Bioactivation of alkylating agents for cancer treatment
A rapid screening method for identifying acylfulvenes and acylfulvene analogs with improved chemotherapeutic properties has been developed. The mechanism of toxicity of irofulven, a potentially clinically useful member of the acylfulvene class, has been elucidated and provides guidance for design and testing of a new class of alkylating agents with structures related to irofulven. The role of alkenal/one oxidoreductase (AOR) is shown to be important in cancer cell susceptibility to this class of alkylating agent.
1. An in vitro method of assessing cancer cell toxicity of an acylfulvene candidate drug, wherein the cancer cell is selected from leukemia, non-small cell lung, colon, central nervous system, melanoma, ovarian, renal, prostate and breast cancer cells, and wherein the cancer cells expresses NADPH alkenal/one oxidoreductase (AOR), comprising: incubating the candidate drug with a medium chain reductase that reduces an α,β-unsaturated aldehyde/ketone fulvene at ring position 8,9 of the candidate drug, wherein the medium chain reductase is a polypeptide having the amino acid sequence of SEQ ID NO: 1, SEQ ID NO:3 or an amino acid sequence at least 95% identical thereto; determining a reduction rate for said candidate drug; and comparing said rate with a model substrate reduction rate; wherein a reduction rate for the candidate drug less than the reduction rate for the model substrate is predictive of increased cancer cell toxicity of the candidate acylfulvene drug compared with the model substrate, and wherein the model substrate is irofulvin.
2. The method of claim 1 wherein the medium chain reductase is encoded by a nucleic acid having the sequence of SEQ ID NO: 2, SEQ ID NO:4 or variants thereof that encode the polypeptides set forth as SEQ ID NO 1 or SEQ ID NO: 3.
3. The method of claim 1 , wherein the reduction rate is a maximum reduction rate (Vmax).
4. The method of claim 1 wherein the reduction rate is a specific activity rate.
5. The method of claim 3 , wherein the Vmax of the candidate acylfulvene drug has a Vmax equal to or less than the Vmax of irofulven.
6. The method of claim 1 further comprising measuring double bond stability toward reduction by incubating the candidate acylfulvene drug with a nucleophile.
7. The method of claim 6 , wherein the nucleophile is glutathione.
8. An in vitro method of assessing cancer cell toxicity of an acylfulvene candidate drug, wherein the cancer coil is in vitro and is selected from leukemia, non-small cell lung, colon, central nervous system, melanoma, ovarian, renal, prostate and breast cancer cells, and wherein the cancer cell expresses NADPH alkenal/one oxidoreductase (AOR), comprising: incubating the candidate drug with a medium chain reductase that reduces an α,β-unsaturated aldehyde/ketone fulvene at ring position 8,9 of the candidate drug, wherein the medium chain reductase is a polypeptide having the amino acid sequence of SEQ ID NO: 1, SEQ ID NO:3 or an amino acid sequence at least 95% identical thereto; determining a reduction rate for said candidate drug; and comparing said rate with a model substrate reduction rate; wherein a reduction rate for the candidate drug less than the reduction rate for the model substrate is predictive of increased cancer cell toxicity of the candidate acylfulvene drug compared with the model substrate, and wherein the model substrate is selected from illudin M, illudin S or irofulvin.
9. The method of claim 8 , wherein the reduction rate is a maximum reduction rate (Vmax).
10. The method of claim 9 , wherein the Vmax of the candidate acylfulvene drug has a Vmax equal to or less than the Vmax of irofulven.
11. The method of claim 9 , wherein the Vmax of the candidate acylfulvene drug has a Vmax of about one order of magnitude less than the Vmax of illudin M.
12. The method of claim 9 , wherein the Vmax of the candidate acylfulvene drug has a Vmax about two orders of magnitude less than the Vmax of illudin S.