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S Seeber

Publications and source records attributed to S Seeber.

At least 37 records · Page 2Linked to original sources
PubMed2001

High-dose chemotherapy with peripheral blood stem cell transplantation for patients with advanced ovarian cancer.

PURPOSE: We report the results of high-dose chemotherapy (HDC) with peripheral blood stem cell transplantation in twenty-one patients with primarily advanced or relapsed ovarian cancer. METHODS: Twenty-five women underwent stem cell collection, and 21 were finally treated with different regimens of HDC containing cyclophosphamide, etoposide, carboplatin, and treosulfan. The patients received cyclophosphamide +/- cisplatin and cisplatin + paclitaxel, respectively, followed by G-CSF (n = 24) or GM-CSF (n = 1) for stem cell mobilization. RESULTS: A mean of 7.2 +/- 6.1 x 10(6) CD34+ cells per kg bw were collected. Thirteen patients received double transplants and one patient received a triple transplant. The median age was 47 years (range 24-61 years) and the mean number of prior regimens was three (range 1-8). Engraftment occurred on time in all patients and there was one treatment-related death resulting in an overall mortality rate of 4.8% among the 21 patients treated with HDC. The response rate was 72% (48% CR, 24% PR) and the mean time to progression and overall survival after HDC were 7 and 32 months, respectively. CONCLUSION: HDC could be performed safely in patients with advanced ovarian cancer. However, even with a high response rate, the duration of response is short, warranting new treatment approaches to further improve the outcome of this population of patients with unfavorable prognosis.

Adult↗
PubMed2001

Digital imaging microscopy of firefly luciferase activity to directly monitor differences in cell transduction efficiencies between AdCMVLuc and Ad5LucRGD vectors having different cell binding properties.

The luciferase reporter gene incorporated into adenoviral vectors is very useful for monitoring viral transduction of different cell types or for comparing the transduction efficiency of different viral constructs of one cell type. Luciferase protein expression can be detected and quantified with very high sensitivity from whole cells or organ extracts. However, its disadvantages become obvious when aiming at evaluation of transduction events at the single cell level. The results obtained from whole cell extracts cannot be directly correlated to single cell events. In this paper direct cellular luciferase imaging using cell permeable luciferin substrates is applied for comparative analysis of cellular transduction events by two adenoviral vectors with different cell binding properties. Using digital imaging microscopy we show a more than ten-fold increase in transduction efficiency by Ad5LucRGD vectors versus AdCMVLuc vectors on human A549 cells.

Adenoviridae↗
PubMed2001

Evaluation of different methods for the detection of minimal residual disease in blood and bone marrow of patients with primary breast cancer: importance for clinical use?

We studied cytokeratin-positive (CK+) cells in the bone marrow (BM) and tumor markers (TM) in the blood of 128 patients with primary breast cancer in order to obtain an early diagnosis of residual disease. CK+ cells of two BM aspirations were detected by immunocytochemistry (IC). To evaluate the usefulness of immunomagnetic separation (IMS) for tumor cell enrichment in clinical samples, IMS was performed prior to IC and compared with the results for IC alone. The overall CK+ rate was 34% (44/128 patients), 29% (15/51) for patients with T1 tumors, 33% (28/84) for N0 patients and 31% (26/82) for patients with G1-2 breast carcinoma. Interestingly, 67% of CK+ patients were only positive in one of the two aspirates studied. A comparison between IC alone and IMS/IC could be performed in 70/128 patients (28/70 CK+). In 6/28 patients, CK+ cells were detected by both methods, in 16/28 patients only by IC and in 6/28 patients only by IMS. At least one TM, including carcinoembryonic antigen, carbohydrate antigen 15-3 and tissue polypeptide antigen, was increased in 58/128 (45%) patients [21/58 (36%) were CK+ in the BM]. Surprisingly, levels for the extracellular domain of Her-2/neu in serum samples were within the normal range in every patient studied. After a 2-year follow-up, 7/128 patients relapsed (3/7 CK+/TM-; 2/7 CK-/TM+; 2/7 CK-/TM-). We conclude that studying two BM aspirates for CK+ cells by IC in combination with TM determination is useful for identifying patients with a higher risk for relapse, however, tumor cell enrichment techniques will have to be improved for clinical use.

Adult↗
PubMed2001

Protection of hematopoietic cells from O(6)-alkylation damage by O(6)-methylguanine DNA methyltransferase gene transfer: studies with different O(6)-alkylating agents and retroviral backbones.

Overexpression of O(6)-methylguanine DNA methyltransferase (MGMT) can protect hematopoietic cells from O(6)-alkylation damage. To identify possible clinical applications of this technology we compared the effect of MGMT gene transfer on the hematotoxicity induced by different O(6)-alkylating agents in clinical use: the chloroethylnitrosoureas ACNU, BCNU, CCNU and the tetrazine derivative temozolomide. In addition, various retroviral vectors expressing the MGMT-cDNA were investigated to identify optimal viral backbones for hematoprotection by MGMT expression. Protection from ACNU, BCNU, CCNU or temozolomide toxicity was evaluated utilizing a Moloney murine leukemia virus-based retroviral vector (N2/Zip-PGK-MGMT) to transduce primary murine bone marrow cells. Increased resistance in murine colony-forming units (CFU) was demonstrated for all four drugs. In comparison to mock-transduced controls, after transduction with N2/Zip-PGK-MGMT the IC50 for CFU increased on average 4.7-fold for ACNU, 2.5-fold for BCNU, 6.3-fold for CCNU and 1.5-fold for temozolomide. To study the effect of the retroviral backbone on hematoprotection various vectors expressing the human MGMT-cDNA from a murine embryonic sarcoma virus LTR (MSCV-MGMT) or a hybrid spleen focus-forming/murine embryonic sarcoma virus LTR (SF1-MGMT) were compared with the N2/Zip-PGK-MGMT vector. While all vectors increased resistance of transduced human CFU to ACNU, the SF1-MGMT construct was most efficient especially at high ACNU concentrations (8-12 microg/ml). Similar results were obtained for protection of murine high-proliferative-potential colony-forming cells. These data may help to optimize treatment design and retroviral constructs in future clinical studies aiming at hematoprotection by MGMT gene transfer.

Alkylating Agents↗
PubMed2001

A comparison of chimerism and minimal residual disease between four different allogeneic transplantation methods in patients with chronic myelogenous leukemia in first chronic phase.

The detection of chimerism, residual molecular and cytogenetic disease following transplantation of peripheral blood stem cells (PBSCT) with a nonmyeloablative conditioning (n = 9) and the transplantation of highly purified CD34(+) stem cells (CD34(+) PBSCT) (n = 16) were compared to unmanipulated bone marrow transplantation (BMT) (n = 69) and unmanipulated PBSCT (n = 50) after myeloablative conditioning in patients with first chronic phase of chronic myelogenous leukemia (CML) (n = 137), second chronic phase of CML (n = 4), acute lymphoblastic leukemia (n = 2) and acute myeloid leukemia (n = 1). A molecular relapse (MR) as defined by two consecutive positive polymerase chain reaction assays for the detection of M-bcr-abl transcripts (n = 141) and cbfbeta-myh11 transcripts (n = 1) in a 4-week interval was found in 10 of 16 patients (63%) after CD34(+) PBSCT, and in 27 of 69 patients (39%) after BMT, whereas only three of 50 patients (6%) after PBSCT (P < 0.001) and one of eight patients (13%) after PBSCT with reduced conditioning suffered from a MR. A cytogenetic relapse occurred in five of 16 patients (31%) after CD34(+)PBSCT and 21 of 69 patients (30%) after BMT (NS) compared to two of 50 patients (4%) after PBSCT and none of the eight patients after PBSCT with reduced conditioning (P < 0.05). The lowest treatment-related mortality was seen in the 16 patients after CD34(+) PBSCT, who are all currently alive with a median follow-up of 15 months, whereas the survival rate for BMT, PBSCT and PBSCT with reduced conditioning were 65%, 63% and 58%, respectively. Multivariate analysis including all potential influential factors of post-transplant residual disease recurrence showed that patients after CD34(+) PBSCT had a significantly higher risk (two times) to develop a MR than patients after BMT (P < 0.03), whereas patients after unmanipulated PBSCT had a significant lower risk (eight times) for the occurrence of a MR post transplant (P < 0.001). Patients after BMT and CD34(+) PBSCT had the lowest rates of complete chimerism (CC) at 3 months after transplant. Only five of nine patients (55%) after CD34(+) PBSCT and 19 of 33 patients (58%) after BMT achieved CC compared to 19 of 22 (86%) patients after PBSCT and seven of eight (88%) patients after PBSCT with reduced conditioning (P < 0.05).

Actuarial Analysis↗
PubMed2001

Estimating the relapse stage in chronic myeloid leukaemia patients after allogeneic stem cell transplantation by the amount of BCR-ABL fusion transcripts detected using a new real-time polymerase chain reaction method.

We have used a new single-step real-time reverse transcription polymerase chain reaction (RT-PCR) method to quantify BCR-ABL transcripts, thereby estimating the relapse stage in chronic myeloid leukaemia patients after allogeneic transplants. In 402 samples from 172 patients, BCR-ABL expression was determined and normalized, using the GAPDH housekeeping gene product as an endogenous reference. In our real-time RT-PCR assay, serial dilutions of RNA of the K562 cell line remained positive down to 7.5 pg. The median normalized BCR-ABL amount differed significantly (P < 0.001) between the various disease stages and was 0.06% (range 0.001-1.55%), 3.2% (range 1.4-5.6%) and 21.5% (range 6.8 -827%) in 17 patients with a molecular relapse, in eight patients with a cytogenetic relapse and in 10 patients with a haematological relapse respectively.

Adolescent↗
PubMed2001

MspA provides the main hydrophilic pathway through the cell wall of Mycobacterium smegmatis.

MspA is an extremely stable, oligomeric porin from Mycobacterium smegmatis that forms water-filled channels in vitro. Immunogold electron microscopy and an enzyme-linked immunosorbent assay demonstrated that MspA is localized in the cell wall. An mspA deletion mutant did not synthesize detectable amounts of mspA mRNA, as revealed by amplification using mspA-specific primers and reverse-transcribed RNA. Detergent extracts of the DeltamspA mutant exhibited a significantly lower porin activity in lipid bilayer experiments and contained about fourfold less porin than extracts of wild-type M. smegmatis. The chromosome of M. smegmatis encodes three proteins very similar to MspA. Sequence analysis of the purified porin revealed that mspB or mspC or both genes are expressed in the DeltamspA mutant. The properties of this porin, such as single channel conductance, extreme stability against denaturation, molecular mass and composition of 20 kDa subunits, are identical to those of MspA. Deletion of mspA reduced the cell wall permeability towards cephaloridine and glucose nine- and fourfold respectively. These results show that MspA is the main general diffusion pathway for hydrophilic molecules in M. smegmatis and was only partially replaced by fewer porins in the cell wall of the DeltamspA mutant [corrected] This is the first experimental evidence that porins are the major determinants of the exceptionally low permeability of mycobacteria to hydrophilic molecules.

Amino Acid Sequence↗
PubMed2001

Survival of tumor cells in stem cell preparations and bone marrow of patients with high-risk or metastatic breast cancer after receiving dose-intensive or high-dose chemotherapy.

PURPOSE: We evaluated whether dose-intensive or high-dose chemotherapy can eliminate micrometastases in high-risk breast cancer patients. EXPERIMENTAL DESIGN: We monitored cytokeratin (CK)/17-1A positive cells in the bone marrow (BM) and peripheral blood stem cells (PBSC) and studied Her-2/neu serum levels of patients with locally advanced (n = 13; group 1) and metastatic breast cancer (n = 30; group 2) using immunomagnetic separation, immunocytochemistry, and ELISA. RESULTS: CK+ cells were found in the BM of 3 of 13 (23%) group 1 patients before but not after chemotherapy, resulting in an overall survival (OS) of 92% after a median follow-up of 33 months. Contamination of PBSC in 2 of 9 (22%) patients was not associated with decreased survival. In group 2 patients, the CK+ rate was 60% (18 of 30 patients) before and 40% (4 of 10 patients) after therapy with an OS rate of 43% after 29 months. PBSC samples were positive in 7 of 24 (29%) patients. CK+ BM and PBSC led to a rapid progress and short OS, whereas tumor cell-free BM and PBSC resulted in a mean OS of 30 months. The antigen 17-1A was detected on most CK+ cells in both patient groups before therapy, on all of CK+ PBSC, and on CK+ cells in group 2 patients after therapy. Increased Her-2/neu levels were found in group 2 patients before chemotherapy. CONCLUSION: Micrometastatic cells are present in PBSC grafts and can survive even high-dose chemotherapy. The presence of immunotherapeutic target antigens supports the idea that a combined chemoimmunotherapy might be successful in eliminating minimal residual disease.

Antibiotics, Antineoplastic↗
PubMed2000

Differential susceptibility of renal carcinoma cell lines to tumor suppression by exogenous Fhit expression.

Hemizygous deletions of the fragile histidine triad (FHIT) gene at human chromosome band 3p14.2 and down-regulation of its gene product are found in the majority of renal cell carcinomas (RCCs). Functional tumor suppressive activity of Fhit in renal cancer cells previously was observed in RCC cell line RC48, which lacks endogenous Fhit expression. To further investigate the potential role of FHIT as a tumor suppressor gene in RCC, we transfected FHIT cDNA expression constructs into RCC cell lines RCC-1 and SN12C, which show low-level expression of endogenous Fhit and reveal an intact von Hippel-Lindau (VHL) gene. Stable transfectants of both cell lines showed no alterations of cell morphology, proliferation kinetics, or cell cycle parameters in vitro. The FHIT gene transfer rate, however, was significantly lower in RCC-1 cells compared with SN12C cells, suggesting a selection against exogenous Fhit expression. In addition, in nude mouse assays, a significant delay of tumor formation was observed for FHIT-transfected RCC-1 cell lines, with outgrowing tumors demonstrating loss of Fhit expression in the majority of cells. In contrast, tumorigenicity of FHIT-transfected SN12C cell clones was not suppressed, despite stable transgene expression. In conclusion, our results demonstrate a selective tumor suppressive activity of Fhit in RCC cells in vivo and suggest that the susceptibility to suppression is not restricted to cancer cells with complete loss of Fhit expression.

Acid Anhydride Hydrolases↗
PubMed2000

Type and position of promoter elements in retroviral vectors have substantial effects on the expression level of an enhanced green fluorescent protein reporter gene.

PURPOSE: Although gene transfer with retroviral vectors has already been applied to patients as part of clinical protocols, low expression of transgenes in target cells still remains a problem. Therefore, we compared various retroviral vectors using different promoters and backbones for expression of the enhanced green fluorescent protein (EGFP) reporter gene in fibroblasts and CD34+ cells. METHODS: The N2A retroviral vector was used to test expression from the herpes simplex virus thymidine kinase promoter (vector N2A-TK-EGFP), a human phosphoglycerate kinase promoter (vector N2A-PGK-EGFP), and the SV40 promoter (vector N2A-SV-EGFP). Additional constructs used the spleen focus-forming virus (SFFV) long terminal repeat (LTR) as promoter and expressed EGFP alone (vector SFbeta1-EGFP) or EGFP and a downstream (vector SFbeta1-EGFP-IRES) or upstream (vector SFbeta1-IRES-EGFP) internal ribosomal entry site. RESULTS: For NIH 3T3 cells the fluorescence-activated cell sorting analysis revealed that the most active internal promoter was the SV40 promoter in the vector N2A-SV-EGFP (mean fluorescence intensity, MFI, 66.7 +/- 0.4), followed by N2A-PGK-EGFP (26.3 +/- 1.8 MFI), and N2A-TK-EGFP (4.8 +/- 0.1 MFI). Expression from the SFbeta1-EGFP vector (82.6 +/- 6.7 MFI) and the SFbeta1-EGFP-IRES vector (102.8 +/- 6.2 MFI) was higher than from SFbeta1-IRES-EGFP vector (15.5 +/- 1.8 MFI). In human CD34-positive cells, the EGFP expression from all vectors was considerably lower than in fibroblasts with the SFbeta1-EGFP vector still being four- to fivefold more active than the internal promoters tested. CONCLUSION: The SFFV LTR seems to allow a high expression of transgenes, as long as the transgene is not expressed downstream of an internal ribosomal entry site. Internal promoters may be useful for targeted gene expression in specific cell types, but the reduced level of expression from some internal promoters has to be taken into consideration.

3T3 Cells↗
PubMed2000

The amount of BCR-ABL fusion transcripts detected by the real-time quantitative polymerase chain reaction method in patients with Philadelphia chromosome positive chronic myeloid leukemia correlates with the disease stage.

The use of the real-time reverse-transcription polymerase-chain reaction (RT-PCR) method to quantify BCR-ABL transcripts before and after allogeneic transplant was prospectively studied in 65 patients with chronic myeloid leukemia (CML). The expression of the BCR-ABL transcript was determined and normalized using the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) housekeeping gene product as an endogenous reference. In the single step real-time PCR assay, tenfold serial dilutions of cDNA of the K5652 cell line remained positive down to 100 pg cDNA only. However, molecular relapses of CML after transplant were only safely detectable when a nested real-time PCR assay was performed, which was able to detect 1-10 pg cDNA from a tenfold serial dilution. The median normalized BCR-ABL transcript level was measured as 0.004% in 17 patients with a molecular relapse, 0.4% in 7 patients with a cytogenetic relapse, 2.6% in 36 patients with a stable phase of CML, and 36% in 5 patients with a relapse in a blast crisis. The analyzed median normalized amount of BCR-ABL transcript differed significantly (P<0.001) between the various disease stages. In ten CML patients with relapse, the real-time PCR method was used to monitor the response of various immunotherapies as donor leukocyte infusions, withdrawal of immunosuppression, or interferon-alpha application. The results of the quantitative evaluation of BCR-ABL transcripts reflected very well the clinical effect of the different applied immunotherapies. The new real-time PCR method seems to be a suitable technique for the early detection of relapse after allogeneic transplant in patients with the BCR-ABL transcript. Its ability to distinguish between molecular and cytogenetic relapse (P<0.001) allows early therapeutic decisions.

Bone Marrow Transplantation↗
PubMed2000

Long-term survival after induction therapy with idarubicin and cytosine arabinoside for de novo acute myeloid leukemia.

We treated 153 patients with de novo acute myeloid leukemia (AML) with two induction courses of conventional-dose cytosine arabinoside (ara-C) and idarubicin (AIDA) followed by either a third course of AIDA, high-dose ara-C or bone-marrow transplantation. The complete remission (CR) rate for all patients was 63.4%, with a higher CR rate for patients with a normal (versus unfavorable) karyotype (73.2% vs 52.5%; P=0.038). The probability of overall survival (OS) was 30.7% after 5 years (26.3% after 7 years). Improved OS at 5 years could be observed for patients up to 50 years old versus patients older than 50 years of age (37.6% vs 19.9%; P=0.001) and patients with a normal (versus unfavorable) karyotype (42.9% vs 14.1%; P=0.0016). Disease-free survival (DFS) after 5 years was 33.2% for all 97 CR patients and was significantly better for patients with a normal (versus unfavorable) karyotype (44.3% vs 12.3%; P= 0.003). Multivariate analysis revealed that the age for OS (P < 0.02) and the karyotype for both OS (P<0.03) and DFS (P< 0.05) were independent prognostic factors. In conclusion, AIDA is an effective and well-tolerated induction regimen (even in elderly patients) with a 5-year survival of more than 30% when combined with ara-C-containing postremission therapy. The karyotype is the most powerful prognostic factor for predicting the outcome of patients treated with this protocol.

Acute Disease↗
PubMed2000

Transplant activities in Germany in 1998--a survey facilitated by the National Registry for Hemopoietic Stem Cell Transplantation.

To improve the infrastructure of hemopoietic stem-cell transplantations in our country, the German Registry for Hemopoietic Stem-Cell Transplantations (DRST) was established in 1998. The present paper summarizes the current status of the DRST and gives a survey of transplant activities in Germany in 1998 in terms of transplant units, transplant types, transplant frequencies and underlying diseases.

Blood Cells↗
PubMed2000

Investigation of bioavailability and pharmacokinetics of treosulfan capsules in patients with relapsed ovarian cancer.

PURPOSE: Treosulfan (L-threitol-1,4-bis-methanesulfonate, Ovastat) is a prodrug of a bifunctional alkylating agent with activity in ovarian carcinoma and other solid tumors. In a pharmacologic study of the bioavailability of treosulfan in a capsule formulation, patients with relapsed ovarian carcinoma were treated with alternating doses of oral and intravenous (i.v.) treosulfan of 1.5 or 2.0 g daily for 5 to 8 days. METHODS: A sensitive method for the determination of treosulfan in plasma and urine by reversed-phase high-performance liquid chromatography had previously been developed. Pharmacokinetic analyses of treosulfan were carried on plasma and urine samples from 20 i.v. courses and 20 courses of oral administration. RESULTS: The bioavailability ratio (f) of oral to i.v. administration was calculated as 0.97 +/- 0.18 (mean +/- SD) using the values AUC oral = 82.1 +/- 39.4 microg/ml h and AUC i.v. = 85.4 +/- 30.3 microg/ml h. The peak plasma concentration cmax (29 +/- 14 microg/ml vs 65 +/- 23 microg/ml) was significantly (P < 0.01) higher after i.v. administration and the tmax after oral administration was 1.5 +/- 0.34 h. The terminal half-life of treosulfan was about 1.8 h. The mean urinary excretion of the parent compound was about 15% of the administered total dose over 24 h (range 6-26%). CONCLUSIONS: The high and relatively constant bioavailability of treosulfan indicates that capsules provide a satisfactory noninvasive treatment alternative. A feasible and reliable oral treosulfan formulation could provide the basis for the development of long-term low-dose outpatient treatment of patients with malignant diseases.

Administration, Oral↗
PubMed2000

In vitro effect of multidrug resistance modifiers on idarubicinol efflux in blasts of acute myeloid leukemia.

Recent results show that the intracellular uptake pattern of idarubicin (IDA) in multidrug-resistant (MDR) cells is nearly identical to that seen in the drug-sensitive parent cell line, whereas the MDR cells have minimal daunorubicin (DNR) uptake compared with the drug-sensitive parent cells. It is known that the major metabolite of IDA, idarubicinol (IDA-OL), has nearly the same cytotoxicity as IDA, while the cytotoxicity of daunorubicinol (DNR-OL) is about 1/30th of that of DNR. We examined the effect of the MDR modifiers verapamil and dexniguldipine on the efflux of IDA, DNR and their hydroxylated metabolites IDA-OL and DNR-OL in blast populations of acute myeloid leukemia (AML), in the MDR-negative cell line CEM-CCRF and in their MDR-positive counterpart (CEM-VBL). All patients with relapsed or persistent AML had been pretreated with IDA and cytosine arabinoside. The efflux of the anthracyclines was estimated by flow cytometry. A total of 36 patients with AML were investigated; 18 out of 36 AML blast populations showed an efflux of DNR, DNR-OL and IDA-OL. The efflux of DNR, DNR-OL and particularly IDA-OL could be reversed by 10 microM verapamil or 1 microM dexniguldipine. For IDA we found an effusion of 40 +/- 11% in all blast populations which could not be significantly inhibited by the modulators. Similar results for IDA were found in the MDR-positive cell line (CEM-VBL 100) and in their MDR-negative counterpart (CEM-CCRF). The incubation of CEM-CCRF cells with DNR, DNR-OL, IDA-OL and especially IDA led to MDR induction as determined by reverse transcription/polymerase chain reaction analysis with MDR-specific primer and by cellular efflux studies. We conclude that the outcome of chemotherapy with idarubicin is influenced by MDR, although IDA is not essentially MDR-dependent itself, but because IDA-OL is actively involved in multidrug resistance. Further investigations should consider the question of whether the combination of IDA and MDR modifiers can enhance the serum level of the active metabolite IDA-OL and can reverse the MDR pattern in cells treated with IDA.

Antineoplastic Agents↗
PubMed2000

Differential modulation of chemosensitivity to alkylating agents and platinum compounds by DNA repair modulators in human lung cancer cell lines.

PURPOSE: Modulation of DNA repair represents one strategy to overcome cellular drug resistance to alkylating agents and platinum compounds. The effects of different known DNA repair modulators such as O6-benzylguanine (6 microg/ml), fludarabine (25 ng/ml), aphidicolin (8.5 ng/ml), pentoxifylline (1.4 microg/ml) and methoxamine (12.4 microg/ml) on the cytotoxicity of mafosfamide, chlorambucil, 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), cisplatin and carboplatin were tested in human lung cancer cell lines. METHODS: Chemosensitivity of the human adenocarcinoma cell line MOR/P and the cisplatin-resistant subline MOR/CPR as well as the large-cell lung cancer cell line L23/P and its cisplatin-resistant counterpart L23/CPR were evaluated by the MTT colorimetric assay. RESULTS: O6-benzylguanine, an inhibitor of O6-alkylguanine-DNA alkyltransferase, significantly sensitised MOR/P and MOR/CPR cells to the cytotoxic effect of BCNU. Fludarabine, methoxamine and aphidicolin did not change the chemosensitivity of the parental and cisplatin-resistant cell lines to any cytotoxic drug tested. Interestingly, O6-benzylguanine enhanced the chemoresistance of parental and cisplatin-resistant cell lines to platinum compounds. Also, pentoxifylline increased resistance of the MOR cell lines to mafosfamide. CONCLUSIONS: Modulation of DNA repair elicits not only chemosensitisation but may also enhance cellular resistance to DNA-affine drugs.

Antineoplastic Agents, Alkylating↗
PubMed2000

Analysis of thrombopoietin receptor (c-mpl) mRNA expression in de novo acute myeloid leukemia.

Expression of the thrombopoietin receptor, c-mpl, has been recently suggested to represent an adverse prognostic factor in myelodysplasia and acute myeloid leukemia (AML). To further evaluate this putative correlation, we assessed the c-mpl mRNA expression in blast samples of 53 AML patients. Overall, c-mpl mRNA expression was observed in 27 (51%) patients. No significant difference between c-mpl(+) and c-mpl(-) patients was found with respect to established prognostic factors such as age (50 vs. 53 years) or karyotype, whereas a significant correlation was observed between c-mpl and CD34 expression (P = 0.026). Among 40 patients who completed standard-/high-dose cytarabine-containing induction/consolidation treatment and were evaluable for treatment response, a higher complete remission (CR) rate was achieved in c-mpl- than in c-mpl(+) patients (95 vs. 68%; P = 0.026). Upon multivariate analysis, this relationship was independent from CD34 expression. CR duration was not significantly longer in c-mpl(-) than in c-mpl(+) patients (median: 14 vs. 10 months, P = 0.262). In conclusion, our data strongly support the previously suggested notion that c-mpl expression is of prognostic relevance for CR induction in de novo AML patients, and suggest determination of c-mpl expression within larger prospective studies in the attempt to develop risk-adapted AML treatment strategies.

Acute Disease↗