Imaging tumor folate receptors using 111In-DTPA-methotrexate

It is known that membrane folic acid receptors are responsible for cellular accumulation of folate and folate analogs, such as methotrexate, and overexpressed on various tumor cells. This study was aimed to develop an 111In labelled DTPA-methotrexate (DTPA-MTX) to image tumor folate receptors in vivo. DTPA-MTX was synthesized by reacting ethylenediamine with MTX. The resulting amino analogue of MTX was reacted with DTPA dianhydride in basic aqueous solution followed by dialysis. Tissue distribution was determined in breast tumor-bearing rats at 0.5, 2, 24, and 48 h (n = 3/time interval). To determine receptor-mediated process 111In-DTPA-MTX was co-administrated with varying blocking doses of cold folate to tumor-bearing rats. Planar imaging and whole-body autoradiograms were performed. The data was compared to that using 111In-DTPA. In animal studies, tumor/blood count density ratios at 0.5-48 h gradually increased from 0.8 +/- 0.32 to 2.2 +/- 0.41 with 111In-DTPA-MTX. Conversely, these values showed time-dependent decrease from 1.19 +/- 0.69 to 0.56 +/- 0.10 with 111In-DTPA in the same time period. Tumor/muscle and tumor/blood count density ratios significantly decreased with high doses of folic acid co-administration. Planar images and autoradiograms confirmed that the tumors could be visualized acceptably with 111In-DTPA-MTX. The results indicate the feasibility of using 111In-DTPA-MTX to image tumors through a folate receptor-mediated process.

Role of indium-111 labelled platelet scintigraphy in the management of thrombocytopenic patients with malignant neoplasms

This study was done to investigate the role of indium-111 labelled platelet scintigraphy in the treatment of thrombocytopenia in patients with malignant neoplasms. The study involved 20 consecutive patients with thrombocytopenia associated with malignant neoplasms of hematological disorders and without evidence of underproduction of megakaryocytes due to chemotherapy or bone marrow infiltration by the malignancy. Splenic sequestration of platelets was evaluated by measuring splenic uptake of 111In-labelled platelets, and findings were correlated with the outcome of splenectomy and medication. Of the 20 patients, 13 had splenic sequestration of platelets. Seven of the 13 patients underwent splenectomy; six of these seven patients experienced a complete response. The other six patients received medication only and showed no response. Of the seven patients without splenic sequestration of platelets, five received medication, and four of them responded to it. 111In-labelled platelet scintigraphy has a role in selecting appropriate therapy and predicting its efficacy in patients with thrombocytopenia associated with malignant neoplasms.

Detection of primary breast cancer presenting as metastatic carcinoma of unknown primary origin by 111In-pentetreotide scan

Women with isolated metastatic carcinoma or adenocarcinoma involving axillary lymph nodes are a well-recognized group of unknown primary carcinoma (UPC) patients with a favorable prognosis. This group of patients are generally treated based on the assumption that they have occult breast cancer. However, to facilitate patient access to the whole spectrum of therapies available for patients with breast cancer, including strategies involving the use of high-dose chemotherapy, a precise diagnosis is increasingly important. In this clinical case we report the detection of a primary breast cancer by 111In-pentetreotide scanning in a woman who presented with metastatic carcinoma in axillary nodes, no palpable breast lesion, a nondiagnostic mammogram, and negative breast ultrasonography. Previous outcomes analysis of patients with UPC have emphasized the value of identifying women with breast cancer. This report suggests that the 111In-pentetreotide scan can contribute specific, clinically useful information in the evaluation of women presenting with metastatic carcinoma in axillary nodes and an occult primary and deserves prospective study in women with UPC presenting with isolated axillary metastases.

Isolated limb perfusion in the sarcoma-bearing rat: a novel preclinical gene delivery system

Reliable site-specific delivery of genetic constructs remains a challenging component of gene-based therapy of solid tumors. Isolated limb perfusion (ILP) continues to be evaluated for treatment of locally advanced soft tissue sarcomas because this approach uniquely directs therapeutic agents into the tumor-bearing extremity without significant systemic leak. In light of these considerations, we tested the hypothesis that ILP could be used to deliver genes carried in viral vectors to the sarcoma-bearing rat extremity, resulting in demonstrable gene transfer into the tumor. ILP was performed in rats by cannulating the femoral artery and vein, isolating the hind limb from systemic circulation by tourniquet, and cycling perfusate for 15 min at a rate of 2.4 ml/min. Leakage into the systemic circulation was 7.5% of the total perfusate concentrated in the isolated limb, as determined by perfusion with technetium 99m-tagged RBCs. We used the ILP technique to perfuse rat hind limbs bearing syngeneic fibrosarcoma tumor nodules with the replication-defective adenovirus Ad5LacZ, which expresses the bacterial beta-galactosidase. 5-Bromo-4-chloro-3-indolyl-beta-D-galactoside staining of the perfused limb tissues confirmed gene transfer to the tumor and peritumoral tissue, demonstrating that the tumor was part of the perfusion circuit and that gene therapy delivered via this method was feasible. These results suggest that adaptation of this preclinical gene delivery model to administer genetic constructs aimed at controlling tumor growth may prove beneficial to patients with extremity sarcomas.

Erdheim-Chester disease demonstrated by bone radiograph and scans

Two cases of patients with Erdheim-Chester disease (EC) are presented with interesting scintigraphic findings. Differential diagnosis of bone scan and radiographic findings is briefly discussed.

Preliminary study of cardiac accumulation of F-18 fluorotamoxifen in patients with breast cancer

The clinical meaning of cardiac uptake of [18F]fluorotamoxifen was assessed. Tamoxifen, a nonsteroidal antiestrogenic drug for treatment and prevention of breast cancer, has a cardioprotective, estrogen-like effect in postmenopausal women. We conducted a pilot study of [18F]fluorotamoxifen to evaluate its clinical usefulness in patients with breast cancer. Significant cardiac uptake of [18F]fluorotamoxifen in five patients was found in the pilot study. We performed positron emission tomography (PET) with [18F]fluorotamoxifen. The intracardiac distribution of [18F]fluorotamoxifen was observed and compared with the patients' clinical symptoms, past history, and results of the electrocardiogram (ECG). None of the patients had a prior history of ischemic heart disease. Various patterns of [18F]fluorotamoxifen distribution were seen in the heart: one patient showed homogeneous distribution; two had defects in the lateral wall; one had patchy distribution; and in one the uptake was questionable. Non-uniform cardiac uptake may be related to myocardial damage. Cardiac uptake of tamoxifen suggests that its cardioprotective benefits may be related not only to serum cholesterol reduction but also to a direct cardioprotective action. Further experimental studies are required to elucidate the pathophysiological mechanism of cardiac uptake of [18F]fluorotamoxifen.

A phase II and pharmacokinetic study of enloplatin in patients with platinum refractory advanced ovarian carcinoma

This was a study of enloplatin in 18 evaluable patients with platinum refractory ovarian cancer. They received an i.v. infusion of enloplatin over 1.5 h without prehydration every 21 days. One patient had a partial response (6%; 95% CI 0-26%) lasting 2.8 months. The median survival was 9.4 months (95%; CI 5.1-19.7%). Neutropenia was the dose-limiting toxicity. Nephrotoxicity was manageable. Enloplatin is the major form of the free drug in plasma. However, 13.5 h after initiation of treatment, 85% of the drug in plasma is protein bound. Elimination of the drug is mainly renal. Enloplatin pharmacokinetics is similar to that of carboplatin. Thus, the plasma pharmacokinetics of enloplatin is dictated by the cyclobutanedicarboxylato (CBDCA) ligand and not the novel amino ligand.

Synthesis, biodistribution and imaging properties of indium-111-DTPA-paclitaxel in mice bearing mammary tumors

Paclitaxel, an antineoplastic agent that stabilizes microtubules and arrests cells in the G2/M cell cycle phase, has shown activity against many common cancers, including ovarian and breast tumors. In order to evaluate the potential value of radiolabeled paclitaxel as an imaging tool in tumors, we synthesized 111In-DEPA-paclitaxel and investigated its biodistribution and gamma scintigraphic imaging properties.

METHODS

Mice bearing a paclitaxel-responsive mammary tumor (MCA-4) were used. DTPA-paclitaxel was labeled with 111In with a radiochemical yield of 84% and radiochemical purity of 90%. Each mouse received 5 microCi of radiotracers intravenously for biodistribution studies and 100 microCi for gamma scintigraphic studies. Indium-111-DTPA was used as a control.

RESULTS

In tumor-bearing mice, 111In-DTPA was characterized by rapid clearance from the plasma with negligible retention in the tumor, the liver and other body parts. In contrast, 111In-DTPA-paclitaxel exhibited a pharmacological profile resembling that of paclitaxel. Furthermore, a significant uptake of 111In-DTPA-paclitaxel was observed in the tumor. The tumor-to-muscle ratios were 2.64, 3.16 and 6.94 at 30 min, 2 hr and 24 hr, respectively, although absolute uptake in the tumor decreased from 1.95% (injected dose/g) at 30 min to 0.21% at 24 hr after injection. The tumor-to-blood ratio reached 50 at 24 hr after injection. Gamma scintigraphy and autoradiographic studies clearly showed the retention of radiolabeled paclitaxel in the tumor 24 hr after injection.

CONCLUSION

These studies suggest that 111In-DTPA-paclitaxel may be clinically useful in studying the uptake of paclitaxel in solid tumors.

Correlation between bone scan findings and collagenase activities in patients with breast cancer

RATIONALE AND OBJECTIVES

This study correlates nuclear bone scan findings and measurements of type IV collagenases for the evaluation of bony metastasis in patients with proven breast cancer.

METHODS

The authors retrospectively evaluated the final diagnosis of a bone scan and the results of an immunohistochemical staining for 92 kDa and 72 kDa type IV collagenases in, respectively, 30 and 30 patients with metastatic breast cancer, and, respectively, 27 and 26 patients with primary breast cancer. The immunohistochemical staining was performed with tissue specimens obtained from a primary or metastatic breast tumor lesion. The amounts of the enzyme were graded from 0 to 4 and scored by multiplication with the percentage of tumor cells. The confidence of bone scan interpretation also was scored from 1 to 5 with increasing probability.

RESULTS

There was a significant difference in enzyme scores between patients with and without metastases. Patients with < 170 92 kDa (26 of 27), 72 kDa (26 of 26) type IV collagenase, showed no active bony, lung, or liver metastases. However, there were variable bone scan findings in patients with a > 200 enzyme score.

CONCLUSIONS

Bone scan provides no additional benefit in breast cancer patients with a type IV collagenase score of < 170. A bone scan is necessary to confirm, localize, or followup bony metastases in patients with an enzyme score of > 200.

Evaluation of [131I]iodoerythronitroimidazole as a predictor for the radiosensitizing effect

The aim of this study was to evaluate whether radiolabeled iodoerythronitroimidazole (IETNIM) could predict the radiosensitization effect on tumors. Tumor-bearing mice were irradiated at a dose of 25, 31 and 37 Gy after the injection of IETNIM. They were also exposed to 37 Gy radiation at 35, 70, 140 and 240 min after the i.p. injection of IETNIM. After the irradiation, tumor growth assays were conducted and the effect of IETNIM as a radiosensitizer was estimated as enhancement factor (EF). Tumor uptake was measured at 35, 70, 140 and 240 min after i.p. injection of [131I]IETNIM, which were the same intervals used in the radiosensitization study. EF of IETNIM in mice treated with 25, 30 and 37 Gy irradiation was 0.72, 0.98 and 1.28, respectively. EF of IETNIM in mice irradiated at 35, 70, 140 and 240 min after the injection was 1.50, 1.69, 1.46 and 1.08, which corresponded to the tumor uptake and blood clearance of [131I]IETNIM. [131I]IETNIM may be a suitable radiopharmaceutical to predict the radiosensitization effect of misonidazole analogs on tumors.

Comparison of fluorine-18-FDG PET and technetium-99m-MIBI SPECT in evaluation of musculoskeletal sarcomas

We compared the diagnostic accuracy of [18F]FDG PET and 99mTc-MIBI SPECT in musculoskeletal sarcomas.

METHODS

Forty-eight patients with clinically suspected recurrent or residual musculoskeletal sarcomas were examined with both FDG-PET and MIBI-SPECT within 2 wk of each study (one follow-up study in nine patients and we follow-up studies in one patient). Imaging findings were visually inspected with grading scales in conjunction with CT and/or MRI, and count-density ratios of lesion-to-contralateral area and standard uptake values (SUVs) of FDG and MIBI in lesions were also generated. The results were correlated with histologic findings (in 51 studies) and/or long-term follow-up evaluations.

RESULTS

The diagnostic sensitivities and specificities were 98% and 90% using FDG, and 81.6% and 80% using MIBI, respectively, with statistical significance in the sensitivity. The tumors were demonstrated better in FDG studies, which produced higher visual grades (2.1 versus 1.6), and the tumors showed increasing SUVs with time (from 6.3 to 7.3). Four of nine patients with positive FDG but negative MIBI scans failed to respond to multidrug therapy.

CONCLUSION

FDG-PET and MIBI-SPECT are useful in differentiating active sarcomas from post-treatment changes and in evaluating therapeutic response. MIBI-SPECT and FDG-PET findings should be interpreted in con junction with CT and/or MRI. FDG-PET shows statistically significant higher sensitivity than MIBI-SPECT. A positive FDG but negative MIBI scan might suggest a multidrug resistance.

Comparison of fluorine-18-fluorodeoxyglucose and carbon-11-methionine PET in detection of malignant tumors

Two commonly used tumor-seeking agents for PET are 2-deoxy-2-18F-fluoro-D-glucose (FDG) and L-methyl-11C-methionine (Met). This study compared FDG and Met in detecting residual or recurrent malignant tumors in the same patients.

METHODS

Thirty-four lesions in 24 patients with clinically suspected recurrent or residual tumors were studied with PET using Met as well as FDG. FDG scans were conducted 1 hr after the completion of PET with Met. The color-coded superimposed images of standardized uptake values (SUVs) and transmission data were produced, and the peak SUVs in the lesions were then evaluated. Lesions above 2.5 SUV were interpreted as positive results for active tumor.

RESULTS

The sensitivity of FDG-PET and Met-PET were 64.5% (20/31 lesions) and 61.3% (19/31 lesions), respectively. The mean SUV of FDG in residual or recurrent malignant tumors (n = 31) was significantly higher than that of Met but there was a significant correlation (r = 0.788, p < 0.01) between FDG and Met SUVs in all lesions (n = 34).

CONCLUSION

PET using FDG and Met appear equally effective in detecting residual or recurrent malignant tumors although FDG uptakes were slightly higher than Met uptakes. Both showed a limited diagnostic sensitivity for small (< 1.5 cm) tumors.

Synthesis and evaluation of water-soluble polyethylene glycol-paclitaxel conjugate as a paclitaxel prodrug

Water-soluble paclitaxel may cause less side effects and be less costly to administer in comparison to a taxol formulation using a cremophor EL/alcohol vehicle. In this study, polyethylene glycol (PEG; MW 5000) was conjugated to the 2' position of paclitaxel through a spacer succinyl group. PEG-paclitaxel as a non-ionic paclitaxel prodrug was highly water soluble (> 20 mg equiv. paclitaxel/ml). The release of paclitaxel from phosphate-buffered solution was pH dependent. The half-life of PEG-paclitaxel was 7.6, 54 and 311 min at pH 9.0, 7.4 and 6.0, respectively. PEG-paclitaxel inhibited the growth of B16 melanoma cells to an extent similar to that of paclitaxel. In MCA-4 mammary tumor-bearing mice, a single dose of PEG-paclitaxel (40 mg equiv. paclitaxel/kg body weight) significantly delayed tumor growth. The average number of days for the tumor to reach 12 from 8 mm in diameter increased from 6.5 days for control animals to 8.5 days for PEG-paclitaxel-treated animals and 9.4 days for paclitaxel-treated animals. These studies demonstrated that PEG may be used as an effective solubilizing carrier for paclitaxel.

Positron emission tomography using [18F]fluorotamoxifen to evaluate therapeutic responses in patients with breast cancer: preliminary study

Positron emission tomography (PET) was used to assess the biodistribution and clinical usefulness of [18F]fluorotamoxifen (FTX) in 10 patients with estrogen-receptor(ER)-positive breast tumors. Ten patients with ER-positive breast cancer were prospectively studied, and the consecutive PET imagings (each takes 15 or 20 min) were obtained for 60 or 80 min after the injection of 88.8-392.2 MBq (2.4-10.6 mCi) of [18F]FTX. Twenty three suspected primary or metastatic lesions in 10 patients were evaluated and the tumor uptakes of [18F]FTX in nineteen tumor lesions were correlated to the response of tamoxifen therapy. Three lesions in three patients were considered to be truly negative for breast cancer on the bases of biopsy specimens and/or clinical course. Five (71.4%) of seven patients and 16 (80.0%) of 20 lesions were interpreted to be truly positive for breast cancer. The mean standardized uptake value (SUV) of the radiotracer in tumor was 3.0 on delayed images. There was no significant correlation between the standardized uptake values of [18F]FTX and the ER concentrations in primary lesions. Nineteen tumor lesions in six patients were evaluable to compare the [18F]FTX uptake with responses to tamoxifen therapy after the PET study. Three patients who had a good response to tamoxifen therapy showed positive lesions on PET images, whereas two of three patients who had a poor response showed negative lesions and one showed mixed results. There was no significant difference of [18F]FTX uptake in bone lesions between good and poor responders. However, when bone lesions were excluded, [18F]FTX uptakes in tumors with good responses were significantly higher than those with poor responses (mean and standard deviation of SUV: 2.46 +/- 0.62 vs 1.37 +/- 0.59, P < 0.05). PET imaging using [18F]FTX provides useful information in predicting the effect of tamoxifen therapy in patients with ER-positive breast cancer. Further study is warranted to confirm the clinical utility of PET using [18F]FTX in breast cancer patients.

99Tcm-IMMU4 imaging in recurrent colorectal cancer: efficacy and impact on surgical management

The aims of this study were to evaluate the efficacy of scintigraphy with the 99Tcm-labelled anti-carcinoembryonic antigen (CEA) monoclonal antibody Fab' fragment (IMMU4) in the diagnosis of recurrent colorectal carcinoma and to investigate its usefulness in the intraoperative surgical management of patients undergoing re-operation because of a rising serum CEA. We evaluated 24 patients prospectively who had rising serum CEA 6-19 months after initial surgery for colorectal carcinoma. Ten patients had lesions confirmed by computed tomography, ultrasound, magnetic resonance imaging, endoscopic examination or barium enema. Fourteen patients had negative findings on one or more of the above studies, but were suspected of having occult disease from their rising serum CEA. All patients were scheduled for surgery for restaging during a "second look' procedure. Planar and single photon emission tomography (SPET) imaging was performed in all patients. All scintigraphic findings were correlated with surgical and histopathological results. The overall sensitivity, specificity and accuracy were 81, 90 and 86% respectively when analysed by lesion, and 95, 60 and 88% respectively when analysed by patient. Ten of 14 (71%) patients with occult disease were correctly diagnosed as having recurrent disease. The SPET images were shown to have superior detectability (80%) compared with the planar images (35%). The surgeon judged the study to have had a neutral impact in 75% of the patients, but to have been helpful in 25%. We conclude that this antibody is potentially useful in detecting recurrent colorectal carcinoma in patients with rising serum CEA, especially when conventional imaging is negative or equivocal. It can also be helpful in altering planned surgery.

Evaluation of preoperative chemotherapy using PET with fluorine-18-fluorodeoxyglucose in breast cancer

We retrospectively investigated the value of PET with fluorine-18 fluorodeoxyglucose (FDG) for preoperative chemotherapy response in patients with locally advanced breast cancer.

METHODS

FDG-PET studies were performed on 16 consecutive patients. All patients had PET studies before chemotherapy, 13 patients between the end of the first cycle and at the midpoint of chemotherapy, and 14 patients before surgery. Visual diagnoses and the standardized uptake values (SUV) of PET scans were compared with pathology findings at surgery and with the results of mammography, ultrasonography (US) or both, which were performed before chemotherapy and before local surgery for residual disease. Each patient's clinical course was monitored for up to 3 yr.

RESULTS

Sensitivity for detection of pathologically proven primary lesions was 100%, 62.5% and 87.5% with FDG-PET, mammography and US, respectively; and sensitivity for detection of initial nodal involvement was 77%, 70% and 87.5%, respectively. Sensitivity for detection of residual primary tumor was 75%, 71.4% and 87.5%, respectively; and sensitivity for detection of residual nodal involvement was 41.6%, 71.4% and 66.6%, respectively. The mean SUV value of primary lesions was 9.4 (range 2.0-20.7, n = 16), with only two lesions showing an SUV below 3. Clinical improvement of primary lesions was seen in all patients; improvement with smaller size and less FDG uptake was visible as early as the second study in 11 patients (69%). Mean SUV values obtained at the second and third studies decreased significantly from those obtained in the first study. In four patients, the disease recurred after breast surgery with high SUV values. The mammograms and sonograms obtained before surgery showed a decrease in the diameter of 6 and 12 primary lesions of the 13 and 14 patients examined, respectively.

CONCLUSION

FDG-PET is valuable for monitoring the effects of preoperative chemotherapy in patients with locally advanced breast cancer with better sensitivity for primary tumor and better specificity for nodal metastasis in comparison with ultrasonography.

Phase II study of docetaxel in patients with epithelial ovarian carcinoma refractory to platinum

We analyzed the efficacy and toxicity of docetaxel in patients with ovarian cancer who failed previous chemotherapy with platinum. Fifty-five patients with measurable ovarian cancer were entered in this Phase II study at The University of Texas M. D. Anderson Cancer Center. Treatment consisted of 100 mg/m2 docetaxel given i.v. every 3 weeks. Because of hypersensitivity reactions, premedication with steroids and antihistamine was initiated during the study. Twenty-two (40%) patients responded (there were 3 complete responders and 19 partial responders). Twenty-one (38%) patients had stable disease. The median survival was 10 months. The main toxicity was neutropenia (98% of patients), with 13 episodes of neutropenic fever. Cumulative fluid retention was the main reason for dose modification and required a combination of diuretics and steroids for palliation. Other side effects were alopecia (100%); anemia (87%); dermatitis (67%); gastrointestinal disorders (53%); stomatitis (49%); neurotoxicity (45%); excessive lacrimation (33%); and hypersensitivity reactions (11%), which in one case were life threatening (loss of consciousness, fluid resuscitation). Docetaxel as a single agent proved to be active in heavily pretreated ovarian cancer patients but is associated with significant side effects. Objective toxicity consisted mainly of neutropenia and fluid retention. Neutropenia was dose limiting and required therapy with granulocyte colony-stimulating factor. Fluid retention was improved but not eliminated by diuretics and corticosteroids. Additional studies of docetaxel in ovarian carcinoma are indicated to define the activity in relation to paclitaxel and in platinum combination therapy.

Phase II study of intravenous topotecan as a 5-day infusion for refractory epithelial ovarian carcinoma

PURPOSE

To determine the efficacy and toxicity of topotecan administered as a 5-day intravenous infusion in patients with advanced ovarian cancer refractory to cisplatin-based chemotherapy.

PATIENTS AND METHODS

Thirty patients with advanced epithelial ovarian cancer refractory to cisplatin-based chemotherapy received intravenous infusions of topotecan 1.5 mg/m2 delivered over 30 minutes each day for 5 days. A course was repeated every 21 days. The patient eligibility requirements included age > or = 18 years, Zubrod score < or = 2, measurable disease, adequate hepatic and renal function, neutrophil count > or = 1,500/microL, platelet count > or = 100,000/microL, and anticipated survival > or = 3 months.

RESULTS

Twenty eight patients were assessable for response and toxicity. All patients were assessable for survival. The major toxicity from administration of topotecan at this dose schedule was myelosuppression; 21 patients required dose reductions. Four patients had neutropenic fever that required hospitalization, and seven patients required platelet transfusions. Maculopapular pruritic exanthema occurred in 20% of patients; gastrointestinal side effects were mild. No deaths were reported on the study. At dose levels of 1.5, 1.25, and 1.0 mg/m2, 61%, 31%, and 25% of patients, respectively, required dose reductions. Of 28 assessable patients, four (14%; 95% confidence interval [CI], 4% to 34%) achieved a partial response (PR) at a median of 1.4 months and lasting 8.9 months, and 17 had stable disease (SD). The overall median survival time was 10.0 months (95% CI, 8.1 to 13.5).

CONCLUSION

Topotecan shows modest clinical activity against cisplatin-refractory ovarian cancer, although the dose-intensity is compromised by the depth of the granulocyte nadir and the duration of granulocytopenia. Further studies of topotecan may necessitate a reevaluation of optimal dose schedule, with the possible incorporation of multilineage cytokines, and its activity in taxane-resistant tumors.

[Organization of the gene for the beta-subunit of human photoreceptor cyclic GMP phosphodiesterase]

Two recombinant bacteriophage lambda clones encoding a 27.8-kb fragment of the human phosphodiesterase beta-subunit gene were isolated from a human genomic library. The nucleotide sequences of 19 exons (from the 4th to 22nd), 18 introns, and the 3'-flanking region were determined. The analysis of the nucleotide sequence of the phosphodiesterase beta-subunit gene revealed four Alu repeats and four minisatellite regions.

Assessment of tumor cell proliferation using [18F]fluorodeoxyadenosine and[18F]fluoroethyluracil

This study was to develop radiofluorinated ethyluracil (FEU) and deoxyadenosine analogues (FAD) for noninvasive assessment of tumor proliferative potential by positron emission tomography (PET). 5-(2-Fluoroethyl)uracil ([18F]FEU) was prepared by treating 2,4-dimethoxy-5-(2-hydroxyethyl)pyrimidine with K18F, followed by hydrolysis with HBr. Fluorodeoxyadenosine ([18F]FAD) was prepared by treating a triacetylated analogue of adenosine with K18F. In vitro cell proliferation assay of [18F]-FEU was performed using human peripheral blood mononucleus cells. Tissue distributions were studied in breast tumor-bearing rats at 0.5, 1, 2 and 4 h along with autoradiography at 45 min postinjection. PET imaging studies were conducted in VX-2 tumor-bearing rabbits. In vitro assay indicated that [18F]FEU incorporated into DNA/RNA during cell proliferation. Tumor-to-tissue count density ratios of [18F]FAD and [18F]-FEU increased as a function of time. [18F]FAD had higher tumor-to-nontumor tissue count density ratios than [18F]FEU. Autoradiograms of [18F]FEU and [18F]FAD, and PET images of [18F]FEU, showed that the tumors could be well visualized. The results suggest that [18F]FEU and [18F]FAD have potential use in evaluating tumor cell proliferation by PET.

Calculation of solvation and binding free energy differences between VX-478 and its analogs by free energy perturbation and AMSOL methods

VX-478 belongs to a novel class of HIV-1 protease inhibitors that are based on N,N-disubstituted benzene sulfonamides. Force field parameters for the N,N-dialkyl benzene sulfonamide moiety have been assembled from the literature and from our own ab initio calculations. These parameters were employed to calculate solvation and binding free energy differences between VX-478 and two analogs. The free energy perturbation method has been used to determine these differences using two approaches. In the first approach, intergroup interaction terms only were included in the calculation of free energies (as in most reports of free energy calculations using AMBER). In the second approach, both the inter- and intragroup interaction terms were included. The results obtained with the two approaches are in excellent agreement with each other and are also in close agreement with the experimental results. The solvation free energies of N,N-dimethyl benzene sulfonamide derivatives (truncated models of the inhibitors), calculated using continuum solvation (AMSOL) methods, are found to be in qualitative agreement with the experimental and free energy perturbation results. The binding and solvation free energy results are discussed in the context of structure-based drug design to show how physicochemical properties (for example aqueous solubilities and bioavailabilities) of these HIV-I protease inhibitors were improved, while maintaining their inhibitory potency.