Efficient apoptosis and necrosis induction by proteasome inhibitor: bortezomib in the DLD-1 human colon cancer cell line

The Synergistic Effect of Reduced Graphene Oxide and Proteasome Inhibitor in the Induction of Apoptosis through Oxidative Stress in Breast Cancer Cell Lines

Reduced graphene oxide (rGO) and a proteasome inhibitor (MG-132) are some of the most commonly used compounds in various biomedical applications. However, the mechanisms of rGO- and MG-132-induced cytotoxicity remain unclear. The aim of this study was to investigate the anticancer effect of rGO and MG-132 against ZR-75-1 and MDA-MB-231 breast cancer cell lines. The results demonstrated that rGO, MG-132 or a mix (rGO + MG-132) induced time- and dose-dependent cytotoxicity in ZR-75-1 and MDA-MB-231 cells. Apart from that, we found that treatment with rGO and MG-132 or the mix increased apoptosis, necrosis and induction of caspase-8 and caspase-9 activity in both breast cancer cell lines. Apoptosis and caspase activation were accompanied by changes in the ultrastructure of mitochondria in ZR-75-1 and MDA-MB-231 cells incubated with rGO. Additionally, in the analyzed cells, we observed the induction of oxidative stress, accompanied by increased apoptosis and cell necrosis. In conclusion, oxidative stress induces apoptosis in the tested cells. At the same time, both mitochondrial and receptor apoptosis pathways are activated. These studies provided new information on the molecular mechanisms of apoptosis in the ZR-75-1 and MDA-MB-231 breast cancer cell lines.

Immunoaffinity proteomics for kidney injury biomarkers in male beagle dogs

Drug-induced kidney injury (DIKI) is a cause of drug development failure. Dogs represent a common non-rodent animal model in pre-clinical safety studies; however, biomarker assays for detecting nephrotoxicity in dogs are limited. To identify novel proteins and gain insight into the molecular mechanisms involved in DIKI, we developed an assay to evaluate proteomic changes associated with DIKI in male beagle dogs that received nephrotoxic doses of tobramycin for 10 consecutive days. Label-free quantitative discovery proteomics analysis on representative kidney cortex tissues collected on Day 11 showed that the tobramycin-induced kidney injury led to a significant differential regulation of 94 proteins mostly associated with mechanisms of nephrotoxicity such as oxidative stress and proteasome degradation. For verification of the proteomic results, we developed a multiplex peptide-centric immunoaffinity liquid chromatography tandem mass spectrometry assay (IA LC-MS/MS) to evaluate the association of eight DIKI protein biomarker candidates using kidney cortices collected on Day 11 and urine samples collected on Days -4, 1, 3, 7 and 10. The results showed that most biomarkers evaluated were detected in the kidney cortices and their expression profile in tissue aligned with the label-free data. Cystatin C was the most consistent marker regardless of the magnitude of the renal injury while fatty acid-binding protein-4 (FABP4) and kidney injury molecule-1 (KIM-1) were the most affected biomarkers in response to moderate proximal tubular injury in absence of changes in serum-based concentrations of blood urea nitrogen or creatinine. In the urine, clusterin is considered the most consistent biomarker regardless of the magnitude and time of the renal injury. To our knowledge, this is the most comprehensive multiplex assay for the quantitative analysis of mechanism-based proximal tubular injury biomarkers in dogs.

Hypoxia-responsive covalent organic framework by single NIR laser-triggered for multimodal synergistic therapy of triple-negative breast cancer

In recent years, laser-mediated photodynamic therapy and photothermal therapy have attracted widespread attention due to their minimally invasive, easy to operate characteristics and high specificity. However, the traditional photodynamic or photothermal therapy exist several shortcomings such as the hypoxic microenvironment, intracellular heat shock proteins or complex operation. In this study, covalent organic framework (COF) was used as the drug carrier to equip with the photosensitizer indocyanine green (ICG) and the hypoxia-activating prodrug AQ4N. The hyaluronic acid (HA) was modified on the surface of COF to obtain the HA-COF@ICG/AQ4N drug delivery system. HA-modified COF delivery systems can target tumor cells through recognize CD44 which is overexpressed in the surface of tumor cells membrane. Under the irradiation of single NIR laser, ICG that can excite the nanoplatform simultaneously produces a combined effect of photodynamic and photothermal. At the same time, photodynamic therapy through depleting intracellular oxygen exacerbates the hypoxic state of the tumor microenvironment, which in turn enhances AQ4N reduced to chemotherapeutic drug AQ4, producing a synergistic cascade antitumor effect. The results of our study by tumor cell and tumor spheroids indicated that the hypoxia-activated multi-functional nanoplatform could effectively inhibit the growth and metastasis of triple-negative breast cancer.

Glucose deprivation enhances resistance to paclitaxel via ELAVL2/4-mediated modification of glycolysis in ovarian cancer cells

The dysregulation of glycolysis regardless of oxygen availability is one of the major characteristics of cancer cells. While the drug resistance of ovarian cancer cells has been extensively studied, the molecular mechanism of anticancer drug resistance under low-glucose conditions remains unknown. In this study, we investigated the pathway mediating drug resistance under low-glucose conditions by examining the relationship between embryonic lethal abnormal vision Drosophila homolog-like (ELAVL) protein and glycolysis-related enzymes. Ovarian cancer cells resistant to 2.5 nM paclitaxel were exposed to low-glucose media for 2 weeks, and the expression levels of ELAVL2, ELAVL4, glycolytic enzymes, and drug resistance-related proteins were elevated to levels comparable to those in cells resistant to 100 nM paclitaxel. Gene silencing of ELAVL2/4 using small interfering RNA prevented the upregulation of glycolysis-related enzymes, reduced lactate production, and sensitized 2.5 nM paclitaxel-resistant ovarian cancer cells to anticancer agents under hypoglycemic conditions. Furthermore, pharmacological inhibition of glycolytic enzymes with 2-deoxyglucose, a specific inhibitor of glycolysis, triggered caspase-dependent apoptosis, reduced lactate generation, and blocked the expression of drug resistance-related proteins under low-glucose conditions. These results suggest that the level of ELAVL2/4 is responsible for the development of chemoresistance through activation of the glycolysis pathway under glucose deprivation conditions.

The Pro-Apoptotic Effect of Silica Nanoparticles Depends on Their Size and Dose, as Well as the Type of Glioblastoma Cells

Despite intensive investigations, nanoparticle-induced cellular damage is an important problem that has not been fully elucidated yet. Here, we report that silica nanoparticles (SiNPs) demonstrated anticancer influence on glioblastoma cells by the induction of apoptosis or necrosis. These effects are highly cell type-specific, as well as dependent on the size and dose of applied nanoparticles. Exposure of LN-18 and LBC3 cells to different sizes of SiNPs-7 nm, 5-15 nm, or 10-20 nm-at dosages, ranging from 12.5 to 1000 µg/mL, for 24 and 48 h reduced the viability of these cells. Treatment of LN-18 and LBC3 cells with 7 nm or 10-20 nm SiNPs at doses ≥50 µg/mL caused a strong induction of apoptosis, which is connected with an increase of intracellular reactive oxygen species (ROS) production. The 5-15 nm SiNPs exhibited distinct behavior comparing to silica nanoparticles of other studied sizes. In contrast to LBC3, in LN-18 cells exposed to 5-15 nm SiNPs we did not observe any effect on apoptosis. These nanoparticles exerted only strong necrosis, which was connected with a reduction in ROS generation. This suggests that SiNPs can trigger different cellular/molecular effects, depending on the exposure conditions, the size and dose of nanoparticles, and cell type of glioblastoma.

Silencing of Proteasome 26S Subunit ATPase 2 Regulates Colorectal Cancer Cell Proliferation, Apoptosis, and Migration

OBJECTIVE

Colorectal cancer (CRC) remains a major cause of cancer-related death worldwide. Proteasome 26S subunit ATPase 2 (PSMC2) plays vital roles in regulating cell cycle and transcription and has been confirmed to be a gene potentially associated with some human tumors. However, the expression correlation and molecular mechanism of PSMC2 in CRC are still unclear. This study aimed to investigate the role of PSMC2 in malignant behaviors in CRC.

METHODS

The high protein levels of PSMC2 in CRC samples were identified by tissue microarray analysis. Lentivirus was used to silence PSMC2 in HCT116 and RKO cells; MTT and colony formation assay were performed to determine cell proliferation. Wound healing and Transwell assay were used to detect cell migration and invasion. Flow cytometry assay was applied to detect cell cycle and apoptosis.

RESULT

The results showed that, among the 96 CRC patients, the expression of PSMC2 was a positive correlation with the clinicopathological features of the patients with CRC. Furthermore, the low PSMC2 expression group showed a higher survival rate than the high PSMC2 expression group. The expression levels of PSMC2 in cancer tissue were dramatically upregulated compared with adjacent normal tissues. In vitro, shPSMC2 was designed to inhibit the expression of PSMC2 in CRC cells. Compared with shCtrl, silencing of PSMC2 significantly suppressed cell proliferation, decreased single cell colony formation, enhanced apoptosis, and accelerated G2 phase and/or S phase arrest.

CONCLUSION

Survival analysis indicated that high expression of PSMC2 in the CRC samples was associated with poorer survival rate than low expression of PSMC2, while the anti-tumor effect of PSMC2 silencing was also confirmed at the cellular level in vitro. Our results suggested that PSMC2 potentially worked as a regulator for CRC, and the silencing of PSMC2 may be a therapeutic strategy for CRC.

The evaluation of the anti-cancer activity of ixazomib on Caco2 colon solid tumor cells, comparison with bortezomib

Proteasome inhibition has recently emerged as a clinically effective anticancer therapeutic approach. The first proteasome inhibitor, bortezomib (Velcade, PS-341), and new proteasome inhibitors including ixazomib have become more important in the development of targeted cancer therapies. Under physiological conditions, MLN9708 (ixazomib citrate), the stable citrate ester drug substance, hydrolyzes rapidly to MLN2238 (ixazomib), the biologically active boronic acid. It is a second-generation proteasome inhibitor, similar to the well-known proteasome inhibitor bortezomib, which is currently being investigated in phase 3 trials as a treatment for multiple Myeloma. Despite the proven efficacy of these drugs in hematologic malignancies, clinical activity is limited to solid tumors such as colon adenocarcinoma. This study is the first to investigate and compare the antiproliferative and apoptotic effects of MLN2238 and bortezomib on human colon adenocarcinoma Caco2 cells. The antiproliferative effects of MLN2238 and bortezomib were determined using WST-1; apoptotic effects of this drug were determined by caspase-3 and a mitochondrial membrane potential (JC-1) activity assay. Expression levels associated with proteasome inhibition and apoptosis of NF-κB and c-myc mRNA were evaluated by RT-PCR. At 24 and 48 h, MLN2238 showed significant time- and concentration-dependent antiproliferative and apoptotic effects on Caco2 cells. Depending on increasing mitochondrial depolarization and caspase-3 activation, MLN2238 induced apoptosis at level similar to that of bortezomib. In addition, MLN2238 downregulated NF-κB and c-myc mRNA expression levels. For the first time, MLN2238 was shown to induce antiproliferative and apoptotic effects on human colon adenocarcinoma cells that are comparable with those of bortezomib; these in vitro data in Caco2 cells support the development of MLN2238 for colon cancer.

The Effects of Silica Nanoparticles on Apoptosis and Autophagy of Glioblastoma Cell Lines

Silica nanoparticles (SiNPs) are one of the most commonly used nanomaterials in various medical applications. However, possible mechanisms of the toxicity caused by SiNPs remain unclear. The study presented here provides novel information on molecular and cellular effects of SiNPs in glioblastoma LBC3 and LN-18 cells. It has been demonstrated that SiNPs of 7 nm, 5–15 nm and 10–20 nm induce time- and dose-dependent cytotoxicity in LBC3 and LN-18 cell lines. In contrast to glioblastoma cells, we observed only weak reduction in viability of normal skin fibroblasts treated with SiNPs. Furthermore, in LBC3 cells treated with 5–15 nm SiNPs we noticed induction of apoptosis and necrosis, while in LN-18 cells only necrosis. The 5–15 nm SiNPs were also found to cause oxidative stress, a loss in mitochondrial membrane potential, and changes in the ultrastructure of the mitochondria in LBC3 cells. Quantitative real-time PCR results showed that in LBC3 cells the mRNA levels of pro-apoptotic genes Bim, Bax, Puma, and Noxa were significantly upregulated. An increase in activity of caspase-9 in these cells was also observed. Moreover, the activation of SiNP-induced autophagy was demonstrated in LBC3 cells as shown by an increase in LC3-II/LC3-I ratio, the upregulation of Atg5 gene and an increase in AVOs-positive cells. In conclusion, this research provides novel information concerning molecular mechanisms of apoptosis and autophagy in LBC3 cells.

Sclareol inhibits cell proliferation and sensitizes cells to the antiproliferative effect of bortezomib via upregulating the tumor suppressor caveolin-1 in cervical cancer cells

The anticancer effect of sclareol has long been reported, however, the exact mechanisms underlying the antitumorigenic effect of sclareol in cervical carcinoma remain to be fully elucidated. The present study analyzed cell proliferation and cell apoptosis by MTT and FITC-Annexin V assays. The protein levels of caveolin-1 (Cav-1) and copper-zinc superoxide dismutase (SOD)1 were determined by western blotting, and the interaction of Cav1 and HSC70 was investigated by co-immunoprecipitation experiments. The present study found that sclareol inhibited cell proliferation and induced apoptosis in HeLa cells. Two cancer-associated proteins, Cav1 and SOD1 were identified as potential targets of sclareol in HeLa cells. The expression of Cav1 increased when the cells were treated with sclareol, and the protein level of SOD1 was negatively correlated with Cav1. The overexpression of Cav1 enhanced the sensitivity of the HeLa cells to sclareol treatment and downregulated the protein level of SOD1, which exhibited potential associations between Cav1 and SOD1. In addition, sclareol significantly sensitized several cancer cells to the anticancer effect of bortezomib by targeting Cav1 and SOD1. Taken together, the results of the present study demonstrated that sclareol inhibited tumor cell growth through the upregulation of Cav1, and provides a potential therapeutic target for human cancer.

Leucovorin Enhances the Anti-cancer Effect of Bortezomib in Colorectal Cancer Cells

Colorectal cancer is a major cancer type worldwide. 5-fluorouracil, often given with leucovorin, is the most commonly used drug in colorectal cancer chemotherapy, yet development of drug resistance to 5-fluorouracil in colorectal cancer cells is the primary cause of chemotherapy failure. Most patients receiving intravenous 5-fluorouracil develop side effects. Leucovorin, due to its vitamin-like profile, has few side-effects. Drug repurposing is the application of approved drugs to treat new indications. In this study, we performed a novel drug-repurposing screening to identify Food and Drug Administration-approved chemotherapeutic compounds possessing synergistic activity with leucovorin against colorectal cancer cells. We found that the combination of bortezomib and leucovorin enhanced caspase activation and increased apoptosis in colorectal cancer cells better than either agent alone. Further, the synergistic induction of apoptosis and inhibition of tumor growth were also observed in mouse colorectal cancer xenografts. These data support leucovorin enhances the anti-cancer effect of bortezomib and present this novel combinatorial treatment against colorectal cancer.

Hypoxia potentiates the cytotoxic effect of piperlongumine in pheochromocytoma models

Hypoxia is a common feature of solid tumors that activates a plethora of pathways, resulting in proliferation and resistance of cancer cells to radio- and chemotherapy. Pheochromocytomas/paragangliomas (PHEOs/PGLs) with mutations in the gene coding for the subunit B of succinate dehydrogenase (SDHB) are the most aggressive forms of the disease, which is partially due to their pseudohypoxic character, metabolic abnormalities, and elevated reactive oxygen species (ROS) levels. We investigated the effect of piperlongumine (PL), a natural product with cytotoxic properties restricted to cancer cells by significantly increasing intracellular ROS levels, on PHEO cells. Here we report for the first time that PL mediates PHEO cell death by activating both apoptosis and necroptosis in vitro and in vivo. This effect is magnified in hypoxic conditions, making PL a promising potential candidate for use as a therapeutic option for patients with PHEO/PGL, including those with SDHB mutations.

Low glucose dependent decrease of apoptosis and induction of autophagy in breast cancer MCF-7 cells

Cancer cells have developed a number of adaptation mechanisms involving the signal activation of the transduction pathways, which promotes the progression and metastasis. Our results showed that the percentage of apoptotic MCF-7 cells incubated in the low glucose medium for 48 h was lower in comparison to those cultured in the high glucose medium, despite the high expression of the proapoptotic transcription factor-CHOP. Furthermore, the MCF-7 cells incubated in the low glucose medium for 48 h showed a higher expression of NF-κB p100/p52 subunits compared to cells incubated in the high glucose medium. Moreover, our findings demonstrated that the shortage of glucose strongly induces autophagy in MCF-7 cells. The activation of this process is not associated with the changes in the expression of mTOR kinase. We suggest, that the antiapoptotic chaperone ORP150 induction, transcription factor NF-κB2 activation, and increased autophagy constitute mechanisms protecting the MCF-7 cells against apoptosis.

The Role of Cathelicidin LL-37 in Cancer Development

LL-37 is a C-terminal peptide proteolytically released from 18 kDa human cathelicidin protein (hCAP18). Chronic infections, inflammation, tissue injury and tissue regeneration are all linked with neoplastic growth, and involve LL-37 antibacterial and immunomodulatory functions. Such a link points to the possible involvement of LL-37 peptide in carcinogenesis. An increasing amount of evidence suggests that LL-37 can have two different and contradictory effects--promotion or inhibition of tumor growth. The mechanisms are tissue-specific, complex, and depend mostly on the ability of LL-37 to act as a ligand for different membrane receptors whose expression varies on different cancer cells. Overexpression of LL-37 was found to promote development and progression of ovarian, lung and breast cancers, and to suppress tumorigenesis in colon and gastric cancer. This review explores and summarizes the current views on how LL-37 contributes to immunity, pathophysiology and cell signaling involved in malignant tumor growth.