Hernandonine-Mediated Autophagic Cell Death in Hepatocellular Carcinoma: Interplay of p53 and YAP Signaling Pathways.

Hepatocellular carcinoma (HCC), the primary form of liver cancer, is the third leading cause of cancer-related death globally. Hernandonine is a natural alkaloid derived from Hernandia nymphaeifolia that has been shown to exert various biological functions. In a previous study, hernandonine was shown to suppress the proliferation of several solid tumor cell lines without affecting normal human cell lines. However, little is known about the effect of hernandonine on HCC. Therefore, this study aimed to investigate the effect and mechanism of hernandonine on HCC in relation to autophagy. We found that hernandonine inhibited HCC cell growth in vitro and in vivo. In addition, hernandonine elicited autophagic cell death and DNA damage in HCC cells. RNA-seq analysis revealed that hernandonine upregulated p53 and Hippo signaling pathway-related genes in HCC cells. Small RNA interference of p53 resulted in hernandonine-induced autophagic cell death attenuation. However, inhibition of YAP sensitized HCC cells to hernandonine by increasing the autophagy induction. This is the first study to illustrate the complex involvement of p53 and YAP in the hernandonine-induced autophagic cell death in human HCC cells. Our findings provide novel evidence for the potential of hernandonine as a therapeutic agent for HCC treatment.

FGF2 drives osteosarcoma metastasis through activating FGFR1-4 receptor pathway-mediated ICAM-1 expression.

Osteosarcoma is a malignant tumor with high metastatic potential, such that the overall 5-year survival rate of patients with metastatic osteosarcoma is only 20%. Therefore, it is necessary to unravel the mechanisms of osteosarcoma metastasis to identify predictors of metastasis by which to develop new therapies. Fibroblast growth factor 2 (FGF2) is a growth factor involved in embryonic development, cell migration, and proliferation. The overexpression of FGF2 and FGF receptors (FGFRs) has been shown to enhance cancer cell proliferation in lung, breast, gastric, and prostate cancers as well as melanoma. Nonetheless, the roles of FGF2 and FGFRs in human osteosarcoma cells remain unknown. In the present study, we found that FGF2 was overexpressed in human osteosarcoma sections and correlated with lung metastasis. Treatment of FGF2 induced migration activity, invasion activity, and intercellular adhesion molecule (ICAM)-1 expression in osteosarcoma cells. In particular, the downregulation or antagonism of FGFR1-4 suppressed FGF2-induced ICAM-1 expression and cancer cell migration. Furthermore, FGFR1, FGFR2, FGFR3, and FGFR4 were involved in FGF2-induced the phospholipase Cß/protein kinase Cα/proto-oncogene c-Src signaling pathway and triggered c-Jun nuclear translocation. Subsequent c-Jun upregulation of activator protein-1 transcription activity on the ICAM-1 promoter led to an increased migration of osteosarcoma cells. Moreover, the knockdown of endogenous FGF2 suppressed ICAM-1 expression and migration of osteosarcoma cells. These findings suggest that FGF2/FGFR1-4 signaling promotes metastasis via its direct downstream target gene ICAM-1, revealing a novel potential therapeutic target for osteosarcoma.

Critical role of heme oxygenase-1 in chaetoglobosin A by triggering reactive oxygen species mediated mitochondrial apoptosis in colorectal cancer.

The incidence rate of colorectal cancer (CRC) has been increasing and poses severe threats to human health worldwide and developing effective treatment strategies remains an urgent task. In this study, Chaetoglobosin A (ChA), an endophytic fungal metabolite from the medicinal herb-derived fungus Chaetomium globosum Km1126, was identified as a potent and selective antitumor agent in human CRC. ChA induced growth inhibition of CRC cells in a concentration-dependent manner but did not impair the viability of normal colon cells. ChA triggered mitochondrial intrinsic and caspase-dependent apoptotic cell death. In addition, apoptosis antibody array analysis revealed that expression of Heme oxygenase-1 (HO-1) was significantly increased by ChA. Inhibition of HO-1 increased the sensitivity of CRC cells to ChA, suggesting HO-1 may play a protective role in ChA-mediated cell death. ChA induced cell apoptosis via the induction of reactive oxygen species (ROS) and ROS scavenger (NAC) prevented ChA-induced cell death, mitochondrial dysfunction, and HO-1 activation. ChA promoted the activation of c-Jun N-terminal kinase (JNK), and co-administration of JNK inhibitor or siRNA markedly reversed ChA-mediated apoptosis. ChA significantly decreased the tumor growth without eliciting any organ toxicity or affecting the body weight of the CRC xenograft mice. This is the first study to demonstrate that ChA exhibits promising anti-cancer properties against human CRC both in vitro and in vivo. ChA is a potential therapeutic agent worthy of further development in clinical trials for cancer treatment.

Cryptocaryone induces apoptosis in human hepatocellular carcinoma cells by inhibiting aerobic glycolysis through Akt and c-Src signaling pathways.

Hepatocellular carcinoma (HCC) is the most common form of liver cancer, with the second highest mortality rate in all cancer. Energy reprogramming is one of the hallmarks of cancer, and emerging evidence showed that targeting glycolysis is a promising strategy for HCC treatment. Cryptocaryone has been shown to display promising anti-cancer activity against numerous types of cancer. Previous study also indicated that cryptocaryone induces cytotoxicity by inhibiting glucose transport in cancer cells, but the detailed mechanism still needs to be elucidated. Therefore, this study aimed to investigate the relationship between the anti-cancer effect and glycolytic metabolism of cryptocaryone in human HCC cells. In this study, we found that cryptocaryone potently induced growth inhibition by apoptotic cell death in HCC cells. Cryptocaryone also suppressed the ATP synthesis, lactate production and glycolytic capacity of HCC cells. Mechanistic investigations showed that phosphorylation of Akt and c-Src, as well as the expression of HK1 were impeded by cryptocaryone. Moreover, cryptocaryone markedly increased the expression level of transcription factor FoxO1. Importantly, clinical database analysis confirmed the negative correlation between HK1 and FoxO1. High expression levels of HK-1 were positively correlated with poorer survival in patients with HCCs. These results suggest that cryptocaryone may promote cell apoptosis by inhibiting FoxO1-mediated aerobic glycolysis through Akt and c-Src signaling cascades in human HCC cells. This is the first study to indicate that cryptocaryone exerts anti-cancer property against human HCC cells. Cryptocaryone is a potential natural product worthy of further development into a promising candidate for HCC treatment.

Protodioscin Induces Mitochondrial Apoptosis of Human Hepatocellular Carcinoma Cells Through Eliciting ER Stress-Mediated IP3R Targeting Mfn1/Bak Expression.

Objective: Protodioscin (PD), a steroidal saponin, has a diverse pharmacological activity including neuroprotection, male fertility improvement, and cytotoxicity against various cancers cell lines of different origins. However, the effect of PD on hepatocellular carcinoma (HCC) is still unclear. Methods: Cell viability, colony formation and flow cytometry analysis for apoptosis profile, mitochondrial membrane potential endoplasmic reticulum (ER) expansion were employed to determine the effect of PD against HCC cells. Transient transfection of siRNA, immunofluorescent imaging and immunoprecipitation were used to elucidate the anti-cancer mechanism of PD. The in vivo toxicity and efficacy of PD were assessed by a xenograft mouse model. Results: PD induced apoptosis, loss of mitochondrial membrane potential and ER expansion in HCC cells. Either downregulation of Mfn1 or Bak reversed PD-induced apoptosis and loss of mitochondrial membrane potential. Further analysis revealed that Mfn1 and Bak will form a complex with IP3R to facilitate the transfer of Ca2+ from ER to mitochondria and apoptosis. In addition, our tumour xenograft model further verifies the in vivo anti-tumour effect of PD. Conclusion: Our study sheds light on the understanding of the anti-HCC effects of PD and may open new aspects for the development of novel treatment for human hepatocellular carcinoma.

Effect of phenylurea hydroxamic acids on histone deacetylase and VEGFR-2.

A series of phenylurea hydroxamic acids incorporating pharmacophores of inhibitors of HDAC inhibitors and VEGFR-2 has been designed. Most of the compounds show antiproliferative activity comparable to that of Vorinostat and Sorafenib, and better EPC inhibitory activity. Enzymatic assays and Western blotting results indicated that compound 14 not only inhibits HDAC but also has slight VEGFR-2 inhibitory activity. A docking study revealed that the polar hydroxamic acid retains the interaction with HDAC through a zinc ion and also interacts with some residues of the active site of VEGFR-2. Despite 14 displaying a weaker VEGFR-2 activity, a possible route to develop potent HDAC/VEGFR-2 inhibitors is suggested.

Overexpression of Lipocalin-2 Inhibits Proliferation and Invasiveness of Human Glioblastoma Multiforme Cells by Activating ERK Targeting Cathepsin D Expression.

Lipocalin-2 (LCN2) exhibits pro- and anti-carcinogenic effects in several cancers, but its role in the progression of glioblastoma multiforme (GBM) remains unclear. This study aims to elucidate the effect of LCN2 in human GBM cell, and the mechanism underlying its effects on GBM malignant progression. We observed that LCN2 expression was significantly lower in GBM than in normal tissues and was associated with poorer GBM patient survival. LCN2-overexpressing GBM cells showed significantly reduced proliferation and migration/invasion abilities. Human protease antibody array analysis showed that the expression of cathepsin D (CTSD) protein and mRNA was lower in LCN2-overexpressing GBM cells than in controls. Higher CTSD expression was observed in GBM tumors than in normal tissues, and higher CTSD expression was associated with poorer overall and disease-free survival. LCN2-overexpressing GBM cells exhibited increased ERK phosphorylation. Treatment of these cells with a MEK inhibitor (U0126) restored CTSD expression, cell migration, and cell invasiveness. In conclusion, LCN2 might be serving as a prognostic marker and promising anti-proliferative and anti-metastatic target for treating GBM.

Moscatilin Inhibits Metastatic Behavior of Human Hepatocellular Carcinoma Cells: A Crucial Role of uPA Suppression via Akt/NF-κB-Dependent Pathway.

Hepatocellular carcinoma (HCC) frequently shows early invasion into blood vessels as well as intrahepatic metastasis. Innovations of novel small-molecule agents to block HCC invasion and subsequent metastasis are urgently needed. Moscatilin is a bibenzyl derivative extracted from the stems of a traditional Chinese medicine, orchid Dendrobium loddigesii. Although moscatilin has been reported to suppress tumor angiogenesis and growth, the anti-metastatic property of moscatilin has not been elucidated. The present results revealed that moscatilin inhibited metastatic behavior of HCC cells without cytotoxic fashion in highly invasive human HCC cell lines. Furthermore, moscatilin significantly suppressed the activity of urokinase plasminogen activator (uPA), but not matrix metalloproteinase (MMP)-2 and MMP-9. Interestingly, moscatilin-suppressed uPA activity was through down-regulation the protein level of uPA, and did not impair the uPA receptor and uPA inhibitory molecule (PAI-1) expressions. Meanwhile, the mRNA expression of uPA was inhibited via moscatilin in a concentration-dependent manner. In addition, the expression of phosphorylated Akt, rather than ERK1/2, was inhibited by moscatilin treatment. The expression of phosphor-IκBα, and -p65, as well as κB-luciferase activity were also repressed after moscatilin treatment. Transfection of constitutively active Akt (Myr-Akt) obviously restored the moscatilin-inhibited the activation of NF-κB and uPA, and cancer invasion in HCC cells. Taken together, these results suggest that moscatilin impedes HCC invasion and uPA expression through the Akt/NF-κB signaling pathway. Moscatilin might serve as a potential anti-metastatic agent against the disease progression of human HCC.

Additional alkaloids from Zoanthus vietnamensis with neuroprotective and anti-angiogenic effects.

A chemical investigation of the zoantharian Zoanthus vietnamensis, collected off Taiwan, yielded eleven new alkaloids, 7α-hydroxykuroshine J (1), 18ß-hydroxykuroshine J (2), 5α-hydroxyzoanthenamine (3), 5ß-hydroxyzoanthenamine (4), 14α-hydroxyzoanthenamine (5), 30-hydroxyzoanthenamine (6), 11-dehydroxy-18-epi-kuroshine A (7), 5α-hydroxykuroshine A (8), 7ß-hydroxykuroshine A (9), 11-keto-oxyzoanthamine (10), and 30-hydroxyzoanthamine (11), along with eight known compounds (12-19). The structures of these compounds were identified by detailed spectroscopic data, including HRESIMS, IR, NMR, and UV spectra. All secondary metabolites isolated from Z. vietnamensis were investigated for the anti-angiogenic effect in human endothelial progenitor cells (EPCs). Compounds 6, 7, 11, and 13 exhibited mild anti-angiogenic effect by blocking cell growth and tube formation of EPCs. The neuroprotective potential of four major compounds 12, 14, 15, and 19 against paclitaxel-induced neurotoxicity was evaluated. Pretreatment of 14 and 15 protected paclitaxel-damaged neurite outgrowth of dorsal root ganglion (DRG) neurons, without interfering the cytotoxic activity of paclitaxel on cervical cancer SiHa cells.

Anti-lymphangiogenic diterpenes from the bark of Calocedrus macrolepis var. formosana.

Eight new diterpenes, 6α,7ß-dihydroxyferruginol (1), 6α,7α-dihydroxyferruginol (2), 6α-hydroxyhinokiol (3), 4α-hydroxy-7-oxo-18-norabieta-8,11,13-trien-4α-ol (4a), 15,16-dehydrosugiol (5), 7-methoxy-6,7-secoabieta-8,11,13-triene-6,12-diol (6), 7α-acetoxyabieta-8,12-diene-11,14-dione (7), 7α-butyloxyethyloxyabieta-8,12-diene-11,14-dione (8), along with four known compounds, 6,7-dehydroferruginol (9), 12-hydroxy-6,7-secoabieta-8,11,13-triene-6,7-dial (10), 7α-11-dihydroxy-12-methoxy-8,11,13-abietatriene (11), and 11,14-dihydroxy-8,11,13-abietatrien-7-one (12) were successfully isolated from the bark of Calocedrus macrolepis var. formosana. The structures of all isolates were elucidated by physical data (appearance, UV, IR, optical rotation) and spectroscopic data (1D, 2D NMR, and HREIMS). Compounds 9, 10, 11, and 12 showed promising growth-inhibitory effect on human lymphatic endothelial cells (LECs). Among these compounds, compound 10 exerted the most potent anti-lymphangiogenesis property by suppressing cell growth and tube formation of LECs. In conclusion, the results revealed the anti-lymphangiogenic potentials of Formosan C. macrolepis var. formosana.

Praeruptorin A reduces metastasis of human hepatocellular carcinoma cells by targeting ERK/MMP1 signaling pathway.

Praeruptorin A (PA) is one of the active ingredients found in the dried root of Peucedanum praeruptorum Dunn, has been reported to possess anticancer effects against various types of cancer. However, the effect of PA on human hepatocellular carcinoma (HCC) remains uncleared. In this study, our results indicated that PA did not induce cytotoxicity or alter cell cycle distribution in human HCC cells (Huh-7, SK-Hep-1, and PLC/PRF/5 cells). Instead, PA inhibited the migration and invasion of human HCC cells while downregulating the expression of matrix metalloproteinase-1 (MMP1) and activating the extracellular signal-regulated kinase (ERK) signaling pathways. Furthermore, blocking the ERK signaling pathway through siERK restored the expression of MMP1 and the invasive ability of PA-treated HCC cells. In conclusion, our results demonstrate the antimetastatic activity of PA against human HCC cells, supporting its potential as a therapeutic agent of HCC treatments.

Whole-exome sequencing in the clinical setting: Establishing a foothold for precision medicine in genodermatoses and other diseases

@#The concept of “precision medicine” has been a mainstay in discourses about the future of medicine, although it was not until the completion of the Human Genome Project that genetic associations to Mendelian diseases have risen dramatically. Since genetic variations in most (85%) monogenic or oligogenic diseases reside in exons, whole-exome sequencing (WES) serves as a pivotal tool in the identification of causative variants in genodermatoses and other diseases, leading to efficient and timely diagnosis. Here, we share our current diagnosis protocol for genodermatoses using WES as a first-tier solution. Two cases are presented to demonstrate the process of identifying germline variants and one case for a somatic variant. In the first case, a germline missense mutation in COL7A1 (exon73:c.G6127A) was identified for a patient that presented with clinical symptoms of dystrophic epidermolysis bullosa (DEB). Immunofluorescence study revealed decreased collagen VII expression in the dermal-epidermal junction. In case 2, we detected a germline missense mutation in KRT16 (exon1:c.374A>G) in a patient with palmoplantar keratoderma (PPK) and congenital pachyonychia. Sanger sequencing and segregation analysis confirmed the variant detected in WES. For case 3, a patient with linear nevus comedonicus was found to have a somatic missense mutation in NEK9 (exon4:c.500T>C), which was only detected in the lesional DNA sample. Thus, WES shows great potential as a diagnostic tool for monogenic or oligogenic genodermatoses. Since omics is a technology-driven tool, we expect that reaching precision medicine is ever closer.

Endothelial Cell-Specific Molecule 1 Promotes Endothelial to Mesenchymal Transition in Renal Fibrosis.

The endothelial-to-mesenchymal transition (EndoMT) is involved in the complex pathogenesis of renal fibrosis. The soluble proteoglycan endothelial cell-specific molecule 1 (ESM1) is significantly upregulated in many tumor cells and cirrhosis-related disease. The role of ESM1 in renal fibrosis is unknown. This study investigates the role of ESM1 in renal fibrosis, using an in vivo unilateral ureteral obstruction (UUO) mouse model of renal fibrosis and in vitro mouse kidney MES 13 cells overexpressing ESM1. We observed that ESM1 overexpression significantly increased the motility and migration of MES 13 cells, independent of cell viability. In ESM1-overexpressing MES 13 cells, we also observed elevated expression of mesenchymal markers (N-cadherin, vimentin, matrix metallopeptidase 9 (MMP9)) and the fibrosis marker α-smooth muscle actin (α-SMA) and decreased expression of the endothelial marker vascular endothelial cadherin (VE-cadherin) and CD31. In a mouse model of fibrosis induced by unilateral ureter obstruction, we observed time-dependent increases in ESM1, α-SMA, and vimentin expression and renal interstitial collagen fibers in kidney tissue samples. These results suggest that ESM1 may serve as an EndoMT marker of renal fibrosis progression.

Inhibition of eIF2α dephosphorylation accelerates pterostilbene-induced cell death in human hepatocellular carcinoma cells in an ER stress and autophagy-dependent manner.

Hepatocellular carcinoma (HCC) is the one of the most common cancers worldwide. Because the side effects of current treatments are severe, new effective therapeutic strategies are urgently required. Pterostilbene (PT), a natural analogue of resveratrol, has diverse pharmacologic activities, including antioxidative, anti-inflammatory and antiproliferative activities. Here we demonstrated that PT inhibits HCC cell growth without the induction of apoptosis in an endoplasmic reticulum (ER) stress- and autophagy-dependent manner. Mechanistic studies indicated that the combination of salubrinal and PT modulates ER stress-related autophagy through the phospho-eukaryotic initiation factor 2α/activating transcription factor-4/LC3 pathway, leading to a further inhibition of eIF2α dephosphorylation and the potentiation of cell death. An in vivo xenograft analysis revealed that PT significantly reduced tumour growth in mice with a SK-Hep-1 tumour xenograft. Taken together, our results yield novel insights into the pivotal roles of PT in ER stress- and autophagy-dependent cell death in HCC cells.

Comparative transcriptomic analysis reveals adriamycin-induced apoptosis via p53 signaling pathway in retinal pigment epithelial cells / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

OBJECTIVE@#This paper applied a transcriptomic approach to investigate the mechanisms of adriamycin (ADR) in treating proliferative vitreoretinopathy (PVR) using ARPE-19 cells.@*METHODS@#The growth inhibitory effects of ADR on ARPE-19 cells were assessed by sulforhodamine B (SRB) assay and propidium iodide (PI) staining using flow cytometry. The differentially expressed genes between ADR-treated ARPE-19 cells and normal ARPE-19 cells and the signaling pathways involved were investigated by microarray analysis. Mitochondrial function was detected by JC-1 staining using flow cytometry and the Bcl-2/Bax protein family. The phosphorylated histone H2AX (γ-H2AX), phosphorylated checkpoint kinase 1 (p-CHK1), and phosphorylated checkpoint kinase 2 (p-CHK2) were assessed to detect DNA damage and repair.@*RESULTS@#ADR could significantly inhibit ARPE-19 cell proliferation and induce caspase-dependent apoptosis in vitro. In total, 4479 differentially expressed genes were found, and gene ontology items and the p53 signaling pathway were enriched. A protein-protein interaction analysis indicated that the TP53 protein molecules regulated by ADR were related to DNA damage and oxidative stress. ADR reduced mitochondrial membrane potential and the Bcl-2/Bax ratio. p53-knockdown restored the activation of c-caspase-3 activity induced by ADR by regulating Bax expression, and it inhibited ADR-induced ARPE-19 cell apoptosis. Finally, the levels of the γ-H2AX, p-CHK1, and p-CHK2 proteins were up-regulated after ADR exposure.@*CONCLUSIONS@#The mechanism of ARPE-19 cell death induced by ADR may be caspase-dependent apoptosis, and it may be regulated by the p53-dependent mitochondrial dysfunction, activating the p53 signaling pathway through DNA damage.

A study of color illumination effect on the SNR of rPPG signals.

Remote photoplethysmography (rPPG) can be used to measure cardiac activity by detecting the subtle color variation of the human skin tissue using an RGB camera. Recent studies have presented the feasibility and proposed multiple methods to improve the motion robustness for the subject movements. However, enhancing the signal-to-noise ratio (SNR) of the rPPG signal is still an important issue for the contactless measurement. In this paper, we conducted an experiment to study the lighting effect on the SNR of rPPG signals. The results point out that different colors of light sources provide different SNR in each RGB channel. By providing the dedicated light sources (λ= 490-620) nm, the SNR of rPPG signals captured from the green color channel can be enhanced. Among the tested light sources, light green provides the most significant improvement from -11.09 to -6.6 dB compared with the fluorescent light.

Activation of the NLRP3 inflammasome in lipopolysaccharide-induced mouse fatigue and its relevance to chronic fatigue syndrome.

BACKGROUND: The NLRP3 inflammasome (NOD-like receptor family, pyrin domain containing 3) is an intracellular protein complex that plays an important role in innate immune sensing. Its activation leads to the maturation of caspase-1 and regulates the cleavage of interleukin (IL)-1ß and IL-18. Various studies have shown that activation of the immune system plays a pivotal role in the development of fatigue. However, the mechanisms underlying the association between immune activation and fatigue remained elusive, and few reports have described the involvement of NLRP3 inflammasome activation in fatigue. METHODS: We established a mouse fatigue model with lipopolysaccharide (LPS, 3 mg/kg) challenge combined with swim stress. Both behavioural and biochemical parameters were measured to illustrate the characteristics of this model. We also assessed NLRP3 inflammasome activation in the mouse diencephalon, which is the brain region that has been suggested to be responsible for fatigue sensation. To further identify the role of NLRP3 inflammasome activation in the pathogenesis of chronic fatigue syndrome (CFS), NLRP3 KO mice were also subjected to LPS treatment and swim stress, and the same parameters were evaluated. RESULTS: Mice challenged with LPS and subjected to the swim stress test showed decreased locomotor activity, decreased fall-off time in a rota-rod test and increased serum levels of IL-1ß and IL-6 compared with untreated mice. Serum levels of lactic acid and malondialdehyde (MDA) were not significantly altered in the treated mice. We demonstrated increased NLRP3 expression, IL-1ß production and caspase-1 activation in the diencephalons of the treated mice. In NLRP3 KO mice, we found remarkably increased locomotor activity with longer fall-off times and decreased serum IL-1ß levels compared with those of wild-type (WT) mice after LPS challenge and the swim stress test. IL-1ß levels in the diencephalon were also significantly decreased in the NLRP3 KO mice. By contrast, IL-6 levels were not significantly altered. CONCLUSIONS: These findings suggest that LPS-induced fatigue is an IL-1ß-dependent process and that the NLRP3/caspase-1 pathway is involved in the mechanisms of LPS-induced fatigue behaviours. NLRP3/caspase-1 inhibition may be a promising therapy for fatigue treatment.

Effects of mass retention of dissolved organic matter and membrane pore size on membrane fouling and flux decline.

Ultrafiltration (UF) fouling has been attributed to concentration polarization, gel layer formation as well as outer and inner membrane pore clogging. It is believed that mass of humic materials either retained on membrane surface or associated with membrane inner pore surface is the primary cause for permeate flux decline and filtration resistance build-up in water supply industries. While biofilm/biofouling and inorganic matter could also be contributing factors for permeability decline in wastewater treatment practices. The present study relates UF fouling to mass of dissolved organic matter (DOM) retained on membrane and quantifies the effect of retained DOM mass on filtration flux decline. The results demonstrate that larger pore membranes exhibit significant flux decline in comparison with the smaller ones. During a 24-h period, dissolved organic carbon mass retained in 10 kDa membranes was about 1.0 gm(-2) and that in 100 kDa membranes was more than 3 times higher (3.6 gm(-2)). The accumulation of retained DOM mass significantly affects permeate flux. It is highly likely that some DOMs bind or aggregate together to form surface gel layer in the smaller 10 kDa UF system; those DOMs largely present in inner pore and serving as pore blockage on a loose membrane (100 kDa) are responsible for severe flux decline.