Source apportionment of microplastics in indoor dust: Two strategies based on shape and composition.

Microplastic (MP) pollution is widely distributed in the environment. However, methods for source apportionment of MPs are still lacking. In this study, the shape and size of 102,860 MPs in indoor dust from 39 cities of China were analyzed by laser direct infrared, and accordingly, a shape index (fshape) based on MP's aspect ratio was developed to assess the contribution of textiles release. In addition, a composition index (fcomp) based on the ratio of the mass concentration of polyethylene terephthalate (PET) to polyamide (PA), which were detected by liquid chromatography-tandem mass spectrometry, was proposed. The contribution of textile source and non-textile source to the indoor MPs were also estimated based on fcomp. It is estimated by fshape that 43% of MPs in indoor dust was released from textiles. Among the most abundant MPs in indoor dust, 98% of polyurethane, 94% of PA and 92% of PET come from the textile source, 76% of polypropylene and almost all of polyethylene come from the non-textile source. fcomp indicates that 83% of PET MPs comes from textile source, i.e., polyester. Considering the application proportion of PET in textile and non-textile industry, it is estimated that 59% of MPs in indoor dust comes from textile source, which is similar to the result obtained by fshape.

Oxidative potential of heavy-metal contaminated soil reflects its ecological risk on earthworm.

The ecological risk of heavy metal-contaminated soil is usually evaluated by its oxidative stress on terrestrial animals, which are vulnerable to the impact of individual differences of animals and environmental conditions. Oxidative potential (OP) is the potential of particles to induce the formation of reactive oxygen species (ROS). In this study, OP of the in situ contaminated soils collected from an industrial site (i.e., 64.5-7783 mg/kg of Cu, 54.9-397 mg/kg of Pb, 278-2085 mg/kg of Zn and 0.615-121 mg/kg of Cd) were measured as 38.0-60.1 pmol/min/mg, and the water extractable Cu, Pb, Zn, and Cd in soils have been proved to contribute 89%-98% to OP. Oxidative stress in earthworms (Eisenia fetida) caused by the industrial contaminated soils can be reflected by the biomarkers such as 8-hydroxy-2'-deoxyguanosine, metallothionein, and antioxidant enzymes, and a negative correlation presents between the comprehensive biomarker response index and the OP of soils (r = -0.979, p < 0.01). This is the first time to propose a dose-response relationship between OP and oxidative stress. Metabolomic analysis also verified that the regulation of four ROS-related metabolites (i.e., l-pipecolate, 1-methylhistidine, 5-methoxytryptamine, and xanthosine) in earthworms treated with contaminated soil were directly correlated with OP values. These results indicate that OP can be used as an indicator for ecological risk assessment of heavy metal-contaminated soil, which provides a fast, stable and easily testable chemical method.

Slower antibiotics degradation and higher resistance genes enrichment in plastisphere.

Microplastics (MPs) are increasingly entering the urban aquatic ecosystems, and the environmental significance and health risks of plastisphere, a special biofilm on MPs, have received widespread attention. In this study, MPs of polylactic acid (PLA) and polyvinyl chloride (PVC) and quartzite were incubated in an urban water environment, and the tetracycline (TC) degradation ability was compared. Approximatedly 24% of TC biodegraded in 28 d in the water-quartzite system, which is significantly higher than that in the water-PLA (17.3%) and water-PVC systems (16.7%). Re-incubation of microorganisms in biofilms affirmed that quartzite biofilm has a higher TC degradation capacity than the plastisphere. According to high-throughput sequencing of 16S rRNA and metagenomic analysis, quartzite biofilm contained more abundant potential TC degrading bacteria, genes related to TC degradation (eutG, aceE, and DLAT), and metabolic pathways related to TC degradation. An oligotrophic environment on the quartzite surface might lead to the higher metabolic capacity of quartzite biofilm for unconventional carbons, e.g., TC. It is also found that, compared with quartzite biofilm, the distinct microbes in the plastisphere carried more antibiotic resistance genes (ARGs). Higher affinity of MPs surface to antibiotics may lead to higher antibiotics stress on the plastisphere, which further amplify the carrying capacity for ARGs of microorganisms in the plastisphere. Compared to the nondegradable PVC MPs, surface of the biodegradable PLA plastics harbored significantly higher amounts of biomass and ARGs. Compared to the mineral particles, the capability of plastisphere has lower ability to degrade unconventional carbon sources such as the refractory organic pollutants, due to the abundance of carbon sources (adsorbed organic carbon and endogenous organic carbon) on the MPs surface. Meanwhile, the stronger adsorption capacity for pollutants also leads to higher pollutant stress (such as antibiotic stress) in plastisphere, which in turn affects the microbiological characteristics of the plastisphere itself, such as carrying more ARGs.

Differences in the Plastispheres of Biodegradable and Non-biodegradable Plastics: A Mini Review.

There has been a steady rise in the production and disposal of biodegradable plastics. Unlike the microorganisms present in the biofilms on non-biodegradable plastic surfaces (the "plastisphere"), the plastisphere of biodegradable plastic has not been well-characterized. As the polymer structure of biodegradable plastic has a higher microbial affinity than that of non-biodegradable plastic, their plastispheres are assumed to be different. This review summarizes the reported differences in microbial communities on the surface of biodegradable and non-biodegradable plastics, discusses the driving forces behind these differences, and discusses the potential environmental risks. Overall, the plastisphere biomass on the surface of non-biodegradable plastic was observed to be lower than that of biodegradable plastic. The community structure of microbes in both plastispheres was diverse, mainly due to the properties of the plastic surface, such as surface charge, hydrophilicity/hydrophobicity, roughness, and bioavailability of polymer components for microbes. Further research should focus on developing biodegradable plastic that degrade faster in the environment, revealing the mechanism of enrichment of ARGs and potential pathogens on plastics, and understanding the potential influence of plastispheres on the evolution and selection of plastic-degrading microbial potential.

Excretion characteristics of nylon microplastics and absorption risk of nanoplastics in rats.

Ingestion of environmental microplastics (MPs) by animals is receiving a great health concern, because of its potential adverse effects on organisms. Most ingested MPs will be excreted, while the health threats depend largely on the excretory dynamics. Although the excretion characteristics of MPs in invertebrates and fishes have been studied, information on the excretion of MPs in mammals remains lacking, especially for the fibrous MPs. Here, fibrous and granular MP and nanoplastic (NP) of nylon polymer (polyamide 66, PA66) were exposed in rats by oral in the first day, then the excretion behavior of ingested PA66 in rats was quantified using mass quantification of liquid chromatography with tandem mass spectrometry (LC-MS-MS) together with the microscope observation. Although most of the ingested PA66-MP or PA66-NP was excreted within 48 h, the three forms of PA66 were not completely cleared by the rats even after seven days excretion. The excretion of PA66 in rats was well-described by a first-order kinetics model, and the calculated half-lives of elimination of PA66 polymer in rats are 19.9 h (fibrous PA66-MP), 23.7 h (granular PA66-MP), and 36.9 h (PA66-NP), indicating rats excrete smaller MPs more slowly than the bigger ones. This was further confirmed by the particle size distribution of granular PA66-MP observed in feces. Besides, approximately 30% of the ingested PA66-NP were failed to be detected in feces, while the occurrence of PA66-NP in rat serum induced by PA66-NP ingestion was found. This indicates that PA66-NP can pass through the gut barrier and entered the blood circulation. Therefore, the health risks of ingested MPs, especially for the NPs, deserve further attention.

Recent advances and trends of trichloroethylene biodegradation: A critical review.

Trichloroethylene (TCE) is a ubiquitous chlorinated aliphatic hydrocarbon (CAH) in the environment, which is a Group 1 carcinogen with negative impacts on human health and ecosystems. Based on a series of recent advances, the environmental behavior and biodegradation process on TCE biodegradation need to be reviewed systematically. Four main biodegradation processes leading to TCE biodegradation by isolated bacteria and mixed cultures are anaerobic reductive dechlorination, anaerobic cometabolic reductive dichlorination, aerobic co-metabolism, and aerobic direct oxidation. More attention has been paid to the aerobic co-metabolism of TCE. Laboratory and field studies have demonstrated that bacterial isolates or mixed cultures containing Dehalococcoides or Dehalogenimonas can catalyze reductive dechlorination of TCE to ethene. The mechanisms, pathways, and enzymes of TCE biodegradation were reviewed, and the factors affecting the biodegradation process were discussed. Besides, the research progress on material-mediated enhanced biodegradation technologies of TCE through the combination of zero-valent iron (ZVI) or biochar with microorganisms was introduced. Furthermore, we reviewed the current research on TCE biodegradation in field applications, and finally provided the development prospects of TCE biodegradation based on the existing challenges. We hope that this review will provide guidance and specific recommendations for future studies on CAHs biodegradation in laboratory and field applications.

Bacterial Community under the Influence of Microplastics in Indoor Environment and the Health Hazards Associated with Antibiotic Resistance Genes.

Selectively colonized microbial communities and enriched antibiotic resistance genes (ARGs) in (micro)plastics in aquatic and soil environments make the plastisphere a great health concern. Although microplastics (MPs) are distributed in indoor environments in high abundance, information on the effect of MPs on a microbial community in an indoor environment is lacking. Here, we detected polymers (containing MPs and natural polymers), bacterial communities, and 18 kinds of ARGs in collected indoor dust samples. A significant correlation by Procrustes analysis between bacterial community composition and the abundance of MPs was observed, and correlation tests and redundancy analysis identified specific associations between MP polymers and bacterial taxa, such as polyamide and Actinobacteria. In addition, the abundance of MPs showed a positive correlation with the relative abundance of the ARGs (to 16S RNA), while natural polymers, such as cellulosics, showed positive correlations with the absolute abundance of ARGs and 16S rRNA. Simulated experiments verified that significantly higher bacterial biomasses and ARGs were observed on the surface of cotton, hair, and wool than on MPs, while a higher relative abundance of ARGs was detected on MPs. However, a significantly higher amount of ARG was found on MPs of poly(lactic acid), the biodegradable plastics with the highest yield. In addition to the plastisphere in water and soil environments, MPs in an indoor environment may also affect the bacterial community and specifically enrich ARGs. Moreover, degradable MPs and nondegradable MPs may result in different health hazards due to their distinct effects on bacterial community.

Comparison of Detection Methods of Microplastics in Landfill Mineralized Refuse and Selection of Degradation Degree Indexes.

A landfill is an important sink of plastic waste and potential sources of microplastics (MPs) when mineralized refuse is reused. However, limitations are still present in quantifying MPs in mineralized refuse and assessing their degradation degree. In this study, laser direct infrared spectroscopy and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to identify MPs of mineralized refuse from a landfill. Although 25-113 items/g MPs were detected in particles subjected to flotation, 37.9-674 µg/g polyethylene terephthalate (PET) and 0.0716-1.01 µg/g polycarbonate (PC) were detected in the residual solids by LC-MS/MS, indicating a great amount of plastic polymers still presented in the residue. This suggests that the commonly used flotation-counting method will lead to significant underestimation of MP pollution in mineralized refuse, which might be due to the aging and aggregation process caused by the long-term landfill process. The ratio of "bisphenol A/PC" and "plasticizer/MPs" was found to be positively correlated and negatively correlated with the landfill age, respectively. Therefore, in addition to the spectral index such as the carbonyl index, new indexes based on the concentrations of polymers, free monomers, and plasticizers were proposed to characterize the degradation degree of MPs in a landfill.

Investigating into anti-cancer potential of lycopene: Molecular targets.

Lycopene, the main pigment of tomatoes, possess the strongest antioxidant activity among carotenoids. Lycopene has unique structure and chemical properties. We searched the literature, via PubMed, Embase, Web of Science and Google database so on to screen citations from inception to Oct 2020 for inclusion in this study. We found that as a common phytochemical, it did not attract much attention in the past few years. However, recent studies have indicated that, in addition to antioxidant activity and the second stage of detoxification, the anticancer of lycopene is also considered to be an important determinant of tumor development including the inhibition of cell proliferation, inhibition of cell cycle progression, induction of apoptosis, inhibition of cell invasion, angiogenesis and metastasis. The effect mechanisms of lycopene are related to the regulation of several signal transduction pathways, such as PI3K/Akt pathway, modulation of insulin-like growth factors system, the suppression of activity of sex steroid hormones, the modification of relevant gene expression, and the alteration of mitochondrial function. These novel findings have suggested that lycopene acts as a promising functional natural pigment, and may be associated with a decreased risk of different types of cancer. This review presents the latest knowledge with respect to its molecular mechanisms and its molecular targets of the inhibitory effects on carcinogenesis.

The impact of microplastic-microbe interactions on animal health and biogeochemical cycles: A mini-review.

Microplastic (MP) pollution has attracted global attention due to the extensive use of plastic products. The hydrophobic MP surface provides a habitat for multiple microorganisms. Although there have been several studies on the impact of plastic particles on microbial communities, there are few reviews that have systematically summarized the interaction between MPs and microbes and their effects on human health and biochemical circulation. The discussions in this review will take place under the following topics: (1) MPs prompt colonization, biofilm generation, and transfer of environmental microbes; (2) the microbial communities can cause the morphological alterations and biodegradation of MPs; (3) MP-microbe combinations can induce the alteration of intestinal flora and hazard animal health; (4) the biogeochemical cycles affected by MP-microbe interactions. This review will highlight the close interactions between MPs and microorganisms, and provide suggestions for future studies.

Distinct microplastic distributions in soils of different land-use types: A case study of Chinese farmlands.

Microplastic (MP) pollution poses a huge threat to agroecosystems, but the distribution characteristics of MPs in different types of farmland are still largely unknown. In this work, samples from six land-use types were collected from Chinese farmlands in five provinces. It was found that MP abundances were in the range of 2783-6366 items/kg in all samples. MP distribution results showed that over 80% of particles were less than 1 mm, and that MP sizes ranging between 0.02 and 0.2 mm represented the greatest proportion. The particle shape classified as fragment (with edges and angular) was the most frequent shape, with an abundance of approximately 54.05%. Polyethylene (PE) and polyamides (PA) were the most abundant polymers in cropped lands; 20.88% and 20.31%, respectively. Statistical analyses showed that lands used for plastic mulching (mulch film and greenhouse crops) had a significantly higher particle abundance, hence identifying plastic mulching as a major contributor to MP pollution in agricultural lands. Furthermore, paddy lands had a significantly higher MP abundance than wheat lands. Variation analyses of MP characteristics revealed that cereal crop farmlands (wheat, paddy land) were more likely to contain fibrous shapes and large MP particles (1-5 mm). Economically important tree lands (orchards, woodlands) were likely to contain fragment shapes and pony-size MPs (0.02-0.2 mm). Discrepancies among farmlands may depend on various reasons, such as mulching plastic application, irrigation, atmospheric fallout, etc. This study provides firsthand evidences about the characteristics of MP pollution in farmlands and explores some predominant MP sources in agroecosystems.

Development and Application of a Mass Spectrometry Method for Quantifying Nylon Microplastics in Environment.

The quantitative detection methods for many microplastic (MP) polymers in the environment are inadequate. For example, effective detection methods for nylon (polyamide, PA), a widely used plastic, in different environmental samples are still lacking. In the present study, a method based on acid depolymerization-liquid chromatography-tandem mass spectrometry (LC-MS/MS) and without the separation of MPs from samples was developed to quantify nylon MPs. After removing the background monomer compounds, PA6 and PA66 were efficiently depolymerized to 6-aminocaproic acid and adipic acid, respectively, and detected by LC-MS/MS. Accordingly, the quantity of nylon MPs was accurately calculated. By using the proposed method, the recovery of spiked PA6 and PA66 MPs in the environmental samples ranged from 90.8 to 98.8%. The limits of quantification for PA6 and PA66 MPs were 0.680 and 4.62 mg/kg, respectively. PA MPs were widely detected in indoor dust, sludge, marine sediment, freshwater sediment, fishery sediment, and fish guts and gills with concentrations of 0.725-321 mg/kg. Extremely high concentrations of PA66 MPs were detected in indoor dust and fish guts and gills, indicating the unequivocal risk of human exposure through dust ingestion and dietary exposure.

Effects of co-loading of polyethylene microplastics and ciprofloxacin on the antibiotic degradation efficiency and microbial community structure in soil.

Microplastics (MPs) have become a global environmental concern while soil plastic pollution has been largely overlooked. In view of the severe antibiotic contamination in arable soils owing to land application of sewage sludge and animal manure, the invasion of MPs along with antibiotics may pose an unpredictable threat to soil microbial communities and ecological health. In this work, polyethylene MPs and ciprofloxacin (CIP) were applied to a soil microcosm to investigate the CIP degradation behavior and their combined effects on soil microbial communities. Compared with that of the individual amendment of CIP, the co-amendment of CIP and MPs reduced the CIP degradation efficiency during the 35 d cultivation period. In addition, the high-throughput sequencing results illustrated that the combined loading of MPs and CIP in soil significantly decreased the microbial diversity compared with that of individual contamination. As for the community structure, the microbial compositions at the phylum level were consistent among all treatments, and the most dominant phyla were Proteobacteria, Actinobacteria, and Chloroflexi. At the genus level, only one genus, namely Arthrobacter, was remarkably changed in the CIP-amended soil compared with that in the blank control, but four genera were significantly altered in the MPs-CIP co-amended soil. Serratia and Achromobacter were abundant in the combined polluted soil, which might have been involved in accelerated depletion of soil total nitrogen based on redundancy analysis. These findings may contribute to the understanding of bacterial responses to the combined pollution of MPs and antibiotics in soil ecosystems.

Computational analysis suggests putative intermediate animal hosts of the SARS-CoV-2

The recent emerged SARS-CoV-2 may first transmit to intermediate animal host from bats before the spread to humans. The receptor recognition of ACE2 protein by SARS-CoVs or bat-originated coronaviruses is one of the most important determinant factors for the cross-species transmission and human-to-human transmission. To explore the hypothesis of possible intermediate animal host, we employed molecular dynamics simulation and free energy calculation to examine the binding of bat coronavirus with ACE2 proteins of 47 representing animal species collected from public databases. Our results suggest that intermediate animal host may exist for the zoonotic transmission of SARS-CoV-2. Furthermore, we found that tree shrew and ferret may be two putative intermediate hosts for the zoonotic spread of SARS-CoV-2. Collectively, the continuous surveillance of pneumonia in human and suspicious animal hosts are crucial to control the zoonotic transmission events caused by SARS-CoV-2.

Exploring the Abundance and Diversity of Bacterial Communities and Quantifying Antibiotic-Related Genes Along an Elevational Gradient in Taibai Mountain, China.

Thus far, no studies have investigated the soil microbial diversity over an elevational gradient in Taibai Mountain, the central massif of the Qinling Mountain Range. Here, we used Illumina sequencing and quantitative PCR of the 16S rRNA gene to assess the diversity and abundance of bacterial communities along an elevational gradient in representative vegetation soils in Taibai Mountain. We identified the soil, climate, and vegetation factors driving the variations in soil bacterial community structure by Pearson correlation and redundancy analysis. We also evaluated the potential for antibiotic discovery by quantitative PCR of the PKS-I, PKS-II, and NRPS genes from Actinobacteria. The results showed that soil bacterial alpha diversity increased first and then decreased with an elevational rise in both the northern and southern slopes of Taibai Mountain. The bacterial abundance was significantly correlated with soil organic matter and nitrate nitrogen. The average relative abundance of Actinobacteria in Taibai Mountain was markedly higher than those in other mountain forest soils. The absolute abundance of PKS and NPRS gene was significantly higher in the tested soils compared with the gene copy numbers reported in tropical urban soils. Taibai Mountain is rich in actinomycete resources and has great potential for antibiotic excavation.

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The effects of Bacillus Bs10, Ba12 and Bl10 on tomato growth and soil rhizosphere microorganisms were determined by Petri dish germination test and pot experiments. The results showed that Bs10, Ba12 and Bl10 exhibited remarkable promoting effect on the length of hypocotyl and radical, as well as the growth of plants. The length, surface area and volume of tomato roots increased significantly after treatment with Bacillus stains, the numbers and proportions of soil bacteria also increased markedly, while those of soil fungi decreased. The numbers of the dominant bacteria and fungi were changed, withBacillus methylotrophicus being much higher in root zone soil, surface soil and neouchi, while the plant pathogens Fusarium solani and Fusarium oxysporum decreased significantly in root zone soil and root surface soil. These results suggested that the addition of Bs10, Ba12 and Bl10 could improve the micro-ecosystem of the root domain of tomato, which might play an important role in growth promoting and disease prevention on tomato plants.

Effects of graded levels of cupric citrate on growth performance, antioxidant status, serum lipid metabolites and immunity, and tissue residues of trace elements in weaned pigs.

OBJECTIVE: The goal of this study was to investigate the effects of cupric citrate (CuCit) on growth performance, antioxidant indices, serum lipid metabolites, serum immune indices, and tissue residues of copper (Cu), zinc, and iron in weaned pigs. METHODS: A total of 180 weaned pigs (Duroc×Landrace×Large White) with an average body weight of 8.98±1.21 kg were randomly assigned to a corn-soybean meal control ration, or 4 similar rations with 30, 60, 120, or 240 mg/kg Cu as CuCit. All diets contained 10 mg/kg Cu as cupric sulfate from the vitamin-mineral premix. The experiment was divided into two phases: 0 to 14 d (phase 1) and 15 to 28 d (phase 2). RESULTS: Average daily gain (ADG; linearly, p<0.01) and average daily feed intake (ADFI; linearly and quadratically, p<0.05) were affected by an increase in CuCit during phase 2. Overall period, ADG (p<0.05) and ADFI (p<0.01) were linearly increased with increasing dietary levels of CuCit. Serum malondialdehyde concentrations (p<0.05) and glutathione peroxidase activity (p<0.01) linearly decreased and increased respectively with an increase in CuCit. Serum levels of Cu-Zn superoxide dismutase were linearly affected with an increase in CuCit (p<0.01). Hepatic malondialdehyde levels decreased with an increase in CuCit (linearly and quadratically, p<0.01). Serum total cholesterol concentrations were quadratically affected (p<0.05) and decreased in pigs fed Cu as CuCit at 60 and 120 mg/kg and increased in pigs fed 240 mg/kg Cu as CuCit. Serum high-density lipoprotein concentrations were linearly affected with an increase in CuCit (p<0.01). Serum IL-1ß levels were quadratically affected (p<0.05) by dietary treatment. Compared with other treatments, 240 mg/kg Cu from CuCit quadratically increased hepatic (p<0.01) and renal (p<0.05) Cu concentrations, and quadratically decreased hepatic and renal iron concentrations (p<0.05). CONCLUSION: Cu administered in the form of CuCit at a dosage range of 30 to 60 mg/kg, effectively enhanced the growth performance and antioxidant status of weaned pigs.

Dihydromyricetin from Ampelopsis grossedentata inhibits melanogenesis through down-regulation of MAPK, PKA and PKC signaling pathways.

The inhibitory effects of dihydromyricetin purified from Ampelopsis grossedentata on melanogenesis and its antioxidant characteristics were investigated. Assays of tyrosinase activities and melanin content in B16F10 mouse melanoma cells were carried out spectrophotometrically, and the expression of melanogenesis-related proteins was determined by Western blotting. The possible signaling pathways involved in dihydromyricetin-mediated depigmentation were also examined using specific protein kinase regulators. The results revealed that dihydromyricetin effectively suppresses intracellular tyrosinase activity and decreases melanin amount in cells. Dihydromyricetin also exhibits antioxidant properties and effectively decreases intracellular reactive oxygen species (ROS) and reactive species (RS) levels. Our results indicated that dihydromyricetin inhibits melanogenesis through its antioxidant properties and by downregulating protein kinase A (PKA), protein kinase C (PKC), and mitogen-activated protein kinases (MAPK) signaling pathways. The present study indicates that dihydromyricetin has the potential to be developed into a depigmentation skin care product.

Paclitaxel pretreatment overcomes hypoxia inducible factor-1α-induced radioresistance acquisition of human hepatoma and lung adenocarcinoma cells.

AIMS: This study delineated the mechanisms of paclitaxel (PTX) assistance in overcoming radioresistance in hepatoma and human lung adenocarcinoma (HLAC) cells. MAIN METHODS: The TUNEL assay was used as an index of radiosensitivity, and the MTT assay assessed the efficacy of various combined PTX/RT treatments. The efficacy of PTX disruptions of hypoxia-inducible factor-1 alpha (HIF-1α) was assessed using Western blotting. KEY FINDINGS: Normoxically overexpressed HIF-1α in hepatoma J5 cells was mechanistically linked to activation of the bFGF/PI3K/Akt pathway because the viability of these cells was strongly inhibited by either Akt inhibitors or an HIF-1α inhibitor. All of the cell lines used were extremely sensitive to PTX, and these effects also correlated excellently with HIF-1α suppression. We designed five combined radiation-PTX protocols of varying dose duration and treatment sequences against CL1-1 cells based on the gathered data. Pretreatment of CL1-1 cells with PTX (100nM) for 24h before irradiation (2.5Gy) was the best combined protocol to achieve maximum radiosensitizing effects. SIGNIFICANCE: Our data clearly indicate that PTX pretreatment is an effective radiosensitizing procedure against HIF-1α-expressing hepatoma and HLAC cells, which are constitutively endowed with radioresistance.