Search

Small cell lung cancer (SCLC) is a severe malignancy associated with early and widespread metastasis. To study SCLC metastasis, we previously developed an orthotopic transplantation model using the human SCLC cell line DMS273. In the model, metastatic foci were found in distant tissues such as bone and the adrenal gland, similarly as observed in patients with SCLC. In this study, we evaluated the differentially expressed genes between orthotopic and metastatic tumors in the model. We isolated tumor cells from orthotopic and metastatic sites, and the tumor cell RNA was analyzed using DNA microarray analysis. We found that 19 genes in metastatic tumors were upregulated by more than 4-fold compared with their expression in orthotopic tumors. One of these genes encodes a transmembrane protein, interferon (IFN)-induced transmembrane protein 1 (IFITM1), and immunohistochemical analysis confirmed the higher expression of the protein in metastatic sites than in orthotopic sites. IFITM1 was also detected in some SCLC cell lines and lung tumors from patients with SCLC. The overexpression of IFITM1 in DMS273 cells increased their metastatic formation in the orthotopic model and in an experimental metastasis model. Conversely, the silencing of IFITM1 suppressed metastatic formation by DMS273 cells. We also found that IFITM1 overexpression promoted the metastatic formation of NCI-H69 human SCLC cells. These results demonstrate that IFITM1 promotes distant metastasis in xenograft models of human SCLC.

Small cell lung cancer (SCLC) is a severe malignancy with early and widespread metastasis, and novel therapeutic drugs are needed. To identify cytotoxic natural compounds against SCLC, we screened libraries of microbial fermentation broths using several lung cancer cell lines. We found that the actinomycete strain MG372-hF19 produces a compound that has not been isolated from natural sources but previously chemically synthesized, 6-chloro-1H-indole-3-carboxaldehyde (1), and an entirely new compound, named 6-deoxy-α-L-talopyranose 1-(6-chloro-1H-indole-3-carboxylate) (2), together with leptomycins. The molecular formulas of the compounds were established as C9H6ClNO and C15H16ClNO6, respectively, via high-resolution electrospray ionization mass spectrometry, and their structures were determined using detailed NMR. Absolute configurational analysis of the sugar unit of compound 2 revealed that the compound incorporates the rare deoxyhexose 6-deoxy-α-L-talopyranose. Both compounds exhibited weak growth-inhibiting activities against human lung cancer cell lines.

Small-cell lung cancer (SCLC) is an aggressive cancer with high metastatic ability and novel strategies against the metastasis are urgently needed to improve SCLC treatment. However, the mechanism of metastasis of SCLC remains largely to be elucidated. For further studies of SCLC metastasis, we developed a new orthotopic transplantation model in mice. We established a GFP-labeled subline from the human SCLC cell line DMS273 and transplanted them orthotopically into the lung of nude mice with Matrigel. The GFP-labeled cells showed significant metastatic activity and formed metastatic foci in distant tissues such as bone, kidney, and brain, as observed in SCLC patients. From a bone metastasis focus of the mouse, we isolated another subline, termed G3H, with enhanced metastatic potential and higher hepatocyte growth factor (HGF) expression than the parental line. Further studies indicated that the HGF/MET signaling pathway was involved in in vitro motility and invasion activities of the G3H cells and treatments with MET inhibitors decreased formation of distant metastases in our orthotopic model using G3H cells. These data indicated that our model mimics the clinical aspect of SCLC such as metastatic tropism and autocrine of HGF/MET signaling. Compared with other orthotopic SCLC models, our model has a superior ability to form distant metastases. Therefore, our model will provide a valuable tool for the study of SCLC metastasis.