Zinc stabilizes adenomatous polyposis coli (APC) protein levels and induces cell cycle arrest in colon cancer cells

In the present study, we investigated the mechanisms by which zinc causes growth arrest in colon cancer cells. The results suggest that zinc treatment stabilizes the levels of the wild-type adenomatous polyposis coli (APC) protein at the post-translational level since the APC mRNA levels and the promoter activity of the APC gene were decreased in HCT-116 cells (which express the wild-type APC gene) after treatment with ZnCl2. Increased levels of wild-type but not truncated APC proteins were required for the ZnCl2-mediated G2/M phase arrest in different colon cancer cell lines. We further tested whether serum-stimulation, which induces cell cycle arrest in the S phase, can relieve ZnCl2-induced G2/M phase arrest of HCT-116 cells. Results showed that in the HCT-116 cells pretreated with ZnCl2, the serum-stimulation neither changed the distribution of G2/M phase arrested cells nor the increased levels of APC protein. The G2/M phase arrest correlated with retarded growth of HCT-116 cells. To further establish that wild-type APC protein plays a role in ZnCl2-induced G2/M arrest, we treated SW480 colon cancer cells that express truncated APC protein. We found that ZnCl2 treatment did not induce G2/M phase arrest in SW480 cells; however, the cell growth was retarded due to the loss of E-cadherin and alpha-tubulin levels. These results suggest that ZnCl2 inhibits the proliferation of colon cancer cells (which carry the wild-type APC gene) through stabilization of the APC protein and cell cycle arrest in the G2/M phase. On the other hand, ZnCl2 inhibits the proliferation of colon cancer cells (which carry the mutant APC gene) by disrupting cellular attachment and microtubule stability.     

Metformin: A Potential Therapeutic Agent for Recurrent Colon Cancer

Accumulating evidence suggests that metformin, a biguanide class of anti-diabetic drugs, possesses anti-cancer properties. However, most of the studies to evaluate therapeutic efficacy of metformin have been on primary cancer. No information is available whether metformin could be effectively used for recurrent cancer, specifically colorectal cancer (CRC) that affects up to 50% of patients treated by conventional chemotherapies. Although the reasons for recurrence are not fully understood, it is thought to be due to re-emergence of chemotherapy-resistant cancer stem/stem-like cells (CSCs/CSLCs). Therefore, development of non-toxic treatment strategies targeting CSCs would be of significant therapeutic benefit.In the current investigation, we have examined the effectiveness of metformin, in combination with 5-fluorouracil and oxaliplatin (FuOx), the mainstay of colon cancer therapeutics, on survival of chemo-resistant colon cancer cells that are highly enriched in CSCs/CSLCs. Our data show that metformin acts synergistically with FuOx to (a) induce cell death in chemo resistant (CR) HT-29 and HCT-116 colon cancer cells, (b) inhibit colonospheres formation and (c) enhance colonospheres disintegration. In vitro cell culture studies have further demonstrated that the combinatorial treatment inhibits migration of CR colon cancer cells. These changes were associated with increased miRNA 145 and reduction in miRNA 21. Wnt/β-catenin signaling pathway was also down-regulated indicating its pivotal role in regulating the growth of CR colon cancer cells. Data from SCID mice xenograft model of CR HCT-116 and CR HT-29 cells show that the combination of metformin and FuOX is highly effective in inhibiting the growth of colon tumors as evidenced by ∼50% inhibition in growth following 5 weeks of combination treatment, when compared with the vehicle treated controls. Our current data suggest that metformin together with conventional chemotherapy could be an effective treatment regimen for recurring colorectal cancer (CRC).     

N-glycan biosynthesis inhibitors induce in vitro anticancer activity in colorectal cancer cells

During malignant transformation, changes in the expression profile of glycans may be involved in a variety of events, including the loss of cell-cell and cell-matrix adhesion, migration, invasion, and evasion of apoptosis. Therefore, modulation of glycan expression with drugs has promising therapeutic potential for various cancer types. In this study, we investigated the in vitro anticancer activity of the N-glycan biosynthesis inhibitors (swainsonine and tunicamycin) in cells derived from colorectal cancer (CRC). We also examined whether these inhibitors are able to induce radiosensitization and toxicity when used in combination with cisplatin or irinotecan, two current anticancer drugs. Our results show that treatment with tunicamycin inhibits cellular mechanisms related to the malignant phenotype, such as anchorage-dependent and anchorage-independent colony formation, migration and invasion, in undifferentiated HCT-116 colon cancer cells, whereas swainsonine only inhibits cell migration. We also observed that tunicamycin, but not swainsonine, caused radiosensitivity in HCT-116 cells. Moreover, the combination of swainsonine with cisplatin or irinotecan enhanced their toxicity in HCT-116 cells, while the combination of tunicamycin with these drugs had no effect. Given these results, we suggest that the modulation of N-glycan biosynthesis appears to be a potential therapeutic tool for CRC treatment because inhibition of this process induced anticancer activity in vitro. Additionally, the inhibition of the N-glycan biosynthesis in combination with chemotherapic drugs is a promising therapeutic strategy for enhancing radiation therapy.     

GHRH antagonist when combined with cytotoxic agents induces S-phase arrest and additive growth inhibition of human colon cancer

Treatment of colon cancer with an antagonist of growth hormone-releasing hormone (GHRH), JMR-132, results in a cell cycle arrest in S-phase of the tumor cells. Thus, we investigated the effect of JMR-132 in combination with S-phase-specific cytotoxic agents, 5-FU, irinotecan and cisplatin on the in vitro and in vivo growth of HT-29, HCT-116 and HCT-15 human colon cancer cell lines. In vitro, every compound inhibited proliferation of HCT-116 cells in a dose-dependent manner. Treatment with JMR-132 (5 μM) combined with 5-FU (1.25 μM), irinotecan (1.25 μM) or cisplatin (1.25 μM) resulted in an additive growth inhibition of HCT-116 cells in vitro as shown by MTS assay. Cell cycle analyses revealed that treatment of HCT-116 cells with JMR-132 was accompanied by a cell cycle arrest in S-phase. Combination treatment using JMR-132 plus a cytotoxic drug led to a significant increase of the sub-G₁ fraction, suggesting apoptosis. In vivo, daily treatment with GHRH antagonist JMR-132 decreased the tumor volume by 40–55% (p < 0.001) of HT-29, HCT-116 and HCT-15 tumors xenografted into athymic nude mice. Combined treatment with JMR-132 plus chemotherapeutic agents 5-FU, irinotecan or cisplatin resulted in an additive tumor growth suppression of HT-29, HCT-116 and HCT-15 xenografts to 56–85%. Our observations indicate that JMR-132 enhances the antiproliferative effect of S-phase-specific cytotoxic drugs by causing accumulation of tumor cells in S-phase.     

Effect of selenite combined with chemotherapeutic agents on the proliferation of human carcinoma cell lines

Selenite is frequently used in combination with cancer chemotherapeutic agents to reduce side effects. However, the cytoprotective activity of selenite may also reduce the efficacy of chemotherapeutic drugs on tumor cells. This study was designed to examine the effects of selenite combined with cytotoxic agents used in clinical protocols [e.g., doxorubicine, docetaxel, 5-fluorouracil (5-FU), methotrexate (MTX), mafosphamide, mitomycin C, gemcitabine, etoposide, cisplatin, irinotecan, and oxaliplatin] on the proliferation of various carcinoma cell types. The data demonstrated that selenite had no marked effects on the antiproliferative activity of docetaxel, doxorubicine, 5-FU, MTX, and mafosphamide in MDA-MB-231 breast cancer cells. Likewise, no consistent changes were observed in A549 lung cancer cell proliferation when selenite was combined with cisplatin, etoposide, gemcitabine, or mitomycin C. On the other hand, selenite potentiated the cytotoxicity of 5-FU, oxaliplatin, and irinotecan in HCT116 colon cancer cells by approx 1.1-fold, 2.7-fold, and 2.6-fold, respectively. In SW620 colon cancer cells, selenite induced a 1.5-fold and 4.3-fold increase of the antiproliferative activity of 5-FU and oxaliplatin, respectively. Whereas irinotecan showed no effects on SW620 cell growth, a combination with selenite resulted in 23% inhibition. Our results indicate that selenite did not reduce the antiproliferative activity of chemotherapeutic agents in vitro. In addition, selenite was able to increase the inhibitory activity of docetaxel in A549 lung cancer cells, and of 5-FU, oxaliplatin, and irinotecan in HCT116 and SW620 colon cancer cells implying selenite is potentially useful as an adjuvant chemotherapeutic agent.     

Schlafen-3 decreases cancer stem cell marker expression and autocrine/juxtacrine signaling in FOLFOX-resistant colon cancer cells

We have previously demonstrated that expression of the novel gene schlafen-3 (Slfn-3) correlates with intestinal epithelial cell differentiation (Patel VB, Yu Y, Das JK, Patel BB, Majumdar AP. Biochem Biophys Res Commun 388: 752-756, 2009). The present investigation was undertaken to examine whether Slfn-3 plays a role in regulating differentiation of FOLFOX-resistant (5-fluorouracil + oxaliplatin) colon cancer cells that are highly enriched in cancer stem cells (CSCs). Transfection of Slfn-3 in FOLFOX-resistant colon cancer HCT-116 cells resulted in increase of alkaline phosphatase activity, a marker of intestinal differentiation. Additionally, Slfn-3 transfection resulted in reduction of mRNA and protein levels of the CSC markers CD44, CD133, CD166, and aldehyde dehydrogenase 1 in both FOLFOX-resistant HCT-116 and HT-29 cells. This was accompanied by decreased formation of tumorosphere/colonosphere (an in vitro model of tumor growth) in stem cell medium and inhibition of expression of the chemotherapeutic drug transporter protein ABCG2. Additionally, Slfn-3 transfection of FOLFOX-resistant HCT-116 and HT-29 cells reduced Hoechst 33342 dye exclusion. Finally, Slfn-3 transfection inhibited the expression of transforming growth factor-α in both FOLFOX-resistant colon cancer cells, but stimulated apoptosis in response to additional FOLFOX treatment. In summary, our data demonstrate that Slfn-3 expression inhibits multiple characteristics of CSC-enriched, FOLFOX-resistant colon cancer cells, including induction of differentiation and reduction in tumorosphere/colonosphere formation, drug transporter activity, and autocrine stimulation of proliferation. Thus Slfn-3 expression may render colon CSCs more susceptible to cancer chemotherapeutics.     

GHRH antagonist when combined with cytotoxic agents induces S-phase arrest and additive growth inhibition of human colon cancer

Treatment of colon cancer with an antagonist of growth hormone-releasing hormone (GHRH), JMR-132, results in a cell cycle arrest in S-phase of the tumor cells. Thus, we investigated the effect of JMR-132 in combination with S-phase-specific cytotoxic agents, 5-FU, irinotecan and cisplatin on the in vitro and in vivo growth of HT-29, HCT-116 and HCT-15 human colon cancer cell lines. In vitro, every compound inhibited proliferation of HCT-116 cells in a dose-dependent manner. Treatment with JMR-132 (5 μM) combined with 5-FU (1.25 μM), irinotecan (1.25 μM) or cisplatin (1.25 μM) resulted in an additive growth inhibition of HCT-116 cells in vitro as shown by MTS assay. Cell cycle analyses revealed that treatment of HCT-116 cells with JMR-132 was accompanied by a cell cycle arrest in S-phase. Combination treatment using JMR-132 plus a cytotoxic drug led to a significant increase of the sub-G₁ fraction, suggesting apoptosis. In vivo, daily treatment with GHRH antagonist JMR-132 decreased the tumor volume by 40–55% (p < 0.001) of HT-29, HCT-116 and HCT-15 tumors xenografted into athymic nude mice. Combined treatment with JMR-132 plus chemotherapeutic agents 5-FU, irinotecan or cisplatin resulted in an additive tumor growth suppression of HT-29, HCT-116 and HCT-15 xenografts to 56–85%. Our observations indicate that JMR-132 enhances the antiproliferative effect of S-phase-specific cytotoxic drugs by causing accumulation of tumor cells in S-phase.     

GHRH antagonist causes DNA damage leading to p21 mediated cell cycle arrest and apoptosis in human colon cancer cells

We investigated the mechanisms of inhibitory effect of growth hormone-releasing hormone (GHRH) antagonist JMR-132 on the growth of HT29, HCT-116 and HCT-15 human colon cancer cells in vitro and in vivo. High-affinity binding sites for GHRH and mRNA for GHRH and splice variant-1 (SV1) of the GHRH receptor were found in all three cell lines tested. Proliferation of HT-29, HCT-116 and HCT-15 cells was significantly inhibited in vitro by JMR-132. Time course studies revealed that the treatment of human HCT-116 colon cancer cells with 10μM GHRH antagonist JMR-132 causes a significant DNA damage as shown by an increase in olive tail moment (OTM) and loss of inner mitochondrial membrane potential (?Ψm). Western blotting demonstrated a time-dependent increase in protein levels of phospho-p53 (Ser46), Bax, cleaved caspase-9, -3, cleavage of poly(ADP-ribose)polymerase (PARP) and a decrease in Bcl-2 levels. An augmentation in cell cycle checkpoint protein p21Waf1/Cip1 was accompanied by a cell cycle arrest in S-phase. DNA fragmentation visualized by the comet assay and the number of apoptotic cells increased time dependently as determined by flow cytometric annexinV and PI staining assays. In vivo, JMR-132 decreased the volume of HT-29, HCT-116 and HCT-15 tumors xenografted into athymic mice up to 75% (p     

荞麦中光毒物质的转化及荞麦光敏素对人结肠癌细胞HCT-116的抑制活性

荞麦光敏素（fagopyrins）具有光毒性和酪氨酸激酶抑制活性,可作为光动力治疗中的光敏剂,用于癌症的治疗。本研究采用电喷雾质谱法和荧光光度法,探究了荞麦中光毒物存在的型式,并分析了光敏素前体(protofagopyrin)转化为荞麦光敏素的条件。通过MTT细胞实验,研究荞麦光敏素提取物对人结直肠癌细胞和人结肠上皮细胞生长增殖的影响。结果表明,荞麦中光毒物以光敏素前体为主,并且有微量的荞麦光敏素,前者质谱的离子强度是后者的400倍。光敏素前体的转化发生在光照提取过程中,而且提取液在光照放置过程中,光敏素前体继续转化,尤其是前0.5 h对于转化的影响显著超过了提取过程。荞麦光敏素提取物与细胞作用,避光培养时,对HCT-116癌细胞有轻度的抑制作用;而对FHC正常细胞不仅未见抑制还有促进作用。光照结合避光培养时,荞麦光敏素对癌细胞的抑制随着提取物浓度的增加而增强,当提取物浓度达到200 μg/mL时,抑制率达到50%;而对正常细胞提取物,浓度低于200 μg/mL时未见抑制,500 ～ 1 000 μg/mL时抑制率达到50%。光敏素提取物与金丝桃素抑制细胞的能力相比,光照结合避光培养时,金丝桃素对正常细胞的抑制作用强于对癌细胞,而荞麦光敏素的提取物正好相反。提示荞麦光敏素比金丝桃素对癌细胞的抑制更具特异性。上述结果为从荞麦叶中开发出有利于肿瘤治疗的药物提供了实验依据。     

Activation of autophagy and PPARγ protect colon cancer cells against apoptosis induced by interactive effects of butyrate and DHA in a cell type-dependent manner: The role of cell differentiation

The short-chain and n-3 polyunsaturated fatty acids exhibit anticancer properties, and they may mutually interact within the colon. However, the molecular mechanisms of their action in colon cancer cells are still not fully understood. Our study focused on the mechanisms responsible for the diverse effects of sodium butyrate (NaBt), in particular when interacting with docosahexaenoic acid (DHA), in distinct colon cancer cell types, in which NaBt either induces cell differentiation or activates programmed cell death involving mitochondrial pathway. NaBt activated autophagy both in HT-29 cells, which are sensitive to induction of differentiation, and in nondifferentiating HCT-116 cells. However, autophagy supported cell survival only in HT-29 cells. Combination of NaBt with DHA-promoted cell death, especially in HCT-116 cells and after longer time intervals. The inhibition of autophagy both attenuated differentiation and enhanced apoptosis in HT-29 cells treated with NaBt and DHA, but it had no effect in HCT-116 cells. NaBt, especially in combination with DHA, activated PPARγ in both cell types. PPARγ silencing decreased differentiation and increased apoptosis only in HT-29 cells, therefore we verified the role of caspases in apoptosis, differentiation and also PPARγ activity using a pan-caspase inhibitor. In summary, our data suggest that diverse responses of colon cancer cells to fatty acids may rely on their sensitivity to differentiation, which may in turn depend on distinct engagement of autophagy, caspases and PPARγ. These results contribute to understanding of mechanisms underlying differential effects of NaBt, when interacting with other dietary fatty acids, in colon cancer cells.     

Combination of dasatinib and curcumin eliminates chemo-resistant colon cancer cells

Metastatic colorectal cancer remains a serious health concern with poor patient survival. Although 5-Fluorouracil (5-FU) or 5-FU plus oxaliplatin (FOLFOX) is the standard therapy for colorectal cancer, it has met with limited success. Recurrence of the tumor after chemotherapy could partly be explained by the enrichment of the chemo-resistant sub-population of cancer stem cells (CSCs) that possess the ability for self-renewal and differentiation into different lineages in the tumor. Therefore development of therapeutic strategies that target CSCs for successful treatment of this malignancy is warranted. The current investigation was undertaken to examine the effectiveness of the combination therapy of dasatinib (a Src inhibitor) and curcumin (a dietary agent with pleiotropic effect) in inhibiting the growth and other properties of carcinogenesis of chemo-resistant colon cancer cells that are enriched in CSCs sub-population. Remnants of spontaneous adenomas from APC ^{Min +/-} mice treated with dasatinib and/or curcumin were analyzed for several cancer stem cell markers (ALDH, CD44, CD133 and CD166). Human colon cancer cells HCT-116 (p53 wild type; K-ras mutant) and HT-29 (p53 mutant; K-ras wild type) were used to generate FOLFOX resistant (referred to as CR) cells. The effectiveness of the combination therapy in inhibiting growth, invasive potential and stemness was examined in colon cancer CR cells. The residual tumors from APC ^{Min +/-} mice treated with dasatinib and/or curcumin showed 80-90% decrease in the expression of the CSC markers ALDH, CD44, CD133, CD166. The colon cancer CR cells showed a higher expression of CSCs markers, cell invasion potential and ability to form colonospheres, compared to the corresponding parental cells. The combination therapy of dasatinib and curcumin demonstrated synergistic interactions in CR HCT-116 and CR HT-29 cells, as determined by Calcusyn analysis. The combinatorial therapy inhibited cellular growth, invasion and colonosphere formation and also reduced CSC population as evidenced by the decreased expression of CSC specific markers: CD133, CD44, CD166 and ALDH. Our data suggest that the combination therapy of dasatinib and curcumin may be a therapeutic strategy for re-emergence of chemo-resistant colon cancer by targeting CSC sub-population.     

The microbe-derived short chain fatty acid butyrate targets miRNA-dependent p21 gene expression in human colon cancer

Colonic microbiota ferment non-absorbed dietary fiber to produce prodigious amounts of short chain fatty acids (SCFAs) that benefit the host through a myriad of metabolic, trophic, and chemopreventative effects. The chemopreventative effects of the SCFA butyrate are, in part, mediated through induction of p21 gene expression. In this study, we assessed the role of microRNA(miRNA) in butyrate's induction of p21 expression. The expression profiles of miRNAs in HCT-116 cells and in human sporadic colon cancers were assessed by microarray and quantitative PCR. Regulation of p21 gene expression by miR-106b was assessed by 3' UTR luciferase reporter assays and transfection of specific miRNA mimics. Butyrate changed the expression of 44 miRNAs in HCT-116 cells, many of which were aberrantly expressed in colon cancer tissues. Members of the miR-106b family were decreased in the former and increased in the latter. Butyrate-induced p21 protein expression was dampened by treatment with a miR-106b mimic. Mutated p21 3'UTR-reporter constructs expressed in HCT-116 cells confirmed direct miR-106b targeting. Butyrate decreased HCT-116 proliferation, an effect reversed with the addition of the miR-106b mimic. We conclude that microbe-derived SCFAs regulate host gene expression involved in intestinal homeostasis as well as carcinogenesis through modulation of miRNAs.     

15-LOX-1 inhibits p21 (Cip/WAF 1) expression by enhancing MEK-ERK 1/2 signaling in colon carcinoma cells

Currently, some controversy exists regarding the precise role of 15-lipoxygenase-1 (15-LOX-1) in colorectal carcinogenesis and other aspects of cancer biology. The aim of this study was to evaluate the effect of 15-LOX-1 on p21 (Cip/WAF 1) expression and growth regulation in human colon carcinoma cells. The effect of 13-S-hydroxyoctadecadienoic acid (HODE), a product of 15-LOX-1, on p21 (Cip/WAF 1) expression was evaluated in Caco-2 cells treated with sodium butyrate (NaBT) and/or nordihydroguaiarectic acid (NDGA), a LOX inhibitor. The effect of transfecting HCT-116 cells with 15-LOX-1 was also examined. NaBT-induced p21 (Cip/WAF 1) expression was enhanced by treatment with NDGA and 13-S-HODE reversed NaBT-induced p21 (Cip/WAF 1) expression in Caco-2 cells. Overexpression of 15-LOX-1 induced extracellular signal-related kinase (ERK) 1/2 phosphorylation, decreased p21 (Cip/WAF 1) expression, and increased HCT-116 cell growth. Treatment with NDGA decreased ERK 1/2 phosphorylation, and increased p21 (Cip/WAF 1) expression in 15-LOX-1 overexpressing HCT-116 cells. Our experimental results support the hypothesis that 15-LOX-1 may have "pro-neoplastic" effects during the development of colorectal cancer.     

Reduction of Orc6 Expression Sensitizes Human Colon Cancer Cells to 5-Fluorouracil and Cisplatin

Previous studies from our group have shown that the expression levels of Orc6 were highly elevated in colorectal cancer patient specimens and the induction of Orc6 was associated with 5-fluorouracil (5-FU) treatment. The goal of this study was to investigate the molecular and cellular impact of Orc6 in colon cancer. In this study, we use HCT116 (wt-p53) and HCT116 (null-p53) colon cancer cell lines as a model system to investigate the impact of Orc6 on cell proliferation, chemosensitivity and pathways involved with Orc6. We demonstrated that the down regulation of Orc6 sensitizes colon cancer cells to both 5-FU and cisplatin (cis-pt) treatment. Decreased Orc6 expression in HCT-116 (wt-p53) cells by RNA interference triggered cell cycle arrest at G1 phase. Prolonged inhibition of Orc6 expression resulted in multinucleated cells in HCT-116 (wt-p53) cell line. Western immunoblot analysis showed that down regulation of Orc6 induced p21 expression in HCT-116 (wt-p53) cells. The induction of p21 was mediated by increased level of phosphorylated p53 at ser-15. By contrast, there is no elevated expression of p21 in HCT-116 (null-p53) cells. Orc6 down regulation also increased the expression of DNA damaging repair protein GADD45β and reduced the expression level of JNK1. Orc6 may be a potential novel target for future anti cancer therapeutic development in colon cancer.     

Overexpression of miR-22 reverses paclitaxel-induced chemoresistance through activation of PTEN signaling in p53-mutated colon cancer cells

Chemoresistance is a key cause of treatment failure in colon cancer. MiR-22 is a tumor-suppressing microRNA. To explore whether miR-22 is an important player in the development of chemoresistance in colon cancer, we overexpressed miR-22 and subsequently tested its role in cell proliferation, apoptosis, survival, and associated signaling in p53-mutated HT-29 and HCT-15 cells, and p53 wild-type HCT-116 cells. We further investigated the role of miR-22 on cytotoxicity of paclitaxel in both the p53-mutated and p53 wild-type colon cancer cells. Results showed that HT-29 and HCT-15 cells were resistant to paclitaxel-induced cytotoxicity, which normally inhibits cell proliferation and survival, and induces apoptosis. Conversely, HCT-116 was relatively sensitive to the cytotoxicity of paclitaxel. Overexpression of miR-22 significantly decreased cell proliferation and survival, and induced cell apoptosis in the p53-mutated colon cancer cells, but played no role in the p53 wild-type cells. Importantly, miR-22 overexpression enhanced the cytotoxic role of paclitaxel in p53-mutated HT-29 and HCT-15 cells, but not in p53 wild-type HCT-116 cell. We further demonstrated that the tumor-suppressive role of miR-22 in p53-mutated colon cancer cells was mediated by upregulating PTEN expression, which negatively regulated Akt phosphorylation at Ser(473) and MTDH expression, and subsequently increased Bax and active caspase-3 levels. Our study is the first to identify the tumor-suppressive role of miR-22 and its associated signaling in the p53-mutated colon cancer cells and highlighted the chemosensitive role of miR-22.     

The bisphosphonate zoledronic acid inhibits the growth of HCT-116 colon carcinoma cells and induces tumor cell apoptosis

Besides its preventive action on bone resorption the third generation bisphosphonate zoledronic acid (ZOL) has been shown to display potent inhibitory action on the formation of bone metastases of various human cancers. Recent research also indicates an antitumoral effect on primary tumors and visceral metastases. Here we investigate for the first time the effect of ZOL on the human colon carcinoma cell line HCT-116. ZOL strongly inhibited the proliferation and soft agar colony formation of HCT-116 cells and caused a G1 cell cycle arrest in a population of ZOL treated cells. This cell cycle arrest was accompanied by an induction of apoptosis via a caspase dependent mechanism. Activation of Caspases 3, 7, 8 and 9, cleavage of PARP as well as the release of cytochrome C into the cytosol were detected in HCT-116 cells treated with low micromolar concentrations of ZOL. The induction of the mitochondrial pathway of apoptosis was accompanied by a translocation of Bax into the mitochondria, Bid activation and a decrease of overall Bcl-2 expression. We also detected a cytosolic increase of apoptosis inducing factor (AIF), a trigger of caspase-independent apoptosis. Taken together, our data indicate a potent antitumoral and apoptosis inducing effect of ZOL on HCT-116 colon carcinoma cells. Lilian Sewing and Florian Steinberg contributed equally to this work.     

Synthesis of PJOV56, a new quinoxalinyl-hydrazone derivative able to induce autophagy and apoptosis in colorectal cancer cells,and related compounds

Quinoxaline derivatives are reported as antineoplastic agents against a variety of human cancer cell lines, with some compounds being submitted to clinical trials. In this work, we report the synthesis, characterization and cytotoxicity potential of a new series of quinoxalinyl-hydrazones. The most cytotoxic compound was (E)-2-[2-(2-pyridin-2-ylmethylene)hydrazinyl]quinoxaline (PJOV56) that presented a time-dependent effect against HCT-116 cells. After 48 h of incubation, PJOV56 was able to induce autophagy and apoptosis of HCT-116 cells, mediated by upregulation of Beclin 1, upregulation of LC3A/B II and activation of caspase 7. Apoptosis was induced along with G0/G1 cell cycle arrest at the highest concentration of PJOV56 (6.0 µM). Thus, PJOV56 showed a dose-dependent mode of action related to induction of autophagy and apoptosis in HCT-116 cells.     

Colon cancer mesenchymal stem cells modulate the tumorigenicity of colon cancer through interleukin 6

Multipotent mesenchymal stem cells (MSCs) have been isolated from several tumors and are implicated to play critical roles to increase malignant cell growth, invasion and metastasis. Here, we show that the MSC-like cells were isolated from human colon cancer tissues. These isolated hCC-MSCs (human colon cancer-derived mesenchymal stem cells) shared similar characteristic features with bone marrow-derived MSCs, which include cell morphology, surface antigens and specific gene expression. Additionally, the hCC-MSCs could differentiate into osteocytes or adipocytes under appropriate culture conditions. The conditioned medium collected from the cultured hCC-MSCs was shown to enhance the migration and invasive activity of HCT-116 colon cancer cells in vitro. Besides, transplantation of HCT-116 cells along with hCC-MSCs in nude mice increased the tumor growth and metastasis. Further study revealed that IL-6 present in the hCC-MSC-conditioned medium sufficiently induced the levels of Notch-1 and CD44 in HCT-116 and HT-29 cells, which contribute to enhance tumorigenic activity of HCT-116 and HT-29 cells. By using immunohistochemical staining, the intense co-expression of IL-6, Notch-1 and CD44 was predominantly detected in human colon cancer tissues. Taken together, our findings suggest the importance of the IL-6/Notch-1/CD44 signaling axis in the interaction between hCC-MSCs and colon cancer cells.