4035

LRP1

A2MR|APOER|APR|CD91|IGFBP3R|LRP|TGFBR5;low density lipoprotein receptor-related protein 1;LRP1;low density lipoprotein receptor-related protein 1

LRP-1|TbetaR-V/LRP-1/IGFBP-3 receptor|alpha-2-macroglobulin receptor|apolipoprotein E receptor|prolow-density lipoprotein receptor-related protein 1|type V tgf-beta receptor

12q13-q14

protein-coding

The prognosis of rhabdomyosarcoma (RMS) in advanced stages is still sobering. Therapy is limited due to local tumor recurrence, development of metastases and multidrug resistance. The aim of this study was to investigate the development of multidrug resistance in cell lines and in xenografts of alveolar and embryonal RMS treated according to the German Soft Tissue Sarcoma Study (CWS). Alveolar and embryonal RMS cell lines were treated with Vincristine, Topotecan, Carboplatin, Actinomycin D, or Ifosfamide. expression levels of resistance-associated genes were assessed using Real time-PCR. Nude mice (NMRI nu/nu, n = 10 per group) underwent xenotransplantation of human embryonal or alveolar RMS. Animals were treated with standard chemotherapeutic drugs Vincristine, Topotecan, Carboplatin, Actinomycin D, or Ifosfamide according to treatment schedules of the CWS-study. tumor sizes were measured and relative tumor volumes were calculated. Animals were sacrificed after 20 days and standard histology, Real-time-PCR for MDR1-, MRP-, LRP- and MDM2-gene as well as immunohistochemistry for MDR1-, LRP-, and MRP-protein were performed. In the cell lines, an up-regulation of MDR-1 gene was found in alveolar rhabdomyosarcoma. In embryonal rhabdomyosarcoma, an up-regulation of LRP and MRP was found. Standard chemotherapy of alveolar rhabdomyosarcoma resulted in a significant reduction of tumor growth (P < 0.05) in ALL groups. In embryonal rhabdomyosarcoma strongest effects were found after treatment with Ifosfamide, Vincristine and Carboplatin (P < 0.05). RT-PCR revealed a MDR1-dependent mechanism in alveolar rhabdomyosarcoma. In embryonal rhabdomyosarcoma, MDR1 occurred to a lower degree. Immunohistochemistry revealedcorrelating expression levels of multidrug resistance-associated proteins. The use of established chemotherapy on human RMS in vivo had strong effects on xenografts compared to their controls. In ALL cases, there was only a reduction of tumor growth, but not a complete eradication of the tumors. Chemotherapy seemed to upregulate the expression of resistance-associated genes in vitro and in vivo. The mechanism of multidrug resistance depends on the tumor subtype. Therefore, further investigations will be required to evaluate multidrug resistance in patients and to investigate new modalities for a reversal of multidrug resistance.

OBJECTIVES: To evaluate and compare the profile of expression of genes related to drug resistance in brain tumors and to analyze the impact of the increased expression of these genes on overall survival. METHODS: Eighty microdissected brain tumor samples from 79 patients were analyzed by RQ-PCR for the genes MDR1,MRP1, MRP3, LRP and BCRP. Protein expression was assessed by immunohistochemistry for MRP1 and LRP genes. pediatric cases (0 to 20 years): 46 (17F:29M, median age7.3 +/- 5.9 years); adult tumors: 33 (17F:16M, median age 46.6 +/- 14.5 years). Histological diagnoses: 21 astrocytomas I and II, 28 astrocytomas III and glioblastomas, 17 medulloblastomas, 8 ependymomas, and 6 oligodendrogliomas. RESULTS: glial tumors expressed higher MDR1 (P = 0.003) and BCRP (P = 0.03) levels than embryonic tumors. Low-grade astrocytomas expressed high MDR1 (P = 0.001), MRP3 (P = 0.01) and LRP (P = 0.02) levels. The MRP1 gene was preferentially expressed by medulloblastomas (P = 0.04) and ependymomas (P = 0.04); ependymomas also presented an increase of LRP (P = 0.02). The mRNA levelsof MRP1 and LRP genes were associated to protein expression. The profile of geneexpression of primary pilocytic astrocytomas of the hypothalamus and of the other locations was similar. Increased expression of resistance genes, separately or jointly, was not correlated with shorter overall survival in patients with medulloblastomas/PNET and malignant gliomas. CONCLUSIONS: Drug resistance genes do not explain the higher sensitivity of gliomas of the hypothalamus/pituitary/optic pathways to chemotherapy. The increased expression of resistance genes had no impact on the overall survival of patients with medulloblastomas/PNET and high grade gliomas. High MDR1, MRP3 and LRP levels maybe implicated in the primary resistance of pilocytic astrocytomas to chemotherapy.

Renal cancers are as one of the most common drug resistant neoplasms affecting children and multidrug resistance (MDR) happened to be an important reason for the failure of chemotherapy in refractory cancers of childhood. MDR can be intrinsic or acquired, depending on the time of its occurrence, either at diagnosis or during chemotherapy. Renal cancers often have intrinsic form of MDRbecause of de novo expression of P-glycoprotein (P-gp) in renal cells. Molecularinvestigations on MDR during the past two decades have led to the isolation and characterization of genes coding for P-gp, multidrug resistance-associated protein (MRP), lung resistance-related protein (LRP), breast cancer resistance protein (BCRP/MXR), drug resistance-associated protein (DRP), and ATP-binding cassette protein (ABCP). Several molecular probes, primer pairs, and monoclonal antibodies have been developed over the years to quantify the regulation and expression of these drug resistance markers in tumor cells. Methodologies have also been standardized to estimate the gene amplification, mRNA and protein expression, and functionality of drug resistance proteins in clinical specimens from cancer patients. Because of the recent developments in microarray technology, DNA and protein arrays against drug resistant genes are available commercially now. This review includes techniques for detection and quantification of the expression and function of these drug resistance genes in childhood renal tumors. Since these markers have clinical significance, currently available technology warrants the application of these markers in clinical oncology. Moreover, the first, second and third generation drug resistance modifiers have been developed over the past several years for overcoming drug resistance problem in tumor cells. Unfortunately, these reversing agents are yetto be proved successful clinically. Since treatment protocols are usually adopted from adult tumor patients into childhood population, clinical trials with modifying agents are yet to be undertaken and/or concluded in pediatric renal cancer patients. More clinical studies may be required to analyze the genes involved in the MDR of childhood renal cancer patients and trials have to be undertaken to evaluate the efficacy of MDR modifying agents in them, at least inparallel with adult patients.

The aim of this prospective study was to analyze the expression of messenger RNAof genes, such as MDR1, MRP1, BCRP, and LRP, implicated in the mechanism of multidrug resistance (MDR) in relation to the response to induction chemotherapyand relapse and these genes' correlation with each other and with pretreatment laboratory and clinical characteristics. We prospectively studied 49 children (26 boys and 23 girls) with acute lymphoblastic leukemia (ALL) (median age, 5.5 years; range, 15 months to 12.5 years) who were treated with the BFM95 chemotherapy protocol. We used bone marrow mononuclear cells from 7 healthy children as controls. The expression of MDR genes and the beta-actin housekeeping gene was detected by the reverse transcription-polymerase chain reaction with the appropriate primers. The mean expression of each MDR gene was significantly higher in the patients than in the control group (P < .01). We found statistically significant correlations between MRP1 and LRP expression and between MRP1 or LRP expression and MDR1 expression (P < .05). High expression for the MDR1 gene was found in 18 patients (36.7%), and their prognoses were significantly worse than those with low expression (event-free survival, 55.56% versus 86.67%; P = .03, log-rank test). expression of each of the MDR genes was independent of the initial white blood cell count, immunophenotype, National cancer Institute risk classification, and prednisone response. Interestingly, MDR1 expression was significantly higher at relapse than at diagnosis for 4 sample pairs. Evaluation of MDR1 expression at diagnosis of childhood ALL may contribute to the early identification of patients at risk of treatment failure.