Identification of a novel DR4 allele, DRB1*0442.

A new DRB1 allele encoding DR4, DRB1*0442, was identified in three Caucasian siblings by reverse in-line hybridization and defined by sequencing based typing. The DRB1*0442 allele differs from DRB1*0404 by a single nucleotide at position 227 (T-->A) of codon 47 in exon 2. At the amino acid level, this substitution results in a change from tyrosine to phenylalanine. Serologically, the new allele appears to retain the DR4 antigenicity; however, this substitution may affect peptide-binding specificity.

Production and pre-clinical significance of haematopoietic peptide growth factors (HPGF) in human non-seminomatous germ cell tumour cell lines.

Peptide growth factors involved in the regulation of haematopoiesis (HPGF), for example granulocyte-colony-stimulating factor (G-CSF) and granulocyte/macrophage-colony-stimulating factor (GM-CSF), are of clinical importance in the treatment of testicular germ cell tumour (GCT) patients with modern chemotherapy regimens since they ameliorate chemotherapy-induced neutropenia. Aberrant expression of and/or response to HPGF has been reported in several solid tumour types although no data are available on GCT with the exception of those on stem cell factor (SCF). The aims of this pre-clinical study were twofold: (1) to screen a panel of human non-seminomatous (NS)GCT for the production of HPGF and (2) to test the effects of G-CSF or SCF on the growth of NSGCT cell lines in vitro, and on the growth kinetics of two human NSGCT xenograft models. HPGF concentrations in cell culture supernatant from 11 NSGCT cell lines growing under routine culture conditions were measured by enzyme-linked immunosorbent assay. The growth kinetics of cell lines was quantified in vitro using the sulphorhodamine B assay. The growth kinetics of nude mouse NSGCT xenografts was followed by measuring tumour volumes every 2-3 days over days 1-30, following daily subcutaneous injection of nude mice (days 1-14). The cell lines produced G-CSF (1/11 cell lines), GM-CSF (2/11), SCF (2/11), M-CSF (6/11). and interleukin-6 (9/11). Growth stimulation of cell line H12.1 by SCF was observed in vitro, but no statistically significant differences in NSGCT xenograft tumour volume (VT) or relative VT (r VT) in treated groups were observed on days 14 or 29 compared to the control. The change in rVT of H12.1 xenografts treated with G-CSF alone compared to control (rVT/rVT,c) was 0.96 on day 29. The values for rVT/rVT,c for H12.1 xenografts treated with G-CSF in combination with low- or high-dose SCF were, respectively, 1.67 or 1.7 compared to 1.19 for SCF-treated mice. The results are in agreement with clinical data to date where no observations have been reported of stimulation or inhibition of tumours in patients receiving treatment with G-CSF. Before any clinical trials are initiated in GCT patients treated with G-CSF in combination with SCF, further pre-clinical experiments with this tumour type are recommended to investigate this phenomenon further in a greater number of NSGCT cell lines in vitro and in vivo and with a wider range of SCF/G-CSF schedules. The potential relevance of secretion of HPGF in NSGCT cell lines in vitro to the pathobiology of GCT in patients is also a subject of interest for future research.

The EWS/ATF1 fusion protein contains a dispersed activation domain that functions directly.

Naturally occurring chromosomal fusion of the Ewings Sarcoma Oncogene (EWS) to distinct cellular transcription factors, produces aberrant transcriptional activators that function as dominant oncogenes. In Malignant Melanoma of Soft Parts the N-terminal region of EWS is fused to C-terminal region of the cAMP-inducible transcription factor ATF1. The EWS/ATF1 fusion protein binds to ATF sites present in cAMP-responsive promoters via the ATF1 bZIP domain and activates transcription constitutively in a manner that is dependent on an activation domain (EAD) present in EWS. To further define the requirements for trans-activation we have performed mutational analysis of EWS/ATF1 in mammalian cells and report several new findings. First, trans-activation by EWS/ATF1 does not require dimerisation with other ATF family members present in mammalian cells. Second, in contrast to the earlier suggestion of an allosteric role, the EAD can act directly. Third, determinants of trans-activation are dispersed throughout the EAD and cooperate synergistically to produce potent trans-activation. We also report that the region of EWS containing the EAD can activate transcription in Yeast. This latter finding might enable a genetic approach to understanding the mechanism of transcriptional activation by EWS and development of high-throughput screens for EWS inhibitors.

Pre-clinical activity of taxol in non-seminomatous germ cell tumor cell lines and nude mouse xenografts.

Taxol (Paclitaxel) is a novel anti-cancer drug which has shown excellent clinical activity in a variety of solid tumors, particularly in metastatic breast and ovarian cancer. 70-80% of patients with metastatic non-seminomatous germ cell tumor (NSGCT) attain disease-free status with standard cisplatin-based combination chemotherapy but the emergence of drug resistance still prevents a small proportion of these patients from achieving long-term remission. Here we report the results of pre-clinical studies investigating whether taxol exhibits cross-resistance to cisplatin or ifosfamide in human NSGCT cell lines and in a cisplatin refractory xenograft model of human NSGCT. Following 96-h drug exposure in a 5-day sulphohodamine B (SRB) in vitro assay, taxol demonstrated potent cytotoxicity in cell lines which were cisplatin sensitive (577 LM, H32, H12.1; mean IC50s 1.5-3.0 nM) or those with acquired or intrinsic cisplatin resistance (H12DDP, H23.1; mean IC50s 2.5 nM). Compared to the drug-sensitive cell line, H12.1, the IC50 values of taxol were increased in cell line 1777NRp Cl-A with intermediate level resistance to cisplatin and ifosfamide (4.7 nM; p > 0.05) and significantly elevated in cell line 1411HP, with a high level of cisplatin resistance (6.9 nM; p < 0.01). The latter 2 cell lines may represent models corresponding to patients relapsing after high-dose platinum-based chemotherapy who seem to be resistant to taxol therapy. The IC50s of taxol in H32 and H12DDP were approximately 100-fold lower following drug exposure times exceeding 24 hours compared with short exposure times (1-6 h). Dose-dependent anti-tumor activity was observed with taxol in a cisplatin-refractory xenograft model of NSGCT (H23.1), with significant anti-tumor activity observed at a dose of 15 mg/kg/d injected intravenously on days 1 through 5. The results of this study are in accordance with the most recent clinical data which showed that taxol is a useful drug in relapsed or cisplatin-refractory testicular germ cell cancer, with significant anti-tumor activity being observed in 25% of patients, but poor activity in patients previously treated with high-dose therapy. Further pre-clinical research, especially using models such as 1411HP and 1777NRp Cl-A, on the combinations of taxol with other regimens are required to enable successful treatment of the most drug-resistant relapsed germ cell tumors.

Comparative cytotoxicity of oxaliplatin and cisplatin in non-seminomatous germ cell cancer cell lines.

Approximately 70-80% of patients with metastatic testicular cancer will become disease free with cisplatin-based chemotherapy and most of these patients will be long-term survivors. Despite these impressive results, the two limitations of cisplatin are its severe and potentially long-term side-effects, and the emergence of drug resistance which prevents a small proportion of these patients from achieving long-term remission. Oxaliplatin has an improved toxicity profile compared to cisplatin and contains the diaminocyclohexane (DACH) substituent known to be correlated with a lack of cross-resistance with cisplatin. A phase II study has shown interesting activity when used in combination with cisplatin in cisplatin-refractory testicular cancer patients. Here we report the results of the first in vitro study investigating whether oxaliplatin as a single agent exhibits cross-resistance to cisplatin in a panel of non-seminomatous germ cell tumor (NSGCT) cell lines using short and long-term drug exposures in a five-day sulfhodamine B in vitro cytotoxicity assay. Oxaliplatin cytotoxicity was significantly superior to cisplatin in cell lines with both acquired (H12DDP) and intrinsic (1777NRp Cl-A) intermediate level resistance to cisplatin. Following 24 h or 96 h drug exposure the fold resistance in H12DDP and 1777NRp Cl-A was 1.7-2.2 with oxaliplatin compared to 3.9-6.1 with cisplatin. The cytotoxic activity of oxaliplatin was not significantly different from that of cisplatin in cisplatin-sensitive cell lines or in cell lines with a high level (10-20 fold) of cisplatin resistance. The results of this study suggest that further preclinical studies in NSGCT are of interest, particularly in combination with cisplatin, ifosfamide and etoposide. Furthermore, the in vitro results support the use of an oxaliplatin administration schedule giving prolonged drug exposure, such as the flat or circadian rhythm-modulated schedule already under investigation for oxaliplatin.

Amifostine does not alter the antitumor activity of cisplatin in a pre-clinical model of testicular cancer.

Testicular germ cell tumors are so exquisitely sensitive to cisplatin that the majority of patients with this cancer are now cured with modern platinum-based chemotherapy. In contrast to some other tumor types, testicular germ cell tumors are known to express alkaline phosphatases (ALP). Amifostine is an aminothiol pro-drug which is rapidly dephosphorylated by ALP at the ell surface of healthy tissues and which exerts a clinically proven protective effect against chemotherapy associated toxicity. The aim of this pre-clinical study was to assess the potential of amifostine to protect platinum-sensitive non-seminomatous germ cell tumor (NSGCT) nude mouse xenografts established from an ALP-positive embryonal carcinoma (EC) cell line, from the cytotoxicity of cisplatin when both were administered at their individual maximally tolerated doses (MTD). The %T/C values calculated at day 30 for nude mice carrying H12.1 NSGCT xenografts treated with amifostine alone, amifostine plus cisplatin or cisplatin alone were, respectively, 93, 3 or 3%. Mean tumor volumes were not significantly different between mice treated with the combination versus cisplatin alone at day 14 or 30. The results of this study revealed no evidence of tumor protection by amifostine, confirming previous results in other tumor types.

Reversal of inherent multidrug-resistance in primary human renal cell carcinoma cell cultures by S 9788.

In a panel of 14 primary cultures of human renal cell carcinomas the reversal of inherent multidrug-resistance by S 9788, a new triazinoaminopiperidine derivative, was analysed. In combination with doxorubicin S 9788 revealed an evident reversal of multidrug resistance in 12 cell cultures. Two cell cultures remained unaffected. An association between reversal and P-glycoprotein (P-170) expression suggests that S 9788 exerts its activity through P-glycoprotein.

In vitro and in vivo circumvention of multidrug resistance by Servier 9788, a novel triazinoaminopiperidine derivative.

S 9788 is a novel triazinoaminopiperidine derivative which does not belong to any of the classes of compounds known to reverse multidrug resistance (MDR). S 9788 was far more potent than verapamil (VRP) in reversing resistance to adriamycin (ADR) in the ADR-selected murine leukaemia cell lines P388/ADR-1 and P388/ADR-10, and the human chronic myelogenous leukaemia K562/R. Fold reversion with S 9788 (5 microM) was, respectively, 3.5, 5.4 and 11.3 times greater than that with VRP (5 microM). S 9788 was also a more potent reversant of ADR resistance in the intrinsically resistant human colon adenocarcinoma COLO 320DM (2.3 fold), and of vincristine (VCR) resistance in the human MDR1 gene-transfected squamous lung carcinoma line S1/tMDR1 (5.6 fold). The activity of S 9788 depended on both the MDR cell line and the cytotoxic agent. S 9788 (50-100 mg/kg/d) administered IP once a day on days 1-4 resulted in a dose-dependent increase in the chemotherapeutic effect of VCR (0.25 mg/kg/d) in P388/VCR - bearing mice and ADR (4 mg/kg/d) in P388/ADR - bearing mice. Increases in antitumor activity were (% T/C) of +20-34% in the P388/ADR model and + 50-78% in the P388/VCR model with respect to cytotoxic agent treatment alone. S 9788 appeared to be devoid of toxicity at its effective doses. The mechanism of action of S 9788 is unknown but S 9788 (0.5-10 microM) induced a dose-dependent increase in ADR accumulation in KB-Al cells and compared to verapamil its effect was twice as active and approximately seven times more potent. We conclude that S 9788 is a novel agent capable of reversing MDR in vitro and in vivo, and whose pharmacological profile warrants its selection as a candidate drug for eventual assessment in the clinic.