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Christian M Kurbacher

Publications and source records attributed to Christian M Kurbacher.

15 recordsLinked to original sources
PubMed2006

Anticancer drugs induce mdr1 gene expression in recurrent ovarian cancer.

Ovarian cancer is currently the most lethal gynecologic malignancy in Europe and the US. Platin analogues and paclitaxel demonstrate high remission rates, but unfortunately the efficacy of cytostatic agents is limited by the development of multidrug resistance (mdr). Clinical paclitaxel resistance is often associated with mdr1 overexpression. In a recent study, we introduced a highly specific quantitative real-time reverse transcriptase polymerase chain reaction for the quantification of mdr1 transcripts. In the present study, we demonstrate that primary tumor cells from patients with recurrent ovarian cancer overexpress mdr1. To evaluate mdr1 expression, we collected tumor cells from 77 ovarian cancer patients (13 chemotherapy-naive ovarian cancer, 64 recurrent ovarian cancer). Cancer cells were aspirated from 49 solid specimens (63%) and 28 ascitic fluids (37%). Subsequently, cancer cells were exposed in 221 short-term cultures either to blank medium (control) or to a single anticancer drug, cisplatin, doxorubicin or paclitaxel. The drug concentrations applied referred to clinical relevant doses. mdr1 mRNA expression was significantly higher in specimens from recurrent ovarian cancer incubated in paclitaxel than in specimens from chemotherapy-naive ovarian cancer. No significant differences were detectable between the mean value of mdr1 mRNA expression in tumor specimens from recurrent ovarian cancer incubated in cisplatin or doxorubicin. Differences within the untreated patients group were also not statistically significant. The result of this study confirms clinical observations, as well as in-vitro studies based on tumor cell lines, that paclitaxel resistance is correlated with mdr1 overexpression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2005

Pilot studies of the effect of zoledronic acid (Zometa) on tumor-derived cells ex vivo in the ATP-based tumor chemosensitivity assay.

There is debate regarding the direct effect of bisphosphonates against visceral metastases from solid tumors, despite their proven efficacy against the skeletal complications of metastasis. The aim of this study was to determine whether zoledronic acid showed direct activity against five ovarian cell lines and tumor-derived cells, and whether addition of zoledronic acid to cytotoxic agents increased their cytotoxicity. In this study we used a standardized ATP-based tumor chemosensitivity assay (ATP-TCA) to measure the activity of alendronate, clodronate and zoledronic acid in five ovarian carcinoma cell lines and human solid tumors (breast, lung, ovarian, unknown primary carcinoma, and cutaneous and uveal melanoma) (n=34). We also tested the combination of zoledronic acid with paclitaxel and cisplatin in tumor-derived cells. All five cell lines exhibited greater sensitivity to bisphosphonates than the tumor-derived cells and in all five the IC50 for zoledronic acid was less than 4 muM. In the tumor-derived cells, zoledronic acid showed concentration-dependent inhibition with a median IC50 for all tumors tested of 17 muM and evidence of apoptosis (caspase activation). Simultaneous addition of zoledronic acid to cisplatin or paclitaxel showed no major increase in cytotoxicity. We conclude that the activity of bisphosphonates was greater in cell lines than in tumor-derived cells. However, the pattern of activity of bisphosphonates was the same in cell lines and tumor derived cells. This study suggests a direct, or possibly an indirect, effect of zoledronic acid and other nitrogen-containing bisphosphonates against neoplastic cells, but simultaneous addition with cisplatin or paclitaxel does not substantially increase the activity of the cytotoxic agent.

Adenosine Triphosphate↗
PubMed2005

Chemosensitivity testing using microplate adenosine triphosphate-based luminescence measurements.

During the last two decades, novel nonclonogenic methods for pretherapeutic chemosensitivity testing have been developed that are likely to overcome major technical limitations of older assays such as low evaluability rates, low degree of standardization and reproducibility, lack of technical robustness, and poor methodological efficacy. Among these, the microplate adenosine triphosphate (ATP)-based tumor chemosensitivity assay (ATP-TCA) has gained particular merits for ex vivo chemosensitivity testing of native nonhematological tumors including cancers of the breast, ovary, gastrointestinal tract, cervix and corpus uteri, and lung; malignant melanomas; gliomas; sarcomas; and mesotheliomas. For this indication, the ATP-TCA can now be considered the best documented and validated technology. This assay, which is now commercially available, provides a highly reproducible, easy-to-handle kit technique; low technical failure rates; and a high methodological efficacy requiring only 1 x 106 tumor cells to test four to six different drugs or combinations. In ovarian and breast carcinomas, the predictive accuracy is > 90%, with a positive predictive value of 85-90% and a negative predictive value near 100%, respectively. In primary ovarian cancers, the ATP-TCA has been found to accurately predict both clinical response and survival. In two prospective clinical trials in patients with heavily pretreated ovarian cancer, chemotherapy individually selected by the ATP-TCA has been found to triple the response rates and nearly double the survival compared to empirically chosen regimens. Consequently, this assay, which is now under phase III evaluation, has successfully been used in new agent development to screen for novel chemotherapy regimens for the treatment of patients with breast and ovarian carcinoma and melanoma, respectively. This chapter highlights the recent preclinical and clinical experience with this promising technology and gives a detailed description of all the technical aspects of the ATP-TCA.

Adenosine Triphosphate↗
PubMed2005

Continuous low-dose GM-CSF as salvage therapy in refractory recurrent breast or female genital tract carcinoma.

Granulocyte-macrophage colony-stimulating factor (GM-CSF, sargramostim [Leukine]) is a powerful cytokine that is able to stimulate the generation of dendritic cells. Adjuvant treatment with continuous low-dose GM-CSF has been shown to prolong survival of stage III/IV melanoma patients. Data on continuous low-dose GM-CSF therapy in tumors other than prostate cancer are still lacking. This pilot trial was initiated in order to evaluate the efficacy and tolerability of continuous low-dose GM-CSF as salvage in various chemotherapy-refractory carcinomas. A total of 19 patients who had failed a median of 4 prior chemotherapies were included. Their malignancies included metastatic breast cancer, recurrent ovarian carcinoma, metastatic endometrial carcinoma, and recurrent squamous cell cancer of the cervix uteri. Continuous low-dose GM-CSF was delivered subcutaneously at a daily starting dose of 125 microg. GM-CSF was increased at 25-microg increments until a maximum of 250 microg was reached or when mild leukocytosis (10-20 g/L) was achieved, providing that the relative eosinophil count did not exceed 15%. Therapy was continued until progression or refusal by the patient. Toxicity was generally mild. Only one patient was withdrawn due to grade 3 fatigue. In three additional patients, temporary dose reduction was necessary because of grade 1 injection site reactions, which recovered spontaneously. Mild to moderate leukocytosis was obvious in 10 patients. Systemic hypersensitivity-like reactions did not occur and no patient required hospitalization for other life-threatening side effects. The objective response rate was 37%: 1 complete and 6 partial responses, 4 disease stabilizations, 8 progression of disease. Median response duration was 6 months. Notably, 6 of 7 responders but only 1 of 8 patients with disease progression developed leukocytosis during therapy. Therefore, we conclude that continuous low-dose GM-CSF has substantial activity in heavily pretreated patients with either metastatic breast cancer or female genital tract cancer. Achievement of mild leukocytosis seems to be a predictor of response.

Breast Neoplasms↗
PubMed2004

Dysregulation of protein kinase C activity in chemoresistant metastatic breast cancer cells.

This study was performed to evaluate the role of protein kinase C (PKC) activity in the development of chemoresistance in clinical breast cancer cells. To simulate the clinical situation, native tumor cells derived from 10 patients with advanced breast cancer were brought into short-term cultures, and treated with anthracyclines (doxorubicin, mitoxantrone), paclitaxel and combinations, respectively. After 3 days of incubation, we determined total PKC activity relative to each control incubated with blank medium. Furthermore, we determined the chemoresistance against these drugs from each cell population separately. Relative PKC activity ranged from 14 to 249%; 64% (37 of 58) of the breast cancer cell suspensions were considered chemoresistant. There was a non-significant trend to a higher relative PKC activity in resistant cells compared to non-resistant cells (p=0.058), regardless of the antineoplastic agent investigated. The individual variability in both PKC activity and chemoresistance pattern revealed that dysregulated PKC activity mediates resistance to antineoplastics. In order to achieve clinical value, evaluation of more data concerning the PKC signal-transduction pathway is necessary. New protocols of cancer treatment will require this information in order to be successful.

Adult↗
PubMed2003

Outcome of ATP-based tumor chemosensitivity assay directed chemotherapy in heavily pre-treated recurrent ovarian carcinoma.

BACKGROUND: We wished to evaluate the clinical response following ATP-Tumor Chemosensitivity Assay (ATP-TCA) directed salvage chemotherapy in a series of UK patients with advanced ovarian cancer. The results are compared with that of a similar assay used in a different country in terms of evaluability and clinical endpoints. METHODS: From November 1998 to November 2001, 46 patients with pre-treated, advanced ovarian cancer were given a total of 56 courses of chemotherapy based on in-vitro ATP-TCA responses obtained from fresh tumor samples or ascites. Forty-four patients were evaluable for results. Of these, 18 patients had clinically platinum resistant disease (relapse < 6 months after first course of chemotherapy). There was evidence of cisplatin resistance in 31 patients from their first ATP-TCA. Response to treatment was assessed by radiology, clinical assessment and tumor marker level (CA 125). RESULTS: The overall response rate was 59% (33/56) per course of chemotherapy, including 12 complete responses, 21 partial responses, 6 with stable disease, and 15 with progressive disease. Two patients were not evaluable for response having received just one cycle of chemotherapy: if these were excluded the response rate is 61%. Fifteen patients are still alive. Median progression free survival (PFS) was 6.6 months per course of chemotherapy; median overall survival (OAS) for each patient following the start of TCA-directed therapy was 10.4 months (95% confidence interval 7.9-12.8 months). CONCLUSION: The results show similar response rates to previous studies using ATP-TCA directed therapy in recurrent ovarian cancer. The assay shows high evaluability and this study adds weight to the reproducibility of results from different centres.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2003

Cisplatin, doxorubicin and paclitaxel induce mdr1 gene transcription in ovarian cancer cell lines.

The clinical observation of the multidrug resistance (MDR) phenotype is often associated with overexpression of the mdrl gene, in particular with respect to ovarian cancer. However, until now the mdrl-inducing potential of commonly used antineoplastics has been only incompletely explored. We performed short-term cultures of six ovarian cancer cell lines (MZOV4, EF027, SKOV3, OAW42, OTN14, MZOV20) exposed to either blank medium or cisplatin, doxorubicin or paclitaxel at concentrations related to the clinically achievable plasma peak concentration. A highly specific quantitative real-time RT-PCR was used to detect the Mdr1 transcripts. Mdrl mRNA contents were calibrated in relation to coamplified GAPDH mRNA. Mdrl mRNA was detectable in each cell line. In 13 out of 18 assays (72%) the specific anticancer drug being tested induced mdr1 transcription. No decrease in mdr1 mRNA concentration was observed. Our data suggest that mdr1 induction by antineoplastics is one of the reasons for failure of ovarian cancer therapy but may vary individually.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

ATP chemosensitivity testing in ovarian and breast cancer: early clinical trials.

After disappointing results achieved with older chemosensitivity tests such as the human tumor clonogenic assay (HTCA) during the 1980s, the last decade has seen a renaissance of the concept of individualized chemotherapy in oncology, markedly stimulated by the development of newer nonclonogenic assays. These methods appear to be able to overcome major technical limitations associated with older assays, now allowing for successful testing of most of the tumor specimens submitted. Currently, the ATP-based tumor chemosensitivity assay (ATP-TCA) can be regarded as the most sophisticated assay to investigate both solid samples and effusions derived from patients with various organ tumors. During the last 5 years, the ATP-TCA has been used successfully to screen for novel drug combinations for further clinical use in both ovarian and breast cancer such as mitoxantrone plus paclitaxel (NT) and treosulfan plus gemcitabine (TG), respectively. Clinical trials that have been set up in heavily pretreated patients with recurrent ovarian or breast cancer have convincingly confirmed the high activity of these combinations previously demonstrated in preclinical investigations using the ATP-TCA. In a recent phase II trial performed in 59 patients with relapsed ovarian carcinoma, ATP-TCA-directed therapy was able to triple the response rate and to double the survival time, compared with published empirical chemotherapy regimes. Preliminary results with ATP-TCA-directed therapy in breast cancer also evidenced promising response rates. These results have been confirmed by additional prospective clinical trials using other types of modern nonclonogenic assays. A phase III trial that is now actively recruiting patients with platinum-refractory ovarian cancer to verify the promising phase II studies will prove the further value of the ATP-TCA as a predictor applicable in routine clinical oncology.

Adenosine Triphosphate↗
PubMed2003

Hematological side-effect profiles of individualized chemotherapy regimen for recurrent ovarian cancer.

The long-term results for patients with recurrent ovarian cancer (ROC) are poor. There is a need to optimize treatment strategies to improve outcome by avoiding ineffective regimens which are often associated with exacerbated side-effects. Individualized chemotherapy regimens guided by a chemosensitivity assay (ATP-tumor chemosensitivity assay) have already been used successfully to direct chemotherapy. Taking the results of this assay into account, application of drug combinations appears more advisable. Here we present a systematic evaluation of toxicities seen with individualized chemotherapy for ROC. A total of 62 patients who received 314 cycles of antineoplastic therapies were evaluated. Three single agents (topotecan, paclitaxel and gemcitabine) and five combinations (cisplatin/gemcitabine, carbopatin/gemcitabine, gemcitabine/treosulfan, mitoxantrone/paclitaxel and carboplatin/paclitaxel) were examined. With respect to myelotoxicity, most single agents except topotecan revealed favorable results in comparison to drug combinations. However, this observation lacks statistical significance. Generally, severe myelosuppression was rare. The highest incidence of leukopenia was seen in regimens with mitoxantrone/paclitaxel or gemcitabine/treosulfan, respectively. Thrombocytopenia accompanied most commonly a topotecan therapy. In the present study combination regimens tend to be more toxic than monotherapies. When response rates are comparable, empirically chosen treatment combination therapies should only be practiced in carefully planned clinical studies.

Adenosine Triphosphate↗
PubMed2002

Cytokine expression in peripheral blood lymphocytes indicates a switch to T(HELPER) cells in patients with preeclampsia.

We sought to determine whether cytokine expression in peripheral blood mononuclear cells is altered in patients with preeclampsia and in patients with a history of recurrent spontaneous abortion (RSA). Twenty-four patients with preeclampsia and twenty patients with a history of RSA were included into the study. Two control groups consisted of twenty healthy pregnant and twenty healthy non-pregnant women. The intracellular expression of interleukin-2 (IL-2), interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) were determined in peripheral blood mononuclear cells (PBMCs) by flow cytometry as a measure of cytokine production. IL-2 synthesis was significantly elevated in the third trimester in preeclamptic patients in comparison with the control group. Non-pregnant women with RSA showed a significantly lower expression of IFN-gamma compared to the non-pregnant control group. Our data suggest an abnormal immune response in preeclamptic patients characterised by a shift to a predominantly Th1-type immunity.

Adult↗
PubMed2002

Individualized long-term chemotherapy for recurrent ovarian cancer after failing high-dose treatment.

Chemotherapy for recurrent ovarian carcinoma (ROC) produces response rates of 10-80% depending on the prevalence of platinum resistance. Most patients relapse within 1 year and median progression-free survival is generally no more than 6 months. Newly developed ATP chemosensitivity assays (ATP-TCA) offer the opportunity for individualized therapy and have shown promising results compared to standard regimens. We report on an unusual case of long-term survival in a patient with stage III c ovarian cancer failing postoperative platinum-based high-dose treatment who subsequently underwent repeated chemotherapy over a period of 4 years. The chemotherapy protocol was selected by pretherapeutic ex vivo ATP-based chemosensitivity testing of autologous tumor tissue. To our knowledge, this is one of the few cases of ROC in which partial remissions using conventionally dosed chemotherapy were achieved repeatedly despite a unfavorable relapse-free interval after high-dose chemotherapy for primary disease. We conclude that ATP-TCA-directed chemotherapy for ROC can select active and tolerable regimens even in difficult therapeutic situations in which no standards recommendation exists.

Adenocarcinoma↗
PubMed2002

Use of an ATP-based chemosensitivity assay to design new combinations of high-concentration doxorubicin with other drugs for recurrent ovarian cancer.

Liposomal doxorubicin (Caelyx/Doxil) has been shown to be active in around 20% of recurrent ovarian cancers. As yet, there is little clinical data on combinations of existing agents with liposomal doxorubicin, despite considerable clinical experience with soluble doxorubicin in combination. In this study, we have used an ATP-based tumor chemosensitivity assay to determine the relative efficacy of high concentrations of doxorubicin tested in combination with cisplatin, treosulfan, 5-fluorouracil (5-FU) or vinorelbine against cells obtained from recurrent ovarian tumor tissue. The results show little enhancement of the efficacy of high concentrations of doxorubicin by 5-FU, cisplatin, or treosulfan. However, vinorelbine+liposomal doxorubicin showed additive inhibition, and this combination is worthy of further testing in clinical trials.

Adenosine Triphosphate↗
PubMed2002

Chemosensitivity of normal human trophoblasts evaluated by a newly developed ATP-based luminescence assay.

Trophoblast injury may be one of the possible causes of fetal distress associated with chemotherapy administered during pregnancy. The purpose of this study was to investigate the ex vivo chemosensitivity of normal trophoblasts (NTB) against commonly used antineoplastic agents. Using the newly developed ex vivo ATP-based trophoblast assay (ATP-TBA), 31 NTB freshly sampled from human placentas (gestational week 7-42) were tested against dactinomycin (Act-D), 5-fluorouracil (5-FU), 4-OOH-cyclophosphamide (4-HC), vincristine (VCR) and methotrexate (MTX) alone or in combination with calcium folate (LV). All agents were studied at concentrations relevant to clinical dosages normally used for chemotherapy of solid neoplasms. Of 31 samples studied with the ATP-TBA, 20 (65%) were evaluable. VCR, Act-D and 4-HC were the most active drugs with 55, 45 and 45% of samples responding ex vivo. Antimetabolites were less active, producing ex vivo response rates of 25 (MTX) and 20% (5-FU), respectively. MTX activity was largely neutralized by adding LV. The chemosensitivity of NTB showed considerable inter-individual variations and did not decrease with increasing gestational age. We therefore conclude that NTB of any gestational age exhibit considerable ex vivo sensitivity against common anticancer agents which is comparable to that observed for various solid tumors. The ATP-TBA may be helpful in planning future trials with both single agents and drug combinations in order to standardize and optimize chemotherapy during pregnancy.

Adenosine Triphosphate↗
PubMedDate not supplied

Induction of MDR1-gene expression by antineoplastic agents in ovarian cancer cell lines.

BACKGROUND: Development of resistance to anticancer drugs is a major concern in clinical oncology and might be particularly involved in the secondary treatment failure frequently seen in ovarian cancer. Clinical observation of the multidrug resistance (MDR) phenotype is often associated with overexpression of the mdr1-gene. However, until now the mdr1-inducing potential of commonly used antineoplastics has been only incompletely explored. MATERIALS AND METHODS: We perfomed short-term cultures of 7 established ovarian cancer cell lines exposed to either blank medium or one of three single anticancer drugs (cisplatin, doxorubicin, paclitaxel) at concentrations related to the clinically achievable plasma peak concentration. Mdr1-transcripts were detected using the highly specific quantitative real time RT-PCR. To calibrate each approach, mdr1-mRNA content was calculated in relation to co-amplified GAPDH-mRNA. RESULTS: Mdr1-mRNA was detectable in each cell line. In 13 assays (62%) the specific anticancer drug being tested induced mdr1-transcription. No decrease in mdr1-mRNA concentration was observed. The method described here is easy to perform and could be of striking value in predicting the development of tumor chemoresistance. CONCLUSION: Our data indicate that mdr1-induction by antineoplastics is one of the reasons for failure of ovarian cancer therapy but may vary from one individual to another.

Antineoplastic Agents↗