Soft docking and multiple receptor conformations in virtual screening

Protein conformational change is an important consideration in ligand-docking screens, but it is difficult to predict. A simple way to account for protein flexibility is to soften the criterion for steric fit between ligand and receptor. A more comprehensive but more expensive method would be to sample multiple receptor conformations explicitly. Here, these two approaches are compared. A "soft" scoring function was created by attenuating the repulsive term in the Lennard-Jones potential, allowing for a closer approach between ligand and protein. The standard, "hard" Lennard-Jones potential was used for docking to multiple receptor conformations. The Available Chemicals Directory (ACD) was screened against two cavity sites in the T4 lysozyme. These sites undergo small but significant conformational changes on ligand binding, making them good systems for soft docking. The ACD was also screened against the drug target aldose reductase, which can undergo large conformational changes on ligand binding. We evaluated the ability of the scoring functions to identify known ligands from among the over 200 000 decoy molecules in the database. The soft potential was always better at identifying known ligands than the hard scoring function when only a single receptor conformation was used. Conversely, the soft function was worse at identifying known leads than the hard function when multiple receptor conformations were used. This was true even for the cavity sites and was especially true for aldose reductase. To test the multiple-conformation method predictively, we screened the ACD for molecules that preferentially docked to the expanded conformation of aldose reductase, known to bind larger ligands. Six novel molecules that ranked among the top 0.66% of hits from the multiple-conformation calculation, but ranked relatively poorly in the soft docking calculation, were tested experimentally for enzyme inhibition. Four of these six inhibited the enzyme, the best with an IC(50) of 8 microM. Although ligands can get better scores in soft docking, the same is also true for decoys. The improved ranking of such decoys can come at the expense of true ligands.     

Enlarged axillary nodes and position of the arms in axillary irradiation--a computed tomography and magnetic resonance imaging evaluation

The purpose of this study was to evaluate the axillary node displacement away from chest wall and their anatomical location in relation to the humeral head, according to the position of the arms, when the axilla is the site of enlarged nodes. In 13 patients with enlarged axillary nodes, the anatomical span of the nodes according to two arms positions, akimbo (A) and up over the head (U), was prospectively evaluated using computed tomography (CT) and magnetic resonance imaging (MRI). The nodes were classified into two groups, i.e. the lower and upper groups. The mean distances of the lower node group from the chest wall when the patients were in A, and U positions were 3 cm and 6.4 cm, respectively (p=0.002). The upper group nodes showed a smaller difference in the distance from the chest wall: in A position, mean 2.1 cm; in U position 2.8 cm (p=0.03). In U position, there was always a node of the lower group that was displaced in front of the humeral head. This study demonstrates the displacement of enlarged axillary nodes according to the position of the arms. In patients with axillary node involvement, CT planning should be considered when they have their arms held up over their heads.     

The role of selective estrogen receptor modulators in the prevention of breast cancer: comparison of the clinical trials

The role of estrogen in the development of breast cancer is well recognized, and the use of selective estrogen receptor modulators (SERMs) to reduce breast cancer risk continues to be evaluated. Tamoxifen is the only SERM approved for the reduction of breast cancer incidence in women at high risk. This approval was based on results from the Breast Cancer Prevention Trial. Although initial results from the Royal Marsden Hospital tamoxifen trial and Italian Tamoxifen Prevention Study did not show a similar overall effect of tamoxifen, recent updates from these two trials and initial results from the International Breast Cancer Intervention Study are consistent with a risk reduction effect of tamoxifen for estrogen-receptor-positive breast cancer. Raloxifene, approved for the prevention and treatment of postmenopausal osteoporosis, is another SERM being evaluated for breast cancer risk reduction. The recently completed Continuing Outcomes Relevant to Evista trial and the Raloxifene Use for The Heart trial, have breast cancer risk reduction as a primary end point. A third, ongoing trial, the Study of Tamoxifen and Raloxifene trial, is evaluating the relative efficacy and adverse event profile of these two agents in a population at high risk. The study populations of these raloxifene breast cancer prevention trials and the four tamoxifen prevention trials are quite diverse in terms of breast cancer risk. Completion of these trials will provide important information about the occurrence of invasive breast cancer in postmenopausal women and the efficacy of raloxifene for breast cancer risk reduction.     

Influence of maternal preeclampsia on recombinant human granulocyte colony-stimulating factor effect in neutropenic neonates with suspected sepsis

AIM: To evaluate the effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in preterm neonates with suspected sepsis and severe neutropenia (<1500 mm(3)), and to define the influence of maternal preeclampsia on rhG-CSF activity. METHODS: Twenty neonates of normotensive mothers (NNMs) (GA 29.2+/-0.5 weeks and BW 1.024+/-81 g) and 20 born to preeclamptic mothers (NPMs) (GA 29+/-0.4 weeks and BW 946+/-55 g) were treated with rhG-CSF, 10 microg/kg per day for 3 days. Complete blood counts were obtained at day 0 (before rhG-CSF administration) and 1-4, 6, 9, 20 and 30 days later. RESULTS: Absolute neutrophil count (ANC) increased rapidly (three-fold within 24h), and significantly (maximum approximately 20-25 times starting values) and remained within normal range in both groups. However, in NNMs a two-phase increase occurred with an early peak on day 2 and a further peak on day 6 giving significantly higher ANC (P<0.001) than for NPMs at days 2-4 and 6. NPMs showed a gradual ANC increase with a single late peak occurring 3 days later than NNMs (day 9). The highest peak values for ANC were similar (15,900+/-1395 mm(-3) for NNMs and 13,880+/-1097 mm(-3) for NPMs). Neutropenia was completely resolved within 2 days in NNMs and within 4 days in NPMs. CONCLUSION: Preeclampsia seemed to influence the course of the ANC in spite of rhG-CSF administration, and a higher daily-dose for NPMs with neutropenic sepsis may more rapidly resolve neutropenia by overcoming the preeclampsia-associated inhibitor of rhG-CSF through a dose-dependent mechanism.     

The role of intratumoral therapy with cisplatin/epinephrine injectable gel in the management of advanced squamous cell carcinoma of the head and neck

OBJECTIVE: To determine the safety and efficacy of targeted antitumor therapy with cisplatin/epinephrine injectable gel in patients with advanced squamous cell carcinoma of the head and neck. DESIGN: Two prospective, double-blind, placebo-controlled phase III trials of identical design. Crossover from blinded to open-label phase was permitted for patients with disease progression. SETTING: Tertiary referral centers in North America and Europe. PATIENTS: One hundred seventy-nine intensively pretreated patients with recurrent or refractory squamous cell carcinoma of the head and neck. INTERVENTION: Cisplatin/epinephrine injectable or placebo gel was administered by direct intratumoral injection; up to 6 weekly treatments. Dose was 0.25 mL of active or placebo gel per cubic centimeter of tumor up to 10 mL total. Patient benefit after local tumor control of the most symptomatic tumor was assessed by patients and physicians using the Treatment Goals Questionnaire. MAIN OUTCOME MEASURES: Local tumor response and patient benefit attributable to improvements in tumor-related symptoms. RESULTS: Combined results for the 178 patients with evaluable data in the 2 trials confirmed objective tumor responses in 35 (29%) of 119 patients, including 23 (19%) complete responses achieved with cisplatin/epinephrine gel, vs 1 (2%) of 59 for placebo (P<.001). Tumor response and patient benefit were significantly correlated (P=.006): 47% (17/36) of patients with target tumor responses achieved a rigorously defined benefit based on a prospectively selected treatment goal vs 15% (22/142) of nonresponders. CONCLUSION: Cisplatin/epinephrine injectable gel reduces tumor burden, ameliorates tumor symptoms, and provides a new therapeutic option for treating patients with squamous cell carcinoma of the head and neck.     

Twenty-one day administration of dienogest reversibly suppresses gonadotropins and testosterone in normal men

Androgen-progestin combinations are promising male contraceptive regimens. Optimization of these regimens includes the development of new progestins with more favorable biological properties. In this context we tested the effects of the progestin dienogest (DNG) on reproductive hormones and metabolic parameters in men. After a 3-wk control period, 25 men were randomly assigned to receive daily doses of 2, 5, or 10 mg DNG or placebo and 10 mg cyproterone acetate for 21 d (n = 5 subjects/group). Subjects were followed for 2 wk after cessation of hormone administration. Weekly blood samples, physical examinations, hormone and chemistry measurements, semen analysis, and sexual/behavioral assessments were performed. These parameters were compared among study groups and within each group at different time points throughout the study periods. DNG and cyproterone acetate administration resulted in profound suppression of gonadotropins and T with no change in SHBG levels. No adverse effects were detected in any subject. Hormone levels returned to baseline after stopping hormone intake. DNG is a potent suppressor of gonadotropins and T in men and does not induce adverse effects over a 21-d administration. DNG is a promising progestin to be used in clinical trials for male contraception.