Data from Leptin Receptor–Related Immune Response in Colorectal Tumors: The Role of Colonocytes and Interleukin-8

We have shown that ObRb, the leptin receptor, is overexpressed in colorectal cancer cells, and that this may influence the patients' outcome. We investigated colonocytes as leptin targets and characterized their pivotal role in antitumor immune response. Cytokine and chemokine mRNAs in HT29 cells were measured by targeted arrays. In vitro, normal colonocytes and human colon cancer cells (HT29, Caco-2, SW480, and HCT116) were used to investigate ObRb transduction system and cytokine releases. Animal colonocytes and CD8 splenocytes and human HT29, HCT116, and CD8(+) cells from blood donors were used to investigate the lymphocyte response to the colonocytes when stimulated by leptin. Leptin-induced cytokine releases in the normal colonic mucosa and tumor growth and cytokine releases within tumors in vivo were measured in male rats and nude mice, respectively. Statistical analysis was done by Fisher's exact and Mann-Whitney U tests. Various cytokines and their receptors were produced in normal and tumoral colonocytes in response to leptin by increasing nuclear factor-kappaB activation. Interleukin-8 (IL-8) was the main cytokine produced in vitro. The levels of IL-8 and its receptor, CXCR1, were higher in tumors than in homologous normal mucosa. Systemic leptin enhanced the proinflammatory cytokines in normal colonocytes and in HT29 xenografted tumor colonocytes. Colonocyte-derived products after leptin treatment stimulated perforin and granzyme B expressions in normal CD8(+) T cells in vitro. Leptin triggers an inflammatory response in tumor tissue by directly stimulating colonocytes, which can recruit T cytotoxic cells in the tumor microenvironment.

<div>Abstract<p>We have shown that ObRb, the leptin receptor, is overexpressed in colorectal cancer cells, and that this may influence the patients' outcome. We investigated colonocytes as leptin targets and characterized their pivotal role in antitumor immune response. Cytokine and chemokine mRNAs in HT29 cells were measured by targeted arrays. <i>In vitro</i>, normal colonocytes and human colon cancer cells (HT29, Caco-2, SW480, and HCT116) were used to investigate ObRb transduction system and cytokine releases. Animal colonocytes and CD8 splenocytes and human HT29, HCT116, and CD8<sup>+</sup> cells from blood donors were used to investigate the lymphocyte response to the colonocytes when stimulated by leptin. Leptin-induced cytokine releases in the normal colonic mucosa and tumor growth and cytokine releases within tumors <i>in vivo</i> were measured in male rats and nude mice, respectively. Statistical analysis was done by Fisher's exact and Mann-Whitney <i>U</i> tests. Various cytokines and their receptors were produced in normal and tumoral colonocytes in response to leptin by increasing nuclear factor-κB activation. Interleukin-8 (IL-8) was the main cytokine produced <i>in vitro</i>. The levels of IL-8 and its receptor, CXCR1, were higher in tumors than in homologous normal mucosa. Systemic leptin enhanced the proinflammatory cytokines in normal colonocytes and in HT29 xenografted tumor colonocytes. Colonocyte-derived products after leptin treatment stimulated perforin and granzyme B expressions in normal CD8<sup>+</sup> T cells <i>in vitro</i>. Leptin triggers an inflammatory response in tumor tissue by directly stimulating colonocytes, which can recruit T cytotoxic cells in the tumor microenvironment. [Cancer Res 2008;68(22):9423–32]</p></div>

Polyamine levels, ornithine decarboxylase (ODC) activity, and ODC-mRNA expression in normal and cancerous human colonocytes

To assess the mechanism of action of 5-fluorouracil (5-FU) apoptosis (AI) and proliferation (PI) indices were determined histochemically in colon carcinoma and normal colon tissue of 7 patients treated preoperatively with 5-FU (300 mg/m2/day for 5 days) and 11 controls. 5-Fluorouracil induced apoptosis selectively in malignant colonocytes (AI in 5-FU-group: 0.126±0.016 [mean±SEM] vs. 0.065±0.012 in controls; P<0.05), but not in normal colonocytes. 5-Fluorouracil had no effect on the PI of either normal or malignant colonocytes. 5-Fluorouracil-induced apoptosis did not correlate with clinical outcome at 24 months. We conclude that 5-FU: (a) induces apoptosis selectively in colon cancer cells, while it spares the normal colonic mucosa, and (b) has no effect on colonocyte proliferation under the conditions of our protocol. This effect of 5-FU may contribute to its chemotherapeutic activity in human colon cancer.

The aim of this study was to determine the potential prognostic roles of the perioperative interleukin-6 (IL-6) level and its dynamic changes in patients with hepatocellular carcinoma (HCC) undergoing transarterial chemoembolization (TACE). Sixty patients with hepatitis B virus-associated HCC receiving TACE were enrolled in the study. Serum IL-6 levels were determined at baseline and 1 day after TACE by immunoassay. Response to TACE was evaluated after a 4-6-week interval. Factors associated with tumor response were analyzed by univariate and multivariate analysis in a Cox regression model. Receiver operating characteristic (ROC) curve analysis was performed to assess the predictive performance of the included variables on tumor response in patients with HCC undergoing TACE. The serum IL-6 level was significantly elevated 1 day after TACE. Patients in the low postintervention IL-6 level group had a high probability of achieving an objective response (OR) (66.7% vs. 18.8%, p = .021). Post-TACE IL-6 level (≤12.7 pg/mL) and post-/pre-TACE neutrophils ratio (>2.47) were independently correlated with OR after TACE. ROC curve analysis showed that a combined index based on those two factors exhibited optimal predictive power of tumor response among all the included variables (area under the curve = 0.740, 95% confidence interval: 0.601-0.879). Additionally, high post-TACE plasma IL-6 level was associated with maximum tumor size, vascular invasion, post-TACE aspartate aminotransferase, and Barcelona Clinic Liver Cancer stage. Our study suggests that the post-treatment serum IL-6 level, rather than pretreatment or dynamic changes of IL-6, serves as a powerful predictor for tumor response. These findings provide evidence to help discriminate between patients who will particularly benefit from TACE and those who require more personalized therapeutic regimens and rigorous surveillance. Transarterial chemoembolization (TACE) is a major therapeutic regimen for advanced hepatocellular carcinoma. Thus, identification of early practical markers of tumor response to TACE is of high importance. This study indicated that the post-treatment serum interleukin-6 (IL-6) level, rather than the pretreatment or dynamic changes of IL-6, serves as a powerful predictor for tumor response. A combined index based on the post-TACE IL-6 level and post-/pre-TACE neutrophils ratio is optimal for predetermining an objective response after TACE, which may be helpful in guiding individualized treatments and surveillance.

The short chain fatty acid (SCFA) butyrate is a product of colonic fermentation of dietary fibers. It is the main source of energy for normal colonocytes, but cannot be metabolized by most tumor cells. Butyrate also functions as a histone deacetylase (HDAC) inhibitor to control cell proliferation and apoptosis. In consequence, butyrate and its derived drugs are used in cancer therapy. Here we show that aggressive tumor cells that retain the capacity of metabolizing butyrate are positively selected in their microenvironment. In the mouse xenograft model, butyrate-preselected human colon cancer cells gave rise to subcutaneous tumors that grew faster and were more angiogenic than those derived from untreated cells. Similarly, butyrate-preselected cells demonstrated a significant increase in rates of homing to the lung after intravenous injection. Our data showed that butyrate regulates the expression of VEGF and its receptor KDR at the transcriptional level potentially through FoxM1, resulting in the generation of a functional VEGF:KDR autocrine growth loop. Cells selected by chronic exposure to butyrate express higher levels of MMP2, MMP9, α2 and α3 integrins, and lower levels of E-cadherin, a marker for epithelial to mesenchymal transition. The orthotopic model of colon cancer showed that cells preselected by butyrate are able to colonize the animals locally and at distant organs, whereas control cells can only generate a local tumor in the cecum. Together our data shows that a butyrate-rich microenvironment may select for tumor cells that are able to metabolize butyrate, which are also phenotypically more aggressive.

Background: mTORC2 phosphorylates Akt at Ser473 thus resulting in Akt activation; knockdown of rictor, a component of mTORC2, blocks Ser473 phosphorylation. Knockdown of rictor leads to growth inhibition and induces apoptosis in colorectal cancer (CRC) cells. However, the molecular mechanism(s) involved in the regulation of rictor expression remains unclear. Protein kinase D (PKD), a serine/threonine kinase family that includes PKD1, PKD2 and PKD3, has been implicated in the regulation of cell proliferation and apoptosis. Recently, PKD3 has been shown to increase Akt phosphorylation at Ser473. The purpose of this study was to investigate the regulation of rictor protein levels by protein kinase D (PKD) in CRC cells. Methods: HT29 and HCT116 CRC cells were treated with MG132, a proteasome inhibitor; cycloheximide (CHX), a protein synthesis inhibitor; Gö6976, a PKC and PKD inhibitor; Gö6983, a PKC inhibitor; or CID755673, a selective PKD inhibitor. Cells were transfected with plasmids encoding PKD1 or PKD2, or infected with an adenovirus construct expressing PKD3. Whole cell lysates were extracted and Western blot analysis performed for rictor protein expression. Total RNA was extracted and real-time RT-PCR was performed for rictor mRNA expression. To investigate whether PKD and rictor are co-localized, PKD and rictor expression was analyzed by immunohistochemistry in human CRCs, liver metastases and corresponding normal mucosa (AccuMax tissue array). Results: MG132 treatment increased rictor protein levels although raptor and mTOR expression was only slightly increased. Moreover, increased Akt Ser473 phosphorylation was observed. Treatment with CHX decreased rictor protein levels in a time-dependent fashion suggesting that rictor is a target of proteasomal degradation in CRC cells. Treatment of HT29 and HCT116 cells with Gö6976, but not Gö6983, decreased rictor protein expression. Consistently, treatment with the selective PKD inhibitor, CID755673, decreased rictor protein expression and inhibited CRC cell growth. Overexpression of PKD1, PKD2 or PKD3 increased rictor protein levels without affecting rictor mRNA expression. In addition, overexpression of PKD3 inhibited rictor degradation suggesting that PKDs are critical for rictor protein expression. Rictor as well as PKD1, PKD2 and PKD3 were up-regulated in primary CRCs and liver metastases compared with normal mucosa, implying a potential role of PKDs upstream of the rictor signaling pathway in the pathogenesis of CRC. Conclusions: Our results demonstrate that PKD post-transcriptionally regulates rictor protein levels in CRC cells. Importantly, these data suggest that PKD-mediated CRC growth is due, at least in part, to an mTORC2-dependent signaling pathway. 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 LB-238.

Epidemiological studies support the involvement of short-chain fatty acids (SCFA) in colon physiology and the protective role of butyrate on colon carcinogenesis. Among the possible mechanisms by which butyrate may exert its anti-carcinogenicity an antioxidant activity has been recently suggested. We investigated the effects of butyrate and mixtures of SCFA (butyrate, propionate and acetate) on DNA damage induced by H(2)O(2) in isolated human colonocytes and in two human colon tumour cell lines (HT29 and HT29 19A). Human colonocytes were isolated from endoscopically obtained samples and the DNA damage was assessed by the comet assay. H(2)O(2) induced DNA damage in normal colonocytes in a dose-dependent manner which was statistically significant at concentrations over 10 microM. At 15 microM H(2)O(2) DNA damage in HT29 and HT29 19A cells was significantly lower than that observed in normal colonocytes (P < 0.01). Pre-incubation of the cells with physiological concentrations of butyrate (6.25 and 12.5 mM) reduced H(2)O(2) (15 microM) induced damage by 33 and 51% in human colonocytes, 45 and 75% in HT29 and 30 and 80% in HT29 19A, respectively. Treatment of cells with a mixture of 25 mM acetate + 10.4 mM propionate + 6.25 mM butyrate did not induce DNA damage, while a mixture of 50 mM acetate + 20.8 mM propionate + 12.5 mM butyrate was weakly genotoxic only towards normal colonocytes. However, both mixtures were able to reduce the H(2)O(2)-induced DNA damage by about 50% in all cell types. The reported protective effect of butyrate might be important in pathogenetic mechanisms mediated by reactive oxygen species, and aids understanding of the apparent protection toward colorectal cancer exerted by dietary fibres, which enhance the butyrate bioavailability in the colonic mucosa.

DNA Hypermethylation Contributes to Incomplete Synthesis of Carbohydrate Determinants in Gastrointestinal Cancer

Regulation of colonic epithelial butyrate transport: Focus on colorectal cancer

Tumor cells exhibit higher glycolysis and rely on abnormal energy metabolism to produce ATP, which is essential for cell proliferation and migration. Abnormal energy metabolism inhibition is considered a promising tumor treatment strategy. Xanthatin is an active sesquiterpene lactone isolated from Xanthium strumarium L. This study evaluated the effect of xanthatin on the energy metabolism of human colon cancer cells. The results showed that xanthatin significantly inhibited the migration and invasion of human HT-29 and HCT-116 colon cancer cells. We found that xanthatin effectively reduced the production of ATP and promoted the accumulation of lactate. Xanthatin inhibited glycolysis which may be related to the reduction of glucose transporter 1 (Glut1) and monocarboxylate transporter 4 (MCT4) mRNA and protein levels. Concomitantly, xanthatin promoted complex II activity and oxidative phosphorylation (OXPHOS), resulting in mitochondrial damage and cell death in HT-29 cells. Furthermore, xanthatin inhibited the phosphorylation of mTOR, the phosphorylation of 4E-binding protein 1 (4E-BP1) and c-myc in HT-29 cells. Moreover, rapamycin, a mTOR inhibitor, could enhance the cytotoxicity effect in xanthatin treated HT-29 cells. Additionally, HT-29 cells transfected with si-mTOR aggravated xanthatin induced cell viability inhibition. Based on these results, we observed that the effect of xanthatin on energy metabolism may be related to its inhibition of the mTOR signaling pathway. Collectively, this study provides important insights into xanthatin's anticancer effect, which occurs by regulation of the energy metabolism of human colon cancer cells, and suggest that xanthatin has potential as a botanical drug against abnormal tumor energy metabolism.

This study investigated the effects of Agrimoniae Herba-Coptidis Rhizoma(XHC-HL)-medicated serum on the proliferation, migration, invasion, and apoptosis of human colorectal cancer HT29 and HCT116 cells via the autophagy mediated by lysosome-associated membrane protein type 2A(LAMP2A). Bioinformatics analysis was conducted to explore the role of LAMP2A in the development and progression of colorectal cancer. Western blot(WB) was used to detect the expression of LAMP2A protein in colorectal cancer cell lines. Lentiviral transfection was utilized to construct LAMP2A knockdown in HT29 and overexpression in HCT116 colorectal cancer cell models. Real-time fluorescence quantitative polymerase chain reaction(real-time qPCR) was performed to assess transfection efficiency. HT29 and HCT116 cells were treated with different concentrations of XHC-HL-medicated serum. The cell counting kit-8(CCK-8) assay was used to detect cell proliferation and determine the optimal concentration and duration of medicated serum intervention. HT29 cells were divided into a normal control(NC) group, an XHC-HL(medicated serum treatment) group, and an XHC-HL+shLAMP2A(medicated serum treatment+LAMP2A knockdown) group. HCT116 cells were divided into a NC group, an XHC-HL group, and an XHC-HL+LAMP2A(medicated serum treatment+LAMP2A overexpression) group. CCK-8 was used to measure cell viability. Colony formation assay was employed to assess cell proliferation ability. Scratch and Transwell migration assays were conducted to evaluate cell migration ability, and Transwell invasion assay was used to detect cell invasion ability. Flow cytometry was adopted to determine apoptosis rates. WB and real-time qPCR were employed to detect the effect of XHC-HL on the protein and mRNA expression of LAMP2A, heat shock cognate protein 70(HSC70), heat shock protein 90(HSP90), and glyceraldehyde-3-phosphate dehydrogenase(GAPDH) in colorectal cancer cells. Differential expression analysis revealed that LAMP2A expression was significantly higher in colorectal cancer patients compared to that in normal controls. Survival analysis indicated that the key molecule of chaperone-mediated autophagy(CMA), LAMP2A, was closely associated with colorectal cancer progression. Gene set enrichment analysis showed that patients with high LAMP2A expression significantly upregulated tumor progression-related signaling pathways such as angiogenesis and immune suppression. Immune infiltration analysis found that patients with high LAMP2A expression had fewer CD8 T cell infiltrations in their tumor microenvironment. XHC-HL-medicated serum inhibited the viability of HT29 and HCT116 cells, with the optimal intervention concentration and duration being 20% and 48 hours, respectively. Compared to the NC group, XHC-HL inhibited the proliferation, migration, and invasion of HT29 and HCT116 cells, and induced apoptosis. The medicated serum treatment with LAMP2A knockdown further inhibited colorectal cancer cell proliferation, invasion, and migration, and promoted apoptosis, whereas overexpression of LAMP2A reversed the inhibitory effects of the medicated serum on proliferation, migration, and invasion, and reduced apoptosis rates. XHC-HL-medicated serum inhibited CMA by upregulating the protein and mRNA expression of LAMP2A, HSC70, and HSP90 and downregulating substrate protein GAPDH expression via the autophagy mediated by LAMP2A. In conclusion, XHC-HL-medicated serum inhibits the proliferation, migration, and invasion of colorectal cancer cells and induces apoptosis by downregulating the expression of the key CMA molecule LAMP2A and inhibiting CMA activity.

Effects of aspirin on colon cancer using quantitative proteomic analysis

Long non-coding RNA (lncRNA) plays a key regulatory role in the pathogenesis of colorectal cancer (CRC). In the present study, the specific regulatory role of lncRNA ezrin antisense RNA 1 (EZR-AS1) on CRC was investigated. The expression of lncRNA EZR-AS1 was significantly up-regulated in CRC cell lines (HCT8, HCT116, HT29, and SW620 cells), which was significantly different from that of normal human fetal colonic mucosa cells (FHC cells) (P<0.01). HCT116 and HT29 cells were then transfected with EZR-AS1 shRNA (sh-EZR-AS1) to silence lncRNA EZR-AS1 (P<0.01). When compared with the Control, after transfection of SH-EZR-AS1, E-cadherin was up-regulated, Vimentin was down-regulated, the apoptosis rate was increased, the cell viability, wound healing rate, and the number of invasive cells were decreased in HCT116 and HT29 cells (P<0.05). Silencing of lncRNA EZR-AS also significantly reduced the tumor volume and weight in mice injected with sh-EZR-AS1-transfected HCT116 and HT29 cells (P<0.05). The regulatory relationship between lncRNA EZR-AS1 and transforming growth factor β (TGF-β) signaling was further identified in CRC cells. Silencing of lncRNA EZR-AS1 significantly down-regulated TGF-β, Smad2, and α-SMA expression in HCT116 and HT29 cells at the protein level (P<0.05). The intervention of SB431542 (a TGF-β receptor blocker) and silencing of Smad2 both significantly down-regulated lncRNA EZR-AS1 expression in HCT116 and HT29 cells (P<0.01). In conclusion, silencing of lncRNA EZR-AS1 inhibited the proliferation, invasion, migration, and epithelial–mesenchymal transition, and promoted the apoptosis of CRC cells through blocking TGF-β signaling.

The p53 tumor suppressor protein performs a number of cellular functions, ranging from the induction of cell cycle arrest and apoptosis to effects on DNA repair. Modulating p53 activity with Mdm2 inhibitors is a promising approach for treating cancer; however, it is presently unclear how the in vivo application of Mdm2 inhibitors impact the myriad processes orchestrated by p53. Since approximately half of all colon cancers (predominately cancers with microsatellite instability) are p53-normal, we assessed the anticancer activity of the Mdm2 inhibitor Nutlin-3 in the mouse azoxymethane (AOM) colon cancer model, in which p53 remains wild type. Using a cell line derived from an AOM-induced tumor, we found that four daily exposures to Nutlin-3 induced persistent p53 stabilization and cell cycle arrest without significant apoptosis. A 4-day dosing schedule in vivo generated a similar response in colon tumors; growth arrest without significantly increased apoptosis. In adjacent normal colon tissue, Nutlin-3 treatment reduced both cell proliferation and apoptosis. Surprisingly, Nutlin-3 induced a transient DNA damage response in tumors but not in adjacent normal tissue. Nutlin-3 likewise induced a transient DNA damage response in human colon cancer cells in a p53-dependent manner, and enhanced DNA strand breakage and cell death induced by doxorubicin. Our findings indicate that Mdm2 inhibitors not only trigger growth arrest, but may also stimulate p53's reported ability to slow homologous recombination repair. The potential impact of Nutlin-3 on DNA repair in tumors suggests that Mdm2 inhibitors may significantly accentuate the tumoricidal actions of certain therapeutic modalities.