digitoxin and Breast-Neoplasms

The efficacy of chemotherapy is hindered by both tumor heterogeneity and acquired or intrinsic multi-drug resistance caused by the contribution of multidrug resistance proteins and stemness-associated prosurvival markers. Therefore, targeting multi-drug resistant cells would be much more effective against cancer. In this study, we characterized the chemoresistance properties of adherent (anchorage-dependent) lung H460 and breast MCF-7 cancer cells growing under prolonged periods of serum starvation (PPSS). We found that under PPSS, both cell lines were highly resistant to Paclitaxel, Colchicine, Hydroxyurea, Obatoclax, Wortmannin, and LY294002. Levels of several proteins associated with increased stemness such as Sox2, MDR1, ABCG2, and Bcl-2 were found to be elevated in H460 cells but not in MCF-7 cells. While pharmacological inhibition of either MDR1, ABCG2, Bcl-2 with Verapamil, Sorafenib, or Obatoclax, respectively decreased the levels of their target proteins under routine culture conditions as expected, such inhibition did not reverse PX resistance in PPSS conditions. Paradoxically, treatment with inhibitors in serum-starved conditions produced an elevation of their respective target proteins. In addition, we found that Digitoxin, an FDA approved drug that decrease the viability of cancer cells growing under PPSS, downregulates the expression of Sox2, MDR1, phospho- AKT, Wnt5a/b, and β-catenin. Our data suggest that PPSS-induced chemoresistance is the result of extensive rewiring of intracellular signaling networks and that multi-resistance can be effectively overcome by simultaneously targeting multiple targets of the rewired network. Furthermore, our PPSS model provides a simple and useful tool to screen drugs for their ability to target multiple pathways of cancer resistance. J. Cell. Physiol. 232: 2033-2043, 2017. © 2016 Wiley Periodicals, Inc.

Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily G, Member 2; Breast Neoplasms; Cell Culture Techniques; Cell Proliferation; Cell Survival; Culture Media, Serum-Free; Digitoxin; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Drug Screening Assays, Antitumor; Energy Metabolism; Female; Gene Expression Regulation, Neoplastic; Humans; Lung Neoplasms; MCF-7 Cells; Models, Biological; Neoplasm Proteins; Paclitaxel; Proto-Oncogene Proteins c-bcl-2; Signal Transduction; Time Factors

The cardiac glycoside digitoxin preferentially inhibits the growth of breast cancer cells and targets the Erk pathway. Digitoxin alters the expression of genes that mediate calcium metabolism and IAP genes.. Since the optimal treatment for cancer involves the use of agents in combination, we assessed the growth inhibitory effects of digitoxin combined with agents that alter calcium metabolism, thapsigargin, a sarcoplasmic/ER Ca(2+)-ATPase inhibitor, and the statin simvastatin, as well as digitoxin's effect on the IAP pathway of apoptosis.. To reveal signaling pathways, we treated human cancer cells with digitoxin, alone or combined with thapsigargin or simvastatin, and measured cell growth using the MTT and colony formation assays. We used histology and Western blot analysis of HEK293 cells to assay effects on IAPs.. Digitoxin inhibited the growth of breast, colon and ovarian cancer cells. Consistent with an effect on calcium metabolism, digitoxin exhibited synergy with thapsigargin and simvastatin on ER-negative breast cancer cells. Digitoxin activates expression of Erk pathway genes and suppresses expression of IAP genes. The growth inhibitory effects on HEK293 cells are not blocked by the pancaspase inhibitor zVAD-FMK, indicating that digitoxin may act by a caspase independent pathway of apoptosis. Furthermore, digitoxin does not have an effect on XIAP protein, a major anti-apoptotic protein.. Digitoxin appears to act through the Erk and stress response pathways and is worthwhile to study to prevent and treat cancer. Our findings warn of possible safety issues for cardiac patients who take a combination of digitoxin and statins.

Topics: Apoptosis; Breast Neoplasms; Cell Line, Tumor; Digitoxin; Drug Synergism; HEK293 Cells; Humans; Inhibitor of Apoptosis Proteins; Signal Transduction; Simvastatin; Thapsigargin

The Na+K+-ATPase is a known target of cardiac glycosides such as digitoxin and ouabain. We determined that the enzyme also is a target of the structurally-related triterpene glycoside actein, present in the herb black cohosh. Actein's inhibition of Na+-K+-ATPase activity was less potent than that of digitoxin, but actein potentiated digitoxin's inhibitory effect on Na+-K+-ATPase activity and MDA-MB-453 breast cancer cell growth. We observed different degrees of signal amplification for the two compounds. Actein's inhibitory effect on ATPase activity was amplified 2-fold for cell growth inhibition, whereas digitoxin's signal was amplified 20-fold. Actein induced a biphasic response in proteins downstream of ATPase: low dose and short duration of treatment upregulated NF-kappaB promoter activity, p-ERK, p-Akt and cyclin D1 protein levels, whereas higher doses and longer exposure inhibited these activities. Actein and digitoxin may be a useful synergistic combination for cancer chemoprevention and/or therapy.

Topics: Antineoplastic Agents; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Digitoxin; Drug Synergism; Drugs, Chinese Herbal; Enzyme Inhibitors; Humans; Mitogen-Activated Protein Kinase 1; NF-kappa B; Promoter Regions, Genetic; RNA Interference; Saponins; Sodium-Potassium-Exchanging ATPase; Triterpenes

Laboratory and epidemiologic studies have suggested a modifying effect of cardiac glycosides (for example, digoxin and digitoxin) on cancer risk. We explored the association between digoxin treatment and invasive breast cancer incidence among postmenopausal Danish women.. We used Danish registries to identify 5,565 postmenopausal women diagnosed with incident invasive breast carcinoma between 1 January 1991 and 31 December 2007, and 55,650 matched population controls. Cardiac glycoside prescriptions were ascertained from county prescription registries. All subjects had at least 2 years of recorded prescription drug and medical history data. We estimated the odds ratio associating digoxin use with breast cancer in conditional logistic regression models adjusted for age, county of residence, and use of anticoagulants, non-steroidal anti-inflammatory drugs (NSAIDs), aspirin, and hormone replacement therapy. We also explored the impact of confounding by indication and detection bias.. Digoxin was the sole cardiac glycoside prescribed to subjects during the study period. There were 324 breast cancer cases (5.8%) and 2,546 controls (4.6%) with a history of digoxin use at least 1 year before their index date (adjusted odds ratio (OR): 1.30; 95% confidence interval: 1.14 to 1.48). The breast cancer OR increased modestly with increasing duration of digoxin exposure (adjusted OR for 7 to 18 years of digoxin use: 1.39; 95% confidence interval: 1.10 to 1.74). The association was robust to adjustment for age, receipt of hormone replacement therapy, coprescribed drugs, and confounding by indication. A comparison of screening mammography rates between cases and controls showed no evidence of detection bias.. Our results suggest that digoxin treatment increases the risk of invasive breast cancer among postmenopausal women.

Topics: Aged; Aged, 80 and over; Breast Neoplasms; Cardiotonic Agents; Cardiovascular Diseases; Case-Control Studies; Digitoxin; Digoxin; Female; Humans; Incidence; Middle Aged; Postmenopause; Prospective Studies; Risk Factors

Topics: Antineoplastic Agents; Breast Neoplasms; Cardenolides; Cell Death; Digitoxin; Humans; Plant Extracts; Plants; Tumor Cells, Cultured

Topics: Breast Neoplasms; Cardiac Glycosides; Cell Division; Digitalis; Digitoxin; Digoxin; Female; Humans; Plants, Medicinal; Plants, Toxic; Tumor Cells, Cultured

Aminoglutethimide is an aromatase inhibitor that is successfully used for endocrine treatment of advanced breast cancer. This drug also stimulates the activity of hepatic mixed-function oxidases, increasing the metabolism of several drugs, including warfarin, digitoxin, antipyrine and theophylline. It also increases the plasma clearance rate of oestrone sulphate. As this oestrogen may be an important substrate for tumour cells, stimulation of oestrone sulphate metabolism may be a component of the mechanism of action of aminoglutethimide.

Topics: Aminoglutethimide; Antipyrine; Aromatase Inhibitors; Breast Neoplasms; Digitoxin; Drug Interactions; Estrogens; Humans; Theophylline; Warfarin

The influence of two progestins, medroxyprogesterone acetate (MPA) and megestrol acetate (MA), given orally in high doses, on the pharmacokinetics of antipyrine, digitoxin, and warfarin were studied in patients with advanced breast cancer. Antipyrine and warfarin were given as a single test dose before and after 5 weeks of progestin treatment. The pharmacokinetics of digitoxin was investigated at steady state in patients receiving this drug therapeutically before and during treatment with progestins. Small changes in clearance rates for antipyrine, warfarin, and digitoxin were found. A minor decrease observed in warfarin clearance however may be of clinical importance. Half-lives decreased by 13% for antipyrine and increased by 71% for warfarin. High-dose progestins given orally do not seem to have a major influence on drug metabolism, probably reflecting a minor effect on drug and steroid-metabolizing microsomal mono-oxygenases in the liver.

Topics: Administration, Oral; Aged; Aged, 80 and over; Antipyrine; Breast Neoplasms; Digitoxin; Female; Humans; Kinetics; Male; Medroxyprogesterone; Medroxyprogesterone Acetate; Megestrol; Megestrol Acetate; Middle Aged; Progesterone Congeners; Warfarin

The influence of aminoglutethimide (AG) on antipyrine, theophylline, and digitoxin kinetics was examined. Antipyrine was given as a single test dose before and after 3 mo of AG treatment, whereas theophylline and digitoxin kinetics were investigated at steady state in patients receiving these drugs therapeutically before and after AG therapy. During AG treatment, mean clearance rates for antipyrine, theophylline, and digitoxin increased by 81%, 32%, and 109%. Together with earlier reports of effects of AG on warfarin and dexamethasone disposition and on its own metabolism, these findings indicate that AG is a potent inducer of drug metabolizing microsomal monooxygenases of the liver. Since many drugs known to be metabolized by this enzyme system are frequently used for concomitant conditions in patients with breast cancer, interactions with AG are to be expected.

Topics: Adult; Aged; Aminoglutethimide; Antipyrine; Breast Neoplasms; Chromatography, High Pressure Liquid; Digitoxin; Drug Interactions; Female; Humans; Kinetics; Male; Middle Aged; Theophylline