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

Renovation as innovation: Repurposing human antibacterial peptide LL-37 for cancer therapy

In many organisms, antimicrobial peptides (AMPs) display wide activities in innate host defense against microbial pathogens. Mammalian AMPs include the cathelicidin and defensin families. LL37 is the only one member of the cathelicidin family of host defense peptides expressed in humans. Since its discovery, it has become clear that they have pleiotropic effects. In addition to its antibacterial properties, many studies have shown that LL37 is also involved in a wide variety of biological activities, including tissue repair, inflammatory responses, hemotaxis, and chemokine induction. Moreover, recent studies suggest that LL37 exhibits the intricate and contradictory effects in promoting or inhibiting tumor growth. Indeed, an increasing amount of evidence suggests that human LL37 including its fragments and analogs shows anticancer effects on many kinds of cancer cell lines, although LL37 is also involved in cancer progression. Focusing on recent information, in this review, we explore and summarize how LL37 contributes to anticancer effect as well as discuss the strategies to enhance delivery of this peptide and selectivity for cancer cells.

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.

Destabilization of FoxM1 and Inhibition of Topoisomerase I Contribute to Cytotoxicity of Prenylated Xanthones Isolated from Metaxya rostrata

We recently isolated the prenylated xanthones 2-deprenyl-rheediaxanthone B (XB) and 2-deprenyl-7-hydroxy-rheediaxanthone B (OH-XB) from the South American tree fern Metaxya rostrata. This study explores the mechanisms underlying the FoxM1 downregulation induced by both xanthones. Analysis of cell viability and cell-death induction in SW480, HCT116, Caco-2, DLD1 and HT29 exposed to xanthones found cell-loss and activation of caspase in all cell lines except HT29 that do not have high FoxM1 protein levels. To determine the cellular mechanism of xanthone-induced FoxM1 loss, protein stability was analyzed by cycloheximide-chase experiments and showed reduction of FoxM1 stability by XB but not OH-XB. Destabilization was prevented by inhibiting proteasome activity using MG-132 and moderately by the lysosomal inhibitor bafilomycin A1 (baf A1). OH-XB had a stronger impact than XB on FoxM1 mRNA expression by qRT-PCR, and MG-132 positively affected FoxM1 protein level in OH-XB exposed cells even though no decrease in protein abundance had been induced by the xanthone. Additionally, the compound inhibited topoisomerase I causing DNA DSB and early cell cycle arrest. This may reduce FoxM1 gene expression, which may in turn compromise DNA repair and enhance xanthone-induced cell death. With regard to xanthone-induced cell death, MG-132 protected cultures from cell loss induced by both compounds, and baf A1 was active against these XB-induced effects. In summary, both destabilization of FoxM1 protein and topoisomerase I inhibition contribute to both XB and OH-XB cytotoxic activity albeit at different ratios.

The ubiquitin-activating enzyme E1 as a novel therapeutic target for the treatment of restenosis

AIMS

The ubiquitin-activating enzyme E1 (UBA1, E1), the apex of the ubiquitin proteasome pathway, plays a critical role in protein degradation and in pathological processes. Whether UBA1 participates the development of vascular restenosis remains unknown. This study aims to determine the role of UBA1 in the development of balloon injury induced neointimal formation.

METHODS AND RESULTS

Immunostaining and western blots were used to examine the expression of the ubiquitinated protein in the injured carotid after angioplasty. Higher levels of ubiquitinated protein were observed in the neointima. Local delivery of potent chemical UBA1 inhibitor PYR-41 (100 μM) and UBA1 shRNA lentivirus both resulted in a substantial decrease in intimal hyperplasia at 2 weeks and 4 weeks after balloon injury. UBA1 inhibition also reduced Ki-67 positive cell percentage and inflammatory response in the carotid artery wall. We further determined that in vitro UBA1 inhibition was able to ameliorate TNF-α-induced nuclear factor-kappa B (NF-κB) activation by reducing IκB degradation in vascular smooth muscle cells (VSMCs). UBA1 inhibition also led to the accumulation of short-lived proteins such as p53, p21 and c-jun, which may account for the UBA1 inhibition-induced cell cycle delay. Thus, VSMCs proliferation was blocked.

CONCLUSIONS

UBA1 inhibition effectively suppresses neointimal thickening through its anti-proliferative and anti-inflammatory effects. Our results provide further evidence that the ubiquitin-proteasome system is a potential new target for the prevention of vascular restenosis.

Inactivation of bone morphogenetic protein 2 may predict clinical outcome and poor overall survival for renal cell carcinoma through epigenetic pathways

We investigated whether impaired regulation of bone morphogenetic protein-2 (BMP-2) via epigenetic pathways is associated with renal cell carcinoma (RCC) pathogenesis. Expression and CpG methylation of the BMP-2 gene were analyzed using RCC cell lines, and 96 matched RCC and normal renal tissues. We also performed functional analysis using BMP-2 restored RCC cells. A significant association of BMP-2 mRNA expression was also found with advanced tumor stage and lymph node involvement, while lower BMP-2 mRNA expression was significantly associated with poor overall survival after radical nephrectomy. In RCC cells, BMP-2 restoration significantly inhibited cell proliferation, migration, invasion, and colony formation. In addition, BMP-2 overexpression induced p21(WAF1/CIP1) and p27(KIP1) expression, and cellular apoptosis in RCC cells. BMP-2 mRNA expression was significantly enhanced in RCC cells by 5-aza-2'-deoxycitidine treatment. The prevalence of BMP-2 promoter methylation was significantly greater and BMP-2 mRNA expression was significantly lower in RCC samples as compared to normal kidney samples. Furthermore, a significant correlation was found between BMP-2 promoter methylation and mRNA transcription in tumors. Aberrant BMP-2 methylation and the resultant loss of BMP-2 expression may be a useful molecular marker for designing improved diagnostic and therapeutic strategies for RCC.

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.

Characterization of proteolytic activities during intestinal regeneration of the sea cucumber, Holothuria glaberrima

Proteolysis carried out by different proteases control cellular processes during development and regeneration. Here we investigated the function of the proteasome and other proteases in the process of intestinal regeneration using as a model the sea cucumber Holothuria glaberrima. This echinoderm possesses the ability to regenerate its viscera after a process of evisceration. Enzymatic activity assays showed that intestinal extracts at different stages of regeneration possessed chymotrypsin-like activity. This activity was inhibited by i) MG132, a reversible inhibitor of chymotrypsin and peptidylglutamyl peptidase hydrolase (PGPH) activities of the proteasome, ii) E64d, a permeable inhibitor of cysteine proteases and iii) TPCK, a serine chymotrypsin inhibitor, but not by epoxomicin, an irreversible and potent inhibitor of all enzymatic activities of the proteasome. To elucidate the role which these proteases might play during intestinal regeneration, we carried out in vivo experiments injecting MG132, E64d and TPCK into regenerating animals. The results showed effects on the size of the regenerating intestine, cell proliferation and collagen degradation. These findings suggest that proteolysis by several proteases is important in the regulation of intestinal regeneration in H. glaberrima.

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.

Involvement of BMPs/Smad signaling pathway in mechanical response in osteoblasts

BACKGROUND/AIMS

Mechanical strain plays an important role in osteoblasts differentiation and bone formation but the underlying mechanism remains unclear. The aim of this study was to determine whether Bone Morphogenetic Proteins (BMPs)/Smad signaling pathway is involved in mechanical response in osteoblasts.

METHODS

MC3T3-E1 cells were exposed to mechanical strain via a four-point bending system. mRNA levels and protein levels of BMP-2, BMP-4, Smad1, Smad5, Smurf1, and Smurf2 were assessed using RT-PCR and immunoblotting. Protein levels of BMP-2 and BMP-4 in the culture medium were also determined using Enzyme-linked Immunosorbent Assay (ELISA). Pretreatment with Noggin and transfection with Smad4 siRNA were carried out to block the BMPs/Smad signaling pathway and MG132 was used to inhibit the proteasome pathway.

RESULTS

We found that mechanical strain enhanced alkaline phosphatase (ALP) expression and activated BMPs/Smad signaling pathway. Mechanical strain induced expression of ALP was attenuated by Noggin and by Smad4 siRNA. The protein levels of Smad1 and Smad5, but not their mRNA levels, were up-regulated by mechanical strain. This finding could be explained by the down-regulation of Smurf1. The protein degradation of Smad might be inhibited by mechanical strain through down-regulation of Smuf1 expression. The addition of MG132 further enhanced the mechanical strain induced activation of Smad proteins and the increased expression of ALP.

CONCLUSIONS

Mechanical strain might promote osteoblasts differentiation through BMPs/Smad signaling pathway. The strain causes a drop in Smurf1 levels, leading to accumulation of Smad proteins and, subsequently, to enhanced BMPs/Smad signaling.

Emerging roles of the host defense peptide LL-37 in human cancer and its potential therapeutic applications

Human cathelicidin LL-37, a host defense peptide derived from leukocytes and epithelial cells, plays a crucial role in innate and adaptive immunity. Not only does LL-37 eliminate pathogenic microbes directly but also modulates host immune responses. Emerging evidence from tumor biology studies indicates that LL-37 plays a prominent and complex role in carcinogenesis. Although overexpression of LL-37 has been implicated in the development or progression of many human malignancies, including breast, ovarian and lung cancers, LL-37 suppresses tumorigenesis in gastric cancer. These data are beginning to unveil the intricate and contradictory functions of LL-37. The reasons for the tissue-specific function of LL-37 in carcinogenesis remain to be elucidated. Here, we review the relationship between LL-37, its fragments and cancer progression as well as discuss the potential therapeutic implications of targeting this peptide.

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.

The host defense peptide LL-37 activates the tumor-suppressing bone morphogenetic protein signaling via inhibition of proteasome in gastric cancer cells

The human cathelicidin LL-37, a pleiotropic host defense peptide, is down-regulated in gastric adenocarcinomas. We therefore investigated whether this peptide suppresses gastric cancer growth. LL-37 lowered gastric cancer cell proliferation and delayed G(1)-S transition in vitro and inhibits the growth of gastric cancer xenograft in vivo. In this connection, LL-37 increased the tumor-suppressing bone morphogenetic protein (BMP) signaling, manifested as an increase in BMP4 expression and the subsequent Smad1/5 phosphorylation and the induction of p21(Waf1/Cip1). The anti-mitogenic effect, Smad1/5 phosphorylation, and p21(Waf1/Cip1) up-regulation induced by LL-37 were reversed by the knockdown of BMP receptor II. The activation of BMP signaling was paralleled by the inhibition of chymotrypsin-like and caspase-like activity of proteasome. In this regard, proteasome inhibitor MG-132 mimicked the effect of LL-37 by up-regulating BMP4 expression and Smad1/5 phosphorylation. Further analysis of clinical samples revealed that LL-37 and p21(Waf1/Cip1) mRNA expressions were both down-regulated in gastric cancer tissues and their expressions were positively correlated. Collectively, we describe for the first time that LL-37 inhibits gastric cancer cell proliferation through activation of BMP signaling via a proteasome-dependent mechanism. This unique biological activity may open up novel therapeutic avenue for the treatment of gastric cancer.

Proteasome inhibition: a new therapeutic strategy to cancer treatment

The ubiquitin-proteasome system is a major pathway for protein degradation. Targeting this pathway using proteasome inhibitors represents a novel approach for the treatment of cancer. Proteasome inhibitors lower cell proliferation and induce apoptosis in solid and hematologic malignancies through multiple mechanisms, including stabilization of cell cycle regulators and pro-apoptotic factors, stimulation of bone morphogenetic protein signaling, inhibition of protein translation, and sensitization to ligand-induced apoptosis. In this connection, proteasome inhibition activates macroautophagy, a compensatory protein degradation system, as well as other pro-survival signaling pathways. Inhibition of these auto-protective responses sensitizes cancer cells to the anti-proliferative effects of proteasome inhibitors.

MG-132 inhibits carcinoid growth and alters the neuroendocrine phenotype

BACKGROUND

Carcinoid cancers are the most common neuroendocrine (NE) tumors, and limited treatment options exist. The inhibition of glycogen synthase kinase-3beta (GSK-3beta) has been shown to be a potential therapeutic target for the treatment of carcinoid disease. In this study, we investigate the ability of MG-132, a proteasome inhibitor, to inhibit carcinoid growth, the neuroendocrine phenotype, and its association with GSK-3beta.

MATERIALS AND METHODS

Human pulmonary (NCI-H727) and gastrointestinal (BON) carcinoid cells were treated with MG-132 (0-4microM). Cellular growth was measured by the 3-[4,5-dimethylthiazole-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay. Levels of total and phosphorylated GSK-3beta and the NE markers chromogranin A (CgA), Achaete-Scute complex-like 1 (ASCL1), as well as the apoptotic markers poly (ADP-ribose), polymerase (PARP), and cleaved caspase-3 were determined by Western blot.

RESULTS

Treating carcinoid cells with MG-132 resulted in growth inhibition, a dose-dependent inhibition of CgA and ASCL1, as well as an increase in the levels of cleaved PARP and cleaved caspase-3. Additionally, an increase in the level of phosphorylated GSK-3beta was observed.

CONCLUSION

MG-132 inhibits cellular growth and the neuroendocrine phenotype. This proteasome inhibitor warrants further preclinical investigation as a possible therapeutic strategy for intractable carcinoid disease.

Enhancement of difficult nonunion in children with osteogenic protein-1 (OP-1): early experience

Numerous studies have described the use of osteogenic protein-1 (OP-1) in adults, but there are few reports in children. The objectives of this short-term followup cohort study were (1) to examine clinical and radiographic healing of persistent nonunions after OP-1 application in children; and (2) to determine the safety of OP-1 use in this sample. Clinical healing was defined by absence of pain and tenderness at the nonunion site and the ability to fully weight bear on the affected limb. Radiographic healing was determined by bony bridging of the nonunion site in at least one view. Safety was defined as the absence of major adverse events, including allergic reactions, infections, local inflammatory reactions, and heterotopic ossification. OP-1 was used in 19 patients who had an operative procedure for the bridging of persistent nonunions between 1999 and 2007. The mean age was 11.6 years (range, 4.8-20.3 years). Thirteen patients had persistent nonunion after one or more previous surgeries, prior to the initial OP-1 application. A single dose of 3.5 mg of OP-1 mixed with 1 g of Type I bovine collagen was applied to 23 sites of 19 patients. Three patients received additional OP-1 applications. Healing occurred clinically and radiographically in 17 of the 23 sites. Complications included four superficial pin site infections, one deep infection, and two fractures. No major local adverse event related to OP-1 application was noted in our sample. Our findings suggest OP-1 stimulates healing of persistent nonunions without major adverse events in our patient population.

LEVEL OF EVIDENCE

Level IV, case series. See the guidelines online for a complete description of levels of evidence.

Inhibition of macroautophagy by bafilomycin A1 lowers proliferation and induces apoptosis in colon cancer cells

Macroautophagy is a process by which cytoplasmic content and organelles are sequestered by double-membrane bound vesicles and subsequently delivered to lysosomes for degradation. Macroautophagy serves as a major intracellular pathway for protein degradation and as a pro-survival mechanism in time of stress by generating nutrients. In the present study, bafilomycin A(1), a vacuolar type H(+)-ATPase inhibitor, suppresses macroautophagy by preventing acidification of lysosomes in colon cancer cells. Diminished macroautophagy was evidenced by the accumulation of undegraded LC3 protein. Suppression of macroautophagy by bafilomycin A(1) induced G(0)/G(1) cell cycle arrest and apoptosis which were accompanied by the down-regulation of cyclin D(1) and cyclin E, the up-regulation of p21(Cip1) as well as cleavages of caspases-3, -7, -8, and -9 and PARP. Further investigation revealed that bafilomycin A(1) increased the phosphorylation of ERK, JNK, and p38. In this regard, p38 inhibitor partially reversed the anti-proliferative effect of bafilomycin A(1). To conclude, inhibition of macroautophagy by bafilomycin A(1) lowers G(1)-S transition and induces apoptosis in colon cancer cells. Our results not only indicate that inhibitors of macroautophagy may be used therapeutically to inhibit cancer growth, but also delineate the relationship between macroautophagy and apoptosis.

Induction of autophagy by proteasome inhibitor is associated with proliferative arrest in colon cancer cells

The ubiquitin-proteasome system (UPS) and lysosome-dependent macroautophagy (autophagy) are two major intracellular pathways for protein degradation. Blockade of UPS by proteasome inhibitors has been shown to activate autophagy. Recent evidence also suggests that proteasome inhibitors may inhibit cancer growth. In this study, the effect of a proteasome inhibitor MG-132 on the proliferation and autophagy of cultured colon cancer cells (HT-29) was elucidated. Results showed that MG-132 inhibited HT-29 cell proliferation and induced G(2)/M cell cycle arrest which was associated with the formation of LC3(+) autophagic vacuoles and the accumulation of acidic vesicular organelles. MG-132 also increased the protein expression of LC3-I and -II in a time-dependent manner. In this connection, 3-methyladenine, a Class III phosphoinositide 3-kinase inhibitor, significantly abolished the formation of LC3(+) autophagic vacuoles and the expression of LC3-II but not LC3-I induced by MG-132. Taken together, this study demonstrates that inhibition of proteasome in colon cancer cells lowers cell proliferation and activates autophagy. This discovery may shed a new light on the novel function of proteasome in the regulation of autophagy and proliferation in colon cancer cells.