In vitro evaluation of flavopiridol, a novel cell cycle inhibitor, in bladder cancer

Purpose: To determine the in vitro effects of flavopiridol on bladder cancer cell lines, immortalized urothelial cell lines, and normal urothelial cells well characterized for defects in p53, pRb, and p16. Methods: Growth inhibition was assessed via an MTT assay and apoptosis via DAPI nuclear staining. Cell cycle analysis was performed via propidium iodide staining and fluorescent activated cell sorting (FACS). Multidrug-resistant cells were generated by continuous exposure to doxorubicin. Results: Growth inhibition was not correlated with inactivation of p53, pRb, or p16. All cells experienced G2/M arrest within 24 h of flavopiridol exposure. Modest apoptosis was observed but required 72 h of continuous drug exposure to become evident. There was no obvious synergistic or antagonistic toxicity when flavopiridol was combined with radiotherapy or cisplatin dosed at the IC₅₀ despite the observation that radiotherapy and flavopiridol led to more profound G2/M arrest than either agent alone. Doxorubicin-resistant cells, demonstrated to overexpress the MDR1 multidrug-resistance protein were equally as sensitive to flavopiridol as the parental cells. Conclusions: Flavopiridol is a novel cell cycle inhibitor that may be a useful agent in bladder cancers with tumor suppressor gene alterations and/or multidrug resistance. Received: 7 July 1998 / Accepted: 28 October 1998     

Serum leptin concentrations of patients with sequential thyroid function changes

BACKGROUND: Leptin, a recently discovered protein produced in adipocytes, regulates body weight by suppressing food intake and/or increasing energy expenditure. Thyroid hormones, which increase the basal metabolic rate and thermogenesis, have been reported to be one of leptin's regulating factors because alternations in thyroid status might lead to compensatory changes in circulating leptin. OBJECTIVE: The aim of this study was to assess the influence of sequential changes in thyroid function on serum leptin levels. PATIENTS AND METHODS: The thyroid function status of 65 patients (55 women and 10 men, aged 40.6 +/- 15.2 years, mean +/- SD) with differentiated thyroid cancer who had received near-total thyroidectomy was studied before I-131 ablation therapy and after 2-4 and 6 months of levo-thyroxine suppressive therapy. Thirty-three (26 women, seven men; aged 41.0 +/- 10.4 years, mean +/- SD) of them were found to have become hypothyroid, then euthyroid and subsequently subclinically hyperthyroid. Their body mass index (BMI), body fat (%BF) by electrical bioimpedance, thyroid function and fasting serum leptin in these states were assessed and compared to those of 38 controls (30 women, eight men, aged 40.2 +/- 11.3 years, mean +/- SD). The controls had no past history or family history of thyroid diseases, and had the same range of BMI, between 20 and 30 kg/m2, as the patients. RESULTS: No difference in serum leptin levels was found between patients and controls with comparable age, sex, and BMI distribution in the euthyroid state. Using a repeated measures anova, tests of TSH, free T4 (FT4), BMI,%BF and leptin were performed on the 33 patients with sex as a grouping factor and thyroid state as a time factor. The sex difference for %BF and leptin proved to be statistically significant (P < 0.0001, and P = 0.0003, respectively). Serum leptin levels increased significantly from the hypothyroid to the subclinical hyperthyroid state (P < 0.0001) with a more pronounced increase found in females than in males (P = 0.03). Change of BMI during sequential thyroid function alterations was significant (P = 0.04) while change in %BF was not significant (P = 0.09). Pearson correlation analysis showed that serum leptin levels significantly correlated with BMI, %BF, FT4, and TSH (all P < 0.05). Using the generalized estimating equations, multivariate regression analysis revealed that FT4 was a statistically independent predictor for serum leptin (P < 0.0001). While other parameters were held constant, the mean serum leptin level increased by 1.47 units when serum FT4 was increased by one unit. CONCLUSION: In conclusion, our data indicate that circulating thyroid hormone plays a relevant role in regulating leptin metabolism independent of BMI and body fat.     

Differential interleukin-1 elaboration by density-defined human monocyte subpopulations

Interleukin-1 (IL-1) is an important immunoregulatory peptide produced by monocytes and macrophages. Because mononuclear phagocytes are morphologically and functionally heterogeneous, we examined whether they differ in their ability to elaborate IL-1. We used discontinuous Percoll gradients to obtain five density-defined human blood monocyte subpopulations. Unfractionated monocytes and their subsets were compared for their ability to stimulate thymocyte proliferation. Supernatants obtained from the denser monocytes consistently contained more IL-1 activity than did supernatants from the less dense cells. This difference in IL-1 activity was the result of differences in IL-1 elaboration, not the selective production of an inhibitor of IL-1- induced thymocyte proliferation. These data demonstrate that density- defined human monocyte subpopulations differ in their capacity to elaborate IL-1.     

Elimination profile of triamcinolone in urine following oral administration

Triamcinolone (T) is a glucocorticoid commonly used to relieve inflammation and treat arthritis, severe allergies, and asthma; however, it is banned by the World Anti‐Doping Agency in competition for athletes when administered orally, intravenously, intramuscularly, or rectally. The minimum required performance limit (MRPL) for urinary T is 30 ng/mL. However, the data about the urinary excretion of T after oral administration is limited. We investigate the elimination profile and determine whether single‐dose administration of T would cause a positive doping result. Twelve healthy volunteers received a single‐dose of 4‐mg T rally, and urine samples were collected for 24 hours. A validated liquid chromatography–tandem mass spectrometry method was used to determine urinary T levels. Non‐compartmental modeling was used to estimate the pharmacokinetic parameters. All the urinary T concentrations were much higher than the MRPL. The peak urinary T concentration was 3211.4 ± 860.3 ng/mL (mean ± SD), time to peak concentration was 1.7 ± 0.9 hours, and the estimated elimination half‐life was 4.4 ± 2.8 hours. About 27.76% of the consumed dose was eliminated via urine within 24 hours of intake. After a single‐dose oral administration, urinary T concentrations still exceeded the MRPL after 24 hours. This information could be useful for limiting the misuse of T. Athletes should be aware when using T in competition and acquire approval for a therapeutic use exemption prior to use. Moreover, the elimination profile of orally administered T may be crucial information for distinguishing different dosage routes.