COLO 320DM Cells Research Articles

New insights of RA-V cyclopeptide as an autophagy inhibitor in human COLO 320DM cancer cell lines

Colon cancer is the leading cause for the malignancy in the gastrointestinal tract. Autophagy is a self-degradation process of the unnecessary, injured and aged organelles and proteins in the cell, which is followed by recovering of degraded products. Apoptosis is a programmed cell death which is characterized by membrane blebbing, chromosome condensation and nuclear fragmentation. Apoptosis and autophagy can occur frequently in a cell, predominantly in a series preceding apoptosis through autophagy by the formation of autophagosomes. In current research, the impact of autophagy inhibition and apoptosis activation were found to be the targeted strategies to treat colon cancer. This study is focused on the apoptotic potential of RA-V, a natural cyclopeptide through the inhibition of protective autophagy in colon cancer cells. Growth inhibitory properties were observed in the RA-V treated (125 μM) colo 320DM cells using cell viability assay. RA-V induced apoptosis of colo 320DM cells at the maximum concentration of 125 μM, which was observed using DAPI and Annexin - PI staining methods. In this study we also examined the mechanistic role of RA-V (125 μM) incolo 320DM cells in the presence of Rapamycin (mTOR inhibitor) and chloroquine (autophagy inhibitor) using MDC and AO staining methods.

SIRT1 stabilizes extrachromosomal gene amplification and contributes to repeat-induced gene silencing

Sirtuin 1 (SIRT1) is a protein deacetylase that maintains genome stability by preventing the activation of latent replication origins. Amplified genes in cancer cells localize on either extrachromosomal double minutes (DMs) or the chromosomal homogeneously staining region. Previously, we found that a plasmid with a mammalian replication initiation region and a matrix attachment region spontaneously mimics gene amplification in cultured animal cells and efficiently generates DMs and/or an homogeneously staining region. Here, we addressed the possibility that SIRT1 might be involved in initiation region/matrix attachment region–mediated gene amplification using SIRT1-knockout human COLO 320DM cells. Consequently, we found that extrachromosomal amplification was infrequent in SIRT1-deficient cells, suggesting that DNA breakage caused by latent origin activation prevented the formation of stable extrachromosomal amplicons. Moreover, we serendipitously found that reporter gene expression from the amplified repeats, which is commonly silenced by repeat-induced gene silencing (RIGS) in SIRT1-proficient cells, was strikingly higher in SIRT1-deficient cells, especially in the culture treated with the histone deacetylase inhibitor butyrate. Compared with the SIRT1-proficient cells, the gene expression per copy was up to thousand-fold higher in the sorter-isolated highest 10% cells among the SIRT1-deficient cells. These observations suggest that SIRT1 depletion alleviates RIGS. Thus, SIRT1 may stabilize extrachromosomal amplicons and facilitate RIGS. This result could have implications in cancer malignancy and protein expression.

DNA methylation in the upstream CpG island of the GPER locus and its relationship with GPER expression in colon cancer cell lines.

The G-protein coupled estrogen receptor (GPER), a proposed tumor suppressor, relays short-term non-genomic responses in target cells and tissues. It frequently undergoes down-modulation in primary tumors of the breast, ovary, and endometrium. Liu and co-workers recently reported loss of GPER expression in colorectal cancer and attributed it to DNA methylation-dependent silencing. We hypothesized that GPER expression is inversely correlated with methylation in the upstream CpG island (upCpGi) in the GPER locus.Methylation in the upCpGi was analysed by bisulfite sequencing and correlated with GPER expression in a panel of colon cancer cell lines. Eight downstream CpGs of the upCpGi was differentially methylated across the cell lines. Methylation in this differentially methylated region (DMR) correlated inversely with GPER expression. Two cell lines, namely SW620 and COLO-320DM, were compared in terms of their viability in response to varying concentrations of G1, a GPER specific agonist. SW-620 cells, which had the least methylated DMR and the highest level of GPER expression, showed significant loss of viability with 1µM G1. COLO-320DM, which had the most methylated DMR and the lowest level of GPER expression, did not show a significant response to 1µM G1. At 5µM G1, SW620 cells showed a greater reduction in viability than COLO-320DM cells.DNA methylation in the DMR is inversely correlated with GPER expression. DNA methylation-dependent silencing of GPER maybe, at least in part, the underlying reason behind the loss of estrogen's oncoprotective effect via GPER in the colon.

Anti-proliferation and radiation-sensitizing effect of an anthocyanidin- rich extract from purple-shoot tea on colon cancer cells

Teas are known to have several health promoting benefits due to polyphenol contents. Two varieties of tea cyanins, Purple-Shoot Tea (not registered) and TTES No. 12, were selected, dehydrated or prepared to green tea to evaluate the anti-proliferative and radiation-sensitizing effects on colon cancer cells. The tea cyanins were extracted by using three drying treatments which are freeze-dried, hot-air dried and green tea manufacturing. The composition analysis showed that the extracts of purple-shoot teas contained more polyphenols, flavonoids, condensed tannins, anthocyanins and proanthocyanidins than TTES No. 12 under various tea processes. Lyophilized tea samples had better antioxidant capacities and reducing power than those of samples from hot-air dried and green tea manufacturing. Anti-proliferation results from HT-29, Colo 320DM and CT-26 cell lines showed that Purple-shoot tea had prominent inhibitory activities which might be correlated to its antioxidative properties. The cell cycle studies confirmed that Purple-shoot tea arrested colon cancer cell at G0/G1 phase. Tested tea samples had radiation-sensitizing effect on the CT-26 cell with 2Gy Co-60 irradiation. Higher anthocyanidin and anthocyanin contents in Purple-shoot tea may contribute to enhanced cytotoxicity and induction of apoptosis after irradiation. The radiation-sensitive effect of Purple-shoot tea on carcinoma cells suggested that nature compounds such as tea polyphenol can be utilized to reduce the dosage in radiotherapy in the future.

Tankyrase Inhibitors Target Colorectal Cancer Stem Cells via AXIN-Dependent Downregulation of c-KIT Tyrosine Kinase.

Cancer stem cells (CSC) constitute heterogeneous cell subpopulations of a tumor. Although targeting CSCs is important for cancer eradication, no clinically approved drugs that target CSCs have been established. Tankyrase poly(ADP-ribosyl)ates and destabilizes AXIN, a negative regulator of β-catenin, and promotes β-catenin signaling. Here, we report that tankyrase inhibitors downregulate c-KIT tyrosine kinase and inhibit the growth of CD44-positive colorectal CSCs. c-KIT expression in CD44-positive subpopulations of colorectal cancer COLO-320DM cells is associated with their tumor-initiating potential in vivo Tankyrase inhibitors downregulate c-KIT expression in established cell lines, such as COLO-320DM and DLD-1, and colorectal cancer patient-derived cells. These effects of tankyrase inhibitors are caused by reducing the recruitment of SP1 transcription factor to the c-KIT gene promoter and depend on AXIN2 stabilization but not β-catenin downregulation. Whereas c-KIT knockdown inhibits the growth of CD44-positive COLO-320DM cells, c-KIT overexpression in DLD-1 cells confers resistance to tankyrase inhibitors. Combination of a low-dose tankyrase inhibitor and irinotecan significantly inhibited the growth of COLO-320DM tumors in a mouse xenograft model. These observations suggest that tankyrase inhibitors target c-KIT-positive colorectal CSCs and provide a novel therapeutic strategy for cancer.

Double-strand breakage in the extrachromosomal double minutes triggers their aggregation in the nucleus, micronucleation, and morphological transformation.

Gene amplification plays a pivotal role in malignant transformation. Amplified genes often reside on extrachromosomal double minutes (DMs). Low-dose hydroxyurea induces DM aggregation in the nucleus which, in turn, generates micronuclei composed of DMs. Low-dose hydroxyurea also induces random double-strand breakage throughout the nucleus. In the present study, we found that double-strand breakage in DMs is sufficient for induction of DM aggregation. Here, we used CRISPR/Cas9 to introduce specific breakages in both natural and artificially tagged DMs of human colorectal carcinoma COLO 320DM cells. Aggregation occurred in the S phase but not in the G1 phase within 4 hours after breakage, which suggested the possible involvement of homologous recombination in the aggregation of numerous DMs. Simultaneous detection of DMs and the phosphorylated histone H2AX revealed that the aggregation persisted after breakage repair. Thus, the aggregate generated cytoplasmic micronuclei at the next interphase. Our data also suggested that micronuclear entrapment eliminated the DMs or morphologically transformed them into giant DMs or homogeneously staining regions (HSRs). In this study, we obtained a model explaining the consequences of DMs after double-strand breakage in cancer cells. Because double-strand breakage is frequently involved in cancer therapy, the model suggests how it affects gene amplification.

Synergistic Effect of Combined Treatment with Longan Flower Extract and 5-Fluorouracil on Colorectal Cancer Cells

To investigate the influence of longan flower extract (LFE) on the sensitization of colorectal cancer (CRC) cells to 5-fluorouracil (5-FU) treatment, HT-29, Colo 320DM and SW480 cells were treated with LFE and 5-FU alone and in combination, and the cell viability was then assessed by trypan blue exclusion, the cell cycle by propidium iodide staining, the mitochondria membrane potential by rhodamine 123 staining, and the expression levels of associated genes by immunoblotting and quantitative real-time polymerase chain reaction. LFE and 5-FU synergistically inhibited cell proliferation of HT-29 and Colo 320DM cells. Combined treatment also elevated the level of loss of mitochondria membrane potential of these two CRC cells and arrested HT-29 cells in the S phase of the cell cycle, in association with down-regulation of cyclin A mRNA expression. LFE synergistically potentiated chemosensitivity to 5-FU in at least two CRC cell lines. The results indicated that LFE has potential as a novel agent for the sensitization of CRC cells to 5-FU.

Oncogenic PITX2 facilitates tumor cell drug resistance by inverse regulation of hOCT3/SLC22A3 and ABC drug transporters in colon and kidney cancers

Oncogenic pituitary homeobox 2 (PITX2), a de facto master regulator of developmental organ asymmetry, previously upregulated multidrug resistance (MDR) P-glycoprotein ABCB1 in A498 renal cell carcinoma (RCC) cells. The role of PITX2 isoforms in MDR cancers was investigated. Data mining correlated elevated PITX2 in >30% of cancers analyzed, maximally in colon (4.4-fold), confirmed in co-immunostaining of colon and renal cancer microarrays wherein ABCB1 concomitantly increased in RCC. Drug-resistant colorectal adenocarcinoma Colo320DM cells exhibited increased nuclear PITX2 (40-fold), PITX2 promoter activity (27-fold) and ABCB1 (8000-fold) compared to drug-sensitive Colo205. ABCB1 inhibitor PSC833/valspodar or PITX2 siRNA reversed doxorubicin resistance. Nuclei from Colo320DM and A498 cells harbored PITX2A/B1 and PITX2A/B1/B2/Cα/Cβ, respectively. ChIP-qPCR evidenced PITX2 promoter binding in drug exporters ABCB1, ABCC1, ABCG2 and importer hOCT3/SLC22A3. In A498, 786-O, Caki-1, Colo320DM, and Caco2 cells, PITX2 siRNA diminished exporters, increased hOCT3/SLC22A3 expression and activity, and reverted vincristine resistance. Heterologous PITX2 expression induced ABCB1, repressed hOCT3/SLC22A3, enhanced vincristine resistance and diminished proliferation inhibition wherein PITX2A and PITX2C were most effective. Furthermore, PITX2 activity and MDR depended on phosphorylation by GSK3 in A498 cells. Conclusively, oncogenic PITX2 limits sensitizing drug uptake and potentiates cytoprotective drug efflux, contributing to MDR phenotype.

Abstract 5873: BAY-3827, a selective inhibitor of AMPK for the evaluation of the role of AMPK in Myc-dependent tumors

Abstract The AMP-activated protein kinase (AMPK) is a sensor of the energy status in the cells, playing a key role in controlling their metabolism. For many years, AMPK was mainly perceived as a tumor suppressor in agreement with being a component of the LKB1 tumor suppressor cascade, which inhibits mTORC1. However, in the last few years, some studies suggested that AMPK might actually exert a pro-tumorigenic role in certain contexts. For instance, Liu and colleagues demonstrated that dysregulated MYC expression renders tumor cells sensitive to AMPK depletion (Liu et al, 2012. Nature). The authors showed that, due to their increased anabolism, MYC-dependent cells rely on AMPK to restore ATP levels and to prevent an energy crisis that results in apoptosis and cell death. Here we report the discovery of a new lead structure for the inhibition of AMPK by biochemical high throughput screening. The optimization of this lead structure towards potency and selectivity led to the probe compound BAY-3827 and the use of this tool compound to evaluate the therapeutic potential of AMPK inhibition in MYC-dependent tumors. To demonstrate a cellular effect of BAY-3827 an HRTF® assay (Homogeneous Time Resolved Fluorescence, cisbio) for phospho-Acetyl-CoA carboxylase (p-ACC, Ser79), a direct substrate of AMPK, was used. ACC phosphorylation was strongly inhibited by BAY-3827 in COLO 320DM and IMR-32 cells. However, despite its high potency, BAY-3827 failed to inhibit the proliferation of cells with dysregulated c-MYC or N-MYC. In conclusion, we have identified a potent and selective AMPK inhibitor. Despite demonstrated inhibition of AMPK kinase activity, BAY-3827 treatment did not translate into antiproliferative activity in MYC-dependent cells. While we could not confirm our initial hypothesis, one might speculate that inhibition of AMPK might be of therapeutic utility in other biological contexts. Therefore, the availability of potent and selective inhibitors, as described here, will contribute to further insight into the potential of AMPK inhibition as a therapeutic target in cancer. Citation Format: Clara Lemos, Volker K. Schulze, Benjamin Bader, Clara D. Christ, Hans Briem, Oliver Politz, Florian Prinz, Simon Holton, Tobias Heinrich, Julien Lefranc, Philip Lienau, Arne Scholz, Franz von Nussbaum, Carl Friedrich Nising, Dominik Mumberg, Marcus Bauser, Andrea Hägebarth. BAY-3827, a selective inhibitor of AMPK for the evaluation of the role of AMPK in Myc-dependent tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5873.

MTOR signaling mediates resistance to tankyrase inhibitors in Wnt-driven colorectal cancer.

Activation of Wnt/β-catenin signaling is essential for colorectal carcinogenesis. Tankyrase, a member of the poly(ADP-ribose) polymerase (PARP) family, is a positive regulator of the Wnt/β-catenin signaling. Accordingly, tankyrase inhibitors are under preclinical development for colorectal cancer (CRC) therapy. However, Wnt-driven colorectal cancer cells are not equally sensitive to tankyrase inhibitors, and cellular factors that affect tankyrase inhibitor sensitivity remain elusive. Here, we established a tankyrase inhibitor-resistant cell line, 320-IWR, from Wnt/β-catenin-dependent CRC COLO-320DM cells. 320-IWR cells exhibited resistance to tankyrase inhibitors, IWR-1 and G007-LK, but remained sensitive to a PARP-1/2 inhibitor, olaparib, and several anti-CRC agents. In 320-IWR cells, nuclear localization of active β-catenin was decreased and expression of β-catenin target genes was constitutively repressed, suggesting that these cells repressed the Wnt/β-catenin signaling and were dependent on alternative proliferation pathways. 320-IWR cells exhibited upregulated mTOR signaling and were more sensitive to mTOR inhibition than the parental cells. Importantly, mTOR inhibition reversed resistance to tankyrase inhibitors and potentiated their anti-proliferative effects in 320-IWR cells as well as in CRC cell lines in which the mTOR pathway was intrinsically activated. These results indicate that mTOR signaling confers resistance to tankyrase inhibitors in CRC cells and suggest that the combination of tankyrase and mTOR inhibitors would be a useful therapeutic approach for a subset of CRCs.

Amplification of a transgene within a long array of replication origins favors higher gene expression in animal cells.

Plasmids with both a mammalian replication initiation region (IR) and a matrix attachment region (MAR) are spontaneously amplified in transfected cells, and generate extrachromosomal double minute (DM) or chromosomal homogeneously staining region (HSR). We previously isolated the shortest core IR (G5) required for gene amplification. In this study, we ligated the G5 DNA to create direct or inverted repeats, mixed the repeats with an expression plasmid, and transfected the mixture into human COLO 320DM or hamster CHO DG44 cells. Consequently, we found that the transfected sequence generated DMs or HSR where, surprisingly, the plasmid sequence was embedded within a long stretch of G5 sequences. The amplified structure from the direct G5 repeats was stable, whereas that from the inverted repeats was not. The amplification might be explained by the efficient replication/multimerization of the G5 repeat and recombination with the co-transfected plasmid in an extrachromosomal context. The product might then be integrated into a chromosome arm to generate a HSR. The expression from the plasmid within the long G5 array was much higher than that from a simple plasmid repeat. Because G5 is a core IR that favors gene expression, a long array of G5 provides an excellent environment for gene expression from the embedded plasmid.

Curcumin inhibits growth potential by G1 cell cycle arrest and induces apoptosis in p53-mutated COLO 320DM human colon adenocarcinoma cells

Curcumin, a natural polyphenolic compound and it is isolated from the rhizome of Curcuma longa, have been reported to possess anticancer effect against stage I and II colon cancer. However, the effect of curcumin on colon cancer at Dukes’ type C metastatic stage III remains still unclear. In the present study, we have investigated the anticancer effects of curcumin on p53 mutated COLO 320DM human colon adenocarcinoma cells derived from Dukes’ type C metastatic stage. The cellular viability and proliferation were assessed by trypan blue exclusion assay and MTT assay, respectively. The cytotoxicity effect was examined by lactate dehydrogenase (LDH) cytotoxicity assay. Apoptosis was analyzed by DNA fragmentation analysis, Hoechst and propidium iodide double fluorescent staining and confocal microscopy analysis. Cell cycle distribution was performed by flow cytometry analysis. Here we have observed that curcumin treatment significantly inhibited the cellular viability and proliferation potential of p53 mutated COLO 320DM cells in a dose- and time-dependent manner. In addition, curcumin treatment showed no cytotoxic effects to the COLO 320DM cells. DNA fragmentation analysis, Hoechst and propidium iodide double fluorescent staining and confocal microscopy analysis revealed that curcumin treatment induced apoptosis in COLO 320DM cells. Furthermore, curcumin caused cell cycle arrest at the G1 phase, decreased the cell population in the S phase and induced apoptosis in COLO 320DM colon adenocarcinoma cells. Together, these data suggest that curcumin exerts anticancer effects and induces apoptosis in p53 mutated COLO 320DM human colon adenocarcinoma cells derived from Dukes’ type C metastatic stage.

TET1 Depletion Induces Aberrant CpG Methylation in Colorectal Cancer Cells.

Aberrant DNA methylation is commonly observed in colorectal cancer (CRC), but the underlying mechanism is not fully understood. 5-hydroxymethylcytosine levels and TET1 expression are both reduced in CRC, while epigenetic silencing of TET1 is reportedly associated with the CpG island methylator phenotype. In the present study, we aimed to clarify the relationship between loss of TET1 and aberrant DNA methylation in CRC. Stable TET1 knockdown clones were established using Colo320DM cells, which express high levels of TET1, and HCT116 cells, which express TET1 at a level similar to that in normal colonic tissue. Infinium HumanMethylation450 BeadChip assays revealed increased levels of 5-methylcytosine at more than 10,000 CpG sites in TET1-depleted Colo320DM cells. Changes in DNA methylation were observed at various positions within the genome, including promoters, gene bodies and intergenic regions, and the altered methylation affected expression of a subset of genes. By contrast, TET1 knockdown did not significantly affect DNA methylation in HCT116 cells. However, TET1 depletion was associated with attenuated effects of 5-aza-2’-deoxycytidine on gene expression profiles in both cell lines. These results suggest that loss of TET1 may induce aberrant DNA methylation and may attenuate the effect of 5-aza-2’-deoxycytidine in CRC cells.

Pro-survival responses to the dual inhibition of anti-apoptotic Bcl-2 family proteins and mTOR-mediated signaling in hypoxic colorectal carcinoma cells.

BackgroundThe use of targeted agents to impel dual inhibition of anti-apoptotic mechanisms and mTOR-mediated pro-survival signaling in colorectal carcinoma (CRC) cell lines with KRAS or BRAF mutation has been shown to induce apoptosis, a timely result given CRC entities harboring such mutations are in need of new therapies. Since CRC comprises heterogeneous tumors with predominant hypoxic components, we investigated effects of an inhibitor of anti-apoptotic Bcl-2 family proteins (ABT-737) in combination with an mTOR inhibitor (AZD8055)—collectively referred to as combo-Rx, in hypoxic CRC cell lines.MethodsCell viability measures, expression of proteins implicated in apoptosis and MAPK/PI3K-AKT/mTOR pathway signaling, and profiling of composite kinase activities were undertaken in a panel of 14 cell lines.ResultsIn hypoxic conditions, combo-Rx suppressed viability of 13 of the cell lines, albeit ABT-737 did not significantly potentiate the inhibitory effect of single-agent AZD8055 in six of the models. Hypoxic KRAS/PIK3CA-mutant HCT-116 and HCT-15 cell lines (both with low endogenous expression of the anti-apoptotic Mcl-1 protein and showing augmented inhibition of viability following the addition of ABT-737 to AZD8055) responded to combo-Rx by induction of apoptosis but with the simultaneous strong Mcl-1 up-regulation and activation of MAPK/PI3K-conducted signaling. In contrast, in hypoxic KRAS-mutant LoVo (devoid of PIK3CA mutation), BRAF/PIK3CA-mutant RKO, and wild-type Colo320DM cell lines (all with high endogenous Mcl-1 expression and being resistant to the additional effect of ABT-737 to AZD8055), combo-Rx did not elicit apoptotic or pro-survival responses.ConclusionsThe concurrent inhibition of anti-apoptotic proteins and mTOR-mediated signaling in hypoxic KRAS/PIK3CA-mutant CRC cell lines resulted in pro-survival responses in parallel with the intended anti-proliferative effects, a finding that should be of note if considering combinatory targeting of multiple pathways in this CRC entity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-016-2600-y) contains supplementary material, which is available to authorized users.

The Discovery and Characterization of K-756, a Novel Wnt/β-Catenin Pathway Inhibitor Targeting Tankyrase.

The Wnt/β-catenin pathway is a well-known oncogenic pathway. Its suppression has long been considered as an important challenge in treating cancer patients. Among colon cancer patients in particular, most patients carry an adenomatous polyposis coli (APC) mutation that leads to an aberration of Wnt/β-catenin pathway. To discover the small molecule inhibitors of the Wnt/β-catenin pathway, we conducted high-throughput screening in APC-mutant colon cancer DLD-1 cells using a transcriptional reporter assay, which identified a selective Wnt/β-catenin pathway inhibitor, K-756. K-756 stabilizes Axin and reduces active β-catenin, and inhibits the genes downstream of endogenous Wnt/β-catenin. We subsequently identified that K-756 is a tankyrase (TNKS) inhibitor. TNKS, which belongs to the PARP family, poly-ADP ribosylates Axin and promotes Axin degradation via the proteasome pathway. K-756 binds to the induced pocket of TNKS and inhibits its enzyme activity. Moreover, PARP family enzyme assays showed that K-756 is a selective TNKS inhibitor. K-756 inhibited the cell growth of APC-mutant colorectal cancer COLO 320DM and SW403 cells by inhibiting the Wnt/β-catenin pathway. An in vivo study showed that the oral administration of K-756 inhibited the Wnt/β-catenin pathway in colon cancer xenografts in mice. To further explore the therapeutic potential of K-756, we also evaluated the effects of K-756 in non-small cell lung cancer cells. Although a single treatment of K-756 did not induce antiproliferative activity, when K-756 was combined with an EGFR inhibitor (gefitinib), it showed a strong synergistic effect. Therefore, K-756, a novel selective TNKS inhibitor, could be a leading compound in the development of anticancer agents. Mol Cancer Ther; 15(7); 1525-34. ©2016 AACR.

Upregulation of the Multidrug Resistance P‐glycoprotein ABCB1 by Transcription Factor Pituitary Homeobox 2 (Pitx2) in Human Colon and Kidney Cancers

BackgroundPituitary homeobox 2 (Pitx2) is a master regulator of organ asymmetry during development but is reactivated in neoplastic cells, contributing to cell proliferation, tumor cell invasion and cancer progression. Upregulation of the multidrug resistance P‐glycoprotein ABCB1 confers chemotherapeutic drug resistance to tumor cells, hampering effective treatment. We have previously shown that Pitx2 is upregulated in a multidrug resistant (MDR) kidney cancer cell line and serves as a positive transcriptional regulator of ABCB1 thereby increasing resistance to the anthracycline chemotherapeutic drug, doxorubicin (DOX) (Lee, W.‐K. et al. Int J Cancer 113, 556–67, 2013). The objective of this study was to determine if ABCB1 regulation by Pitx2 is also in engaged by other cancer types that exhibit intrinsic MDR.MethodsExpression of Pitx2 and ABCB1 was determined by immunofluorescence microscopy, immunoblotting and immunohistochemistry. Cell viability was assessed by MTT and clonogenic survival assays. Pitx2 transcriptional activity was measured by luciferase reporter gene assay. Isolation of nuclei was performed by Tenbroeck homogenization in hypoosmotic buffer and a discontinuous sucrose gradient.ResultsIn human colorectal adenocarcinoma Colo320DM cells, which exhibit MDR and harbor augmented ABCB1 expression, nuclear Pitx2 expression and Pitx2 reporter gene activity were significantly increased compared to less drug resistant Colo205 cells. The ABCB1 inhibitor PSC833 (0.1 μM) reversed drug resistance to 1 μM DOX after 24 h in Colo320DM cells. Further, knockdown of Pitx2 by RNAi in Colo320DM cells resulted in decreased ABCB1 protein by almost 3‐fold and diminished resistance to DOX resulting in attenuated cell survival. Moreover, the Pitx2 isoforms that are involved in regulation of ABCB1 in colon and kidney cancer cells were investigated. Both Pitx2A and Pitx2B were found to be present in the nuclear fraction of Colo320DM and MDR A498 kidney carcinoma cells. Analysis of human kidney and colon cancer tissue arrays by co‐immunostaining suggests a causal relationship between nuclear Pitx2 and ABCB1 expression.ConclusionPitx2 is a transcriptional regulator of ABCB1 in cancers of the colon and kidney suggesting a contributory role to the MDR phenotype.Support or Funding InformationFunded by an Internal Research Grant (UW/H) and ZBAF

Role of OATP2A1 in PGE2 secretion from human colorectal cancer cells via exocytosis in response to oxidative stress

Chronic inflammation induced by reactive oxygen species is associated with increased risk of developing colorectal cancer (CRC), and prostaglandin E2 (PGE2), which serves as a key mediator of inflammatory responses, plays an important role in CRC initiation and progression. Therefore, in the present study, we aimed to investigate the role of prostaglandin transporter OATP2A1/SLCO2A1 in the changes of PGE2 disposition in CRC cells in response to oxidative stress. H2O2 induced translocation of cytoplasmic OATP2A1 to plasma membranes in LoVo and COLO 320DM cells, but not in Caco-2 cells. The shift of subcellular OATP2A1 was abolished in the presence of anti-oxidant N-acetyl-L-cysteine or an inhibitor of protein kinase C, which evokes exocytosis. Exposure of LoVo cells to H2O2 caused an increase in the amount of extracellular PGE2 without changing the sum of intra- and extracellular PGE2. OATP2A1 knockdown decreased extracellular PGE2 in LoVo cells. In addition, extracellular PGE2 was significantly reduced by exocytosis inhibitor cytochalasin D, suggesting that H2O2-induced PGE2 release occurs in an exocytotic manner. Furthermore, mRNA expression of vascular endothelial growth factor (VEGF) was significantly reduced in LoVo cells by knockdown of OATP2A1. These results suggest that cytoplasmic OATP2A1 likely facilitates PGE2 loading into suitable intracellular compartment(s) for efficient exocytotic PGE2 release from CRC cells exposed to oxidative stress.

TP53 status regulates ACSL5-induced expression of mitochondrial mortalin in enterocytes and colorectal adenocarcinomas

Acyl-CoA synthetase 5 (ACSL5), a mitochondrially localized enzyme, catalyzes the synthesis of long-chain fatty acid thioesters and is physiologically involved in pro-apoptotic sensing of enterocytes. The aim of the present study is to identify an ACSL5-dependent regulation of mitochondrially expressed proteins and the characterization of related pathways in normal and diseased human intestinal mucosa. Proteomics of isolated mitochondria from ACSL5 transfectants and CaCo2 controls were performed. ACSL5-dependent protein synthesis was verified with quantitative reverse transcription plus the polymerase chain reaction, Western blotting, short-interfering-RNA-mediated gene silencing and additional cell culture experiments. Lipid changes were analyzed with tandem mass spectrometry. ACSL5-related pathways were characterized in normal mucosa and sporadic adenocarcinomas of the human intestine. In CaCo2 cells transfected with ACSL5, mortalin (HSPA9) was about two-fold increased in mitochondria, whereas cytoplasmic mortalin levels were unchanged. Disturbance of acyl-CoA/sphingolipid metabolism, induced by ACSL5 over-expression, was characterized as crucial. ACSL5-related over-expression of mitochondrial mortalin was found in HEK293 and Lovo (wild-type TP53 [tumor protein p53]) and CaCo2 (p53-negative; TP53 mutated) cells but not in Colo320DM cells (mutated TP53). In normal human intestinal mucosa, an increasing gradient of both ACSL5 and mortalin from bottom to top was observed, whereas p53 (wild-type TP53) decreased. In sporadic intestinal adenocarcinomas with strong p53 immunostaining (mutated TP53), ACSL5-related mortalin expression was heterogeneous. ACSL5-induced mitochondrial mortalin expression is assumed to be a stress response to ACSL5-related changes in lipid metabolism and is regulated by the TP53 status. Uncoupling of ACSL5 and mitochondrial mortalin by mutated TP53 could be important in colorectal carcinogenesis.

A novel pathway by which the environmental toxin 4-Nonylphenol may promote an inflammatory response in inflammatory bowel disease

Background4-Nonylphenol is a ubiquitous environmental toxin that is formed as a byproduct in the manufacturing and/or sewage treatment of regular household items. Previous work in our lab has implicated 4-NP in the progression of autoimmune diseases such as inflammatory bowel disease in which macrophages mistakenly attack the intestinal linings, causing chronic inflammation. Several key pro-and anti-inflammatory molecules have been shown to be involved in the manifestation of this disease, including IL-23A, COX-2, IL-8, TLR-4, and IL-10.Material/Methods4-NP’s effects on these known mediators of IBD were effectively analyzed using a novel model for IBD, by which 4-NP may promote an inflammatory response. Data were collected using DNA Microarray, RT-PCR, and ELISA, after 48 hour treatment of U937 histiocytic lymphocyte cells and COLO320DM human intestinal epithelial cells with 1 nM and 5 nM concentrations of 4-NP.ResultsSignificant dysregulation of the expression of both pro- and anti-inflammatory genes was observed in U937 cells that would promote and prolong inflammation. However, TLR-4, IL-8, and COX-2 gene expressions showed unprecedented effects in COLO320DM cells suggesting that these genes mediate apoptotic processes within the gastrointestinal tract.ConclusionsOverall, our results suggest that 4-NP administration engenders immune responses linked to apoptotic processes via dysregulation of macrophage signaling. In sum, 4-NP appears to increases the risk of developing inflammatory bowel disease by promoting or prolonging adverse progression of inflammation in the gastrointestinal tract.

The Intermediate Conductance Calcium-activated Potassium Channel KCa3.1 Regulates Vascular Smooth Muscle Cell Proliferation via Controlling Calcium-dependent Signaling

The intermediate conductance calcium-activated potassium channel KCa3.1 contributes to a variety of cell activation processes in pathologies such as inflammation, carcinogenesis, and vascular remodeling. We examined the electrophysiological and transcriptional mechanisms by which KCa3.1 regulates vascular smooth muscle cell (VSMC) proliferation. Platelet-derived growth factor-BB (PDGF)-induced proliferation of human coronary artery VSMCs was attenuated by lowering intracellular Ca(2+) concentration ([Ca(2+)]i) and was enhanced by elevating [Ca(2+)]i. KCa3.1 blockade or knockdown inhibited proliferation by suppressing the rise in [Ca(2+)]i and attenuating the expression of phosphorylated cAMP-response element-binding protein (CREB), c-Fos, and neuron-derived orphan receptor-1 (NOR-1). This antiproliferative effect was abolished by elevating [Ca(2+)]i. KCa3.1 overexpression induced VSMC proliferation, and potentiated PDGF-induced proliferation, by inducing CREB phosphorylation, c-Fos, and NOR-1. Pharmacological stimulation of KCa3.1 unexpectedly suppressed proliferation by abolishing the expression and activity of KCa3.1 and PDGF β-receptors and inhibiting the rise in [Ca(2+)]i. The stimulation also attenuated the levels of phosphorylated CREB, c-Fos, and cyclin expression. After KCa3.1 blockade, the characteristic round shape of VSMCs expressing high l-caldesmon and low calponin-1 (dedifferentiation state) was maintained, whereas KCa3.1 stimulation induced a spindle-shaped cellular appearance, with low l-caldesmon and high calponin-1. In conclusion, KCa3.1 plays an important role in VSMC proliferation via controlling Ca(2+)-dependent signaling pathways, and its modulation may therefore constitute a new therapeutic target for cell proliferative diseases such as atherosclerosis.