An object of the present invention is to provide amethod of efficiently constructing a gene delivery carrierhaving a favorable activity and expression efficiency of aprotein expressed by a gene introduced by transformation.Moreover, an object of the present invention is to providea pharmaceutical composition comprising a gene deliverycarrier constructed by the construction method and atherapeutic agent for solid tumor comprising the resistantbacterium. The objects of the present invention have beenattained by a gene delivery carrier consisting of ananaerobic microorganism capable of growing in a tumortissue in an anaerobic environment and capable ofexpressing (A) a protein having an antitumor activity or(B) a protein having an activity of converting anantitumor substance precursor to an antitumor substance,wherein DNA encoding the protein of interest is allowed tofurther comprise, on the 5'-terminal side thereof, a DNAfragment comprising a nucleotide sequence encoding apeptide consisting of an amino acid sequence from the 1stto at least 4th amino acids at the N-terminus of ahistone-like DNA-binding protein.
