Colorectal Cancer Cell Death Research Articles

CQ synergistically sensitizes human colorectal cancer cells to SN-38/CPT-11 through lysosomal and mitochondrial apoptotic pathway via p53-ROS cross-talk

Autophagy plays a key role in supporting cell survival against chemotherapy-induced apoptosis. In this study, we found the chemotherapy agent SN-38 induced autophagy in colorectal cancer (CRC) cells. However, inhibition of autophagy using a small molecular inhibitor 3-methyladenine (3-MA) and ATG5 siRNA did not increase SN-38-induced cytotoxicity in CRC cells. Notably, another autophagy inhibitor chloroquine (CQ) synergistically enhanced the anti-tumor activity of SN-38 in CRC cells with wild type (WT) p53. Subsequently, we identified a potential mechanism of this cooperative interaction by showing that CQ and SN-38 acted together to trigger reactive oxygen species (ROS) burst, upregulate p53 expression, elicit the loss of lysosomal membrane potential (LMP) and mitochondrial membrane potential (∆ψm). In addition, ROS induced by CQ plus SN-38 upregulated p53 levels by activating p38, conversely, p53 stimulated ROS. These results suggested that ROS and p53 reciprocally promoted each other's production and cooperated to induce CRC cell death. Moreover, we showed induction of ROS and p53 by the two agents provoked the loss of LMP and ∆ψm. Altogether, all results suggested that CQ synergistically sensitized human CRC cells with WT p53 to SN-38 through lysosomal and mitochondrial apoptotic pathway via p53-ROS cross-talk. Lastly, we showed that CQ could enhance CRC cells response to CPT-11 (a prodrug of SN-38) in xenograft models. Thus the combined treatment might represent an attractive therapeutic strategy for the treatment of CRC.

Brusatol-Mediated Inhibition of c-Myc Increases HIF-1α Degradation and Causes Cell Death in Colorectal Cancer under Hypoxia.

HIF-1 (hypoxia-inducible factor-1) regulates the expression of ~100 genes involved in angiogenesis, metastasis, tumor growth, chemoresistance and radioresistance, underscoring the growing interest in targeting HIF-1 for cancer control. In the present study, we investigated the molecular mechanisms underlying brusatol-induced HIF-1α degradation and cell death in colorectal cancer under hypoxia (0.5% O2). Under hypoxia, pretreatment of cancer cells with brusatol increased HIF-1α degradation and cancer cell death in a dose-dependent manner. This effect was mediated by activation of prolyl hydroxylases (PHDs), as evidenced by the block of brusatol-induced HIF-1α degradation and cancer cell death by both pharmacological inhibition and siRNA-mediated knockdown of PHDs. In addition, a ferrous iron chelator (2,2'-bypyridyl) blocked brusatol-induced degradation of HIF-1α and cancer cell death in hypoxia by inhibiting PHD activation. We further found that brusatol inhibited c-Myc expression, and showed that overexpression of c-Myc prevented brusatol-induced degradation of HIF-1α and cancer cell death by increasing mitochondrial ROS production and subsequent ROS-mediated transition of ferrous iron to ferric iron. Consistent with these results, treatment of tumor-bearing mice with brusatol significantly suppressed tumor growth by promoting PHD-mediated HIF-1α degradation. Collectively, our results suggest that brusatol-mediated inhibition of c-Myc/ROS signaling pathway increases HIF-1α degradation by promoting PHD activity and induces cell death in colorectal cancer under hypoxia

CO-Induced apoptotic death of colorectal cancer cells by a luminescent photoCORM grafted on biocompatible carboxymethyl chitosan.

A photo-active luminescent rhenium carbonyl complex namely, [Re(CO)3(phen)(pyAl)](CF3SO3) was grafted on a biocompatible carboxymethyl chitosan (CMC) matrix through Schiff base condensation reaction. The light-induced CO delivery from ReCMC has been shown to eradicate human colorectal adenocarcinoma cells (HT-29) very efficiently in a dose-dependent fashion. The onset of CO-induced apoptosis was realized by caspase-3,-7 detection aided by fluorescence confocal microscopy. ReCMC represents a unique example of a biocompatible and biodegradable antineoplastic agent that could find its use in cancer photopharmacology.

Modulation of cell death in human colorectal and breast cancer cells through a manganese chelate by involving GSH with intracellular p53 status

Chemotherapy is central to current treatment modality especially for advanced and metastatic colorectal and breast cancers. Targeting the key molecular events of the neoplastic cells may open a possibility to treat cancer. Although some improvements in understanding of colorectal and breast cancer treatment have been recorded, the involvement of glutathione (GSH) and dependency of p53 status on the modulation of GSH-mediated treatment efficacy have been largely overlooked. Herein, we tried to decipher the underlying mechanism of the action of Mn-N-(2-hydroxyacetophenone) glycinate (MnNG) against differential p53 status bearing Hct116, MCF-7, and MDA-MB-468 cells on the backdrop of intracellular GSH level and reveal the role of p53 status in modulating GSH-dependant abrogation of MnNG-induced apoptosis in these cancer cells. Present study discloses that MnNG targets specifically wild-type-p53 expressing Hct116 and MCF-7 cells by significantly depleting both cytosolic, mitochondrial GSH, and modulating nuclear GSH through Glutathione reductase and Glutamate-cysteine ligase depletion that may in turn induce p53-mediated intrinsic apoptosis in them. Thus GSH addition abrogates p53-mediated apoptosis in wild-type-p53 expressing cells. GSH addition also overrides MnNG-induced modulation of phase II detoxifying parameters in them. However, GSH addition partially replenishes the down-regulated or modulated GSH pool in cytosol, mitochondria, and nucleus, and relatively abrogates MnNG-induced intrinsic apoptosis in p53-mutated MDA-MB-468 cells. On the contrary, although MnNG induces significant cell death in p53-null Hct116 cells, GSH addition fails to negate MnNG-induced cell death. Thus p53 status with intracellular GSH is critical for the modulation of MnNG-induced apoptosis.

Soluble VEGF receptor 1(sFLT1) induces non-apoptotic cell death of ovarian and colorectal cancer cells

Soluble VEGF receptor 1(sFLT1) induces non-apoptotic cell death of ovarian and colorectal cancer cells

The A2b adenosine receptor antagonist PSB-603 promotes oxidative phosphorylation and ROS production in colorectal cancer cells via adenosine receptor-independent mechanism

PurposeAdenosine is a multifaceted regulator of tumor progression. It modulates immune cell activity as well as acting directly on tumor cells. The A2b adenosine receptor (A2b-AR) is thought to be an important mediator of these effects. In this study we sought to analyze the contribution of the A2b-AR to the behavior of colorectal cancer cells. Principal resultsThe A2b-AR antagonist PSB-603 changed cellular redox state without affecting cellular viability. Quantification of cellular bioenergetics demonstrated that PSB-603 increased basal oxygen consumption rates, indicative of enhanced mitochondrial oxidative phosphorylation. Unexpectedly, pharmacological and genetic approaches to antagonize AR-related signalling of PSB-603 did not abolish the response, suggesting that it was AR-independent. PSB-603 also induced acute increases in reactive oxygen species, and PSB-603 synergized with chemotherapy treatment to increase colorectal cancer cell death, consistent with the known link between cellular metabolism and chemotherapy response. Major conclusionsPSB-603 alters cellular metabolism in colorectal cancer cells and increases their sensitivity to chemotherapy. Although requiring more mechanistic insight into its A2b-AR-independent activity, our results show that PSB-603 may have clinical value as an anti-colorectal cancer therapeutic.

Abstract 3816: Reactive oxygen species and ERK2 phosphorylation are required for NSC59984 to induce mutant p53 protein degradation and restore p53 signaling

Abstract Tumor suppressor p53 is mutated in over 50% of human cancers. p53 mutation abolishes wild-type p53 function and also endows mutant p53 with a gain-of-function (GOF) that drives tumor growth and drug resistance. Targeting mutant p53 is an attractive strategy for cancer therapy. We recently reported (Zhang et al., Cancer Research, 2015) a small-molecule NSC59984 with dual capabilities to restore p53 signaling and destabilize mutant p53 protein (depleting GOF). We now demonstrate the role of reactive oxygen species (ROS) and ERK2 in the mechanism of action of NSC59984. We observe a sustained-phosphorylation of ERK2 in cancer cells treated with NSC59984. Blockade of ERK2 rescues mutant p53 from NSC59984-mediated degradation, and inhibits restoration of p53 signaling in mutant p53-expressing cells. Thus, sustained ERK2 phosphorylation is required for NSC59984-induced degradation of mutant p53 protein, and depletion of mutant p53 contributes to the restoration of p53 pathway. NSC59984 induces MDM2 phosphorylation that correlates with ERK2 phosphorylation. The effect of NSC59984 on MDM2 phosphorylation is blocked by U0126 and knockdown of ERK2. NSC59984-mediated mutant p53 protein degradation is inhibited by MDM2 knockdown, and enhanced by MDM2 overexpression. Thus, ERK2-dependent MDM2 phosphorylation is a major determinant of NSC59984-mediated mutant p53 degradation. We investigated the role of ROS in the effect of NSC59984 on ERK2 phosphorylation. ROS is induced by NSC59984 and a decrease in ROS by NAC inhibits NSC59984-induced ERK2 phosphorylation, and mutant p53 protein degradation. Increased ROS by BSO treatment enhances the NSC59984 effect on ERK2 phosphorylation, mutant p53 protein degradation and restoration of p53 signaling. We conclude that ROS is required for NSC59984 to sustain ERK2 phosphorylation, which, in turn, is required for NSC59984-induced mutant p53 protein degradation via MDM2. The combination of NSC59984 and BSO synergistically induces cell death in colorectal cancer cells. ROS and ERK2 are two important factors required for NSC59984 to degrade mutant p53 protein, restore p53 signaling and induce cell death. These results provide a rationale for clinical testing of NSC59984 in tumors with high ROS. Citation Format: Shengliang Zhang, Lanlan Zhou, David Dicker, Wafik S. El-Deiry. Reactive oxygen species and ERK2 phosphorylation are required for NSC59984 to induce mutant p53 protein degradation and restore p53 signaling. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3816.

Abstract 2840: CDK4/6 inhibitor PD-0332991 (palbociclib) promotes cell death and synergizes with CPT-11 in colorectal cancer under hypoxia in vitro

Abstract We recently reported that a family of nucleoside analogues (sangivamycin-like molecules) can sensitize tumor cells to TRAIL through dual blockade of CDK1 and GSK3-beta (Mayes et al., Cancer Research, 2011). We further reported that CDK inhibitors can destabilize HIF1-alpha regardless of VHL or p53 status or the presence of hypoxia (Warfel et al., Cell Cycle, 2013). In order to translate this knowledge into a cancer therapeutic strategy, we investigated the effects of CDK inhibition in colorectal cancer (CRC) cell lines with or without chemotherapy. PD-0332991 (Palbociclib) is a specific inhibitor of CDK4/6 that has been tested in numerous clinical trials for breast cancer, NSCLC, GBM, lymphoma, leukemia, in combination with 5-FU and oxaliplatin in solid malignancies (NCT01522989) or with cetuximab in head and neck cancer (NCT02101034). Palbociclib was approved by the FDA in 2015 in combination with letrozole as initial endocrine therapy for post-menopausal women with ER(+)/Her2(-) breast cancer. Little is known about the effects of CDK4/6 inhibition in CRC. We investigated the therapeutic effect and anti-proliferative mechanism of CDK4/6 inhibition in CRC. We used CellTiter-Glo assays to detect CRC cell viability and determined IC50 values (50% inhibitory concentration) of single drug through nonlinear regression analysis by GraphPad Prism software. The combination index (CI) of multiple drug combinations was identified with Compusyn analysis. We found that Palbociclib promotes cell death of CRC cells under hypoxia but not under normoxia where Palbociclib inhibited cell proliferation via the pRb pathway. These results suggest that the CDK4/6 inhibitor could regulate cell fate of CRC via different molecular mechanisms under hypoxia versus normoxia. We further found that Palbociclib can upregulate ERK/MAPK signaling under hypoxia, as compared with normoxia. The IC50 values of Palbociclib were generally higher under hypoxia (Mean ± SD: 10.54 ± 3.35 μM, N = 5) versus normoxia (Mean ± SD: 6.61 ± 0.85 μM, N = 5) in CRC cell lines. Thus, hypoxia promotes resistance of CRC cells toward the cytotoxic activity of the CDK4/6 inhibitor. We found that Palbociclib synergizes with CPT-11 much better than with either 5-FU or oxaliplatin against CRC cell lines with different molecular subtypes. Based on our findings that Palbociclib can promote cell death of CRC cells under hypoxia and synergizes with CPT11, further investigation is needed to assess the novel combination therapy against CRC. Citation Format: Jun Zhang, Lanlan Zhou, Shuai Zhao, David Dicker, Wafik S. El-Deiry. CDK4/6 inhibitor PD-0332991 (palbociclib) promotes cell death and synergizes with CPT-11 in colorectal cancer under hypoxia in vitro. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2840.

Abstract 3564: MUC13 protects colorectal cancer cells from death by activating the NF-κb pathway and is a potential therapeutic target

Abstract MUC13 is a transmembrane mucin glycoprotein that is overexpressed by many cancers, although its functions are not fully understood. NF-κB is a key transcription factor promoting cancer cell survival, but therapeutically targeting this pathway has proved difficult because NF-κB has pleiotropic functions. Here, we report that MUC13 prevents colorectal cancer cell death by promoting two distinct pathways of NF-kB activation, consequently up-regulating BCL-XL. MUC13 promoted TNF-induced NF-κB activation by interacting with TNFR1 and the E3 ligase, cIAP1, to increase ubiquitination of RIPK1. MUC13 also promoted genotoxin-induced NF-κB activation by increasing phosphorylation of ATM and SUMOylation of NEMO. Moreover, elevated expression of cytoplasmic MUC13 and NF-κB correlated with colorectal cancer progression and metastases. Our demonstration that MUC13 enhances NF-κB signalling in response to both TNF and DNA damaging agents provides a new molecular target for specific inhibition of NF-κB activation. As proof of principle, silencing MUC13 sensitized colorectal cancer cells to death in response to cytotoxic drugs and inflammatory signals and abolished chemotherapy-induced enrichment of CD133+ CD44+ cancer stem cells, slowed xenograft growth in mice, and synergized with 5-fluourouracil to induce tumor regression. Therefore, these data indicate that combining chemotherapy and MUC13 antagonism could improve the treatment of metastatic cancers. Citation Format: Yong H. Sheng, Yaowu He, sumaira Z. hasnain, Ran Wang, Hui Tong, Daniel T. Clarke, Rohan Lourie, Iulia Oancea, kuanyau wong, John W. Lumley, Timothy H. Florin, Philip Sutton, John. D. Hooper, Nigel A. Mcmillan, Michael A. Mcguckin. MUC13 protects colorectal cancer cells from death by activating the NF-κb pathway and is a potential therapeutic target. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3564.

Abstract 4769: Inhibition of ribosomal protein L9 expression suppresses colorectal carcinoma cell growth in vitro and in vivo

Abstract Background: Ribosomal protein L9 (RPL9), a component of the 60S subunit, is upregulated in human colorectal cancer (CRC). We thus hypothesized if targeting of RPL9 with small interfering (si) RNA could inhibit CRC progression. We also investigated molecular mechanism to mediate CRC cell death caused by RPL9 silencing. Methods: HCT116 and HT29 human CRC cells were transfected with RPL9 siRNA and tested for growth inhibition and apoptotic induction using MTS, FACS and microscopic analysis. To obtain insights into the molecular changes in response to RPL9 knockdown, global changes in gene expression were examined using RNA sequencing. Results: RPL9 silencing caused inhibition of CRC cell growth through induction of apoptotic cell death. RNA sequencing revealed that RPL9-specific knockdown led to dysregulation of 622 genes in HCT116 and 2882 genes in HT29 cells. Among those, 256 genes showed the same directional regulation (128 up- and 168 down-regulated genes), including up-regulation of tumor suppressors such as KLF6 and ATF3, and were considered as a common RPL9 knockdown signature. Western blotting proved that downregulation of RPL9 was accompanied with the decrease in the levels of PARP-1 and pro-caspase 3 delaying cell cycle progression and accelerating apoptotic signaling. Of importance, targeting RPL9 significantly inhibited CRC growth in a murine xenograft model. Conclusion: These results suggest that inhibition of RPL9 expression could be an attractive option for molecular targeted therapy of colorectal cancer. Citation Format: In Hye Baik, Keon Uk Park, Ilseon Hwang, Hun-Mo Ryoo, Yun-Han Lee. Inhibition of ribosomal protein L9 expression suppresses colorectal carcinoma cell growth in vitro and in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4769.

MUC13 protects colorectal cancer cells from death by activating the NF-\u03baB pathway and is a potential therapeutic target

MUC13 is a transmembrane mucin glycoprotein that is over produced by many cancers, although its functions are not fully understood. Nuclear factor-κB (NF-κB) is a key transcription factor promoting cancer cell survival, but therapeutically targeting this pathway has proved difficult because NF-κB has pleiotropic functions. Here, we report that MUC13 prevents colorectal cancer cell death by promoting two distinct pathways of NF-kB activation, consequently upregulating BCL-XL. MUC13 promoted tumor necrosis factor (TNF)-induced NF-κB activation by interacting with TNFR1 and the E3 ligase, cIAP1, to increase ubiquitination of RIPK1. MUC13 also promoted genotoxin-induced NF-κB activation by increasing phosphorylation of ATM and SUMOylation of NF-κB essential modulator. Moreover, elevated expression of cytoplasmic MUC13 and NF-κB correlated with colorectal cancer progression and metastases. Our demonstration that MUC13 enhances NF-κB signaling in response to both TNF and DNA-damaging agents provides a new molecular target for specific inhibition of NF-κB activation. As proof of principle, silencing MUC13 sensitized colorectal cancer cells to killing by cytotoxic drugs and inflammatory signals and abolished chemotherapy-induced enrichment of CD133+ CD44+ cancer stem cells, slowed xenograft growth in mice, and synergized with 5-fluourouracil to induce tumor regression. Therefore, these data indicate that combining chemotherapy and MUC13 antagonism could improve the treatment of metastatic cancers.

Teaching an old antibody new tricks

Anti-EGFR antibodies induce immunogenic cell death in colorectal cancer.

In Hyperthermia Increased ERK and WNT Signaling Suppress Colorectal Cancer Cell Growth.

Although neoplastic cells exhibit relatively higher sensitivity to hyperthermia than normal cells, hyperthermia has had variable success as an anti-cancer therapy. This variable outcome might be due to the fact that cancer cells themselves have differential degrees of sensitivity to high temperature. We hypothesized that the varying sensitivity of colorectal cancer (CRC) cells to hyperthermia depends upon the differential induction of survival pathways. Screening of such pathways revealed that Extracellular Signal-Regulated Kinase (ERK) signaling is augmented by hyperthermia, and the extent of this modulation correlates with the mutation status of V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS). Through clonal growth assays, apoptotic analyses and transcription reporter assays of CRC cells that differ only in KRAS mutation status we established that mutant KRAS cells are more sensitive to hyperthermia, as they exhibit sustained ERK signaling hyperactivation and increased Wingless/Integrated (WNT)/beta-catenin signaling. We propose that whereas increased levels of WNT and ERK signaling and a positive feedback between the two pathways is a major obstacle in anti-cancer therapy today, under hyperthermia the hyperinduction of the pathways and their positive crosstalk contribute to CRC cell death. Ascertaining the causative association between types of mutations and hyperthermia sensitivity may allow for a mutation profile-guided application of hyperthermia as an anti-cancer therapy. Since KRAS and WNT signaling mutations are prevalent in CRC, our results suggest that hyperthermia-based therapy might benefit a significant number, but not all, CRC patients.

Determination of the Role of CBP- and p300-Mediated Wnt Signaling on Colonic Cells.

BackgroundThe Wnt signaling pathway, mediated through active beta-catenin, is responsible for initiating the majority of cases of human colorectal cancer (CRC), and we have previously shown that hyperactivation of this pathway by histone deacetylase inhibitors (HDACis), such as butyrate, can induce the death of CRC cells. An important cellular switch that mediates the effects of Wnt-signaling activation is variation in the association between beta-catenin and the transcriptional coactivators cAMP response element binding (CREB) binding protein (CBP) and p300. Association of CBP with beta-catenin is thought to activate a set of genes linked to cell proliferation, while the p300-mediated Wnt genetic program is believed to promote cell differentiation. Small molecule agents have been discovered that modulate CBP/p300 Wnt transcriptional programs by altering the association of CBP and p300 to beta-catenin. ICG-001 and ICG-427 inhibit CBP- and p300-mediated Wnt activity, respectively, while IQ-1 prevents the shift from CBP-mediated to a p300-mediated Wnt activity.ObjectiveAim 1 of this proposal is designed to determine the role of CBP- and p300-mediated Wnt signaling in the response of CRC cells to HDACis. Aim 2 is to determine the role of CBP and p300 in the maintenance of high- and low-Wnt fractions in CRC cell line. Aim 3 will compare the effects of CBP- and p300-mediated Wnt activity on CRC initiation and progression.MethodsIn Aim 1, cells will be cotreated with HDACis and ICG-001, ICG-427, or IQ-1 and the levels of Wnt activity, apoptosis, proliferation, differentiation, and CBP- or p300-beta-catenin binding measured. Aim 2 of this proposal may mirror similar heterogeneity observed in human tumors and which may be of clinical significance. Aim 3 will use CRC cell line model systems of initiation and progression: the normal colon cell lines CCD-841CoN, the adenoma line LT97, the primary colon carcinoma cell line SW480, and the lymph node metastasis cell line SW620. Cells will be treated with HDACis and the small molecule agents, and assayed as described above.ResultsWe will also attempt to use changes in CBP- and p300-mediated Wnt signaling to shift colonic cells between cell type, modifying CBP- and p300-mediated gene expression in the LT97 adenoma line to shift the adenoma phenotype to more characteristic of the CCD-841CoN normal cells, or the SW480 carcinoma cells. We will use microarray analyses to determine the patterns of gene expression responsible for these CBP- or p300-mediated changes in colonic neoplastic phenotype.ConclusionsThe findings generated from this study will lead to future, more in-depth projects to further dissect the action of CBP/p300 Wnt–mediated transcriptional programs in colonic neoplasia, with an emphasis on methods to modulate these genetic programs for chemopreventive effect.

Erastin Disrupts Mitochondrial Permeability Transition Pore (mPTP) and Induces Apoptotic Death of Colorectal Cancer Cells.

We here evaluated the potential anti-colorectal cancer activity by erastin, a voltage-dependent anion channel (VDAC)-binding compound. Our in vitro studies showed that erastin exerted potent cytotoxic effects against multiple human colorectal cancer cell lines, possibly via inducing oxidative stress and caspase-9 dependent cell apoptosis. Further, mitochondrial permeability transition pore (mPTP) opening was observed in erastin-treated cancer cells, which was evidenced by VDAC-1 and cyclophilin-D (Cyp-D) association, mitochondrial depolarization, and cytochrome C release. Caspase inhibitors, the ROS scavenger MnTBAP, and mPTP blockers (sanglifehrin A, cyclosporin A and bongkrekic acid), as well as shRNA-mediated knockdown of VDAC-1, all significantly attenuated erastin-induced cytotoxicity and apoptosis in colorectal cancer cells. On the other hand, over-expression of VDAC-1 augmented erastin-induced ROS production, mPTP opening, and colorectal cancer cell apoptosis. In vivo studies showed that intraperitoneal injection of erastin at well-tolerated doses dramatically inhibited HT-29 xenograft growth in severe combined immunodeficient (SCID) mice. Together, these results demonstrate that erastin is cytotoxic and pro-apoptotic to colorectal cancer cells. Erastin may be further investigated as a novel anti-colorectal cancer agent.

Soluble VEGF receptor 1 (sFLT1) induces non-apoptotic death in ovarian and colorectal cancer cells.

Soluble Vascular Endothelial Growth Factor Receptor 1 (sVEGFR1/sFLT1) is an angiogenesis inhibitor that competes with angiogenic factors such as VEGF and Placental Growth Factor (PlGF). Imbalances of VEGF and sFLT1 levels can cause pathological conditions such as tumour growth or preeclampsia. We observed direct damage caused by sFLT1 in tumour cells. We exposed several kinds of cells derived from ovarian and colorectal cancers as well as HEK293T cells to sFLT1 in two ways, transfection and exogenous application. The cell morphology and an LDH assay revealed cytotoxicity. Additional experiments were performed to clarify how sFLT1 injured cells. In this study, non-apoptotic cell damage was found to be induced by sFLT1. Moreover, sFLT1 showed an anti-tumour effect in a mouse model of ovarian cancer. Our results suggest that sFLT1 has potential as a cancer therapeutic candidate.

Ginsenoside Rh2 inhibiting HCT116 colon cancer cell proliferation through blocking PDZ-binding kinase/T-LAK cell-originated protein kinase

BackgroundGinsenoside Rh2 (GRh2) is the main bioactive component in American ginseng, a commonly used herb, and its antitumor activity had been studied in previous studies. PDZ-binding kinase/T-LAK cell-originated protein kinase (PBK/TOPK), a serine/threonine protein kinase, is highly expressed in HCT116 colorectal cancer cells. MethodsWe examined the effect of GRh2 on HCT116 cells ex vivo. Next, we performed in vitro binding assay and in vitro kinase assay to search for the target of GRh2. Furthermore, we elucidated the underlying molecular mechanisms for the antitumor effect of GRh2 ex vivo and in vivo. ResultsThe results of our in vitro studies indicated that GRh2 can directly bind with PBK/TOPK and GRh2 also can directly inhibit PBK/TOPK activity. Ex vivo studies showed that GRh2 significantly induced cell death in HCT116 colorectal cancer cells. Further mechanistic study demonstrated that these compounds inhibited the phosphorylation levels of the extracellular regulated protein kinases 1/2 (ERK1/2) and (H3) in HCT116 colorectal cancer cells. In vivo studies showed GRh2 inhibited the growth of xenograft tumors of HCT116 cells and inhibited the phosphorylation levels of the extracellular regulated protein kinases 1/2 and histone H3. ConclusionThe results indicate that GRh2 exerts promising antitumor effect that is specific to human HCT116 colorectal cancer cells through inhibiting the activity of PBK/TOPK.

Combination of metformin and 5-aminosalicylic acid cooperates to decrease proliferation and induce apoptosis in colorectal cancer cell lines.

BackgroundThe link between inflammation and cancer has been confirmed by the use of anti-inflammatory therapies in cancer prevention and treatment. 5-aminosalicylic acid (5-ASA) was shown to decrease the growth and survival of colorectal cancer (CRC) cells. Studies also revealed that metformin induced apoptosis in several cancer cell lines.MethodsWe investigated the combinatory effect of 5-ASA and metformin on HCT-116 and Caco-2 CRC cell lines. Apoptotic markers were determined using western blotting. Expression of pro-inflammatory cytokines was determined by RT-PCR. Inflammatory transcription factors and metastatic markers were measured by ELISA.ResultsMetformin enhanced CRC cell death induced by 5-ASA through significant increase in oxidative stress and activation of apoptotic machinery. Moreover, metformin enhanced the anti-inflammatory effect of 5-ASA by decreasing the gene expression of IL-1β, IL-6, COX-2 and TNF-α and its receptors; TNF-R1 and TNF-R2. Significant inhibition of activation of NF-κB and STAT3 transcription factors, and their downstream targets was also observed. Metformin also enhanced the inhibitory effect of 5-ASA on MMP-2 and MMP-9 enzyme activity, indicating a decrease in metastasis.ConclusionThe current data demonstrate that metformin potentiates the antitumor effect of 5-ASA on CRC cells suggesting their potential use as an adjuvant treatment in CRC.

The miR-27a-calreticulin axis affects drug-induced immunogenic cell death in human colorectal cancer cells

Immunogenic cell death (ICD) evoked by chemotherapeutic agents implies emission of selected damage-associated molecular patterns (DAMP) such as cell surface exposure of calreticulin, secretion of ATP and HMGB1. We sought to verify whether miR-27a is implicated in ICD, having demonstrated that it directly targets calreticulin. To this goal, we exposed colorectal cancer cell lines, genetically modified to express high or low miR-27a levels, to two bona fide ICD inducers (mitoxantrone and oxaliplatin). Low miR-27a-expressing cells displayed more ecto-calreticulin on the cell surface and increased ATP and HMGB1 secretion than high miR-27a-expressing ones in time-course experiments upon drug exposure. A calreticulin target protector counteracted the miR-27a effects while specific siRNAs mimicked them, confirming the results reported. In addition, miR-27a negatively influenced the PERK-mediated route and the late PI3K-dependent secretory step of the unfolded protein response to endoplasmic reticulum stress, suggesting that miR-27a modulates the entire ICD program. Interestingly, upon chemotherapeutic exposure, low miR-27a levels associated with an earlier and stronger induction of apoptosis and with morphological and molecular features of autophagy. Remarkably, in ex vivo setting, under the same chemotherapeutic induction, the conditioned media from high miR-27a-expressing cells impeded dendritic cell maturation while increased the secretion of specific cytokines (interleukin (IL)-4, IL-6, IL-8) and negatively influenced CD4+ T-cell interferon γ production and proliferation, all markers of a tumor immunoevasion strategy. In conclusion, we provide the first evidence that miR-27a impairs the cell response to drug-induced ICD through the regulatory axis with calreticulin.

Sodium Butyrate Induces Endoplasmic Reticulum Stress and Autophagy in Colorectal Cells: Implications for Apoptosis.

PurposeButyrate, a short-chain fatty acid derived from dietary fiber, inhibits proliferation and induces cell death in colorectal cancer cells. However, clinical trials have shown mixed results regarding the anti-tumor activities of butyrate. We have previously shown that sodium butyrate increases endoplasmic reticulum stress by altering intracellular calcium levels, a well-known autophagy trigger. Here, we investigated whether sodium butyrate-induced endoplasmic reticulum stress mediated autophagy, and whether there was crosstalk between autophagy and the sodium butyrate-induced apoptotic response in human colorectal cancer cells.MethodsHuman colorectal cancer cell lines (HCT-116 and HT-29) were treated with sodium butyrate at concentrations ranging from 0.5–5mM. Cell proliferation was assessed using MTT tetrazolium salt formation. Autophagy induction was confirmed through a combination of Western blotting for associated proteins, acridine orange staining for acidic vesicles, detection of autolysosomes (MDC staining), and electron microscopy. Apoptosis was quantified by flow cytometry using standard annexinV/propidium iodide staining and by assessing PARP-1 cleavage by Western blot.ResultsSodium butyrate suppressed colorectal cancer cell proliferation, induced autophagy, and resulted in apoptotic cell death. The induction of autophagy was supported by the accumulation of acidic vesicular organelles and autolysosomes, and the expression of autophagy-associated proteins, including microtubule-associated protein II light chain 3 (LC3-II), beclin-1, and autophagocytosis-associated protein (Atg)3. The autophagy inhibitors 3-methyladenine (3-MA) and chloroquine inhibited sodium butyrate induced autophagy. Furthermore, sodium butyrate treatment markedly enhanced the expression of endoplasmic reticulum stress-associated proteins, including BIP, CHOP, PDI, and IRE-1a. When endoplasmic reticulum stress was inhibited by pharmacological (cycloheximide and mithramycin) and genetic (siRNA targeting BIP and CHOP) methods, the induction of BIP, PDI, IRE1a, and LC3-II was blocked, but PARP cleavage was markedly enhanced.DiscussionTaken together, these results suggested that sodium butyrate-induced autophagy was mediated by endoplasmic reticulum stress, and that preventing autophagy by blocking the endoplasmic reticulum stress response enhanced sodium butyrate-induced apoptosis. These results provide novel insights into the anti-tumor mechanisms of butyric acid.