Background/Aims: Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and is a leading cause of cancer-related death worldwide. Luteolin, a flavonoid from traditional Chinese medicine, shows anti-cancer activity in many cancer cells, including HCC. However, the mechanism underlying the action of luteolin in HCC, especially its role in regulating cell autophagy, remains unclear. In the present study, we investigated the role of luteolin in regulating cell autophagy and the role of autophagy in luteolin-induced apoptosis. Methods: The 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay (MTT) was used to investigate cell viability. Flow cytometry analysis was used to detect the cell cycle and cell apoptosis. Hoechst 33342 staining was used to detect cell apoptosis. Transmission electron microscopy was used to investigate autophagy. qRT-PCR and western blotting were used to detect apoptosis- and autophagy-related mRNAs and proteins. Results: Luteolin reduced the viability of SMMC-7721 cells in a time and dose-dependent manner, and induced significant G0/G1-phase arrest. In addition, the results of flow cytometry analysis and Hoechst 33342 staining showed that luteolin treatment increased the number of apoptotic cells obviously, and the results of qRT-PCR and western blotting showed that luteolin treatment increased caspase 8 and decreased bcl-2 at the mRNA and protein levels. Furthermore, luteolin increased the number of intracellular autophagosomes, promoted LC3B-I conversion to LC3B-II, and increased Beclin 1 expression. Finally, co-treatment with the autophagy inhibitor chloroquine weakened the effects of luteolin on cell apoptosis. Conclusion: Luteolin induced apoptosis in human liver cancer SMMC-7721 cells, partially via autophagy. Thus, luteolin could be used as a regulator of autophagy in HCC treatment.

We studied the apoptosis-inducing properties of the antimicrobial peptide cecropin of Musca domestica in human hepatocellular carcinoma cell line BEL-7402 and its underlying mechanism. Proliferation inhibition of the human hepatocellular carcinoma BEL-7402 cells and the human normal liver cells were determined by the MTT assay, and the cell viability was determined by trypan blue dye exclusion assay. The apoptotic tumor cells treated with cecropin were examined by transmission electron microscopy and terminal-deoxynucleotidyl transferase mediated nick end labeling. The apoptosis rate was measured by flow cytometry (FCM) with PI/Annexin-V double staining. Western blot analysis and RT-PCR were used to determine the expression levels of proteins involved in apoptosis, such as Fas, Fas-L, caspase-8, and caspase-3. The experimental results showed that Musca domestica cecropin inhibited the proliferation of human hepatocellular carcinoma BEL-7402 cells in dosedependent and time-dependent manners, without affecting the proliferation of normal liver cells. FCM showed that the cell apoptosis rates were 5.1+/-0.11%, 8.1+/-0.04%, and 10.9+/-0.15% after the treating with 100 mM cecropin for 24, 48, and 72 h, respectively. The rates of apoptosis were 5.4+/-0.14% and 8.0+/-0.13% after the treating with 25 and 50 microM cecropin for 72 h, respectively. Western blot analysis and RT-PCR showed that the apoptosisrelated molecules including Fas, Fas-L, caspase-8 and caspase-3 were activated. This study showed that the antimicrobial peptide cecropin-inducing apoptosis in human hepatocellular carcinoma BEL-7402 cells, which might be associated with upregulation of Fas, Fas-L, and caspase-8 and caspase-3 and triggering extrinsic apoptotic pathway.

Lysozyme is an abundant, cationic antimicrobial protein that plays an important role in host defense. It targets the beta (1-4) glycosidic bond between N-acetylglucosamine and N-acetylmuramic residues that make up peptidoglycan, making lysozyme highly active against Gram-positive bacteria. However, lysozyme alone is inactive against Gram-negative bacteria because it cannot reach the peptidoglycan layer. Cecropins are cationic molecules with a wide range of antimicrobial activities. The main target for these peptides is the cytoplasmic membrane. We resume that cecopin may disrupt the outer membrane, giving the enzyme access to the peptidoglycan in cell wall. So in the present study, novel hybrid protein combining Musca domestica cecropin (Mdc) with human lysozyme (Hly) was designed. The DNA sequence encoding recombination fusion protein Mdc-hly was cloned into the pET-32a vector for protein expression in Escherichia coli strain BL21 (DE3). The protein was expressed as a His-tagged fusion protein, and the Mdc-hly was released from the fusion by enterokinase cleavage and separated from the carrier thioredoxin. Antimicrobial activity assays showed that the recombinant fusion protein Mdc-hly has improved in vitro antimicrobial activity and action spectrum compared to Mdc and hly. Mdc-hly may have important potential application as a future safely administered human drug and food additive.

The chloride channel-3 (ClC-3) protein is known to be a component of Cl− channels involved in cell volume regulation or acidification of intracellular vesicles. Here, we report that ClC-3 was highly expressed in the cytoplasm of metastatic carcinomatous cells and accelerated cell migration in vitro and tumor metastasis in vivo. High-grade expression of cytoplasmic ClC-3 predicted poor survival in cancer patients. We found that independent of its volume-activated Cl− channel properties, ClC-3 was able to promote cell membrane ruffling, required for tumor metastasis. ClC-3 mediated membrane ruffling by regulating keratin 18 phosphorylation to control β1 Integrin recycling. Therefore, cytoplasmic ClC-3 plays an active and key role in tumor metastasis and may be a valuable prognostic biomarker and a therapeutic target to prevent tumor spread.

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