MATHEMATICAL MODELING AND BIFURCATION ANALYSIS FOR A BIOLOGICAL MECHANISM OF CANCER DRUG RESISTANCE

Drug resistance is one of the most intractable issues in targeted therapy for cancer diseases.It has also been demonstrated to be related to cancer heterogeneity,which promotes the emergence of treatment-refractory cancer cell populations.Focusing on how cancer cells develop resistance during the encounter with targeted drugs and the immune system,we propose a mathematical model for studying the dynamics of drug resistance in a conjoint heterogeneous tumor-immune setting.We analyze the local geometric properties of the equilibria of the model.Numerical simulations show that the selectively targeted removal of sensitive cancer cells may cause the initially heterogeneous population to become a more resistant population.Moreover,the decline of immune recruitment is a stronger determinant of cancer escape from immune surveillance or targeted therapy than the decay in immune predation strength.Sensitivity analysis of model parameters provides insight into the roles of the immune system combined with targeted therapy in determining treatment outcomes.

Prox1 Suppresses Proliferation and Drug Resistance of Retinoblastoma Cells via Targeting Notch1

Objective Retinoblastoma(RB)is a prevalent type of eye cancer in youngsters.Prospero homeobox 1(Prox1)is a homeobox transcriptional repressor and downstream target of the proneural gene that is relevant in lymphatic,hepatocyte,pancreatic,heart,lens,retinal,and cancer cells.The goal of this study was to investigate the role of Prox1 in RB cell proliferation and drug resistance,as well as to explore the underlying Notch1 mechanism.Methods Human RB cell lines(SO-RB50 and Y79)and a primary human retinal microvascular endothelial cell line(ACBRI-181)were used in this study.The expression of Prox1 and Notch1 mRNA and protein in RB cells was detected using quantitative real time-polymerase chain reaction(RT-qPCR)and Western blotting.Cell proliferation was assessed after Prox1 overexpression using the Cell Counting Kit-8 and the MTS assay.Drug-resistant cell lines(SO-RB50/vincristine)were generated and treated with Prox1 to investigate the role of Prox1 in drug resistance.We employed pcDNA-Notch1 to overexpress Notch1 to confirm the role of Notch1 in the protective function of Prox1.Finally,a xenograft model was constructed to assess the effect of Prox1 on RB in vivo.Results Prox1 was significantly downregulated in RB cells.Overexpression of Prox1 effectively decreased RB cell growth while increasing the sensitivity of drug-resistant cells to vincristine.Notch1 was involved in Prox1’s regulatory effects.Notch1 was identified as a target gene of Prox1,which was found to be upregulated in RB cells and repressed by increased Prox1 expression.When pcDNA-Notch1 was transfected,the effect of Prox1 overexpression on RB was removed.Furthermore,by downregulating Notch1,Prox1 overexpression slowed tumor development and increased vincristine sensitivity in vivo.Conclusion These data show that Prox1 decreased RB cell proliferation and drug resistance by targeting Notch1,implying that Prox1 could be a potential therapeutic target for RB.

Drug resistance mechanisms in cancers:Execution of prosurvival strategies

One of the quintessential challenges in cancer treatment is drug resistance.Several mechanisms of drug resistance have been described to date,and new modes of drug resistance continue to be discovered.The phenomenon of cancer drug resistance is now widespread,with approximately 90% of cancer-related deaths associated with drug resistance.Despite significant advances in the drug discovery process,the emergence of innate and acquired mechanisms of drug resistance has impeded the progress in cancer therapy.Therefore,understanding the mechanisms of drug resistance and the various pathways involved is integral to treatment modalities.In the present review,I discuss the different mechanisms of drug resistance in cancer cells,including DNA damage repair,epithelial to mesenchymal transition,inhibition of cell death,alteration of drug targets,inactivation of drugs,deregulation of cellular energetics,immune evasion,tumor-promoting inflammation,genome instability,and other contributing epigenetic factors.Furthermore,I highlight available treatment options and conclude with future directions.

Inferring Mycobacterium Tuberculosis Drug Resistance and Transmission using Whole-genome Sequencing in a High TB-burden Setting in China

Objective China is among the 30 countries with a high burden of tuberculosis(TB)worldwide,and TB remains a public health concern.Kashgar Prefecture in the southern Xinjiang Autonomous Region is considered as one of the highest TB burden regions in China.However,molecular epidemiological studies of Kashgar are lacking.Methods A population-based retrospective study was conducted using whole-genome sequencing(WGS)to determine the characteristics of drug resistance and the transmission patterns.Results A total of 1,668 isolates collected in 2020 were classified into lineages 2(46.0%),3(27.5%),and 4(26.5%).The drug resistance rates revealed by WGS showed that the top three drugs in terms of the resistance rate were isoniazid(7.4%,124/1,668),streptomycin(6.0%,100/1,668),and rifampicin(3.3%,55/1,668).The rate of rifampicin resistance was 1.8%(23/1,290)in the new cases and 9.4%(32/340)in the previously treated cases.Known resistance mutations were detected more frequently in lineage 2 strains than in lineage 3 or 4 strains,respectively:18.6%vs.8.7 or 9%,P<0.001.The estimated proportion of recent transmissions was 25.9%(432/1,668).Multivariate logistic analyses indicated that sex,age,occupation,lineage,and drug resistance were the risk factors for recent transmission.Despite the low rate of drug resistance,drug-resistant strains had a higher risk of recent transmission than the susceptible strains(adjusted odds ratio,1.414;95%CI,1.023–1.954;P=0.036).Among all patients with drug-resistant tuberculosis(DR-TB),78.4%(171/218)were attributed to the transmission of DR-TB strains.Conclusion Our results suggest that drug-resistant strains are more transmissible than susceptible strains and that transmission is the major driving force of the current DR-TB epidemic in Kashgar.

PHLDA2 reshapes the immune microenvironment and induces drug resistance in hepatocellular carcinoma

Hepatocellular carcinoma(HCC)is a malignancy known for its unfavorable prognosis.The dysregulation of the tumor microenvironment(TME)can affect the sensitivity to immunotherapy or chemotherapy,leading to treatment failure.The elucidation of PHLDA2’s involvement in HCC is imperative,and the clinical value of PHLDA2 is also underestimated.Here,bioinformatics analysis was performed in multiple cohorts to explore the phenotype and mechanism through which PHLDA2 may affect the progression of HCC.Then,the expression and function of PHLDA2 were examined via the qRT-PCR,Western Blot,and MTT assays.Our findings indicate a substantial upregulation of PHLDA2 in HCC,correlated with a poorer prognosis.The methylation levels of PHLDA2 were found to be lower in HCC tissues compared to normal liver tissues.Besides,noteworthy associations were observed between PHLDA2 expression and immune infiltration in HCC.In addition,PHLDA2 upregulation is closely associated with stemness features and immunotherapy or chemotherapy resistance in HCC.In vitro experiments showed that sorafenib or cisplatin significantly up-regulated PHLDA2 mRNA levels,and PHLDA2 knockdown markedly decreased the sensitivity of HCC cells to chemotherapy drugs.Meanwhile,we found that TGF-βinduced the expression of PHLDA2 in vitro.The GSEA and in vitro experiment indicated that PHLDA2 may promote the HCC progression via activating the AKT signaling pathway.Our study revealed the novel role of PHLDA2 as an independent prognostic factor,which plays an essential role in TME remodeling and treatment resistance in HCC.

Deciphering resistancemechanisms and novel strategies to overcome drug resistance in ovarian cancer:a comprehensive review

Ovarian cancer is among the most lethal gynecological cancers,primarily due to the lack of specific symptoms leading to an advanced-stage diagnosis and resistance to chemotherapy.Drug resistance(DR)poses the most significant challenge in treating patients with existing drugs.The Food and Drug Administration(FDA)has recently approved three new therapeutic drugs,including two poly(ADP-ribose)polymerase(PARP)inhibitors(olaparib and niraparib)and one vascular endothelial growth factor(VEGF)inhibitor(bevacizumab)for maintenance therapy.However,resistance to these new drugs has emerged.Therefore,understanding the mechanisms of DR and exploring new approaches to overcome them is crucial for effective management.In this review,we summarize the major molecular mechanisms of DR and discuss novel strategies to combat DR.

Role of targeting ferroptosis as a component of combination therapy in combating drug resistance in colorectal cancer

Colorectal cancer(CRC)is a form of cancer that is often resistant to chemotherapy,targeted therapy,radiotherapy,and immunotherapy due to its genomic instability and inflammatory tumor microenvironment.Ferroptosis,a type of non-apoptotic cell death,is characterized by the accumulation of iron and the oxidation of lipids.Studies have revealed that the levels of reactive oxygen species and glutathione in CRC cells are significantly lower than those in healthy colon cells.Erastin has emerged as a promising candidate for CRC treatment by diminishing stemness and chemoresistance.Moreover,the gut,responsible for regulating iron absorption and release,could influence CRC susceptibility through iron metabolism modulation.Investigation into ferroptosis offers new insights into CRC pathogenesis and clinical management,potentially revolutionizing treatment approaches for therapy-resistant cancers.

Smart drug delivery systems to overcome drug resistance in cancer immunotherapy

Cancer immunotherapy,a therapeutic approach that inhibits tumors by activating or strengthening anti-tumor immunity,is currently an important clinical strategy for cancer treatment;however,tumors can develop drug resistance to immune surveillance,resulting in poor response rates and low therapeutic efficacy.In addition,changes in genes and signaling pathways in tumor cells prevent susceptibility to immunotherapeutic agents.Furthermore,tumors create an immunosuppressive microenvironment via immunosuppressive cells and secrete molecules that hinder immune cell and immune modulator infiltration or induce immune cell malfunction.To address these challenges,smart drug delivery systems(SDDSs)have been developed to overcome tumor cell resistance to immunomodulators,restore or boost immune cell activity,and magnify immune responses.To combat resistance to small molecules and monoclonal antibodies,SDDSs are used to co-deliver numerous therapeutic agents to tumor cells or immunosuppressive cells,thus increasing the drug concentration at the target site and improving efficacy.Herein,we discuss how SDDSs overcome drug resistance during cancer immunotherapy,with a focus on recent SDDS advances in thwarting drug resistance in immunotherapy by combining immunogenic cell death with immunotherapy and reversing the tumor immunosuppressive microenvironment.SDDSs that modulate the interferon signaling pathway and improve the efficacy of cell therapies are also presented.Finally,we discuss potential future SDDS perspectives in overcoming drug resistance in cancer immunotherapy.We believe that this review will contribute to the rational design of SDDSs and development of novel techniques to overcome immunotherapy resistance.

Distribution and Drug Resistance Analysis of 2287 Strains of Pathogenic Bacteria in Children’s Blood Culture

Background: Bloodstream infection is a serious infectious disease. In recent years, the drug resistance of pathogenic bacteria to commonly used anti-infective drugs has been widely concerned, which also makes the treatment of bloodstream infection face severe challenges. Objective: To explore the distribution characteristics of blood culture-positive pathogens and the resistance to antibacterial drugs, so as to provide clinicians with accurate laboratory evidence, so as to guide clinicians to rationally apply antibiotics, improve clinical treatment effects, and reduce the emergence of drug-resistant strains. Methods: From January 2019 to June 2022, 2287 positive blood culture specimens of patients in Guangzhou Women and Children’s Medical Center were retrospectively analyzed, and the proportion of different pathogenic bacteria, the distribution of pathogenic bacteria in different departments, and the multi-drug resistance of different pathogenic bacteria were counted. Results: Among the 2287 blood culture positive samples, 1560 strains (68.20%) of gram-positive bacteria and 727 strains (31.80%) of gram-negative bacteria were strained. The top three departments in the distribution of pathogenic bacteria were pediatric intensive care unit (600 strains), pediatric internal medicine (514 strains), and pediatric emergency comprehensive ward (400 strains). The pathogens with high detection rates were: Staphylococcus epidermidis (24.09%), Staphylococcus humans (23.74%), Escherichia coli (13.21%) and Klebsiella pneumoniae (8.71%). The pathogens with high multi-drug resistance rates were: Streptococcus pneumoniae (93%), Staphylococcus epidermidis (83.76%), Enterobacter cloacae (75.61%) and Staphylococcus humans (62.43%). Conclusion: In our hospital, gram-positive bacteria were the main pathogenic bacteria in the blood culture of children patients. The children’s intensive care unit was the department with the largest distribution of pathogenic bacteria, and the multiple drug resistance rate of Streptococcus pneumoniae was the highest.

HIV-1 Subtype Diversity and Factors Affecting Drug Resistance among Patients with Virologic Failure in Antiretroviral Therapy in Hainan Province,China,2014–2020

Objective This study aimed to determine the HIV-1 subtype distribution and HIV drug resistance(HIVDR)in patients with ART failure from 2014 to 2020 in Hainan,China.Methods A 7-year cross-sectional study was conducted among HIV/AIDS patients with ART failure in Hainan.We used online subtyping tools and the maximum likelihood phylogenetic tree to confirm the HIV subtypes with pol sequences.Drug resistance mutations(DRMs)were analyzed using the Stanford University HIV Drug Resistance Database.Results A total of 307 HIV-infected patients with ART failure were included,and 241 available pol sequences were obtained.Among 241 patients,CRF01_AE accounted for 68.88%,followed by CRF07_BC(17.00%)and eight other subtypes(14.12%).The overall prevalence of HIVDR was 61.41%,and the HIVDR against non-nucleoside reverse transcriptase inhibitors(NNRTIs),nucleotide reverse transcriptase inhibitors(NRTIs),and protease inhibitors(PIs)were 59.75%,45.64%,and 2.49%,respectively.Unemployed patients,hypoimmunity or opportunistic infections in individuals,and samples from 2017 to 2020 increased the odd ratios of HIVDR.Also,HIVDR was less likely to affect female patients.The common DRMs to NNRTIs were K103N(21.99%)and Y181C(20.33%),and M184V(28.21%)and K65R(19.09%)were the main DRMs against NRTIs.Conclusion The present study highlights the HIV-1 subtype diversity in Hainan and the importance of HIVDR surveillance over a long period.

KCNJ15 deficiency promotes drug resistance via affecting the function of lysosomes

The altered lysosomal function can induce drug redistribution which leads to drug resistance and poor prognosis for cancer patients.V-ATPase,an ATP-driven proton pump positioned at lysosomal surfaces,is responsible for maintaining the stability of lysosome.Herein,we reported that the potassium voltage-gated channel subfamily J member 15(KCNJ15)protein,which may bind to V-ATPase,can regulate the function of lysosome.The deficiency of KCNJ15 protein in breast cancer cells led to drug aggregation as well as reduction of drug efficacy.The application of the V-ATPase inhibitor could inhibit the binding between KCNJ15 and V-ATPase,contributing to the amelioration of drug resistance.Clinical data analysis revealed that KCNJ15 deficiency was associated with higher histological grading,advanced stages,more metastases of lymph nodes,and shorter disease free survival of patients with breast cancer.KCNJ15 expression level is positively correlated with a high response rate after receiving neoadjuvant chemotherapy.Moreover,we revealed that the small molecule drug CMA/BAF can reverse drug resistance by disrupting the interaction between KCNJ15 and lysosomes.In conclusion,KCNJ15 could be identified as an underlying indicator for drug resistance and survival of breast cancer,which might guide the choice of therapeutic strategies.

A Pleiotropic Drug Resistance Family Protein Gene Is Required for Rice Growth, Seed Development and Zinc Homeostasis

Zinc(Zn) is an essential mineral element for plant growth and development. Zn deficiency in crops frequently occurs in many types of soils. It is therefore crucial to identify genetic resources linking Zn acquisition traits and development of crops with improved Zn-use efficiency for sustainable crop production. In this study, we functionally identified a rice uncharacterized ABCG(ATP-binding cassette G-subfamily) gene encoding a PDR20(pleiotropic drug resistance 20) metal transporter for mediation of rice growth, seed development and Zn accumulation. OsPDR20 was localized to the plasma membrane, but it was not transcriptionally induced under Zn deficiency, rather was sufficiently up-regulated under high level of Zn stress. Yeast(Saccharomyces cerevisiae) transformed with OsPDR20 displayed a relatively lower Zn accumulation with attenuated cellular growth, suggesting that OsPDR20 had an activity for Zn transport. Knocking-down OsPDR20 by RNA interference(RNAi) compromised rice growth with shorter plant height and decreased biomass in rice plantlets grown under hydroponic media. Zn concentration in the roots of OsPDR20 knocked-down rice lines declined under Zn deficiency, while they remained unchanged compared with the wild type under normal Zn supply. A rice lifelong field trial demonstrated that OsPDR20 mutation impaired the capacity of seed development, with shortened panicle and seed length, compromised spikelet fertility, and reduced grain number per plant or grain weight per unit area. Interestingly, OsPDR20 mutation elevated the accumulation of Zn in husk and brown rice over the wild type. Overall, this study pointed out that OsPDR20 is fundamentally required for rice growth and seed development through Zn transport and homeostasis.

Roles of lncRNAs in pancreatic ductal adenocarcinoma: Diagnosis,treatment, and the development of drug resistance

Background: Pancreatic ductal adenocarcinoma(PDAC) is one of the most lethal cancers, primarily due to its late diagnosis, high propensity to metastasis, and the development of resistance to chemo-/radiotherapy. Accumulating evidence suggests that long non-coding RNAs(lnc RNAs) are intimately involved in the treatment resistance of pancreatic cancer cells via interacting with critical signaling pathways and may serve as potential diagnostic/prognostic markers or therapeutic targets in PDAC. Data sources: We carried out a systematic review on lnc RNAs-based research in the context of pancreatic cancer and presented an overview of the updated information regarding the molecular mechanisms underlying lnc RNAs-modulated pancreatic cancer progression and drug resistance, together with their potential value in diagnosis, prognosis, and treatment of PDAC. Literature mining was performed in Pub Med with the following keywords: long non-coding RNA, pancreatic ductal adenocarcinoma, pancreatic cancer up to January 2022. Publications relevant to the roles of lnc RNAs in diagnosis, prognosis, drug resistance, and therapy of PDAC were collected and systematically reviewed. Results: Lnc RNAs, such as HOTAIR, HOTTIP, and PVT1, play essential roles in regulating pancreatic cancer cell proliferation, invasion, migration, and drug resistance, thus may serve as potential diagnostic/prognostic markers or therapeutic targets in PDAC. They participate in tumorigenesis mainly by targeting mi RNAs, interacting with signaling molecules, and involving in the epithelial-mesenchymal transition process. Conclusions: The functional lnc RNAs play essential roles in pancreatic cancer cell proliferation, invasion, migration, and drug resistance and have potential values in diagnosis, prognostic prediction, and treatment of PDAC.

Advances in drug resistance of triple negative breast cancer caused by pregnane X receptor

Breast cancer is the most common malignancy in women worldwide.Triplenegative breast cancer(TNBC),refers breast cancer negative for estrogen receptor,progesterone receptor and human epidermal growth factor receptor 2,characterized by high drug resistance,high metastasis and high recurrence,treatment of which is a difficult problem in the clinical treatment of breast cancer.In order to better treat TNBC clinically,it is a very urgent task to explore the mechanism of TNBC resistance in basic breast cancer research.Pregnane X receptor(PXR)is a nuclear receptor whose main biological function is to participate in the metabolism,transport and clearance of allobiological agents in PXR.PXR plays an important role in drug metabolism and clearance,and PXR is highly expressed in tumor tissues of TNBC patients,which is related to the prognosis of breast cancer patients.This reviews synthesized the important role of PXR in the process of high drug resistance to TNBC chemotherapeutic drugs and related research progress.

Clinical Distribution and Drug Resistance of Acinetobacter baumannii in a Hospital from 2019 to 2021

Objective:To analyze the clinical distribution and drug resistance of Acinetobacter baumannii(AB)and provide reference for the treatment of AB infection.Methods:AB isolated from clinical specimens of Huaihua First People’s Hospital from 2019 to 2021 were collected and identified by VITEK 2 Compact,an automated microbial identification and susceptibility testing system,in which drug sensitivity test was also performed.Excel was used for statistical analysis.Results:Among the 1,311 AB strains,81.16%(1,064 strains)were from sputum samples,and the departments with the highest detections rates of AB were neurosurgery(24.33%),intensive care(15.48%)and infectious disease(11.44%).The drug sensitivity test showed that the resistance rate of 1,311 AB strains to compound sulfamethoxazole and amikacin was 28.38%and 20.54%,respectively,and the resistance rate to 10 other kinds of common antibiotics was more than 40%.Conclusion:The 1,311 AB strains isolated were widely distributed in clinical settings and had strong resistance to commonly used antibiotics.Therefore,it is necessary to strengthen the monitoring of pathogens and drug resistance,formulate reasonable and effective infection control measures,and ensure that antibiotics are used in a reasonable manner.

Correlative Expression of Glutathion S-Transferase-π and Multidrug Resistance Associated Protein in Bladder Transitional Cell Carcinoma

In order to elucidate the mechanisms of multidrug resistance (MDR) in bladder cancer, the expression of glutathione S-transferase-π (GST-π) and multidrug resistance associated protein (MRP) in tissue samples resected from 44 patients and 6 normal bladder mucosa as control was de- tected by using immunohistochemical method, and the results were analyzed by computer-assisted im- age analyzing system (IAS) to achieve semi-quantitative data. In addition, correlation between the expression of both factors was studied. The results showed that the positive expression rate of GST- π and MRP in bladder cancer was 72. 7 % (32/44) and 68. 2 % (30/44) respectively, significantly higher than those in normal bladder mucosa, being 16. 7% and 33. 3% respectively. The rate of GST-πpositive staining was increased correspondingly with tumor grade and stage elevated, being higher in recurrent tumors treated by chemotherapy, but not significantly (P>0. 05). There was no significant differences between the expression of MRP and tumors' behaviors and clinical characters. However, the results demonstrated that the correlation between the expression of both resistant fac- tors was very evident (r=0. 695, P<0. 0025). It was suggested that the activation of GST-π and MRP might occur during malignant transformation of normal mucosa, but tumors' differentiation and progression could not be the unique factors that influenced both overexpression. Chemotherapy might be another important reason. The correlation of both indicated that there was a common mech- anism regulating their expression probably, which made them play a pivotal role in chemotherapy drug resistance of bladder cancers.

Mechanism of drug resistance and reversal with ligustra-zine and cyclosporin A in cisplatin--inducedhuman epithelial ovarian cancer resistant cell line 3Ao/cDDP

Objective: To investigate the mechanism of resistance and reversal effect of ligustrazine and cyclosporin A in cisplatin--induced multidrug resistance ovarian cancer cell line 3Ao/cDDP. Methods: Using the corresponding dose calculated from clinical chemotherapy at 30 mg cisplatin per cycle, we established 3Ao/cDDP with 3Ao exposed at regular intervals and repeatedly to high-level concentration of cisplatin at 10 mg/ml for 24 hours each time. Expressions of LRP, MRP, P-gp, GSTp and TopoII were quantitatively detected with FCM. For drug resistance reversal, cyclosporin A and ligustrazine were administered singly or in combination at the maximal dose without cytotoxicity. Inhibition rates were determined by MTT assay. Results: 3Ao/cDDP was established after 4.5 months, with resistance factor 1.6 which was similar to clinical resistance degree. Low expression levels of MRP and P-gp were found in both 3Ao and 3Ao/cDDP (P>0.05), and LRP and GSTp expression levels in 3Ao/cDDP were significantly higher than those in 3Ao (P<0.005 and P<0.05, respectively), and TopoII in 3Ao/cDDP was significantly lower vs 3Ao (P<0.05). The inhibition rate of cDDP was 20.807±0.015%, cDDP plus ligustrazine 27.421±0.07% (P>0.05 vs cDDP), cDDP plus cyclosporin A 49.635±0.021% (P<0.01 vs cDDP), and cDDP plus ligustrazine and cyclosporin A 58.861±0.014% (P<0.01 vs cDDP). Conclusions: 3Ao/cDDP, induced by cisplatin and established by imitating the characteristics of clinical chemotherapy for epithelial ovarian cancer, was an ideal model for investigation of cisplatin resistance in vitro. Cisplatin resistance in 3Ao/cDDP could be accounted for by higher LRP, GSTp and lower TopoII expression and was not associated with MRP or P-gp. Ligustrazine had no significant reversal effect on cisplatin resistance, but cyclosporin A could reverse the resistance effectively.

Glycogen Synthase Kinase 3β Inhibitor (2'Z,3'E)-6-Bromo-indirubin-3'-Oxime Enhances Drug Resistance to 5-Fluorouracil Chemotherapy in Colon Cancer Cells

Objective： To explore the effects and mechanism of glycogen synthase kinase 3β （GSK-313） inhibitor （2＇Z,3＇E）-6-bromo-indirubin-3＇-oxime （BIO） on drug resistance in colon cancer cells. Methods： The colon cancer SW480 and SW620 cells were treated with BIO, 5-fluorouracil （5-FU） and BIO/5-FU, separately. Cell cycle distribution, apoptosis level and efflux ability of rhodamine 123 （Rh123） were detected by flow cytometry. The protein expressions of P-glycoprotein （P-gp）, multidrug resistance protein 2 （MRP2）, thymidylate synthase （TS）, β-catenin, E2F-1 and βcl-2 were detected by Western blot. β-catenin and P-gp were stained with double immunofluorescence and observed under a confocal microscope. Results： BIO up-regulated β-catenin, P-gp, MRP2 and TS, enhanced the efflux ability of Rh123, decreased Bcl-2 protein and gave the opposite effect to E2F-1 protein in SW480 and SW620 ceils. Furthermore, BIO significantly inhibited cell apoptosis, increased S and G2/M phase cells, and reduced the cell apoptosis induced by 5-FU in SW480 cells, whereas the effects were slight or not obvious in SW620 cells. Conclusion： GSK-3β was involved in drug resistance regulation, and activation of β-catenin and inhibition of E2F-1 may be the most responsible for the enhancement of 5-FU chemotherapy resistance induced by GSK-β inhibitor β10 in colon cancer.

Reversal of HCC Drug Resistance by Using Hammerhead Ribozymes against Multidrug Resistance 1 Gene

To reverse multidrug resistance（MDR） of HepG2 by anti-MDR1 hammerhead ribozyme, an anti-MDR1 hammerhead ribozyme was developed and delivered to P-gp-overproducing human hepatocarcinoma cell line HepG2 by a retroviral vector containing RNA polymerase Ⅲ promoter. The expression of mdrl/Pgp and Rz was detected in HepG2, HepG2 muhidrug-resistant cell line and HepG2 Rz-transfected cells by semi-quantitative RT-PCR and Western blot methods. Moreover, MTT assay was employed to detect the sensitivity of these ribozyme-transfected cells, and Rhodamine123 （Rh123） was used to test the function of Pgp. The Rz- transfected HepG2 cells became doxorubicin-sensitive, which was concomitant with the decreased MDR1 expression. The study showed that the retrovirus vector encoding the anti-MDR1 ribozyme may be applicable to the treatment of MDR cells.

Expression and Prognostic Significance of Multidrug Resistance Associated Protein (MRP) Gene in Non-small Cell Lung Cancer by in Site Hybridization

Objective: To study on the effect of MRP gene overexpression on prognosis of patients with non-small lung cancer (NSCLC). Methods: Paraffin-embedded tissues from 47 cases of NSCLC who had undergone radical tumor resection were examined for expression of MRP gene mRNA by in situ hybridization using labelled digoxigenin probes combined with immunohistochemistry. All the patients were retrospectively followed-up. Results: All of the 47 lung cancer specimens were found to have overexpression of MRP gene mRNA. It was significantly correlated with patients' survival time, response to chemotherapy, recurrence or metastases after surgery, but was not correlated with histology, tumor size, node status, TNM stage, degree of differentiation, age and sex. Conclusion: Overexpression of MRP gene is a marker of prognostic significance in patients with NSCLC.