Anaerobic bacterium as a drug for cancer gene therapy

Abstract

The present invention provides a bacterium belonging to the genus Bifidobacterium, by which DNA coding for a protein having an antitumor activity or DNA coding for a protein having the activity of converting a precursor of an antitumor substance into the antitumor substance is delivered to tumor tissues specifically under anaerobic conditions thereby expressing the protein encoded by the DNA, as well as a pharmaceutical composition comprising said anaerobic bacterium.

What is claimed is:  
     
         1 . A method for delivering a gene in a system for delivering DNA specifically to tumor tissues under anaerobic conditions, wherein a bacterium belonging to the genus Bifidobacterium is used as a gene delivery vector and then the DNA delivered specifically to tumor tissues under anaerobic conditions is expressed in said tumor tissues.  
     
     
         2 . A method for delivering a gene in a system for delivering DNA specifically to tumor tissues under anaerobic conditions, wherein a bacterium belonging to the genus Bifidobacterium and having the DNA coding for a protein which has a higher activity than in its parent strain is used as a gene delivery vector and then the DNA delivered specifically to tumor tissues under anaerobic conditions is expressed in said tumor tissues.  
     
     
         3 . A method for delivering a gene in a system for delivering DNA specifically to tumor tissues under anaerobic conditions, wherein a bacterium belonging to the genus Bifidobacterium transformed with a recombinant DNA having said DNA is used as a gene delivery vector and the DNA delivered specifically to tumor tissues under anaerobic conditions is expressed in the tumor tissues.  
     
     
         4 . The method as claimed in any one of  claims 1  to  3 , wherein the DNA is selected from the group consisting of: 
 (a) DNA coding for a protein having an antitumor activity, and  
 (b) DNA coding for a protein having an activity of converting a precursor of an antitumor substance into the antitumor substance.  
 
     
     
         5 . The method as claimed in  claim 4 , wherein the protein having an antitumor activity is interleukin-2.  
     
     
         6 . The method as claimed in  claim 4 , wherein the precursor of an antitumor substance is selected from the group consisting of 5-fluorocytosine, 5-aziridino-2,4-dinitrobenzamide, ganciclovir, a glucuronic acid-conjugated antitumor substance and a lysine-conjugated antitumor substance.  
     
     
         7 . The method as claimed in  claim 4 , wherein the protein having the activity of converting a precursor of an antitumor substance into the antitumor substance is a protein selected from the group consisting of cytosine deaminase, nitroreductase, herpes simplex virus type 1 thymidine kinase and β-glucuronidase.  
     
     
         8 . The method as claimed in  claim 3 , wherein the recombinant DNA is an expression vector.  
     
     
         9 . The method as claimed in  claim 8 , wherein the expression vector has a promoter and a terminator functioning in a bacterium belonging to the genus Bifidobacterium.  
     
     
         10 . The method as claimed in  claim 9 , wherein the promoter and terminator are those involved in expressing a gene coding for histone-like DNA-binding protein (HU protein) derived from  Bifidobacterium longum.    
     
     
         11 . The method as claimed in  claim 9 , wherein the promoter and terminator are DNAs located at the 1- to 192-positions and at the 472- to 600-positions respectively in the nucleotide sequence set forth in SEQ ID NO: 1.  
     
     
         12 . The method as claimed in any one of  claims 1  to  11 , wherein the bacterium is  Bifidobacterium longum.    
     
     
         13 . The method as claimed in any one of  claims 1  to  4  or  6  to  12 , wherein the bacterium is  Bifidobacterium longum  105-A/pBLES100-S-eCD (FERM BP-7274).  
     
     
         14 . A method for expressing a gene coding for a protein having an antitumor activity in tissue tumors specifically, which comprises use of the bacterium as claimed in any one of  claims 1  to  5  or  8  to  12 .  
     
     
         15 . A method for expressing a gene coding for a protein having the activity of converting a precursor of an antitumor substance into the antitumor substance in tissue tumors specifically, which comprises use of the bacterium as claimed in any one of  claims 1  to  4  or  6  to  12 .  
     
     
         16 . A pharmaceutical composition comprising the bacterium as claimed in any one of  claims 1  to  13 .  
     
     
         17 . The pharmaceutical composition as claimed in  claim 16 , wherein the pharmaceutical composition comprises a combination of the bacterium as claimed in any one of  claims 1  to  4  or  6  to  13  and the precursor of an antitumor substance.  
     
     
         18 . The pharmaceutical composition as claimed in  claim 16 , wherein the pharmaceutical composition comprises the bacterium as claimed in any one of  claims 1  to  4  or  6  to  13  and the precursor of an antitumor substance.  
     
     
         19 . The pharmaceutical composition as claimed in any one of  claims 16  to  18 , wherein the bacterium is  Bifidobacterium longum.    
     
     
         20 . The pharmaceutical composition as claimed in any one of  claims 16  to  19 , wherein bacterium is  Bifidobacterium longum  105-A/pBLES100-S-eCD (FERM BP-7274).  
     
     
         21 . A bacterium belonging to the genus Bifidobacterium, which is used in the method as claimed in any one of  claims 1  to  13 .  
     
     
         22 .  Bifidobacterium longum  105-A/pBLES100-S-eCD (FERM BP-7274.  
     
     
         23 . DNA having the nucleotide sequence set forth in SEQ ID NO: 1.  
     
     
         24 . A method of treating a solid tumor, which comprises use of the method as claimed in any one of  claims 1  to  15 .  
     
     
         25 . A method of treating a solid tumor, which comprises administering the bacterium as claimed in any one of  claims 1  to  4  or  6  to  13  in combination with the precursor of an antitumor substance.  
     
     
         26 . An anaerobic bacterium belonging to the genus Bifidobacterium capable of expressing a gene coding for a protein having an antitumor activity in only cancer cells under substantially anaerobic conditions.  
     
     
         27 . An anaerobic bacterium belonging to the genus Bifidobacterium capable of expressing a gene coding for a protein having the activity of converting a precursor of an antitumor substance with low toxicity to humans and animals into an antitumor substance in only cancer cells under substantially anaerobic conditions.