| IntroductionIt has been believed that leukemia is the most common malignant tumor in childhood and influences health and life of children seriously. With the development of chemotherapy, the rates of complete remission and overall survival have been improved evidentially, but treatment - induced secondary drug resistance of tumor cells is a major cause of relapsed disease and therapeutic failure in cancer platients. Several mechanism may account for this phenomenon, and multidrug resistance is a principal mechanism of drug resistance. Usually, increased intracellular drug extusion and decreased drug retention contribute to multidrug resistance. It has been generally reported that overexpression of P - glycoprotein ( P - gp) and multidrug resistance protein ( MRP) correlate with multidrug resistance, effect of treatment and prognosis. Recently, a novel transporter, lung resistance protein was cloned and sequenced by foreign scholar. Transfection and over-pression of LRP confer drug resistance to other drug sensitive cells. Relatively high expression of LRP mRNA is observed in leukemia cases , suggesting a potential role for this new transporter in drug resistance in leukemia.The lung resistence protein( LRP) has been found to be a non-glycoprotein from non - small cell lung carcinoma and its cDNA se-quence displays a single open reading frame of 2688 base pairs coding for an 896 - amino acid protein with a calculated M. of 100K. The LRP gene is located on the short arm of chromson 16, close to the gene encoding MRP and its deduced amino acid sequence displays almost complete identity with the rat major vault protein ( MVP) , suggesting that this protein plays a role in fundamental cell process. They have been found to locolize at nuclear pore complexes and may form central plug. The structure and localization of vaults indicate that they may play a role in nucleocytoplasmic transport. Some research has demonstrated that increased LRP expression could lead to resistance to chemotherapy. Thus, the changes of LRP expression may be used to predict drug resistance and prognosis.Using a reverse transcription polymerase chain reaction ( RT -PCR) assay, we have investigated LRP mRNA levels in mononuclear-cells from 52 samples of 43 children with acute leukemia, to assess the relationship of prior chemotherapy with mRNA levels, and study interlinks among drug resistance mechanism , clinical types and prognosis.Experimental materialsStudy patients: 52 samples of 43 children with newly diagnosed, complete remission and relapse acute leukemia from September, 1999 to May, 2001 in our hospital were involed in our study, they were diagnosed by morphologic, immunologic and chromosomal features. Of the 43 cases, 29cases are male, 14 cases are female, the median age is 8 years old( age from 3 to 14 years old). 28 cases are diagnosed as ALL and 15 cases are diagnosed as AML. 24 samples are obtained atpresentation, 19 samples are at complete remission and 9 samples are at relapse, 5 samples are at presentation and complete remission ,but none of samples are at presentation and relapse. 10 bone marrow samples as a control come from FTP children in my hospitol.Main reagents: Trizol reagent from GIBCO BRL USA is for total RNA isolation . first strand cDNA synthesis kit for reverse transcription , Taq DNA polymerase and primers for PCR were purchased from Sangon corporation in shang haiExperimental methodSamples: Bone marrow samples were collected in 10ml tubes containing heparin as anticoagulant before therapy. Mononuclear cells were separated by Ficoll density gradient centrifugation and cryopre-served at -70 C before use.RNA extraction and reverse transcription: total RNA was isolated using Trizol reagent, following the manufactures instructions, chloroform - extracted and precipitated with isopropanol. Synthesis of single stranded cDNA from 1 ug RNA was performed according to " First strand cDNA synthesis kit" from Fermentas Ltd. RNA and cDNA were stored at -70 C.Polymerase chain react...
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