OBJECTIVETo explore the expression of multidrug resistance gene 1 ( MDR1), glutathione-S-transferases-pi (GST-pi) in osteosarcoma and soft tissue sarcoma tissues from 34 patients and their correlation with chemotherapy resistance.

METHODSMDR1 and GST-pi expressions were analyzed by real-time fluorescence quantitative polymerase chain reaction (FQ-PCR) and flow cytometry (FCM) at mRNA and protein levels, respectively. Chemotherapy sensitivity on adriamycin, cisplatinum, fluorouracil, mitomycin C, dacarbazine, vincristine, methotrexate in tumor tissues were detected by MTT assay.

RESULTSThe nonsensitive rates on adriamycin, cisplatinum, fluorouracil, mitomycin C, dacarbazine, vincristine, methotrexate in tumor tissues were 41.18%, 17.7%, 47.1%, 50.0%, 76.5%, 61.8% and 52.9%, respectively. The expression of P-glycoprotein (P-gp) and GST-pi in tumor tissues was 1.54 and 2.58 (relative fluorescence intensity). Chi2 analysis showed that there was a positive correlation between P-gp expression and drug resistance on ADM, GST-pi expression and resistance on ADM, DDP and MMC (P < 0.05). There was not seen obvious correlation between expression of MDR1, GST-pi and age, gender, pathological type, tumor size in osteosarcoma and soft tissue sarcoma patients (P > 0.05). The expression of GST-pi was increased in patients receiving preoperative chemotherapy. The rate of postoperative recurrence was higher in patients with higher GST-pi expression level than those with lower GST-pi expression level before operation (P < 0.05).

CONCLUSIONIndividual differences exist in chemotherapy sensitivity and expression of MDR1 and GST-pi in osteosarcoma and soft tissue sarcomas patients. Chemotherapy can induce up-regulation of GST-pi protein expression. Primary high expression of GST-pi is the main mechanism of resistance of osteosarcoma and soft tissue sarcomas to chemotherapy and is related to poor prognosis.

ATP-Binding Cassette, Sub-Family B, Member 1 ; biosynthesis ; genetics ; Adolescent ; Adult ; Aged ; Antineoplastic Combined Chemotherapy Protocols ; therapeutic use ; Bone Neoplasms ; drug therapy ; genetics ; metabolism ; Child ; Cisplatin ; therapeutic use ; Doxorubicin ; therapeutic use ; Drug Resistance, Multiple ; Drug Resistance, Neoplasm ; Female ; Flow Cytometry ; Follow-Up Studies ; Glutathione S-Transferase pi ; biosynthesis ; genetics ; Humans ; Male ; Middle Aged ; Mitolactol ; therapeutic use ; Mitomycins ; therapeutic use ; Osteosarcoma ; drug therapy ; genetics ; metabolism ; Prognosis ; RNA, Messenger ; biosynthesis ; genetics ; Reverse Transcriptase Polymerase Chain Reaction ; methods ; Sarcoma ; drug therapy ; genetics ; metabolism

BACKGROUNDBoth survivin and lung resistance related protein (LRP) are related to the chemoresistances in hepatocellular carcinoma (HCC). But the relationship between survivin and LRP is indefinite. The aim of this study was to investigate the effects of down-regulation of survivin on LRP expressions and the reversal of chemoresistances in HCC both in vitro and in vivo.

METHODSThe expressions of survivin were detected by RT-PCR and Western blotting in HCC cell line SMMC-7721 and SMMC-7721/ADM. The sensitivities of these two cell lines to ADM were evaluated by MTT assays. SiRNA which targeted survivin was transfected into SMMC-7721/ADM cells, then the sensitivity of SMMC-7721/ADM cells to ADM and the expressions of survivin and LRP were detected respectively. SMMC-7721/ADM cells were transplanted subcutaneously into nude mice to establish xenograft tumors. Antitumor activities of RNA interference (RNAi) targeting survivin, various doses of ADM and combination therapies were observed respectively. Possible toxicities were evaluated. LRP expression changes were tested. Student's t test was used for evaluating statistical significance.

RESULTSThe expressions of survivin in SMMC-7721/ADM cell line showed significant elevation compared to those in SMMC-7721 cell line (P < 0.05). Positive siRNA down-regulated the expressions of survivin significantly (P < 0.05). SiRNA targeting survivin could sensitize SMMC-7721/ADM cells to ADM and down-regulate the expressions of LRP significantly (P < 0.05). Growths of the tumors were significantly inhibited in positive siRNA group as compared with those in the control group from the 8th day (P < 0.05). Combination therapies caused significant tumor inhibitions compared with tumors of nude mice in the other three groups respectively (P < 0.05). No toxicities were found in nude mice treated by siRNA and combination therapies. The expressions of LRP were markedly reduced in tumors treated with siRNA targeting survivin (P < 0.05).

CONCLUSIONSDown regulation of survivin gene by RNAi can increase chemosensitivity of HCC both in vitro and in vivo. The reversal of drug resistance may be reduced through the inhibitions of LRP.

Animals ; Antineoplastic Combined Chemotherapy Protocols ; therapeutic use ; Blotting, Western ; Carcinoma, Hepatocellular ; drug therapy ; genetics ; metabolism ; Cell Line, Tumor ; Doxorubicin ; therapeutic use ; Drug Resistance, Neoplasm ; Humans ; Inhibitor of Apoptosis Proteins ; Mice ; Mice, Inbred BALB C ; Mice, Nude ; Microtubule-Associated Proteins ; genetics ; metabolism ; Mitolactol ; therapeutic use ; Mitomycins ; therapeutic use ; RNA Interference ; physiology ; RNA, Small Interfering ; genetics ; physiology ; Reverse Transcriptase Polymerase Chain Reaction ; Vault Ribonucleoprotein Particles ; genetics ; metabolism ; Xenograft Model Antitumor Assays