Sunitinib prolongs survival in genetically engineered mouse models of multistep lung carcinogenesis

Abstract

Non-small cell lung cancer (NSCLC) has a poor prognosis, with substantial mortality rates even among patients diagnosed with early-stage disease. There are few effective measures to block the development or progression of NSCLC. Antiangiogenic drugs represent a new class of agents targeting multiple aspects of tumor progression, including cell proliferation, invasion, migration, and outgrowth of metastatic deposits. We tested the multitargeted angiogenesis inhibitor sunitinib in a novel endogenous mouse model of NSCLC, which expresses a conditional activating mutation in Kras with or without conditional deletion of Lkb1; both alterations are frequent in human NSCLC. We showed that daily treatment with sunitinib reduced tumor size, caused tumor necrosis, blocked tumor progression, and prolonged median survival in both the metastatic (Lkb1/Kras) and nonmetastatic (Kras) mouse models; median survival was not reached in the nonmetastatic model after 1 year. However, the incidence of local and distant metastases was similar in sunitinib-treated and untreated Lkb1/Kras mice, suggesting that prolonged survival with sunitinib in these mice was due to direct effects on primary tumor growth rather than to inhibition of metastatic progression. These collective results suggest that the use of angiogenesis inhibitors in early-stage disease for prevention of tumor development and growth may have major survival benefits in the setting of NSCLC.

Fig. 1

A, cell proliferation assay of tumor-derived cell lines. A549 and H2126 are established human cell lines for comparison with KW-634 and KW-857, derived from Kras mice, and KW-807 and KW-814, derived from Kras/Lkb1^L/L mice. B, Kras or Kras/Lkb1^L/L cell lines or tumor lysates treated with sunitinib at the indicated concentrations were probed for phosphorylated AKT (pAKT) or phosphorylated MAPK (pMAPK). Tumor lysates were whole lung lysates harvested from Kras/Lkb1^L/L mice treated with a single dose of sunitinib at 7 wk after treatment with adeno-Cre (a time point at which mice have well-developed lung tumors). Mice were sacrificed at indicated time points after administration of sunitinib. D, whole lung lysates harvested as in C were probed for phosphorylated VEGFR2 (pVEGFR2), total VEGFR2, or β-actin. E, Kras or Kras/Lkb1^L/L cell lines probed for total VEGFR2 or PDGFRβ. VEGFR2 panels represent a prolonged (>10 min) exposure. H157 is a human lung cancer cell line previously described to express PDGFRβ used as a positive control.

Fig. 2

Representative H&E-stained paraffin sections of lung tissue from control (A and C) or sunitinib-treated (B and D) mice are shown. A and B, tumors from Kras/Lkb1^L/L mice treated for 5 wk with sunitinib or vehicle (both sacrificed at ~9 wk after activation of oncogenic mutations by adeno-Cre). C and D, tumors from Kras mice treated for 11 wk with sunitinib or vehicle (both sacrificed at 27 wk). Insets are at 10x increased magnification.

Fig. 3

A and C, mice treated with vehicle only. B and D, mice treated with sunitinib starting at 16 wk after adeno-Cre activation of mutations. Mice in A and C were sacrificed for histologic examination at 18 wk. E, a sunitinib-treated mouse censored at 52 wk (inset is x8 magnification). F, Kaplan-Meier survival curve of mice treated with sunitinib or placebo. n indicates the number of mice in each group used for analysis.

Fig. 4

A and C, mice treated with vehicle only. B and D, mice treated with sunitinib starting at 4 wk after adeno-Cre activation of mutations. E, a representative mouse treated with sunitinib starting at 2 wk after adeno-Cre activation of mutations. Mice were sacrificed for histologic examination at the time points indicated. Kaplan-Meier survival curves of mice treated with sunitinib at 4 wk (F) or 2 wk (G) are shown below. n indicates the number of mice in each group used for analysis.