Flavopiridol is the first potent inhibitor of cyclin-dependent kinases (CDKs) to enter clinical trials. Little is known about mechanisms of resistance to this agent. In order to determine whether ...P-glycoprotein (Pgp) might play a role in flavopiridol resistance, we examined flavopiridol sensitivity in a pair of Chinese hamster ovary cell lines differing with respect to level of Pgp expression. The IC(50)s of flavopiridol in parental AuxB1 (lower Pgp) and colchicine-selected CH(R)C5 (higher Pgp) cells were 90.2 +/- 6.6 nM and 117 +/- 2.3 nM, respectively (P< 0.01), suggesting that Pgp might have a modest effect on flavopiridol action. Consistent with this hypothesis, pretreatment with either quinidine or verapamil (inhibitors of Pgp-mediated transport) sensitized CH(R)C5 cells to the antiproliferative effects of flavopiridol. Because of concern that colony forming assays might not accurately reflect cytotoxicity, we also examined flavopiridol-treated cells by trypan blue staining and flow cytometry. These assays confirmed that flavopiridol was less toxic to cells expressing higher levels of Pgp. Further experiments revealed that flavopiridol inhibited the binding of 3H-azidopine to Pgp in isolated membrane vesicles, but only at high concentrations. Collectively, these results identify flavopiridol as a weak substrate for Pgp.
Flavopiridol, the first inhibitor of cyclin-dependent kinases to enter clinical trials, has shown promising antineoplastic activity and is currently undergoing Phase II testing. Little is known about ...mechanisms of resistance to this agent. In the present study, we have characterized an ovarian carcinoma cell line OV202 high passage (hp) that spontaneously developed drug resistance upon prolonged passage in tissue culture. Standard cytogenetic analysis and spectral karyotyping revealed that OV202 hp and the parental low passage line OV202 shared several marker chromosomes, confirming the relatedness of these cell lines. Immunoblotting demonstrated that OV202 and OV202 hp contained similar levels of a variety of polypeptides involved in cell cycle regulation, including cyclin-dependent kinases 2 and 4; cyclins A, D1, and E; and proliferating cell nuclear antigen. Despite these similarities, OV202 hp was resistant to flavopiridol and cisplatin, with increases of 5- and 3-fold, respectively, in the mean drug concentrations required to inhibit colony formation by 90%. In contrast, OV202 hp and OV202 displayed indistinguishable sensitivities to oxaliplatin, paclitaxel, topotecan, 1,3-bis(2-chloroethyl)-1-nitrosourea, etoposide, doxorubicin, vincristine, and 5-fluorouracil, suggesting that the spontaneously acquired resistance was not attributable to altered P-glycoprotein levels or a general failure to engage the cell death machinery. After incubation with cisplatin, whole cell platinum and platinum-DNA adducts measured using mass spectrometry were lower in OV202 hp cells than OV202 cells. Similarly, after flavopiridol exposure, whole cell flavopiridol concentrations measured by a newly developed high performance liquid chromatography assay were lower in OV202 hp cells. These data are consistent with the hypothesis that acquisition of spontaneous resistance to flavopiridol and cisplatin in OV202 hp cells is due, at least in part, to reduced accumulation of the respective drugs. These observations not only provide the first characterization of a flavopiridol-resistant cell line but also raise the possibility that alterations in drug accumulation might be important in determining sensitivity to this agent.
Radionuclide sentinel lymph node localization and biopsy is a staging procedure that is being increasingly used to evaluate patients with invasive breast cancer who have clinically normal axillary ...nodes. The most important prognostic indicator in patients with invasive breast cancer is the axillary node status, which must also be known for correct staging, and influences the selection of adjuvant therapies. The accuracy of sentinel lymph node localization depends on a number of factors, including the injection method, the operating surgeon's experience and the hospital setting. The efficacy of sentinel lymph node mapping can be determined by two measures: the sentinel lymph node identification rate and the false-negative rate. Of these, the false-negative rate is the most important, based on a review of 92 studies. As sentinel lymph node procedures vary widely, nuclear medicine physicians and radiologists must be acquainted with the advantages and disadvantages of the various techniques. In this review, the factors that influence the success of different techniques are examined, and studies which have investigated false-negative rates and/or sentinel lymph node identification rates are summarized.
To review recent developments and to examine the role of nuclear medicine-based radionuclide therapy in the management of bone metastases.
Recent developments in the use of radionuclides were broadly ...reviewed in the context of treatment paradigms, radionuclide toxicity, cost, and overall outcomes, and an impression of the use of radionuclides in metastatic bone disease was derived.
Through a number of studies, radionuclide therapy has been shown to be an efficacious and cost-effective means of alleviating bone pain in metastatic disease. Moreover, its early use in pain therapy may limit cancer progression by inhibiting oligometastases. Thus, radionuclides can significantly decrease patient morbidity, increase patient survival, and perhaps attenuate the aggressiveness of cancer. Nonetheless, in comparison with analgesics, external beam radiotherapy, or surgery, it still appears to have lower priority among medical oncologists.
Bone pain palliation is critical for cancer patients afflicted with bone metastases, but radionuclides remain underutilized in such treatments. The authors propose that physician education regarding radionuclide therapy be improved and additional investigations to evaluate newer radionuclides and treatment paradigms (eg, higher activities, repetitive or cyclic administration, chemosensitization, or chemosupplementation) be strongly encouraged. A comprehensive and an interdisciplinary clinical approach toward increasing the use of radionuclides in alleviating metastatic bone pain is proposed. Data from clinical collaborations will help optimize radiopharmaceutical therapy for pain palliation, increase its awareness among oncologists, and contribute effectively to patient palliation and quality-of-life improvements.
Vitamin D shows significant potential as a therapy for prostate cancer. However, its use in clinical trials has been hampered by its induction of hypercalcemia at serum concentrations required to ...suppress cancer cell proliferation. This has spurred the development of less calcemic analogs of vitamin D. In this article, we review the clinical trials and consider the future directions of the use of vitamin D and its analogs in the treatment or chemoprevention of prostate cancer. First, we summarize the epidemiological evidence leading to the hypothesis that vitamin D has anticancer activity. We then review the clinical trials using vitamin D analogs that involve patients with prostate cancer and conclude with a brief overview of our planned study with vitamin D5, 1alpha(OH)D5, which will begin shortly. Data for this review were identified by searches of PubMed, the Cochrane Library, Biosis, and references from relevant articles, using the search terms "vitamin D," "prostate cancer," "chemoprevention" and "vitamin D analog." Abstracts from recent international meetings were also reviewed but were only included when they were the only known reference to the clinical trial or the research mentioned. Only papers published in English were included.
Abstract
Background
Endoscopic Retrograde Cholangiopancreatography (ERCP) brush cytology is the most frequently used tool for sampling indeterminate biliary strictures. Previous studies have ...demonstrated that the diagnostic yield of brush cytology for malignant biliary strictures is 60%. With improved diagnostic tools, sampling techniques and specimen processing, the yield of ERCP brush cytology may be higher.
Aims
To assess the diagnostic yield of ERCP brush cytology in patients with indeterminate biliary strictures and to determine factors associated with positive diagnosis.
Methods
This is a retrospective study of all patients who underwent ERCP with brush cytology at University Health Network (UHN) from October 2016 to September 2019. The cytological samples were taken as follows: the cytology brush is introduced into the stricture ten times under direct fluoroscopy guidance. The brush was cut and placed into a methanol based buffered solution (CytoLyt®). Residual sample was then flushed out of the catheter with the solution and into the sample container. Patient demographic, clinical, procedural and pathological data was collected by chart review. All patients were followed for a minimum of three months after their index ERCP. Post-ERCP sampling via repeat ERCP brushings, endoscopic ultrasound fine needle biopsy, percutaneous biopsy or surgical resection was recorded.
Results
A total of 97 patients underwent ERCP with brush cytology during the study period (43 females, median age 69 years). Fifty-nine patients (84%) were diagnosed with malignancy via ERCP brush cytology. Using follow up sampling, surgical resection and clinical follow up as the gold standard, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 84%, 100%, 100%, and 71% respectively. Patient demographics, degree of cholestasis or stricture location had no significant impact on these outcomes.
Conclusions
This study shows a high diagnostic yield for ERCP with brush cytology for patients with indeterminate biliary strictures. Large prospective studies using updated tools, techniques and specimen handling processes are needed to confirm our observations.
Funding Agencies
None
Dairy cows undergo significant metabolic and endocrine changes during the transition from pregnancy to lactation, and impaired insulin action influences nutrient partitioning toward the fetus and the ...mammary gland. Because impaired insulin action during transition is thought to be related to elevated body condition and body fat mobilization, we hypothesized that over-conditioned cows with excessive body fat mobilization around calving may have impaired insulin metabolism compared with cows with low fat mobilization. Nineteen dairy cows were grouped according to their average concentration of total liver fat (LFC) after calving in low LLFC; LFC <24% total fat/dry matter (DM); n=9 and high (HLFC; LFC >24.4% total fat/DM; n=10) fat-mobilizing cows. Blood samples were taken from wk 7 antepartum (ap) to wk 5 postpartum (pp) to determine plasma concentrations of glucose, insulin, glucagon, and adiponectin. We applied euglycemic-hyperinsulinemic (EGHIC) and hyperglycemic clamps (HGC) in wk 5 ap and wk 3 pp to measure insulin responsiveness in peripheral tissue and pancreatic insulin secretion during the transition period. Before and during the pp EGHIC, 13C6 glucose was infused to determine the rate of glucose appearance (GlucRa) and glucose oxidation (GOx). Body condition, back fat thickness, and energy-corrected milk were greater, but energy balance was lower in HLFC than in LLFC. Plasma concentrations of glucose, insulin, glucagon, and adiponectin decreased at calving, and this was followed by an immediate increase of glucagon and adiponectin after calving. Insulin concentrations ap were higher in HLFC than in LLFC cows, but the EGHIC indicated no differences in peripheral insulin responsiveness among cows ap and pp. However, GlucRa and GOx:GlucRa during the pp EGHIC were greater in HLFC than in LLFC cows. During HGC, pancreatic insulin secretion was lower, but the glucose infusion rate was higher pp than ap in both groups. Plasma concentrations of nonesterified fatty acids decreased during HGC and EGHIC, but in both clamps, pp nonesterified fatty acid concentrations did not reach the ap levels. The study demonstrated a minor influence of different degrees of body fat mobilization on insulin metabolism in cows during the transition period. The distinct decrease in the glucose-dependent release of insulin pp is the most striking finding that explains the impaired insulin action after calving, but does not explain differences in body fat mobilization between HLFC and LLFC cows.
Our aim was to compare the energy balance estimated (EBest) according to equations published by various energy feeding systems (German Society for Nutrition Physiology, French National Institute for ...Agricultural Research, and US National Research Council) and the EB calculated by use of calorimetrically measured heat production (EBhp) of 20 high-yielding (≥10,000 kg/305 d) German Holstein cows at −4 (pregnant, nonlactating) and 2 wk (early lactation) relative to parturition. In addition to heat production, feed and water intake, physical activity (including standing-lying behavior), body weight, body condition score, body temperature, plasma concentrations of fatty acids and β-hydroxybutyrate, milk yield, and milk composition were measured to characterize the metabolic status. The EBhp was balanced 2.74 ± 4.09 MJ of metabolizable energy (ME)/d; ±standard error before calving, but strongly negative (−84.7 ± 7.48 MJ of ME/d) at wk 2 of lactation. At both time points, EBhp and EBest differed significantly. On average, the equations overestimated the antepartum EB by 33 MJ of ME/d and underestimated the postpartum negative EB by 67 MJ of ME/d, respectively. Because the same ME intake and energy-corrected milk values were used for calculation of EBest and EBhp in our study, we considered that the factors (0.488 to 0.534 MJ of ME/kg0.75) currently used to calculate the ME requirements for maintenance probably underestimate the needs of high-yielding dairy cows, particularly during early lactation. In accord, heat production values determined under standard conditions of thermoneutrality and locomotion restriction amounted to 0.76 ± 0.02 MJ of ME/kg0.75 (4 wk antepartum) and 1.02 ± 0.02 MJ of ME/kg0.75 (2 wk postpartum), respectively. The expected positive correlation between EBhp and DMI was observed in pregnant cows only; however, a bias of 26 MJ of ME/d between mean actual energy intake and ME intake predicted according to German Society for Nutrition Physiology was found in cows at wk 4 antepartum. At both investigated time points, mobilization of tissue energy reserves (reflected by plasma fatty acid concentration) was related to EBhp. In early lactating cows, metabolic body weight (kg0.75) and the percentage of milk fat showed the strongest correlation (correlation coefficient = −0.70 and −0.73) to EBhp. Our findings must be taken into account when experimental data are interpreted because the true energy status might be significantly overestimated when EBest is used.
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