The aim of our studies of alkylating agent pharmacology is to define, at the molecular level, chemical structures and mechanisms which produce reduced hematologic toxicity while preserving antineoplastic activity. We are correlating alkylating agent antitumor activity and cytotoxicity with site-specific binding to chromatin, and we are attempting to selectively increase toxicity for tumor tissue by addition of a sugar moiety to the alkylating group. From our recent work with the nitrosoureas and C6-glucose nitrogen mustard, we hypothesize that addition of the sugar moiety increases alkylation of tumor cell DNA and template-active regions of tumor cell chromatin, while concomitantly decreasing alkylation of bone marrow DNA and template-active regions of bone marrow chromatin. We have now synthesized C6-galactose nitrogen mustard, and demonstrated both its antitumor activity against a spectrum of murine tumors, and its reduced hematologic toxicity in the mouse and dog, as confirmation of clinical potential. Specific objectives for the grant include: 1. Analysis of nitrogen mustard alkylating agent binding and repair in template active regions of chromatin of murine P388 and bone marrow cells, sensitive and HN2/-resistant Raji/Burkitt's lymphoma cells, and the human bone marrow stem cell KG-la. We will compare the less myelotoxic C6-galactose and C6-glucose mustard compounds with the myelosuppressive mustards HN2 and L-PAM, to determine the importance of alkylation of transcriptionally-active chromatin for the antitumor activity and cytotoxicity of this class of alkylating agent. 2. Determine the importance of alkylating agent binding and repair in nucleosomal core versus internucleosomal regions of chromatin for cytotoxicity in these same cell lines. 3. Determine comparative cross-linking by the less myelotoxic glucose and galactose nitrogen mustards in murine P388 and bone marrow cells, in comparative studies with HN2 and L-PAM. 4. Determine the toxicology and phamacologic disposition of C6- galactose mustard in mice and dogs, to determine target organ toxicity since bone marrow toxicity is not a major contributing factor for lethality at the LD10 dose in the mouse of dog. 5. Synthesize and evaluate sugar-containing analogs of mitomycin C. Our initial studies with one analog demonstrate sugar-moiety mediated bone marrow sparing in mice.
