Expression of MDR1/P glycoprotein in human sarcomas

Single-agent gemcitabine in patients with advanced, pre-treated angiosarcoma: A multicenter, retrospective study

Gemcitabine has shown clinical activity against angiosarcoma in small series, alone, or combined with taxanes. We aimed to evaluate its activity as a single-agent in a larger series of patients with advanced angiosarcoma. We retrospectively reviewed the electronic medical records of consecutive adult patients with advanced angiosarcoma treated with single-agent gemcitabine at our institutions from January 2010 to January 2021. Response was evaluated according to RECIST 1.1, and toxicity was graded according to NCI-CTC v5.0. 42 patients were identified. 38 patients (90%) had received prior anthracyclines and weekly paclitaxel, and 9 (21%) had received pazopanib. The best tumor response was partial response (PR) in 16 patients (38%), or stable disease (10 patients, 24%). All 8 patients with cardiac angiosarcoma experienced a PR. Median PFS was 5.4 months (95%CI: 3.1-6.5), and median OS was 9.9 months (95%CI: 6.6-13.4). Single-agent gemcitabine has clinically meaningful activity in advanced, heavily pre-treated angiosarcoma.

Itraconazole Reverts ABCB1-Mediated Docetaxel Resistance in Prostate Cancer

Docetaxel (DTX) was the first chemotherapeutic agent to demonstrate significant efficacy in the treatment of men with metastatic castration-resistant prostate cancer. However, response to DTX is generally short-lived, and relapse eventually occurs due to emergence of drug-resistance. We previously established two DTX-resistant prostate cancer cell lines, LNCaP^R and C4-2B^R, derived from the androgen‐dependent LNCaP cell line, and from the LNCaP lineage-derived androgen-independent C4-2B sub-line, respectively. Using an unbiased drug screen, we identify itraconazole (ITZ), an oral antifungal drug, as a compound that can efficiently re-sensitize drug-resistant LNCaP^R and C4-2B^R prostate cancer cells to DTX treatment. ITZ can re-sensitize multiple DTX-resistant cell models, not only in prostate cancer derived cells, such as PC-3 and DU145, but also in docetaxel-resistant breast cancer cells. This effect is dependent on expression of ATP-binding cassette (ABC) transporter protein ABCB1, also known as P-glycoprotein (P-gp). Molecular modeling of ITZ bound to ABCB1, indicates that ITZ binds tightly to the inward-facing form of ABCB1 thereby inhibiting the transport of DTX. Our results suggest that ITZ may provide a feasible approach to re-sensitization of DTX resistant cells, which would add to the life-prolonging effects of DTX in men with metastatic castration-resistant prostate cancer.

Angiosarcoma: state of the art and perspectives

We propose a literature review of available data on angiosarcoma (AS). AS account for 1% of adult soft tissue sarcoma. Two risk factors are well-establish chronic lymhoedema, previous radiotherapy. Clinical presentations of AS are heterogeneous. Large resection followed, if possible, by adjuvant radiotherapy is the cornerstone of curative intent treatment of localized forms. There are no convincing data supporting the administration of adjuvant chemotherapy. For metastatic or locally advanced AS, doxorubicin and weekly paclitaxel seem to provide the longer progression-free survival. Three phase II or parts of phase II trials have been published in the last 2 years, investigating weekly paclitaxel, sorafenib and imatinib, demonstrating that clinical trials are feasible for such rare diseases. Biological evidences for the key role of angiogentic factors have been accumulated during the last years and support the further investigation of anti-angiogenetic agents alone and almost combination with chemotherapy in such disease.

Cardiac stem cells: isolation, expansion and experimental use for myocardial regeneration

Cellular cardiomyoplasty (myogenic cell grafting) is actively being explored as a novel method to regenerate damaged myocardium. The adult human heart contains small populations of indigenous committed cardiac stem cells or multipotent cardiac progenitor cells, identified by their cell-surface expression of c-kit (the receptor for stem cell factor), P-glycoprotein (a member of the multidrug resistance protein family), and Sca-1 (stem cell antigen 1, a mouse hematopoietic stem cell marker) or a Sca-1-like protein. Cardiac stem cells represent a logical source to exploit in cardiac regeneration therapy because, unlike other adult stem cells, they are likely to be intrinsically programmed to generate cardiac tissue in vitro and to increase cardiac tissue viability in vitro. Cardiac stem cell therapy could, therefore, change the fundamental approach to the treatment of heart disease.

The role of a novel copper complex in overcoming doxorubicin resistance in Ehrlich ascites carcinoma cells in vivo

One of the important pathways of resistance to anthracyclines is governed by elevated levels of glutathione (GSH) in cancer cells. Resistant cells having elevated levels of GSH show higher expression of multidrug-resistant protein (MRP); the activity of glutathione S-transferases (GSTs) group of enzymes have also been found to be higher in some drug-resistant cells. The general mechanism in this type of resistance seems to be the formation of conjugates enzymatically by GSTs, and subsequent efflux by active transport through MRP (MRP1-MRP9). MRPs act as drug efflux pump and can also co-transport drugs like doxorubicin (Dox) with GSH. Depletion of GSH in resistant neoplastic cells may possibly sensitize such cells, and thus overcome multidrug resistance (MDR). A number of resistance modifying agents (RMA) like DL-buthionine (S, R) sulfoxamine (BSO) and ethacrynic acid (EA) moderately modulate resistance by acting as a GSH-depleting agent. As most of the GSH-depleting agents have dose-related toxicity, development of non-toxic GSH-depleting agent has immense importance in overcoming MDR. The present study describes the resistance reversal potentiality of novel copper complex, viz., copper N-(2-hydroxy acetophenone) glycinate (CuNG) developed by us in Dox-resistant Ehrlich ascites carcinoma (EAC/Dox) cells. CuNG depletes GSH in resistant (EAC/Dox) cells possibly by forming conjugate with it. Depletion of GSH results in higher Dox accumulation that may lead to enhanced rate of apoptosis in EAC/Dox cells. In vivo studies with male Swiss albino mice bearing ascitic growth of EAC/Dox showed tremendous increase in life span (treated/control, T/C = 453%) for the treated group with apparent regression of tumor. Resistance to Dox in EAC/Dox cells is associated with over expression of GST-P1, GST-M1 (enzymes involved in phase II detoxification) and MRP1 (a transmembrane ATPase efflux pump for monoglutathionyl conjugates of xenobiotics). CuNG causes down regulation of all these three proteins in EAC/Dox cells. The effect of CuNG as RMA is better than BSO in many aspects.

The association of P-glycoprotein with response to chemotherapy and clinical outcome in patients with osteosarcoma. A meta-analysis

BACKGROUND

There is controversy regarding whether P-glycoprotein (Pgp) may be a prognostic factor for the response to chemotherapy and clinical disease progression in patients with osteosarcoma.

METHODS

The authors conducted a meta-analysis of 14 studies (n = 631 patients) that evaluated the correlation between Pgp and histologic response to chemotherapy and clinical disease progression (death, metastasis, or recurrence). Data were synthesized in receiver operating characteristic curves and with fixed-effects and random-effects likelihood ratios and risk ratios.

RESULTS

Pgp had no discriminating ability for identifying poor responders versus good responders to chemotherapy: The positive likelihood ratio was 1.15 (95% confidence interval [95% CI], 0.93-1.43), and the negative likelihood ratio was 0.88 (95% CI, 0.65-1.18; random-effects calculations). There was some between-study heterogeneity, but no study showed strong discriminating ability. Conversely, Pgp positivity increased the risk of disease progression 1.92-fold (95% CI, 1.18-3.13; random-effects calculations) with some between-study heterogeneity that disappeared when only studies that employed immunohistochemistry were considered (risk ratio, 2.23; 95% CI, 1.37-3.64). The results were robust in various sensitivity analyses, although smaller studies tended to show stronger associations with the risk of disease progression compared with larger studies (P = 0.03).

CONCLUSIONS

The available evidence showed conclusively that Pgp was not associated with the histologic response of patients with osteosarcoma to combination chemotherapy regimens. Conversely, Pgp positivity, as determined by immunohistochemistry, was a strong correlate of more rapid disease progression, although there was heterogeneity across the performed studies that, to some extent, may have reflected bias, differential measurements of Pgp, or confounding with other risk factors.

Effect of P-glycoprotein expression on outcome in the Ewing family of tumors

This study was designed to determine the prognostic significance of multidrug resistance, mediated by P-glycoprotein (Pgp) expression, in Ewing sarcoma. The clinical and laboratory features, treatment protocol, and outcome of 75 patients with Ewing sarcoma or peripheral neuroectodermal tumor treated between 1972 and 1997 were reviewed. Pgp expression was tested with the monoclonal antibody JSB-1. Thirty-four (64%) of the 53 tissue samples from untreated patients stained positive for Pgp. Progression-free and overall survival were 44 and 59%, respectively, in patients with negative findings, and 28 and 41% in those with positive findings; neither difference was significant. Of the 12 relapsed patients, 6 (50%) expressed more Pgp after chemotherapy than at diagnosis and 4 (33%) expressed less. Within these subgroups, 5 out of 6 and 3 out of 4 died from the disease. No correlation was found between Pgp and known prognostic factors of Ewing tumors. Pgp expression is probably an intrinsic factor of Ewing tumors but has no correlation to prognosis.

Modulation of myogenic differentiation in a human rhabdomyosarcoma cell line by a new derivative of 5-fluorouracil (QF-3602)

The in vitro study of mechanisms involved in drug-induced maturation has made it possible to use differentiation-based therapy in clinical practice. The goal of this new therapy is the development of specific agents to induce cancer cells to stop proliferating and express characteristics of normal cells. Recently, by structural modifications of 5-fluorouracil (5-FU), we synthesized a new pyrimidine acyclonucleoside-like compound, 1-¿[3-(3-chloro-2-hydroxypropoxy)-1-methoxy]propyl¿-5-fluorouracil (QF-3602), which showed in rhabdomyosarcoma cells a low toxicity and time-dependent growth inhibition. In this work, we compared the degree of myogenic differentiation of RD rhabdomyosarcoma (RMS) cells after treatment with QF-3602 and 5-FU. Scanning and transmission electron microscopy (SEM and TEM) and immunocytochemical analyses showed that QF-3602 induced the appearance of myofilaments along the myotube-like giant RD cells, an increase in fibronectin and a decrease in vimentin expression. In contrast, only minor changes were observed with 5-FU. Moreover, polymerase chain reaction (PCR) analyses showed that QF-3602 did not induce overexpression of the mdr 1 gene, a resistance mechanism that frequently appears in classical cytotoxic therapy in these tumors. Compounds obtained by structural modifications of 5-FU may be useful in differentiation therapy as a new approach to the treatment of RMS.

Incidence of P-glycoprotein overexpression and multidrug resistance (MDR) reversal in adult soft tissue sarcoma

Multidrug resistance (MDR) is a widespread problem in the treatment of neoplastic diseases and may limit the effectiveness of treatment of adult soft tissue sarcomas (STS). We examined the levels of expression of the MDR marker P-glycoprotein (Pgp) in fresh, surgical material and matched paraffin-embedded tissue using MRK-16 and JSB-1 monoclonal antibodies. Using fresh tumour material in short-term culture an assessment of doxorubicin sensitivity (MTT assay) and MDR modulation using PSC-833 in daunorubicin (DNR) accumulation experiments (FACS analysis) was carried out. 44 patients were studied at various disease stages with a mean follow-up duration of 487 days (range: 45-1095 days). Immunocytochemistry and immunohistochemistry showed 62% and 58%, respectively, of STS samples were positive for Pgp. Patients showing negative Pgp expression had a median survival of 544 days versus 431 days for Pgp-positive patients (P=0.311), with disease-free survival medians of 508 and 355 days, respectively (P=0.203). In vitro doxorubicin sensitivity was not informative in this respect and there was no apparent relationship between this and Pgp expression. Eleven out of 29 samples evaluated for MDR modulation showed enhanced tumour cell DNR accumulation. However, the effects of PSC-833 on drug accumulation in clinical material were modest compared with those seen for MDR cell lines, with a maximum of only 20% enhancement. Moreover, there was no relationship between the extent of PSC-833 effects on accumulation and the levels of Pgp seen in the STS samples. Nevertheless, we show evidence that a proportion of cases of STS express moderate to high levels of Pgp. There may be a role for MDR modulating agents in association with doxorubicin in the treatment of these tumours, either in the adjuvant setting or at first relapse.

Multidrug resistance phenotype in high grade soft tissue sarcoma: correlation of P-glycoprotein immunohistochemistry with pathologic response to chemotherapy

BACKGROUND

P-glycoprotein-mediated drug efflux has been implicated as an important mechanism of multidrug resistance (MDR) in cancer. Its role in chemotherapy resistance in soft tissue sarcoma is unclear.

METHODS

Tumor specimens prior to and following neoadjuvant chemotherapy from 29 cases of high grade soft tissue sarcoma were analyzed with 2 monoclonal antibodies (C494 and JSB-1) that recognize different epitopes of P-glycoprotein. Staining intensity was graded 0 = negative, 1 = equivocal, 2 = moderate, 3 = strong. Only cases with Grade 2 or 3 staining intensity with both antibodies were considered MDR positive. The resection specimens were evaluated for tumor necrosis postchemotherapy. Pathologic response was graded as good for <15%, moderate for 15-50%, or poor for >50% posttreatment tumor viability.

RESULTS

Of the 29 pretreatment specimens, 10 (34%) were MDR positive and 19 (66%) were MDR negative. Pathologic response to treatment was characterized as good in 6, moderate in 7, and poor in 16 patients. Of the MDR positive biopsies, 9 (90%) had poor response, compared with 7 (36%) in the MDR negative biopsy group (P = 0.0078). None of the cases with MDR positive biopsies had a good response, compared with 6 cases in which biopsies were MDR negative (32%) (P = 0.057). Only one MDR negative case became MDR positive posttreatment.

CONCLUSIONS

Expression of MDR phenotype is found in approximately one-third of high grade soft tissue sarcomas. These preliminary data show a significant correlation between MDR phenotype and poor pathologic response to chemotherapy, and suggest that MDR induction by chemotherapy in soft tissue sarcoma is an uncommon event.

Multidrug resistance phenotype in the RMS-GR human rhabdomyosarcoma cell line obtained after polychemotherapy

Classical cytotoxic treatment of rhabdomyosarcoma (RMS), the most common soft tissue malignacy in children, is often accompanied by significant morbidity and poor response. Chemotherapy may induce multidrug resistance (MDR) associated with the expression of P-glycoprotein, a drug efflux pump which modifies the sensitivity of tumoral cells to drugs. To analyze MDR in RMS we used the RMS-GR cell line, obtained from an embryonal rhabdomyosarcoma treated in vivo with polychemotherapy. The RMS-GR cells showed cross-resistance to vincristine, doxorubicin and actinomycin D, the drugs of choice in the conventional treatment of RMS. Polymerase chain reaction (PCR) analysis showed that these RMS cells overexpressed mdr1/P-glycoprotein. The pattern of resistance and the level of P-glycoprotein expression were similar to those found in the resistant RMS TE.32.7.DAC cell line obtained in vitro. Southern blot analysis showed that mdr1 overexpression was not due to amplification of the gene. Our results showed that the in vivo treatment of embryonal RMS may induce an MDR phenotype mediated by mdr1/P-glycoprotein in RMS cells.

Multidrug resistance in oncology: diagnostic and therapeutic approaches

Resistance to anticancer drugs is often mediated by the overexpression of a membrane pump able to extrude many xenobiotics out of the tumour cells. The most frequently expressed of these pumps is called P-glycoprotein and is encoded by a gene called MDR1 (for multidrug resistance). There could be great clinical interest for investigating the expression of this gene or of its product in patients' tumours, as well as in developing ways of circumventing this mechanism of resistance. Multidrug resistance can be diagnosed in tumours by molecular biology techniques (gene expression at the mRNA level), by immunological techniques (quantification of P-glycoprotein itself) or by functional approaches (measuring dye exclusion). Numerous studies have tried to use the MDR status of tumours as a predictor of response to treatment, but they have not yet reached definitive conclusions to allow the use of this approach in routine determinations. This is because no consensus has emerged concerning the optimal technique and the best conditions for MDR determination. Continuous efforts are still required for defining appropriate standardization of the techniques. The development of MDR modulators for the treatment of resistant tumours is a promising approach requiring rigorous clinical trials with successive phase I, phase II and phase III studies. Phase I can be omitted when the reverter is already being used in therapeutics; phase II should be performed using a sequential design, in order to prove the inefficacy of the anticancer therapy before combining it to a modulator; and phase III must only be undertaken after the demonstration that responders can be recruited by the combination. However, the effect of some reverters on anticancer drug pharmacokinetics may hamper rapid evaluation. Several drugs are good candidates for MDR modulation, but definitive results are still lacking for the introduction of such combinations in standard therapeutic protocols.

Resistance to anticancer drugs: are we ready to use biologic information for the treatment of patients with cancer?

Multidrug resistance (MDR) to anticancer drugs can be diagnosed in tumors by molecular biology techniques (expression of the MDR1 gene), by immunologic techniques (expression of P-glycoprotein), and by functional approaches (dye exclusion). Numerous studies have tried to correlate the MDR status of tumors to the clinical response to the treatment, but wide discrepancies prevented definitive conclusions. As a consequence, the routine use of these techniques is still not possible, and continuous efforts are needed for their standardization. The development of MDR modulators in the clinical setting is a promising approach that requires rigorous clinical trials, especially with sequential design of phase 2 protocols. Definitive results are still lacking concerning the interest of combining an MDR modulator to standard chemotherapy for resistant cancers.

High-dose cyclosporin with etoposide--toxicity and pharmacokinetic interaction in children with solid tumours

The tolerability, anti-tumour activity and pharmacokinetic interaction of high-dose intravenous cyclosporin combined with intravenous etoposide was evaluated in children. Eighteen patients with recurrent or refractory tumours, all of whom had previously received etoposide, were treated with a combination of high-dose cyclosporin and etoposide. In 13, cyclosporin was given as a continuous infusion (15 mg kg(-1) per 24 h for 60 h) and in five a short 3-hour infusion of 30 mg kg(-1) day(-1) on three consecutive days. Pharmacokinetic profiles of etoposide were determined with and without cyclosporin. Cyclosporin levels ranged from 1359 to 4835 ng ml(-1) and cyclosporin increased the median area under the concentration time for etoposide curve from 7.2 to 12.5 mg ml(-1) min. The major toxicity was acute with varying forms of hypersensitivity reactions. In four cases this was severe. Hyperbilirubinaemia was present in 25 of 32 courses but was of short duration. In 14 courses, creatinine and/or urea was elevated, but was also transient. Significant hypertension was seen in six courses. Four of 17 patients evaluable for response obtained a partial response and one showed stable disease. It is concluded that in children given the combination of high-dose cyclosporin and etoposide, the etoposide dose should be halved in order to achieve an area under the drug concentration-time curve similar to that with etoposide alone. A continuous infusion schedule of cyclosporin is better tolerated during the period of administration but is associated with similar hepatic and renal dysfunction to a short schedule. The 24% response rate in children who had previously received etoposide suggests that this may be an effective method of enhancing drug sensitivity and further phase II evaluation is justified.

Therapeutic differentiation in a human rhabdomyosarcoma cell line selected for resistance to actinomycin D

Classical cytotoxic treatment of rhabdomyosarcoma (RMS) is accompanied often by significant morbidity and poor response. The use of cytotoxic agents may induce a multidrug resistance phenotype, which plays an important role in the sensitivity of tumoral cells to drugs. Using actinomycin D, a drug of choice in the treatment of RMS, we induced resistance in the TE.32.7 human RMS cell line. The TE.32.7-DAC-resistant cell line exhibited cross-resistance to vincristine and doxorubicin and showed mdr1/P-glycoprotein over-expression, suggesting that this mechanism was involved in the reduction in intracellular drug concentration and may be responsible for the failure of treatment of RMS with classical cycles of cytotoxics. Furthermore, this resistant cell line showed increased expression of the muscle differentiation markers desmin and alpha-actinin and ultrastructural changes which clearly indicated myogenic differentiation. Our findings suggest that, although this tumor is probably arrested along the normal myogenic pathway to maturation, induction of cell differentiation with anti-neoplastic drugs may be an alternative therapeutic approach. However, the failure of TE.32.7-DAC cells to completely re-enter the program of myogenic differentiation supports the hypothesis that multidrug resistance is a major obstacle in differentiation therapy for RMS.

In situ hybridization and its diagnostic applications in pathology

In situ hybridization (ISH) is a technique by which specific nucleotide sequences are identified in cells or tissue sections. These may be endogenous, bacterial or viral, DNA or RNA. On the basis of research applications, the technique is now being translated into diagnostic practice, mainly in the areas of gene expression, infection and interphase cytogenetics. Diagnostic applications are most often based on short nucleotide sequences (oligomers) labelled with non-isotopic reporter molecules, and sites of binding may be localized by histochemical or immunohistochemical methods. The technique can be applied to routinely fixed and processed tissues; with some targets, it is even possible to obtain hybridization in autopsy material. ISH has been used to detect messenger RNA (mRNA) as a marker of gene expression, where levels of protein storage are low; for example, to confirm an endocrine tumour as the source of excess hormone production. Its application in infectious diseases has to date been mainly in viral infections, such as the typing of human papillomavirus (HPV) or the detection of Epstein-Barr virus by the presence of small nuclear RNAs (EBERs). The expression of mRNAs for histone proteins has been used to detect cells in S phase, and related methods may be applied to detect apoptotic cells. Using probes to chromosome-specific sequences, it is possible to detect aneuploidy, and to document changes in specific chromosomes, which may have prognostic significance in some tumours, such as B-cell chronic lymphatic leukaemia. Using sequence-specific probes, translocations can be identified, such as the t(11;12) of Ewing's sarcoma. This review presents an outline of the technique of in situ hybridization and discusses areas of current and potential diagnostic application.

A new mdr-1 encoded P-170 specific monoclonal antibody: (6/1C) on paraffin wax embedded tissue without pretreatment of sections

AIMS

The generation and characterisation of a monoclonal antibody that specifically recognises the mdr-1 encoded protein, P-glycoprotein (P-170), on routinely processed formalin fixed, paraffin wax embedded tissue sections.

METHODS

The monoclonal antibody, designated 6/1C, was produced following a combination of in vivo and in vitro immunisation regimens in Balb/c mice with a synthetic 12 amino acid peptide that corresponds to amino acids 21-32 (believed to be intracellularly located) of P-170 and has insignificant homology with the mdr-3 encoded P-170. Antibody 6/1C was characterised by western blotting and immunocytochemistry on cytospins of paired multidrug resistant or sensitive cell lines, including mdr-1 and mdr-3 transfected cells, and by immunohistochemistry on normal and malignant formalin fixed paraffin wax embedded tissue sections.

RESULTS

Antibody 6/1C showed a single band at 170 kDa on western blots of multidrug resistant cell lysates and mdr-1 transfected cell lysates that was absent on similar preparations of drug sensitive cells and mdr-3 transfected cells. Immunocytochemical studies on cytospins of multidrug resistant cells and mdr-1 transfected cells revealed strong inner plasma membrane/cytoplasmic staining. Staining was negligible on drug sensitive cells and cells transfected with the mdr-3 gene. Immunohistochemical studies on formalin fixed, paraffin wax embedded normal adult kidney, liver, and breast tissue and a range of fetal tissues exhibited staining patterns of a variety of secretory surfaces consistent with documented mdr-1 specific staining. Specific staining of malignant cells in similarly treated sections of breast tumours was seen also with antibody 6/1C. Staining on paraffin wax embedded tissue with this antibody did not require any pretreatment of tissue sections.

CONCLUSIONS

This new monoclonal antibody, chosen for its specificity with the mdr-1 encoded P-170 and its reactivity on routinely fixed paraffin wax embedded tissue samples without pretreatment, appears to be useful for the investigation of P-170 in archival material. It is especially useful for retrospective studies on pretreatment and post-treatment tissue sections, and could help establish when and how rapidly mdr-1 associated drug resistance develops during chemotherapeutic regimens. Immunohistochemical assessment of P-170 expression in many cancers has potential for diagnostic purposes and may influence the choice of chemotherapeutic drugs used in the treatment of refractory tumours.

Quantitative analysis of multidrug resistance gene expression in human osteosarcomas

We evaluated the MDR1 expression levels in 77 osteosarcomas and investigated whether MDR1 mRNA expression in osteosarcomas varies with location within the tumour, following chemotherapy, or after metastasis. We modified the semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) assay to determine accurately the levels of MDR1 mRNA expression in clinical specimens. We show that specimens collected from multiple locations in six tumours revealed very little variation in MDR1 expression suggesting that the levels of MDR1 in these tumours do not vary greatly with location within the tumour mass. In a comparison of pre and post-chemotherapy specimens it was found that MDR1 levels did not change appreciably following chemotherapy in 16 of 20 cases. In addition, in eight of ten specimens obtained before and after metastasis, the amount of MDR1 mRNA was found to remain relatively constant despite metastatic spread. Thus, many osteosarcomas exhibited intrinsic expression of MDR1 mRNA before multidrug regimens which invariably included doxorubicin and, in most cases, MDR1 expression was not induced following chemotherapeutic treatment. Our results suggest that some osteosarcoma patients may have primary tumours which are resistant to doxorubicin. These individuals may benefit from different chemotherapeutic regimens, e.g. the addition of MDR reversal agents.

Inverse expression of mdr 1 and c-myc genes in a rhabdomyosarcoma cell line resistant to actinomycin d

Cytotoxic agents used in cancer therapy may induce differentiation in tumour cells with no proliferative potential. However, chemotherapy can also induce multidrug resistance, a formidable obstacle to the successful treatment of tumours. Both events were recently shown to occur in a rhabdomyosarcoma cell line (RD-DAC) resistant to actinomycin D, a drug of choice in the treatment of these tumours. To analyse this connection, cell line RD cultures were investigated with progressive concentrations of actinomycin D and it was shown that a minimum dose (1.2 x 10(-6) mM) of the drug was necessary to increase mdr 1 mRNA in RD-DAC. The mechanism of mdr 1 overexpression was an increase in the number of copies of the mdr 1 gene, although the mRNA levels were not correlated with mdr 1 amplification. Drug resistance mediated by mdr 1 overexpression coincided with the development of myogenic differentiation in RD-DAC and with a decrease in c-myc mRNA levels, whereas levels of N-myc mRNA showed no modulation. These findings suggest that factors implicated in cell proliferation and differentiation, such as c-myc, may be responsible for the control of genes related to the development of multidrug resistance in rhabdomyosarcomas. Modulation of these factors may determine the sensitivity of rhabdomyosarcoma cells to drugs and may play an important role in triggering the differentiation programme found in these resistant rhabdomyosarcoma cells.

Reverse transcriptase-polymerase chain reaction amplification of MDR1 gene expression in adult soft tissue sarcomas

Expression of the multidrug resistance gene MDR1 is reported to be an important determinant of the response to chemotherapy and survival in some cancers. We compared three methods for determining the intrinsic MDR1 expression in soft tissue sarcomas. We studied MDR1 gene expression in 39 samples from 33 cases of soft tissue sarcomas comprising 11 liposarcomas, nine malignant fibrous histiocytomas, six leiomyosarcomas, four malignant schwannomas, three fibrosarcomas, three synovial sarcomas, and three epithelioid sarcomas, and seven cases of benign soft tissue tumors in adult patients. To detect MDR1 mRNA, reverse transcriptase-polymerase chain reaction (RT-PCR) was performed in all samples. Furthermore, RNA dot-blot analysis with digoxigenin-labeled RNA probe and immunohistochemistry with JSB-1 and C-219 antibodies for P-glycoprotein were employed in 34 and 37 samples in soft tissue sarcomas, respectively. We compared these three detection techniques. Of the 39 specimens, 18 (46%) showed MDR1 PCR products. Liposarcomas (six of 11), malignant fibrous histiocytomas (six of nine), leiomyosarcomas (four of six), fibrosarcomas (two of three) revealed high or intermediate MDR1 expression at high frequency. No MDR1 expression was detectable in malignant schwannomas, synovial sarcomas, or epithelioid sarcomas. Of seven benign soft tissue tumors, one ganglioneuroma and one lipomatosis showed low levels of MDR1 expression. By RNA dot-blot analysis, MDR1 transcripts were detectable in 12 of 34 specimens (35%). Four samples were negative by dot blot despite positivity with RT-PCR. Concordance between MDR1 expression by RNA level with RT-PCR and dot blot and at the protein level with immunohistochemistry using C-219 was found in 16 (47%) of the 34 comparable specimens. Eight samples showed positive immunoreactivity for C-219 despite negative results in RT-PCR and dot-blot analysis. The intrinsic MDR1 expression in soft tissue sarcoma seemed to depend on certain tumor types, such as liposarcoma, malignant fibrous histiocytoma, leiomyosarcoma, and fibrosarcoma. For the evaluation of MDR1 expression, RT-PCR is useful because of its relative simplicity and sensitivity. However, the clinical significance of such low levels of MDR1 expression detected only by RT-PCR must be discussed within systematically treated patient groups.

Expression of multidrug-resistance-associated protein gene in human soft-tissue sarcomas

We examined the mRNA expression of the multidrug- resistance-associated protein gene (MRP) in soft-tissue sarcomas and compared it with the expression of the multidrug resistance gene (MDR1), using the reverse transcriptase/polymerase chain reaction. We investigate 39 samples from 33 cases of soft-tissue sarcomas (11 liposarcomas, 9 malignant fibrous histiocytomas, 6 leiomyosarcomas, 4 malignant schwannomas, 3 fibrosarcomas, 3 synovial sarcomas, and 3 epithelioid sarcomas) and 7 benign soft-tissue tumors. All samples were obtained prior to chemotherapy. An expression of MRP mRNA was noted in 56% of soft-tissue sarcoma specimens. The co-expression of MRP and MDR1 was recognized in 15 samples (38%) (5/11 liposarcomas, 5/9 malignant fibrous histiocytomas, 3/6 leiomyosarcomas, 2/3 fibrosarcomas) and significantly correlated with histological grade (P=0.0165). A positive and significant correlation was found between MRP and MDR1 expression in soft-tissue sarcomas(P=0.0013). In benign soft-tissue tumors, 1 chemodectoma and 1 neurothekeoma showed low MRP expression; however, no case showed co-expression of MRP and MDR1.

Low concentrations of actinomycin D potentially cause therapeutic differentiation in human rhabdomyosarcoma cell line RD

Neoplastic transformation may be an alteration in the process of cell maturation that leads to an infinite capacity for proliferation. Because the cytodestruction caused by most drugs available for cancer chemotherapy is often accompanied by significant morbidity and poor response, the induction of differentiation has been proposed as an alternative approach to conventional anticancer therapy. We used human rhabdomyosarcoma cell line RD to analyze the differentiation process induced by actinomycin D, a drug of choice in the conventional treatment of rhabdomyosarcomas. Low concentrations of actinomycin D induced a terminal process of morphological and ultrastructural myogenic differentiation in rhabdomyosarcoma cells, which concluded with cell death. However, this potential therapeutic effect cannot be considered complete because of the presence of tumoral cells that are heterogeneous with respect to actinomycin D chemosensitivity. This heterogeneity led to the appearance of foci of resistant cells which, despite their greater degree of differentiation in comparison with the parental cell line, escaped from terminal myogenic differentiation. This subgroup of tumoral cells may be responsible for the failure of cytotoxic treatment.

Evaluation of P-glycoprotein expression in soft tissue sarcomas of the extremities

Soft tissue sarcomas comprise a heterogeneous group of mesenchymal tumors accounting for less than one-percent of adult neoplasms. In the last few years, the use of adjuvant chemotherapy has been proposed for the treatment of these lesions in order to obtain a better systemic control, but its usefulness is still controversial. In this study, we evaluated whether P-glycoprotein, a membrane protein strictly associated with multidrug resistance, is overexpressed in soft tissue sarcomas. By using human multidrug resistant sarcoma cell lines as controls, we analyzed P-glycoprotein expression in 34 primary and in 23 relapsed soft tissue sarcomas of the extremities. Overexpression of P-glycoprotein was found in 6 out of 34 primaries (18%) and in 8 out of 23 relapses (35%). In particular, in malignant fibrous histiocytoma, the most frequent soft tissue sarcoma of adults, P-glycoprotein overexpression was found in 23% of primary untreated cases, in agreement with the reported relapse rate of this tumor after surgery and chemotherapy. These data suggest that, in soft tissue sarcomas, overexpression of P-glycoprotein may be of prognostic value and that the assessment of P-glycoprotein expression may be useful for the design of chemotherapy protocols.

MDR1 gene expression: evaluation of its use as a molecular marker for prognosis and chemotherapy of bone and soft tissue sarcomas

Successful chemotherapeutic treatment of malignant tumours is often limited by the intrinsic or acquired multidrug resistance (MDR). The classical MDR phenotype is characterised by reduced drug accumulation within the cell, caused by overexpression of the MDR1 gene encoded P-glycoprotein. Some reports have been published evaluating MDR1 expression as a molecular marker for response to chemotherapy in human bone and soft tissue sarcomas. In this review, an attempt is made to summarise the accuracy of the measurement of MDR1 expression for use in prognosis, as well as in decisions on chemotherapeutic treatment of sarcomas. In addition, general problems for the performance of such studies is discussed.

A novel site of DNA amplification on chromosome 1p32-33 in a rhabdomyosarcoma revealed by comparative genomic hybridization

Cytogenetic analysis of a human embryonal rhabdomyosarcoma revealed a near-diploid karyotype with structural chromosome aberrations not involving the typical rearrangements of rhabdomyosarcomas, plus a large number of double minutes. Comparative genomic hybridization revealed a previously undescribed site of DNA amplification on the short arm of chromosome 1 (band 1p32-33).

Expression of P-glycoprotein in high-grade osteosarcomas in relation to clinical outcome

BACKGROUND

Increased levels of P-glycoprotein occur in some osteosarcomas. In this study we determined the relation between P-glycoprotein status and outcome in patients with high-grade osteosarcoma.

METHODS

P-glycoprotein status was determined immunohistochemically in specimens of osteosarcoma of the extremities (stage II) from 92 patients who were treated with surgery and chemotherapy. The P-glycoprotein status was analyzed in relation to the length of event-free survival.

RESULTS

The presence of increased levels of P-glycoprotein in the osteosarcoma was significantly associated with a decreased probability of remaining event-free after diagnosis (P = 0.002). In a multivariate analysis, P-glycoprotein status (P = 0.001) and the extent of tumor necrosis after preoperative chemotherapy (P = 0.04) were independent predictors of clinical outcome. The risk of adverse events was increased substantially (rate ratio, 3.37; 95 percent confidence interval, 1.60 to 7.10) among patients with increased levels of P-glycoprotein in tumor cells, as compared with patients who did not have increased levels of P-glycoprotein in tumor cells.

CONCLUSIONS

In patients with high-grade osteosarcoma treated with surgery and chemotherapy, the presence of increased levels of P-glycoprotein in tumor cells is associated with a significantly increased risk of adverse events and is independent of the extent of necrosis after preoperative chemotherapy.

Analysis of P-glycoprotein expression in osteosarcoma

Current treatment of high-grade osteosarcoma combines surgical removal of the lesion with chemotherapy. In this study we evaluated whether the expression of P-glycoprotein, a protein closely associated with multidrug resistance, may be helpful in identifying the patients whose tumours will be further resistant to specific agents. By using multidrug-resistant osteosarcoma cell lines as standards, the expression of P-glycoprotein was evaluated in 105 cases of primary and metastatic osteosarcoma by semiquantitative immunofluorescence. Overexpression of the protein was shown in 23% of primary and in 50% of metastatic lesions. In 38 cases, homogeneously treated and followed-up for at least 24 months, overexpression of P-glycoprotein appeared to be associated with a higher relapse rate and with a trend toward a worse outcome. These data support the role of P-glycoprotein in the response to chemotherapy and its involvement in the determination of the outcome of osteosarcoma patients.

Determination of DNA topoisomerase II in newly diagnosed childhood acute lymphoblastic leukemia by immunocytochemistry and RT-PCR

The expression of DNA-topoisomerase II was analysed at the protein level in newly diagnosed cases of acute lymphoblastic leukemia (ALL) in children. Blast cells obtained from 81 children with untreated ALL were determined by means of immunocytochemistry. Of the ALL, 49 (60%) were positive for topoisomerase II and 32 (40%) negative. No significant correlation was found between the expression of topoisomerase II and the relapse rate or relapse-free intervals. These results were substantiated by determining the topoisomerase II mRNA expression in a collective of 21 patients by semiquantitative PCR. The PCR-assay and immunocytochemistry corresponded in 13 of 21 cases (62%).