Roles of survivin isoforms in the chemopreventive actions of NSAIDS on colon cancer cells

NSAIDs downregulate survivin (an apoptosis inhibitor), increase apoptosis and reduce growth of colon polyps and cancers. Recently, anti- and pro-apoptosis isoforms of survivin were identified. The roles of these isoforms in NSAID-induced colon cancer cell death have not been examined, and is the focus of this study. The anti-apoptosis isoforms, wild-type (WT) survivin and survivin-ΔEx3, and the pro-apoptosis isoform, survivin-2b, were present in HT-29 and RKO cells. Indomethacin treatment significantly decreased WT survivin and survivin-ΔEx3 (30.5±10.4% and 20.3±6.7%, respectively) but not survivin-2b mRNA in RKO cells. In HT-29 cells, all three isoform mRNAs were slightly decreased by indomethacin treatment. Consistently, indomethacin treatment dramatically reduced WT survivin protein in RKO but not HT-29 cells. Indomethacin treatment increased apoptosis and general cell death more significantly in RKO cells (75.7±1.1% cell death at 48 h) than in HT-29 cells (25.4±3.7% cell death at 48 h). Anti-sense suppression of survivin-2b mRNA increased resistance of both RKO and HT-29 cells to indomethacin. These data support a role for survivin isoforms in colon cancer cell apoptosis, and thus in prevention of colon cancer growth by NSAIDs.     

Chemoprevention of precursors to colon cancer by dehydroepiandrosterone (DHEA)

Although dehydroepiandrosterone (DHEA) is recognized as one of the major adrenal androgens, its precise physiological role in the human endocrine system remains to be elucidated. In particular, the effect of DHEA on carcinogenesis has not been fully characterized. We undertook this study to determine whether DHEA has a chemopreventative effect on the precursors of colon cancer in a murine model of azoxymethane (AOM)-induced aberrant crypt foci (ACF). The number of ACF was significantly decreased in mice treated with 0.4% (p < 0.001) and 0.8% DHEA (p < 0.001), but there were no significant differences between DHEA-treated and control mice in terms of the ACF size, 3-catenin expression or level of dysplasia. This is the first study of colon cancer carcinogenesis demonstrating that DHEA treatment can decrease the number of ACF without apparently modifying their malignant potential. These data strongly suggest that DHEA might be a potential chemopreventative agent against human colon cancer.     

A novel histone deacetylase inhibitor Chidamide induces apoptosis of human colon cancer cells

Many studies have demonstrated that histone deacetylase (HDAC) inhibitors induce various tumor cells to undergo apoptosis, and such inhibitors have been used in different clinical trials against different human cancers. In this study, we designed and synthesized a novel HDAC inhibitor, Chidamide. We showed that Chidamide was able to increase the acetylation levels of histone H3 and to inhibit the PI3K/Akt and MAPK/Ras signaling pathways, which resulted in arresting colon cancer cells at the G1 phase of the cell cycle and promoting apoptosis. As a result, the proliferation of colon cancer cells was suppressed in vitro. Our data support the potential application of Chidamide as an anticancer agent in treating colon cancer. Future studies are needed to demonstrate its in vivo efficacy.     

结肠腺癌组织中COX-2和PTEN蛋白表达与临床病理特征的相关性分析

目的检测环氧合酶-2（COX-2）和PTEN蛋白在结肠癌中的表达,探讨两基因表达与临床病理因素的关系以及二者之间的关系。方法选择2010年1月-2012年4月在我校附属医院行根治手术切除的结肠腺癌组织56例,另取同期活检15例非肿瘤结肠黏膜组织作为对照,采用免疫组织化学方法检测COX-2和PTEN蛋白的表达情况。结果COX-2在结肠腺癌组织中阳性率高于非肿瘤结肠黏膜组织（82．1% vs 13．3％,P〈0．05）;PTEN在结肠腺癌组织中阳性率低于非肿瘤结肠黏膜组织（51．8％vs 100．0％,P〈0．05）。COX-2与PTEN的表达与Duke分期及有无淋巴结转移有关,而与性别、年龄和组织学分型无明显相关。结肠腺癌组织中COX-2和PTEN的表达呈负相关（r=-0．357,P=0．007）。结论COX-2表达上调及PTEN失表达与结肠腺癌的发生发展、浸润、转移有关,两指标联合检测有助于结肠腺癌生物学行为的评估。     

O-GlcNAcylation is a novel regulator of lung and colon cancer malignancy

O-GlcNAc is a monosaccharide attached to serine or threonine hydroxyl moieties on numerous nuclear and cytoplasmic proteins; O-GlcNAcylation is dynamically regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). Although recent studies have shown that O-GlcNAcylation plays essential roles in breast cancer progression, it is also necessary to know whether O-GlcNAcylation is involved in other types of human cancer. In this study, O-GlcNAcylation levels and the expressions of OGT and OGA in human lung and colon cancer tissues were examined by immunohistochemistry analysis. We found that O-GlcNAcylation as well as OGT expression was significantly elevated in the cancer tissues compared with that in the corresponding adjacent tissues. Additionally, the roles of O-GlcNAcylation in the malignancy of lung and colon cancer were investigated in vitro. The results showed that O-GlcNAcylation markedly enhanced the anchorage-independent growth of lung and colon cancer cells; O-GlcNAcylation could also enhance lung and colon cancer invasion in a context-dependent manner. All together, this study suggests that O-GlcNAcylation might play important roles in lung and colon cancer formation and progression, and may be a valuable target for diagnosis and therapy of cancer.     

Mechanisms by which docosahexaenoic acid and related fatty acids reduce colon cancer risk and inflammatory disorders of the intestine

A growing body of epidemiological, clinical, and experimental evidence has underscored both the pharmacological potential and the nutritional value of dietary fish oil enriched in very long chain n − 3 PUFAs such as docosahexaenoic acid (DHA, 22:6, n − 3) and eicosapentaenoic acid (EPA, 20:5, n − 3). The broad health benefits of very long chain n − 3 PUFAs and the pleiotropic effects of dietary fish oil and DHA have been proposed to involve alterations in membrane structure and function, eicosanoid metabolism, gene expression and the formation of lipid peroxidation products, although a comprehensive understanding of the mechanisms of action has yet to be elucidated. In this review, we present data demonstrating that DHA selectively modulates the subcellular localization of lipidated signaling proteins depending on their transport pathway, which may be universally applied to other lipidated protein trafficking. An interesting possibility raised by the current observations is that lipidated proteins may exhibit different subcellular distribution profiles in various tissues, which contain a distinct membrane lipid composition. In addition, the current findings clearly indicate that subcellular localization of proteins with a certain trafficking pathway can be subjected to selective regulation by dietary manipulation. This form of regulated plasma membrane targeting of a select subset of upstream signaling proteins may provide cells with the flexibility to coordinate the arrangement of signaling translators on the cell surface. Ultimately, this may allow organ systems such as the colon to optimally decode, respond, and adapt to the vagaries of an ever-changing extracellular environment.     

Mitochondrial metabolism in cancer stem cells: a therapeutic target for colon cancer

It has been proposed that the selective elimination of cancer stem cells (CSCs) using targeted therapy could greatly reduce tumor growth, recurrence, and metastasis. To develop effective therapeutic targets for CSC elimination, we aimed to define the properties of CSC mitochondria, and identify CSC-mitochondria-specific targets in colon cancer. We found that colon CSCs utilize mitochondrial oxidative phosphorylation (OXPHOS) to produce ATP. We also found that forkhead box protein 1 (FOXM1)-induced peroxiredoxin 3 (PRDX3) maintains the mitochondrial function, and the FOXM1/PRDX3 mitochondrial pathway maintains survival of colon CSCs. Furthermore, FOXM1 induces CD133 (PROM1/prominin 1) expression, which maintains the stemness of colon CSCs. Together, our findings indicate that FOXM1, PRDX3, and CD133 are potential therapeutic targets for the elimination of CSCs in colon cancer. [BMB Reports 2015; 48(10): 539-540]     

miR-181a mediates metabolic shift in colon cancer cells via the PTEN/AKT pathway

Cancer cell metabolism is often characterized by a shift from an oxidative to a glycolytic bioenergetics pathway, a phenomenon known as the warburg effect. Whether the deregulation of miRNAs contributes to the warburg effect remains largely unknown. Here we show that miR-181a expression is increased and thus induces a metabolic shift in colon cancer cells. miR-181a performs this function by inhibiting the expression of PTEN, leading to an increase of phosphorylated AKT which triggers metabolic shift. The increase of lactate production induced by miR-181a results in the rapid growth of cancer cells. These results identify miR-181a as a molecular switch involved in the orchestration of the warburg effect in colon cancer cells via the PTEN/AKT pathway.     

Overexpression of PTEN induces cell growth arrest and apoptosis in human breast cancer ZR-75-1 cells

Phosphatase and tensin homolog （PTEN） is a tumor suppressor gene located at human chromosome 10q23, might play an important role in cell proliferation, cell cycle and apoptosis of cancer cells. In this study, the eukaryotic expression vectors pBP-wt-PTEN （containing a wild-type PTEN gene） and pBP-G129R-PTEN （containing a mutant PTEN gene） were used to transfect breast cancer ZR-75-1 cells. After transfection, ZR-75-1 cells expressing PTEN were obtained and tested. The blue exclusion assay showed the growth rate of the cells transfected with pBP-wt-PTEN was significantly lower than that of the control cells transfected with pBP-G129R-PTEN. Analysis of the cell cycle by flow cytometry showed that the progression from the G1 to the S phase was arrested in cells expressing wild-type PTEN. Some typical morphological changes of apoptosis were also observed in cells transfected with pBP-wt-PTEN, but not in those transfected with pBP-G 129R-PTEN. This study shows that overexpression of PTEN in ZR-75-1 cells leads to cell growth arrest and apoptosis.     

PTEN and myotubularin phosphatases: from 3-phosphoinositide dephosphorylation to disease

The phosphatase and tensin homolog deleted on chromosome ten (PTEN) and myotubularin (MTM1) represent subfamilies of protein tyrosine phosphatases whose principal physiological substrates are D3-phosphorylated inositol phospholipids. As lipid phosphatases, PTEN- and MTM1-related (MTMR) proteins dephosphorylate the products of phosphoinositide 3-kinases and antagonize downstream effectors that utilize 3-phosphoinositides as ligands for protein targeting domains or allosteric activation. Here, we describe the cellular mechanisms of PTEN and MTMR function and their role in the etiology of cancer and other human diseases.     

Understanding the colon cancer stem cells and perspectives on treatment

An area of research that has been recently gaining attention is the relationship between cancer stem cell (CSC) biology and chemo-resistance in colon cancer patients. It is well recognized that tumor initiation, growth, invasion and metastasis are promoted by CSCs. An important reason for the widespread interest in the CSC model is that it can comprehensibly explain essential and poorly understood clinical events, such as therapy resistance, minimal residual disease, and tumor recurrence. This review discusses the recent advances in colon cancer stem cell research, the genes responsible for CSC chemoresistance, and new therapies against CSCs.     

Alpha-tocopheryl succinate sensitizes human colon cancer cells to exisulind-induced apoptosis

Sulindac sulfone (also known as exisulind) and its chemical derivatives are promising anticancer agents capable of inducing apoptosis in a variety of malignant cell types with minimal toxicity to normal cells. Here, we tested the ability of alpha-tocopheryl succinate (TOS), another promising anticancer agent, to sensitize colon cancer cells to exisulind-induced apoptosis. We found that sub-apoptotic doses of TOS greatly enhanced exisulind-induced growth suppression and apoptosis in the HCT116, LoVo and SNU-C4 human colon cancer cell lines. Our results revealed that this was accounted for primarily by an augmented cleavage of poly(ADP-ribose) polymerase (PARP) and enhanced activation of caspase-8, -9 and -3. Pretreatment with z-VAD-FMK (a pan-caspase inhibitor), z-IETD-FMK (a caspase-8 inhibitor) or z-LEHD-FMK (a caspase-9 inhibitor) blocked TOS and exisulind cotreatment-induced PARP cleavage and apoptosis. Furthermore, TOS/exisulind cotreatment induced JNK phosphorylation, while pretreatment with SP600151 (a JNK inhibitor) partially blocked cotreatment-induced caspase-dependent PARP cleavage and apoptosis. Taken together, these findings indicate that TOS sensitizes human colon cancer cells to exisulind-induced apoptosis. Apoptotic synergy induced by exisulind plus TOS seems likely to be mediated through a mechanism involving activation of caspases and JNK. S.-J. Lim, Y.-J. Lee both authors are contributed equally to this study.     

结直肠癌PTEN基因表达及与p-ERK相关性研究

目的 研究结直肠癌中的PTEN、p-ERK蛋白的表达及相互关系,初步探讨它们在结直肠癌的发生发展中的生物学意义.方法 应用免疫组织化学染色快捷法,检测40例结直肠癌组织、18例结直肠腺瘤、13例结直肠正常黏膜中PTEN蛋白、和p-ERK蛋白的表达情况,比较PTEN蛋白表达与临床病理指标的关系,及其与p-ERK蛋白表达的相关性.结果 1.结直肠癌癌组织PTEN蛋白表达的阳性率(57.5％)明显弱于腺瘤(72.2％)及正常组织(100％),组间比较差异有显著性(P＜0.05),其表达水平与结直肠癌的分化程度、淋巴结转移、浸润深度、Dukes分期有关,与患者的性别、年龄,肿瘤大小及位置无关(P＞0.05)2.结直肠癌组织p-ERK蛋白表达的阳性率(72.5％)明显高于正常结直肠黏膜组(0.00％)及腺瘤组(66.6％),组间比较差异有显著性(P＜0.01),其表达随结直肠癌侵润深度增加、淋巴结转移、Duke分期的进展而增高.3.PTEN蛋白表达强度与p-ERK蛋白表达强度之间呈负相关(r=-0.452,P＜0.05).结论 提示抑癌基因PTEN的表达与结直肠癌生物学行为密切相关;在结直肠癌发生、发展过程中,可能由于PTEN蛋白的低表达或失表达不能有效抑制ERK磷酸化,使细胞发生癌变,并促进癌变细胞的浸润、转移.     

Role of the PTEN protein in the multidrug resistance of prostate cancer cells

At present, there is no doubt that the signal transduction pathway P13K/Akt/PTEN/mTOR, controlled by phosphatidylinositol-3-kinase, is involved in tumor cell resistance to a number of drugs. Another well-known mechanism determining drug resistance in tumors is associated with the activity of drug transporters of the ABC superfamily (first of all, P-glycoprotein (Pgp), MRP1, BCRP, and LRP). Several mechanisms of cell defense can simultaneously operate in one cell. The interplay of different mechanisms involved in drug resistance is poorly understood. The PC3 and DU145 human prostate cell lines were used to show that the PTEN functional status determined the cell resistance to some drugs and that correlated with the levels of MRP1 and BCRP. Pgp was not involved in drug resistance of these cells. Introduction of PTEN into PTEN-deficient PC3 cells, as well as rapamycin treatment, inhibited Akt and mTOR and sensitized cells to doxorubicin and vinblastine. Exogenous PTEN altered the MRP1 and BCRP expression. The results indicate that at least two mechanisms of drug resistance operate in prostate cancer cells: the PI3K/Akt/PTEN/mTOR pathway and an elevated MRP1 expression. The mechanisms are interconnected: PTEN and mTOR signaling is involved in MRP1 and BCRP expression regulation.