David E. Seitz

Single Molecule Dynamics of Lysozyme Processing Distinguishes Linear and Cross-linked Peptidoglycan Substrates

The dynamic processivity of individual T4 lysozyme molecules was monitored in the presence of either linear or cross-linked peptidoglycan substrates. Single-molecule monitoring was accomplished using a novel electronic technique in which lysozyme molecules were tethered to single-walled carbon nanotube field-effect transistors through pyrene linker molecules. The substrate-driven hinge-bending motions of lysozyme induced dynamic electronic signals in the underlying transistor, allowing long-term monitoring of the same molecule without the limitations of optical quenching or bleaching. For both substrates, lysozyme exhibited processive low turnover rates of 20-50 s(-1) and rapid (200-400 s(-1)) nonproductive motions. The latter nonproductive binding events occupied 43% of the enzymes time in the presence of the cross-linked peptidoglycan but only 7% with the linear substrate. Furthermore, lysozyme catalyzed the hydrolysis of glycosidic bonds to the end of the linear substrate but appeared to sidestep the peptide cross-links to zigzag through the wild-type substrate.

Phase II study of gemcitabine plus docetaxel in advanced pancreatic cancer: A hoosier oncology group study

Objective: To determine the response rate, duration of response and survival with weekly gemcitabine plus docetaxel in metastatic or unresectable pancreatic cancer. Methods: Forty patients were enrolled, and 38 patients were evaluable for survival and toxicity. Thirty-seven patients were evaluable for response. Nine patients (24%) had locally advanced disease and 29 (76%) had metastatic disease at the time of enrollment. Median Eastern Cooperative Oncology Group performance status was 1. Patients received gemcitabine 750 mg/m2 i.v. and docetaxel 35 mg/m2 i.v. weekly for 3 out of 4 weeks for a maximum of 6 cycles. Results: Patients received a median of 4 cycles (range 1–6) of chemotherapy. An objective response was obtained in 10 patients (27%) with a median duration of 17 weeks. Median survival was 7 months, and 1-year survival was 19.3%. Eight patients experienced at least one form of grade 4 toxicity and 27 patients experienced at least one type of grade 3 toxicity. Conclusions: The combination of gemcitabine and docetaxel is a well-tolerated regimen with clinical efficacy. The ultimate role of this combination versus single-agent gemcitabine can only be determined by a randomized phase III trial.

A phase II trial of irinotecan, 5-fluorouracil and leucovorin combined with celecoxib and glutamine as first-line therapy for advanced colorectal cancer.

Objectives: Preclinical and clinical data indicate that cyclooxygenase-2 (COX-2) is a bona fide molecular target for colorectal cancer (CRC). Glutamine may decrease chemotherapy-associated diarrhea. This study was designed to address whether the addition of celecoxib, a COX-2 inhibitor, and glutamine would improve the efficacy and decrease the toxicities of the irinotecan, fluorouracil and leucovorin (IFL) regimen. Methods: All patients received the original IFL regimen plus celecoxib (400 mg, po, every 12 h continuously while on trial) and glutamine (10 g, po, every 8 h continuously while on chemotherapy). Results: Of the 41 patients enrolled, 40 patients received between 1 and 6 cycles of treatment. This regimen was associated with significant toxicities: 45.0% had grade 3 diarrhea, 35.0% grade 3/4 neutropenia, 22.5% hospitalization, 10.0% deep vein thrombosis and 2 treatment-related deaths. The overall response rate was 47.2%. The median progression-free survival was 6.7 months. The median overall survival was 16.3 months. The 12-month overall survival rate was 54.8%. COX-2 expression was present in 63.2% of the specimens evaluated. There was no significant correlation between COX-2 expression and response to chemotherapy (p = 0.739). Conclusion: The addition of celecoxib and glutamine appears not to improve the efficacy or decrease the toxicities of IFL for the treatment of metastatic CRC.

Fluorotamoxifen. A Caveat on the Generality of Electrophilic Destannylation

Abstract A one-step synthesis of fluorotamoxifen from tamnoxifen is described. Attempts to achieve synthesis of the title compound by fluorodestannylation or transmetallation were unsuccessful.

Phase I trial of carboplatin and paclitaxel with escalating doses of oral topotecan in patients with solid tumors.

&NA; Carboplatin, paclitaxel, and topotecan have activity against a variety of cancers. This phase I study was designed to determine the maximum tolerated dose of oral topotecan when given in combination with carboplatin and paclitaxel. Eligibility criteria were as follows: Karnofsky Performance score greater than or equal to 80; and adequate hepatic, renal, and bone marrow function. Patients received paclitaxel 175 mg/m2 intravenously followed by carboplatin AUC5 iv on day 1 every 3 weeks for up to 6 cycles. Cohorts of 3 to 5 were treated with escalating doses of oral topotecan on days 1 to 5, initially at 0.75 mg/m2 then 1 mg/m2 and 1.25 mg/m2 in subsequent cohorts. Thirteen patients were treated. Three of three patients in cohort 1 had grade IV neutropenia, with one neutropenic fever and one patient requiring a platelet transfusion. In cohort 2, three of five patients had grade III/IV neutropenia including two with neutropenic fever. Four patients required blood transfusions and one required platelet transfusions. In cohort 3, three of five had grade III/IV neutropenia, one of five had grade IV thrombocytopenia, and one patient required blood transfusions. In conclusion, this three‐drug regimen resulted in significant cumulative myelosuppression in the doses and schedule tested in this phase I trial. Subsequent combinations of these drugs should focus on alternate doses or schedules.