GRP78 mediates the therapeutic efficacy of curcumin on colon cancer

Assessment of an Anticancer Effect of the Simultaneous Administration of MM-129 and Indoximod in the Colorectal Cancer Model

(1) Background: The purpose of the given study was to examine the antitumor activity of the simultaneous administration of MM-129, a 1,2,4-triazine derivative, and indoximod (IND), the kynurenine pathway inhibitor, toward colon cancer. (2) Methods: The efficiency of the co-administration of the studied compounds was assessed in xenografted zebrafish embryos. Then, the effects of the combined administration of compounds on cellular processes such as cell viability, apoptosis, and intracellular signaling pathways were evaluated. In vitro studies were performed using two colorectal cancer cell lines, namely, DLD-1 and HT-29. (3) Results: The results indicated that the simultaneous application of MM-129 and indoximod induced a stronger inhibition of tumor growth in zebrafish xenografts. The combination of these compounds intensified the process of apoptosis by lowering the mitochondrial potential, enhancing the externalization of phosphatidylserine (PS) and activation of caspases. Additionally, the expression of protein kinase B (AKT) and indoleamine 2,3-dioxygenase-(1IDO1) was disrupted under the applied compound combination. (4) Conclusions: Simultaneous targeting of ongoing cell signaling that promotes tumor progression, along with inhibition of the kynurenine pathway enzyme IDO1, results in the enhancement of the antitumor effect of the tested compounds against the colon cancer cells.

Human α-defensin 6 (HD6) suppresses CRC proliferation and metastasis through abolished EGF/EGFR signaling pathway

The incidence of colorectal cancer (CRC) has increased significantly in the past decade. Early diagnosis and new therapeutics are still urgently needed for CRC in clinical practice. Human α-defensin 6 (HD6) plays a defense role against microbes in the gastrointestinal tract. However, the role and mechanism of HD6 in CRC is still unresolved. Specimens from CRC patients with higher HD6 showed better outcomes. Overexpressed HD6 in CRC cells caused a reduction of cell proliferative, migratory, and invasive ability in vitro and in vivo. HD6-overexpressed caused S phase arrest through changes in cyclin-A and B and CDK2 levels. In addition, serpine-1 may be negatively regulated by HD6 altering the translocation of c-Jun N-terminal kinases (JNK), extracellular regulated protein kinases (ERK), and p38. Higher HD6 and lower serpine-1 levels in CRC patients reflected better outcomes. Finally, we found that HD6 interacts directly with epidermal growth factor receptor (EGFR) by co-immunoprecipitated assay. EGF treatment caused an increase of the level of serpine-1 and pEGFR levels and then increased growth activity in HD6 overexpressing cells. Together, our study shows that HD6 may compete with EGF to bind to EGFR and interrupt cancer progression in CRC. We believe these findings may give new insights for HD6 in CRC therapy.

Therapeutic effect of curcumin in gastrointestinal cancers: A comprehensive review

Gastrointestinal (GI) cancers with a high global prevalence are a leading cause of morbidity and mortality. Accordingly, there is a great need to develop efficient therapeutic approaches. Curcumin, a naturally occurring agent, is a promising compound with documented safety and anticancer activities. Recent studies have demonstrated the activity of curcumin in the prevention and treatment of different cancers. According to systematic studies on curcumin use in various diseases, it can be particularly effective in GI cancers because of its high bioavailability in the gastrointestinal tract. Nevertheless, the clinical applications of curcumin are largely limited because of its low solubility and low chemical stability in water. These limitations may be addressed by the use of relevant analogues or novel delivery systems. Herein, we summarize the pharmacological effects of curcumin against GI cancers. Moreover, we highlight the application of curcumin's analogues and novel delivery systems in the treatment of GI cancers.

Curcumin, a Multifaceted Hormetic Agent, Mediates an Intricate Crosstalk between Mitochondrial Turnover, Autophagy, and Apoptosis

Curcumin has extensive therapeutic potential because of its antioxidant, anti-inflammatory, and antiproliferative properties. Multiple preclinical studies in vitro and in vivo have proven curcumin to be effective against various cancers. These potent effects are driven by curcumin's ability to induce G2/M cell cycle arrest, induce autophagy, activate apoptosis, disrupt molecular signaling, inhibit invasion and metastasis, and increase the efficacy of current chemotherapeutics. Here, we focus on the hormetic behavior of curcumin. Frequently, low doses of natural chemical products activate an adaptive stress response, whereas high doses activate acute responses like autophagy and cell death. This phenomenon is often referred to as hormesis. Curcumin causes cell death and primarily initiates an autophagic step (mitophagy). At higher doses, cells undergo mitochondrial destabilization due to calcium release from the endoplasmic reticulum, and die. Herein, we address the complex crosstalk that involves mitochondrial biogenesis, mitochondrial destabilization accompanied by mitophagy, and cell death.

Dietary phytochemicals in colorectal cancer prevention and treatment: A focus on the molecular mechanisms involved

Worldwide, colorectal cancer (CRC) remains a major cancer type and leading cause of death. Unfortunately, current medical treatments are not sufficient due to lack of effective therapy, adverse side effects, chemoresistance and disease recurrence. In recent decades, epidemiologic observations have highlighted the association between the ingestion of several phytochemical-enriched foods and nutrients and the lower risk of CRC. According to preclinical studies, dietary phytochemicals exert chemopreventive effects on CRC by regulating different markers and signaling pathways; additionally, the gut microbiota plays a role as vital effector in CRC onset and progression, therefore, any dietary alterations in it may affect CRC occurrence. A high number of studies have displayed a key role of growth factors and their signaling pathways in the pathogenesis of CRC. Indeed, the efficiency of dietary phytochemicals to modulate carcinogenic processes through the alteration of different molecular targets, such as Wnt/β-catenin, PI3K/Akt/mTOR, MAPK (p38, JNK and Erk1/2), EGFR/Kras/Braf, TGF-β/Smad2/3, STAT1-STAT3, NF-кB, Nrf2 and cyclin-CDK complexes, has been proven, whereby many of these targets also represent the backbone of modern drug discovery programs. Furthermore, epigenetic analysis showed modified or reversed aberrant epigenetic changes exerted by dietary phytochemicals that led to possible CRC prevention or treatment. Therefore, our aim is to discuss the effects of some common dietary phytochemicals that might be useful in CRC as preventive or therapeutic agents. This review will provide new guidance for research, in order to identify the most studied phytochemicals, their occurrence in foods and to evaluate the therapeutic potential of dietary phytochemicals for the prevention or treatment of CRC by targeting several genes and signaling pathways, as well as epigenetic modifications. In addition, the results obtained by recent investigations aimed at improving the production of these phytochemicals in genetically modified plants have been reported. Overall, clinical data on phytochemicals against CRC are still not sufficient and therefore the preventive impacts of dietary phytochemicals on CRC development deserve further research so as to provide additional insights for human prospective studies.

Heat shock protein 27 influences the anti-cancer effect of curcumin in colon cancer cells through ROS production and autophagy activation

The problem of therapeutic resistance and chemotherapeutic efficacy is tricky and critical in the management of colorectal cancer (CRC). Curcumin is a promising anti-cancer agent. Heat shock protein 27 (HSP27) is correlated with CRC progression and is said to affect CRC response to different therapies. However, the role of HSP27 on the therapeutic efficacy of curcumin remains unknown. HSP27 was silenced using small hairpin RNA (shRNA) technique. The cytotoxic and apoptotic effects of curcumin were assessed by sulforhodamine B (SRB) colorimetric assay, flow cytometric cell cycle analysis, and annexin V/propidium iodide (PI) double-labeling assays. Total reactive oxygen species (ROS)/superoxide and autophagy detection were performed, and the levels of apoptosis-related proteins were examined by Western blotting. It was found that the silencing of HSP27 (HSP27-KD) resulted in increased treatment resistance to curcumin in CRC cells. In addition, cell cycle analysis showed that the curcumin treatment caused cell cycle arrest at the G2/M phase in the control group, and apoptosis was reduced in the HSP27-KD group. Curcumin treatment also resulted in a decrease in anti-apoptotic proteins, p-Akt, Akt, Bcl-2 and p-Bad, and increase in pro-apoptotic proteins Bad and c-PARP levels in the control cells but not in the HSP27-KD cells. This was also followed by low reactive oxygen/nitrogen species (ROS/RNS), superoxide and autophagy induction levels in the HSP27-KD cells as compared to the control cells. Therefore, as silencing of HSP27 increases curcumin resistance by reducing apoptosis and reactive oxidative stress production, HSP27 is a potential selective target for curcumin treatment in CRC.

At the crossway of ER-stress and proinflammatory responses

Immune cells detect specific microbes or damage to tissue integrity in order to initiate efficient immune responses. Abnormal accumulation of proteins in the endoplasmic reticulum (ER) can be seen as a sign of cellular malfunction and stress that triggers a collection of conserved emergency rescue programs. These different signaling cascades, which favor ER proteostasis and promote cell survival, are collectively known as the unfolded protein response (UPR). In recent years, a synergy between the UPR and inflammatory cytokine production has been unraveled, with different branches of the UPR entering in a cross-talk with specialized microbe sensing pathways, which turns on or amplify inflammatory cytokines production. Complementary to this synergetic activity, UPR induction alone, can itself be seen as a danger signal, and triggers directly or indirectly inflammation in different cellular and pathological models, this independently of the presence of pathogens. Here, we discuss recent advances on the nature of these cross-talks and how innate immunity, metabolism dysregulation, and ER-signaling pathways intersect in specialized immune cells, such as dendritic cells (DCs), and contribute to the pathogenesis of inflammatory diseases.

Curcumin inhibits hypoxia-induced proliferation and invasion of MG-63 osteosarcoma cells via downregulating Notch1

Curcumin is a biologically active ingredient abundantly present in the ground rhizomes of Curcuma longa with a wide range of bioactive properties, including antitumor effects. Hypoxia is a common characteristic of solid tumors, including osteosarcoma. However, whether curcumin has antitumor effects on osteosarcoma under hypoxic conditions, and its underlying molecular mechanisms, remain unclear. The present study demonstrated that the MG‑63 osteosarcoma cell line exhibited increased proliferation and enhanced invasiveness upon exposure to hypoxic conditions. However, these effects were prevented by curcumin treatment. Further investigation revealed that curcumin may inhibit Notch1 upregulation induced by hypoxia. Overexpression of Notch1 via Notch1 cDNA transfection ameliorated curcumin‑inhibited MG‑63 cell growth under hypoxic conditions. Taken together, these data revealed that curcumin may suppress the growth of osteosarcoma cells in hypoxia via inhibiting Notch1 signaling.

Unraveling the Anticancer Effect of Curcumin and Resveratrol

Resveratrol and curcumin are natural products with important therapeutic properties useful to treat several human diseases, including cancer. In the last years, the number of studies describing the effect of both polyphenols against cancer has increased; however, the mechanism of action in all of those cases is not completely comprehended. The unspecific effect and the ability to interfere in assays by both polyphenols make this challenge even more difficult. Herein, we analyzed the anticancer activity of resveratrol and curcumin reported in the literature in the last 11 years, in order to unravel the molecular mechanism of action of both compounds. Molecular targets and cellular pathways will be described. Furthermore, we also discussed the ability of these natural products act as chemopreventive and its use in association with other anticancer drugs.

Synergistic effect of fenretinide and curcumin for treatment of non-small cell lung cancer

Curcumin and fenretinide are 2 well-known and promising chemotherapeutic compounds via various molecular mechanisms. However, the anticancer capacity of either curcumin or fenretinide is limited. This prompted us to examine the combined anticancer effects of curcumin and fenretinide. Our results demonstrate for the first time that there is synergistic anticancer effect of combined treatment with these 2 agents, leading to enhanced cytotoxicity and enhanced expression level of pro-apoptotic protein cleaved PARP in non-small cell lung cancer (NSCLC) cells while showed little toxicity to rat cardiomyoblast normal cells. The combination treatment was also demonstrated to inhibit lung carcinoma growth in vivo. Furthermore, we show that fenretinide or the ER stress inhibitor 4-PBA decreased curcumin-induced Glucose-regulated protein 78 (GRP78) upregulation, and produced a similar enhanced cytotoxic effect. In addition, GRP78 knockdown by siRNA also enhanced the cytotoxic effect of curcumin in A549 and H1299 cells. Our findings suggest that the 2 small molecules, when used in combination, can potentially be effective therapeutic agents for treating NSCLC, at least in part, by regulating endoplasmic reticulum (ER) chaperone protein GRP78.

MiR-593 mediates curcumin-induced radiosensitization of nasopharyngeal carcinoma cells via MDR1

Curcumin (Cur) exhibits radiosensitization effects to a variety of malignant tumors. The present study investigates the radiosensitizing effect of Cur on nasopharyngeal carcinoma (NPC) cells and whether its mechanism is associated with microRNA-593 (miR-593) and multidrug resistance gene 1 (MDR1). A clonogenic assay was performed to measure the radiosensitizing effect. The expression of miR-593 and MDR1 was analyzed by quantitative polymerase chain reaction (qPCR) or western blot assay. A transplanted tumor model was established to identify the radiosensitizing effect in vivo. A luciferase-based reporter was constructed to evaluate the effect of direct binding of miR-593 to the putative target site on the 3' UTR of MDR1. The clonogenic assay showed that Cur enhanced the radiosensitivity of cells. Cur (100 mg/kg) combined with 4 Gy irradiation inhibited the growth of a transplanted tumor model in vivo, resulting in the higher inhibition ratio compared with the radiotherapy-alone group. These results demonstrated that Cur had a radiosensitizing effect on NPC cells in vivo and in vitro; Cur-mediated upregulation of miR-593 resulted in reduced MDR1 expression, which may promote radiosensitivity of NPC cells.

Silencing A7-nAChR levels increases the sensitivity of gastric cancer cells to ixabepilone treatment

Gastric cancer is an important health issue worldwide. Currently, improving the therapeutic efficacy of chemotherapy drugs is an important goal of cancer research. Alpha-7 nicotine acetylcholine receptor (A7-nAChR) is the key molecule that mediates gastric cancer progression, metastasis, and therapy responses; however, the role of A7-nAChR in the therapeutic efficacy of ixabepilone remains unclear. A7-nAChR expression was silenced by small interfering RNA (siRNA) technology. The cytotoxicity of ixabepilone was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and ixabepilone-induced apoptosis was analyzed by flow cytometry and annexin V/propidium iodide (PI) apoptotic assay. The expression patterns of anti-apoptotic proteins (AKT, phospho-AKT, Mcl-1, and Bcl-2) and pro-apoptotic proteins (Bad and Bax) were determined by western blot. Our study found that A7-nAChR knockdown (A7-nAChR-KD) AGS cells were more sensitive to ixabepilone administration than scrambled control AGS cells. We found that A7-nAChR knockdown enhanced ixabepilone-induced cell death as evidenced by the increased number of annexin V-positive (apoptotic) cells. After scrambled control and A7-nAChR-KD cells were treated with ixabepilone, we found that pAKT and AKT levels were significantly reduced in both groups of cells. The levels of Bcl-2 and the anti-apoptotic Mcl-1 isoform increased dramatically after ixabepilone treatment in scrambled control cells but not in A7-nAChR-KD cells. Bad and Bax levels did not change between the treatment group and vehicle group in both A7-nAChR-KD and scrambled control cells, whereas cleaved PARP levels dramatically increased in ixabepilone-treated A7-nAChR-KD cells. Our results demonstrated that knockdown of A7-nAChR enhanced the sensitivity of gastric cancer cells to ixabepilone administration. Thus, the A7-nAChR expression level in patients with gastric cancer may be a good indicator of ixabepilone sensitivity.

Glucose-regulated protein 94 mediates cancer progression via AKT and eNOS in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a crucial health issue worldwide. High glucose-regulated protein 94 (GRP94) expression has been observed in different types of cancer, suggesting a link between tumor progression and GRP94 expression. However, the mechanisms underlying the role of GRP94 in HCC progression remain unclear. We used specific small hairpin RNA (shRNA) to manipulate GRP94 expression in HCC cells. Tissue arrays, MTT assays, xCELLigence assays, and in vivo xenograft model were performed to identify clinicopathological correlations and to analyze cell growth. We found that high GRP94 expression reflected a poor response and a lower survival rate. In vitro and in vivo studies showed that silencing GRP94 suppressed cancer progression. Mechanistically, GRP94 knockdown reduced AKT, phospho-AKT, and eNOS levels but did not influence the AMPK pathway. Our results demonstrated that GRP94 is a key molecule in HCC progression that modulates the AKT pathway and eNOS levels. Our findings suggest that GRP94 may be a new prognostic and therapeutic target for HCC.

Glucose-regulated protein 78 mediates the therapeutic efficacy of 17-DMAG in colon cancer cells

Glucose-regulated protein 78 (GRP78) is expressed as part of the molecular response to endoplasmic reticulum (ER) stress and mediates protein folding within the cell. GRP78 is also an important biomarker of cancer progression and the therapeutic response of patients with different cancer types. However, the role of GRP78 in the cytotoxic effect of 17-DMAG in colon cancer cells remains unclear. GRP78 expression was knocked down by small interfering RNA (siRNA). The anticancer effects of 17-DMAG were assessed by an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, a flow cytometric cell-cycle analysis, and an Annexin V-propidium iodide (PI) apoptotic assay. We found that HT-29 cells expressed a lower level of GRP78 compared with DLD-1 cells. The MTT assay revealed that HT-29 cells were more sensitive to 17-DMAG treatment than DLD-1 cells. GRP78 knock down (GRP78KD) cells demonstrated an increased sensitivity to 17-DMAG treatment compared with the scrambled control cells. Based on the cell-cycle analysis and Annexin V-PI apoptotic assay, apoptosis dramatically increased in GRP78KD cells compared with scrambled control DLD-1 cells after these cells were treated with 17-DMAG. Finally, we observed a decrease in the level of Bcl-2 and an increase in the levels of Bad and Bax in GRP78KD cells treated with 17-DMAG. These results are consistent with an increased sensitivity to 17-DMAG after knock down of GRP78. The level of GRP78 expression may determine the therapeutic efficacy of 17-DMAG against colon cancer cells.