Expression Of LRP Research Articles

Activity of lipoplatin in tumor and in normal cells in vitro

Lipoplatin is a novel liposomal cisplatin formulation with reduced adverse side effects compared with its parental compound, cisplatin. The aims of this preclinical study were to compare lipoplatin and cisplatin cytotoxicity in vitro in established cell lines derived from non-small cell lung cancer, renal cell carcinoma, and in normal hematopoietic cell precursors, and to identify biological markers associated with sensitivity and resistance. Our results showed a superior cytotoxicity in all tumor cell models and a much lower toxicity in normal cells for lipoplatin compared with cisplatin, suggesting a higher therapeutic index for the liposomal compound. Moreover, RT-PCR analysis of molecular markers known to be related to cisplatin resistance showed a direct correlation between cisplatin and lipoplatin resistance and ERCC1 and LRP expression. In conclusion, lipoplatin showed a higher antitumor activity in both tumor histotypes investigated and was found to be safer than the parent compound, cisplatin. Moreover, ERCC1 and LRP expression levels would seem to be valid predictors of sensitivity or resistance to these drugs.

EXPRESSION OF MULTIDRUG RESISTANCE-RELATED PROTEIN (MRP-1), LUNG RESISTANCE-RELATED PROTEIN (LRP) AND TOPOISOMERASE-II (TOPO-II) IN WILMS' TUMOR: IMMUNOHISTOCHEMICAL STUDY USING TMA METHODOLOGY

MRP-1, LRP and TOPO-II are all associated with protection of the cells from the adverse effects of various chemotherapeutics. The aim of this study was to measure the expression of these proteins in Wilms' tumor (WT). TMA block was constructed from 14 samples of WT's and from xenografts derived from them. Sections of the TMA were used for immunostaining against MRP-1, LRP and TOPO-IIa. All normal kidneys expressed MRP-1 but were either weakly or negatively stained for LRP and TOPO-IIa. In WT samples, MRP-1 was universally expressed, exclusively in the tubular component, while there was no expression of LRP and TOPO-IIa showed heterogeneous distribution. The xenografts varied in their MRP-1 and TOPO-IIa expression and exhibited weak/negative staining of LRP. This study shows that although all the proteins evaluated, had different expression patterns in the tumor samples, the most prominent changes in expression were found for MRP-1. The exact clinical implications of these changes in expression and their relevance to the resistance of these tumors to chemotherapy requires further investigation. The finding of different expression profiles for the multidrug resistance proteins in the original WT's and their xenografts suggests that the results of animal cancer models may be difficult to interpret.

Pharmacological effects of serum containing chinese medicine Bushen Huayu Jiedu Compound Recipe (补肾化瘀解毒复方) in lung cancer drug-resistance cells

To explore the pharmacologic effects of Chinese medicine Bushen Huayu Jiedu Compound Recipe (BSHYJDR) in drug-resistance cells of lung cancer. Human lung adenocarcinoma A549/DDP cell strain was selected, serum pharmacology and flow cytometer (FCM) method were adopted, S180 tumor-bearing mice and normal mice were given, through gastrogavage, different doses of a decocted concentration of BSHYJDR. Serum from the abdominal aorta was taken to observe the effect of drug-serum on cisplatin (DDP) concentration, free Ca2+ concentration and the expression of lung drug-resistance protein LRP-56 in A549/DDP cells. Compared with the drug-resistance group, the intracellular DDP concentration in the group taking a high dose and the normal group of Chinese medicine showed significant difference (P<0.05), while no significant difference was found in the low-dose group (P>0.05). Compared with the drug-resistance group, the Ca2+ concentration in cells and the expression of LRP in lung cancer drug-resistance cells A549/DDP of the high-dose group, the low-dose group and the normal group of Chinese medicine were significantly different (all P<0.01), the LRP expression of the normal group was obviously higher than that of the drug-resistance group (P<0.05). It was indicated that serum containing Chinese medicine BSHYJDR in the tumor-bearing mice and the normal mice had certainly different, tumor-bearing mice serum containing could improve drug concentration in lung cancer drug-resistance cells, prevent the inflow and release of Ca2+, and inhibit the expression of the drug-resistance gene in the lung cancer drug-resistance cells, which might be the mechanism of BSHYJDR in enhancing the efficacy in reversing and inhibiting tumor.

Determination of P‐glycoprotein, MDR‐related protein 1, breast cancer resistance protein, and lung‐resistance protein expression in leukemic stem cells of acute myeloid leukemia

The most primitive leukemic precursor in acute myeloid leukemia (AML) is thought to be the leukemic stem cell (LSC), which retains the properties of self-renewal and high proliferative capacity and quiescence of the hematopoietic stem cell. LSC seems to be immunophenotypically distinct and more resistant to chemotherapy than the more committed blasts. Considering that the multidrug resistance (MDR) constitutive expression may be a barrier to therapy in AML, we have investigated whether various MDR transporters were differentially expressed at the protein level by different leukemic subsets. The relative expression of the drug-efflux pumps P-gp, MRP, LRP, and BCRP was evaluated by mean fluorescence index (MFI) and the Kolmogorov-Smirnov analysis (D values) in five leukemic subpopulations: CD34+CD38-CD123+ (LSCs), CD34+CD38+CD123-, CD34+CD38+CD123+, CD34+CD38+CD123-, and CD34- mature cells in 26 bone marrow samples of CD34+ AML cases. : The comparison between the two more immature subsets (LSC versus CD34+CD38-CD123- cells) revealed a higher P-gp, MRP, and LRP expression in LSCs. The comparative analysis between LSCs and subsets of intermediate maturation (CD34+CD38+) demonstrated the higher BCRP expression in the LSCs. In addition, P-gp expression was also significantly higher in the LSC compared to CD34+CD38+CD123- subpopulation. Finally, the comparative analysis between LSC and the most mature subset (CD34-) revealed higher MRP and LRP and lower P-gp expression in the LSCs. Considering the cellular heterogeneity of AML, the higher MDR transporters expression at the most immature, self-renewable, and quiescent LSC population reinforces that MDR is one of the mechanisms responsible for treatment failure.

Detection of drug-resistance genes using single bronchoscopy biopsy specimens

Expression of three major resistance genes MDR1, MRP1 and LRP was investigated in small cell lung cancer, non-small cell lung cancer and metastasis. Single biopsies of bronchoscopy from 73 patients were performed to investigate expression of these three resistance genes by reverse transcriptase-polymerase chain reaction. Relations between gene expression and patient age, smoking status, histology, and chemotherapy were evaluated. A more frequent expression of MDR1 (77 versus 66%), MRP1 (91 versus 72%) and LRP (77 versus 63%) genes was detected in the malignant biopsies than in the non-malignant, respectively. In the metastasis biopsies, expression of these genes was markedly increased. No significant difference was observed between specimens before and after chemotherapy. Biopsies from progressing cancer showed higher MDR1, MRP1 and LRP gene expression. In conclusion, these data reveal a major role of MRP1 in intrinsic resistance and the high gene expression of MDR1 and MRP1 in relapsed diseases.

Predictive value of multidrug resistance proteins and cellular drug resistance in childhood relapsed acute lymphoblastic leukemia

Cellular resistance in childhood acute leukemias might be related to profile and function of multidrug resistance proteins and apoptosis regulating proteins. The aims of the study were: (1) analysis of expression of MRP1, PGP1, LRP, BCL-2 and p53 proteins; (2) correlation with ex vivo drug resistance, and (3) analysis of their prognostic impact on clinical outcome in childhood acute lymphoblastic (ALL) and acute myeloid (AML) leukemia. Total number of 787 children diagnosed for initial ALL (n = 527), relapsed ALL (n = 104), initial AML (n = 133) and relapsed AML (n = 23) were included into the study. Mean follow-up period was 3.5 years. Drug resistance for up to 30 anticancer agents was performed by the MTT assay. Expression of all proteins was tested by flow cytometry. Both initial AML and relapsed ALL samples showed higher drug resistance than initial ALL samples. No significant differences were found in drug resistance between initial and relapsed AML samples. The presence of multidrug resistance and apoptosis proteins had no impact on pDFS in iALL and iAML, however strong trend towards adverse prognostic impact of MRP1, PGP and LRP on pDFS in rALL was observed. The same trend was observed for each of analyzed co-expressions of tested multidrug resistance proteins. The phenomenon of cellular drug resistance in childhood acute leukemias is multifactorial and plays an important role in response to therapy. Expression of MRP1, PGP and LRP proteins, as well as their co-expression play possible role in childhood relapsed ALL.

Prognostic implications of the nuclear localization of Y‐box‐binding protein‐1 and CXCR4 expression in ovarian cancer: Their correlation with activated Akt, LRP/MVP and P‐glycoprotein expression

The nuclear localization of Y-box-binding protein-1 (YB-1) is known to be a poor prognostic factor in several human malignancies, including ovarian carcinoma. Following on from our basic study dealing with microarray analyses of YB-1-associated gene expression in ovarian cancer cells, we examined whether nuclear localization of YB-1 is associated with the expression of CXCR4, a vault protein named lung resistance-related vault protein (LRP/MVP), phosphorylated Akt (p-Akt) or P-glycoprotein (P-gp) in human ovarian carcinoma. Fifty-three surgically resected ovarian carcinomas treated with paclitaxel and carboplatin were examined immunohistochemically for nuclear YB-1 expression and intrinsic expression of p-Akt, P-gp, LRP/MVP and CXCR4. Nuclear expression of YB-1 demonstrated significant correlation with p-Akt, P-gp and LRP expression, but no relationship with CXCR4 expression. By multivariate analysis, only YB-1 nuclear expression and CXCR4 expression were independent prognostic factors with regard to overall survival. These results indicate that YB-1 nuclear expression and CXCR4 expression are important prognostic factors in ovarian carcinoma.

P3-247: Functional consequences of LRP expression on familiar Alzheimer disease APP mutations

P3-247: Functional consequences of LRP expression on familiar Alzheimer disease APP mutations

Expresión de proteínas relacionadas con resistencia a múltiples drogas (MDR-proteínas) y resistencia a la quimioterapia en el cáncer de pulmón

Purpose: To evaluate the expression of MDR-proteins in the response to lung cancer chemotherapy. Methods: 147 tumor samples were collected from 143 patients, 35 of which were obtained by bronchoscopy and 112 from surgery; 101 samples belonging to 99 patients were considered valid for the study. The samples were cryopreserved and immunochemistry with monoclonal murine antibodies used to determine the MDR-proteins Pgp, Mrp1 and Lrp. Results: No MDR-proteins were expressed in 16 cases. One MDR-protein was present in 32 cases: Pgp in 3, Mrp1 in 11 and Lrp in 18. Two MDR-proteins were expressed in 34 cases: Pgp and Lrp in 24, Mrp1 and Pgp in 5, and Mrp and Lrp in 5. All the three MDR-proteins were present in 17 cases. No differences were observed considering age (Pgp, p = 0.74; Mrp1, p = 0.95; Lrp, p = 0.26). Neither sex produced changes when considering either number of MDR-proteins (p = 0.55) or types of them (p = 0.21). Significant differences of MRD-proteins were also lacking for number (p = 0.59) and type (p = 0.51) in relation to the tumer histologic grade. The tendency to the simultaneous expression of Pgp and Lrp was very significant (p < 0.01), while the simultaneous expression of Mrp1 and Lrp showed to be no significant (p = 0.26). Conclussions: Pgp and Lrp are frequently expressed simultaneously. Only the expression of Pgp and the number of MDR-proteins expressed simultaneously seem to be related to response to chemotherapy.

The role of lung resistance protein in radiation treated head and neck carcinoma

Objectives. Vault proteins are ribonucleotide proteins composed largely of a single large protein termed major vault protein. (MVP) The (MVP) LRP gene is located on chromosome 16 close to the genes coding for multidrug resistance‐associated protein and protein kinase c‐β. The role of MVP (LRP) in cancer drug resistance has been demonstrated in various cell lines as well as in ovarian carcinomas and acute myeloid leukaemia, however little is known about its possible role in radiation resistance.1,2 Our aim was to examine this in head and neck squamous carcinoma (HNSCC). Method. One hundred and thirty three patients with proven squamous cell carcinoma of the oropharynx were recruited into the study, looking at two subsites of posterior tongue and tonsil. These patients received primary radiotherapy with curative intent. Archived biopsy material was obtained for 78 patients. Immunohistochemistry was used to detect LRP expression. Locoregional failure and cancer specific survival were estimated using Kaplan Meier method. Results. On analysis of the whole group together LRP expression was strongly associated with locoregional failure (P &lt; 0.0001) however, on subgroup analysis there was an obvious difference between the two sites, with increased LRP expression being associated with poor prognosis in the tongue group (P &lt; 0.0001), but not the tonsil group. (P = 0.14). Conclusion. This is the first reported study of LRP as a prognostic marker in radiotherapy treated HNSCC suggesting it may play an important role not just in cancer drug resistance but also in radiation resistance. Of added interest is the difference in prognostic significance between the two subsites. References 1 Scheffer G.L., Wijngaard P.L., Flens M.J., et al. (1995) The drug resistance‐related protein LRP is the human major vault protein. Nature Med.1, 578–5822 Kozlov G., Vavelyuk O., Ovidiu M., et al. (2005) Solution structure of a two‐repeat fragment of major vault protein. J. Mol. Biol.7

Induced Resistance in the Human Non Small Cell Lung Carcinoma (NCI-H460) Cell Line In Vitro by Anticancer Drugs

Exposure of human non-small cell lung cancer cells (NCI-H460) to gradually increasing concentrations of doxorubicin resulted in the appearance of a new cell line (NCI-H460/R) that was resistant to doxorubicin (96.2-fold) and cross-resistant to etoposide, paclitaxel, vinblastine and epirubicin. Slight cross-resistance to two MDR-unrelated drugs 8-Cl-cAMP and sulfinosine was observed. Flow cytometry analysis showed that the accumulation of doxorubicin in the resistant cells was 88.4% lower than in the parental cells. Also, verapamil significantly decreased the efflux rate in NCI-H460 and NCI-H460/R cells, whereas curcumin inhibited the efflux in NCI-H460 cells only. Gene expression data confirmed the induction of mdr1 (P-gp), as judged by the observed 15-fold increase in its mRNA concentration in doxorubicin-resistant NCI-H460/R cells. In contrast, mrp1 and lrp expression was unaffected by the doxorubicin resistance. Further work should develop a rationale for a novel treatment of NSCLC with appropriate modulators of resistance aimed at improving the outcome of the acquired drug resistance.

Expresión de proteínas relacionadas con resistencia a múltiples fármacos en el cáncer de pulmón

Reduction of intracellular drug accumulation plays an important role in resistance to chemotherapy in neoplasms. MDR-proteins regulate this cell activity. A total of 147 tumor samples were collected from 143 patients. Thirty-five samples were obtained by bronchoscopy and 112 were surgical specimens. One hundred and one samples from 99 patients were valid for the study. The samples underwent cryopreservation and immunohistochemistry for detection of three multiple-drug resistant proteins (MDR-proteins): Pgp, Mrp1 and Lrp. No proteins were expressed in 16 patients. A single protein was expressed in 32 patients: 3 Pgp, 11 Mrp1 and 18 Lrp=0. Two proteins were expressed in 34 patients: 24 Pgp and Lrp, 5 Mrp1 and Pgp, 5 Mrp1 and Lrp=0. All three proteins were expressed in 17 patients. No differences were observed in expression according to age (Pgp [p=0.74], Mrp1 [p=0.95], Lrp [p=0.26]). No differences were found according to sex, when both the number (p=0.72) and type (p=0.39) of simultaneously expressed proteins were analyzed. No differences were observed according to tumoral stage [number (p=0.55), type (p=0.21)] or histological grade [number (p=0.59), type (p=0.51)]. The tendency toward simultaneous expression of Pgp and Lrp was highly significant (p<0.01). The same tendency was not observed in the association between Mrp1 and Lrp (p=0.26). MDR-proteins are frequently expressed in lung cancer. Of the three MDR-proteins studied, Lrp was the most frequent. Adenocarcinoma expressed less Mrp1 than other histological types. Squamous carcinoma expressed less Lrp than adenocarcinomas and large-cell undifferentiated carcinomas. In a considerable number of patients, more than two proteins were expressed simultaneously. Squamous-cell carcinomas tended to express Pgp, Mrp1 and Lrp simultaneously. Pgp was usually expressed in association with Lrp.

Expression of lung resistance-related protein, LRP, and multidrug resistance-related protein, MRP1, in normal human lung cells in long-term cultures

Transport processes form part of the body's defense mechanism, and they determine the intracellular levels of many endogenous and exogenous compounds. The multidrug resistance-related protein MRP1 and the lung resistance-related protein LRP are associated with drug resistance against chemotherapeutics; they protect cells against toxic compounds. There is much experimental evidence to suggest that both of these transporter proteins serve important physiological functions. The expression of LRP and MRP1 was studied in normal human bronchial epithelial cells (NHBEC) and peripheral lung cells (PLC) obtained from explant cultures from morphologically-normal human lung tissue taken from patients with lung cancer. LRP (mRNA and protein) was detected in the cells of the bronchi as well as the peripheral lung with low (a factor of 2.6) inter-individual variation in the first generation. No significant alterations were noted for LRP within three-to-four generations in the same patient. LRP expression was not substantially different between cultures from different topographic regions of the human lung. MRP1 protein and MRP1 mRNA could also be detected in all of the NHBEC and PLC cultures studied, but with substantially higher (a factor of 7.7) intra-individual variation in the first generation than for LRP. MRP expression was the same for bronchial cells and PLC when the material was obtained from both sites. The level of mRNA for MRP1 was, in general, less stable than that for LRP. In multigeneration explant cultures, the levels of LRP mRNA and protein and MRP1 protein did not fluctuate greatly, but the level of MRP1 mRNA dropped to about 25% of the reference value within four generations (after about 8-10 weeks of culture). In one case, NHBEC subpassages were followed over a period of 20 weeks. In this system MRP mRNA levels increased by more than threefold, while levels of MRP1 protein and LRP mRNA and protein were expressed at almost constant rates.

MDR1 and MRP1 gene expression are independent predictors for treatment outcome in adult acute myeloid leukaemia

Multi drug resistance (MDR) is a major obstacle for cancer therapy. The three major candidates accounting for the development of MDR in acute myeloid leukaemia (AML) are multi drug resistance gene (MDR1), multi drug resistance-related protein gene (MRP1) and lung resistance protein gene (LRP). So far, the differential impact of resistance gene expression on treatment outcome in AML is not clear. Therefore, we examined MDR1, MRP1 and LRP gene expression at diagnosis in 331 adult AML patients in the context of other known prognostic factors, such as age, disease status, cytogenetics and FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication mutational status. Median observation time was longer than 5 years [64.1 months (40.0-87.6)]. MDR1 expression proved to be an independent prognostic factor for outcome of induction therapy (P <0.001) and overall survival (P=0.02), whereas MRP1 expression was an independent predictor for disease-free survival (P=0.01) in the multivariate analysis. This prognostic impact of both resistance genes was also found in patients with intermediate risk cytogenetics. LRP expression, however, had no impact on treatment outcome in AML. Our study shows that resistance gene expression should be considered together with age, cytogenetics and FLT3 mutational status for risk-adapted treatment strategies in AML in the future.

Upregulation of hepatic LDL receptor-related protein in nephrotic syndrome: response to statin therapy

Nephrotic syndrome (N-S) is associated with elevated plasma concentration and impaired clearance of VLDL, chylomicrons (CM), and their atherogenic remnants. These abnormalities are largely due to lipoprotein lipase, hepatic triglyceride lipase, and VLDL receptor deficiencies and impaired HDL-mediated shuttling of apoE and apoC between the nascent and remnant VLDL and CM. LRP is a multifaceted endocytic receptor that is heavily expressed in the liver. LRP recognizes at least 30 different ligands including VLDL and CM remnants. These observations prompted the present study to discern the effect of N-S on hepatic LRP gene and protein expressions. The study further sought to explore the effect of lipid-lowering therapy on LRP expression in N-S. Sprague-Dawley rats were randomized to the N-S (given ip injections of puromycin aminonucleoside; 130 mg/kg on day 1, 60 mg/kg on day 14) and placebo-injected control groups. On day 14, animals were subdivided into statin-treated (rosuvastatin; 20 mg x kg(-1) x day(-1) mixed with powdered chow) and untreated groups and studied on day 28. The untreated N-S group exhibited severe proteinuria, hypoalbuminemia, hypercholesterolemia, hypertriglyceridemia, and marked elevation of hepatic tissue LRP mRNA and protein abundance. Statin administration for 2 wk resulted in significant improvements of plasma lipid profile, proteinuria, and hypoalbuminemia as well as hepatic LRP mRNA and protein abundance. In contrast, statin administration had no significant effect on either plasma lipids or hepatic LRP levels in the normal control rats. In conclusion, N-S results in marked upregulation of hepatic LRP expression that is partly reversed with statin administration. These findings exclude depressed hepatic LRP expression as the primary cause of elevated plasma lipoprotein remnants in N-S.

Effect of lung resistance-related protein on the resistance to cisplatin in human ovarian cancer cell lines

The mechanisms of drug-resistance in human ovarian cancer cells have not been entirely clarified. The purpose of this study was to investigate whether LRP is involved in the resistance of ovarian cancer cell lines to cisplatin and its molecular mechanism. Human ovarian cisplatin-resistant cancer cell lines (A2780/DDP and COC1/DDP) and their parental cisplatin-sensitive cell lines (A2780 and COC1), alone or transfected with antisense LRP-specific oligonucleotides (ODN) or sense ODN, were treated with cisplatin to induce differentiation. Expression of LRP was examined by RT-PCR and Western blot analysis. The sensitivities of cells to cisplatin were assessed using sulforhodamine B (SRB) assay and flow cytometry, and the accumulation and efflux of cisplatin in the cells and isolated nuclei were examined by high performance liquid chromatographic (HPLC) assay. The expressions of LRP in A2780/DDP and COC1/DDP cells were higher than those in A2780 and COC1 cells and conferred resistance to cisplatin. Transfection of LRP AsODN into A2780/DDP and COC1/DDP cells down-regulated LRP expression and reversed the resistance phenotype. Levels of cisplatin accumulating in cells were increased by LRP-specific AsODN and anti-LRP monoclonal antibody. Isolated nuclei from A2780 and COC1 cells or A2780/DDP and COC1/DDP cells incubated with anti-LRP antibody contained more cisplatin than the nuclei of A2780/DDP and COC1/DDP cells not treated with anti-LRP antibody. Efflux of cisplatin was greater from the nuclei of A2780/DDP and COC1/DDP cells than those of A2780 and COC1 cells, and was inhibited by anti-LRP monoclonal antibody. Thus, LRP was involved in the resistance of ovarian cancer cells to cisplatin and has an important role in the transport of cisplatin both in exocytotic vesicles and between the nucleus and cytoplasm.

Apoptotic and Multi-Drug Resistance Profile in Elderly AML Patients.

Elderly AML patients have an unfavorable prognosis with frequent resistance of leukemic cells to chemotherapy. The expression of proteins related with apoptosis and multi-drug resistance have been involved in chemotherapeutic resistance in AML; however, these proteins are not only expressed on leukemic but also on normal cells. Moreover, within leukemic cells, different stages of maturation may occur. The aim of the present study was to evaluate the expression of proteins related to apoptosis (APO 2.7, bax, and bcl-2), and drug resistance (P-gp, MRP, LRP) in a series of 117 elderly AML patients (median age of 70) uniformly treated according with the Spanish Pethema cooperative group protocol (LMA >65). 63 patients (54%) achieved complete remission (CR), with a median relapse free survival (RFS) of 9.2 months. In the bone marrow (BM) pre-treatment, we performed a four-color staining technique (APO2.7, bax or bcl-2 with CD32/CD34/CD45; and P-gp, MRP, or LRP with CD34/CD19/CD33), allowing the identification of myeloid blast cells, and the discrimination between stages of maturation of blast cell subsets. Samples were acquired on a FACSCalibur flow cytometer (Becton/Dickinson), and appropriate controls were used in each individual sample and, accordingly, antigen expression in individual cell samples was quantified as relative fluorescence intensity (RFI) (ratio blast cell/control mean channel fluorescence value). Our results showed that the level of expression of MRP and LRP was significantly higher (mean±SD of MFI 2.0±0.75 vs 2.7±1.87 and 4.5±2.2 vs 7.0±6.2, respectively -p <0.03-) in cases that did not achieved CR with one or two cycles of chemotherapy. Although different patterns of expression of apoptosis or drug resistance-associated proteins were detected according with the stage of maturation on myeloid blast cells, we did't found any other correlation between levels of bcl-2, bax, APO 2.7, bcl-2/bax ratio or MDR and probability of achieving morphological CR. In addition, CD34 expression on blast cells had also significant influence on response (CR was achieved in 81% of CD34 negative cases vs only 46% of CD34 positive cases; p= 0.005). We didn't found any influence of apoptosis and/or drug-resistance proteins expression in relapse rate nor RFS. Variables influencing RFS were age (p=0.04), and number of cycles to achieve CR (p=0.01); while only WBC count (p=0.05) influenced overall survival (OS). We conclude that MRP and LRP could have a role in the resistance to induction treatment in elderly AML patients but not in RFS or OS.

Wnt signals across the plasma membrane to activate the beta-catenin pathway by forming oligomers containing its receptors, Frizzled and LRP.

Wnt-induced signaling via beta-catenin plays crucial roles in animal development and tumorigenesis. Both a seven-transmembrane protein in the Frizzled family and a single transmembrane protein in the LRP family (LDL-receptor-related protein 5/6 or Arrow) are essential for efficiently transducing a signal from Wnt, an extracellular ligand, to an intracellular pathway that stabilizes beta-catenin by interfering with its rate of destruction. However, the molecular mechanism by which these two types of membrane receptors synergize to transmit the Wnt signal is not known. We have used mutant and chimeric forms of Frizzled, LRP and Wnt proteins, small inhibitory RNAs, and assays for beta-catenin-mediated signaling and protein localization in Drosophila S2 cells and mammalian 293 cells to study transmission of a Wnt signal across the plasma membrane. Our findings are consistent with a mechanism by which Wnt protein binds to the extracellular domains of both LRP and Frizzled receptors, forming membrane-associated hetero-oligomers that interact with both Disheveled (via the intracellular portions of Frizzled) and Axin (via the intracellular domain of LRP). This model takes into account several observations reported here: the identification of intracellular residues of Frizzled required for beta-catenin signaling and for recruitment of Dvl to the plasma membrane; evidence that Wnt3A binds to the ectodomains of LRP and Frizzled; and demonstrations that a requirement for Wnt ligand can be abrogated by chimeric receptors that allow formation of Frizzled-LRP hetero-oligomers. In addition, the beta-catenin signaling mediated by ectopic expression of LRP is not dependent on Disheveled or Wnt, but can also be augmented by oligomerization of LRP receptors.

Expression of Multidrug Resistance Proteins in Rat and Human Chronic Pancreatitis

The expression of the ABC-transporters MDR-1, MRP1, and MRP-2 was investigated in healthy pancreas and in chronic pancreatitis tissue samples in rats and humans to evaluate their possible involvement in a multidrug resistance of the pancreas with consequences for the pharmacologic treatment of pancreatic diseases. Human pancreatic tissue samples of healthy tissue and chronic pancreatitis were collected during pancreas surgery. In rats, the time-course of the expression of transporter proteins was studied 14, 28, and 56 days after experimental induction of chronic pancreatitis. The expression of MDR-1, MRP-1, MRP-2, and furthermore, LRP and PAP was investigated by RT-PCR, Real Time TaqManPCR, and immunohistochemistry. In rat pancreas, MDR-1 (P-gp) and MRP-1 but in human pancreas MDR-1 (P-gp), MRP-1 and MRP-2 were found to be expressed. Chronic pancreatitis lead to an increased transcription of mRNA of MDR-1 (rat and human) and much lower, MRP-2 (human). The expression of P-gp and related transporters could have impact on the metabolism, distribution, and availability of various compounds, including drugs, in the pancreas. The results indicate that this could be more pronounced in chronic pancreatitis.

Clinical characteristics, prognostic factors and multidrug-resistance related protein expression in 36 adult patients with acute promyelocytic leukemia.

We report on a single-center experience about the characteristics and outcome of 36 acute promyelocytic leukemia (APL) patients observed at our Department of Hematology between 1990 and 2002. The expression, of multidrug-resistance (MDR) associated proteins (PGP, LRP, MRP1) was also analyzed. There were 12 males and 24 females (median age 37 yr), 89% (32 of 36) with classic morphology, and 11% (four of 36) with a microgranular variant. Risk class (according to GIMEMA/PETHEMA): 25% (nine of 36) high risk (HR), 53% (nineteen of 36) intermediate risk (IR), 22% (eight of 36) low risk (LR). PGP, LRP, and MRP1 expression at onset and at first relapse was low. CD33 antigen expression was high in all cases. The patients were treated according to GIMEMA protocols (LAP0389 and AIDA) including ATRA in induction in 75% (27 of 36) of cases and 94% (34 of 36) achieved a complete remission (CR) after induction therapy while 6% (two of 36) died early (DDI) of hemorrhage. 71% (24 of 34) of evaluable patients remain in CR at a median follow-up of 57 months (range 4-158 months) while 29% (10 of 34) relapsed at a median time of 12 months (range 8-43 months) and, of them, eight of 10 died early. The majority of patients that relapsed were in high-risk group. The overall survival (OS) of the whole population at 32 months was 66% and the DFS at 42 months was 62%. A statistically significant difference in terms of DFS was observed between HR and IR/LR patients (P = 0.04 by log-rank). DFS was not affected by age, sex, Hb levels, karyotype, and BCR isoform. At conclusion, our data confirm that despite the high rate of success with ATRA plus chemotherapy as induction (more than 90% of CR), about 30% of APL patients have a relapse (without a long-lasting second remission) and underline the importance of patient stratification in distinct risk groups at diagnosis in order to better adapt the type and intensity of treatment (risk-adapted therapy). Taking into account the high expression of CD33 and the low expression of MDR proteins in APL, new and investigational approaches like gemtuzumab-ozogamicin, with or without ATRA and other new drugs, should be strongly considered expecially in HR APL.