A synthetic alkylating agent chemically related to the nitrogen mustards with antineoplastic and immunosuppressive activities; used to treat cancers and autoimmune diseases.Chemotherapeutic Agents Approved(In Vitro):Cyclophosphamide induces outer membrane blebbing, leads to DNA fragmentation, as revealed by TUNEL staining of free 3'-OH DNA ends, and induces cleavage of the caspase 3 and caspase 7 substrate PARP in 9L/P450 cells. Bcl-2 expression fully blocks the activation of both initiator caspases as well as the effector caspase 3 in cells treated with activated Cyclophosphamide. Bcl-2 inhibits the cytotoxic effects but not the cytostatic effects of activated Cyclophosphamide. Cyclophosphamide inhibits the AChE reversibly with an IC50 of 511 μM. Carbon tetrachloride does not affect the direct cytotoxicity of cyclophosphamide or 4-hydroxycyclophosphamide to cells in culture.(In Vivo):Cyclophosphamide (injected i.p.;2mg/mouse in 0.1 mL PBS, in C3H mice bearing SW1 tumors) increases the percentage of cells that stained for CD3, CD4 or CD8 in both spleens and tumors.