Efficacy of the phosphoinositol 3 kinase (PI3K) inhibitor GDC-0941 in patient- and cell-line-derived xenografts of dedifferentiated liposarcoma (DDLPS).

Abstract

e13528 Background: Analysis of primary clinical specimens of DDLPS revealed evidence of AKT activation in 27% of cases (Gutierrez A, et al. Aberrant AKT activation drives well-differentiated liposarcoma. PNAS 2011; 108(39):16386-91). We evaluated the efficacy of the PI3K inhibitor GDC-0941 (GDC) alone and in combination with doxorubicin (DOX) in patient- and cell-line derived DDLPS xenografts with proven PI3K/AKT pathway activation. Methods: NMRI nu/nu mice were either injected bilaterally with 1x107SW872 cells or transplanted with human DDLPS (UZLX-STS3). Animals were randomized to 4 groups (6 mice/group) and treated for two weeks: vehicle, DOX (i.p., 1.2mg/kg/biw), GDC (p.o., 75mg/kg/qd), GDC+DOX (same dose/schedule as single agents). Efficacy was assessed by tumor volume assessment, Western blotting and histological evaluation (H&E). Mitotic and apoptotic effects were confirmed using immunostainings for phospho-histone H3 (p-H3) (for proliferation), and cleaved caspase 3 (CC3) (for apoptosis). Results: GDC and GDC+DOX significantly delayed the growth of both xenografts (74% decrease under GDC and 77% under GDC+DOX in SW872, 67% under GDC and 56% under GDC+DOX in UZLX-STS3, vs. control). GDC and GDC+DOX treatment resulted in reduced mitotic activity and increase in apoptosis, as compared to untreated tumors in both models (Table). The activation of PI3K signaling was nearly completely suppressed in the GDC and GDC+DOX treated groups in SW872, whilea weak activation of the pathway was still observed in UZLX-STS3. Conclusions: GDC-0941 has anti-tumor activity, decreases tumor proliferation and induces apoptosis in DDLPS with PI3K/AKT activation. The GDC+DOX combination did not show additive effect in vivo. [Table: see text]