Method for suppressing tumorigenicity of stem cells

A method for suppressing tumorigenicity of stem cells of a mammalian subject, which comprises contacting said stem cell with an effective amount of the fatty acid derivative represented by the formula (I):

• wherein L, M and N are hydrogen, hydroxy, halogen, lower alkyl, hydroxy(lower)alkyl, lower alkanoyloxy or oxo, wherein the five-membered ring may have at least one double bond;
• A is —CH3, or —CH2OH, —COCH2OH, —COOH or a functional derivative thereof;
• B is single bond, —CH2—CH2—, —CH═CH—, —CH2—CH2—CH2—, —CH═CH—CH2—, —CH2—CH═CH—, —C≡C—CH2— or —CH2—C≡C—;
• Z is
• or single bond
• wherein R4 and R5 are hydrogen, hydroxy, halogen, lower alkyl, lower alkoxy or hydroxy(lower)alkyl, wherein R4 and R5 are not hydroxy and lower alkoxy at the same time;
• Z1 and Z2 are oxygen, nitrogen or sulfur;
• R6 and R7 are optionally substituted lower alkyl, which is optionally linked together to form lower alkylene;
• R1 is a saturated or unsaturated bivalent lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, lower alkyl, hydroxy, oxo, aryl or heterocyclic group, and at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur;
• and
• Ra is a saturated or unsaturated lower or medium aliphatic hydrocarbon residue, which is unsubstituted or substituted with halogen, oxo, hydroxy, lower alkyl, lower alkoxy, lower alkanoyloxy, cyclo(lower)alkyl, cyclo(lower)alkyloxy, aryl, aryloxy, heterocyclic group or hetrocyclic-oxy group;
• lower alkoxy;
• lower alkanoyloxy;
• cyclo(lower)alkyl;
• cyclo(lower)alkyloxy;
• aryl;
• aryloxy;
• heterocyclic group;
• heterocyclic-oxy group, and at least one of carbon atom in the aliphatic hydrocarbon is optionally substituted by oxygen, nitrogen or sulfur.