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A F Shields

Publications and source records attributed to A F Shields.

At least 19 recordsLinked to original sources
PubMed2003

Phase II study of gemcitabine, cisplatin, and infusional fluorouracil in advanced pancreatic cancer.

PURPOSE: This phase II study was undertaken to determine the efficacy of adding infusional fluorouracil (FU) to the chemotherapy doublet of gemcitabine and cisplatin in patients with advanced pancreatic cancer. PATIENTS AND METHODS: The eligibility criteria included histologically or cytologically confirmed adenocarcinoma of the pancreas that was either unresectable or metastatic. No prior gemcitabine therapy was allowed. Patients received a combination of gemcitabine 1000 mg/m2 intravenously (IV) on days 1, 8, and 15; cisplatin 50 mg/m2 IV on days 1 and 15; and FU 175 mg/m2/d from days 1 to 15 by continuous IV infusion. Cycles were repeated every 28 days. Objective tumor response and toxicity were evaluated according to the World Health Organization criteria. RESULTS: A total of 47 patients (median age, 57 years; males, 59%) were enrolled. Sixteen patients had locally advanced (LA) disease, and 31 patients had metastatic disease. A total of 183 cycles of chemotherapy were administered. In patients with metastatic disease (n = 31), the probability of survival at 6 and 12 months was 66% and 34%, respectively. Objective partial response or stable disease was observed in 26% (90% confidence interval [CI], 0.14 to 0.41) and 61% (90% CI, 0.45 to 0.74) of patients, respectively. In patients with LA disease (n = 16), there were three partial responses (19%; 90 CI, 0.07 to 0.39). One patient in this group was successfully resected after FU-based radiotherapy. The most common grade 3 to 4 toxicities were neutropenia (60%), thrombocytopenia (42%), and anemia (26%). Thirteen patients were hospitalized for treatment-related complications. CONCLUSION: The combination of gemcitabine, cisplatin, and infusional FU has significant activity in patients with advanced pancreatic cancer.

Adenocarcinoma↗
PubMed2003

Developments in the systemic therapy of pancreatic cancer.

Pancreatic adenocarcinoma is the fourth leading cause of cancer mortality in the United States of America. Progress in the treatment of this disease in the past several decades has been very modest. Several new agents with activity against pancreatic cancer have been identified. Of these, gemcitabine is the most promising agent when used in combination with other drugs. Pilot phase II studies combining gemcitabine with 5-flourouracil, irinotecan, docetaxel, or cisplatin show improved outcomes in objective response rates and survival that need to be confirmed in larger randomized studies. Advancement in the understanding of the molecular biology of neoplasia in recent years has helped identify several molecular targets for future new drug development in pancreatic cancer. Assessment of response to therapy of pancreatic cancer has been a difficult challenge. Functional imaging with techniques such as positron emission tomography (PET) may yield a more precise and timely objective evaluation of response to treatment.

Adenocarcinoma↗
PubMed2002

A single-institution experience with concurrent capecitabine and radiation therapy in gastrointestinal malignancies.

PURPOSE: We report our clinical experience with 32 patients receiving concurrent irradiation and capecitabine. METHODS AND MATERIALS: Medical records of patients with gastrointestinal malignancies treated with radiation and capecitabine therapy were reviewed. RESULTS: The population consisted of 20 males and 12 females, with a median age of 67.5 years (45-84 years) and adequate hepatic and bone marrow function. Histology was adenocarcinoma in all patients, except two with esophageal squamous carcinoma. Twenty-one patients received the regimen as adjuvant therapy, three received preoperative therapy, and 8 patients received therapy for palliation. The median dose of capecitabine was 1600 mg/m(2)/day (1200-2500 mg/m(2)/day) orally for 5 days per week for the duration of radiation therapy. Thirty patients received a total dose ranging from 45 Gy to 64 Gy over 4-6 weeks. Two previously radiated patients received total doses of 29.9 Gy and 46 Gy. Grade 3/4 toxicities observed were neutropenia in 3 patients and diarrhea, thrombocytopenia, fatigue, and myocardial infarction in 1 patient each. No treatment-related mortality was observed. Twenty of 21 patients (95.2%) who received adjuvant therapy continue to be in complete remission. Four of 11 (36%) evaluable patients demonstrated a response. CONCLUSION: Concurrent capecitabine and radiation were very well tolerated and warrant further investigation in prospective trials.

Adenocarcinoma↗
PubMed2001

Phase II study of gemcitabine and cisplatin in the treatment of patients with advanced pancreatic carcinoma.

BACKGROUND: Pancreatic carcinoma is considered among the most chemoresistant of human malignancies. The most commonly used cytotoxic single agents, 5-fluorouracil and 2'-deoxy-2',2'-difluorocytidine (gemcitabine), have objective response rates of less than 10% in large studies. Hypothesizing noncross resistance and a synergistic interaction between gemcitabine and cisplatin, early clinical studies have demonstrated significant activity with this combination in patients with several types of malignant disease. A Phase II study was undertaken to determine the efficacy of gemcitabine in combination with cisplatin in patients with locally advanced and metastatic pancreatic carcinoma based on these considerations. METHODS: The eligibility criteria included histologically confirmed, locally advanced, unresectable or metastatic exocrine carcinoma of the pancreas with no prior gemcitabine therapy; prior adjuvant therapy was allowed provided the last day of therapy was at least 6 months prior to starting treatment; clinically measurable or evaluable disease; a Southwest Oncology Group scale performance status of 0-2; a life expectancy of > 12 weeks; and adequate bone marrow, hepatic, and renal function. A total of 42 patients, 4 patients with locally advanced, unresectable disease and 38 patients with metastatic disease, were treated and received a total of 211 cycles of therapy between May 1997 to March 1999. The median age of patients was 61.5 years. The patients were treated in the outpatient setting with a combination of gemcitabine 1,000 mg/M(2) intravenously over 30 minutes administered on Days 1, 8, and 15 of each cycle and cisplatin 50 mg/M(2) intravenously administered after gemcitabine infusion on Days 1 and 15 with adequate prehydration accompanied by adequate urinary output. Cycles were repeated every 28 days. Response and toxicity were assessed according to World Health Organization and standard criteria. RESULTS: The complete and partial response rate among all 42 registered patients was 11 of 42 patients (26%; 95% confidence interval, 0.14-0.42). Stabilization of disease was seen in 15 patients (38%). Two additional patients with metastatic disease who achieved major responses to chemotherapy were rendered free of disease surgically, achieving a complete response status. The median overall survival was 7.1 months (95% confidence interval [CI], 6.3-9.1 months), with 64% of patients alive at 6 months and 19% of patients alive at 12 months. The median time to disease progression was 5.4 months (range, 0.9-20.8 months). Major toxicities were neutropenia and thrombocytopenia, with one episode of neutropenic fever. CONCLUSIONS: The combination of gemcitabine and cisplatin appeared to have significantly greater activity than single-agent gemcitabine in this Phase II study, with tolerable toxicity. The antitumor activity of this combination needs to be confirmed in multi-institutional or comparative trials.

Adult↗
PubMed2001

Phase II study of liposomal doxorubicin in patients with advanced colorectal cancer.

Doxil is a liposomal preparation of doxorubicin that results in prolonged pharmacologic exposure in vivo to the active agent. We sought to test the hypothesis that this new formulation would result in improved efficacy in patients with colorectal cancer. Patients with advanced colorectal cancer who had received prior therapy were eligible for the trial. Treatment consisted of Doxil 45 mg/m2 intravenously every 3 weeks. Seventeen patients entered the trial and they received a median of two cycles of treatment. None of the patients had a partial response to treatment. Stable disease was the best response, and one patient received therapy for 17 cycles before her disease progressed. The therapy was well tolerated, with only two patients having the dose decreased because of hand-foot syndrome. Four patients experienced allergic reactions during the infusion, but with appropriate premedication and slowing of the infusion, treatment was able to be resumed without difficulty. No greater than grade I neutropenia or thrombocytopenia developed in any patient. Although Doxil was well tolerated at this dose and schedule, it was not an active agent in this group of patients. Doxil alone or in combination with other agents is worthy of further study in cancers responsive to doxorubicin.

Adult↗
PubMed2001

Expression of inflammatory modulator COX-2 in pancreatic ductal adenocarcinoma and its relationship to pathologic and clinical parameters.

Despite the exceedingly poor prognosis of pancreatic cancer, it is often histologically well to moderately differentiated. The apparent resistance to conventional therapeutic modalities is poorly understood and may be related to the molecules involved in its progression or its propensity for perineurial invasion. Cyclooxygenase-2 (COX-2) is an inducible enzyme homologous to COX-1 that is responsible for production of prostaglandins at sites of inflammation. It is activated by a variety of growth factors and tumor promoters, and it has been implicated in cancer progression. It may also have a role in the resistance to therapy. Anti-COX-2 agents have been documented to have antitumor activity, and some are now being tested in the therapy for various cancers, including those of the pancreas. Experience regarding the rate of COX-2 expression in pancreatic cancer and its relationship to the clinical and biologic parameters is very limited. In this study, immunohistochemical stains for COX-2 have been performed on 120 cases of pancreatic ductal adenocarcinoma. The stains were scored according to the percentage (0: no staining, 1: < 10%, 2: 10-50%, and 3: >50% of the cells staining) and intensity (0 for no staining, 1 for mild staining, and 2 for dark staining) of staining. Based on the combined score for each case, they were divided into low expressors (percentage and intensity < or =1) and high expressors (percentage or intensity >1). In addition to global scoring for each case, the glandular and solid (poorly differentiated) components, when present, were scored separately. The global scores were correlated with clinical and biologic parameters. Seventy-four percent of the cases exhibited expression of COX-2 and 53% were high expressors. No significant association was observed when comparing the global COX-2 expression to survival, tumor size, stage, and vascular invasion. Increased perineural invasion was found to be significantly associated with COX-2 expression (p < 0.05). Increased expression was also more common in the glandular component as compared with the solid component of the tumors (68% versus 35%, p < 0.05). Of the 34 patients who received radiotherapy, 9 were low expressor (median survival 19.5 months) and 25 were high expressors (median survival 14 months). The difference in survival was not statistically significant.

Adult↗
PubMed2001

A phase II trial of bryostatin 1 in the treatment of metastatic colorectal cancer.

Current chemotherapy for patients with advanced colorectal cancer is relatively ineffective and may be associated with significant toxicity. Bryostatin 1 (bryo 1) influences cell proliferation, intracellular metabolism and signaling, differentiation, and apoptosis in human cancer cell lines via modulation of protein kinase C (PKC) activity. This trial investigates the efficacy and toxicity of bryo 1 as a novel therapeutic agent for patients with advanced colorectal cancer who have had previous 5-fluorouracil therapy. The primary end point was tumor response to bryo 1. Toxicity was also assessed. Twenty-eight patients with advanced colorectal cancer were enrolled. The mean age was 59 years (range, 38-76), with 16 men and 12 women, and good minority representation (11 African-Americans). The first 10 patients initially received 25 microg/m2 of bryo 1 weekly as a 24-h infusion for 3 weeks of every 4-week cycle, with dose escalation to 35 microg/m2 starting with the second cycle. The remaining patients were started at 35 microg/m2 and escalated to 40 microg/m2, if toxicity was minimal. Twenty-five patients were evaluable for objective tumor response, and complete data on toxicity were collected on 26 patients. No partial or complete tumor responses were observed. All 25 patients had disease progression within four cycles. Myalgia was the most common toxicity. Myelosuppression was not seen. bryo 1 as a weekly 24-h continuous infusion lacks single-agent antitumor activity in advanced colorectal cancer. Toxicity differs from that of traditional chemotherapeutic drugs.

Adult↗
PubMed2000

Cost analysis of pancreatic carcinoma treatment.

BACKGROUND: Pancreatic carcinoma is a major health issue and financial burden to society. To improve the quality and efficiency of care delivered, it is essential for health care providers to have a good understanding of the cost of treatment. METHODS: The authors examined the facility-based costs and survival of 103 patients with pancreatic carcinoma who were treated at the Karmanos Cancer Institute between January 1992 and September 1998. Longitudinal cost data for each patient were obtained, and from those data, 6-month, 1-year, and lifetime total treatment costs were calculated. RESULTS: The average 6-month, 1-year, and lifetime total treatment costs were $37,327, $42,218, and $48,803, respectively, and the median survival was 7 months. In univariate analyses, the disease stage at diagnosis was a highly significant predictor of total cost. Patients with metastatic disease had the lowest cost, and patients with resectable disease had the highest cost. In multivariate analyses controlling for disease stage, treatment strategies and dual insurance coverage were also important predictors of costs but patient age, race, and gender were not predictive. Disease stage also was highly predictive of survival. In a multivariate analysis controlling for disease stage, chemotherapy and radiation therapy were correlated with longer survival, whereas resection and palliative bypass surgery were not. CONCLUSIONS: The costs of treating patients with pancreatic carcinoma are considerable, even though survival duration typically is short. Disease stage was the most dominating factor determining costs and survival. After controlling for disease stage, chemotherapy, surgery, and dual insurance coverage were also significantly associated with higher cost of care. However, in survival analyses, only chemotherapy and radiation therapy were associated with a significant increase in patient survival.

Aged↗
PubMed2000

Radiosynthesis of 3'-deoxy-3'-[(18)F]fluorothymidine: [(18)F]FLT for imaging of cellular proliferation in vivo.

A reliable radiosynthesis of 3'-deoxy-3'-[(18)F]fluorothymidine ([(18)F]FLT) has been developed based on [(18)10 mCi (370 MBq) of radiochemically pure [(18)1 Ci/micromol (37 GBq/micromol) at EOS within 100 min and in 13% radiochemical yield (end of bombardment (EOB); 7% end of synthesis (EOS)). [(18)F]FLT has been designed as a new positron emission tomography imaging agent for visualizing cellular proliferation in vivo based on the metabolism of thymidine.

Cell Division↗
PubMed2000

Cisplatin, cytarabine, caffeine, and continuously infused 5-fluorouracil (PACE) in the treatment of advanced pancreatic carcinoma: a phase II study.

Encouraging results using cisplatin, cytarabine, and caffeine for the treatment of pancreatic carcinoma prompted a phase II study using these agents and adding continuous intravenous infusion (CI) 5-fluorouracil (5-FU) (PACE). Patients with advanced pancreatic adenocarcinoma who had not received prior cytotoxic therapy were eligible. Treatment consisted of the following: on day 1, the administration of cisplatin 100 mg/m2 IV, cytarabine 2 g/m2 IV every 12 hours x 2 doses, and caffeine 400 mg/m2 subcutaneously after each cytarabine dose; and on days 3 to 21, 5-FU 250 mg/m2/day given by CI. Cycles were repeated every 28 days. Thirty eligible patients were entered in the study. The median number of cycles received was three. Grade IV neutropenia and thrombocytopenia occurred in 53% and 27% of patients, respectively. Among 30 treated patients, complete remission (CR) was seen in 2 patients and partial remission (PR) in 3 patients, for an overall response rate of 16.7% (95% confidence interval 6.8-32.4%). The median survival was 5.0 months (range: 0.3-32.4 months) and 16.7% and 10% of patients were alive at 1 and 2 years. respectively. Changes in the serum level of CA 19-9 provided an early marker of response which translated in differences in survival. Those with increasing or decreasing/stable levels of CA 19-9 after the first cycle of therapy had median survivals of 1.7 and 8.3 months, respectively (p = 0.0002). Although PACE chemotherapy produced durable responses in pancreatic cancer, the toxicity was substantial. A modification of this regimen with newer, less toxic drugs may provide better results and reduced toxicity. Also, the monitoring of the serum CA 19-9 level may provide a means to assess response and predict survival.

Adenocarcinoma↗
PubMed1999

Phase II study of CI-958 in colorectal cancer.

PURPOSE: We completed a phase II trial of CI-958 (NSC 635371) in patients with advanced colorectal cancer given at a dose of 700 mg/m2 every 21 days. METHODS: All 15 patients had metastatic disease and had been previously treated with one 5-fluorouracil-based regimen in an adjuvant (six) or metastatic (nine) setting. RESULTS: None of the patients treated with CI-958 had an objective response to treatment. Median survival was 4.8 months after the start of treatment. Leukopenia was the major toxicity, but no patient experienced febrile neutropenia. An acute febrile reaction was seen after infusion in four of the first nine patients treated. This was abrogated by pretreatment with dexamethasone in the remaining patients. CONCLUSIONS: CI-958 was not effective at this dose and schedule in patients with previously treated advanced colorectal cancer.

Adenocarcinoma↗
PubMed1999

Kinetic analysis of 2-[11C]thymidine PET imaging studies: validation studies.

UNLABELLED: 2-[11C]thymidine has been tested as a PET tracer of cellular proliferation. We have previously described a model of thymidine and labeled metabolite kinetics for use in quantifying the flux of thymidine into DNA as a measure of tumor proliferation. We describe here the results of studies to validate some of the model's assumptions and to test the model's ability to predict the time course of tracer incorporation into DNA in tumors. METHODS: Three sets of studies were conducted: (a) The uptake of tracers in proliferative tissues of normal mice was measured early after injection to assess the relative delivery of thymidine and metabolites of thymidine catabolism (thymine and CO2) and calculate relative blood-tissue transfer rates (relative K1s). (b) By using sequential injections of [11C]thymidine and [11C]thymine in normal human volunteers, the kinetics of the first labeled metabolite were measured to determine whether it was trapped in proliferating tissue such as the bone marrow. (c) In a multitumor rat model, 2-[14C]thymidine injection, tumor sampling and quantitative DNA extraction were performed to measure the time course of label uptake into DNA for comparison with model predictions. RESULTS: Studies in mice showed consistent relative delivery of thymidine and metabolites in somatic tissue but, as expected, showed reduced delivery of thymidine and thymine in the normal brain compared to CO2. Thymine studies in volunteers showed only minimal trapping of label in bone marrow in comparison to thymidine. This quantity of trapping could be explained by a small amount of fixation of labeled CO2 in tissue, a process that is included as part of the model. Uptake experiments in rats showed early incorporation of label into DNA, and the model was able to fit the time course of uptake. CONCLUSION: These initial studies support the assumptions of the compartmental model and demonstrate its ability to quantify thymidine flux into DNA by using 2-[11C]thymidine and PET. Results suggest that further work will be necessary to investigate the effects of tumor heterogeneity and to compare PET measures of tumor proliferation to in vitro measures of proliferation and to clinical tumor behavior in patients undergoing therapy.

Animals↗
PubMed1998

Evaluation of pyrazoloacridine in patients with advanced pancreatic carcinoma.

PURPOSE: Pyrazoloacridine (PZA) is an acridine derivative selected for clinical development because of broad pre-clinical antitumor activity and solid tumor selectivity. Phase I evaluations with PZA have demonstrated predictable toxicity and suggested clinical efficacy. A phase II trial in patients with previously untreated advanced pancreatic cancer was conducted. METHODS: PZA was administered at a dose of 750 mg/m2 intravenously over 3 hours every 21 days. Seventeen patients were treated receiving a total of 46 courses of PZA. RESULTS: Of the 15 patients evaluable for response, no responses were observed (0% response rate, 95% confidence interval 0-22%). Major toxicities directly attributable to PZA included moderate neutropenia and mild neurotoxicity. CONCLUSION: PZA at this dose and schedule of administration was inactive in patients with pancreatic carcinoma.

Acridines↗
PubMed1998

Imaging proliferation in vivo with [F-18]FLT and positron emission tomography.

Positron emission tomography (PET) is now regularly used in the diagnosis and staging of cancer. These uses and its ability to monitor treatment response would be aided by the development of imaging agents that can be used to measure tissue and tumor proliferation. We have developed and tested [F-18]FLT (3'-deoxy-3'-fluorothymidine); it is resistant to degradation, is retained in proliferating tissues by the action of thymidine kinase 1 (TK), and produces high-contrast images of normal marrow and tumors in canine and human subjects.

Animals↗
PubMed1998

Establishment of a human pancreatic tumor xenograft model: potential application for preclinical evaluation of novel therapeutic agents.

Adenocarcinoma of the pancreas is currently the fifth leading cause of death in the United States. It remains generally incurable by available treatment modalities. We report here on the characterization of a permanent pancreatic cell line (KCI-MOH1), established as a xenograft in severe combined immune deficient (SCID) mice, from a 74 year-old African American male patient diagnosed with pancreatic cancer. Sections from paraffin-embedded tumors excised from SCID mice revealed typical adenocarcinoma of the pancreas. Karyotypic analysis of cultured cells derived from tumors grown in SCID mice revealed a male karyotype with multiple clonal aberrations: 42, XY, add (3)(p11.2), der(7) t(7;12) (p22;q12), -10, -12, add (14)(p11), -18, add (20)(q13)-22/84, idemx2. Immunostaining of KCI-MOH1 tissues shows strong expression of p53 and p21 proteins. The xenograft model was established by transplanting the KCI-MOH1 cells subcutaneously (s.c.) in SCID mice. When the s.c. tumor was transplanted in vivo to other SCID mice, the success rate was 100%, with a doubling time of 8.5 days. The SCID mouse xenograft model was used to test the efficacy of selected standard chemotherapeutic drugs (taxol, gemcitabine, 5-fluorouracil, and Ara-C) and novel biological agents (Bryostatin 1 and Auristatin-PE). Results show that gemcitabine, Ara-C, and Bryostatin 1 were active against KCI-MOH1. The xenograft described herein can be used as an animal model to facilitate the development of novel therapeutic agents against human pancreatic cancers.

Adenocarcinoma↗
PubMed1998

Kinetic analysis of 2-[carbon-11]thymidine PET imaging studies: compartmental model and mathematical analysis.

UNLABELLED: Carbon-11-thymidine is a PET tracer of DNA synthesis and cellular proliferation. Quantitative analysis of [11C]thymidine images is complicated by the presence of significant quantities of labeled metabolites. Estimation of the rate of thymidine incorporation into DNA using [11C]thymidine requires a kinetic model that is capable of describing the behavior of thymidine and labeled metabolites. METHODS: Based on previous studies with labeled thymidine, we constructed a five-compartment model describing the kinetic behavior of 2-[11C]thymidine and its labeled metabolites. In addition, we have performed a series of calculations and simulations to calculate the sensitivity and identifiability of model parameters to estimate the extent to which individual parameters can be estimated; to determine appropriate model constraints necessary for reproducible estimates of the constant describing flux of thymidine from the blood into DNA, i.e., thymidine flux constant; and to determine the potential accuracy of model parameter and thymidine flux constant estimates from PET imaging data. RESULTS: The underlying assumptions in the thymidine compartmental model lead to a description of the thymidine flux constant for DNA incorporation in terms of model parameters. Sensitivity and identifiability analyses suggest that the model parameters pertaining to labeled metabolites will be difficult to estimate independently of the thymidine parameters. Exact evaluation of the kinetic parameters of the labeled metabolites is not the principal goal of this model. Simulations were performed that suggest that it is preferable to tightly constrain these parameters to preset values near the center of their expected ranges. Although it is difficult to estimate individual thymidine model parameters, the flux constant for incorporation into DNA can be accurately estimated (r > 0.9 for estimated versus true simulated flux constant). Flux constant estimates are not affected by modest levels of local degradation of thymidine that may occur in proliferating tissue. CONCLUSION: By using a kinetic model for thymidine and labeled metabolites, it is possible to estimate the flux of thymidine uptake and incorporation into DNA and, thereby, noninvasively estimate regional cellular proliferation using [11C]thymidine and PET.

Carbon Radioisotopes↗
PubMed1998

5-Fluoro-1-(2'-deoxy-2'-fluoro-beta-D-ribofuranosyl) uracil trapping in Morris hepatoma cells expressing the herpes simplex virus thymidine kinase gene.

UNLABELLED: The planning and individualization of gene therapy with suicide genes such as herpes simplex virus thymidine kinase (HSV-tk) necessitates the assessment of the enzyme activity expressed in the tumor. This can be done by uptake measurements of specific substrates for HSV-tk. Due to the molecular structure of 5-fluoro-1-(2'-deoxy-fluoro-beta-D-ribofuranosyl)uracil (FFUdR), it may be a substrate for both the mammalian thymidine kinase and HSV-tk. METHODS: Using a HSV-tk-expressing rat hepatoma cell line and a control cell line (bearing the empty vector) the uptake of 3H-FFUdR was determined with increasing incubation periods. Furthermore, measurements with graded mixtures of HSV-tk-expressing cells and control cells were made. To elucidate the mechanism of FFUdR transport into cells, a series of inhibition/competition experiments was performed with challenge inhibitors of the nucleoside and the nucleobase transport systems. RESULTS: The uptake studies with tritiated FFUdR revealed a 14- to 19-fold higher accumulation in the HSV-tk-expressing cell line compared to the control cell line. While the 3H-FFUdR uptake was 3- to 4-fold higher than the 3H-ganciclovir uptake in the HSV-tk-expressing cells, it was also higher in control cells (5-fold). Furthermore, FFUdR accumulation was linearly correlated with the amount of HSV-tk-expressing cells. FFUdR uptake and growth inhibition by therapeutic doses of ganciclovir were highly correlated, with r = 0.96. Inhibition/competition experiments showed that FFUdR is transported mainly by the equilibrative and the concentrative nucleoside transporter but not by the nucleobase transport systems. CONCLUSION: The FFUdR uptake is an indicator of the HSV-tk activity in tumor cells and can be used as a prognostic marker during gene therapy with HSV-tk. The relative merits of ganciclovir and FFUdR as specific substrates for HSV-tk will need to be further explored in vivo.

Animals↗