Response Of Colon Cancer Cells Research Articles

The Expression of LINC00673 in Colon Cancer and the Melatonin's Effect on Its Expression

Objective: In this study, the cell lines SW620 and DLD-1 which belongs to colon cancer were employed with the aim of observing melatonin's effect on the growth of colon cancer cells and exploring the influence of melatonin about the autophagy of colon cancer. Besides. It uses qRT-PCR to identify LINCRNA00673 (LINC00673) expression in colon cancer and the influence of melatonin on LINC00673 expression.For the purpose of providing a fundamental theory for melatonin in anti-cancer therapy and also presenting as a biomarker for the early detection of colon cancer. Method: 1) Cultivating the colon cancer cell lines SW620 and DLD-1, and subdividing them in accordance with distinct concentrations of melatonin: 0 mM, 1mM, and 2mM, to detect the impact of melatonin for migration and growth of colon cancer cells by Cell Scratch Test and Colony Formation Assay.2) Detecting the expression level of autophagy-related molecules in colon cancer cells in response to melatonin employing Western Blot Assay. 3) Utilizing QT-PCR, extract RNA from two groups of cells and detect the expression of LINC00673 and LINC00673 following melatonin treatment. Result: 1) The Cell Scratch test and Colony Formation Assay indicated that compared with the normal group, the scratch healing of SW620 cells and DLD-1 cells decreased. Furthermore, following melatonin administration, the number of cell colonies decreased. And the results are statistically significant. 2) Western blotting results illustrated that after the interferon of melatonin, the expression level of the autophagy-related molecule Beclin-1 increased significantly, whereas the expression of P62 decreased. 3) QT-PCR results demonstrated that the expression of LINC00673 in colon cancer cells SW620 and DLD-1 was significantly increased. Moreover, melatonin had an inhibiting effect on it. Conclusion: These in vitro experiments managed to prove that melatonin possesses a powerful anti-colon cancer effect and can inhibit the growth and spread of colon cancer. Western blotting indicated that melatonin can inhibit colon cancer through autophagy. Besides which, it is discovered that melatonin may exert its anticancer effect by influencing LINC00673.

Effect of TP53 deficiency and KRAS signaling on the bioenergetics of colon cancer cells in response to different substrates: A single cell study.

Metabolic reprogramming is a hallmark of cancer. Somatic mutations in genes involved in oncogenic signaling pathways, including KRAS and TP53, rewire the metabolic machinery in cancer cells. We here set out to determine, at the single cell level, metabolic signatures in human colon cancer cells engineered to express combinations of activating KRAS gene mutations and TP53 gene deletions. Specifically, we explored how somatic mutations in these genes and substrate availability (lactate, glucose, substrate deprivation) from the extracellular microenvironment affect bioenergetic parameters, including cellular ATP, NADH and mitochondrial membrane potential dynamics. Employing cytosolic and mitochondrial FRET-based ATP probes, fluorescent NADH sensors, and the membrane-permeant cationic fluorescent probe TMRM in HCT-116 cells as a model system, we observed that TP53 deletion and KRAS mutations drive a shift in metabolic signatures enabling lactate to become an efficient metabolite to replenish both ATP and NADH following nutrient deprivation. Intriguingly, cytosolic, mitochondrial and overall cellular ATP measurements revealed that, in WT KRAS cells, TP53 deficiency leads to an enhanced ATP production in the presence of extracellular lactate and glucose, and to the greatest increase in ATP following a starvation period. On the other hand, oncogenic KRAS in TP53-deficient cells reversed the alterations in cellular ATP levels. Moreover, cell population measurements of mitochondrial and glycolytic metabolism using a Seahorse analyzer demonstrated that WT KRAS TP53-silenced cells display an increase of the basal respiration and tightly-coupled mitochondria, in the presence of glucose as substrate, compared to TP53 competent cells. Furthermore, cells possessing oncogenic KRAS, independently of TP53 status, showed less pronounced mitochondrial membrane potential changes in response to metabolic nutrients. Furthermore, analysis of cytosolic and mitochondrial NADH levels revealed that the simultaneous presence of TP53 deletion and oncogenic KRAS showed the most pronounced alteration in cytosolic and mitochondrial NADH during metabolic stress. In conclusion, our findings demonstrate how activating KRAS mutation and loss of TP53 remodel cancer metabolism and lead to alterations in bioenergetics under metabolic stress conditions by modulating cellular ATP production, NADH oxidation, mitochondrial respiration and function.

Proteasome inhibitors restore the STAT1 pathway and enhance the expression of MHC class I on human colon cancer cells

BackgroundA new strategy, particularly a novel combination, for immunotherapy in microsatellite stable metastatic colorectal cancer (mCRC) treatment needs to be formulated. Studies on the interferon-γ (IFN-γ)/ Janus kinase (JAK)/ signal transducer and activator of transcription (STAT)1 pathway provide new directions in this regard.MethodsOur study applies three colon cancer cell lines, including microsatellite stable (MSS) cell lines, which are SW480 and SW620, and microsatellite instability-high (MSI-H) cell line, which is DLD-1. We compared the expressions of immune surface markers on colon cancer cells in response to IFN-γ. We elucidated these mechanisms, which involved the upregulation of immune surface markers. Furthermore, we examined real-world clinical samples using the PerkinElmer Opal multiplex system and NanoString analysis.ResultsWe established that the baseline expression of major histocompatibility complex (MHC) class I alleles and programmed death-ligand 1 (PD-L1) were generally low in cell line models. The immune surface markers were significantly increased after IFN-γ stimulation on SW480 but were notably unresponsive on the SW620 cell line. We discovered that STAT1 and phosphorylated STAT1 (pSTAT1) were downregulated in the SW620 cell line. We verified that the STAT1/pSTAT1 could be restored through the application of proteasome inhibitors, especially bortezomib. The expression of MHC class I as downstream signals of STAT1 was also up-regulated by proteasome inhibitors. The similar results were reproduced in DLD-1 cell line, which was also initially unresponsive to IFN-γ. In real-world samples of patients with mCRC, we found that higher STAT1 expression in tumor cells was strongly indicative of a highly immunogenic microenvironment, with significantly higher expression levels of MHC class I and PD-L1, not only on tumor cells but also on non-tumor cells. Furthermore, tumor infiltrating lymphocytes (TILs) were increased in the positive-STAT1 group. Through NanoString analysis, we confirmed that the mRNA expressions of IFN-γ, human leukocyte antigen (HLA)-A, HLA-E, and HLA-G were also significantly higher in the positive-STAT1 group than those in the negative-STAT1 group.ConclusionOur study provides a novel rationale for the addition of bortezomib, a proteasome inhibitor, into new immunotherapy combinations.

Ferritinophagy is not required for colon cancer cell growth.

Ferritinophagy is a form of selective autophagy responsible for degrading intracellular ferritin, mediated by nuclear receptor coactivator 4 (NCOA4). NCOA4 plays significant roles in systemic iron homeostasis, and its disruption leads to simultaneous anemia and susceptibility to iron overload. The importance of iron colorectal cancer pathogenesis is well studied; however, the role of ferritinophagy in colon cancer cell growth has not been assessed. Disruption of ferritinophagy via NCOA4 knockout leads to only marginal differences in growth under basal and iron-restricted conditions. Moreover, NCOA4 played no significant role in cell death induced by 5-fluorouracil and erastin. Western blotting analysis for ferritin and transferrin receptor 1 found a dose-dependent effect on expression in both proteins in wild-type and NCOA4 knockout cell lines, but further investigation revealed no difference in growth response when treated at both high and low doses. Our data demonstrate a marginal role for ferritinophagy in growth both under normal and cytotoxic conditions in colon cancer cells, as well as a possible compensatory mechanism in colon cancer cells in response to ferroptosis induction.

Hypoxia-induced upregulation of Orai1 drives colon cancer invasiveness and angiogenesis

In colon cancer, hypoxia promotes metastasis and angiogenesis, but little is known about the mediators of these effects. Here, we reported that expression of Orai1 is up-regulated in colon cancer cells in response to hypoxia, and the increase in Orai1 is mediated by Notch1 pathway. We also showed upregulation of Orai1 contributes to hypoxia-induced invasion and angiogenesis, and inhibition or downregulation of Orai1 reverses these effects. Mechanistic study revealed that upregulation of Orai1 by hypoxia potentiates store-operated Ca2+ entry (SOCE), and then causes activation of nuclear factor of activated T cells isoform c3 (NFATc3) in colon cancer cells. Furthermore, expression of Orai1 was correlated with tumor metastasis in patients. These results identify Orai1 as a novel target gene of hypoxia and reveal the role of Orai1 signaling in regulating hypoxia-induced invasiveness and angiogenesis under hypoxic conditions. Strategies to target this signaling might be developed to treat colon cancer metastasis and angiogenesis associated with hypoxia.

Epidermal growth factor-mediated Rab25 pathway regulates integrin \u03b21 trafficking in colon cancer

BackgroundIntegrins play a critical role in carcinogenesis. Integrin β1 localization is regulated by the guanosine-5′-triphosphate hydrolase Rab25 and integrin β1 levels are elevated in the serum of colon cancer patients; thus, the present study examined the effects of epidermal growth factor (EGF) and Rab25 on integrin β1 localization in colon cancer cells.MethodsHCT116 human colon cancer cells were treated with increasing concentrations of EGF, and cell proliferation and protein expression were monitored by MTT and western blot analyses, respectively. Cell fractionation was performed to determine integrin β1 localization in the membrane and cytosol. Integrin β1 extracellular shedding was monitored by enzyme-linked immunosorbent assays (ELISAs) with culture supernatants from stimulated cells. HCT116 cells were transfected with Rab25-specific siRNA to determine the significance of Rab25 in integrin β1 trafficking in the presence of EGF.ResultsTotal integrin β1 expression increased in response to EGF and subsequently decreased at 24 h post-stimulation. A similar decrease was observed in purified membrane fractions, whereas no changes were observed in cytosolic levels. ELISAs using media from stimulated cell cultures demonstrated increased integrin β1 levels corresponding to the decrease observed in membrane fractions, suggesting that EGF induces integrin receptor shedding. EGF stimulation in Rab25-knockdown cells resulted in integrin β1 accumulation in the membrane, suggesting that Rab25 promotes integrin endocytosis.ConclusionsIntegrin β1 is shed from colon cancer cells in response to EGF stimulation in a Rab25-dependent manner. These results further the present understanding of the role of integrin β1 in colon cancer progression.

Translationally controlled tumour protein TCTP is induced early in human colorectal tumours and contributes to the resistance of HCT116 colon cancer cells to 5-FU and oxaliplatin

BackgroundTranslationally controlled tumour protein TCTP is an anti-apoptotic protein frequently overexpressed in cancers, where high levels are often associated with poor patient outcome. TCTP may be involved in protecting cancer cells against the cytotoxic action of anti-cancer drugs. Here we study the early increase of TCTP levels in human colorectal cancer (CRC) and the regulation of TCTP expression in HCT116 colon cancer cells, in response to treatment with the anti-cancer drugs 5-FU and oxaliplatin.MethodsUsing immunohistochemistry, we assessed TCTP levels in surgical samples from adenomas and adenocarcinomas of the colon, compared to normal colon tissue. We also studied the regulation of TCTP in HCT116 colon cancer cells in response to 5-FU and oxaliplatin by western blotting. TCTP mRNA levels were assessed by RT-qPCR. We used mTOR kinase inhibitors to demonstrate mTOR-dependent translational regulation of TCTP under these conditions. Employing the Real-Time Cell Analysis (RTCA) System and the MTS assay, we investigated the effect of TCTP-knockdown on the sensitivity of HCT116 cells to the anti-cancer drugs 5-FU and oxaliplatin.Results1. TCTP levels are significantly increased in colon adenomas and adenocarcinomas, compared to normal colon tissue. 2. TCTP protein levels are about 4-fold upregulated in HCT116 colon cancer cells, in response to 5-FU and oxaliplatin treatment, whereas TCTP mRNA levels are down regulated. 3. mTOR kinase inhibitors prevented the up-regulation of TCTP protein, indicating that TCTP is translationally regulated through the mTOR complex 1 signalling pathway under these conditions. 4. Using two cellular assay systems, we demonstrated that TCTP-knockdown sensitises HCT116 cells to the cytotoxicity caused by 5-FU and oxaliplatin.ConclusionsOur results demonstrate that TCTP levels increase significantly in the early stages of CRC development. In colon cancer cells, expression of this protein is largely upregulated during treatment with the DNA-damaging anti-cancer drugs 5-FU and oxaliplatin, as part of the cellular stress response. TCTP may thus contribute to the development of anti-cancer drug resistance. These findings indicate that TCTP might be suitable as a biomarker and that combinatorial treatment using 5-FU/oxaliplatin, together with mTOR kinase inhibitors, could be a route to preventing the development of resistance to these drugs.

Endoplasmic reticulum stress and IRE-1 signaling cause apoptosis in colon cancer cells in response to andrographolide treatment.

The plant metabolite andrographolide induces cell cycle arrest and apoptosis in cancer cells. The mechanism(s) by which andrographolide induces apoptosis however, have not been elucidated. The present study was performed to determine the molecular events that promote apoptosis in andrographolide treated cells using T84, HCT116 and COLO 205 colon cancer cell lines. Andrographolide was determined to limit colony formation and Ki67 expression, alter nuclear morphology, increase cytoplasmic histone-associated-DNA-fragments, and increase cleaved caspase-3 levels. Andrographolide also induced significantly higher expression of endoplasmic reticulum (ER) stress proteins GRP-78 and IRE-1 by 48 h but not PERK or ATF6. Apoptosis signaling molecules BAX, spliced XBP-1 and CHOP were also significantly increased. Moreover, chemical inhibition of ER stress or IRE-1 depletion with siRNA in andrographolide treated cells significantly limited expression of IRE-1 and CHOP as determined by immunofluorescence staining, real time PCR, or immunobloting. This was accompanied by a decreased BAX/Bcl-2 ratio. Andrographolide significantly promotes cancer cell death compared to normal cells. These data demonstrate that andrographolide associated ER stress contributes to apoptosis through the activation of a pro-apoptotic GRP-78/IRE-1/XBP-1/CHOP signaling pathway.

Cell-to-Cell Variation in p53 Dynamics Leads to Fractional Killing

Many chemotherapeutic drugs kill only a fraction of cancer cells, limiting their efficacy. We used live-cell imaging to investigate the role of p53 dynamics in fractional killing of colon cancer cells in response to chemotherapy. We found that both surviving and dying cells reach similar levels of p53, indicating that cell death is not determined by a fixed p53 threshold. Instead, a cell's probability of death depends on the time and levels of p53. Cells must reach a threshold level of p53 to execute apoptosis, and this threshold increases with time. The increase in p53 apoptotic threshold is due to drug-dependent induction of anti-apoptotic genes, predominantly in the inhibitors of apoptosis (IAP) family. Our study underlines the importance of measuring the dynamics of key players in response to chemotherapy to determine mechanisms of resistance and optimize the timing of combination therapy.

Abstract 120: Runx3 inhibited epithelial to mesenchymal transition promotes motility and invasiveness of colon cancer cells through reduction of ROS generation

Abstract Approximately 90% of all cancer deaths arise from the metastatic spread of primary tumours. Most colon cancer metastasis occurs. Runx3(runt-related transcription factor3) is known as tumor suppressor gene in gastrointestinal epithelium. Recent reports have been shown that loss of Runx3 induce proliferative effect in gastric cancer cells. However, their roles and underlying mechanism in colon cancer cell lines are not yet known. In this study, we investigated the function of Runx3 in human colon cancer cells. The proliferation, migration, and invasion of colon cancer cells in response to using the Runx3 expression vector for various times were investigated using MTT, wound healing, and Matrigel invasion assay, respectively. The morphologic changes of colon cancer cells through the EMT process were monitored by immunofluorescence staining and Western blot assay for EMT markers Twist and Vimentin. We found that Runx3 overexpressing cell inhibited cell motility and invasiveness in colon cancer, and this process was enhanced by Runx3 siRNA. We observed that the mRNA expressions of Runx3 was enhanced by Runx3 overexpressing cell, whereas no increase of these factors was observed when the Runx3 siRNA was transfection. Overexpression of Runx3 decreases protein expression of EMT (Epithelial-Mesenchymal transition) markers. In addition, Runx3 knockdown upregulates MMP2 activity. The ROS production was decreased in Runx3-overexpressing cells. These results indicate that Runx3 signaling pathway can contribute to ROS generation enhancing the metastatic potential of tumor cells. Our findings suggest that Runx3 signaling processes through ROS and MMP2 the inhibition of these pathway blocked the metastatic potential of colon cancer cell lines. Citation Format: Bo Ram Kim, Myoung Hee Kang, Jung Lim Kim, Yoo Jin Jang, Sun Il Lee, Jun Suk Kim, Sang Cheul Oh. Runx3 inhibited epithelial to mesenchymal transition promotes motility and invasiveness of colon cancer cells through reduction of ROS generation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 120. doi:10.1158/1538-7445.AM2014-120

Abstract 3042: Investigating microRNA expression profiles in colon cancer cells in response to cyclooxygenase 2 signaling

Abstract MicroRNAs (miRNAs) are emerging as central players in cancer progression. Aberrant expression of miRNAs leads to malignant transformation and correlates with staging, progression and prognosis of cancers. Unfortunately, signaling pathways leading to altered expression of miRNAs are largely unknown. During early development of colon cancer, the expression of cyclooxygenase 2 (COX-2) is constitutively induced. We and others have shown that constitutive expression of COX-2 promotes colon carcinogenesis. However, the underlying mechanisms are not completely understood. To determine if COX-2 signaling alters expression of miRNAs, we used the Human Cancer RT2-miRNA PCR arrays to profile miRNA expression in HCA-7 human colon cancer cells treated with or without the COX-2 selective inhibitor NS-398. HCA-7 cells constitutively express endogenous COX-2. We found that expression levels of 39 miRNAs are different in HCA-7 cells as compared to HCA-7 cells treated with NS-398; 8 miRNAs were up-regulated and 31 miRNAs were down-regulated. To confirm the data from the PCR array, we used quantitative RT-PCR to quantify expression of 8 miRNAs in HCA-7 cells with or without NS-398 treatment. These 8 miRNAs were selected due to their relevance to cancer invasion and metastasis. We also compared the expression of these miRNAs in HCT-15 human colon cancer cells that were engineered to stably express COX-2 (HCT-15-COX-2) to the parental HCT-15 cells. Expression levels of 6 of the 8 examined miRNAs (miR-23b, 124, 146b-5p, 155, 183, 184) were significantly lower in HCT-15-COX-2 or HCA-7 cells than in parental HCT-15 or HCA-7 cells that were treated with NS-398. Therefore, we identified 6 miRNAs that are modulated by COX-2 and may play a role in mediating COX-2 signaling to promote colon carcinogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3042.

Comparative proteomic analysis of colon cancer cells in response to Oxaliplatin treatment

Colon cancer is one of the most common malignancies in the world. Oxaliplatin, a third-generation platinum compound, is widely used in clinical chemotherapy of colon cancer. Although the mechanisms of the antitumor effect of Oxaliplatin have been investigated in recent years, the proteomic changes that are associated with the cellular response to this compound are poorly understood. In this study, we performed a comparative proteomic analysis to survey the global changes in protein expression levels after Oxaliplatin treatment in three colon cancer cell lines: HT29, SW620, and LoVo. Two-dimensional gel electrophoresis coupled with MALDI-TOF/TOF mass spectrometry revealed 57, 48, and 53 differentially expressed proteins in the three cell lines (HT29, SW620 and LoVo, respectively) after Oxaliplatin treatment. Of these proteins, 21 overlapped among all three cell lines. These overlapping proteins participate in many cellular processes, such as apoptosis, signal transduction, transcription and translation, cell structural organization, and metabolism. Additionally, the expression levels of ezrin (EZRI), heat-shock protein beta-1 (HSPB1), translationally controlled tumor protein (TCTP), and cell division control protein 2 homolog (CDC2) were confirmed by immunoblotting. This is the first direct proteomic analysis of Oxaliplatin-treated colon cancer cells. Several interesting proteins that we found warrant further investigation owing to their potential significant functions in the antitumor effect of Oxaliplatin.

Wild‐type APC regulates caveolin‐1 expression in human colon adenocarcinoma cell lines via FOXO1a and C‐myc

Genetic evidence suggests that caveolin-1, an essential component of membrane caveolae, acts as a tumor promoter in some, and a tumor suppressor in other cancers. The role of caveolin-1 in colon carcinogenesis is controversial. We report here, for the first time, that caveolin-1 is transcriptionally induced in colon cancer cells in response to conditional expression of a full length adenomatous polyposis coli (APC) gene. This induction of caveolin-1 by APC is mediated by both FOXO1a, a member of the Forkhead family of transcription factor, and c-myc. The FOXO1a protein, which is increased by wild-type APC expression, induces caveolin-1 promoter-reporter activity and binds directly to a FKHR consensus binding sequence in the caveolin-1 promoter. The c-myc protein, which is reduced in the presence of wild-type APC, acts to repress caveolin-1 expression by acting at non-E-box containing elements in the caveolin-1 promoter. These data predict that caveolin-1 protein expression would be decreased early in colonic carcinogenesis, which is associated with loss of wild-type APC. Our results would be consistent with the interpretation that caveolin-1 may have tumor suppressing functions during early stages of colon carcinogenesis.

M1621 Gene Expression Profile in Colon Cancer Cells in Response to Troglitazone: Impact of XIAP Expression

M1621 Gene Expression Profile in Colon Cancer Cells in Response to Troglitazone: Impact of XIAP Expression

Resveratrol Phenocopies the Suppressive Effects of Insulin‐like Growth Factor Receptor‐1 siRNA on IGF‐1 Promoted Colon Cancer Cell Proliferation

The insulin‐like growth factor (IGF) system is believed to mediate obesity‐related increase in the risk of colon cancer. IGFs activate the β‐catenin pathway, which plays a central role in the growth of colon cancer cells. Dietary resveratrol exerts inhibitory effects on cancers; however, its molecular mechanisms are not fully elucidated, particularly in relation to obesity‐promoted cancers. We hypothesized that resveratrol suppresses colon cancer cell proliferation by inhibiting activation of IGF receptor‐1 (IGF‐1R) in response to IGFs (elevated during obesity). IGF‐1 (10 nM) promoted proliferation of colon cancer cells, in vitro, as expected. Resveratrol (50–150 μM) or IGF‐1R siRNA (100 nM) inhibited (p < 0.05) proliferation of colon cancer cells in response to both exogenous and autocrine IGFs. The relative levels of IGF‐1R were reduced (p < 0.05) in cells treated with either resveratrol or IGF‐1R siRNA, in association with a loss (p < 0.05) in Akt activation, GSK3β phosphorylation, and cyclin D1 levels. These results suggest that resveratrol effectively phenocopies the inhibitory properties of IGF‐1R siRNA and may thus be a potent chemopreventive/therapeutic agent against obesity‐associated increase in colon cancer risk. We will examine this possibility in future studies using in vivo models. Funded by TAES and AICR 058094.

Apoptosis, cell cycle progression and gene expression in TP53-depleted HCT116 colon cancer cells in response to short-term 5-fluorouracil treatment

Loss of TP53 function may contribute to 5-fluorouracil (5-FU) resistance in colorectal cancer since TP53-deficient cells may be unable to undergo apoptosis in response to 5-FU-induced DNA damage. 5-FU treatment of TP53-deficient cells would provide useful information on the apoptotic response to drug-induced DNA damage in the absence of TP53 and its transcriptional targets. We investigated apoptosis induction and cell cycle alterations in response to short-term treatment with two different 5-FU concentrations following siRNA-mediated knockdown of TP53 in the TP53-proficient HCT116 colon cancer cell line. We focused on high-dose 5-FU treatment to investigate the apoptotic phenotype in 5-FU-treated cultures since this dose resulted in apoptosis induction at 24 h of treatment, whereas clinically-relevant bolus 5-FU treatment of HCT116 cultures did not. Gene expression alterations were also assessed in 5-FU-treated HCT116 cultures using whole genome expression arrays. Compared to 5-FU-treated TP53-proficient HCT116 cultures, 5-FU-treated TP53-depleted HCT116 cultures showed lack of CDKN1A induction, decreased apoptotic levels, decreased FAS and TNFRSF10B transcript levels and cleaved PARP protein levels, G1/S transition arrests, decreased CCND1 protein levels, and smaller intra-S phase arrests. Alterations in gene expression in 5-FU-treated TP53-depleted HCT116 cultures confirmed previously-reported TP53 target genes and suggested potentially novel TP53 target genes (e.g. APOBEC3C, BIRC3, JMJD2B, LAMP3, MYO1E, PRRG1, SULF2, TACSTD2, TncRNA, ZFYVE20) that may play a role in mediating the 5-FU-induced DNA damage response in TP53-proficient cells. Abrogation of TP53 function in 5-FU-treated HCT116 cultures results in reduced apoptosis, TP53- and CDKN1A-independent G1/S phase arrests that may be protective against apoptosis, smaller intra-S phase arrests, and transcript level decreases of both reported TP53 target genes as well as potentially novel TP53 target genes.

The anti-apoptotic and growth stimulatory actions of leptin in human colon cancer cells involves activation of JNK mitogen activated protein kinase, JAK2 and PI3 kinase/Akt

Obesity is a major risk factor for the development of colon cancer. Secretion of the hormone leptin from adipocytes is increased in obesity, and serum levels are proportional to body fat mass. Serum leptin levels are an independent risk factor for colon cancer. Leptin receptors are expressed in normal, premalignant and malignant colonic epithelia. We have investigated the effects of leptin on proliferation and apoptosis of colonic cancer cells and the early signalling events involved. Proliferation of HT-29 colon cancer cells in response to leptin was assessed by 3-[4, 5-dimethylthiazol-2-y-l]-2, 5-diphenyltetrazolium bromide (MTT) assay, and apoptosis was quantified by enzyme-linked immunosorbent assay (ELISA) for intracellular nucleosomes. Signalling pathways involved were determined by using specific inhibitors, quantification of phosphorylated active intermediates and ELISA of active nuclear-translocated transcription factors. Leptin stimulated HT-29 cell proliferation and inhibited both serum-starvation and celecoxib-induced apoptosis. The proliferative and anti-apoptotic effects of leptin were abolished by inhibition of JAK2 with AG490, phosphatidylinositol 3'-kinase (PI3 kinase) with LY294002 and c-Jun NH(2)-terminal kinase (JNK) with SP600125. Stimulation of HT-29 cells with leptin increased phosphorylation of JAK2, Akt and JNK. Activation of JAK2 was upstream of PI3 kinase/Akt but not of JNK. Activation of JAK2 was followed by activation and nuclear translocation of STAT3 and JNK activation led to increased activator protein 1 (AP-1) transcriptional activity. Leptin stimulates proliferation and inhibits apoptosis in human colon cancer cells and may be an important factor in the increased incidence of colon cancer in obesity. This effect involves JAK2, PI3 kinase and JNK and activation of the oncogenic transcription factors signal transducer and activator of transcription (STAT)3 and AP-1.

Expression Profile Analysis of Colon Cancer Cells in Response to Sulindac or Aspirin

Nonsteroidal anti-inflammatory drugs (NSAIDs) have a preventive effect against colorectal cancer. Although inhibition of cyclooxygenase-2 plays a crucial role in the suppression of tumors, precise mechanisms of their action remain to be disclosed. To identify genes involved in the growth-suppressive effect of NSAIDs, we utilized cDNA microarray containing 23,040 genes and analyzed time-dependent alteration of gene expression in response to sulindac or aspirin in NSAIDs-sensitive SW480 and SW948 colon-cancer cells as well as in relatively resistant SNU-C4 cells. Consequently we identified 112 genes with commonly altered expression by sulindac and 176 with commonly altered expression by aspirin in the three lines. Addition of sulindac and that of aspirin altered expression levels of 130 and 140 genes, respectively, in SW480 and SW948 cells but not in SNU-C4 cells. These data may lead to a better understanding of growth-suppressive effects on colonic epithelium, and may provide clues for identifying novel therapeutic and/or preventive molecular targets of colon cancer.

P53 and β Catenin Expression in Chronic Ulcerative Colitis–Associated Polypoid Dysplasia and Sporadic Adenomas

In patients with chronic ulcerative colitis (CUC), polypoid dysplastic lesions (PDLs) are morphologically similar to sporadic adenomas (SAs), but may be biologically distinct from them and are managed differently. p53 mutations have been shown to occur at an earlier phase in the progression of CUC-associated neoplasia when compared with sporadic colon carcinogenesis. In contrast, APC gene mutations are common and occur at an earlier stage in the development of SA. beta catenin is a cell membrane protein that accumulates in the nucleus of colon cancer cells in response to APC gene mutations. This study was performed to test the hypothesis that CUC-associated PDLs have a different molecular profile than do CUC-associated SAs and therefore may be distinguished on this basis. Mucosal biopsy specimens of 38 benign polypoid epithelial neoplasms (17 CUC-associated PDLs and 21 CUC-associated SAs) from 33 patients with CUC and 13 SAs from patients without CUC (controls) were immunohistochemically stained for p53 and beta catenin and graded as follows: 0 = no staining, 1+ = <50% of cells positive, and 2+ = > or =50% of cells positive. The results were correlated with the clinical and histologic features and compared between the two CUC-associated polyp subgroups. Overall, six (16%) polyps were p53-positive, of which five were CUC-associated PDLs (one 1+ and four 2+) and one was a CUC-associated SA (1+) (p = 0.05). Strong (2+) p53 positivity was detected, however, in only CUC-associated PDLs (4 of 5; 80%). Nine of 32 polyps evaluated for beta catenin were positive and included 1 (8%) of 12 CUC-associated PDLs and 8 (40%) of 20 CUC-associated SAs (p = 0.06). Two of the nine beta catenin polyps were strongly positive, and both were CUC-associated SAs. Non-CUC-associated (control) SAs were positive for p53 and beta catenin in 2 (15%) of 13 and 6 (46%) of 13 cases, but none in a strong (2+) fashion. No differences were observed in p53 or beta catenin staining, between CUC-associated and non-CUC-associated SAs. Neither p53 nor beta catenin expression correlated with any clinical or pathologic features, including size and degree of dysplasia of the polyps. CUC-associated PDLs and CUC-associated SAs may have a different molecular genotype. In patients with CUC, the combination of strong p53 expression and absent or weak beta catenin expression is evidence in favor of a CUC-associated PDL in diagnostically difficult lesions. Furthermore, CUC-associated and non-CUC-associated SAs have a similar P53 and beta catenin immunophenotype and thus provide evidence that they are pathogenetically related neoplasms regardless of the presence or absence of colitis.