digitoxin and digitoxose

Despite significant advances in the understanding of lung cancer biology, the prognosis of cancer patients remains poor. Part of the failure of anticancer therapy is due to intratumoral heterogeneity in these patients that limits the efficacy of single agents. Therefore, there is an urgent need for new anticancer drugs or drug combination regimens that possess increased activity against all cellular subtypes found within the tumor. In this study, we evaluated the in vitro antiproliferative activity of the cardiac glycosides (CGs) digitoxin and its synthetic analog MonoD on H460 lung cancer cells grown under different culture conditions. The CGs were tested alone in H460 cells under routine culture as well as in cells growing under short (24-72 h) and prolonged serum starvation (7 days) in order to evaluate the activity of drugs on cancer cells under varied degrees of proliferation. Our results showed that both CGs, and MonoD in particular, have potent antiproliferative activity at clinically relevant concentrations against cells in all the tested culture conditions. In contrast, paclitaxel, hydroxyurea and colchicine were only active in cells growing in routine culture conditions, and relatively inactive in serum-starved conditions. Importantly, both CGs were able to potentiate the effect of clinically relevant concentrations of hydroxyurea or paclitaxel in serum-starved conditions. When paclitaxel was used in combination with CGs, the highest antiproliferative effect was obtained when paclitaxel was administered first, followed by either digitoxin or MonoD. Our results indicate that CGs have potential clinical applications in translational oncology especially in combination with other drugs, and warrants further investigation of CGs in more advanced preclinical models of lung cancer.

Topics: Antineoplastic Agents; Cell Line, Tumor; Cell Proliferation; Digitoxin; Drug Synergism; Hexoses; Humans; Hydroxyurea; Inhibitory Concentration 50; Lung Neoplasms; Paclitaxel

In order to obtain specific antisera to digitoxin, four new types of hapten-bovine serum albumin (BSA) conjugates were synthesized from digitoxin. The haptens were linked to the carrier protein through hemisuccinate and hemisuccinylglycine bridges at the C-3' and C-3" positions in the digitoxose chain. The antisera were prepared by immunizing rabbits with each digitoxin-BSA conjugate and the properties of the antisera were investigated by RIA with 3H-labeled digitoxin. Among these antisera, the antiserum raised against digitoxin 3'-hemisuccinate-BSA conjugate possessed high specificity for digitoxin, exhibiting only minor cross-reactions with digitoxigenin bisdigitoxoside (4.0%), dihydrodigitoxin (2.8%), digoxin (2.4%), digitoxigenin monodigitoxoside (0.23%) and digitoxigenin (< 0.05%).

Topics: Animals; Cattle; Cross Reactions; Cross-Linking Reagents; Digitoxin; Haptens; Hexoses; Immune Sera; Rabbits; Radioimmunoassay; Serum Albumin, Bovine; Spectrometry, Mass, Fast Atom Bombardment

The purpose of this investigation was to define, under controlled in vitro conditions, the processes contributing to the uptake and accumulation of [3H]digoxin by incubated slices of chicken renal cortex. Progressive uptake was evident in time-course experiments with the slice-to-medium concentration ratio (S/M) reaching 5.25 after 120 min. No metabolism was evident. Increasing the ratio of unlabeled to labeled digoxin resulted in a concentration-dependent decrease in relative uptake of the label, suggesting saturability. Incubation under conditions of metabolic inhibition reduced digoxin S/M by about 50%, indicating that both energy-requiring and passive mechanisms contribute to the overall accumulation process. The structural nature of the uptake process was explored by incubating digoxin in the presence of potential inhibitors of transport. The organic cation quinine and the non-glycosidic steroids digoxigenin and spironolactone were without effect even at greater than 1000-fold excess compared to digoxin. Similarly, the sugar digitoxose had no inhibitory activity on digoxin accumulation by the slices. On the other hand, the glycosides digitoxin, digoxigenin-bis-digitoxoside and digoxigenin-mono-digitoxoside inhibited dogoxin uptake in a concentration-dependent manner. These results indicate a structural preference for an intact glycoside rather than for either the steroidal or sugar portion of the molecule alone. An inhibitory effect of ouabain and a stimulatory effect of reduced medium potassium concentration suggest a possible role for Na+,K(+)-ATPase in the uptake of digoxin by the renal cortex.

Topics: Animals; Chickens; Digitoxin; Digoxigenin; Digoxin; Female; Hexoses; Kidney Cortex; Kinetics; Ouabain; Potassium; Probenecid; Quinine; Sodium Cyanide; Spironolactone

Topics: Digitalis; Digitalis Glycosides; Glycosides; Hexoses; Plant Extracts