MRP expression of testicular cancers and its clinical relevance.

BACKGROUND: The expression of a multidrug resistance associated protein (MRP) has been investigated in a variety of human tumors. However, there is a lack of data regarding its expression in germ cell testicular tumors (GCTTs). PATIENTS AND METHODS: MRP expression was examined by immunohistochemistry (IHC) using mouse monoclonal antibody (MRPm6) against human MRP in 56 testis cancer specimens. This antigen was also correlated with the histology, metastatic behavior, clinical stage and tumor suppressor protein p53 immunostaining of GCTTs. RESULTS: All testis tumors, regardless of their histology, metastatic status and clinical stage gave positive signals. MRP was positive not only in the cytoplasm but, very interestingly, in the nuclei. CONCLUSION: Our results suggested that ala GCTTs express high levels of MRP protein with no relation to any of clinicopathological variables investigated here. Since germ cell tumors are very sensitive to chemotherapy, the role of MRP as mediator of drug resistance seems unconvincing in this malignancy. MRP is located in the cytoplasm and the nuclei of tumor cells and may be involved in transportation and/or redistribution certain substrates from the nucleus to the cytoplasm.

mdm-2 expression in human testicular germ-cell tumors and its clinical value.

BACKGROUND: In germ cell testicular tumors (GCTT) mdm-2 gene was analyzed for amplification and transcripts but not for protein. The purpose of this study is to determine whether mdm-2 protein level is aberrant in GCTT and if so, what is the relationship between mdm-2 overexpression and other disease parameters including histologic subtypes, p53 status, metastatic potential and clinical stage. METHODS: 81 testicular germ-cell tumors were screened for their mdm-2 expression at the protein levels using immunohistochemistry (IHC) and Western blot (WB) analysis. RESULTS: Of 81 GCTTs 45 (55.55%) showed mdm-2 nuclear immunoreactivity, 34 (41.97%) of which were strongly positive. The incidence of mdm-2 immunostaining was significantly higher (P = 0.0007) in non-seminomas (NSGCT) than in seminomas (SGCT). The frequency of positive tumor was higher in tumors from metastatic patients than in tumors from metastatic-free patients (P = 0.011). mdm-2 expression was detected significantly more frequently in tumors of advanced stages, i.e. IIB, IIC and III versus tumors of early stages (I and II/A) (P = 0.0098). A significant difference between the three stages of disease as to the expression of mdm-2 (chi 2 = 0.0386) could be established, namely the incidence of mdm-2 expression increased with an increase in stage. Using Westem blotting 22 (68.75%) out of 32 tumors overexpressed the mdm-2 oncoprotein of 90 kd (p90). CONCLUSIONS: mdm-2 expression as detected by immunohistochemistry may provide a reliable prognostic tool to isolate subgroups of patients with more aggressive GCTT.

Drug resistance and sensitivity of germ cell testicular tumors: evaluation of clinical relevance of MDR1/Pgp, p53, and metallothionein (MT) proteins.

BACKGROUND: Although in vitro and clinical studies indicate that overexpression of P-glycoprotein (Pgp), p53, or metallothionein (MT) is involved in modulating drug resistance/sensitivity of cancer cells, the clinical relevance of the overexpression remains to be elucidated. MATERIALS AND METHODS: In this paper the expression and clinical value of Pgp, p53, and MT were evaluated immunohistochemically in 77 specimens of germ cell testicular tumors (GCT). We also studied the interrelationship(s) between the investigated markers. RESULTS: Pgp positivity correlated with cancers of advanced stages (P = 0.000). p53 and MT immunostaining does not predict a poor response to chemotherapy, but rather is correlated to a favorable clinical outcome (P = 0.001, P = 0.00006 respectively). We obtained an inverse association between Pgp and p53 (P = 0.0005), and positive strong association between p53 and MT immunoreactivity (P = 0.0002). CONCLUSIONS: Based on our results in patients with germ cell testicular tumors we assume that the poor clinical outcome seen in certain Pgp positive tumors is the consequence of Pgp association with a more progressive malignant phenotype, rather than its role in multidrug resistance (MDR). p53 and MT immunoreactivity predicts a better response rate to chemotherapy, wheres tumors lacking or demonstrating low MT and or p53 expression show a worse prognosis.

Differential expression of glutathione S-transferases in germ cell tumors of human testes.

Glutathione S-transferase (GST) isoenzymes alfa, mu and pi were assessed by Western blotting in normal testes, seminomas and non-seminomatous germ cell tumors (NSGCTs). GST alfa and mu were strongly expressed in all normal specimens (n = 6), the pi isoform, however, could not or barely be detected. Ten (92%) of 11 seminomas had GST pi and only 2 (16%) showed alfa expression. In contrast, twelve (80%) of 15 NSGCTs showed a significant level of GST alfa and only 2 (13%) had GST pi expression. The absence or paucity of mu isoform was characteristic for all neoplastic testicular tissues. A statistically significant relationship (P = 0.021) could be established between GST alfa and stages of disease, i.e., alfa isoform was prevalent in the later stage (IIB, III) NSGCT tumors. These results suggest that the poor prognosis of the later stage NSGCTs may be due to their high GST alfa content, while the GST pi does not seem to have role in this relation.

Expression of bcl-2 in testicular carcinoma: correlation with tumor progression and MDR1/Pgp.

BACKGROUND: The expression of bcl-2 has been studied extensively in a variety of human tumors. However, there is a lack of clinical data regarding its expression in germ cell testicular tumors (GCTTs). METHODS: In this study, the authors screened 70 patients with GCTTs for bcl-2 expression using immunohistochemistry (IHC) and the streptavidin-biotin-alkaline phosphatase method. This expression was also correlated with the metastatic behavior, clinical stages, and multidrug resistance gene product protein (MDR1/Pgp) immunostaining of GCTTs. RESULTS: Overall, 41 carcinomas (58%) stained positively with anti-bcl-2 monoclonal antibody. According to histologic type, these lesions with positive staining included 11 of 26 seminomas (42.3%) and 30 of 44 nonseminomatous germ cell testicular tumors (NSGCTs) (68%). The incidence of bcl-2 immunostaining was higher (P = 0.05, two-tailed Fisher's exact test) among NSGCTs than among seminomas. The expression of bcl-2 was more prevalent among tumors from patients with metastases than among tumors from metastasis free patients (P = 0.000). There was a significant difference between the three stages of disease in the expression of bcl-2 (chi2 = 0.000), i.e., bcl-2 expression was clearly dominant among tumors at advanced stages. A significant association between bcl-2 and Pgp immunostaining was established (P = 0.004). CONCLUSIONS: These findings revealed that bcl-2 expression occurs in GCTTs. Furthermore, they suggest that bcl-2 is associated with a more advanced malignant phenotype of this tumor.

Do metallothioneins affect the response to treatment in testis cancers?

PURPOSE: Data on the involvement of elevated metallothionein (MT) expression in resistance to some of the commonly used anticancer treatments are scattered and conflicting. This encouraged us to examine further the contribution of metallothionein expression to the development of this resistance phenotype. PATIENTS AND METHODS: Formalin-fixed, paraffin-embedded blocks of primary untreated germ cell testicular tumor specimens, obtained from 77 patients following radical orchiectomy, were examined for their MT expression using monoclonal antibody and immunohistochemistry. Clinical staging, the chemotherapeutic schedule and evaluation of response to treatment (defining objective response) were performed according to UICC criteria. RESULTS: All tumor types, including seminomas and nonseminomas, expressed MT, regardless of their histology and clinical stage. The immunoreactivity of MT showed a significant positive correlation with the clinical sensitivity of cancer to antitumor therapy (P = 0.0001). CONCLUSION: In patients with germ cell testicular tumors, high MT expression, as detected by immunohistochemistry, predicts a better response rate to chemotherapy whereas tumors lacking or demonstrating low MT expression show a worse prognosis. These data do not support the hypothesis that MT overexpression contributes to cisplatinum resistance, at least in this tumor type.

Is p53 expression, detected by immunohistochemistry, an important parameter of response to treatment in testis cancer?

BACKGROUND: Several prior studies revealed positive p53 expression via immunohistochemistry (IHC) in a large percentage of germ cell testicular cancers (GCTTs). However, the predicting and prognostic value of this protein remains to be defined. Therefore, the aim of our study was to further clarify the role of p53 protein in GCTTs and to look for correlations between its gene expression and other disease parameters, including histological subtype, stage and clinical resistance sensitivity. Furthermore, we correlated p53 protein expression with that of MDRI gene product protein (Pgp) in order to examine the interrelationship between these two markers. PATIENTS AND METHODS: 77 untreated patients with GCTTs were investigated for their p53 expression using monoclonal antibody and immunohistochemistry in paraffin-embedded specimens. There were 34 patients with stage I, 16 with stage II, 27 with stage III disease. RESULTS: All tumor types, except differentiated teratomas, were immunoreactive for p53 to a various extent ranging from scarcely positive to homogeneously stained tumor cells. Seminomas (S) and embryonal carcinoma (EC) components showed the most positive nuclear staining. p53 expression showed a significant inverse correlation with the stage of disease (P < 0.0003). There was a significant positive relationship between p53 immunoreactivity and response to treatment (P = 0.0012), i.e. high levels of p53 expression correlated with clinical sensitivity of the tumors to chemotherapy. We could demonstrate a statistically significant opposite relationship between p53 and Pgp immunoreactivity (P < 0.0005). CONCLUSION: Our results show that p53 status in tumor cells may be a strong determinate of susceptibility to chemotherapy and that p53 overexpression has a favorable prognosis in terms of response to treatment in GCTTs. Moreover, the findings provide clinical evidence for the presense of significant relationship between p53 and MDR1/Pgp immunoreactivity. They also suggest that patients resistant to chemotherapy and lacking p53 expression might benefit from an alternative appropriately designed chemotherapeutic regimen to achieve further successful treatment in GCTTs.

[Metallothionein expression as a marker of therapeutic sensitivity in the early stages of testicular cancer]. / Metallothionein, mint a korai stádiumú hererákok terápiás érzékenységének mutatója.

Data concerning the involvement of elevated metallothionein (MT) expression in drug resistance are obviously scattered and contrasting. The presence of the MT gene product protein was screened in 51 untreated human germ cell testicular tumours, furthermore a relationship between MT expression and clinical resistance was investigated. Using monoclonal antibody and immunoenzyme staining elevated MT level could be demonstrated in nuclei and cytoplasm of both seminomas and non seminomatous germ cell testis tumours. Thirty-one tumours (61%) showed extensive, 15 (29%) focal positive staining. In contrast teratomas expressed this antigen negatively or scarcely. The highest level of MT was stated in early stages (I, IIA) compared with progressed stages (IIB, III) (p = 0.0004). Between the high level of MT and clinical resistance a converse correlation could be shown because the resistant tumours expressed no or low, while the sensitive tumours significantly high level of MT protein which can be used as an useful marker to identify patient subgroups sensitive to anticancer therapy, at least in testis tumours.

[Correlation between p-53 expression and clinical resistance in testicular cancer]. / A p-53 expresszió és a klinikai rezisztencia összefüggésének vizsgálata hererákokban.

One of the most common cellular gene which negatively regulates the cell cycle, thus functioning as tumour suppressor gene, is the p-53 gene. The presence of this mutated gene has been correlated with, the aggressiveness of several malignant neoplasmas. Expression of the p-53 gene product protein was screened in 55 untreated human germ cell testicular tumours, furthermore a relationship between p-53 expression and clinical resistance was investigated. Using monoclonal antibody and immunoenzyme staining elevated p-53 level could be demonstrated in nuclei of embryonal carcinoma (84%) and seminoma components (56%). Most of the choriocarcinoma cases showed positive staining. Teratomas expressed this antigen negatively or scarcely. In seminomas the highest level of p-53 was stated in stage I. In contrast the opposite tendency could be demonstrated in embryonal carcinomas where p-53 was ++ positive in stage III. Between the high level of p-53 and clinical resistance a converse correlation could be stated because the resistant tumours expressed no or low, the sensitive tumours high level of p-53 protein (P 0.01). These results suggest that elevated p-53 expression could be a prognostic marker of sensitivity in testis cancer.

Glutathione related enzymes in human testicular germ cell tumors and normal testes.

In this study, the activity of the glutathione related enzymes, namely glutathione S-transferase (GST), glutathione reductase (GSSG-R), Selenium-dependent and -independent glutathione peroxidase (GPX) of various TGC tumors (n = 18) obtained from untreated patients, was compared to that of the corresponding enzymes of normal testicular tissues (n = 5). The enzymes of all tumorous tissues except teratomas were significantly less active, than the corresponding enzymes of nontumorous tissues. The GST was in seminomas 4.3-20-, in embryonal carcinomas 47-, and in mixed tumors 13-47-fold less active than in the normal testes. The GST activity of teratomas was about half of that of the normal tissues. The Se-independent GPX, component of GST alfa class, comprised about 90 percent of the total GPX activity in normal testis; however it was absent or barely detectable in all TGC tumors except teratomas. The latter had about the same GPX activity as the tumor-free testicular tissues. Apart from the teratoma, the GSSG-R activity of all TGC tumors was also suppressed to about one third of that of the normal testis. The insufficient function of glutathione related enzymes of TGC tumors may contribute to their sensitivity against treatment. The poorer prognosis of teratomas, however, may be explained by the relatively higher activity of their detoxifying enzymes.

Severe depletion of cellular thiols and glutathione-related enzymes of a carmustine-resistant L1210 strain associates with collateral sensitivity to cyclophosphamide.

Cyclophosphamide (CPA) increased the life span of both carmustine (BCNU)-resistant (L1210/BCNU) and BCNU-sensitive L1210 (L1210/0) leukaemic mice; their sensitivity to CPA, however, was extremely different. The BCNU-resistant strain was much more sensitive (collaterally) to CPA than was its sensitive counterpart. The collateral sensitivity was accompanied by a severe reduction in the activity of glutathione-related enzymes and in protein thiol (SH) and non-protein SH levels in BCNU-resistant cells. The activity of glutathione reductase (GSSG-R) was 2 times higher in the L1210/0 cells than in the L1210/BCNU cells. Glutathione-S-transferase (GST) was also almost 2 times more active in the sensitive cells than in the resistant strain. To develop resistance against CPA with a single treatment (60 mg/kg) per passage, the L1210/BCNU strain needed 26 passages, whereas the L1210/0 strain required significantly fewer. The resistance developed against CPA was associated with a moderate elevation of thiols in the L1210/CPA cells, whereas this elevation was approximately 3 times more pronounced in the L1210/BCNU/CPA cells. The severely reduced activity of GST in the L1210/BCNU strain was markedly increased when these cells were made resistant to CPA; the GSSG-R activity, however, remained low, suggesting an irreversible injury of this enzyme by BCNU.

Benzamide potentiation of the cytotoxicity of bifunctional galactitol [correction of galacticol] in resistant P388 leukemia correlates with inhibition of DNA ligase II.

Benzamide (BA) enhances the cytotoxicity of 1,2:5,6-dianhydrogalactitol (DAG) in resistant P388 leukemia cell lines but not in the sensitive parent line. To examine the reason for this difference in response, we carried out an alkaline elution assay using proteinase K to study DNA interstrand cross-linking. At early time points, equal concentrations of DAG produced the same level of interstrand cross-linking (ICL) in the resistant and sensitive P388 leukemic cells, although marked differences were observed in their cytotoxicity toward the two cell lines. In the sensitive cells, neither the amount of DNA cross-linking nor the cytotoxicity changed during the observation period (38 h) in either the presence or the absence of BA. In contrast, the elution rate of the DNA of DAG-treated resistant cells increased with time and had reached the control levels by 38 h. However, when these cells were postincubated with BA for 38 h, the elution rate of DNA was much faster than that observed for the untreated resistant cells, indicating an accumulation of DNA single-strand breaks (SSB). The SSB accumulation caused by BA was associated with an inhibition of the activity of ligase II enzyme, which was stimulated when resistant cells were treated with DAG alone. The potentiating effect of BA on the resistant cells can thus be related to the inhibiting action of BA on the DNA-rejoining enzyme, ligase II. The lack of sensitization by BA of the DAG-treated parent cell line may be attributable to the absence of DNA-SSB formation, which is necessary for ligase II activation through the stimulation of poly(ADP-ribose) synthesis.

Absence of cross-resistance between two alkylating agents: BCNU vs bifunctional galactitol.

Dianhydrogalactitol (DAG) increased the life span of both BCNU-sensitive and -resistant L1210 tumor-bearing mice. However, the BCNU-resistant strain showed slightly lower sensitivity against DAG, which could be overcome by an increase in drug dose of ca. 20%. The somewhat lower sensitivity was proportional to a slightly reduced DNA cross-linking formation induced by DAG in BCNU-resistant cells. The amount of DNA cross-links was determined by measurement of the 1,6-di(guaninyl)-galactitol content of DNA. The slight reduction in cross-links is not attributable to DNA repair but rather to other factors that seem to prevent the formation of DNA-drug adducts. The absence of cross-resistance is explained by different kinds of DNA damage caused by the two alkylating agents and the presumably different defense mechanisms developed by cells against these lesions.

Identification of guanine and adenine adducts in DNA alkylated by dibromodulcitol in vitro and in vivo.

DNA reacted with dibromodulcitol in neutral solution yielded 3- and 7-alkyl substituted purines after hydrolysis at neutral pH-value at 37 degrees C. The alkylated products were identified by mass spectrometry and by comparison of their UV absorption spectra and chromatographic properties on thin-layer chromatography (TLC) and various columns with those of the corresponding galactitylpurine derivatives obtained by synthetic route from alkylation of the appropriate nucleic bases or nucleosides. The labelled alkylpurines occurring in DNA of Yoshida tumour cells treated with [3H]dibromodulcitol in vivo were also identified by co-chromatography of labelled DNA hydrolysate with synthetic 3- and 7-alkyl substituted purines. On the basis of the same chromatographic behaviour 3-(1-deoxy-3,6-anhydrogalactit-1-yl)adenine, 7-(1-deoxygalactit-1-yl)guanine, 7-(1-deoxy-3,6-anhydrogalactit-1-yl)guanine and 1,6-di(guanin-7-yl)-1,6-dideoxygalactitol were identified as main alkylated products in tumor cell DNA after in vivo treatment with dibromodulcitol.

In vivo study on alkylation site in DNA by the bifunctional dianhydrogalactitol.

In vivo alkylation of Yoshida sarcoma cell DNA by 3H-labelled 1,2:5,6-dianhydrogalactitol (DAG) yielded N-7 monogalactitylguanines and 1,6-di-(guanin-7-yl)-galactitol, similar to the alkylated products obtained by in vitro reaction of DNA with dianhydrogalactitol in neutral solution. The ratio between monoalkylguanines and diguaninyl product was 2-2.5, slightly increasing with doses. Persistence of alkylated products in DNA was followed in function of time. There was no significant loss of either monoalkylated bases or diguaninyl derivative during the observation period i.e. 7-24 h after treatment. In contrast, the physical measurements of the amount of renaturable DNA showed a rapid opening of cross-links in the same period. Taking the presence of diguaninyl moiety as an indicator of cross-links in DNA, these two latter findings show an apparent contradiction which could be reconciled however by the mechanism proposed by Reid and Walker (Biochim. Biophys. Acta, 179 (1969) 179) for the removal of cross-linkage induced by HN2. Accordingly, one arm of the cross-links is removed, probably enzymically, leaving the DNA non-renaturable, while the other arm of cross-link is still covalently attached to the DNA molecule rendering possible the detection of diguaninyl moiety in DNA at some later time. This concept for the removal of cross-links from DNA seems to be supported by our results too.

Alkylation by 1,2:5,6-dianhydrogalactitol of deoxyribonucleic acid and guanosine.

DNA was alkylated in neutral solution at 37 degrees C with 1,2:5,6-dianhydrogalactitol and hydrolysed to yield two principal products, identified as 7-galactitylguanine and 1,6-dideoxy-1,6-di(guanin-7-yl)galactitol. The reaction products were separated by chromatography on Sephadex G-10 and Dowex 50 (H+ form). The two compounds were also obtained by reaction between dianhydrogalactitol and guanosine in acetic acid. The products were characterized from their u.v.-spectral data by comparison with those of the 7-alkylguanines and were also identified by mass spectrometry.

Complex evaluation of the effect of some cytostatic hexitol derivatives.

The antitumor effect of three structurally closely related alkylating hexitol derivatives (DBD, DAG, DiacDAG) was evaluated using a complex multi-parameter evaluation system. It comprised toxicology, action on ascites and solid tumors, as well as on subpopulations isolated by isopyknic centrifugation, cross-resistance and their action on chromatin components (DNA, histone, nonhistone proteins). The results indicate that in spite of their same mode of action, considerable differences could be observed in tumor specificity, inhibition of tumor growth and in their interaction with chromatin components. This multiparameter system seems to be very useful for comparative studies of other alkylating agents, especially for the evaluation of the effect of chemically closely related compounds.

The interaction of dianhydrogalactitol with DNA in cultured Yoshida sarcoma cells.

Using alkaline sucrose gradient sedimentation centrifugation it was found that treatment of Yoshida sarcoma cells in culture for 1 h with increasing concentrations of dianhydrogalactitol (DAG) enhanced the sedimentation rate of DNA in a dose-dependent manner. There was no difference between the amount of protein which co-sedimented with DNA released from treated and untreated cells. When DNA was extracted from the cells using a p-amino-salicylate-phenol mixture, the protein content of DNA seemed not to be affected by DAG. The possibility that DAG could form interstrand cross-linking in cellular DNA was suggested from renaturation studies. The appearance of a fast sedimenting DNA in the alkaline sucrose gradient and the evidence for a cross-linked DNA detected by renaturation technique, only appeared later than 6 h after treatment. A similar delayed effect on the depression in the rate of DNA synthesis was also observed. These data suggest that the inhibition of DNA synthesis may be related to the delayed formation of DNA interstrand cross-linked.

The effect of dibromodulcitol on the template activity of DNA chromatin and nuclei from Yoshida sarcoma cells.

It has been shown earlier that after in vivo administration, dibromodulcitol (DBD) reacts with DNA and to a greater extent with chromosomal proteins of Yoshida sarcoma cells. The present experiments were designed to show if the binding of DBD to the chromatin elements of Yoshida sarcoma cells causes any changes in RNA synthesis using either DNA or chromatin as template in bacterial RNA polymerase system. During 4 to 24 h following in vivo administration, DBD reduces the template activity of dna without detectable single-strand breaks in the template DNA in alkaline sucrose gradients. Using chromatin as template the same dose of DBD produces no or very slight inhibition of RNA synthesis. Measuring the DNA-dependent RNA synthesis in nuclei isolated from Yoshida cells of treated rats, the dose of DBD which markedly inhibited the template activity of DNA, resulted in a significant stimulation of the nuclear RNA synthesis. The increased RNA synthesis was not due to an inhibition of ribonuclease activity. The observed alterations of the transcriptive properties of chromatin and nuclei produced by DBD are interpreted as being due to a modification of the whole nucleoprotein structure caused by the interaction of DBD with both DNA and chromosomal proteins.

Effect of methyl methanesulphonate (MMS) and methylene dimethanesulphonate (MDMS) on the template activity of DNA isolated from MDMS-sensitive and -resistant Yoshida cells.

Both methylene dimethanesulphonate (MDMS) and methyl methanesulphonate (MMS) cause the template activity of Yoshida cell DNA to decrease in a dose-dependent manner. The MDMS-resistant subline of Yoshida tumour is less sensitive in terms of DNA template activity than the MDMS-sensitive subline towards both agents. Although the difference in sensitivity is not reflected in the survival data after each agent, it does suggest that the DNA from each cell line differs in its capacity to function as an efficient template.