Caveolin-1 is transcribed from a hypermethylated promoter to mediate colonocyte differentiation and apoptosis

Platelet-derived microparticles stimulate the invasiveness of colorectal cancer cells via the p38MAPK-MMP-2/MMP-9 axis

BACKGROUND

Metastasis is the main cause of death in patients with colorectal cancer (CRC). Apart from platelets, platelet-derived microparticles (PMPs) are also considered important factors that can modify the activity of cancer cells. PMPs are incorporated by cancer cells and can also serve as intracellular signalling vesicles. PMPs are believed to affect cancer cells by upregulating their invasiveness. To date, there is no evidence that such a mechanism occurs in colorectal cancer. It has been shown that platelets can stimulate metalloproteases (MMPs) expression and activity via the p38MAPK pathway in CRC cells, leading to their elevated migratory potential. This study aimed to investigate the impact of PMPs on the invasive potential of CRC cells of various phenotypes via the MMP-2, MMP-9 and p38MAPK axis.

METHODS

We used various CRC cell lines, including the epithelial-like HT29 and the mesenchymal-like SW480 and SW620. Confocal imaging was applied to study PMP incorporation into CRC cells. The presence of surface receptors on CRC cells after PMP uptake was evaluated by flow cytometry. Transwell and scratch wound-healing assays were used to evaluate cell migration. The level of C-X-C chemokine receptor type 4 (CXCR4), MMP-2, and MMP-9 and the phosphorylation of ERK1/2 and p38MAPK were measured by western blot. MMP activity was determined using gelatine-degradation assays, while MMP release was evaluated by ELISA.

RESULTS

We found that CRC cells could incorporate PMPs in a time-dependent manner. Moreover, PMPs could transfer platelet-specific integrins and stimulate the expression of integrins already present on tested cell lines. While mesenchymal-like cells expressed less CXCR4 than epithelial-like CRC cells, PMP uptake did not increase its intensity. No significant changes in CXCR4 level either on the surface or inside CRC cells were noticed. Levels of cellular and released MMP-2 and MMP-9 were elevated in all tested CRC cell lines after PMP uptake. PMPs increased the phosphorylation of p38MAPK but not that of ERK1/2. Inhibition of p38MAPK phosphorylation reduced the PMP-induced elevated level and release of MMP-2 and MMP-9 as well as MMP-dependent cell migration in all cell lines.

CONCLUSIONS

We conclude that PMPs can fuse into both epithelial-like and mesenchymal-like CRC cells and increase their invasive potential by inducing the expression and release of MMP-2 and MMP-9 via the p38MAPK pathway, whereas CXCR4-related cell motility or the ERK1/2 pathway appears to not be affected by PMPs. Video Abstract.

Epigenetic insights in the diagnosis, prognosis, and treatment selection in CRC, an updated review

BACKGROUND/AIM

The gradual accumulation of genetic and epigenetic alterations can lead to the development of colorectal cancer. In the last decade much research has been done to discover how methylation as an epigenetic alteration leads to carcinogenesis. While Methylation is a biological process, it can influence gene expression by affecting the promoter activity. This article reviews the role of methylation in critical pathways in CRC.

METHODS

In this study using appropriate keywords, all research and review articles related to the role of methylation on different cancers were collected and analyzed. Also, existing information on methylation detection methods and therapeutic sensitivity or resistance due to DNA methylation were reviewed.

RESULTS

The results of this survey revealed that while Methylation is a biological process, it can influence gene expression by affecting the promoter activity. Promoter methylation is associated with up or downregulation of genes involved in critical pathways, including cell cycle, DNA repair, and cell adherence. Hence promoter methylation can be used as a molecular tool for early diagnosis, improving treatment, and predicting treatment resistance.

CONCLUSION

Current knowledge on potential methylation biomarkers for diagnosis and prognoses of CRC has also been discussed. Our survey proposes that a multi-biomarker panel is more efficient than a single biomarker in the early diagnosis of CRC.

FABP7 Regulates Acetyl-CoA Metabolism Through the Interaction with ACLY in the Nucleus of Astrocytes

Fatty acid binding protein 7 (FABP7) is an intracellular fatty acid chaperon that is highly expressed in astrocytes, oligodendrocyte-precursor cells, and malignant glioma. Previously, we reported that FABP7 regulates the response to extracellular stimuli by controlling the expression of caveolin-1, an important component of lipid raft. Here, we explored the detailed mechanisms underlying FABP7 regulation of caveolin-1 expression using primary cultured FABP7-KO astrocytes as a model of loss of function and NIH-3T3 cells as a model of gain of function. We discovered that FABP7 interacts with ATP-citrate lyase (ACLY) and is important for acetyl-CoA metabolism in the nucleus. This interaction leads to epigenetic regulation of several genes, including caveolin-1. Our novel findings suggest that FABP7-ACLY modulation of nuclear acetyl-CoA has more influence on histone acetylation than cytoplasmic acetyl-CoA. The changes to histone structure may modify caveolae-related cell activity in astrocytes and tumors, including malignant glioma.

Low-intensity pulsed ultrasound affects growth, differentiation, migration, and epithelial-to-mesenchymal transition of colorectal cancer cells

Ultrasound (US) offers potentially important opportunities from a therapeutic point of view. Thus, the study of the biological effects of US on cancer cells is important to understand the consequences of these changes on the malignant phenotype. This study aimed to investigate the effects of low-intensity ultrasound (LIPUS) on the phenotype of colorectal cancer cell lines. Cell proliferation was evaluated by viability test and by evaluation of pERK expression, while cell motility using the scratch test. Cell differentiation was evaluated assessing alkaline phosphatase activity. Epithelial mesenchymal transition was assessed by analyzing the expression of Vimentin and E-Cadherin. Release and uptake of extracellular vesicles (EVs) were evaluated by flow cytometry. LIPUS effects on the organization of cytoskeleton were analyzed by confocal microscopy and by evaluation of Rho GTPase expression. No alterations in vitality and clonogenicity were observed when the intermediate (0.4 MPa) and the lowest (0.035 MPa) acoustic intensities were administered while the treatment with high intensity (1 MPa) induced a reduction of both cell viability and clonogenicity in both cell lines in a frequency-dependent manner. LIPUS promoted the differentiation of colon cancer cells, affected epithelial-to-mesenchymal transition, promoted the closure of a wound as well as increased the release of EVs compared with untreated cells. LIPUS-induced increase in cell motility was likely due to a Rho GTPase-dependent mechanism. Overall, the results obtained warrant further studies on the potential combined effect of LIPUS with differentiating agents and on their potential use in a clinical setting.

Down expression of lnc-BMP1-1 decreases that of Caveolin-1 is associated with the lung cancer susceptibility and cigarette smoking history

Lnc-BMP1-1 is a lncRNA transcribed from SFTPC (surfactant associated protein C), a lung tissue specific gene encoding pulmonary-associated surfactant protein C (SPC) that is solely secreted by alveolar typeⅡ epithelial cells, among which the ones with SFTPC+ might be transformed into lung adenocarcinoma cells. Caveolin-1 (Cav-1) is a candidate tumor suppressor gene and is vital for coping with oxidative stress induced by cigarette smoke. When comparing lung cancer tissues with their adjacent normal tissues, the expression of lnc-BMP1-1 were decreased, especially in patients with cigarette smoking history (P=0.027), and positively associated with the expression of Cav-1 (P<0.001). When comparing to A549 cells transfected with empty vector (A549-NC cells), the expression level of Cav-1 in A549 cells with over-expressed lnc-BMP1-1 (A549-BMP cells) was increased along with the decreased level of HDAC2 protein. The drug sensitivity of A549-BMP cells to Doxorubicin hydrochloride (DOX) was increased; the growth and migration capability of A549-BMP cells were inhibited along with the decreased protein level of Bcl-2 and DNMT3a; the growth of tumor in nude mice injected with A549-BMP cells were inhibited, too. Furthermore, the lnc-BMP1-1 and Cav-1 expression was also down-regulated in the human bronchial epithelial (16HBE) cells treated with cigarette smoke extract (CSE).

Caveolin-1 is Markedly Downregulated in Patients with Early-Stage Colorectal Cancer

BACKGROUND

Caveolin-1 (CAV-1), the main scaffold protein in caveolae, is frequently deregulated in human cancer. Of importance, this protein has been described to show tumor suppressor or oncogenic properties depending on the cell type and the stage of the disease. In fact, its role in colorectal cancer (CRC) remains to be fully clarified due to discrepancies in the literature.

METHODS

We analyzed CAV-1 by western blot in a set of early-stage CRC patients with paired tumor tissue and normal colonic mucosa available. CAV-1 mRNA and expression levels of miR-124, 133 and 802 were quantified by real-time PCR.

RESULTS

We found CAV-1 strongly downregulated in 76.2% of tumor samples and associated with the subgroup of elderly patients (p = 0.027). We observed by real-time PCR a lack of correlation between CAV-1 mRNA and protein levels in some cases with CAV-1 downregulated by western blot, and miR-124 deregulation was identified as a potential contributing alteration to decrease CAV-1 protein expression.

CONCLUSION

CAV-1 is commonly downregulated in patients with primary CRC, which suggests its tumor suppressor role in early stages of this disease. Moreover, based on our findings, the previous discrepancies observed in different studies to date could be due to a complex posttranscriptional CAV-1 regulation.

Abrus agglutinin stimulates BMP-2-dependent differentiation through autophagic degradation of β-catenin in colon cancer stem cells

Eradicating cancer stem cells (CSCs) in colorectal cancer (CRC) through differentiation therapy is a promising approach for cancer treatment. Our retrospective tumor-specimen analysis elucidated alteration in the expression of bone morphogenetic protein 2 (BMP-2) and β-catenin during the colon cancer progression, indicating that their possible intervention through "forced differentiation" in colon cancer remission. We reveal that Abrus agglutinin (AGG) induces the colon CSCs differentiation, and enhances sensitivity to the anticancer therapeutics. The low dose AGG (max. dose = 100 ng/mL) decreased the expression of stemness-associated molecules such as CD44 and β-catenin in the HT-29 cell derived colonospheres. Further, AGG augmented colonosphere differentiation, as demonstrated by the enhanced CK20/CK7 expression ratio and induced alkaline phosphatase activity. Interestingly, the AGG-induced expression of BMP-2 and the AGG-induced differentiation were demonstrated to be critically dependent on BMP-2 in the colonospheres. Similarly, autophagy-induction by AGG was associated with colonosphere differentiation and the gene silencing of BMP-2 led to the reduced accumulation of LC3-II, suggesting that AGG-induced autophagy is dependent on BMP-2. Furthermore, hVps34 binds strongly to BMP-2, indicating a possible association of BMP-2 with the process of autophagy. Moreover, the reduction in the self-renewal capacity of the colonospheres was associated with AGG-augmented autophagic degradation of β-catenin through an interaction with the autophagy adaptor protein p62. In the subcutaneous HT-29 xenograft model, AGG profoundly inhibited the growth of tumors through an increase in BMP-2 expression and LC3-II puncta, and a decrease in β-catenin expression, confirming the antitumor potential of AGG through induction of differentiation in colorectal cancer.

Butyrate and docosahexaenoic acid interact in alterations of specific lipid classes in differentiating colon cancer cells

Docosahexaenoic acid (DHA) and sodium butyrate (NaBt) exhibit a number of interactive effects on colon cancer cell growth, differentiation, or apoptosis; however, the molecular mechanisms responsible for these interactions and their impact on cellular lipidome are still not fully clear. Here, we show that both dietary agents together induce dynamic alterations of lipid metabolism, specific cellular lipid classes, and fatty acid composition. In HT-29 cell line, a model of differentiating colon carcinoma cells, NaBt supported incorporation of free DHA into non-polar lipids and their accumulation in cytoplasmic lipid droplets. DHA itself was not incorporated into sphingolipids; however, it significantly altered representation of individual ceramide (Cer) classes, in particular in combination with NaBt (DHA/NaBt). We observed altered expression of enzymes involved in Cer metabolism in cells treated with NaBt or DHA/NaBt, and exogenous Cer 16:0 was found to promote induction of apoptosis in differentiating HT-29 cells. NaBt, together with DHA, increased n-3 fatty acid synthesis and attenuated metabolism of monounsaturated fatty acids. Finally, DHA and/or NaBt altered expression of proteins involved in synthesis of fatty acids, including elongase 5, stearoyl CoA desaturase 1, or fatty acid synthase, with NaBt increasing expression of caveolin-1 and CD36 transporter, which may further promote DHA incorporation and its impact on cellular lipidome. In conclusion, our results indicate that interactions of DHA and NaBt exert complex changes in cellular lipidome, which may contribute to the alterations of colon cancer cell differentiation/apoptotic responses. The present data extend our knowledge about the nature of interactive effects of dietary fatty acids.

Anti-neoplastic drugs increase caveolin-1-dependent migration, invasion and metastasis of cancer cells

Expression of the scaffolding protein Caveolin-1 (CAV1) enhances migration and invasion of metastatic cancer cells. Yet, CAV1 also functions as a tumor suppressor in early stages of cancer, where expression is suppressed by epigenetic mechanisms. Thus, we sought to identify stimuli/mechanisms that revert epigenetic CAV1 silencing in cancer cells and evaluate how this affects their metastatic potential. We reasoned that restricted tissue availability of anti-neoplastic drugs during chemotherapy might expose cancer cells to sub-therapeutic concentrations, which activate signaling pathways and the expression of CAV1 to favor the acquisition of more aggressive traits. Here, we used in vitro [2D, invasion] and in vivo (metastasis) assays, as well as genetic and biochemical approaches to address this question. Colon and breast cancer cells were identified where CAV1 levels were low due to epigenetic suppression and could be reverted by treatment with the methyltransferase inhibitor 5’-azacytidine. Exposure of these cells to anti-neoplastic drugs for short periods of time (24-48 h) increased CAV1 expression through ROS production and MEK/ERK activation. In colon cancer cells, increased CAV1 expression enhanced migration and invasion in vitro via pathways requiring Src-family kinases, as well as Rac-1 activity. Finally, elevated CAV1 expression in colon cancer cells following exposure in vitro to sub-cytotoxic drug concentrations increased their metastatic potential in vivo. Therefore exposure of cancer cells to anti-neoplastic drugs at non-lethal drug concentrations induces signaling events and changes in transcription that favor CAV1-dependent migration, invasion and metastasis. Importantly, this may occur in the absence of selection for drug-resistance.

Polo-like kinase 1 expression is suppressed by CCAAT/enhancer-binding protein α to mediate colon carcinoma cell differentiation and apoptosis

BACKGROUND

Human polo-like kinase 1 (PLK1), a highly conserved serine/threonine kinase is a key player in several essential cell-cycle events. PLK1 is considered an oncogene and its overexpression often correlates with poor prognosis of cancers, including colorectal cancer (CRC). However, regulation of PLK1 expression in colorectal cells was never studied earlier and it is currently unknown if PLK1 regulates differentiation and apoptosis of CRC.

METHODS

PLK1 expression was analyzed by real-time PCR and western blotting. Transcriptional regulation was studied by reporter assay, gene knock-down, EMSA and ChIP.

RESULTS

PLK1 expression was down-regulated during butyrate-induced differentiation of HT-29 and other CRC cells. Also, PLK1 down-regulation mediated the role of butyrate in CRC differentiation and apoptosis. We report here a novel transcriptional regulation of PLK1 by butyrate. Transcription factors CCAAT/enhancer-binding protein α (C/EBPα) and Oct-1 share an overlapping binding site over the PLK1 promoter. Elevated levels of C/EBPα by butyrate treatment of CRC cells competed out the activator protein Oct-1 from binding to the PLK1 promoter and sequestered it. Binding of C/EBPα was associated with increased deacetylation near the transcription start site (TSS) of the PLK1 promoter, which abrogated transcription through reduced recruitment of RNA polymerase II. We also found a synergistic role between the synthetic PLK1-inhibitor SBE13 and butyrate on the apoptosis of CRC cells.

CONCLUSION

This study offered a novel p53-independent regulation of PLK1 during CRC differentiation and apoptosis.

GENERAL SIGNIFICANCE

Down-regulation of PLK1 is one of the mechanisms underlying the anti-cancer role of dietary fibre-derived butyrate in CRC.

Epigenetic Regulation of Caveolin-1 Gene Expression in Lung Fibroblasts

Fibrotic disorders are associated with tissue accumulation of fibroblasts. We recently showed that caveolin (Cav)-1 gene suppression by a profibrotic cytokine, transforming growth factor (TGF)-β1, contributes to fibroblast proliferation and apoptosis resistance. Cav-1 has been shown to be constitutively suppressed in idiopathic pulmonary fibrosis (IPF), but mechanisms for this suppression are incompletely understood. We hypothesized that epigenetic processes contribute to Cav-1 down-regulation in IPF lung fibroblasts, and after fibrogenic stimuli. Cav-1 expression levels, DNA methylation status, and histone modifications associated with the Cav-1 promoter were examined by PCR, Western blots, pyrosequencing, or chromatin immunoprecipitation assays in IPF lung fibroblasts, normal fibroblasts after TGF-β1 stimulation, or in murine lung fibroblasts after bleomycin injury. Methylation-specific PCR demonstrated methylated and unmethylated Cav-1 DNA copies in all groups. Despite significant changes in Cav-1 expression, no changes in DNA methylation were observed in CpG islands or CpG island shores of the Cav-1 promoter by pyrosequencing of lung fibroblasts from IPF lungs, in response to TGF-β1, or after bleomycin-induced murine lung injury, when compared with respective controls. In contrast, the association of Cav-1 promoter with the active histone modification mark, H3 lysine 4 trimethylation, correlated with Cav-1 down-regulation in activated/fibrotic lung fibroblasts. Our data indicate that Cav-1 gene silencing in lung fibroblasts is actively regulated by epigenetic mechanisms that involve histone modifications, in particular H3 lysine 4 trimethylation, whereas DNA methylation does not appear to be a primary mechanism. These findings support therapeutic strategies that target histone modifications to restore Cav-1 expression in fibroblasts participating in pathogenic tissue remodeling.

Aberrant CpG Island Shore Region Methylation of CAV1 Is Associated with Tumor Progression and Poor Prognosis in Gastric Cardia Adenocarcinoma

BACKGROUND AND AIMS

Caveolin-1 (CAV1) is a multifunctional scaffolding protein and plays an important role in tumorigenesis. However, the epigenetic changes of CAV1 in gastric cardia adenocarcinoma (GCA) have not been investigated so far. The purpose of this study was to clarify the contribution of critical CpG sites in CAV1 to progression/prognosis of GCA and to further elucidate the effect of critical CpG sites on the ectopic expression of β-catenin in GCA.

METHODS

Methylation-specific polymerase chain reaction (MSP) and bisulfite genomic sequencing (BGS) methods were, respectively, applied to examine the methylation status of CAV1. RT-PCR and immunohistochemistry methods were used to determine the mRNA and protein expression of CAV1 and β-catenin.

RESULTS

Decreased mRNA and protein expression of CAV1 were observed in GCA tumor tissues and were associated with hypermethylation of CpG island shore and transcription start site (TSS) regions in CAV1. Hypermethylation of the other two regions within CpG islands in CAV1 was observed both in tumor and corresponding adjacent tissues but was not related to the transcriptional inhibition of CAV1. The methylation status of CpG island shore region in CAV1 was associated with the ectopic expression of β-catenin and was independently associated with survival in GCA patients.

CONCLUSIONS

Hypermethylation of CpG island shore and TSS regions is cancer specific and is closely associated with reduced expression of CAV1. The CpG island shore methylation of CAV1 may play an important role in progression of GCA and may serve as a prognostic methylation biomarker for GCA patients.

Oral absorption of peptides and nanoparticles across the human intestine: Opportunities, limitations and studies in human tissues

In this contribution, we review the molecular and physiological barriers to oral delivery of peptides and nanoparticles. We discuss the opportunities and predictivity of various in vitro systems with special emphasis on human intestine in Ussing chambers. First, the molecular constraints to peptide absorption are discussed. Then the physiological barriers to peptide delivery are examined. These include the gastric and intestinal environment, the mucus barrier, tight junctions between epithelial cells, the enterocytes of the intestinal epithelium, and the subepithelial tissue. Recent data from human proteome studies are used to provide information about the protein expression profiles of the different physiological barriers to peptide and nanoparticle absorption. Strategies that have been employed to increase peptide absorption across each of the barriers are discussed. Special consideration is given to attempts at utilizing endogenous transcytotic pathways. To reliably translate in vitro data on peptide or nanoparticle permeability to the in vivo situation in a human subject, the in vitro experimental system needs to realistically capture the central aspects of the mentioned barriers. Therefore, characteristics of common in vitro cell culture systems are discussed and compared to those of human intestinal tissues. Attempts to use the cell and tissue models for in vitro-in vivo extrapolation are reviewed.

Biphasic Ccl20 regulation by Toll-like receptor 9 through the activation of ERK-AP-1 and non-canonical NF-κB signaling pathways

BACKGROUND

Chemokines play key roles in immune homeostasis and inflammatory response. Considering the role of Ccl20 and Toll-like receptor 9 (TLR9) in gut homeostasis and inflammatory bowel disease (IBD), regulation of Ccl20 by bacterial DNA, the TLR9 ligand, merits in-depth studies.

METHODS

We analyzed Ccl20 expression in various epithelial cell (EC) lines by q-PCR and ELISA. In-vivo expression was investigated in isolated murine colonocytes by immunoblotting. Transcriptional regulation of Ccl20 was studied by reporter assays, gene knock-down, electrophoretic mobility shift assay and chromatin immunoprecipitation. Activation of upstream kinases was checked by immunoblotting.

RESULTS

We showed low levels of Ccl20 expression in mouse colonic ECs, but marked induction by in vivo treatment with bacterial DNA. This corroborated with persistent Ccl20 induction in different EC lines. We found involvement of MAP-kinases during the early hours after stimulation, and a novel AP-1site (-252bp) regulated the expression in colonic ECs. More importantly, mutually exclusive transcriptional regulation by AP-1 (cjun/cfos) and non-canonical NF-κB (RelB/p52) downstream of MEK-ERK and NIK-IKK-α-NF-κB2 (p100) phosphorylation, respectively was responsible for persistent Ccl20 expression in the colonic cells, while canonical NF-κB isoforms played no role.

CONCLUSIONS

Persistent Ccl20 induction by TLR9 in colonic ECs involves early and delayed activation of two independent signaling pathways. This is the first report of non-canonical NF-κB activation and Ccl20 expression in the colonic ECs by TLR9.

GENERAL SIGNIFICANCE

Our study will help to better understand immune regulation by Ccl20 in the intestine and may be exploited for future development of novel therapeutics against IBD.

Suppression of Spleen Tyrosine Kinase (Syk) by Histone Deacetylation Promotes, Whereas BAY61-3606, a Synthetic Syk Inhibitor Abrogates Colonocyte Apoptosis by ERK Activation

Spleen tyrosine kinase (Syk), a non-receptor tyrosine kinase, regulates tumor progression, either negatively or positively, depending on the tissue lineage. Information about the role of Syk in colorectal cancers (CRC) is limited, and conflicting reports have been published. We studied Syk expression and its role in differentiation and apoptosis of the colonocytes. Here, we reported for the first time that expression of two transcript variants of Syk is suppressed in colonocytes during butyrate-induced differentiation, which mediates apoptosis of HT-29 cells. Despite being a known HDAC inhibitor, butyrate deacetylates histone3/4 around the transcription start site (TSS) of Syk. Histone deacetylation precludes the binding of RNA Polymerase II to the promoter and inhibits transcription. Since butyrate is a colonic metabolite derived from undigested fibers, our study offers a plausible explanation of the underlying mechanisms of the protective role of butyrate as well as the dietary fibers against CRC through the regulation of Syk. We also report that combined use of butyrate and highly specific Syk inhibitor BAY61-3606 does not enhance differentiation and apoptosis of colonocytes. Instead, BAY completely abolishes butyrate-induced differentiation and apoptosis in a Syk- and ERK1/2-dependent manner. While butyrate dephosphorylates ERK1/2 in HT-29 cells, BAY re-phosphorylates it, leading to its activation. This study describes a novel mechanism of butyrate action in CRC and explores the role of Syk in butyrate-induced differentiation and apoptosis. In addition, our study highlights those commercial small molecule inhibitors, although attractive drug candidates should be used with concern because of their frequent off-target effects. J. Cell. Biochem. 118: 191-203, 2017. © 2016 Wiley Periodicals, Inc.