ATP-binding cassette protein responsible for cytotoxin resistance

Abstract

This invention provides for a novel ATP-binding cassette protein which is responsible for cytotoxin resistance. The invention also provides for methods of expressing the protein and assays for identification of inhibitors of the protein.

1 - 2 . (canceled)  
     
     
         3 . A eukaryote cell genetically altered to overexpress an ATP-binding cassette protein having the following properties: 
 i. conferring mitoxantrone resistance on S1-M1-80 human colon carcinoma cells when expressed in the cells; and,    ii. specifically binding to polyclonal antibodies which specifically bind to a member of the group of proteins depicted in Seq. ID. No. 2 or ID. No. 4.    
     
     
         4 . A cell of  claim 3 , wherein the cell is genetically altered by transformation of the cell with an exogenous DNA comprising an expression cassette encoding the ATP-binding cassette protein.  
     
     
         5 . A cell of  claim 4 , wherein the expression cassette comprises a heterologous promoter operatively linked to the DNA encoding the ATP-binding cassette protein.  
     
     
         6 . A cell of  claim 3 , wherein the cell has an endogenous copy of the ATP-binding cassette protein and the genetic alteration comprises insertion of DNA which can serve as an enhancing element or as a second promoter where the insertion is upstream of the endogenous promoter operatively linked to the ATP-binding cassette protein and where the inserted DNA increases the basal expression levels of ATP-binding cassette protein.  
     
     
         7 . A DNA encoding a ATP-binding cassette protein wherein the protein is characterized by having the following properties: 
 i. conferring mitoxantrone resistance on S1-M1-80 human colon carcinoma cells when expressed in the cells; and,    ii. specifically binding to polyclonal antibodies which specifically bind to a member of the group of proteins consisting of those depicted in Seq. ID. No. 2 or ID. No. 4.    
     
     
         8 . The DNA of  claim 7 , wherein the encoded protein has 95% identity to the amino acids depicted in Seq. ID. No. 2 or ID. No. 4.  
     
     
         9 . The DNA of  claim 7 , wherein the DNA encoding the protein has a sequence identical to that depicted in Seq. ID. No. 1 or No. 3.  
     
     
         10 . A process for over expressing ATP-binding cassette protein in a cell comprising a first step of either: 
 i. transforming the cell with an expression cassette which directs the expression of ATP-binding cassette protein; or,    ii. selecting a cell having an endogenous copy of the ATP-binding cassette protein, and transforming the cell with DNA which can serve as an enhancing element or as a second promoter where the insertion is upstream of the endogenous promoter operatively linked to the ATP-binding cassette protein and where the inserted DNA increases the basal expression levels of ATP-binding cassette protein; and a second step of,    culturing the transformed cell under conditions where the levels of ATP-binding cassette protein are increased above the basal levels of the non-transformed cells with the proviso that the ATP-binding cassette protein has the following properties:    a. confers mitoxantrone resistance on S1-M1-80 human colon carcinoma cells when expressed in the cells; and,    b. specifically binds to polyclonal antibodies which specifically bind to a member of the group of proteins depicted in Seq. ID. No. 2 or ID. No. 4.    
     
     
         11 . The process of  claim 10 , wherein the ATP-binding cassette protein has 95% homology to the amino acids depicted in Seq. ID. No. 2 or ID. No. 4.  
     
     
         12 . The process of  claim 10 , wherein the protein has the amino acids depicted in Seq. ID. No. 2 or ID. No. 4.  
     
     
         13 - 20 . (canceled)