Increased expression of the multidrug-resistance gene in undifferentiated sarcoma

Hepatic tumors in children

Although they account for only 1% to 4% of solid tumors in children, hepatic tumors and pseudotumors offer a diagnostic challenge to the clinician seeing only an occasional case. Metastatic lesions such as neuroblastoma, Wilms' tumor, and lymphoma are the most common neoplasm seen in the liver, but 10 distinct primary tumors and pseudotumors of the liver occur with some regularity, and a few others may be seen rarely, including leiomyosarcoma, rhabdoid tumor, and endodermal sinus tumor. Five of these neoplasms--hepatoblastoma, infantile hemangio-endothelioma, mesenchymal hamartoma, undifferentiated embryonal sarcoma, and embryonal rhabdomyosarcoma of the biliary tree--occur only in children and are the major focus of the article.

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.

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.

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.

Cytopathology of undifferentiated (embryonal) sarcoma of the liver

We have studied one undifferentiated (embryonal) sarcoma of the liver (USL) by fine-needle aspiration cytology (FNAC) and have correlated the cytologic findings with those seen in the histologic sections. The main cytologic and immunocytochemical features were: cellular aspirates, mesenchymal clusters, disparity in individual cell size (small round cells, and multinucleated giant cells, sometimes bizarre), absence of biliary pigment, AFP-negative and vimentin-negative tumor cells, AFP-negative and PAS-positive hyaline globules, and apoptotic cells. Only immunostaining for alpha-1-antitrypsin, alpha-1-antichymotrypsin, and carcinoembryonic antigen were positive in tumor cells in histologic sections. The differential diagnosis should be carried out with rhabdomyosarcomas, hepatoblastomas, malignant fibrous histiocytomas, and poorly differentiated hepatocarcinomas. We think that the cytologic features observed in this case, evaluated both in the appropriate clinical context and in the light of the laboratory findings, may permit the correct diagnosis of this infrequent liver tumor. Nevertheless, more cases need to be studied to assess the reliability of our findings.

Expression of MDR1/P glycoprotein in human sarcomas

Conflicting reports of MDR1 gene expression in human tumours are observed according to whether studies are performed at the mRNA or P-glycoprotein level. We have investigated this expression in 22 clinically drug-resistant sarcomas at the mRNA level by Northern blot (NB), Dot blot (DB), in situ hybridisation (ISH), and at the protein level by immunohistochemistry (IHC) using three monoclonal antibodies (MoAbs): C219, JSB1, MRK16. Increased MDR1 mRNA expression was detected by NB, DB, and ISH in 1/22 sarcoma (an Ewing's sarcoma). ISH was perfectly correlated with DB hybridisation and confirmed the expression of tumoral cells alone. Specific staining of 100% of tumoral cells was obtained with the three MoAbs in the same sarcoma. Expression in tumoral cells of 12 other sarcomas was detected with MRK16, and positive staining of stromal cells with both C219 (1/22) and MRK16 (8/22) was observed. This study confirms that MDR1 overexpression occurs in human sarcomas but is not the principal mechanism of drug-resistance. Furthermore, positivity with one antibody does not necessarily imply the presence of P glycoprotein (P-gp) and a disparity may exist between the levels of P-gp and its mRNA in the same sample. So care must be taken in interpreting results and more sensitive techniques such as the polymerase chain reaction (PCR) could prove useful.

Human cell lines as models for multidrug resistance in solid tumours

In spite of our expanding knowledge on the molecular biology of cancer, relatively little progress has been made in improving therapy for the solid tumours which are major killers, e.g., lung, colon, breast. Significant advances over the past 10-15 years in chemotherapy of some tumours such as testicular cancer and some leukaemias indicates that, in spite of the undesirable side-effects, chemotherapy has the potential to effect cure in the majority of patients with certain types of cancer. Multidrug resistance, inherent or acquired, is one important limiting factor in extending this success to most solid tumours. In vitro studies described in this review are now uncovering a diversity of possible mechanisms of cross-resistance to different types of drug. Sensitive methods such as immunocytochemistry, RT-PCR or in situ RNA hybridisation may be necessary to identify corresponding changes in clinical material. Only by classifying individual tumours according to their specific resistance mechanisms will it be possible to define the multidrug resistance problem properly. Such rigorous definition is a prerequisite to design (and choice on an individual basis) of specific therapies suited to individual patients. Since a much larger proportion of cancer biopsies should be susceptible to accurate analysis by the immunochemical and molecular biological techniques described above than to direct assessment of drug response, it seems reasonable to hope that this approach will succeed in improving results for cancer chemotherapy of solid tumours where other approaches such as individualised in vitro chemosensitivity testing have essentially failed. Results from clinical trials using cyclosporin A or verapamil are encouraging, but these agents are far from ideal, and reverse resistance in only a subset of resistant tumours. Proper definition of the other mechanisms of MDR, and how to antagonize them, is an urgent research priority.

Expression of MDR1 and GST-pi in human soft tissue sarcomas: relation to drug resistance and biological aggressiveness

Human soft tissue sarcomas (HSTS) in adults are a family of mesenchymal tumors characterized by high biological aggressiveness and general refractoriness to chemotherapy. A series of 36 HSTS, 24 untreated and 12 homogeneously treated with a presurgical chemotherapeutic regimen consisting of doxorubicin (intra-arterial) and iphosphamide (intra-vein), was analyzed for expression of MDR1 and the glutathione-S-transferase-pi (GST-pi) gene in order to identify molecular phenomena which may be implicated in the chemoresistance displayed by these tumors. The MDR1 gene was expressed in a greater percentage of drug-treated tumors and at higher levels than in untreated ones. By contrast, chemotherapeutic treatment has no effect on GST-pi mRNA expression. The GST-pi expression level (EL) was much higher in the HSTS with biologically aggressive features. In fact, significant correlations were observed between GST-pi and histologic grade (p = 0.01); aneuploidy (p less than 0.01); and histone H3 EL (p = 0.01), suggesting a possible causal relationship between GST-pi activity and biological aggressiveness in HSTS.