Colon Cancer Proliferation Research Articles

MiR-223-RhoB signaling pathway regulates the proliferation and apoptosis of colon adenocarcinoma

MicroRNAs (miRNAs) can function as tumor suppressor or oncogenic genes. The putative targets of miR-223 include tumor suppressor gene, RhoB. Here we sought to investigate the role of miR-223-RhoB signaling pathway in proliferation of colon cancer. We used Western blot, immunofluorescence staining, or RT-PCR to detect expression levels of miR-223 and RhoB in colon adenocarcinoma and adjacent non-cancerous tissue samples, or in human colon adenocarcinoma cell lines. MTT assay was used to determine proliferation and apoptosis in cell lines. We further used Western blot to determine levels of cell cycle regulators CDK1 and Cyclin B1 with anti-miR-223 or apoptosis with overexpression of RhoB. The expression level of miR-223 was significantly upregulated in clinical samples and cell lines of colon adenocarcinoma, in contrast to down-regulation of RhoB. In addition, we showed that inhibition of miR-223 led to upregulation of RhoB and in turn suppression of proliferation of colon adenocarcinoma. Moreover, inhibition of miR-223 or overexpression of RhoB induced cell arrest or apoptosis in colon adenocarcinoma. These results suggest that miR-223-RhoB signaling pathway plays an important role in modulation of proliferation, cell arrest, and apoptosis in colon cancer.

Proteomic analysis of muscarinic acetylcholine receptor-mediated proliferation in HT-29 human colon cancer cells

Muscarinic acetylcholine receptors (mAChRs) are members of G-protein-coupled receptors. They can induce agonist-dependent neoplastic transformation and facilitate colon cancer proliferation via promoting rapid expression of a variety of early responsive genes. In this study, we used 2-dimensional gel electrophoresis (2-DE) approach with subsequent mass spectrometry (MS) to identify up- and down-regulated proteins (a total of 23 protein spots) involved in mAChRs-related signaling pathway, energy metabolism, transcription/translation, oxidative stress metabolism and cytoskeleton organization in agonist carbachol stimulated HT-29 human colon cells. We found that the increased expression of adenocarcinoma biomarker, annexin A5 (ANXA5) induced by carbachol treatment, which was confirmed by immunoblot. This study contributes to the understanding of mechanisms underlying mAChRs agonist-induced expression of whole proteins in HT-29 colon cancer cells. Our results indicated that ANXA5 might serve as a potential biomarker for the diagnosis of colon cancer.

Effect and mechanism of antimicrobial peptide cathelicidin secreted by tumor associated macrophage on the growth of colorectal cancer in mice

Objective: To investigate the effect and mechanism of the antibacterial peptide cathelicidin secreted by tumor associated macrophages on the growth of colorectal cancer in mice. Methods: Azoxymethane (AOM)/ dextran sodium sulfate (DSS) method was used to establish a mouse model of colitis associated colon cancer. To induce tumor formation, cathelicidin antibody, IgG antibody (positive control) or PBS (negative control) was respectively injected into mice once every 3 days and lasted one month. Then the pictures of mice colon were taken, and the numbers of tumor were counted and evaluated. Expressions of cathelicidin in tumor associated macrophages isolated from tumor and adjacent normal tissues of mice were examined by quantitative RT-PCR (qRT-PCR) and Western blot. Expressions of the tumor proliferating antigen Ki-67, macrophage marker CD68 and cathelicidin in tumor and non-tumor tissues were determined by immunohistochemistry analysis. Apoptosis of cells from tumor tissues was analyzed by using TdT-mediated dUTP nick-end labeling (TUNEL). Results: In colon tumor tissues, cathlicidin strongly expressed in inflammatory cells (macrophages), but weakly expressed in tumor cells. The tumor number and size in mice injected with cathelicidin neutralizing antibody were 4.50±1.18 and (1.74±0.18) mm, respectively, significantly lower than 13.88±1.98 and (3.74±0.38) mm of mice injected with PBS (t=4.07, t=4.72; P< 0.01) and 15.25±1.82 and (3.40±0.36) mm of mice injected with IgG antibody (t=4.96, t=4.08; P<0.01). The Ki-67 positive rate of cells in tumor tissues of mice injected with cathelicidin neutralizing antibody was (28.20±3.44) %, significantly lower than (68.20±3.51) % of mice injected with PBS (t=8.135, P<0.01) and (69.20±3.41) % of mice injected with IgG antibody (t=8.461, P<0.01). Immunohistochemistry analyses showed that the expression of CD68 in tumor tissues of mice injected with cathelicidin antibody was significantly lower than that of mice injected with IgG antibody or PBS. TUNEL result showed that treatment with cathelicidin neutralizing antibody had negligible effect on the apoptosis of tumor cells. Conclusions: Cathelicidin secreted by tumor associated macrophages can promote the growth of colorectal cancer in mice, and neutralizing cathelicidin activity can inhibit the growth and proliferation of colorectal cancer. Cathelicidin mediated promotion of colon cancer proliferation may mainly be exerted by recruiting inflammatory cells such as macrophages into the tumor microenvironment.

2,2′-Dithiodisuccinic acid-stabilized polyion complex micelles for pH and reduction dual-responsive drug delivery

In this work, a new kind of polyion complex (PIC) micelles with pH and reduction dual responsiveness was developed for effective intracellular drug delivery. The PIC micelles can be readily prepared by mixing a polycationic block polymer, methoxy poly(ethylene glycol)-b-poly(l-lysine) (mPEG-PLL), with a small molecule polyacid, 2, 2′-dithiodisuccinic acid (DTS) in aqueous media. The resultant PIC micelles are of uniform spherical shapes with hydrodynamic radii ranging from 65 to 75 nm based on different feeding ratios of mPEG-PLL and DTS. Interestingly, by using the small molecule polyacid DTS, the obtained PIC micelles show distinct pH-responsive disintegration in acid solution. Meanwhile, the PIC micelles were also assessed to be reduction-responsive due to the presence of disulfide bond in DTS. In view of these stimuli-responsive properties, the potential use of this PIC micelle as smart drug carrier was then investigated. Doxorubicin (DOX), a cationic anticancer drug, was loaded into the PIC micelles with high efficiency. In vitro drug release studies revealed that release of DOX from the PIC micelles was suppressed in neutral solutions due to the stable electrostatic interactions between PIC micelles and DOX, but could be accelerated in acidic solutions or under high GSH condition. Furthermore, flow cytometry and confocal laser scanning microscopy (CLSM) studies indicated that the DOX-loaded PIC micelles could be effectively internalized by MCF-7 human breast cancer cells and release the loaded DOX in intracellular environment. Consequently, the DOX-loaded PIC micelles were capable of inhibiting the proliferation of C26 murine colon cancer and MCF-7 human breast cancer cells in high efficiency, showing similar IC50 values as free DOX. Thus, this biocompatible PIC micelle may be promising for intracellular drug delivery.

Downregulation of SIRT6 by miR-34c-5p is associated with poor prognosis and promotes colon cancer proliferation through inhibiting apoptosis via the JAK2/STAT3 signaling pathway.

Sirtuin 6 (SIRT6) is a member of the nicotinamide adenine dinucleotide positivity-dependent class III deacetylase sirtuin family. The present study aimed to explore the expression and function of SIRT6 in colon cancer. Furthermore, the partial mechanism underlying the dysregulation of SIRT6 was investigated. The results of immunohistochemistry demonstrated that SIRT6 was markedly downregulated in colon cancer tissues, and patients with high SIRT6 expression had a better prognosis than those who did not. The proliferation and apoptotic assays demonstrated that SIRT6 was able to suppress colon cancer cell proliferation and induce apoptosis via the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway. MicroRNAs (miRNAs/miRs) are important non-coding RNAs, which have a critical role in the negative regulation of their target genes. Through bioinformatics analysis and further experiments, the results demonstrated that miR-34c-5p was not only dysregulated in colon cancer tissues but may also regulate SIRT6 expression via interaction with the 3′-untranslated region of SIRT6 mRNA. The proliferation and apoptotic assays indicated that miR-34c-5p could directly promote cell growth and inhibit apoptosis via activation of the JAK2/STAT3 signaling pathway, which was similar to silencing SIRT6. In conclusion, the results of the present study demonstrated that miR-34c-5p promoted colon cancer cell proliferation by targeting SIRT6 via activation of the JAK2/STAT3 signaling pathway. It may be hypothesized that SIRT6 is a potential biomarker for colon cancer prognosis, and the miR-34c-5p/SIRT6/JAK2/STAT3 axis may provide novel insights into colon cancer treatment.

Catalpol suppressed proliferation, growth and invasion of CT26 colon cancer by inhibiting inflammation and tumor angiogenesis

Catalpol suppressed proliferation, growth and invasion of CT26 colon cancer by inhibiting inflammation and tumor angiogenesis

Antitumor effect of sikokianin C, a selective cystathionine β-synthase inhibitor, against human colon cancer in vitro and in vivo.

Cystathionine β-synthase (CBS) overexpression is related to the proliferation and migration of human colon cancers. Targeted therapy that inhibits CBS has achieved promising effects in colon cancer treatments, but no selective inhibitor of CBS is available. In our previous study, a natural biflavonoid compound, sikokianin C, was identified as a potent and selective inhibitor of CBS. However, the mode of action of this compound and its antitumor efficacy in vivo remain unknown. In the present study, we have demonstrated that sikokianin C selectively inhibits CBS activity in a competitive manner, and the five key residues involved in the binding of sikokianin C to the substrate channel of CBS protein were identified via a combination of molecular docking and site-directed mutagenesis. Additionally, we analyzed the antitumor efficacy of sikokianin C against human colon cancer cells in vitro and in vivo. Sikokianin C greatly suppressed the proliferation of HT29 colon cancer cells with an IC50 value of 1.6 μM, and CBS is the target of sikokianin C in mammalian cells, as evidenced by CBS knockdown analyses. Moreover, sikokianin C induced the apoptosis of HT29 cancer cells in a dose dependent manner. Treating mice with sikokianin C dramatically reduced the tumor volume and the weight of the colon cancer xenograft in vivo. These results indicate that the selective CBS inhibitor sikokianin C can potentially be used for the treatment of colon cancer.

Curcumin Suppresses the Colon Cancer Proliferation by Inhibiting Wnt/β-Catenin Pathways via miR-130a.

Curcumin exhibits anti-tumor effects in several cancers, including colorectal carcinoma (CRC), but the detailed mechanisms are still unclear. Here we studied the mechanisms underlying the anti-tumor effect of curcumin in colon cancer cells. SW480 cells were injected into mice to establish the xenograft tumor model, followed by evaluation of survival rate with the treatment of curcumin. The expression levels of β-catenin, Axin and TCF4 were measured in the SW480 cells in the absence or presence of curcumin. Moreover, miRNAs related to the curcumin treatment were also detected in vitro. Curcumin could suppress the growth of colon cancer cells in the mouse model. This anti-tumor activity of curcumin was exerted by inhibiting cell proliferation rather than promoting cell apoptosis. Further study suggested that curcumin inhibited cell proliferation by suppressing the Wnt/β-catenin pathway. MiR-130a was down-regulated by curcumin treatment, and overexpressing miR-130a could abolish the anti-tumor activity of curcumin. Our study confirms that curcumin is able to inhibit colon cancer by suppressing the Wnt/β-catenin pathways via miR-130a. MiR-130a may serve as a new target of curcumin for CRC treatment.

Impact of protamine I on colon cancer proliferation, invasion, migration, diagnosis and prognosis.

This paper investigates protamine I (PRM1) expression and its effects on proliferation, invasion and migration of colon cancer cells as well as its function in clinical diagnosis and prognosis. Gene chips were used to screen differentially expressed genes. PRM1 expression was detected by Western blotting and quantitative real time-polymerase chain reaction (qRT-PCR). Hematoxylin and eosin (HE) staining and immunohistochemistry were utilized to compare the expression of PRM1 from multiple differentiation levels of colon cancer tissues. Cell viability, cell apoptosis and cell cycle were tested using the MTT assay and flow cytometry. Cell invasion and migration capability were tested using the Transwell assay and wound healing. In vivo effects of PRM1 on colon cancer were explored using a xenograft model. PRM1 expression in serum was detected by enzyme-linked immunosorbent assay (ELISA). The expression level of PRM1 was significantly higher in colon cancer tissues and the staining degree of PRM1 in poorly-differentiated was stronger. pcDNA3.1-PRM1 decreased cell apoptosis while it increased the proliferation, cell invasion and migration. The si-PRM1 group displayed an opposite tendency. The serum PRM1 level was significantly higher and could serve as a diagnostic biomarker for colon cancer.

Salidroside could enhance the cytotoxic effect of L‑OHP on colorectal cancer cells.

Evidence has suggested that salidroside inhibits the proliferation and invasion of renal clear cell, lung, breast, and colon cancer. However, effect of salidroside on colorectal cancer (CRC) cells against oxaliplatin (L-OHP) resistance remains unclear. In the present study, the CRC HT-29 cell line and L-OHP resistance HT-29/L-OHP cell line were used to evaluate the effect, and mechanism of salidroside on L-OHP resistance. The results demonstrated that the activity of HT-29 cells was lower compared with that of HT-29/L-OHP cells following L-OHP intervention, and was accompanied with varied expression levels of drug resistant proteins. The combination of salidroside and L-OHP weakened cell activity significantly compared single utilization. Compared with the control group, salidroside intervention resulted in a higher percentage of HT-29/L-OHP cells in the G0/G1 stage, and reduced percentage in the G2/M stage, but no significant variation in the S stage. The HT-29/L-OHP cells exhibited increased apoptosis rates and caspase-3 activity, but decreased metastatic, and invasive abilities following salidroside intervention. Quantitative polymerase chain reaction and western blot analysis detected variations in the expression levels of associated genes in HT-29/L-OHP cells following salidroside intervention. In all, the results of the present study revealed that salidroside is able to decrease the activity and invasive capacity of HT-29/L-OHP cells, and treatment with salidroside is associated with increased apoptosis of cancer cells through the regulation of certain genes.

LncRNA BCAR4 promotes colon cancer progression via activating Wnt/β-catenin signaling

BCAR4 (Breast Cancer Anti-Estrogen Resistance 4) is a long noncoding RNA that was identified as an oncogene in breast cancer. In our research, we found that the expression level of BCAR4 was upregulated in colon cancer tissues compared to paired normal tissues. What's more, higher BCAR4 expression was correlated with lower survival rate in patients with colon cancer. Mechanistically, we showed that BCAR4 activated Wnt/β-catenin signaling in colon cancer by protecting β-catenin from degradation. We also showed that BCAR4 overexpression promoted cell proliferation and migration in colon cancer. However, silencing BCAR4 inhibited cell growth and promoted apoptosis. Besides, BCAR4 knockdown decreased tumor growth in vivo. These findings indicate that BCAR4 facilitated colon cancer progression by enhancing cell proliferation and inhibiting apoptosis via BCAR4/β-catenin axis. BCAR4 may be a useful new target for treatment of patients with colon cancer.

MiR-19b-3p promotes colon cancer proliferation and oxaliplatin-based chemoresistance by targeting SMAD4: validation by bioinformatics and experimental analyses

BackgroundAs a disease with extremely complex molecular mechanisms, many deregulated miRNAs have been identified in colon cancer. Few studies have been performed by using Ingenuity Pathways Analysis (IPA) to predict miRNAs specifically expressed in colon cancer.MethodsA characteristic microRNA-target network of colon cancer was explored using IPA. Then the clinical significance of miR-19b-3p was evaluated in 211 colon cancer patients. The roles of miR-19b-3p and its candidate target gene, SMAD4, in colon cancer progression were examined both in vitro and in vivo.ResultsBioinformatics analysis showed that 15 microRNAs screened by IPA were significantly correlated with malignant biological behaviors of colon cancer. miR-19b-3p was the most significantly upregulated candidate based on the validation experiment using 211 colon cancer samples. High expression of miR-19b-3p was significantly associated with high N stage (P < 0.001), high AJCC stage (P < 0.001), poor histologic grade (P = 0.032), frequent venous and lymphatic invasion (P = 0.027), and liver metastasis (P < 0.001). Survival analysis revealed that miR-19b-3p was an independent prognostic factor associated with colon cancer patient’s overall survival (OS) and disease-free survival (DFS). miR-19b-3p promoted proliferation and chemoresistance of colon cancer cells, but had no effect on invasion in vitro, along with tumorigenesis in vivo. In addition, we confirmed that miR-19b-3p mediates resistance to oxaliplatin-based chemotherapy via SMAD4.ConclusionsOur findings demonstrate the role of miR-19b-3p-SMAD4 axis in colon cancer progression, which may become a potential therapeutic target against chemotherapy resistance.

Ca2+/calmodulin-dependent protein kinase II regulates colon cancer proliferation and migration via ERK1/2 and p38 pathways.

AIMTo investigate the role of calmodulin-dependent protein kinase II (CaMKII) in colon cancer growth, migration and invasion.METHODSCaMKII expression in colon cancer and paracancerous tissues was evaluated via immunochemistry. Transcriptional and posttranscriptional levels of CaMKIIin tissue samples and MMP2, MMP9 and TIMP-1 expression in the human colon cancer cell line HCT116 were assessed by qRT-PCR and western blot. Cell proliferation was detected with the MTT assay. Cancer cell migration and invasion were investigated with the Transwell culture system and wound-healing assay.RESULTSWe first demonstrated that CaMKII was over-expressed in human colon cancers and was associated with cancer differentiation. In the human colon cancer cell line HCT116, the CaMKII-specific inhibitor KN93, but not its inactive analogue KN92, decreased cancer cell proliferation. Furthermore, KN93 also significantly prohibited HCT116 cell migration and invasion. The specific inhibition of ERK1/2 or p38 decreased the proliferation and migration of colon cancer cells.CONCLUSIONOur findings highlight CaMKII as a potential critical mediator in human colon tumor development and metastasis.

Targeted inhibition of the phosphoinositide 3-kinase impairs cell proliferation, survival, and invasion in colon cancer.

BackgroundColon cancer is the third most common cancer in the world, and its metastasis and drug resistance are challenging for its effective treatment. The PI3K/Akt/mTOR pathway plays a crucial role in the pathogenesis of colon cancer. The aim of this study was to investigate the targeting of PI3K in colon cancer cells HT-29 and HCT-116 in vitro.MethodsIn HT-29 and HCT-116 cells, BEZ235, a dual inhibitor of PI3K/mTOR, and shRNAtarget to PI3KCA were used to inhibit PI3K/Akt/mTOR pathway. The inhibition efficiency of PI3K/Akt/mTOR pathway was detected by RT-PCR and Western blot. Cell proliferation, migration, invasion, and apoptosis were evaluated by Cell Counting Kit-8, Transwell, and flow cytometry assays. The expression of apoptosis-related proteins (cleavage caspase 3, Bcl-2, Bax, and Bim) were also detected.ResultsWe found that in HT-29 and HCT-116 cells, the treatment of BEZ235 (1 μM) and PI3KCA knockdown inhibited the activation of PI3K/Akt/mTOR pathway and significantly suppressed cell proliferation, migration, and invasion of HT-29 and HCT-116 cells. In addition, we confirmed that knockdown of BEZ235 and PI3KCA induced cell apoptosis through the upregulated levels of cleavage caspase 3 and Bax and downregulated expression of Bcl-2 and Bim.ConclusionOur results indicated that targeted inhibition of the PI3K/Akt/mTOR pathway impaired cell proliferation, survival, and invasion in human colon cancer.

Catalpol suppressed proliferation, growth and invasion of CT26 colon cancer by inhibiting inflammation and tumor angiogenesis

Tumor angiogenesis and inflammation, which play important roles in mediating tumor proliferation and growth, should be inhibited to effectively regulate tumor progression. Catalpol, a main active ingredient extracted from Rehmannia glutinosa, has various pharmacological actions including anti-apoptotic, anti-inflammatory, hypoglycemic and anti-cancer properties. However, the pharmacological effect of catalpol on colon cancer remains largely unknown. The aim of this study was to investigate the effects of catalpol on the proliferation, growth, invasion, tumor angiogenesis and inflammation of CT26 colon cancer in vitro and in vivo. Catalpol inhibited the proliferation and growth of CT26 cells in concentration- and dose-dependent manners in vitro and in vivo, respectively. Catalpol suppressed the invasion of CT26 cells in vitro. Tumor cell-induced vascularization of endothelial cells and rat aortic ring angiogenesis were impaired by catalpol. Catalpol reduced the secretions of several angiogenic markers in the culture supernatant of CT26 cells. Immunohistochemical assay showed that catalpol inhibited the expressions of angiogenic markers vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2 (VEGFR2), hypoxia inducible factor-1α (HIF-1α) and basic fibroblast growth factor (bFGF) in colon cancer tissues. Moreover, catalpol inhibited the expressions of inflammatory factors interleukin-1β (IL-1β), IL-6, IL-8, cyclooxygenase (COX-2) and inducible nitric oxide synthase (iNOS). Taken together, catalpol suppressed the growth and invasion of CT26 colon cancer cells mainly by inhibiting inflammation and tumor angiogenesis, as a promising candidate compound for treating colon cancer.

Abstract 5616: Activation of CD137/CD137L results in reduced tumor cell proliferation in human colon cancer

Abstract Background: CD137L is expressed on antigen presenting cells and CD137/CD137L interaction co-stimulates activation and proliferation of CD137 expressing T cells. CD137L expression has also been detected on various cancer cells. While signaling in immune cells showed both inhibiting and activating effects the impact of CD137L induction on tumor cells is poorly understood. In this study, the expression of CD137 and CD137L and the effects of CD137L activation were analyzed in human colorectal cancer (CRC). Methods: Expression of CD137 and CD137L was examined in human colon cancer cell lines HT29, SW480 and SW620 treated with or without hypoxia using RT-qPCR, Western blot and FACS analysis. Its differentiated expression was further analyzed in human CRCs by immunofluorescent double-staining. To dissect the effects of CD137L activation on cancer cells, MTS proliferation assays were additionally performed. Results: All three human colon cancer cell lines demonstrated high cellular (FACS) and protein (Western Blot) CD137L expression. CD137 was found only in SW480 cells at weak expression. Additionally, both CD137 and CD137L were significantly upregulated in cells treated with hypoxia. In human CRCs both CD137 and CD137L expressing tumor cells were detected by immunofluorescent double-staining. Interestingly, activation of CD137L by immobilized CD137-Fc resulted in reduced cancer cell proliferation compared to IgG1-Fc controls. Conclusion: Our results demonstrate tumor cell mediated expression of the costimulatory molecule CD137 and its ligand CD137L in both colon cancer cell lines and human colorectal cancer. Moreover, CD137L reverse signaling was found to reduce cancer cell proliferation in vitro. Based on these data, the CD137/CD137L signaling pathway seems to present a promising target for cancer therapy in CRC. Note: This abstract was not presented at the meeting. Citation Format: Tanja Grimmig, Simone Callies, Hannes Naegele, Martin Wagner, Romana Moench, Buelent Polat, Christoph-Thomas Germer, Martin Gasser, Ana Maria Waaga-Gasser. Activation of CD137/CD137L results in reduced tumor cell proliferation in human colon cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5616. doi:10.1158/1538-7445.AM2017-5616

H2S-induced S-sulfhydration of lactate dehydrogenase a (LDHA) stimulates cellular bioenergetics in HCT116 colon cancer cells

Cystathionine-β-synthase (CBS) is upregulated and hydrogen sulfide (H2S) production is increased in colon cancer cells. The functional consequence of this response is stimulation of cellular bioenergetics and tumor growth and proliferation. Lactate dehydrogenase A (LDHA) is also upregulated in various colon cancer cells and has been previously implicated in tumor cell bioenergetics and proliferation. In the present study, we sought to determine the potential interaction between the H2S pathway and LDH activity in the control of bioenergetics and proliferation of colon cancer, using the colon cancer line HCT116. Low concentrations of GYY4137 (a slow-releasing H2S donor) enhanced mitochondrial function (oxygen consumption, ATP production, and spare respiratory capacity) and glycolysis in HCT116 cells. SiRNA-mediated transient silencing of LDHA attenuated the GYY4137-induced stimulation of mitochondrial respiration, but not of glycolysis. H2S induced the S-sulfhydration of Cys163 in recombinant LDHA, and stimulated LDHA activity. The H2S-induced stimulation of LDHA activity was absent in C163A LDHA. As shown in HCT116 cell whole extracts, in addition to LDHA activation, GYY4137 also stimulated LDHB activity, although to a smaller extent. Total cellular lactate and pyruvate measurements showed that in HCT116 cells LDHA catalyzes the conversion of pyruvate to lactate. Total cellular lactate levels were increased by GYY4137 in wild-type cells (but not in cells with LDHA silencing). LDHA silencing sensitized HCT116 cells to glucose oxidase (GOx)-induced oxidative stress; this was further exacerbated with GYY4137 treatment. Treatment with low concentrations of GYY4137 (0.3mM) or GOx (0.01U/ml) significantly increased the proliferation rate of HCT116 cells; the effect of GOx, but not the effect of GYY4137 was attenuated by LDHA silencing. The current report points to the involvement of LDHA in the stimulatory effect of H2S on mitochondrial respiration in colon cancer cells and characterizes some of the functional interactions between LDHA and H2S-stimulated bioenergetics under resting conditions, as well as during oxidative stress.

The influence and mechanisms of lysine-specific demethylase 1 (LSD1) on invasion and metastasis of colon cancer cells

Objective: To investigate the effect and molecular mechanisms of LSD1 on proliferation and metastasis of colon cancer. Methods: The influence of down-regulated LSD1 expression on proliferation, invasion and apoptosis of colon cancer cells were detected by transwell invasion assay, cell proliferation assay and apoptosis assay, respectively. Results: Three independent siRNAs targeting LSD1 (siRNA-1554, siRNA-705, and siRNA-1973) were transfected to SW620 cells to detect gene-silencing efficiency, and the result showed that the knockdown effect of siRNA-705 were better than the other two siRNAs at both mRNA and protein levels. Using siRNA-705 and pargyline (2.5 mmol/L), we performed transwell invasion assay, cell proliferation assay and apoptosis assay in SW620 cell lines, and found the significant suppression of invasion and growth. Cell apoptosis were induced by siRNA and pargyline (P<0.05). Interestingly, up-regulation of E-cadherin and down-regulation of N-cadherin were observed after treated with siRNA-705 and pargyline for 72 hours. Conclusion: Inhibition of LSD1 could impair proliferation and invasiveness, and induce apoptosis of colon cancer cells in vitro. It leads to up-regulation of E-cadherin and down-regulation of N-cadherin. All of above may play important roles in invasion and metastasis of colon cancer.

Hyperglycemia exacerbates colon cancer malignancy through hexosamine biosynthetic pathway

Hyperglycemia is a common feature of diabetes mellitus, considered as a risk factor for cancer. However, its direct effects in cancer cell behavior are relatively unexplored. Herein we show that high glucose concentration induces aberrant glycosylation, increased cell proliferation, invasion and tumor progression of colon cancer. By modulating the activity of the rate-limiting enzyme, glutamine-fructose-6-phosphate amidotransferase (GFAT), we demonstrate that hexosamine biosynthetic pathway (HBP) is involved in those processes. Biopsies from patients with colon carcinoma show increased levels of GFAT and consequently aberrant glycans’ expression suggesting an increase of HBP flow in human colon cancer. All together, our results open the possibility that HBP links hyperglycemia, aberrant glycosylation and tumor malignancy, and suggest this pathway as a potential therapeutic target for colorectal cancer.

Inhibitory effect of emodin on fatty acid synthase, colon cancer proliferation and apoptosis.

Fatty acid synthase (FASN) is a key anabolic enzyme for de novo fatty acid synthesis, which is important in the development of colon carcinoma. The high expression of FASN is considered a promising molecular target for colon cancer therapy. Emodin, a naturally occurring anthraquinone, exhibits an anticancer effect in various types of human cancer, including colon cancer; however, the molecular mechanisms remain to be fully elucidated. Cell viability was evaluated using a Cell Counting Kit-8 assay. The apoptosis rate of cells was quantified via flow cytometry following Annexin V/propidium iodide staining. FASN activity was measured by monitoring oxidation of nicotinamide adenine dinucleotide phosphate at a wavelength of 340 nm, and intracellular free fatty acid levels were detected using a Free Fatty Acid Quantification kit. Western blot analysis and reverse transcription-polymerase chain reaction were used to detect target gene and protein expression. The present study was performed to investigate whether the gene expression of FASN and its enzymatic activity are regulated by emodin in a human colon cancer cell line. Emodin markedly inhibited the proliferation of HCT116 cells and a higher protein level of FASN was expressed, compared with that in SW480, SNU-C2A or SNU-C5 cells. Emodin significantly downregulated the protein expression of FASN in HCT116 cells, which was caused by protein degradation due to elevated protein ubiquitination. Emodin also inhibited intracellular FASN enzymatic activity and reduced the levels of intracellular free fatty acids. Emodin enhanced antiproliferation and apoptosis in a dose- and time-dependent manner. The combined treatment of emodin and cerulenin, a commercial FASN inhibitor, had an additive effect on these activities. Palmitate, the final product of the FASN reaction, rescued emodin-induced viability and apoptosis. In addition, emodin altered FASN-involved signaling pathways, including phosphatidylinositol 3-kinase/Akt and mitogen-activated protein kinases/extracellular signal-regulated kinases 1/2. These results suggested that emodin-regulated cell growth and apoptosis were mediated by inhibiting FASN and provide a molecular basis for colon cancer therapy.