Antimicrobial peptide GW-H1-induced apoptosis of human gastric cancer AGS cell line is enhanced by suppression of autophagy

Fatty acid modification of casein bioactive peptides nano-assemblies, synthesis, characterization and anticarcinogenic effect

In this study, the nano-assemblies of bovine casein hydrolyzed peptides (HP) modified by fatty acids with various alkyl chain lengths (C8, C10, C12 and C14) were synthesized. The physicochemical properties of HP-C8-HP-C14 nano-assemblies were characterized using spectra, laser particle size analyzer, contact angle meter, scanning electron microscope (SEM) and cryo-transmission electron microscope (Cryo-TEM). HP-C8 and HP-C10 self-assembled into a hollow cube cage with an average size of ~500 nm, and the assembly of HP-C12 showed a flower-shaped morphology with more dispersed behavior, and droplet size was observed as ~20 nm. The in vitro cytotoxicity against human breast cancer cells MCF-7 was tested using CCK-8 assay and flow cytometry analysis. HP-C12 showed the highest cytotoxicity for MCF-7 cells with an inhibition rate of 66.03 % ± 0.35 % with an IC50 value of 7.4 μM among HP-Cn. HP-C8, HP-C10 and HP-C12 significantly affected on the migration, invasion and apoptosis of MCF-7 cells. The apoptosis mechanism may depend on the upregulation of anti-apoptotic protein Bcl-2 as well as pro-apoptotic proteins Bax and caspase-8. The dead MCF-7 cells were analyzed with UHPLC-MS/MS using untargeted metabolomics, revealing key metabolic pathways.

Application Value of Antimicrobial Peptides in Gastrointestinal Tumors

Gastrointestinal cancer is a common clinical malignant tumor disease that seriously endangers human health and lacks effective treatment methods. As part of the innate immune defense of many organisms, antimicrobial peptides not only have broad-spectrum antibacterial activity but also can specifically kill tumor cells. The positive charge of antimicrobial peptides under neutral conditions determines their high selectivity to tumor cells. In addition, antimicrobial peptides also have unique anticancer mechanisms, such as inducing apoptosis, autophagy, cell cycle arrest, membrane destruction, and inhibition of metastasis, which highlights the low drug resistance and high specificity of antimicrobial peptides. In this review, we summarize the related studies on antimicrobial peptides in the treatment of digestive tract tumors, mainly oral cancer, esophageal cancer, gastric cancer, liver cancer, pancreatic cancer, and colorectal cancer. This paper describes the therapeutic advantages of antimicrobial peptides due to their unique anticancer mechanisms. The length, net charge, and secondary structure of antimicrobial peptides can be modified by design or modification to further enhance their anticancer effects. In summary, as an emerging cancer treatment drug, antimicrobial peptides need to be further studied to realize their application in gastrointestinal cancer diseases.

Antibacterial and Anticancer Activities of Pleurocidin-Amide, a Potent Marine Antimicrobial Peptide Derived from Winter Flounder, Pleuronectes americanus

The extensive use of conventional antibiotics has led to the growing emergence of many resistant strains of pathogenic bacteria. Evidence suggests that cationic antimicrobial peptides (AMPs) have the greatest potential to serve as traditional antibiotic substitutes. Recent studies have also reported that certain AMPs have selective toxicity toward various types of cancer cells. The electrostatic attraction between the negatively charged membrane components and AMPs is believed to play a crucial role in the disruption of bacterial and cancer cell membranes. In the current study, we used a potent AMP called Pleurocidin (Ple) derived from winter flounder Pleuronectes americanus and its C-terminal-amidated derivative Pleurocidin-amide (Ple-a), and evaluated their antibacterial and anticancer activities. Our results indicated that both Ple and Ple-a exhibited significant antibacterial activity against a broad spectrum of Gram-positive and Gram-negative bacteria, especially marine pathogens, with MIC values ranging from 0.25 to 32 μg/mL. These peptides are also potent against several multidrug-resistant (MDR) bacterial strains, with MIC values ranging from 2 to 256 μg/mL. When used in combination with certain antibiotics, they exhibited a synergistic effect against MDR E. coli. Ple and Ple-a also showed notable cytotoxicity toward various cancer cell lines, with IC₅₀ values ranging from 11 to 340 μM, while normal mouse fibroblast 3T3 cells were less susceptible to these peptides. Ple-a was then selected to study its anticancer mechanism toward A549 human lung adenocarcinoma cells. Western blot analysis and confocal microscopy showed that Ple-a could inhibit autophagy of A549 cells, and induce apoptosis 48 h after treatment. Our findings provided support for the future application of Ple-a as potential therapeutic agent for bacterial infections and cancer treatment.

Antimicrobial peptides as potential therapeutics for breast cancer

Breast cancer is the most common and deadliest cancer in women worldwide. Although notable advances have been achieved in the treatment of breast cancer, the overall survival rate of metastatic breast cancer patients is still considerably low due to the development of resistance to breast cancer chemotherapeutic agents and the non-optimal specificity of the current generation of cancer medications. Hence, there is a growing interest in the search for alternative therapeutics with novel anticancer mechanisms. Recently, antimicrobial peptides (AMPs) have gained much attention due to their cost-effectiveness, high specificity of action, and robust efficacy. However, there are no clinical data available about their efficacy. This warrants the increasing need for clinical trials to be conducted to assess the efficacy of this new class of drugs. Here, we will focus on the recent progress in the use of AMPs for breast cancer therapy and will highlight their modes of action. Finally, we will discuss the combination of AMP-based therapeutics with other breast cancer therapy strategies, including nanotherapy and chemotherapy, which may provide a potential avenue for overcoming drug resistance.

Effect of Hydrophobicity on the Anticancer Activity of Fatty-Acyl-Conjugated CM4 in Breast Cancer Cells

Antimicrobial peptides (AMPs) are important anticancer resources, and exploring AMP conjugates as highly effective and selective anticancer agents would represent new progress in cancer treatment. In this study, we synthesized C4-C16 fatty-acyl-conjugated AMP CM4 and investigated its physiochemical properties and cytotoxicity activity in breast cancer cells. Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and reversed-phase high-performance liquid chromatography (RP-HPLC) showed that long-chain fatty acyl (≥C12) conjugation prevented N-acyl-CM4 from trypsin hydrolysis. RP-HPLC and circular dichroism (CD) spectra showed that the hydrophobicity and helical content of N-acyl-CM4 increased with the acyl length. The acyl chain length was positively related to the cytotoxicity of C8-C16 conjugates, and C12-C16 fatty acyl conjugates exhibited significant cytotoxicity against MX-1, MCF-7, and MDA-MB-231 cells, with IC₅₀ values <8 μM. Flow cytometry and confocal laser scanning microscopy results showed that N-acylated conjugation significantly increased the membrane affinity in breast cancer cells, and C12-C16 acyl conjugates were capable of translocating to the intracellular space, thereby targeting mitochondria and inducing apoptosis. N-acyl-CM4 showed low cytotoxicity against normal mammalian cells and erythrocytes, especially ≤C12 fatty acyl conjugates, exhibiting selective cytotoxicity to breast cancer cells. The current work indicated that increasing hydrophobicity by attaching long fatty acyl (≥C12) to AMPs may be an effective method to improve the anticancer activity, together with selectivity and resistance to trypsin hydrolysis. This finding provides a good strategy to develop AMPs as effective anticancer agents in the future.

Germacrone Induces Apoptosis as Well as Protective Autophagy in Human Prostate Cancer Cells

Background

Germacrone, a natural product isolated from the traditional Chinese medicine Rhizoma Curcuma, has been reported to exhibit antitumor activities in vitro. To further understand the antitumor mechanism of germacrone, we investigated the growth inhibitory effect of germacrone on the human prostate cancer cell lines PC-3 (androgen independent) and 22RV1 (androgen dependent).

Materials and Methods

Prostate cancer cells were cultured with different concentrations of germacrone, and cell viability was measured by MTT assay. The levels of proteins were measured by Western blotting. Cell apoptosis was assessed by flow cytometry. Images of autophagy-related protein staining were captured by fluorescence microscopy. Autophagic flux was assessed by detecting the LC3B-II level.

Results

Our results indicated that germacrone treatment significantly inhibited cell proliferation by inducing apoptosis in a dose-dependent manner, with IC50 values of 259 μM for PC-3 cells and 396.9 μM for 22RV1 cells. Germacrone-treated cells also exhibited induction of autophagy, as evidenced by elevated LC3B-II protein expression levels and punctuate patterns. Additionally, an autophagy inhibitor enhanced the growth inhibitory effect of germacrone. Moreover, the phosphorylation of Akt and mTOR was inhibited in germacrone-treated prostate cancer cells.

Conclusion

Germacrone induced apoptosis and autophagy in prostate cancer cells by inhibiting the Akt/mTOR signaling pathway. Germacrone treatment also led to the activation of protective autophagy. These findings suggest that germacrone may potentially contribute to the development of a new therapeutic agent for prostate cancer treatment.

In vivo and in vitro studies using Clonorchis sinensis adult-derived total protein (CsTP) on cellular function and inflammatory effect in mouse and cell model

Clonorchis sinensis (C. sinensis) can induce a food-borne parasitic disease (clonorchiasis). Numerous studies have analyzed functional proteins, immunologic factors, pro-inflammatory cytokines, and cell signaling transduction that promote the development of clonorchiasis. In a previous study, it was shown that C. sinensis adult-derived total protein (CsTP) might be involved in the pathogenesis and development of liver fibrosis via bringing about Th2 immune response. In the present study, further investigation of CsTP on cellular function and inflammatory effect in vitro and in vivo has been elicited. CsTP induced inflammation and autophagy as evidenced by upregulation of TNF-α, IFN-γ, and autophagic markers LC3B and P62. Exposed to CsTP upregulated the antiapoptotic gene Bcl-2 expression, diminished the apoptosis induced by H₂O₂, but promoted the proliferation and migration of LX-2 cells in proper concentration range. Additionally, the protein levels of p-AKT and p-mTOR were repressed in response to CsTP, suggesting a correlation of blocking the activation of mTOR/AKT signaling pathway. These results revealed that CsTP might exacerbate hepatic pathological changes by regulating cell proliferation, apoptosis, autophagy, and inflammation in the liver and LX-2 cells. Some effects might be partially involved in the mTOR and AKT pathways.

Distribution of positively charged amino acid residues in antimicrobial peptide epinecidin-1 is crucial for in vitro glioblastoma cytotoxicity and its underlying mechanisms

Epinecidin-1 (epi) was identified from orange-spotted grouper (Epinephelus coioides) and exhibits diverse biological activities. The aims of this study were to investigate how the distribution of positively charged amino acid residues affects epi-mediated cytotoxicity and to examine the molecular mechanism underlying epi-induced cytotoxicity in U87MG human glioblastoma cells. MTS/PMS and trypan blue exclusion assay were used to measure cell viability. Necrotic cell death was confirmed by detecting cyclophilin A release and propidium iodide incorporation. DNA damage was evaluated by measuring phosphorylated H2AX. Intracellular reactive oxygen species (ROS) were analyzed by flow cytometry using dihydroergotamine. Mitochondrial membrane potential was detected by flow cytometry using tetramethylrhodamine, ethyl ester. Overall, we found that epi caused cytotoxicity in U87MG cells by inducing DNA damage and necrosis through mitochondrial hyperpolarization and subsequent ROS production. The proper folding of epi into an α-helical structure was essential for epi-mediated anti-glioblastoma effects. In addition, NFκB signaling was activated in U87MG cells after exposure to epi. Suppression of NFκB further enhanced epi-induced cytotoxicity, ROS generation and DNA damage, indicating that NFκB may play a protective role in epi-induced cytotoxicity. Our findings may be useful for the design and improvement of antimicrobial peptides with anti-cancer activity.

The Ameliorating Effect of Plasma Protein from Tachypleus tridentatus on Cyclophosphamide-Induced Acute Kidney Injury in Mice

In the study, the protective effect of plasma protein from Tachypleus tridentatus (PPTT) on acute kidney injury (AKI) and the related molecular mechanisms were first investigated by Western blotting analyses, TdT-mediated dUTP Nick-End Labeling (TUNEL) assay, and immunohistochemistry. It was found that PPTT had an obviously inhibitory effect on Reactive oxygen species (ROS) in cyclophosphamide (CTX)-exposed mice. Furthermore, results demonstrated that the renal cell death mode is due to inducing apoptosis and autophagy inhibited by dose-dependent PPTT in mice treated with CTX by decreasing the protein expression of bax, beclin-1, and LC3 and increasing the expression of bcl-2. Moreover, the p38 MAPK and PI3K/Akt signaling pathways were observed to take part in the PPTT-induced renal cell growth effect by enhancing the upregulation of the expression of Akt and p-Akt as well as the downregulation of the expression of p38 and p-p38, which indicated a PPTT ameliorating effect on AKI CTX-induced in mice through p38 MAPK and PI3K/Akt signaling pathways. Briefly, this article preliminarily studies the mechanism of the PPTT ameliorating effect on AKI CTX-induced in mice, which helps to provide a reference for PPTT clinical application in AKI therapy.

Antimicrobial Peptide TP4 Induces ROS-Mediated Necrosis by Triggering Mitochondrial Dysfunction in Wild-Type and Mutant p53 Glioblastoma Cells

Antimicrobial peptide tilapia piscidin 4 (TP4) from Oreochromis niloticus exhibits potent bactericidal and anti-tumorigenic effects. In a variety of cancers, the mutation status of p53 is a decisive factor for therapeutic sensitivity. Therefore, we investigated the impact of p53 status on TP4-induced cytotoxicity in glioblastoma cell lines and the molecular mechanisms that govern cytotoxic effects. Both U87MG (wild-type/WT p53) and U251 (mutant p53) glioblastoma cell lines were sensitive to TP4-induced cytotoxicity. The necrosis inhibitors Necrostatin-1 and GSK’872 attenuated TP4-induced cytotoxicity, and TP4 treatment induced the release of cyclophilin A, a biomarker of necrosis. Moreover, TP4 induced mitochondrial hyperpolarization and dysfunction, which preceded the elevation of intracellular reactive oxygen species, DNA damage, and necrotic cell death in both U87MG and U251 glioblastoma cells. p38 was also activated by TP4, but did not contribute to cytotoxicity. SB202190, a specific p38 inhibitor, enhanced TP4-induced oxidative stress, mitochondrial dysfunction, and cytotoxicity, suggesting a protective role of p38. Furthermore, TP4-induced cytotoxicity, oxidative stress, phosphorylation of p38, and DNA damage were all attenuated by the mitochondrial-targeted reactive oxygen species (ROS) scavenger MitoTEMPO, or the reactive oxygen species scavenger N-acetyl-L-cysteine. Based on these data, we conclude that TP4 induces necrosis in both WT and mutant p53 glioblastoma cells through a mitochondrial ROS-dependent pathway.

Autophagy flux inhibition augments gastric cancer resistance to the anti-human epidermal growth factor receptor 2 antibody trastuzumab

The autophagy involved in the occurrence, development and prognosis of human epidermal growth factor receptor 2 (HER2) gene-amplified cancer also controls the resistance of this type of cancer to the monoclonal antibody, trastuzumab (Tzb). In the present study, Tzb resistance was established in HER2-positive NCI-N87 cell lines (Tzb-refractory cells). The cell viability, clonogenic assay, ratios of light chain 3 II/I, sequestosome 1 expression, and the phosphorylation of protein kinase B (Akt) and mechanistic target of rapamycin (mTOR) were investigated in the parental and Tzb-refractory cells. The viability of parental NCI-N87 and Tzb-refractory cells with an autophagy inhibitor or inducer was also examined. The results of the present study indicated that autophagic flux may have an important function in the resistance of HER2-positive human gastric cancer NCI-N87 cells to Tzb. Tzb resistance in NCI-N87 cells prevents cell apoptosis via autophagic flux inhibition. Tzb may activate the Akt/mTOR pathway to inhibit autophagic flux in gastric cancer cell lines. Everolimus, an mTOR inhibitor, may inhibit cell viability, indicating that the mTOR pathway may serve a function in HER2-positive gastric cancer and that the resistance of HER2-positive gastric cancer to Tzb may, at least partially, be due to activation of the mTOR pathway.

A synthetic cationic antimicrobial peptide inhibits inflammatory response and the NLRP3 inflammasome by neutralizing LPS and ATP

Antimicrobial peptides (AMPs) are one of the most important defense mechanisms against bacterial infections in insects, plants, non-mammalian vertebrates, and mammals. In the present study, a class of synthetic AMPs was evaluated for anti-inflammatory activity. One cationic AMP, GW-A2, demonstrated the ability to inhibit the expression levels of nitric oxide (NO), inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-activated macrophages. GW-A2 reduced LPS-induced increases in the phosphorylation of mitogen-activated protein kinase and protein kinase C-α/δ and the activation of NF-κB. GW-A2 also inhibited NLRP3 inflammasome activation induced by LPS and ATP. Furthermore, in the mice injected with LPS, GW-A2 reduced (1) the concentration of IL-1β, IL-6 and TNF-α in the serum; (2) the concentration of TNF-α in the peritoneal lavage; (3) the expression levels of iNOS, COX-2 and NLRP3 in the liver and lung; (4) the infiltration of polymorphonuclear neutrophils in the liver and lung. The underlying mechanisms for the anti-inflammatory activity of GW-A2 were found to be partially due to LPS and ATP neutralization. These results provide insights into how GW-A2 inhibits inflammation and the NLRP3 inflammasome and provide a foundation for the design of rational therapeutics for inflammation-related diseases.

Silencing of AQP3 induces apoptosis of gastric cancer cells via downregulation of glycerol intake and downstream inhibition of lipogenesis and autophagy

Gastric cancer (GC) has a poor prognosis and is a leading cause of cancer-related death. Optimal therapeutic targets have not been identified. AQP3 is capable of transporting glycerol across the cytomembrane. Previous studies have shown that AQP3 is involved in proliferation, invasion and migration by regulating glycerol and lipid metabolism in diverse cancer cell types. However, the potential roles of glycerol and lipid metabolism in AQP3-related cell apoptosis in GC remain unclear. In this study, we observed that AQP3 expression was upregulated in tumor tissues, and positively correlated with tumor size, lymph node metastasis and glycerol concentration in human GC samples. Silencing of AQP3 resulted in decreased glycerol intake and impaired lipid synthesis, which contributed to increased cell apoptosis. Furthermore, inhibition of autophagy induced by AQP3 knockdown promoted cell apoptosis. Administration of either glycerol or rapamycin restored cell viability, and overexpression of AQP3 increased cell viability by upregulating cellular glycerol metabolism and autophagy. Our study demonstrates that the increase in cell apoptosis of AQP3-deficient GC cells is a consequence of reduced glycerol uptake and lipogenesis and is associated with autophagy inhibition induced by AQP3 deficiency.

Bovine lactoferricin P13 triggers ROS-mediated caspase-dependent apoptosis in SMMC7721 cells

Bovine lactoferricin P13 (LfcinB-P13) is a peptide derived from LfcinB. In the present study, the effect of LfcinB-P13 on the human liver cancer cell line SMMC7721 was investigated in vitro and in vivo. The results of the present study indicate that LfcinB-P13 significantly decreased SMMC7721 cell viability in vitro (P=0.032 vs. untreated cells), while exhibiting low cytotoxicity in the wild-type liver cell line L02. In addition, the rate of apoptosis in SMMC7721 cells was significantly increased following treatment with 40 and 60 µg/ml LfcinB-P13 (P=0.0053 vs. the control group), which was associated with an increase in the level of reactive oxygen species (ROS) and the activation of caspase-3 and -9. Furthermore, ROS chelation led to the suppression of LfcinB-P13-mediated caspase-3 and -9 activation in SMMC7721 cells. LfcinB-P13 was demonstrated to markedly inhibit tumor growth in an SMMC7721-xenograft nude mouse model. The results of the present study indicate that LfcinB-P13 is a novel candidate therapeutic agent for the treatment of liver cancer.

AKT/mTOR signaling pathway is involved in salvianolic acid B-induced autophagy and apoptosis in hepatocellular carcinoma cells

Chinese medicines are emerging as an attractive new generation of anticancer drugs. Here, we explored the impact of salvianolic acid B (Sal B), the major water-soluble compounds of Danshen, on apoptosis and autophagy of human hepatocellular carcinoma cells (HCC). We also investigated the related molecular mechanisms. We found that Sal B exhibits potent ability to inhibit HCC cells viability in a concentration-dependent manner, and to induce apoptosis via the mitochondrial apoptosis pathway. Additionally, Sal B could also induce autophagy. Furthermore, pretreatment with the autophagy inhibitor chloroquine or 3-methyladenine showed the potential in attenuating the apoptosis rate induced by Sal B. Mechanistically, Sal B treatment inhibited the AKT/mTOR signaling cascade in vitro. Overexpression of AKT abolished the effects of Sal B on HCC cells, suggesting a critical role of the AKT/mTOR signaling pathway in Sal B-induced biological effects. Our results indicated that the mitochondrial pathway was involved in Sal B-induced apoptosis of HCC cells. Moreover, the AKT/mTOR signaling pathway was involved in Sal B-induced autophagy, which promoted apoptosis. This study may provide a promising strategy for using Sal B as a chemotherapeutic agent for patients with HCC.

Dihydrotanshinone I induced apoptosis and autophagy through caspase dependent pathway in colon cancer

BACKGROUND

Dihydrotanshinone I (DHTS) was previously reported to exhibit the most potent anti-cancer activity among several tanshinones in colon cancer cells. Its cytotoxic action was reactive oxygen species (ROS) dependent but p53 independent.

PURPOSE

To further study the anti-cancer activity of DHTS and its molecular mechanisms of action in colon cancer both in vitro and in vivo.

METHODS

Caspase activity was detected by fluorescence assay. Apoptosis was detected by flow cytometry and TUNEL assay. Protein levels were analyzed by western blotting. Knockdown of target gene was achieved by siRNA transfection. Formation of LC3B puncta and activation of caspase-3 were detected by confocal fluorescence microscope. In vivo anti-colon cancer activity of DHTS was observed in xenograft tumors in NOD/SCID mice.

RESULTS

Anti-colon cancer activity of DHTS by inducing apoptosis and autophagy was observed both in vitro and in vivo. Mitochondria mediated caspase dependent pathway was essential in DHTS-induced cytotoxicity. The apoptosis induced by DHTS was suppressed by knockdown of apoptosis inducing factor (AIF), inhibition of caspase-3/9 but was increased after knockdown of caspase-2. Meantime, knockdown of caspase-2, pretreatment with Z-VAD-fmk or NAC (N-Acety-L-Cysteine) efficiently inhibited the autophagy induced by DHTS. A crosstalk between cytochrome c and AIF was also reported.

CONCLUSION

DHTS-induced caspase and ROS dependent apoptosis and autophagy were mediated by mitochondria in colon cancer. DHTS could be a promising leading compound for the development of anti-tumor agent or be developed as an adjuvant drug for colon cancer therapy.