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Oncogene. 2014 Jan 16;33(3):316-25. doi: 10.1038/onc.2012.594. Epub 2013 Jan 14.

The PI3K inhibitor GDC-0941 combines with existing clinical regimens for superior activity in multiple myeloma.

Author information

1
Department of Cancer Immunotherapy and Hematology, Genentech Inc., South San Francisco, CA, USA.
2
Department of Oncology Biomarker Development, Genentech Inc., South San Francisco, CA, USA.
3
Department of Medicine, Comprehensive Cancer Center, Mayo Clinic, Scottsdale, AZ, USA.

Abstract

The phosphatidylinositol 3'-kinase (PI3K) pathway is dysregulated in multiple myeloma (MM); we therefore tested a highly selective class I PI3K inhibitor, GDC-0941, for anti-myeloma activity. Functional and mechanistic studies were first performed in MM cell lines, then extended to primary MM patient samples cultured in vitro. GDC-0941 was then assessed as a single agent and in various combinations in myeloma tumor xenograft models. We show p110 α and β are the predominant PI3K catalytic subunits in MM and that a highly selective class I PI3K inhibitor, GDC-0941, has robust activity as a single agent to induce cell cycle arrest and apoptosis of both MM cell lines and patient myeloma cells. Mechanistic studies revealed an induction of cell cycle arrest at G0/G1, with decreased phospho-FoxO1/3a levels, decreased cyclin D1 and c-myc expression, and an increase in the cell cycle inhibitor, p27kip. Induction of apoptosis correlated with increased expression of the pro-apoptotic BH3-only protein BIM, cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase (PARP). In vitro, GDC-0941 synergized with dexamethasone (Dex) and lenalidomide (combination index values of 0.3-0.4 and 0.4-0.8, respectively); in vivo GDC-0941 has anti-myeloma activity and significantly increases the activity of the standard of care agents in several murine xenograft tumor models (additional tumor growth inhibition of 37-53% (Dex) and 22-72% (lenalidomide)). These data provide a clear therapeutic hypothesis for the inhibition of PI3K and provide a rationale for clinical development of GDC-0941 in myeloma.

PMID:
23318440
DOI:
10.1038/onc.2012.594
[Indexed for MEDLINE]

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