Intratumoral pharmacokinetic analysis by 19F-magnetic resonance spectroscopy and cytostatic in vivo activity of gemcitabine (dFdC) in two small cell lung cancer xenografts

Molecular magnetic resonance imaging in cancer

The ability to identify key biomolecules and molecular changes associated with cancer malignancy and the capacity to monitor the therapeutic outcome against these targets is critically important for cancer treatment. Recent developments in molecular imaging based on magnetic resonance (MR) techniques have provided researchers and clinicians with new tools to improve most facets of cancer care. Molecular imaging is broadly described as imaging techniques used to detect molecular signature at the cellular and gene expression levels. This article reviews both established and emerging molecular MR techniques in oncology and discusses the potential of these techniques in improving the clinical cancer care. It also discusses how molecular MR, in conjunction with other structural and functional MR imaging techniques, paves the way for developing tailored treatment strategies to enhance cancer care.

Magnetic resonance spectroscopy of cancer metabolism and response to therapy

Magnetic resonance spectroscopy allows noninvasive in vivo measurements of biochemical information from living systems, ranging from cultured cells through experimental animals to humans. Studies of biopsies or extracts offer deeper insights by detecting more metabolites and resolving metabolites that cannot be distinguished in vivo. The pharmacokinetics of certain drugs, especially fluorinated drugs, can be directly measured in vivo. This review briefly describes these methods and their applications to cancer metabolism, including glycolysis, hypoxia, bioenergetics, tumor pH, and tumor responses to radiotherapy and chemotherapy.

A novel method for quantification of gemcitabine and its metabolites 2',2'-difluorodeoxyuridine and gemcitabine triphosphate in tumour tissue by LC-MS/MS: comparison with (19)F NMR spectroscopy

PURPOSE

To develop a sensitive analytical method to quantify gemcitabine (2',2'-difluorodeoxycytidine, dFdC) and its metabolites 2',2'-difluorodeoxyuridine (dFdU) and 2',2'-difluorodeoxycytidine-5'-triphosphate (dFdCTP) simultaneously from tumour tissue.

METHODS

Pancreatic ductal adenocarcinoma tumour tissue from genetically engineered mouse models of pancreatic cancer (KP ( FL/FL ) C and KP ( R172H/+) C) was collected after dosing the mice with gemcitabine. (19)F NMR spectroscopy and LC-MS/MS protocols were optimised to detect gemcitabine and its metabolites in homogenates of the tumour tissue.

RESULTS

A (19)F NMR protocol was developed, which was capable of distinguishing the three analytes in tumour homogenates. However, it required at least 100 mg of the tissue in question and a long acquisition time per sample, making it impractical for use in large PK/PD studies or clinical trials. The LC-MS/MS protocol was developed using porous graphitic carbon to separate the analytes, enabling simultaneous detection of all three analytes from as little as 10 mg of tissue, with a sensitivity for dFdCTP of 0.2 ng/mg tissue. Multiple pieces of tissue from single tumours were analysed, showing little intra-tumour variation in the concentrations of dFdC or dFdU (both intra- and extra-cellular). Intra-tumoural variation was observed in the concentration of dFdCTP, an intra-cellular metabolite, which may reflect regions of different cellularity within a tumour.

CONCLUSION

We have developed a sensitive LC-MS/MS method capable of quantifying gemcitabine, dFdU and dFdCTP in pancreatic tumour tissue. The requirement for only 10 mg of tissue enables this protocol to be used to analyse multiple areas from a single tumour and to spare tissue for additional pharmacodynamic assays.

19F NMR in vivo spectroscopy reflects the effectiveness of perfusion-enhancing vascular modifiers for improving gemcitabine chemotherapy

Nuclear magnetic resonance spectroscopy of fluorine-19 ((19)F NMR) has proven useful for evaluating kinetics of fluorinated chemotherapy drugs in tumors in vivo. This work investigated how three perfusion-enhancing vascular modifiers (BQ123, thalidomide, and Botulinum neurotoxin type A [BoNT-A]) would affect the chemotherapeutic efficacy of gemcitabine, a fluorinated drug widely used in human cancer treatment. Murine tumor growth experiments demonstrated that only BoNT-A showed a strong trend to enhance tumor growth inhibition by gemcitabine (1.7 days growth delay, P = 0.052, Student t-test). In accord with these results, (19)F NMR experiments showed that only BoNT-A increased significantly the uptake of gemcitabine in tumors (50% increase, P = 0.0008, Student t-test). Further experiments on gemcitabine kinetics (NMR vs time) and distribution ((19)F MRI) confirmed the uptake-enhancing properties of BoNT-A. The results of this study demonstrate that (19)F NMR can monitor modulation of the pharmacokinetics of fluorinated chemotherapy drugs in tumors. The results also show that (19)F NMR data can give a strong indication of the effectiveness of perfusion-enhancing vascular modifiers for improving gemcitabine chemotherapy in murine tumors. (19)F NMR is a promising tool for preclinical evaluation of such vascular modifiers and may ultimately be used in the clinic to monitor how these modifiers affect chemotherapy.

Phase II Study of Gemcitabine and Cisplatin in Patients with Previously Untreated Extensive Stage Small Cell Lung Cancer: Southwest Oncology Group Study 9718

BACKGROUND

This phase II study (S9718) evaluated the antineoplastic activity and tolerability of the combination of gemcitabine and cisplatin in previously untreated patients with extensive stage small cell lung cancer (ES-SCLC).

METHODS

Chemonaive patients with ES-SCLC, received gemcitabine 1250 mg/m intravenously (IV) over 30 minutes on days 1 and 8 and cisplatin 75 mg/m IV over 30 to 60 minutes on day 1. Treatments were repeated every 21 days for a maximum of six cycles.

RESULTS

A total of 88 patients were enrolled in the study; seven patients were not eligible and one did not receive treatment; 80 patients were fully assessable for survival, response, and toxicity. Objective response was observed in 42 patients (53%; 95% confidence interval [CI]: 41%-64%) with two patients (3%; 95% CI: 0%-8%) achieving a complete response. Median PFS was 5 months (CI, 4.2-5.9 months), and median overall survival was 8.8 months (95% CI: 7.8-9.5 months). The 1- and 2-year survival rates were 27.5% (95% CI: 17.7%-37.3%) and 4% (95% CI: 0%-8%), respectively. The most common toxicity was neutropenia. Grade 3 and 4 neutropenia was noted in 17 (21%) and 17 (21%) patients, respectively. Two patients developed febrile neutropenia, with subsequent full recovery. Twenty-one patients (23%) developed grade 3 thrombocytopenia. Grade 4 thrombocytopenia was seen in only one patient. The most common nonhematologic toxicities included grade 3 and 4 vomiting in 12 (21%) patients and fatigue in nine (10%) patients. Two patients (3%) died of respiratory infections while on treatment.

CONCLUSION

The combination of gemcitabine and cisplatin is an active and reasonably well tolerated regimen for the treatment of ES-SCLC. It does not appear to offer any compelling advantages over other commonly used two drug regimens in this disease.

Second-line chemotherapy with weekly paclitaxel and gemcitabine in patients with small-cell lung cancer pretreated with platinum and etoposide: a single institution phase II trial

PURPOSE

The safety and efficacy of a combined regimen of weekly paclitaxel and gemcitabine was tested in patients with refractory and sensitive small-cell lung cancer (SCLC).

METHODS

Treatment consisted of paclitaxel 80 mg/m(2) on days 1, 8, 15 and gemcitabine 1,000 mg/m(2) on days 1 and 8 every 3 weeks. Of the 31 patients enrolled, 10 had refractory and 21 had sensitive disease. Objective responses occurred in 8 patients (26%), including 2 out of 10 patients with refractory- and 6 out of 21 patients with sensitive SCLC. Median time to progression and median survival were 9.4 and 32 weeks, respectively.

RESULTS

The schedule was very well tolerated, with grade 3-4 thrombocytopenia in 26% of the patients, grade 3 neutropenia in 26%, grade 3-4 asthenia in 13% and grade 1-2 sensory neuropathy in 32%.

CONCLUSION

To conclude, this weekly schedule of paclitaxel and gemcitabine was found to have moderate activity in platinum-etoposide pretreated SCLC patients and a favorable toxicity profile.

Gemcitabine monotherapy in recurrent ovarian cancer: from the bench to the clinic

Gemcitabine (2'2'-difluorodeoxycytidine [dFdC]) is a synthetic analog of deoxycytidine with two fluorine atoms at the 2' position of the carbohydrate. As a hydrophobic molecule, dFdC competes for intracellular access via membrane-associated nucleoside transporter proteins. Following intracellular transport, dFdC is phosphorylated sequentially by deoxycytidine kinase to gemcitabine triphosphate, which inhibits ribonucleotide metabolism, hinders DNA processing, and increases accumulation of intrastrand adducts and interstrand cross-links, thereby leading to a G1 block in the cell cycle. dFdC monotherapy has been extensively evaluated at doses of 800-1250 mg/m2. dFdC is generally well tolerated, with the most frequently occurring dose-limiting toxicities being hematologic, noncumulative, and easily managed by dose alteration. Several studies involving treatment of recurrent ovarian cancer patients with dFdC monotherapy, most of whom had platinum-resistant disease and/or prior exposure to paclitaxel, led to overall response rates of 14-22% and a median duration of response of 4.0-10.6 months. An additional one third of the participants experienced stable disease for an overall clinical benefit in approximately one half of the treated patients. Tumor cells with a multidrug resistance phenotype have increased sensitivity to dFdC (collateral sensitivity). As dFdC is unaffected by platinum resistance, and not susceptible to classic multidrug resistance, it could be particularly beneficial to administer following treatment with agents that induce multidrug resistance. Integration of dFdC with platinum and/or radiation should also be investigated.

Phase II trial of a 24-hour infusion of gemcitabine in previously untreated patients with advanced pancreatic adenocarcinoma

The antitumor effect of gemcitabine is not dose-response related but schedule dependent. Here we report a phase II trial of a weekly 24-hour infusion of gemcitabine in previously untreated patients with advanced pancreatic cancer. Patients with histologically proven, measurable, and irresectable pancreatic adenocarcinoma were treated with gemcitabine at a dose of 100 mg/m2 infused over 24 hr on days 1, 8, and 15. Treatment was repeated every 28 days until progression of disease or limiting toxicity. All 18 patients enrolled were evaluable for response. Neutropenia and thrombocytopenia grade 3 occurred in 1 patient each. One partial response and two minor responses were observed. Median time to progression of disease was 4.4 months. Improvement of the European Organization for Research and Treatment of Cancer C30 scores was observed in 6 patients (pain and overall symptom score, respectively) and in 3 patients (overall functioning score and global quality of life, respectively). Weekly 24-hr gemcitabine was well tolerated in previously untreated patients with advanced pancreatic cancer. It shows marginal antitumor activity in terms of response rate. However, the 24-hr infusion at a dose of 100 mg/m2 seems to be as active as the standard 30-min gemcitabine at a dose of 1000 mg/m2. Relatively long median time to progression of disease and improvement of symptom and quality-of-life scores suggest, that patients may benefit from 24-hr gemcitabine.

Phase II study of second-line gemcitabine in sensitive or refractory small cell lung cancer

Small cell lung cancer (SCLC) is highly sensitive to chemotherapy. Despite a dramatic initial response, however, most patients relapse. Given the activity of gemcitabine in non-small cell lung cancer (NSCLC), and early clinical trials suggesting activity of gemcitabine in chemo-naive SCLC patients, we conducted a phase II study to determine the efficacy and toxicities of gemcitabine in SCLC patients who have failed first-line chemotherapy. Gemcitabine 1250 mg/m(2) was given intravenously on days 1 and 8, every 3 weeks. Eligibility criteria included prior treatment with only one chemotherapy regimen and Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. Patients with brain metastases were eligible.

RESULTS

Between April 1998 and October 2001, 27 patients were enrolled: 15 patients with sensitive (S) disease (recurred>3 months after first-line chemotherapy) and 12 patients with refractory (R) disease (failed<3 months after first-line chemotherapy). Median age was 61 (range 45-74). All patients had received prior platinum-based therapy involving etoposide and either cisplatin or carboplatin. There were one early death and two early withdrawals because of toxicity. No responses were observed. Of 24 patients who received at least two cycles of gemcitabine, only three achieved stable disease after six cycles while 21 progressed. The median time to progression (TTP) was 6 weeks in S group, 5.6 weeks in R group, and 6 weeks overall. After a minimum potential follow-up of almost 1 year for all patients, the median survival was 8.8 months in S group, 4.2 months in R group, and 6.4 months for the whole group. One-year survival rate was 33.3% in S group, 16.7% in R group, and 25.4% for all patients. Myelosuppression was the most commonly observed adverse effect, with grade 3/4 neutropenia in 30%, and grade 3 thrombocytopenia in 30%. One patient (3.7%) developed neutropenic fever. Respiratory failure and death, possibly related to pulmonary toxicity, was observed in one patient (3.7%).

CONCLUSION

monotherapy gemcitabine as second-line agent has limited activity in previously treated SCLC.

Toxicity of a 24-hour infusion of gemcitabine in biliary tract and pancreatic cancer: a pilot study

The antitumor activity of gemcitabine is not dose-response related but schedule-dependent. Based on the results of a published phase I study in patients with nonsmall-cell lung cancer we started a pilot study of a 24-hr infusion of gemcitabine in patients with adenocarcinoma of the pancreas and biliary tract cancer. Twenty-five patients were enrolled and received a 24-hr infusion of gemcitabine once weekly on three consecutive out of 4 weeks. Dose levels of gemcitabine ranged from 100 to 150 mg/m2. One of 13 chemotherapy-naive patients had a partial response. Dose-limiting toxicity (DLT) was thrombocytopenia in pretreated patients and neutropenia in chemotherapy-naive patients. Other toxicities were oral mucositis, fever, flu-like symptoms, and asthenia. Maximum tolerated dose (MTD), especially in pretreated patients, was 100 mg/m2.

Collateral sensitivity to gemcitabine (2',2'-difluorodeoxycytidine) and cytosine arabinoside of daunorubicin- and VM-26-resistant variants of human small cell lung cancer cell lines

Multidrug resistance (MDR), characterized by a cross-resistance to many natural toxin-related compounds, may be caused either by overexpression of a drug efflux pump such as P-glycoprotein, (P-gP), multidrug resistance proteins MRP1-3, or BCRP/MXR or, in the case of DNA topoisomerase II active drugs, by a decrease in the enzymatic activity of the target molecule termed altered topoisomerase MDR (at-MDR). However, human small cell lung carcinoma (SCLC) cell lines showed a collateral sensitivity to 2',2'-difluorodeoxycytidine (gemcitabine, dFdC) and 1-beta-D-arabinofuranosylcytosine (ara-C). H69/DAU, a daunorubicin (DAU)-resistant variant of H69 with a P-gP overexpression, and NYH/VM, a VM-26 (teniposide)-resistant variant of NYH with an at-MDR, were both 2-fold more sensitive to gemcitabine and 7- and 2-fold more sensitive to ara-C, respectively. MDR variants had a 4.3- and 2.0-fold increased activity of deoxycytidine kinase (dCK), respectively. dCK catalyzes the first rate-limiting activation step of both gemcitabine and ara-C. In addition, deoxycytidine deaminase, responsible for inactivation of dFdC and ara-C, was 9.0-fold lower in H69/DAU cells. The level of thymidine kinase 2, a mitochondrial enzyme that can also phosphorylate deoxycytidine and gemcitabine, was not significantly different between the variants. These differences most likely caused an increased accumulation of the active metabolites (dFdCTP, 2.1- and 1.6-fold in NYH/VM and H69/DAU cells, respectively) and of ara-CTP (1.3-fold in NYH/VM cells). Ara-CTP accumulation was not detectable in either H69 variant. The pools of all ribonucleoside and deoxyribonucleoside triphosphates were at least 3- to 4-fold higher in the NYH variants compared to the H69 variants; for dCTP and dGTP this difference was even larger. The higher ribonucleotide pools might explain the >10-fold higher accumulation of dFdCTP in NYH compared to H69 variants. Since dCTP is low, H69 cells might not need a high ara-CTP accumulation to inhibit DNA polymerase. This might be related to the lack of ara-CTP in H69 variants. In addition, the increased CTP, ATP, and UTP pools in the MDR variants might explain the increased ara-CTP and dFdCTP accumulation. In conclusion, the MDR variants of the human SCLC cell lines were collaterally sensitive due to an increased dCK activity, and consequently an increased ara-CTP and dFdCTP accumulation.

Coregulation of glucose uptake and vascular endothelial growth factor (VEGF) in two small-cell lung cancer (SCLC) sublines in vivo and in vitro

We examined the relationship between (18)F- labeled 2-fluro-2-deoxy-d-glucose (FDG) uptake, and expression of glucose transporters (GLUTs) in two human small-cell lung cancer (SCLC) lines CPH 54A and CPH 54B. Changes in the expression of GLUTs and vascular endothelial growth factor (VEGF) during 12-, 18-, and 24 hours of severe hypoxia in vivo (xenografts) and in vitro (cell cultures) were recorded for both tumor lines. The two SCLC lines are subpopulations of the same patient tumor. In spite of their common genomic origin they represent consistently different metabolic and microenvironmental phenotypes as well as treatment sensitivities. There were higher levels of Glut-1 protein in 54B and a correspondingly higher FDG uptake in this tumor line (P<.001). During hypoxia a significant upregulation of in VEGF mRNA, GLUT-1 mRNA, and Glut-1 and -3 protein occurred with a distinctly different time course in the two cell lines. A similar co-upregulation of GLUT and VEGF was seen in hypoxic tumors of both lines. There were no significant changes of HIF-1alpha mRNA during hypoxia in either of the cell lines. A more detailed understanding of such correlations between glucose metabolism, angiogenesis, and microenvironmental phenotype of tumors, by positron emission tomography (PET) and molecular techniques might further sophisticate our interpretation of glycolytic predominance in tumors as seen by 18FFDG PET.