A METHIONINASE FOR METHIONINE-DEPENDENT CHEMOTHERAPY

NEW APPROACHES ARE NECESSARY TO IMPROVE CHEMOTHERAPY OF SOLID TUMORS. FOR THIS PURPOSE, ANTICANCER, INC. HAS TAKEN ADVANTAGE OF THE CANCER-SPECIFIC METABOLIC DEFECT OF METHIONINE DEPENDENCE, WHICH CAUSES MANY TYPES OF CANCER CELLS TO REVERSIBLY ARREST LATE IN THE S/G2 PHASE OF THE CELL CYCLE IN MEDIUM WHERE METHIONINE (MET) HAS BEEN REPLACED BY HOMOCYSTEINE (HCY) (MET-HCY+ MEDIUM). THIS APPROACH HAS BEEN TERMED "METHIONINE-DEPENDENT CHEMOTHERAPY". TO BRING METHIONINE-DEPENDENT CHEMOTHERAPY CLOSER TO CLINICAL TRIALS, ANTICANCER, INC. PROPOSES TO ISOLATE A METHIONINASE THAT, UPON ADMINISTRATION TO THE ANIMAL OR PATIENT, WILL ALLOW THE MODULATION OF CIRCULATING LEVELS OF METHIONINE. THE BACTERIA ALCALIGENES FAECALIS AND PSEUDOMONAS PSEUDOALCALIGENES, WHICH CONTAIN A METHIONINASE THAT APPARENTLY DOES NOT CLEAVE HOMOCYSTEINE, HAVE BEEN IDENTIFIED. STATE-OF-THE-ART GENETIC SELECTION AND PROTEIN PURIFICATION PROCEDURES WILL BE USED TO ISOLATE A METHIONINASE WITH A LOW KM, A LONG HALF-LIFE IN THE CIRCULATION, AND A LOW TOXICITY FOR THE EXPERIMENTAL ANIMAL OR HUMAN PATIENT. THE METHIONINE-CLEAVING PROPERTIES, HALF-LIFE, AND TOXICITY OF THE ENZYME WILL BE TESTED IN RATS. PURIFICATION AND CHARACTERIZATION OF A DESIRABLE ENZYME IN PHASE I WILL LEAD TO CLONING THE METHIONINASE GENEIN PHASE II.