Selective, novel spleen tyrosine kinase (Syk) inhibitors suppress chronic lymphocytic leukemia B-cell activation and migration

Leukemia. 2012 Jul;26(7):1576-83. doi: 10.1038/leu.2012.24. Epub 2012 Feb 7.

Abstract

Syk is a protein tyrosine kinase that couples B-cell receptor (BCR) activation with downstream signaling pathways, affecting cell survival and proliferation. Moreover, Syk is involved in BCR-independent functions, such as B-cell migration and adhesion. In chronic lymphocytic leukemia (CLL), Syk becomes activated by external signals from the tissue microenvironment, and was targeted in a first clinical trial with R788 (fostamatinib), a relatively nonspecific Syk inhibitor. Here, we characterize the activity of two novel, highly selective Syk inhibitors, PRT318 and P505-15, in assays that model CLL interactions with the microenvironment. PRT318 and P505-15 effectively antagonize CLL cell survival after BCR triggering and in nurse-like cell-co-cultures. Moreover, they inhibit BCR-dependent secretion of the chemokines CCL3 and CCL4 by CLL cells, and leukemia cell migration toward the tissue homing chemokines CXCL12, CXCL13, and beneath stromal cells. PRT318 and P505-15 furthermore inhibit Syk and extracellular signal-regulated kinase phosphorylation after BCR triggering. These findings demonstrate that the selective Syk inhibitors PRT318 and P505-15 are highly effective for inhibition of CLL survival and tissue homing circuits, and support the therapeutic development of these agents in patients with CLL, other B-cell malignancies and autoimmune disorders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects
  • Blotting, Western
  • Cell Adhesion / drug effects
  • Cell Movement / drug effects*
  • Cell Proliferation / drug effects
  • Chemotaxis
  • Cyclohexylamines / pharmacology*
  • Enzyme-Linked Immunosorbent Assay
  • Flow Cytometry
  • Humans
  • Intracellular Signaling Peptides and Proteins / antagonists & inhibitors*
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Leukemia, Lymphocytic, Chronic, B-Cell / drug therapy*
  • Leukemia, Lymphocytic, Chronic, B-Cell / enzymology
  • Leukemia, Lymphocytic, Chronic, B-Cell / pathology*
  • Phosphorylation / drug effects
  • Protein Kinase Inhibitors / pharmacology*
  • Protein-Tyrosine Kinases / antagonists & inhibitors*
  • Protein-Tyrosine Kinases / metabolism
  • Pyrimidines / pharmacology*
  • Stromal Cells / cytology
  • Stromal Cells / drug effects
  • Stromal Cells / metabolism
  • Syk Kinase
  • Tumor Cells, Cultured

Substances

  • 2-(2-aminocyclohexylamino)-4-(m-tolylamino)pyrimidine-5-carboxamide
  • 4-(3-(2H-1,2,3-triazol-2-yl)phenylamino)-2-(2-aminocyclohexylamino)pyrimidine-5-carboxamide
  • Cyclohexylamines
  • Intracellular Signaling Peptides and Proteins
  • Protein Kinase Inhibitors
  • Pyrimidines
  • Protein-Tyrosine Kinases
  • SYK protein, human
  • Syk Kinase