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Biomedical subjects

John D Roberts

Publications and source records attributed to John D Roberts.

31 records · Page 2Linked to original sources
PubMed2003

Requirement of protein kinase C micro activation and calpain-mediated proteolysis for arachidonic acid-stimulated adhesion of MDA-MB-435 human mammary carcinoma cells to collagen type IV.

Arachidonic acid (AA) stimulation of adhesion of human metastatic breast carcinoma cells to collagen type IV depends on the protein kinase C (PKC) pathway(s) and is associated with the translocation of PKC mu from the cytoplasm to the membrane. In the present study, we have further explored the role of PKC mu in AA-stimulated adhesion. PKC mu activation site serines 738/742 and autophosphorylation site serine 910 are rapidly phosphorylated, and in vitro PKC mu kinase activity is enhanced in response to AA treatment. Inhibition of PKC mu activation blocks AA-stimulated adhesion. A phosphorylated, truncated species of PKC mu was detected in AA-treated cells. This 77-kDa protein contains the kinase domain but lacks a significant portion of the regulatory domains. Inhibition of calpain protease activity blocks generation of the truncated protein, promotes accumulation of the activated, full-length protein in the membrane, and blocks the AA-mediated increase in adhesion. p38 MAPK activity is also required for AA-stimulated adhesion. Activation of PKC mu and p38 are independent events. However, inhibition of p38 activity reduces calpain-mediated proteolysis of PKC mu and in vivo calpain activity, suggesting a role for p38 in regulation of calpain activity and a point for cross-talk between the PKC and MAPK pathways. These results support the hypothesis that AA stimulates activation of PKC mu, which is cleaved by calpain at the cell membrane. The resulting truncated kinase, as well as the full-length kinase, may be required for increased cell adhesion to collagen type IV. Additionally, these studies present the first evidence for calpain cleavage of a non-structural protein leading to the promotion of tumor cell adhesion.

Arachidonic Acid↗
PubMed2003

RTOG 97-06: initial report of a phase I-II trial of selective bladder conservation using TURBT, twice-daily accelerated irradiation sensitized with cisplatin, and adjuvant MCV combination chemotherapy.

To examine combination cisplatin and twice-daily accelerated irradiation (RT) after aggressive transurethral resection of bladder tumor (TURBT) in an attempt to preserve the bladder and to determine the likelihood that patients who complete this regimen could then complete three cycles of methotrexate, cisplatin, vinblastine (MCV) chemotherapy. Between 1998 and 2000, 52 patients with Stage T2-T4aN0M0 disease, from 17 institutions, were entered into the trial. Forty-seven patients were deemed eligible; the planned accrual was 40. Of the 46 patients, 68% were >60 years old, 70% were men, and 96% had a Karnofsky score >/=90. The clinical T stage was T2 in 66%, T3a in 25%, and T3b in 9%. The median follow-up at the time of analysis was 26 months. The protocol required TURBT within 6 weeks of the initiation of induction therapy. Induction treatment involved 13 days of concomitant boost RT, 1.8 Gy to the pelvis in the morning followed by 1.6 Gy to the tumor 4-6 h later. For sensitization, cisplatin (20 mg/m(2)) was given on the first 3 days of each treatment week. Three to four weeks after induction, patients were evaluated cystoscopically for residual disease. Patients whose biopsies and cytologic evaluations showed no disease completed consolidation chemoirradiation. Patients with residual tumor went on to cystectomy. After either consolidation or cystectomy, patients were to complete three cycles of MCV chemotherapy. Of the 47 patients, 45% completed all phases of the protocol treatment with minor, or no, deviations. Five patients refused either the postinduction evaluation or cystectomy and 6 refused adjuvant chemotherapy. The CR rate after induction therapy was 74%. For 2 patients, residual disease after induction was limited to positive cytologic findings, and for 8 patients, biopsy of the primary site revealed persistence. Of the 8 cystectomy patients, 2 had no evidence of disease in the bladder at pathologic review of the surgery specimen. Grade 3 toxicity related to chemotherapy was observed in 11% of patients during both induction and consolidation, and in 41% during adjuvant chemotherapy. A total of 8 patients (36% of those receiving adjuvant chemotherapy) went on to develop Grade 4 neutropenia or thrombocytopenia during additional adjuvant chemotherapy. Grade 3 toxicity due to RT was seen in 4% and 0% of patients during induction and consolidation, respectively. One patient developed Grade 4 hydronephrosis during consolidation. The projected 36-month value for locoregional failure, distant metastasis, overall survival, and bladder-intact survival was 27%, 29%, 61%, and 48%, respectively. After aggressive TURBT, twice-daily accelerated RT initiated in concomitant-boost format is well tolerated and results in a rate of complete response (74%) similar to that in previous bladder-sparing trials. The projected 2-year values for locoregional control, bladder-intact survival, and overall survival were also consistent with previously reported trials of bladder-sparing treatment. With only 45% of patients completing three cycles of MCV, this form of adjuvant chemotherapy appears to be poorly tolerated by most patients.

Algorithms↗
PubMed2003

Conformations of 2-carboxy-1,4-butanedioic acid as a function of ionization state in dimethyl sulfoxide.

[reaction: see text] The conformational equilibria of 2-carboxy-1,4-butanedioic acid and its mono-, di-, and trianions were estimated by NMR couplings in dimethyl sulfoxide (DMSO). Intramolecular hydrogen bonding was inferred for the mono- and dianions, but not for the triacid. For the di- and trianions, the (3)J(HH) couplings were consistent with the negative carboxylate groups being much closer together than might be expected from electrostatic repulsion considerations. The successive triacid pK(a) values were estimated as 7.0, 13.4, and approximately 20(?) on the Bordwell scale.

Journal Article↗
PubMed2003

The use of cyclin-dependent kinase inhibitors alone or in combination with established cytotoxic drugs in cancer chemotherapy.

Cyclin-dependent kinase (CDK) inhibitors are small molecule inhibitors of the kinases required for the orderly progression of cells, both normal and neoplastic, through the cell cycle. Because cell cycle dysregulation is such a common occurrence in neoplasia, the search for agents that might block cell cycle traverse has been the focus of intense interest. These efforts have led to the identification of a broad array of compounds that interfere directly with the function of CDKs. Two of these agents (flavopiridol and UCN-01) have now entered the clinical arena, and others are scheduled to do so in the near future. In preclinical studies, CDK inhibitors have shown the ability not only to block neoplastic cell proliferation, but also to induce, through a variety of mechanisms, programmed cell death. The latter capacity may stem from the diverse effects that CDK inhibitors exert on multiple kinases and apoptotic regulatory molecules. In addition, there is abundant preclinical evidence that CDK inhibitors can potentiate, generally in a dose- and sequence-dependent manner, the anti-tumor effects of many established cytotoxic agents. In clinical studies in humans, flavopiridol and UCN-01 have been shown to be tolerable, although clear evidence of single agent activity or enhancement of the efficacy of established agents has not yet emerged. This may reflect a failure to optimize drug schedules/pharmacokinetics, or to identify the critical molecular targets of these agents. Finally, in recent years, a rationale has emerged for combining CDK inhibitors with other molecularly targeted agents (i.e. differentiation-inducers and signal transduction modulators). Current research has basically two goals: (a). to identify CDK inhibitor concentrations and schedules that inhibit the growth of and induce apoptosis in specific tumor cell types; and (b). to establish a rational basis for combining CDK inhibitors with more conventional cytotoxic agents to enhance antitumor efficacy. This review gives a brief summary of such efforts, with an emphasis on agents and combinations that are in or near clinical development.

Animals↗
PubMed2003

Phase I studies of weekly administration of cytotoxic agents: implications of a mathematical model.

Certain toxic effects of cytotoxic anticancer agents typically evolve over weeks. When such agents are administered weekly, these effects are cumulative. With such schedules, good medical practice mandates dose modifications with mild or moderate toxicity in order to avoid progression to serious or life-threatening toxicity. These modifications lead to differences between scheduled and delivered doses. Phase I studies are designed to identify the maximum tolerated dose for a given schedule. Yet neither standard phase I study designs nor the theoretical literature acknowledge the existence or incorporate the impact of dose modifications upon phase I study outcomes. Our purpose was to better understand the impact of dose reductions/omissions upon outcomes of phase I studies of weekly administration of cytotoxic agents. We created a mathematical model in which toxicity was represented as a power function of dose in order to represent extremes of behavior observed with actual cytotoxic agents in the clinic. We used the model to simulate dosing and toxicity experiences across a wide range of doses. From these simulations we identified "best doses" according to a variety of traditional and novel criteria. We find the concept of maximum tolerated dose inadequate for the determination of best doses. We also suggest a strategy for a new phase I study design which can be used to estimate the "best dose" corresponding to a specified delivery rate. In summary, identification of best doses requires attention, not only to dose limiting toxic events, but also to delivered dose rates and schedule adherence.

Antineoplastic Agents↗
PubMed2003

Effect of tamoxifen on venous thrombosis risk factors in women without cancer: the Breast Cancer Prevention Trial.

Tamoxifen reduces breast cancer incidence among healthy women, but is associated with an increased risk of venous thrombosis. We studied the 6 month effects of tamoxifen on venous thrombosis risk factors in women without cancer. One hundred and eleven women at one centre who were participants in a multicentre breast cancer prevention trial were randomized, in double-blind fashion, to receive 20 mg/d of tamoxifen or placebo. The activated protein C (APC) ratio and concentrations of antithrombin, protein C antigen, and total protein S were measured at baseline and 6 months of treatment. None of the factors changed over 6 months in placebo-treated women. Among tamoxifen-treated women, antithrombin and protein S, but not protein C or APC ratio were reduced. Sequential antithrombin concentrations with tamoxifen were 114% and 104% (P = 0.001 compared with placebo). Sequential protein S concentrations with tamoxifen were 18.42 and 17.30 micro g/ml (P = 0.02 compared with placebo). Reductions in antithrombin and protein S were greater in postmenopausal women, but did not differ by other risk factors for venous thrombosis, such as body mass index. Reductions of antithrombin and protein S, but not protein C or APC resistance, might relate to the increased risk of venous thrombosis associated with tamoxifen treatment.

Activated Protein C Resistance↗
PubMed2002

Quantum-mechanical calculations of the stabilities of fluxional isomers of C4H(7)(+) in solution.

Although numerous quantum calculations have been made over the years of the stabilities of the fluxional isomers of C(4)H(7)(+), none have been reported for other than the gas phase (which is unrealistic for these ionic species) that exhibit exceptional fluxional properties in solution. To be sure, quantum-mechanical calculations for solutions are subject to substantial uncertainties, but nonetheless it is important to see whether the trends seen for the gas-phase C(4)H(7)(+) species are also found in calculations for polar solutions. Of the C(4)H(7)(+) species, commonly designated bisected-cyclopropylcarbinyl 1, unsym-bicyclobutonium 2, sym-bicyclobutonium 3, allylcarbinyl 4, and pyramidal structure 6, the most advanced gas-phase calculations available thus far suggest that the order of stability is 1 > or = 2 > or = 3 4 6 with barriers of only approximately 1 kcalmol for interconversions among 1, 2, and 3. We report here that, when account is taken of solvation, 2 turns out to be slightly more stable than 1 or 3 in polar solvents. The pattern of the overall results is unexpected, in that despite substantial differences in structures and charge distributions between the primary players in the C(4)H(7)(+) equilibria and the large differences in solvation energies calculated for the solvents considered, the differential solvent effects from species to species are rather small.

Journal Article↗
PubMed2002

An NMR and quantum mechanical investigation of solvent effects on conformational equilibria of butanedinitrile.

Vicinal proton-proton NMR couplings and ab initio quantum mechanics have been used to investigate solvent effects on conformational equilibria of butanedinitrile. The trans and gauche conformations are about equally favored at room temperature in solvents of low dielectric constant while the equilibrium is essentially the statistical proportions of one-third trans and two-thirds gauche in water with a high dielectric constant. The coupling assignments were confirmed with the aid of stereospecific deuterium-labeled (R,R or S,S)-1,2-dideuteriobutanedinitrile. The calculations support the observed trends. Similar results were observed for 1,2-dibromo- and dichloroethanes.

Journal Article↗
PubMed2002

An NMR and quantum-mechanical investigation of tetrahydrofuran solvent effects on the conformational equilibria of 1,4-butanedioic acid and its salts.

Vicinal proton-proton NMR couplings have been used to compare the influences of water and tetrahydrofuran (THF) as solvents on the conformational equilibria of 1,4-butanedioic (succinic) acid and its mono- and dianionic salts. An earlier NMR investigation (Lit, E. S.; Mallon, F. K.; Tsai, H. Y.; Roberts, J. D. J. Am Chem. Soc. 1993, 115, 9563-9567) showed that, in water, the conformational preferences for the gauche conformations for butanedioic acid and its monoanion and dianion were, respectively, approximately 84%, 66%, and 43%, essentially independent of the nature of the cation or concentration. We now report the corresponding gauche percentages calculated in the same way for 0.05 M solutions in THF to be 66%, 90-100%, and 46-64%. Substantial evidence was adduced for the rotational angle between the substituents in the monoanion being approximately 70 degrees. The positions of conformational equilibria of the salts in THF, particularly of the dianion, were found to be rather insensitive to concentration and temperature, but more sensitive to the amount of water present. Ab initio quantum-mechanical calculations for 1,4-butanedioate dianion indicate that, as expected for the gas phase, the trans conformation of the dianion should be heavily favored over the gauche, but, in both THF and water, the gauche conformation is calculated to predominate with rotational angles substantially less than 60 degrees. This conclusion is, in fact, generally consistent with the experimental vicinal proton couplings, which are wholly inconsistent with the trans conformation.

Journal Article↗
PubMed2002

Higher doses of mitoxantrone among men with hormone-refractory prostate carcinoma: a Cancer and Leukemia Group B study.

BACKGROUND: Mitoxantrone in combination with a low-dose glucocorticoid has been shown to produce more favorable outcomes among men with hormone-refractory prostate carcinoma than glucocorticoid alone. Therefore, the authors sought to determine the safety and activity of higher doses of mitoxantrone in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF) and a glucocorticoid in preparation for a possible Phase III trial comparing standard to dose-escalated mitoxantrone. METHODS: This Phase II trial enrolled 45 patients from October 1996 to March 1998. Twenty-one patients without pelvic irradiation (Arm I) received 21 mg/m(2) of mitoxantrone every 3 weeks, and 24 patients who had received pelvic irradiation (Arm II) were given 17 mg/m(2) on the same schedule. All patients received 40 mg of hydrocortisone in divided doses daily and GM-CSF at 500 microg/daily for a minimum of 10 days per cycle beginning on the third day of the cycle. RESULTS: In Arm I, 33% of assessable patients achieved a partial response, 50% had a > or = 50% decline in their PSA, and 35% had a > or = 75% decline in PSA values. The comparable numbers in Arm II were 24%, 48%, and 35%, respectively. The median survival times were 12 months in Arm I and 14 months in Arm II. Treatment had to be discontinued in 13% of patients because of thrombocytopenia. No other significant toxicities were encountered. CONCLUSIONS: Higher doses of mitoxantrone (17 and 21 mg/m(2)) were associated with activity comparable to many estramustine combinations and generally were well tolerated. However, because the degree and frequency of thrombocytopenia were greater than that observed with standard dose mitoxantrone (12-14 mg/m(2)), and because the median survival is apparently comparable to standard dose mitoxantrone, this approach to HRPC cannot be recommended for Phase III testing.

Aged↗
PubMedDate not supplied

An NMR investigation of the conformational equilibria of 2-(2'-pyridyl)ethylphosphonic acid in several solvents.

Vicinal proton-proton NMR couplings have been used to investigate whether the position of conformational equilibria is determined by intramolecular N-H hydrogen bonding for 2-(2'-pyridyl)ethylphosphonic acid 1 in its various possible ionization states in water, methanol, ethanol, and dimethyl sulfoxide (DMSO). With 1 in the form of its monoanion and dianion, the trans is favored, with the dianion being more trans than the monoanion for a given solvent, probably as the result of steric effects, possibly enhanced by repulsive electrostatic effects between the negatively charged phosphonic group and the lone pair on the pyridine nitrogen. For 1 and its conjugate acid, the gauche amounts, respectively, to 43% and 45% in water, 66% and 51% in methanol, 66% and 64% in ethanol, and 29% and 49% in DMSO. For these latter two species, electrostatic, steric, and hydrogen bonding-effects are all likely to play a role in determining the conformational equilibria.

Journal Article↗
PubMedDate not supplied

Phase 2 study of the g209-2M melanoma peptide vaccine and low-dose interleukin-2 in advanced melanoma: Cancer and Leukemia Group B 509901.

High-dose interleukin-2 (IL-2) is the only approved immunologic therapy for advanced melanoma, but response rates are low and significant toxicities limit treatment to otherwise healthy patients. g209-2M is a nanopeptide engineered to mimic an epitope of the gp100 melanocyte differentiation protein that is recognized in a human leukocyte antigen (HLA)-restricted manner by melanoma tumor-infiltrating lymphocytes in some patients. Previous reports indicated that administration of the g209-2M peptide could induce g209-reactive circulating T cells in patients with melanoma and that the combination of g209-2M and high-dose IL-2 might be a more active treatment than high-dose IL-2 alone. Low-dose IL-2 is not active but has significant biologic effects, and because of a different toxicity profile, it can be offered to most patients. The primary objective of this cooperative group phase 2 study was to determine the activity of the combination of g209-2M and low-dose IL-2 in advanced melanoma. Twenty-six HLA appropriate patients with advanced melanoma received subcutaneous g209-2M peptide once every 3 weeks and subcutaneous IL-2 (5 million IU/m) daily for 5 days during the first and second weeks. Patients were monitored for tumor response, toxicity, and induction of g209-reactive circulating T cells. There were no objective responses. There were no toxic deaths and no grade 4 toxicities. More than half of the patients experienced some grade 2 toxicity and one quarter experienced grade 3 toxicity. There was no convincing evidence by enzyme-linked immunospot or tetramer analysis of induction of g209-reactive circulating T cells. The combination of g209-2M and low-dose IL-2 is safe and tolerable but inactive against advanced melanoma. Absence of evidence of immunization raises concerns for peptide-based immunization strategies with concurrent IL-2.

Adult↗