NOS2 and metastatic melanoma: As myeloid cells are known to have an important impact on establishment of metastatic tumors (18), mice with a loss of function of the NOS2 gene in myeloid cells (using NOS2fl/fl and NOS2fl/fl LysMCre+strain mice) were injected intravenously with OVA expressing B16-F10 cells, a metastatic melanoma cell line.