Indirubin derivatives induce apoptosis of chronic myelogenous leukemia cells involving inhibition of Stat5 signaling

Abstract

Indirubin is the major active anti-tumor component of a traditional Chinese herbal medicine used for treatment of chronic myelogenous leukemia (CML). While previous studies indicate that indirubin is a promising therapeutic agent for CML, the molecular mechanism of action of indirubin is not fully understood. We report here that indirubin derivatives (IRDs) potently inhibit Signal Transducer and Activator of Transcription 5 (Stat5) protein in CML cells. Compound E804, which is the most potent in this series of IRDs, blocked Stat5 signaling in human K562 CML cells, imatinib-resistant human KCL-22 CML cells expressing the T315I mutant Bcr-Abl (KCL-22M), and CD34-positive primary CML cells from patients. Autophosphorylation of Src family kinases (SFKs) was strongly inhibited in K562 and KCL-22M cells at 5 μM E804, and in primary CML cells at 10 μM E804, although higher concentrations partially inhibited autophosphorylation of Bcr-Abl. Previous studies indicate that SFKs cooperate with Bcr-Abl to activate downstream Stat5 signaling. Activation of Stat5 was strongly blocked by E804 in CML cells. E804 down-regulated expression of Stat5 target proteins Bcl-xL and Mcl-1, associated with induction of apoptosis. In sum, our findings identify IRDs as potent inhibitors of the SFK/Stat5 signaling pathway downstream of Bcr-Abl, leading to apoptosis of K562, KCL-22M and primary CML cells. IRDs represent a promising structural class for development of new therapeutics for wild type or T315I mutant Bcr-Abl-positive CML patients.

Emerging therapeutic targets in myeloproliferative neoplasms and peripheral T-cell leukemia and lymphomas

“…This agent selectively inhibited the phosphorylation of STAT5 in lymphoma cell lines by unknown mechanisms. Inhibition of STAT5 activity was also reported for Indirubin derivatives, including E804, which blocked STAT5 phosphorylation and STAT5 DNA-binding activity in CML cells [151], associated with downregulation of MCL-1 and BCL2L1 expression. Based on the structure of the compound, the mechanism of inhibition of STAT5 here is most likely suppression of TK activities.…”

Deniz kabuklularında bulunan indigoid boyarmaddelerin metal etkileşimlerinin spektrofotometrik yöntemle incelenmesi

“…Protein kinaz grubu enzimler hücrede farklılaşma, büyüme, proliferasyon, apoptosis kontrolü gibi aşamalarda rol oynarlar ve bu enzimleri aktive veya inhibe edecek ilaç olmaya aday bileşikler geliştirilerek kanser, diyabet, bipolar bozukluk gibi hastalıkların ve inflamasyonun tedavisi için kullanılmaları amacıyla çeşitli araştırmalar yapılmaktadır (7,8). İndirubin ve analoglarının protein kinaz grubu enzimlere van der Waals ve hidrojen bağları ile bağlanarak bahsi geçen enzimleri inhibe ya da aktive ettikleri ve indirubin-3'-monoksim molekülünün yüksek oranda hücre proliferasyonunu engellediği bildirilmiştir (9). Literatürde 6-bromoindirubinin ve 6-bromoindirubinin-3'-oksim analoğunun glikojen sentez kinaz enziminin selektif inhibitörleri olduğunu ve kanser tedavisinde kullanılabileceğini bildiren çalışmalar bulunmaktadır (10,11).…”

A Colorful History: The Evolution of Indigoids

“…Concerning the biological mechanism of action, a number of indirubin analogs potently block constitutively activated Stat3 signaling of human breast and prostate cancer cells. Particularly, in vitro biochemical kinase assay data suggest E804 containing a dihydroxypropyl 3′-oxime ether substituent as a potent inhibitor of Src kinase, down-regulating constitutively activated Stat3 or Stat5 in human breast cancer, CML, and T315I mutant Bcr-Abl expressing CML cells (93,165). However, prolonged modulation against Src activity can cause a recovery of impaired Stat3 activation and thus tumor cell survival through altered JAK/Stat3 interaction (166,167).…”