6-bromoindirubin-3--oxime and Breast-Neoplasms

TRAIL (TNFα-related apoptosis-inducing factor) has been promoted as a promising anti-cancer agent. Unfortunately many tumor cells develop resistance towards TRAIL due to numerous defects in apoptotic signaling. To handle this problem combination therapy with compounds affecting as many different anti-apoptotic targets as possible might be a feasible approach. The bromo-substituted indirubin derivative 6BIO meets this challenge: Treatment of breast cancer and bladder carcinoma cell lines with micromolar concentrations of 6BIO abrogates cellular growth and induces apoptosis. Combination of subtoxic amounts of 6BIO with ineffective doses of TRAIL completely abolishes proliferation and long-term survival of cancer cells. As shown in two-dimensional as well as three-dimensional cell culture models, 6BIO potently augments TRAIL-induced apoptosis in cancer cell lines. The potent chemosensitizing effect of 6BIO to TRAIL-mediated cell death is due to the pleiotropic inhibitory profile of 6BIO. As shown previously, 6BIO abrogates STAT3, PDK1 as well as GSK3 signaling and moreover, inhibits the expression of the anti-apoptotic Bcl-2 family members Bcl-xL and Mcl-1 on mRNA as well as on protein level, as demonstrated in this study. Moreover, the expression of cFLIP and cIAP1 is significantly downregulated in 6BIO treated cancer cell lines. In sum (subtoxic concentration of) the multi-kinase inhibitor 6BIO serves as a potent chemosensitizing agent fighting TRAIL resistant cancer cells.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Cell Survival; Drug Resistance, Neoplasm; Female; Glycogen Synthase Kinase 3; Humans; Indoles; Oximes; Protein Kinase Inhibitors; Receptors, TNF-Related Apoptosis-Inducing Ligand; TNF-Related Apoptosis-Inducing Ligand; Urinary Bladder Neoplasms

While metastasis is the chief cause of cancer mortality, there nonetheless remains a lack of antimetastatic therapies that are clinically available. In this study, we present the indirubin derivative 6-bromo-indirubin-3'-oxime (6BIO) as a promising antimetastatic agent. 6BIO strongly reduced formation of lung metastasis in the well-established 4T1 mouse model of aggressive breast cancer. Several major hallmarks of the metastatic process were affected by subtoxic concentrations of 6BIO, which inhibited adhesion, migration, and invasion of a variety of metastatic cell types in vitro. Mechanistic analyses focused on known targets of 6BIO, which were silenced by this compound. Unexpectedly, RNAi-mediated silencing of glycogen synthase kinase 3β (GSK3β) and phosphoinositide-dependent protein kinase 1 (PDK1), both modulators of cellular metastasis targeted by 6BIO, were not found to affect invasive migration in this study. Instead, the Jak/STAT3 signaling pathway appeared to play a major role through modulation of its downstream migration regulators C-terminal tensin-like protein and matrix metalloproteinase 2. However, PDK1 and GSK3β contributed to the overall response to 6BIO, as silencing of all three pathways resulted in almost complete inhibition of migration, phenocopying the 6BIO response. Taken together, our findings illustrate the antimetastatic activity of 6BIO on the basis of its ability to simultaneously inhibit several kinase cascades involved in metastasis of cancer cells, supporting the concept of "polypharmacology" in developing drugs to attack metastasis, the most deadly aspect of cancer.

Topics: Animals; Apoptosis; Blotting, Western; Breast Neoplasms; Cell Adhesion; Cell Movement; Cell Proliferation; Chemotaxis; Female; Glycogen Synthase Kinase 3; Humans; Indoles; Lung Neoplasms; Matrix Metalloproteinase 2; Mice; Mice, Inbred BALB C; Oximes; Phosphorylation; Protein Serine-Threonine Kinases; Pyruvate Dehydrogenase Acetyl-Transferring Kinase; Signal Transduction; Spheroids, Cellular; STAT Transcription Factors

Indirubin derivatives gained interest in recent years for their anticancer and antimetastatic properties. The objective of the present study was to evaluate and compare the anticancer properties of the two novel bromo-substituted derivatives 6-bromoindirubin-3'-oxime (6BIO) and 7-bromoindirubin-3'-oxime (7BIO) in five different breast cancer cell lines. Cell viability assays identified that 6BIO and 7BIO are most effective in preventing the proliferation of the MDA-MB-231-TXSA breast cancer cell line from a total of five breast cancer cell lined examined. In addition it was found that the two compounds induce apoptosis via different mechanisms. 6BIO induces caspase-dependent programmed cell death through the intrinsic (mitochondrial) caspase-9 pathway. 7BIO up-regulates p21 and promotes G(2)/M cell cycle arrest which is subsequently followed by the activation of two different apoptotic pathways: (a) a pathway that involves the upregulation of DR4/DR5 and activation of caspase-8 and (b) a caspase independent pathway. In conclusion, this study provides important insights regarding the molecular pathways leading to cell cycle arrest and apoptosis by two indirubin derivatives that can find clinical applications in targeted cancer therapeutics.

Topics: Apoptosis; Breast Neoplasms; Cell Cycle; Cell Line, Tumor; Female; Humans; Indoles; Neoplasm Invasiveness; Oximes