Abstract A1: The zinc-finger E-box-binding transcriptional repressor Snail promotes tumor progression and angiogenesis in non-small cell lung cancer.

A1

The zinc-finger E-box-binding transcriptional repressor Snail has been implicated in tumor progression of several malignancies. Best known as a transcriptional repressor of the adherens junction component E-cadherin, Snail has predominantly been associated with the epithelial-mesenchymal transition (EMT), invasion, and metastasis. However, the role of Snail in non-small cell lung cancer (NSCLC) is not yet defined. Immunohistochemistry of human lung adenocarcinoma and squamous cell carcinoma sections revealed specific nuclear staining of tumor cells in all patient samples. A human lung adenocarcinoma cell line H441 was stably transduced with a Snail expressing retroviral vector. Western analysis verified up-regulation of Snail and down-regulation of E-cadherin in the Snail over-expressing cells (H441-Snail) as compared to vector control cells (H441-V). In three-dimensional spheroid culture, H441V cells grew into large, tight spheroids while H441-Snail cells were markedly discohesive, reflecting a Snail-mediated phenotypic change consistent with EMT. To examine the effects of Snail over-expression in vivo, severe combined immunodeficiency (SCID) mice were injected subcutaneously with either H441-Snail cells or with H441-V cells. Mice were sacrificed 6 weeks later. The primary tumor burden in mice bearing H441-Snail tumors was five fold greater than the primary tumor burden of mice bearing H441-V tumors (p<0.005). To evaluate the incidence of metastases, these cell lines were tested in an orthotopic model. H441-V and H441-Snail cells were transthoracically injected into the left lung of SCID mice. Organs were then harvested and analyzed by flow cytometry gated on the human marker, CD49b. The incidence of metastases to the right lung, liver, bone marrow, and adrenal glands were significantly increased in the mice bearing H441-Snail tumors (p<0.05). Because H441-Snail tumors appeared grossly more hemorrhagic as compared to H441-V tumors at the time of harvest, primary tumors were homogenized and analyzed by ELISA for levels of two angiogenic factors known to play a role in NSCLC tumor angiogenesis: CXCL8 and CXCL5. H441-Snail tumors were associated with increased levels of CXCL8 (p<0.05) and CXCL5 (p<0.05) as compared to H441-V tumors. Based on these results, SCID mice injected with H441-Snail cells were treated with a CXCR2 (CXCL8 and CXCL5 receptor) blocking antibody. These mice exhibited reduced tumor burden and metastases as compared to mice bearing H441-Snail tumors that were treated with a control antibody. In summary, Snail contributes to tumor progression in NSCLC by inducing tumor angiogenesis, as evidenced by elevated levels of angiogenic factors (CXCL8 and CXCL5) and the reversal of increased tumor burden and metastases with CXCR2 blockade.

Citation Information: Cancer Prev Res 2008;1(7 Suppl):A1.