Contribution of neuropilin 1 to increased motility in radiation‐surviving cells

Abstract

Radiotherapy is an effective approach for the treatment of various types of cancer. However, it has been reported that the malignant capacity of tumor cells is elevated in tumors that survive radiotherapy. In a previous report, we prepared radiation‐surviving tumor cells (IR cells) using the human non‐small cell lung cancer cell line H1299. In preliminary experiments, we found that expression of neuropilin 1 was up‐regulated in IR cells. Here, we investigated the contribution of neuropilin 1 to changes in cell characteristics in these radiation‐surviving cells. Expression levels of neuropilin 1 mRNA were about 1.4‐fold up‐regulated in IR cells, as compared with parental cells. Cell motility was further increased in IR cells than parental cells on cell migration assay, although there were no differences in angiogenic activity on tube formation assay. Furthermore, up‐regulation of cell motility in IR cells was suppressed by pre‐treatment with anti‐neuropilin 1 antibody. Neuropilin 1 was observed at the endosome‐like vesicles in IR cells, on which early endosome autoantigen 1(EEA1), a marker for endosome, was not co‐localized on immunofluorescence. Although further studies are necessary in order to identify other molecules associated with neuropilin 1, neuropilin 1 may be important in controlling the up‐regulation of cell motility in radiation‐surviving tumor cells.