Sulfonamide compound or salt thereof

A method of treating tumor comprising administering an effective amount of a compound represented by the following formula (I) or a salt thereof to a subject in need thereof:

• wherein X1 represents an oxygen atom or a sulfur atom;
• X2 and X3 represent oxygen atoms;
• X2 represents an oxygen atom, and X3 represents —NH—;
• or X2 represents —NH—, and X3 represents an oxygen atom;
• X4 represents a hydrogen atom or a C1-C6 alkyl group;
• R1 represents —C(R11)(R12)- or —C(═CH2)—;
• R11 and R12 are the same or different and represent a hydrogen atom, a halogen atom, or a hydroxy group, or a C1-C6 alkyl group, alternatively may be taken together with the carbon atoms to which R11 and R12 are attached to form a saturated hydrocarbon ring having 3 to 8 carbon atoms;
• R2 represents a C6-C14 aromatic hydrocarbon group or a 9 or 10 membered fully unsaturated heterocyclic group,
• wherein R2 may have substituents, and when R2 has two substituents on carbon atoms which are adjacent to each other on the aromatic hydrocarbon ring, the substituents may be fused together with carbon atoms to which the substituents bind to form a saturated or partially unsaturated 4-8 membered hydrocarbon ring or heterocyclic ring, either of which may have substituents,
• R3 represents a C6-C14 aromatic hydrocarbon group or a 5-10 membered fully unsaturated heterocyclic group,
• wherein R3 may have substituents, and when R3 has two substituents on the carbon atoms which are adjacent to each other on the aromatic hydrocarbon ring, the substituents may be fused together with carbon atoms to which the substituents bind to form a saturated or partially unsaturated 4-8 membered hydrocarbon ring or heterocyclic ring, either of which may have substituents;
• and
• R4 represents a hydrogen atom or a C1-C6 alkyl group;
• with the proviso that X1 is an oxygen atom when X2 represents an oxygen atom, X3 represents —NH—, X4 represents a hydrogen atom, R1 represents —CH2—, R2 represents a phenyl group, R3 represents 4-methylphenyl group, and R4 represents a hydrogen atom,
• wherein the tumor is selected from the group consisting of head and neck cancer, gastrointestinal cancer, liver cancer, biliary tract cancer, pancreatic cancer, colorectal cancer, lung cancer, breast cancer, genital cancer, ovarian cancer, uterine cancer, urinary cancer, hematopoietic tumors, bone and soft tissue tumors, skin cancer, and brain tumor.