DNA (cyclophosphamide-induced interstrand and intrastrand crosslinks at guanine N-7 positions)

The provided “target name” describes a pharmacologic mechanism rather than a discrete molecular target: cyclophosphamide is a prodrug alkylating agent whose active metabolite, phosphoramide mustard, forms covalent adducts with DNA, primarily at guanine N-7, creating interstrand and intrastrand crosslinks that impede DNA strand separation, block replication and transcription, and induce apoptosis; specific interstrand adducts such as G–NOR–G are detectable in patients and correlate with pharmacodynamic action, while acrolein, another metabolite, contributes to DNA single-strand breaks and urotoxicity; because the “target” is bulk DNA lesions rather than a single protein receptor or enzyme, this entry is not a conventional therapeutic target entity but a mechanistic endpoint of alkylating chemotherapy.[1][2][5][4][7] Notes on correctness and classification: - The string “Cyclophosphamide target - DNA crosslinking/alkylation” conflates a drug with its mechanism; there is no single receptor/protein named this way, so this should be flagged as not a proper standalone target entity and corrected to the underlying substrate “DNA (guanine N-7) crosslinking by phosphoramide mustard).”[2][4][1] - Mechanistic details: cyclophosphamide requires CYP-mediated activation (notably CYP2B6 among others) to 4-hydroxycyclophosphamide/aldophosphamide, then phosphoramide mustard causes DNA crosslinks; interstrand crosslinks (5–10% of adducts) are highly cytotoxic; acrolein contributes to single-strand breaks and bladder toxicity; tissues with high ALDH are relatively protected by detoxifying aldophosphamide.[1][2][5][7] Evidence and specifics: - Cyclophosphamide’s cytotoxic effect is mainly due to cross-linking of DNA (and RNA) via phosphoramide mustard; interstrand crosslinks are most physiologically relevant for cytotoxicity.[4][1] - Crosslink sites: predominantly guanine N-7; adduct distribution includes phosphotriester monoadducts, N-7-guanine monoadducts, and N-7-guanine–N-7-guanine interstrand crosslinks (e.g., G–NOR–G).[1] - Additional lesions: DNA–protein crosslinks and single-strand breaks; acrolein induces single-strand breaks and contributes to cytotoxicity and hemorrhagic cystitis.[5][4] - Immunologic context: ALDH-rich cells (e.g., hematopoietic stem cells) are relatively protected; elimination of regulatory T cells and other immunomodulatory effects are described for the drug but are downstream of the DNA damage mechanism.[2] - Safety profile includes early-onset cardiotoxicity at high cumulative doses, major myelosuppression, and hemorrhagic cystitis.[4][7]

Other names

DNA crosslink adducts (G–NOR–G interstrand crosslink)DNA alkylation (guanine N-7 adducts)DNA interstrand crosslinksDNA intrastrand crosslinksDNA–protein crosslinks

DNA alkylation at guanine N-7 leading to interstrand and intrastrand DNA crosslinks that block DNA replication and trigger apoptosis; Formation of specific interstrand crosslink adducts (e.g., G–NOR–G) via phosphoramide mustard; Additional DNA lesions including DNA–protein crosslinks; acrolein-associated single-strand breaks