CRISPR/Cas gene editing and delivery systems for cancer therapy.

CRISPR/Cas systems stand out because of simplicity, efficiency, and other superiorities, thus becoming attractive and brilliant gene-editing tools in biomedical field including cancer therapy. CRISPR/Cas systems bring promises for cancer therapy through manipulating and engineering on tumor cells or immune cells. However, there have been concerns about how to overcome the numerous physiological barriers and deliver CRISPR components to target cells efficiently and accurately. In this review, we introduced the mechanisms of CRISPR/Cas systems, summarized the current delivery strategies of CRISPR/Cas systems by physical methods, viral vectors, and nonviral vectors, and presented the current application of CRISPR/Cas systems in cancer clinical treatment. Furthermore, we discussed prospects related to delivery approaches of CRISPR/Cas systems. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Pharmacological Activation of AMPK Prevents Drp1-mediated Mitochondrial Fission and Alleviates Hepatic Steatosis In vitro.

BACKGROUND: The incidence of non-alcoholic fatty liver disease (NAFLD) is increasing worldwide. Adenosine monophosphate-activated protein kinase (AMPK) activation is beneficial for NAFLD treatment. Recent studies show the excessive fission of mitochondria during NAFLD progression, so targeting mitochondria dynamics may be a possible target for NAFLD. Still, little is known about whether AMPK regulates mitochondrial dynamics in hepar. OBJECTIVE: This study investigated whether AMPK activation alleviates hepatic steatosis by regulating mitochondrial dynamics mediated by GTPase dynamin-related protein 1 (Drp1). METHODS: Human hepatocyte line L-02 cells were cultured and subjected to palmitic acid (PA) treatment for 24 h to establish a hepatic steatosis model in vitro, which was pre-treated with different tool drugs. Hepatocyte function, hepatocyte lipid content, mitochondrial reactive oxygen species (ROS) production, and mitochondrial membrane potential (MMP) were examined. The expression levels of genes and proteins associated with mitochondrial dynamics were assessed using reverse transcription-quantitative PCR and western blotting. RESULTS: The results indicated that 5-Aminoimidazole-4-carboxamide 1-ß-D-ribofuranoside (AICAR), an AMPK activator, improved hepatocyte function, as demonstrated by decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity (P＜0.05 or P＜0.01). In addition, AICAR decreased total cholesterol (TC) and triglyceride (TG) content and lipid deposition in hepatocytes (P＜0.01); decreased ROS production; improved MMP (P＜0.01); reduced fission-1 (Fis1) and mitochondrial fission factor (Mff) mRNA expression; and downregulated p-Drp1 (Ser 616) protein expression. In contrast, AICAR increased mitochondrial fusion factor mitofusin-1 (Mfn1) and mitofusin-2 (Mfn2) mRNA expression and upregulated p-Drp1 (Ser 637) protein expression. Mdivi-1, a Drp-1 inhibitor, was used to confirm whether mitochondrial dynamics regulated by Drp1-mediated the role of AICAR. Similar to AICAR, Mdivi-1 improved hepatocyte function and MMP significantly, decreased ROS production and lipid deposition, downregulated Fis1 and Mff mRNA expression, downregulated p-Drp1 (Ser 616) protein expression, and enhanced Mfn1 and Mfn2 mRNA and p-Drp1 (Ser 637) protein expression. However, Compound C, an AMPKspecific inhibitor, had less impact on the protective effect of Mdivi-1. CONCLUSION: The results demonstrated that AMPK activation has a protective effect on hepatic steatosis in vitro, largely dependent on the inhibition of Drp1-mediated mitochondrial fission.

Hierarchically tumor-activated nanoCRISPR-Cas13a facilitates efficient microRNA disruption for multi-pathway-mediated tumor suppression.

Rationale: CRISPR-Cas13a is an efficient tool for robust RNA knockdown with lower off-target effect, which may be a potentially powerful and safe tool for cancer gene therapy. However, therapeutic effect of current cancer gene therapy that targeting monogene was compromised by the multi-mutational signal pathway alterations of tumorigenesis. Methods: Here, hierarchically tumor-activated nanoCRISPR-Cas13a (CHAIN) is fabricated for multi-pathway-mediated tumor suppression by efficient microRNA disruption in vivo. A fluorinated polyetherimide (PEI; Mw=1.8KD) with graft rate of 33% (PF33) was utilized to compact the CRISPR-Cas13a megaplasmid targeting microRNA-21 (miR-21) (pCas13a-crRNA) via self-assemble to constitute a nanoscale 'core' (PF33/pCas13a-crRNA), which was further wrapped by modified hyaluronan (HA) derivatives (galactopyranoside-PEG2000-HA, GPH) to form CHAIN. Results: The dual-tumor-targeting and tumor-activated CHAIN not only manifested long-term circulation, but augmented tumor cellular uptake and endo/lysosomal escape, thus achieving efficient transfection of CRISPR-Cas13a megaplasmid (~ 13 kb) in tumor cells with minimal toxity. Efficient knockdown of miR-21 by CHAIN restored programmed cell death protein 4 (PDCD4) and reversion-inducing-cysteine-rich protein with Kazal motifs (RECK) and further crippled downstream matrix metalloproteinases-2 (MMP-2), which undermined cancer proliferation, migration and invasion. Meanwhile, the miR-21-PDCD4-AP-1 positive feedback loop further functioned as an enhanced force for anti-tumor activity. Conclusion: Treatment with CHAIN in hepatocellular carcinoma mouse model achieved significant inhibition of miR-21 expression and rescued multi-pathway, which triggered substantial tumor growth suppression. By efficient CRISPR-Cas13a induced interference of one oncogenic microRNA, the CHAIN platform exerted promising capabilities in cancer treatment.

Impact of Agricultural Division of Labor on Fertilizer Reduction Application: Evidence from Western China.

Nowadays, environmental friendly agriculture has become the world trend of modern agricultural development; fertilizer reduction application is an essential way to achieve sustainable development goals. With the deepening development of the agricultural specialized division of labor and socialized services, the division of labor economy can promote the economic input of fertilizer. Based on 540 survey data of farmers in the main rice-producing areas of Sichuan Province, this paper constructs a theoretical analytical framework for the impact of agricultural division of labor on fertilizer reduction application. A binary probit model was used to empirically analyze the effect of agricultural division of labor on fertilizer reduction application, and its mechanism was examined. The results show that: (1) both horizontal and vertical agricultural divisions of labor have positive and significant effects on the reduction in fertilizer application by rice farmers. All above results remain stable after treatment of endogeneity; (2) due to the migration of the rural labor, the horizontal division of labor is expressed as changes in the structure of labor and cultivation within the household which has changed. To achieve economies of scale, farmers increase specialization in production, resulting in reducing marginal cost and application of fertilizer; (3) the vertical division of labor is expressed in the adoption of external socialized services by farmers, which improves the land resource endowment of fragmentation and hydraulic conditions. Thus, it creates a good environment for fertilizer application to improve its application efficiency, which in turn promotes fertilizer reduction by farmers. Based on this, this paper proposes that the government should motivate farmers to deepen their participation in the horizontal and vertical division of labor. Meanwhile, it is also necessary to improve the agricultural specialization continuously and further promote the development of socialized services market.

Dual cancer stem cell manipulation to enhance phototherapy against tumor progression and metastasis.

Targeting breast cancer stem cells (BCSCs) therapy is a prospective strategy to eliminate tumors owing to the BCSCs-governed drug resistance, tumor progression and metastasis. BCSCs are intrinsically in a disequilibrium state with favorable ability of self-renewal rather than differentiation, resulting in inability of complete tumor eradication. Besides the original BCSCs, epithelial-mesenchymal transition (EMT) process can further facilitate BCSCs regeneration, accompanied by tumor progression and metastasis. Herein, we, for the first time, engineered a photodynamic nanoplatform to manipulate BCSCs against tumor progression and metastasis by not only remolding the disequilibrium state but also blocking the EMT process. The HP@PP was constructed by haloperidol (HP)-incorporated polyethyleneimine-polyhistidine (PP) micelles, which was further integrated with low molecular weight heparin (LMWH)-chlorin e6 (Ce6) conjugate (LC) to form HP@PP/LC nanoparticles (NPs). For HP@PP/LC NPs, the protonation of PP in tumor tissues precisely targeted HP to BCSCs for remolding the disequilibrium state via promoting BCSCs differentiation into tumor cells. Simultaneously, LC conjugate targeted to tumors for exerting EMT blocking ability with LMWH, as well as exerting photodynamic clearance of tumor cells with Ce6 component. Therefore, our nanoplatform provides an emerging strategy for manipulating BCSCs against tumor progression and metastasis, demonstrating a promising photodynamic platform against tumors.

A Nanoplatform to Amplify Apoptosis-to-Pyroptosis Immunotherapy via Immunomodulation of Myeloid-Derived Suppressor Cells.

Pyroptosis is a programmed cell death to enhance immunogenicity of tumor cells, but pyroptosis-based immunotherapy is limited due to the immune escape involving myeloid-derived suppressor cells (MDSCs). Therefore, designing a nanoplatform to not only trigger apoptosis-pyroptosis transformation but also combat the MDSC-based immune escape is of great significance. As a proof-of-concept study, here, we designed a metal organic framework (MOF)-based nanoplatform to tailor the pyroptosis immunotherapy through disrupting the MDSC-mediated immunosuppression. By pH-responsive zeolitic imidazolate framework-8 (ZIF-8) modified with hyaluronic acid (HA), the chemotherapeutic drug mitoxantrone (MIT) and DNA demethylating agent hydralazine (HYD) were successfully co-encapsulated into ZIF-8 for achieving (M+H)@ZIF/HA nanoparticles. This nanoplatform demonstrated a powerful apoptosis-to-pyroptosis transformation with a potent disruption of MDSC-mediated T cell paralysis via reducing immunosuppressive methylglyoxal by HYD. Overall, our two-pronged nanoplatform (M+H)@ZIF/HA can switch the cold tumor into an arsenal of antigens that stimulate robust immunological responses, while suppressing immune escape, collectively triggering vigorous cytotoxic T cell responses with remarkable tumor elimination and building a long-term immune memory response against metastasis.

Rational design of a minimalist nanoplatform to maximize immunotherapeutic efficacy: Four birds with one stone.

Chemotherapy sometimes can cause potential tumor-specific T-cell-mediated immune response via stimulating immunogenic cell death (ICD). However, such immune response is usually very weak in chemotherapy because of immunosuppressive tumor microenvironment (ITME), substantially nourished by immunosuppressive indoleamine-2,3-dioxygenase (IDO) and myeloid-derived suppressor cells (MDSCs). It is still a challenge to develop a minimalist drug nanoplatform which can stimulate the inherent immunotherapeutic potential in chemotherapy. Herein, a self-sufficient bi-prodrug nanomedicine strategy was reported to realize a minimalist drug nanoplatform for strengthening immunotherapeutic capability in chemotherapy through its self-owned functions. Gemcitabine (GEM) and 1-methyl-tryptophan (1MT) were designed as a bi-prodrug molecule (GEM-1MT), named for the bioactivity reason of both GEM and 1MT. GEM-1MT bi-prodrug molecules could self-assemble into waste-free nanoparticles (NPs) for cancer therapy. Our GEM-1MT NPs can give full scope to the effect of "kill four birds with one stone": (I) the released GEM could kill tumor cells for triggering ICD; (II) the selective MDSC depletion could be induced by the released GEM; (III) the released 1MT could result in IDO inhibition in tumor cells; (IV) the released 1MT could also cause IDO inhibition in MDSCs. Therefore, the GEM-1MT NPs exhibited an enhanced immunotherapy, contributing to the overall therapeutic efficacy of self-combining chemo-immunotherapy. This bi-prodrug nanomedicine strategy provides a new concept for rational design of a minimalist drug nanoplatform with a strengthened overall therapeutic efficacy of chemo-immunotherapy.

Rational Design of a Robust Antibody-like Small-Molecule Inhibitor Nanoplatform for Enhanced Photoimmunotherapy.

Immune checkpoint blockade of the programmed cell death-ligand 1/programmed cell death-1 (PD-L1/PD-1) pathway via an antibody is a potent strategy for T cell remodeling. Nevertheless, the potency of the antibody is partly compromised by its high price, instability, risk of autoimmune disease, and so forth. Small-molecule inhibitors are interesting alternatives to antibodies. However, tumor-specific delivery of small-molecule inhibitors to the target site for boosting the interruption of the PD-L1/PD-1 pathway is rarely reported. Herein, we designed a tumor-specific delivery nanoplatform that could efficiently deliver the small-molecule inhibitor to the precise target site, greatly enhancing the blocking effect of the PD-L1/PD-1 pathway. Hyaluronic acid (HA) was conjugated with chlorin e6 (Ce6), resulting in a HA-Ce6 conjugate (HC). The nanoplatform was constructed by the HC micelles with the encapsulation of small-molecule inhibitor, BMS 202 (BMS), to form BMS/HC micelles. The target property of HA, combined with the hyaluronidase-induced degradation of HA in the tumor site, enables the as-prepared micelles with tumor-specific delivery of BMS for blocking the PD-L1/PD-1 pathway. With cooperative treatment with the photosensitizer Ce6, the present therapeutic nanoplatform demonstrated excellent photoimmunotherapy for tumor regression in distant tumors and lung metastasis. This strategy of tumor-specific delivery of small-molecule inhibitors provides an effective pathway to strengthen the blocking efficacy of PD-L1/PD-1 on effective photoimmunotherapy.

Effect on survival of local treatment in patients with low prostate-specific antigen, high Gleason score prostate cancer: a population-based propensity score-matched analysis.

BACKGROUND: Emerging data suggest that in patients with low prostate-specific antigen (PSA) and high Gleason score, prostate cancer (PCa) is more aggressive and more likely to be related to genomic characteristics of neuroendocrinology. However, the evidence for the advantages of local treatment (LT) for these men is lacking. Hence, we investigated survival in men with low-PSA values and high-grade (Gleason score 8-10) PCa according to the treatment of the primary tumor. METHODS: Kaplan-Meier survival analysis was applied to analyze the effects on overall survival (OS) and cancer-specific survival (CSS) according to the different treatments of the primary tumor. Multivariable Cox proportional hazards survival regression analysis calculated the CSS after propensity score matching (PSM) in 2 cohorts according to treatment type. The treatment types included the following: (I) LT versus non-LT (NLT) and (II) radical prostatectomy (RP) versus radiotherapy (RT). RESULTS: In the Surveillance, Epidemiology, and End Results (SEER) database [2004-2014], we identified 14,208 patients newly diagnosed with low PSA values (10 ng/mL or less), with a Gleason score 8-10, and cT1-4N0M0 prostate adenocarcinoma. After the first PSM, of the 3,512 PCa patients, 1,576 underwent LT and 1,576 underwent NLT. After the second PSM, of the 792 PCa patients, 396 underwent RP, and 396 underwent RT. The 5- and 10-year OS rates for LT vs. NLT patients were 90% and 73% versus 69% and 39%, respectively, while the 5- and 10-year CSS rates for LT vs. NLT patients were 98% and 94% versus 89% and 79%, respectively. Subsequent multivariate survival analysis showed that LT was associated with lower likelihood of PCa mortality relative to NLT [hazard ratio (HR), 0.19; 95% confidence interval (CI), 0.14-0.26, P<0.001], also in RP versus RT (HR, 0.26; 95% CI, 0.12-0.54, P<0.001). CONCLUSIONS: In patients with low PSA values, Gleason score 8-10, and localized PCa, LT resulted in higher survival compared with NLT. Within LT, RP provided the most benefit relative to RT.

Laparoscopic gynecological surgery in an adult woman with Becker muscular dystrophy performed with sevoflurane with cisatracurium anesthesia: A case report.

RATIONALE: Becker muscular dystrophy (BMD) and Duchenne muscular dystrophy (DMD) are progressive neuromuscular disorders caused by mutations in the dystrophin gene. The management of anesthesia in patients with BMD is complicated because they are highly sensitive to the conventional anesthetics such as volatile anesthetics and muscle relaxants. It is reported that anesthesia in patients with DMD is associated with several complications. However, a few case reports have been published on adult patients with BMD undergoing surgery with general anesthesia. Reports indicate that children with BMD may experience some serious complications with flurane-inhaled anesthesia. However, no study has yet shown that the use of flurane-induced anesthesia in adults with DMD carries high risks. PATIENT CONCERNS: We describe a 56-year-old woman with BMD who was scheduled for laparoscopic hysterectomy and bilateral adnexectomy under general anesthesia due to a mass in the uterus. The patient was diagnosed with BMD 20 years back and reported that during this period, she was able to walk slowly with help during her daily life. Additionally, she also had a history of hypertension since 4 years and type 2 diabetes mellitus since 2 years. DIAGNOSIS: The patient was postmenopausal and presented with abnormal uterine bleeding and elevated CA125. Abdominal ultrasonography revealed diffuse enlargement of the uterus and hypoechoic internal echoes. These findings were suggestive of diffuse adenomyosis with multiple uterine leiomyomas, which would have adverse effects later in her life. Therefore, the patient required surgery to address the symptoms and further confirm the diagnosis. The final diagnosis was confirmed by histopathological analysis. INTERVENTIONS: The patient was scheduled for laparoscopic hysterectomy and bilateral adnexectomy. Anesthesia was induced and maintained by a combination of intravenous and inhalation anesthetic agents, particularly cisatracurium besilate and inhaled. sevoflurane. OUTCOMES: The duration of anesthesia and postoperative period were uneventful. At the end of the operation, the patient had normal vital signs and was fully conscious. The patient was followed up for 8 months and no complications were noted during this period. LESSONS: The combination of sevoflurane and cisatracurium besilate is a safe and effective method for the anesthetic management of adult patients with BMD scheduled for laparoscopic gynecological surgery. On the other hand, it is important to be aware of even rare complications of procedures, so that necessary precautions can be undertaken. Further investigations are necessary to determine the safe dosage of volatile anesthetics specifically for this clinical scenario so that anesthesiologists can use this combination method more accurately and precisely.

Long noncoding RNA HOXA-AS2 promotes non-small cell lung cancer progression by regulating miR-520a-3p.

Background: The HOXA cluster antisense RNA 2 (HOXA-AS2) has recently been discovered to be involved in carcinogenesis in multiple cancers. However, the role and underlying mechanism of HOXA-AS2 in non-small cell lung cancer (NSCLC) yet need to be unraveled. Methods: HOXA-AS2 expression in NSCLC tissues and cell lines was detected using quantitative real-time PCR (qRT-PCR). Furthermore, the effects of HOXA-AS2 on NSCLC cell proliferation, apoptosis, migration, and invasion were assessed by MTS, flow cytometry, wound healing and transwell invasion assays, respectively. Starbase2.0 predicted and luciferase reporter and RNA immunoprecipitation (RIP) assays were used to validate the association of HOXA-AS2 and miR-520a-3p in NSCLC cells. Results: Our results revealed that HOXA-AS2 in NSCLC tissues were up-regulated and cell lines, and were associated with poor prognosis and overall survival. Further functional assays demonstrated that HOXA-AS2 knockdown significantly inhibited NSCLC cell proliferation, induced cell apoptosis and suppressed migration and invasion. Starbase2.0 predicted that HOXA-AS2 sponge miR-520a-3p at 3'-UTR, which was confirmed using luciferase reporter and RIP assays. miR-520a-3p expression was inversely correlated with HOXA-AS2 expression in NSCLC tissues. In addition, miR-520a-3p inhibitor attenuated the inhibitory effect of HOXD-AS2-depletion on cell proliferation, migration and invasion of NSCLC cells. Moreover, HOXA-AS2 could regulate HOXD8 and MAP3K2 expression, two known targets of miR-520a-3p in NSCLC. Conclusion: These findings implied that HOXA-AS2 promoted NSCLC progression by regulating miR-520a-3p, suggesting that HOXA-AS2 could serve as a therapeutic target for NSCLC.

α-lipoic acid exerts neuroprotective effects on neuronal cells by upregulating the expression of PCNA via the P53 pathway in neurodegenerative conditions.

Oxidative stress appears to be a central event responsible for the degeneration of dopaminergic neurons in Parkinson's disease (PD). 1-methyl-4­phenyl-1,2,3,6-tetrahydropyridine or its toxic metabolite 1­methyl­4­phenylpyridinium (MPP+) are classical widely­used pharmacological and toxic agents to model PD; they cause the production of reactive oxygen species by inhibiting mitochondrial complex I, leading to DNA oxidative damage and subsequent neuronal death. Previous findings have suggested that proliferating cell nuclear antigen (PCNA), a critical regulatory protein for DNA repair, is involved in dopaminergic neuron damage in the MPP+­induced PD model. The naturally occurring dithiol compound, α­lipoic acid (ALA) has been reported to provide neuroprotection in in vitro models of PD. The molecular mechanism by which ALA reduces neuronal death in PD remains to be fully elucidated. The present study aimed to analyze the ability of ALA to protect neuronal PC12 cells from the toxicity induced by MPP+, and the molecular mechanism underlying these actions using MTT and lactate dehydrogenase cytotoxicity assays, Hoechst 33258 staining and western blot analysis. The results demonstrated that ALA efficiently increased the production of PCNA in MPP+­treated PC12 cells. Accordingly, ALA treatment attenuated MPP+­induced toxicity in the PC12 cells, and reduced cell apoptosis. The increase in the expression levels of PCNA by ALA in the MPP+­treated PC12 cells appeared to be mediated by repression of the p53 protein, as the expression of p53 was increased by MPP+­treatment and reduced by ALA. Taken together, these results indicated that ALA protected dopaminergic neurons against MPP+­induced neurotoxicity through its ability to upregulate the DNA repair protein, PCNA, via the P53 pathway.

Clinicopathological significance of matrix metalloproteinase-7 protein expression in esophageal cancer: a meta-analysis.

BACKGROUND: The MMP-7 basement membrane and extracellular matrix may be essential for tumor invasion and metastasis, and the results presented herein showed a relationship between MMP-7 expression and esophageal cancer (EC). However, its clinicopathological value for EC patients remains inconsistent. To clarify their associations, a meta-analysis of the relevant published literature was conducted. MATERIALS AND METHODS: Databases including PubMed, Embase, Web of Science, Cochrane Library, CISCOM, CINAHL, and Google Scholar were electronically searched. Only those studies analyzing MMP-7 expression in EC patients with regard to series of different demographic variables and clinicopathological stages (TNM stage, differentiation and invasion grade, and lymph-node [LN] metastasis) were eligible for inclusion. Summary odds ratios (ORs) were pooled in accordance with the random-effect model. RESULTS: Fourteen clinical cohort studies (tumor samples =935) were incorporated into the current meta-analysis. Results revealed that increased MMP-7 expression in EC patients was positively correlated to TNM stage III-IV (OR 3.04, 95% confidence interval [CI] 1.43-6.46; P=0.004). Similar connections were also detected in the differentiation grade, invasion grade, and LN metastasis (all P<0.05). Country-stratified analysis yielded significant association of elevated MMP-7 expression with EC in the People's Republic of China (PRC) under both TNM III-IV versus I-II and differentiation low versus high comparisons (TNM stage, OR 2.01, 95% CI 1.55-2.59, P<0.001; differentiation grade, OR 1.32, 95% CI 1.11-1.57, P=0.002). With regard to invasion grade and LN metastasis, significant association was observed in all the experimental subgroups (all P-values [PRC and Japan] were lower than 0.05). CONCLUSION: These data showed an obvious connection between MMP-7 and TNM stages, differentiation grade, invasive grade, and LN metastasis of EC, indicating that overexpression of MMP-7 may be a suitable diagnostic biomarker for variation in EC clinicopathological features.

Distribution characteristics and indicator significance of Dechloranes in multi-matrices at Ny-Ålesund in the Arctic.

In recent years, Dechloranes have been widely detected in the environment around the world. However, understanding and knowledge of Dechloranes in remote regions, such as the Arctic, remain lacking. Therefore, the concentrations of 5 Dechloranes in surface seawater, sediment, soil, moss, and dung collected from Ny-Ålesund in the Arctic were measured with the concentrations 93 pg/L, 342, 325, 1.4, and 258 pg/g, respectively, which were much lower than those in Asian and European regions. The mean ratios of anti-Dechlorane Plus (DP) to total DP (ƒanti) in seawater, sediment, soil, moss, dung, and atmospheric samples were 0.36, 0.21, 0.18, 0.27, 0.66, and 0.43, respectively. Results suggested that the main source of DP in seawater, sediment, soil, and moss was long-range atmospheric transport. However, the ratio identified in dung was different, for which the migration behavior of the organism is probably the main source of DP.

Sulfonamide antibiotics in the Northern Yellow Sea are related to resistant bacteria: implications for antibiotic resistance genes.

Antibiotic resistance gene (ARG) residues and the mode of transmission in marine environments remain unclear. The sulfonamide (SAs) concentrations, different genes and total bacterial abundance in seawater and sediment of the Northern Yellow Sea were analyzed. Results showed the genes sul I and sul II were present at relatively high concentrations in all samples, whereas the gene sul III was detected fewer. The ARGs concentrations in the sediment were 10(3) times higher than those in water, which indicated sediment was essential ARG reservoir. Statistical analysis revealed the total antibiotic concentration was positively correlated with the relative abundance of the gene sul I and sul II. The relative abundances of the gene sul I and the gene sul II were also correlated positively with those of the gene int1. This correlation demonstrated that SAs exerted selective pressure on these ARGs, whereas the gene int1 could be implicated in the propagation of the genes sul I and sul II in marine environments.