Compositions and methods for treating cancer

Abstract

Provided are nucleic acid constructs and systems which comprise (i) a first nucleic acid construct encoding a toxin operatively linked to a first promoter and at least one cancer-associated signaling responsive enhancer element; and (ii) a second nucleic acid construct encoding an anti-toxin operatively linked to a second promoter, the second promoter being stronger than the first promoter. Also provided are pharmaceutical compositions comprising same and methods of using same for treating cancer.

1 . A nucleic acid construct system comprising:
 (i) a first nucleic acid construct encoding a toxin operatively linked to a first promoter and at least one cancer-associated signaling responsive enhancer element;   (ii) a second nucleic acid construct encoding an anti-toxin operatively linked to a second promoter, said second promoter being stronger than said first promoter.   
     
     
         2 . The nucleic acid construct system of  claim 1 , wherein said first nucleic acid construct and said second nucleic acid construct are provided at substantially equal concentrations. 
     
     
         3 . The nucleic acid construct system of  claim 1 , wherein said toxin and antitoxin are a bacterial-derived toxin-antitoxin pair. 
     
     
         4 . The nucleic acid construct system of  claim 3 , wherein said toxin-antitoxin pair is a bacterial type II toxin-antitoxin pair. 
     
     
         5 . The nucleic acid construct system of  claim 4 , wherein said toxin-antitoxin pair is selected from: CcdB-CcdA, ParE-ParD, MazF-MazE, yafO-yafN, HicA-HicB, Kid-Kis, and Zeta-Epsilon. 
     
     
         6 . The nucleic acid construct system of  claim 1 , wherein said first promoter and said second promoter are both constitutive promoters. 
     
     
         7 . The nucleic acid construct system of  claim 1 , wherein said at least one cancer-associated signaling responsive enhancer element is a Ras responsive enhancer element. 
     
     
         8 . The nucleic acid construct system of  claim 7 , wherein said Ras responsive enhancer element is a K-Ras responsive enhancer element. 
     
     
         9 . The nucleic acid construct system of  claim 7 , wherein said Ras responsive enhancer element comprises at least one element selected from the group consisting of an Ets binding site, an Ap-1 binding site and a PY2 sequence. 
     
     
         10 . The nucleic acid construct system of  claim 1 , wherein said antitoxin is operatively linked to said second promoter and a p53 wild-type responsive element. 
     
     
         11 . The nucleic acid construct system of  claim 10 , wherein said p53 wild-type responsive element comprise 17 copies of a p53 wild type responsive element as set forth in SEQ ID NO: 15. 
     
     
         12 . The nucleic acid construct system of  claim 1 , wherein said second promoter comprises CMV and said first promoter comprises SV40. 
     
     
         13 . The nucleic acid construct system of  claim 1 , wherein said first nucleic acid construct, said second nucleic acid construct or both is adeno-virus based or is lenti-virus based. 
     
     
         14 . The nucleic acid construct system of  claim 1 , wherein said first nucleic acid construct further comprises a repressor of a bacterial repressor-operator system, said repressor being under a transcriptional regulation of said cancer-associated signaling responsive enhancer element, and wherein said second nucleic acid construct comprises an operator of said bacterial repressor-operator system, such that expression of said repressor inhibits expression of said antitoxin. 
     
     
         15 . The nucleic acid construct system of  claim 14 ,
 a. wherein said repressor comprises the Tetracycline repressor (Tet-R) sequence, and wherein said operator comprises the tetracycline operator sequence;   b. wherein said operator comprises at least two repeats of the sequence tetracycline operator sequence; or   c. both.   
     
     
         16 . The nucleic acid construct system of  claim 1 , wherein said first nucleic acid construct comprises four repeats of the PY2 sequence set forth by SEQ ID NO:2 being upstream and operably linked to the SV40 minimal promoter region set forth by SEQ ID NO:4, a toxin coding sequence being downstream of and transcriptionally regulated by said SV40 minimal promoter region, an IRES sequence set forth by SEQ ID NO:7 being downstream and operably linked to said toxin coding sequence, and a Tetracycline repressor set forth by SEQ ID NO: 8 being downstream of and operably linked to said IRES sequence. 
     
     
         17 . The nucleic acid construct system of  claim 1 , wherein said second nucleic acid construct comprises a CMV minimal promoter which comprises two repeats of a tetracycline operator as set forth by SEQ ID NO:9 and an antitoxin coding sequence being downstream of and operably linked to said CMV minimal promoter. 
     
     
         18 . A pharmaceutical composition comprising the nucleic acid construct system of  claim 1  and a pharmaceutically acceptable vehicle. 
     
     
         19 . A method of treating cancer in a patient in need thereof, said method comprising administering to said subject an effective amount of the pharmaceutical composition of  claim 18 , thereby treating said cancer patient. 
     
     
         20 . The method of  claim 19 , wherein said cancer comprises a tumor overexpressing Ras and said tumor cells are characterized by a hyperactive RAS pathway as compared to non-tumor cells of the same tissue.