Integrin-linked kinase (ILK) was assesed as a therapeutic target in
glioblastoma xenograft models through multiple endpoints including treatment related changes in the tumor microenvironment.
Glioblastoma cell lines were tested in vitro for sensitivity toward the small-molecule inhibitors QLT0254 and
QLT0267. Cell viability, cell cycle, and apoptosis were evaluated using MTT assay, flow cytometry,
caspase activation, and
DAPI staining. Western blotting and ELISA were used for
protein analysis (ILK, PKB/Akt,
VEGF, and HIF-1alpha). In vivo assessment of growth rate, cell proliferation, BrdUrd, blood vessel mass (CD31 labeling), vessel perfusion (
Hoechst 33342), and
hypoxia (EF-5) was done using U87MG
glioblastoma xenografts in RAG2-M mice treated orally with
QLT0267 (200 mg/kg q.d.). ILK inhibition in vitro with QLT0254 and
QLT0267 resulted in decreased levels of phospho-PKB/Akt (Ser473), secreted
VEGF, G2-M block, and apoptosis induction. Mice treated with
QLT0267 exhibited significant delays in
tumor growth (treated 213 mm3 versus control 549 mm3). In situ analysis of U87MG
tumor cell proliferation from QLT0267-treated mice was significantly lower relative to untreated mice. Importantly,
VEGF and HIF-1alpha expression decreased in QLT0267-treated
tumors as did the percentage of blood vessel mass and numbers of
Hoechst 33342 perfused
tumor vessels compared with control
tumors (35% versus 83%). ILK inhibition with novel small-molecule inhibitors leads to treatment-associated delays in
tumor growth, decreased
tumor angiogenesis, and functionality of
tumor vasculature. The
therapeutic effects of a selected ILK inhibitor (
QLT0267) should be determined in the clinic in
cancers that exhibit dysregulated ILK, such as PTEN-null
glioblastomas.