the Kaplan-Meier survival analysis and Cox regression analysis were used to reveal the prognostic function of these DEGs. Neurexophilin and PC-esterase domain family member 4 (NXPE4) and prostate androgen-regulated mucin-like protein 1 (PARM1) were two outstanding independent overall survival (OS) and relapse-free survival (RFS) prognostic genes of CRC in TCGA database. We next verified the expression of NXPE4 and PARM1 messenger RNA (mRNA) levels were significantly lower in CRC tumor tissue than in the adjacent noncancerous tissue in our clinical samples, and NXPE4 mRNA expression level was related to the tumor location and tumor size, while PARM1 was related to tumor location, lymph nodes metastasis, and tumor size. This study demonstrated that NXPE4 and PARM1 might be two potential novel prognostic biomarkers for CRC.

Knockdown GREM1 suppresses cell growth, angiogenesis, and epithelial-mesenchymal transition in colon cancer

Gremlin 1 (GREM1), as a bone morphogenetic protein (BMP) antagonist and vascular endothelial growth factor receptor-2 (VEGFR2) novel agonist, has been confirmed as overexpressed in colorectal cancer (CRC) tissues but its role in carcinogenesis remains unclear. Here we reported that the GREM1 expression in mesenchymal-like colon cancer cells (SW620 and SW480) was significantly higher than that of epithelial-like colon cancer cells (Caco-2, HTC116, and HT29) and normal colon cell. Simultaneously, we analyzed two series of CRC transcriptomes from Gene Expression Omnibus (GEO) databases and found the great majority of primary CRC tissues expressed high level of GREM1 messenger RNA (mRNA) compared with adjacent normal tissues, and that the GREM1 mRNA expression is correlated with low histological grade development and stage 2 to 3 metastatic recurrence in CRC based on a data analysis of 104 different stage CRC tissue from the GEO databases. Functional studies showed that GREM1 silencing by short hairpin RNA (shRNA) significantly inhibited CRC cells proliferation, migration, the formation of vascular endothelial growth factor (VEGF)-induced capillary structure of human umbilical vein endothelial cells (HUVECs), and epithelial-mesenchymal transition in colon cancer cells by repressing phosphorylation levels of BMP downstream signal Smad1, vascular endothelial growth factor (VEGF) downstream signal matrix metallopeptidase 2 (MMP2), and metastasis-related factor C-X-C motif chemokine ligand 12 (CXCL12) expression. In addition, shGREM1 combined with VEGF inhibitor BAW2881 displayed more effective antiangiogenesis to inhibit the tube formation of HUVEC. Hence, these experiments demonstrated that GREM1 is involved in CRC development and procession and provide a new idea for CRC diagnosis, resistance therapy, and prognosis.

Omega 3 polyunsaturated fatty acids inhibit cell proliferation by regulating cell cycle in fad3b transgenic mouse embryonic stem cells

Background

The consumption of omega 3 polyunsaturated fatty acids (PUFAs) is important for human health and is closely associated with cell proliferation and differentiation. This study aimed to investigate the influence of omega 3 PUFAs on embryonic stem cell (ESC) proliferation and explore potential mechanisms that mediate these effects.

Methods

In this study, we isolated ESCs from fad3b-expressing transgenic mice. We detected the fatty-acid composition of ESCs using gas chromatography-mass spectroscopy, analyzed cell-cycle phases using flow cytometry, and detected gene expression using real-time polymerase chain reaction (PCR) and western blots.

Results

The amount of omega 3 PUFAs significantly increased in fad3b versus control ESCs. However, the growth of fad3b ESCs was slower than that of control cells, and most fad3b ESCs were in a prolonged G0/G1 phase after being passaged for 18 h. Therefore, we hypothesized that fad3b expression inhibited the cell cycle in ESCs by increasing the expression of P21, which then decreased the expression of cyclin-dependent kinase 4 (Cdk4). We found that pretreatment of fad3b ESCs with PD0325901, a P21 inhibitor, clearly attenuated the inhibitory effects of P21 on Cdk4, and resumed the cell cycle.

Conclusions

Expression of the fad3b gene in ESCs increased the omega 3 PUFA content, which inhibited cell proliferation by prolonging the G1 phase but did not arrest the G0-to-G1 or G1-to-S transitions. The prolonged G1 phase in fad3b ESCs was probably induced by downregulation of Cdk4 expression via p21 upregulation. These results suggest that accumulation of omega 3 PUFAs in vivo may beneficially affect ESC differentiation and that fad3b ESCs may be a useful tool for investigating related mechanisms.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0862-x) contains supplementary material, which is available to authorized users.

Calotropin regulates the apoptosis of non‑small cell cancer by regulating the cytotoxic T‑lymphocyte associated antigen 4‑mediated TGF‑β/ERK signaling pathway

Non-small-cell lung cancer (NSCLC) is one of the most common malignancies that is responsible for a high level of cancer-associated mortalities worldwide. Previous evidence has shown that Calotropin is an upstream activator of protein kinase B, which can further inhibit the growth and promote the apoptosis of NSCLC cells. In the present study, the efficacy of Calotropin on growth, aggressiveness and apoptosis of NSCLC cells was investigated, as well as the potential underlying mechanism. The results demonstrated that Calotropin inhibited H358 cell growth, migration and invasion. Flow cytometry assay showed that Calotropin promoted the apoptosis of H358 cells in vitro. Western blot analysis demonstrated that Calotropin inhibited fibronectin (FN), Vimentin (VIM) and E-cadherin (Eca) protein expression levels in H358 cells in vitro. In addition, Calotropin treatment upregulated pro-apoptosis gene expression, including caspase-3, caspase-8 and apoptotic protease activating factor-1, and downregulated anti-apoptosis gene expression, including P53, B-cell lymphoma (Bcl) 2 and Bcl-2-like protein 2 in H358 cells. The results also revealed that the expression levels of cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) were decreased by Calotropin treatment in H358 cells. Analyses of the underlying mechanism indicated that Calotropin inhibited transforming growth factor-β (TGF-β) and extracellular signal-regulated kinase (ERK) expression. Overexpression of CTLA-4 inhibited Calotropin-mediated downregulation of TGF-β and ERK expression in H358 cells. In vivo assay revealed that Calotropin administration significantly inhibited tumor growth and prolonged animal survival over the 120-day observation period. Immunohistochemistry demonstrated that the number of apoptotic cells increased and the expression levels of CTLA-4 were decreased in the Calotropin-treated tumor group when compared with control. In addition, the expression levels of TGF-β and ERK were downregulated in the Calotropin-treated tumor group compared with control. In conclusion, the results of the present study indicated that Calotropin administration regulated NSCLC apoptosis by downregulating the CTLA-4-mediated TGF-β/ERK signaling pathway, suggesting that Calotropin may be a potential anti-cancer agent for the treatment of NSCLC.

TGFβ and IGF1R signaling activates protein kinase A through differential regulation of ezrin phosphorylation in colon cancer cells

Aberrant cell survival plays a critical role in cancer progression and metastasis. We have previously shown that ezrin, a cAMP-dependent protein kinase A-anchoring protein (AKAP), is up-regulated in colorectal cancer (CRC) liver metastasis. Phosphorylation of ezrin at Thr-567 activates ezrin and plays an important role in CRC cell survival associated with XIAP and survivin up-regulation. In this study, we demonstrate that in FET and GEO colon cancer cells, knockdown of ezrin expression or inhibition of ezrin phosphorylation at Thr-567 increases apoptosis through protein kinase A (PKA) activation in a cAMP-independent manner. Transforming growth factor (TGF) β signaling inhibits ezrin phosphorylation in a Smad3-dependent and Smad2-independent manner and regulates pro-apoptotic function through ezrin-mediated PKA activation. On the other hand, ezrin phosphorylation at Thr-567 by insulin-like growth factor 1 receptor (IGF1R) signaling leads to cAMP-dependent PKA activation and enhances cell survival. Further studies indicate that phosphorylated ezrin forms a complex with PKA RII, and dephosphorylated ezrin dissociates from the complex and facilitates the association of PKA RII with AKAP149, both of which activate PKA yet lead to either cell survival or apoptosis. Thus, our studies reveal a novel mechanism of differential PKA activation mediated by TGFβ and IGF1R signaling through regulation of ezrin phosphorylation in CRC, resulting in different cell fates. This is of significance because TGFβ and IGF1R signaling pathways are well-characterized tumor suppressor and oncogenic pathways, respectively, with important roles in CRC tumorigenesis and metastasis. Our studies indicate that they cross-talk and antagonize each other's function through regulation of ezrin activation. Therefore, ezrin may be a potential therapeutic target in CRC.

Functional expression of BMP7 receptors in oral epithelial cells. Interleukin-17F production in response to BMP7

BACKGROUND

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-β (TGF-β) superfamily. Recently, BMP7 has been demonstrated to be produced by salivary glands and contribute to embryonic branching in mice. The BMP7 in saliva is thought to be delivered to the oral cavity and is expected to contact with stratified squamous epithelial cells which line the surface of oral mucosa. In this study, we attempted to investigate the effects of BMP7 on oral epithelial cells.

METHODS

The expression of BMP receptors was examined by reverse transcriptase-polymerase chain reaction (RT-PCR). OSCCs were stimulated with human recombinant BMP7 (hrBMP7) and the phosphorylation status of Smad1/5/8 was examined by western blotting. For microarray analysis, Ca9-22 cells were stimulated with 100 ng/mL of hrBMP7 and total RNA was extracted and subjected to real-time PCR. The 5'-untranslated region (5'-UTR) of IL-17 F gene was cloned to pGL4-basic vector and used for luciferase assay. Ca9-22 cells were pre-incubated with DM3189, a specific inhibitor of Smad1/5/8, for inhibition assay.

RESULTS

All isoforms of type I and type II BMP receptors were expressed in both Ca9-22 and HSC3 cells and BMP7 stimulation resulted in the phosphorylation of Smad1/5/8 in both cell lines. The microarray analysis revealed the induction of interleukin-17 F (IL-17 F), netrin G2 (NTNG2) and hyaluronan synthase 1 (HAS1). Luciferase assay using the 5'-UTR of the IL-17 F gene revealed transcriptional regulation. Induced IL-17 F production was further confirmed at the protein level by ELISA. Smad1/5/8 inhibitor pretreatment decreased IL-17 F expression levels in the cells.

Bone morphogenetic protein-2 and tumor growth: Diverse effects and possibilities for therapy

Concern regarding safety with respect to the clinical use of human bone morphogenetic protein-2 (BMP-2) has become an increasingly controversial topic. The role of BMP-2 in carcinogenesis is of particular concern. Although there have been many studies of this topic, the results have been contradictory and confusing. We conducted a systematic review of articles that are relevant to the relationship or effect of BMP-2 on all types of tumors and a total of 97 articles were included. Studies reported in these articles were classified into three major types: "expression studies", "in vitro studies", and "in vivo studies". An obvious pattern was that those works that hypothesize an inhibitory effect for BMP-2 most often examined only the proliferative properties of the tumor cells. This subset of studies also contained an extraordinary number of contradictory findings which made drawing a reliable general conclusion impossible. In general, we support a pro-tumorigenesis role for BMP-2 based on the data from these in vitro cell studies and in vivo animal studies, however, more clinical studies should be carried out to help make a firm conclusion.

Bone morphogenetic protein 7 is associated with the nodal invasion of colon cancer

Environmental and genetic factors interact in the process and treatment of colon cancer, although the underlying mechanisms remain elusive. The aim of the study was to examine the role of whether bone morphogenetic protein 7 (BMP7) is involved in the progression of colon cancer under local intratumoral infiltration lymphocytes. A total of 46 cases of pathologically confirmed specimens were obtained from patients with nodal invasion of colon cancer. The patients were subdivided into three groups based on the nodal invasion stages (N0, N1 and N2). Eleven cases without nodal invasion of colon cancer served as the control group (N0). The phenotype of CD45⁺, CD4⁺, CD8⁺, CD25⁺ and CD56⁺ cells and the expression of BMP7 were confirmed by immunofluorescence. The association between BMP7 expression and CD45⁺/CD4⁺CD25⁺/CD8⁺ cells infiltration was analyzed. The density of CD4⁺CD25⁺ T cells within the tumor was associated with nodal invasion in patients with colon cancer. More importantly, the expression of BMP7 was observed in the majority of the cancer tissues. The co-expression pattern of BMP7 in colon cancer cells and intratumor CD4⁺CD25⁺ T cells was associated with nodal invasion of colon cancer. In conclusion, the results have shown that the co-expression of BMP7 is inversely associated with the infiltration of CD4⁺CD25⁺ T cells of colon cancer. The results suggest the combination of adaptive immunotherapy and biological drugs impact the treatment strategy for colon cancer in distinct clinical settings.

Association Between BMP-2 and Carcinogenicity

STUDY DESIGN

Literature review.

OBJECTIVE

To evaluate the association between recombinant human bone morphogenetic protein-2 (rhBMP-2) and malignancy.

SUMMARY OF BACKGROUND DATA

The use of rhBMP-2 in spine surgery has been the topic of much debate as studies assessing the association between rhBMP-2 and malignancy have come to conflicting conclusions.

METHODS

A systematic review of the literature was performed using the PubMed-National Library of Medicine/National Institute of Health databases. Only non-clinical studies directly addressing BMP-2 and cancer were included. Articles were categorized by study type (animal, in vitro cell line/human/animal), primary malignancy, cancer attributes, and whether BMP-2 was pro-malignancy or not.

RESULTS

A total of 4,131 articles were reviewed. Of those, 515 articles made reference to both BMP-2 and cancer, 99 of which were found to directly examine the role of BMP-2 in cancer. Seventy-five studies were in vitro and 24 were animal studies. Forty-three studies concluded that BMP-2 enhanced cancer function, whereas 18 studies found that BMP-2 suppressed malignancy. Thirty-six studies did not examine whether BMP-2 enhanced or suppressed cancer function. Fifteen studies demonstrated BMP-2 dose dependence (9 enhancement, 6 suppression) and one study demonstrated no dose dependence. Nine studies demonstrated BMP-2 time dependence (6 enhancement, 3 suppression). However, no study demonstrated that BMP-2 caused cancer de novo.

CONCLUSION

Currently, conflicting data exist with regard to the effect of exogenous BMP-2 on cancer. The majority of studies addressed the role of BMP-2 in prostate (17%), breast (17%), and lung (15%) cancers. Most were in vitro studies (75%) and examined cancer invasiveness and metastatic potential (37%). Of 99 studies, there was no demonstration of BMP-2 causing cancer de novo. However, 43% of studies suggested that BMP-2 enhances tumor function, motivating more definitive research on the topic that also includes clinically meaningful dose- and time-dependence.

LEVEL OF EVIDENCE

2.

Bone morphogenetic protein antagonist gremlin-1 regulates colon cancer progression

Bone morphogenetic proteins (BMP) are phylogenetically conserved signaling molecules of the transforming growth factor-beta (TGF-beta) superfamily of proteins, involved in developmental and (patho)physiological processes, including cancer. BMP signaling has been regarded as tumor-suppressive in colorectal cancer (CRC) by reducing cancer cell proliferation and invasion, and by impairing epithelial-to-mesenchymal transition (EMT). Here, we mined existing proteomic repositories to explore the expression of BMPs in CRC. We found that the BMP antagonist gremlin-1 (GREM1) is secreted from heterotypic tumor-host cell interactions. We then sought to investigate whether GREM1 is contextually and mechanistically associated with EMT in CRC. Using immunohistochemistry, we showed that GREM1-expressing stromal cells harbor prominent features of myofibroblasts (i.e., cancer-associated fibroblasts), such as expression of α-smooth muscle actin and laminin-beta-1, and were in contextual proximity to invasion fronts with loss of the tight junction protein occludin and parallel nuclear accumulation of β-catenin, two prominent EMT hallmarks. Furthermore, in vitro assays demonstrated that GREM1-dependent suppression of BMP signaling results in EMT induction, characterized by cadherin switching (loss of E-cadherin-upregulation of N-cadherin) and overexpression of Snail. Collectively, our data support that GREM1 promotes the loss of cancer cell differentiation at the cancer invasion front, a mechanism that may facilitate tumor progression.

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.

Glioma cancer stem cells secrete Gremlin1 to promote their maintenance within the tumor hierarchy

In glioblastomas, cancer stem cells (CSCs) reside in functional niches that provide essential cues to maintain the cellular hierarchy. Bone morphogenetic proteins (BMPs) are proposed as anti-CSC therapies to induce differentiation, but, paradoxically, tumors express high levels of BMPs. Yan et al. demonstrate that the BMP antagonist Gremlin1 is specifically expressed by CSCs as protection from endogenous BMPs. Gremlin1-overexpressing cells display increased growth and tumor formation, while targeting Gremlin1 in CSCs impairs growth and self-renewal associated with inhibition of p21WAF1/CIP1, a key CSC signaling node.

Glioblastomas are the most prevalent and lethal primary brain tumor and are comprised of hierarchies with self-renewing cancer stem cells (CSCs) at the apex. Like neural stem cells (NSCs), CSCs reside in functional niches that provide essential cues to maintain the cellular hierarchy. Bone morphogenetic proteins (BMPs) instruct NSCs to adopt an astrocyte fate and are proposed as anti-CSC therapies to induce differentiation, but, paradoxically, tumors express high levels of BMPs. Here we demonstrate that the BMP antagonist Gremlin1 is specifically expressed by CSCs as protection from endogenous BMPs. Gremlin1 colocalizes with CSCs in vitro and in vivo. Furthermore, Gremlin1 blocks prodifferentiation effects of BMPs, and overexpression of Gremlin1 in non-CSCs decreases their endogenous BMP signaling to promote stem-like features. Consequently, Gremlin1-overexpressing cells display increased growth and tumor formation abilities. Targeting Gremlin1 in CSCs results in impaired growth and self-renewal. Transcriptional profiling demonstrated that Gremlin1 effects were associated with inhibition of p21^WAF1/CIP1, a key CSC signaling node. This study establishes CSC-derived Gremlin1 as a driving force in maintaining glioblastoma tumor proliferation and glioblastoma hierarchies through the modulation of endogenous prodifferentiation signals.

ZNF313 is a novel cell cycle activator with an E3 ligase activity inhibiting cellular senescence by destabilizing p21(WAF1.)

ZNF313 encoding a zinc-binding protein is located at chromosome 20q13.13, which exhibits a frequent genomic amplification in multiple human cancers. However, the biological function of ZNF313 remains largely undefined. Here we report that ZNF313 is an ubiquitin E3 ligase that has a critical role in the regulation of cell cycle progression, differentiation and senescence. In this study, ZNF313 is initially identified as a XIAP-associated factor 1 (XAF1)-interacting protein, which upregulates the stability and proapoptotic effect of XAF1. Intriguingly, we found that ZNF313 activates cell cycle progression and suppresses cellular senescence through the RING domain-mediated degradation of p21(WAF1). ZNF313 ubiquitinates p21(WAF1) and also destabilizes p27(KIP1) and p57(KIP2), three members of the CDK-interacting protein (CIP)/kinase inhibitor protein (KIP) family of cyclin-dependent kinase inhibitors, whereas it does not affect the stability of the inhibitor of CDK (INK4) family members, such as p16(INK4A) and p15(INK4B). ZNF313 expression is tightly controlled during the cell cycle and its elevation at the late G1 phase is crucial for the G1-to-S phase transition. ZNF313 is induced by mitogenic growth factors and its blockade profoundly delays cell cycle progression and accelerates p21(WAF1)-mediated senescence. Both replicative and stress-induced senescence are accompanied with ZNF313 reduction. ZNF313 is downregulated during cellular differentiation process in vitro and in vivo, while it is commonly upregulated in many types of cancer cells. ZNF313 shows both the nuclear and cytoplasmic localization in epithelial cells of normal tissues, but exhibits an intense cytoplasmic distribution in carcinoma cells of tumor tissues. Collectively, ZNF313 is a novel E3 ligase for p21(WAF1), whose alteration might be implicated in the pathogenesis of several human diseases, including cancers.

Enrichment map profiling of the cancer invasion front suggests regulation of colorectal cancer progression by the bone morphogenetic protein antagonist, gremlin-1

The cancer invasion front (CIF), a spatially-recognized area due to the frequent presence of peritumoral desmoplastic reaction, represents a cancer site where many hallmarks of cancer metastasis occur. It is now strongly suggested that the desmoplastic microenvironment holds crucial information for determining tumor development and progression. Despite extensive research on tumor-host cell interactions at CIFs, the exact paracrine molecular network that is hardwired into the proteome of the stromal and cancer subpopulations remains partially understood. Here, we interrogated the signaling pathways and the molecular functional signatures across the proteome of a desmoplastic coculture model system of colorectal cancer progression. We discovered a group of bone morphogenetic protein (BMP) antagonists that coordinates major biological programs in CIFs, including cell proliferation, invasion, migration and differentiation processes. Using a mathematical model of cancer cell progression, coupled to in vitro cell migration assays, we demonstrated that the prominent BMP antagonist gremlin-1 (GREM1) may trigger motility of cancer cell cohorts. Our data collectively demonstrate that the desmoplastic CIFs deploy a microenvironmental signature, based on BMP antagonism, in order to regulate the motogenic fates of cancer cell cohorts invading the adjacent stroma.

Bone morphogenetic protein type I receptor antagonists decrease growth and induce cell death of lung cancer cell lines

Bone morphogenetic proteins (BMPs) are highly conserved morphogens that are essential for normal development. BMP-2 is highly expressed in the majority of non-small cell lung carcinomas (NSCLC) but not in normal lung tissue or benign lung tumors. The effects of the BMP signaling cascade on the growth and survival of cancer cells is poorly understood. We show that BMP signaling is basally active in lung cancer cell lines, which can be effectively inhibited with selective antagonists of the BMP type I receptors. Lung cancer cell lines express alk2, alk3, and alk6 and inhibition of a single BMP receptor was not sufficient to decrease signaling. Inhibition of more than one type I receptor was required to decrease BMP signaling in lung cancer cell lines. BMP receptor antagonists and silencing of BMP type I receptors with siRNA induced cell death, inhibited cell growth, and caused a significant decrease in the expression of inhibitor of differentiation (Id1, Id2, and Id3) family members, which are known to regulate cell growth and survival in many types of cancers. BMP receptor antagonists also decreased clonogenic cell growth. Knockdown of Id3 significantly decreased cell growth and induced cell death of lung cancer cells. H1299 cells stably overexpressing Id3 were resistant to growth suppression and induction of cell death induced by the BMP antagonist DMH2. These studies suggest that BMP signaling promotes cell growth and survival of lung cancer cells, which is mediated through its regulation of Id family members. Selective antagonists of the BMP type I receptors represents a potential means to pharmacologically treat NSCLC and other carcinomas with an activated BMP signaling cascade.

BMP2 induces osteoblast apoptosis in a maturation state and noggin-dependent manner

Large doses of bone morphogenetic protein 2 (BMP2) are used clinically to induce bone formation in challenging bone defects. However, complications after treatment include swelling, ectopic bone formation, and adjacent bone resorption. While BMP2 can be effective, it is important to characterize the mechanism of the deleterious effects to optimize its use. The aim of this study was to determine the effect of BMP2 on apoptosis in osteoblast lineage cells and to determine the role of the BMP inhibitor Noggin in this process. Human mesenchymal stem cells (MSCs), immature osteoblast-like MG63 cells, and mature normal human osteoblasts (NHOst) were treated with BMP2. A model system of increased endogenous BMP signaling was created by silencing Noggin (shNOG-MG63). Finally, the BMP pathway regulating apoptosis in NHOst was examined using BMP signaling inhibitors (5Z-7-oxozeaenol, dorsomorphin, H-8). Apoptosis was characterized by caspase-3, BAX/BCL2, p53, and DNA fragmentation. BMP2 induced apoptosis in a cell-type dependent manner. While the effect was minor in MSCs, MG63 cells had modest increases and NHOst cells had robust increases apoptosis after BMP2 treatment. Apoptosis was significantly higher in shNOG-MG63 than MG63 cells. 5Z-7-oxozeaenol and dorsomorphin eliminated the BMP2-induced increase in DNA fragmentation in NHOst, suggesting roles for TAB/TAK1 and Smad signaling. These results indicate that the apoptotic effect of BMP2 is dependent on cell maturation state, inducing apoptosis in committed osteoblasts through Smad and TAB/TAK1 signaling, and is regulated by Noggin. Dose and delivery must be optimized in therapeutic applications of BMP2 to minimize complications.

Polymorphisms in bone morphogenetic protein 3 and the risk of papillary thyroid cancer

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor beta (TGFβ) superfamily with well-described functions in bone formation. Although disrupted BMP signaling in tumor development has been investigated, a genetic association for BMP3 in papillary thyroid cancer (PTC) has remained largely unexplored. In this study, we investigated whether BMP3 single nucleotide polymorphisms (SNPs) are associated with the development of PTC and its clinicopathological features. A total of 103 PTC patients and 324 control subjects were enrolled. One promoter SNP (rs13138132; -1919C/A) and one missense mutation (rs3733549; Arg192Gln) in BMP3 were genotyped by direct sequencing. SNPStats, SNPAnalyzer, Helixtree and Haploview version 4.2 were used to evaluate the genetic data. Multiple logistic regression models were used to calculate odds ratios (ORs), 95% confidence intervals (CIs) and P-values. The missense SNP (rs3733549) was weakly associated with the development of PTC in a codominant model (AA vs. GG; P=0.017) and a recessive model (AA vs. GG/GA; P=0.023). Additionally, in an analysis according to clinicopathological features, rs13138132 was significantly associated with extra-thyroidal invasion in a codominant model (CA vs. CC; P=0.006) and a dominant model (CA/AA vs. CC; P=0.0023). We also identified that the frequency of the A allele in the promoter SNP (rs13138132) was increased in PTC patients with extrathyroidal invasion (P=0.004). Our data suggest that rs3733549 in BMP3 is associated with the development of PTC and that the A allele of rs13138932 in BMP3 is a risk factor for extrathyroidal invasion.

Prognostic significance of BMP7 as an oncogene in hepatocellular carcinoma

This study aims to evaluate the association between BMP7 tissue expression and patient prognosis in hepatocellular carcinoma (HCC). The expression of BMP7 mRNA in HCC was characterized using real-time PCR and 30 pairs of fresh frozen HCC tissues and corresponding noncancerous tissues. BMP7 protein expression in HCC was confirmed using immunohistochemistry on a tissue microarray chip. Finally, BMP7 expression was correlated with conventional clinicopathological features of HCC and patient outcome. The expression of BMP7 mRNA and protein in HCC cells was much higher than in normal hepatic cells. Our results showed that the high expression of BMP7 in HCC was related to tumor size (p < 0.001), histological differentiation (p = 0.041), serum AFP (p = 0.007), and tumor stage (p < 0.001). Kaplan-Meier survival analysis showed that a high-expression level of BMP7 resulted in a significantly poor prognosis of HCC patients. Multivariate analysis revealed that BMP7 expression level was an independent prognostic parameter for the overall survival rate of HCC patients. These findings provide evidence that a high-expression level of BMP7 serves as a biomarker for poor prognosis for HCC. Thus, we speculate that BMP7 may be a potential target of antiangiogenic therapy for HCC.

Galectin-3 regulates p21 stability in human prostate cancer cells

Galectin-3 (Gal-3) is a multifunctional protein involved in cancer through regulation of cell adhesion, cell growth, apoptosis and metastasis, while p21 (Cip1/WAF1) is a negative regulator of the cell cycle, involved in apoptosis, transcription, DNA repair and metastasis. The results presented here demonstrate for the first time that the level of Gal-3 protein is associated with the level of p21 protein expression in human prostate cancer cells and the effects of Gal-3 on cell growth and apoptosis were reversed by modulating p21 expression level. Furthermore, Gal-3 regulates p21 expression at the post-translational level by stabilizing p21 protein via the carbohydrate-recognition domain. This is the first report suggesting a molecular function not yet described for Gal-3 as the regulator of p21 protein stability. This study provides a unique insight into the relationship of these two molecules during prostate cancer progression, and may provide a novel therapeutic target.

Developmental pathways in colon cancer: crosstalk between WNT, BMP, Hedgehog and Notch

A hallmark of cancer is reactivation/alteration of pathways that control cellular differentiation during developmental processes. Evidence indicates that WNT, Notch, BMP and Hedgehog pathways have a role in normal epithelial cell differentiation, and that alterations in these pathways accompany establishment of the tumorigenic state. Interestingly, there is recent evidence that these pathways are intertwined at the molecular level, and these nodes of intersection may provide opportunities for effective targeted therapies. This review will highlight the role of the WNT, Notch, BMP and Hedgehog pathways in colon cancer.

Major signaling pathways in intestinal stem cells

BACKGROUND

The discovery of markers to identify the intestinal stem cell population and the generation of powerful transgenic mouse models to study stem cell physiology have led to seminal discoveries in stem cell biology.

SCOPE OF REVIEW

In this review we give an overview of the current knowledge in the field of intestinal stem cells (ISCs) highlighting the most recent progress on markers defining the ISC population and pathways governing intestinal stem cell maintenance and differentiation. Furthermore we review their interaction with other stem cell related pathways. Finally we give an overview of alteration of these pathways in human inflammatory gastrointestinal diseases.

MAJOR CONCLUSIONS

We highlight the complex network of interactions occurring among different pathways and put in perspective the many layers of regulation that occur in maintaining the intestinal homeostasis.

GENERAL SIGNIFICANCE

Understanding the involvement of ISCs in inflammatory diseases can potentially lead to new therapeutic approaches to treat inflammatory GI pathologies such as IBD and celiac disease and could reveal the molecular mechanisms leading to the pathogenesis of dysplasia and cancer in inflammatory chronic conditions. This article is part of a Special Issue entitled Biochemistry of Stem Cells.

Effects of activin and TGFβ on p21 in colon cancer

Activin and TGFβ share SMAD signaling and colon cancers can inactivate either pathway alone or simultaneously. The differential effects of activin and TGFβ signaling in colon cancer have not been previously dissected. A key downstream target of TGFβ signaling is the cdk2 inhibitor p21 (p21^cip1/waf1). Here, we evaluate activin-specific effects on p21 regulation and resulting functions. We find that TGFβ is a more potent inducer of growth suppression, while activin is a more potent inducer of apoptosis. Further, growth suppression and apoptosis by both ligands are dependent on SMAD4. However, activin downregulates p21 protein in a SMAD4-independent fashion in conjunction with increased ubiquitination and proteasomal degradation to enhance migration, while TGFβ upregulates p21 in a SMAD4-dependent fashion to affect growth arrest. Activin-induced growth suppression and cell death are dependent on p21, while activin-induced migration is counteracted by p21. Further, primary colon cancers show differential p21 expression consistent with their ACVR2/TGFBR2 receptor status. In summary, we report p21 as a differentially affected activin/TGFβ target and mediator of ligand-specific functions in colon cancer, which may be exploited for future risk stratification and therapeutic intervention.

Oncogenic KRAS regulates BMP4 expression in colon cancer cell lines

Activating mutations in the KRAS oncogene are common in colorectal cancer. However, the complete spectrum of KRAS targets that mediate its tumorigenic effect has not yet been fully delineated. We identified bone morphogenetic protein 4 (Bmp4), a transforming growth factor-β family member that regulates development and tissue homeostasis, as a new target of KRAS. In SW480, Hela, and 293 cells, oncogenic KRAS(V12) downregulated BMP4 RNA levels, a BMP4 promoter luciferase construct, and Bmp4 protein levels. The MEK inhibitor PD98059 but not the phosphatidylinositol 3-kinase inhibitor LY294002 blocked this downregulation of BMP4. To identify the region of the BMP4 promoter that mediated this regulation by KRAS, serial 5'-deletions of the promoter were generated. An inhibitory region was identified between -3,285 and -3,258 bp in the Bmp4 promoter. In summary, oncogenic KRAS can downregulate Bmp4 through a transcriptional pathway that depends on ERK. These findings point to a unique link between two pathways that are frequently altered in colon cancer.

Clinicopathological significance of BMP7 expression in esophageal squamous cell carcinoma

Background

Bone morphogenetic proteins (BMPs) are secreted signaling molecules belonging to the transforming growth factor-β (TGF-β) superfamily of growth factors. Recent studies have shown that the influence of the expression of BMP7 was altered in several tumors. The purpose of the current study was to examine the expression of BMP7 in esophageal squamous cell carcinoma and to clarify the clinical impact of BMP7 expression in esophageal squamous cell carcinoma (ESCC).

Methods

A total of 180 patients with ESCC who underwent surgical resection from 1991 to 2004 were eligible for this study. The expression of BMP7 in esophageal tumor tissues was examined immunohistochemically.

Results

BMP7 expression was found in the cytoplasm of cancer cells. BMP7 positivity was observed in 61.7% of tumors. The BMP7-positive group had deeper progression, more advanced stages, and greater venous invasion than those without BMP7 expression (p < 0.001, p < 0.005, and p < 0.0005, respectively). In addition, expression of BMP7 correlated with poorer prognosis (p < 0.0005). Multivariate analysis showed that BMP7 expression status was an independent prognostic factor (p < 0.05).

Conclusions

Patients with expression of BMP7 in ESCC had high malignant potential. BMP7 could be a useful prognostic marker for patients with ESCC.

Selective suicide gene therapy of colon cancer exploiting the urokinase plasminogen activator receptor promoter

Colon cancer is the third and fourth most prevalent cancer among Iranian men and women, respectively. Suicide gene therapy is one of the alternative therapeutic modalities for cancer. The application of specific promoters for therapeutic genes should decrease the adverse effects of this modality. The combined aims of this study were to design a specific suicide gene therapy construct for colon cancer and study its effect in distinct representatives of transformed and nontransformed cells. The KRAS oncogene signaling pathway is one of the most important signaling pathways activated in colon cancer; therefore, we inserted the urokinase plasminogen activator receptor (uPAR; PLAUR gene) promoter as one of the upregulated promoters by this pathway upstream of a suicide gene (thymidine kinase [TK]) and a reporter gene (beta-galactosidase, beta-gal [LacZ]). This promoter is a natural combination of different motifs responsive to the RAS signaling pathway, such as the transcription factors AP1 (FOS/JUN), SP1, SP3, and AP2alpha, and nuclear factor kappa B (NFkappaB). The reporter plasmid under the control of the uPAR promoter (PUCUPARLacZ) had the ability to express beta-gal in colon cancer cells (human colon adenocarcinoma [SW480] and human colorectal carcinoma [HCT116] cell lines), while it could not express beta-gal in nontransformed human umbilical vein endothelial cells (HUVEC) and normal colon cells. After confirming the ability of pUCUPARTK (suicide plasmid) to express TK in SW480 and HCT116 cells by real-time PCR, cytotoxicity assays showed that pUCUPARTK decreased the viability of these cells in the presence of ganciclovir 20 and 40 microg/mL (and higher), respectively. Although M30 CytoDEATH antibody could not detect a significant rate of apoptosis induced by ganciclovir in pUCUPARTK-transfected HCT116 cells, the percentage of stained cells was marked in comparison with untreated cells. While this antibody could detect apoptosis in HCT116 cell line transfected with positive control plasmid, it could not detect apoptosis in SW480 cells transfected with the same positive control. This discrepancy could be attributed to the different mechanisms of TK/ganciclovir-induced apoptosis in tumor protein p53 (TP53)-expressing (HCT116) and -deficient (SW480) cells. Annexin-propidium iodide staining could detect apoptosis in treated, pUCUPARTK-transfected SW480 and HCT116 cells. This study showed that the uPAR promoter can be considered as a suitable candidate for specific suicide gene therapy of colon cancer and probably other cancers in which the RAS signaling pathway is involved in their carcinogenesis process.

Administration of human recombinant bone morphogenetic protein-2 for spine fusion may be associated with transient postoperative renal insufficiency

STUDY DESIGN

Retrospective chart review.

OBJECTIVE

We reviewed the peri- and postoperative outcomes of our patients who had undergone lumbar and lumbosacral fusion both with and without recombinant human bone morphogenetic protein (rhBMP) over a period of 8 years to assess the frequency of complications and new diagnoses associated with the use of rhBMP2.

SUMMARY OF BACKGROUND DATA

Administration of rhBMP2 for augmentation of lumbar and lumbosacral spinal fusion has not previously been associated with systemic complications.

METHODS

A review of all patients undergoing lumbar and lumbosacral fusion over an 8-year period was performed to determine the frequency of postoperative complications and new diagnoses. Comparisons in complication frequency and new postoperative diagnoses between patients receiving rhBMP2 versus only allo- or autograft were made. Statistical methodology was applied to determine significance. RESULTS.: None of the 105 patients not receiving rhBMP2 and 3 of 24 patients receiving rhBMP2 had blood urea nitrogens and creatinines that more than doubled and reached values >30 and 1.5 mg/dL, respectively, after surgery (P = 0.006). Renal parameters returned to baseline within 45 days of surgery. Two of the 3 patients with postoperative renal insufficiency had been administered 16 mL (24 mg) of rhBMP2, whereas all other patients receiving rhBMP2 had received 8 mL (12 mg). Both of these patients also had supraventricular tachycardia, fever, and mental status changes after surgery. We recorded no significant increase in the incidence of new endocrinologic, autoimmune, neurologic, or neoplastic disorders associated with the use of rhBMP2 in our small patient population.

CONCLUSION

A small subset of patients may develop transient renal insufficiency after rhBMP2 to augment spinal fusion. Higher doses of rhBMP2 may possibly increase the risk of developing renal insufficiency in particular patients; however, additional study is needed before all the risk factors are understood.

Bone morphogenetic protein 4 and its receptors are expressed in the leptomeninges and meningiomas and signal via the Smad pathway

The roles of bone morphogenetic proteins (BMPs) and their receptors (BMPRs) in meningioma biology are not known. In this study, frozen tissues from 26 World Health Organization Grades I to III meningiomas were analyzed by Western blot for BMP-2/4, BMPR IA, and BMPR II, and activation of downstream p-Smad1, p38 mitogen-activated protein kinase (MAPK), and p44/42 MAPK signaling molecules. Sections from 20 normal leptomeninges, 2 arachnoid cysts, and 51 meningiomas were analyzed for BMP-4 and p44/42 MAPK by immunohistochemistry. Primary meningioma cultures from 11 meningiomas were treated with BMP-4 and evaluated for cell proliferation and signaling pathway activation. Conditioned media from 7 cultures were analyzed for BMP-4 by ELISA. Bone morphogenetic protein 4 was variably detected in adult leptomeninges but was detected in 89% or 84% of Grade I meningiomas and in 60% of Grade II meningiomas by Western blot and immunohistochemistry, respectively. Bone morphogenetic protein receptors IA and II were detected in leptomeninges and in all meningiomas studied, and activated Smad1 was detected in all meningiomas studied. Bone morphogenetic protein 4 stimulated meningioma cell proliferation and phosphorylation/activation of Smad1 but not p38 MAPK or p44/42 MAPK in vitro, and it was detected in conditioned media from 4 of 7 cultures. These findings suggest that BMP-4 and BMPRs may play autocrine/paracrine roles and interact with other transforming growth factor-beta superfamily members in regulating meningioma growth and differentiation.

Endothelial cells and pulmonary arterial hypertension: apoptosis, proliferation, interaction and transdifferentiation

Severe pulmonary arterial hypertension, whether idiopathic or secondary, is characterized by structural alterations of microscopically small pulmonary arterioles. The vascular lesions in this group of pulmonary hypertensive diseases show actively proliferating endothelial cells without evidence of apoptosis. In this article, we review pathogenetic concepts of severe pulmonary arterial hypertension and explain the term "complex vascular lesion ", commonly named "plexiform lesion", with endothelial cell dysfunction, i.e., apoptosis, proliferation, interaction with smooth muscle cells and transdifferentiation.

Antiproliferative and proapoptotic effects of epigallocatechin gallate on human leiomyoma cells

OBJECTIVE

To investigate the effects of epigallocatechin gallate (EGCG), an extract of green tea on cultured human leiomyoma cells (HuLM).

DESIGN

Laboratory study.

SETTING

University hospitals.

PATIENT(S)

Not applicable.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

The HuLM cells were treated with various EGCG concentrations. Cell proliferation was assayed using Hoechst 33258 dye, and apoptosis by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Total RNA was isolated, and gene expression profiling was performed on 84 key genes related to 18 different signal transduction pathways. The protein levels of PCNA, CDK4, BCL2, and BAX were examined by Western blot analysis.

RESULT(S)

The HuLM cells treated with EGCG showed a dose-dependent and time-dependent inhibition of cell proliferation. The TUNEL staining indicated a significant increase in apoptosis in HuLM cells treated with 100 μM of EGCG compared with untreated control. Gene expression profiling indicated that EGCG treatment up-regulated representative genes from the transforming growth factor β (TGF-β) and stress pathways, while inhibiting the survival pathway and NFκB-dependent inflammatory pathway. Western blot analysis confirmed that EGCG at ≥50 μM significantly decreased the expression of PCNA, CDK4, and BCL2 as well as increased the expression of the proapoptotic BAX in a dose-dependent manner.

CONCLUSION(S)

Epigallocatechin gallate inhibits the proliferation of HuLM cells and induces apoptosis. These results suggest that EGCG may be a potential anti-uterine fibroid agent acting through multiple signal transduction pathways.

Less common colorectal cancer predisposition syndromes

A variety of syndromes confer increased risk for intestinal polyp development, outside the more commonly occurring syndromes. Each of these uncommon syndromes predispose to pathognomonic histologies that are uncommonly observed. Accurate diagnosis of these syndromes is contingent on higher-level pathology review, evaluation of signs and symptoms beyond sole consideration of the polyps, and collection of a detailed family history. When a genetic mutation can be identified in the proband, the management of intestinal and extra-intestinal cancer screening can be more appropriately tailored.

p21 in cancer: intricate networks and multiple activities

One of the main engines that drives cellular transformation is the loss of proper control of the mammalian cell cycle. The cyclin-dependent kinase inhibitor p21 (also known as p21WAF1/Cip1) promotes cell cycle arrest in response to many stimuli. It is well positioned to function as both a sensor and an effector of multiple anti-proliferative signals. This Review focuses on recent advances in our understanding of the regulation of p21 and its biological functions with emphasis on its p53-independent tumour suppressor activities and paradoxical tumour-promoting activities, and their implications in cancer.

Endothelial cells and pulmonary arterial hypertension: apoptosis, proliferation, interaction and transdifferentiation

Severe pulmonary arterial hypertension, whether idiopathic or secondary, is characterized by structural alterations of microscopically small pulmonary arterioles. The vascular lesions in this group of pulmonary hypertensive diseases show actively proliferating endothelial cells without evidence of apoptosis. In this article, we review pathogenetic concepts of severe pulmonary arterial hypertension and explain the term "complex vascular lesion ", commonly named "plexiform lesion", with endothelial cell dysfunction, i.e., apoptosis, proliferation, interaction with smooth muscle cells and transdifferentiation.

Bone morphogenetic protein-7 inhibits telomerase activity, telomere maintenance, and cervical tumor growth

Telomere maintenance is critical in tumor cell immortalization. Here, we report that the cytokine bone morphogenetic protein-7 (BMP7) inhibits telomerase activity that is required for telomere maintenance in cervical cancer cells. Application of human recombinant BMP7 triggers a repression of the human telomerase reverse transcriptase (hTERT) gene, shortening of telomeres, and hTERT repression-dependent cervical cancer cell death. Continuous treatment of mouse xenograft tumors with BMP7, or silencing the hTERT gene, results in sustained inhibition of telomerase activity, shortening of telomeres, and tumor growth arrest. Overexpression of hTERT lengthens telomeres and blocks BMP7-induced tumor growth arrest. Thus, BMP7 negatively regulates telomere maintenance, inducing cervical tumor growth arrest by a mechanism of inducing hTERT gene repression.

The cancer paradigm of severe pulmonary arterial hypertension

The plexiform lesions of severe pulmonary arterial hypertension (PAH) are similar in histologic appearance, whether the disease is idiopathic or secondary. Both forms of the disease show actively proliferating endothelial cells without evidence of apoptosis. Here, we discuss the pathobiology of the atypical, angioproliferative endothelial cells in severe PAH. The concept of the endothelial cell as a "quasi-malignant" cell provides a new framework for antiproliferative, antiangiogenic therapy in severe PAH.

Bone morphogenetic protein signalling is required for the anti-mitogenic effect of the proteasome inhibitor MG-132 on colon cancer cells

BACKGROUND AND PURPOSE

Inhibition of proteasome has been emerging as a promising approach in pathway-directed cancer therapy. Bone morphogenetic protein (BMP) signalling, which is known to be regulated by the ubiquitin-proteasome pathway in osteoblasts, plays a crucial role in the suppression of gastrointestinal carcinogenesis. Here we sought to elucidate the anti-mitogenic effect of a proteasome inhibitor in relation to BMP signalling in colon cancer.

EXPERIMENTAL APPROACH

The effects of the proteasome inhibitor MG-132 on proliferation of SW1116 and HT-29 colon cancer cells were determined by [(3)H]-thymidine incorporation and colony-formation assay. The involvement of BMP signalling in the action of MG-132 was elucidated by western blot, real-time PCR, immunofluorescence and RNA interference.

KEY RESULTS

MG-132 significantly suppressed the proliferation of colon cancer SW1116 and HT-29 cells. In this regard, MG-132 activated BMP signalling and this was manifested as an increase in Smad1/5/8 phosphorylation and upregulation of p21(Waf1/Cip1) and p27(Kip1) expression. Knockdown of BMP receptor II abolished Smad1/5/8 phosphorylation, the induction of p21(Waf1/Cip1) and p27(Kip1) and inhibition of cell proliferation induced by MG-132. Further analysis revealed that MG-132 upregulated the expression of BMP1 and BMP2, which are secreted members of the BMP superfamily. Moreover, the expression of Smad6, an intracellular inhibitor of BMP signalling, was suppressed by MG-132.

CONCLUSIONS AND IMPLICATIONS

These findings suggest that inhibition of proteasome suppresses the proliferation of colon cancer cells via activation of BMP signalling. They also demonstrate a novel aspect of proteasome function in the regulation of colon cancer cell proliferation.

BMP suppresses PTEN expression via RAS/ERK signaling

Bone morphogenetic protein (BMP), a member of the transforming growth factor beta family, classically utilizes the SMAD signaling pathway for its growth suppressive effects,and loss of this signaling cascade may accelerate cell growth. In the colon cancer predisposition syndrome Juvenile Polyposis, as well as in the late progression stages of nonsyndromic colorectal cancers, SMAD4 function is typically abrogated. Here, we utilized the SMAD4-null SW480 colon cancer cell line to examine BMPs effect on a potential target gene, PTEN, and how its expression might be regulated. Initial treatment of the SMAD4-null cells with BMP resulted in mild growth suppression, but with prolonged exposure to BMP, the cells become growth stimulatory, which coincided with observed decreases in transcription and translation of PTEN, and with corresponding increases in phospho-AKT protein levels. BMP-induced PTEN suppression was mediated via the RAS/ERK pathway, as pharmacologic inhibition of RAS/ERK, or interference with protein function in the cytosol by DN-RAS prevented BMP-induced growth promotion and changes in PTEN levels, as did treatment with noggin, a BMP ligand inhibitor. Thus, BMP downregulates PTEN via RAS/ERK in a SMAD4-null environment that contributes to cell growth, and constitutes a SMAD4-independent but BMP-responsive signaling pathway.

Bone morphogenetic protein signaling is essential for terminal differentiation of the intestinal secretory cell lineage

BACKGROUND & AIMS

Bone morphogenetic proteins (Bmps) are morphogens known to play key roles in gastrointestinal development and pathology. Most Bmps are produced primarily by the mesenchymal compartment and activate their signaling pathways following a paracrine or autocrine route. The aim of this study was to investigate the role of epithelial Bmp signaling in intestinal morphogenesis and maintenance of adult epithelial cell functions.

METHODS

With the use of tissue-specific gene ablation, we generated mice lacking the Bmp receptor type IA (Bmpr1a) exclusively in the intestinal epithelium. Bmpr1a mutant and control mice were sacrificed for histology, immunofluorescence, Western blot analysis, electron microscopy, and quantitative polymerase chain reaction.

RESULTS

As well as showing increased proliferation and altered intestinal epithelial morphology, Bmpr1a mutant mice revealed that epithelial Bmp signaling is associated with impaired terminal differentiation of cells from the secretory lineage but not with the determination of cell fate. Loss of Bmp signaling exclusively in the epithelial compartment is not sufficient for the initiation of the de novo crypt phenomenon associated with juvenile polyposis syndrome.

CONCLUSIONS

Epithelial Bmp signaling plays an important role in the terminal differentiation of the intestinal secretory cell lineage but not in de novo crypt formation. These findings emphasize the importance of delineating the contribution of the stroma vs the epithelium in gastrointestinal physiology and pathology.