TY  - JOUR
A1  - Voelcker, Georg
T1  - Enzyme catalyzed decomposition of 4-Hydroxycyclophosphamide
T2  - The open conference proceedings journal
N2  - According to general doctrine canceroselectivity of Cyclophosphamide is based on different activities of the 4-hydroxycyclophosphamide (OHCP) detoxifying cellular enzyme aldehyde dehydrogenase in tumor and normal cells. Aldehyde dehydrogenase converts the OHCP tautomere aldophosphamide (ALDO) to the non-cytotoxic carboxyphosphamide. Due to different activities of the detoxifying enzyme more cytotoxic phosporamide mustard (PAM) is spontaneously released from OHCP/ALDO in tumor cells. PAM unfolds its cytotoxic activity by forming intrastrand and interstrand DNA crosslinks. This hypothesis is supported by in vitro experiments which show inverse correlations of aldehyde dehydrogenase activity and sensitivity of tumor cells against activated congeners of cyclophosphamide like mafosfamide which hydrolyses within a few minutes to OHCP. In protein free rat serum ultrafiltrate however free OHCP and its coexisting tautomer ALDO are stable compounds. Its half-life in protein free rat serum ultrafiltrate (pH7, 37oC) is more than 20 h. Contrary to protein free ultrafiltrate in whole serum ALDO is enzymatically decomposed to PAM and 3-hydroxypropionaldehyde (HPA) within minutes. The decomposing enzyme was identified as 3´-5´ phosphodiesterase, the Michaelis constant was determined to be 10-3 M in human serum.
The experiments presented clearly demonstrate that ALDO is not only cleaved base catalyzed yielding acrolein and PAM but also cleaved enzymatically by serum phosphodiesterases yielding HPA and PAM. It is discussed that the reason of the high canceroselectivity of cyclophosphamide is not only due to enrichment of OHCP/ALDO in tumor cells due to less detoxification of ALDO in tumor cells than in normal cells. It is discussed that there is a good reason for an additional mechanism namely the amplification of apoptosis of PAM damaged cells by HPA.
A two step mechanism for the mechanism of action of OHCP/ALDO is discussed. During the first step, the DNA is damaged by alkylation by PAM. During the second step the cell containing damaged DNA is eliminated by apoptosis, supported by HPA.
KW  - 4-hydroxycyclophosphamide
KW  - Enzymatic decomposition
KW  - 3´-5´ phosphodiesterases
KW  - Phosphoramide mustard
KW  - 3-hydroxypropionaldehyde
Y1  - 2017
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/48672
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-486727
SN  - 2210-2892
N1  - Open-Access License: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
VL  - 8
SP  - 44
EP  - 51
PB  - Bentham Science Publ.
CY  - Beijing [u .a.]
ER  -