ABSTRACT
PURPOSE: Lung cancer is a major cause of cancer death, and its incidence is increasing in the world. Conventional therapies remain less effective for metastases of lung cancer, leading to poor prognosis of this disorder. The present study investigates pathological roles of RhoC in metastasis of lung cancer using a clinically relevant mouse model of lung cancer. EXPERIMENTAL DESIGN: RhoA, RhoC, dominant-negative Rho (dnRho) or green fluorescent protein gene was retrovirally transduced to murine lung cancer cells. For in vivo study, these transduced cells were intrapulmonary inoculated in syngeneic mice, and subsequently, growth and metastasis were analyzed. Migration and invasion activities were further investigated by in vitro chemotaxic chamber assays. Expression levels and activities of certain matrix metalloproteinases (MMPs) were explored by reverse transcription-PCR and gelatin zymography. RESULTS: Metastasis of lung cancer in the animal model, as well as in vitro migration and invasion, were significantly enhanced or inhibited by overexpression of RhoC or dnRho, respectively, without affecting the growth of primary tumors. Expression levels of certain MMPs and the activity of MMP-2 were significantly enhanced or suppressed by overexpression of RhoC or dnRho, respectively. CONCLUSION: RhoC plays a crucial role in metastasis of lung cancer. RhoC does not affect tumor growth but enhances the metastatic nature of lung cancer by not only stimulating cell motility but also up-regulating certain MMPs. Attenuation of RhoC activity may be a potential target in the development of a novel strategy for treating metastasis of lung cancer.
Subject(s)
Lung Neoplasms/pathology , Neoplasm Metastasis , rho GTP-Binding Proteins/physiology , Animals , Carcinoma, Lewis Lung , Cell Division , Cell Line, Tumor , Cell Movement , Female , Gelatin/chemistry , Genes, Dominant , Green Fluorescent Proteins , Immunohistochemistry , Luminescent Proteins/metabolism , Lung Neoplasms/metabolism , Lymph Nodes/pathology , Matrix Metalloproteinases/metabolism , Mice , Mice, Inbred C57BL , Neoplasm Invasiveness , Neoplasm Transplantation , Prognosis , RNA, Messenger/metabolism , Retroviridae/genetics , Reverse Transcriptase Polymerase Chain Reaction , Time Factors , Up-Regulation , ras Proteins , rho GTP-Binding Proteins/metabolism , rhoC GTP-Binding ProteinABSTRACT
Lindera strychifolia, a scandent shrub Lauraceous medicinal plant, has been used in Chinese traditional medicine as a palliative and an anti-spasmodic. It also shows cytotoxic effects against several tumor cell lines and inhibits marcromolecule biosynthesis. This study investigated the anti-tumor effects of L. strychifolia extract against lung cancer cells using in vitro and in vivo models. Two human lung cancer cell lines A549 (adenocarcinoma) and SBC-3 (small cell carcinoma), and a non-tumor cell line 3T3-L1 (mice fibroblasts) were subjected to L. strychifolia extract treatment. On lung cancer cells, L. strychifolia induced cell growth inhibition in a dose-dependent manner. Conversely, the extract did not show any significant cytotoxic effect on 3T3-L1 cells. Therefore, the extract is specific for tumor cells. Tumor cells treated with L. strychifolia extract showed typical morphological appearance of apoptosis including nuclei fragmentation and cell condensation. The in vivo effects of L. strychifolia extract were investigated in C57BL/6 mice transplanted with Lewis lung cancer (LL-2) cells, and in BALB/c nude mice transplanted with A549 or SBC-3 human lung cancer cells. Oral administration of L. strychifolia extract prolonged survival time and inhibited tumor growth in a dose-dependent manner by inducing apoptosis in the LL-2 cell mice model. Furthermore, in A549 or SBC-3 cell nude mice models, oral administration of L. strychifolia extract also significantly inhibited tumor growth at the 5.0 mg/ml concentration. These findings suggested that the components of L. strychifolia have anticancer activity and may contribute to clinical applications in the prevention and treatment of lung cancer.