Let-7 microrna and mimetics thereof as therapeutics for cancer

Abstract

The present invention relates to methods to treat or prevent cancers in a subject, in particular the present invention relates to a method of treating and/or preventing cancer comprising targeting cancer stem cells by administering miRNAs which have reduced expression or are lacking in the cancer stem cells. In some embodiments, the miRNAs that are reduced or lacking in cancer stem cells are let-7 miRNAs. In alternative embodiments, the present invention relates to a method of treating and/or preventing cancer comprising targeting cancer stem cells by administering miRNAs which have increased expression levels in the cancer stem cells. Another aspect of the present invention relates to methods to enrich for a cancer stem cell population. Another aspect of the present invention relates to methods to identify miRNAs which contribute to the self-renewal capacity of cancer stem cells.

1 . A method of treating or preventing a cancer in a subject wherein the cancer comprises a cancer stem cell, the method comprising administering to the subject a pharmaceutical composition comprising an effective amount of at least one let-7 miRNA, or an agent that increases the expression of a let-7 miRNA in a cancer stem cell, wherein the let-7 miRNA binds to and inhibits an RNA transcript comprising a let-7 target sequence which is expressed in a cancer stem cell. 
     
     
         2 . The method of  claim 1 , wherein the let-7 target sequence comprises SEQ ID NO: 9 or SEQ ID NO: 10 or SEQ ID NO:11 or a homologue thereof. 
     
     
         3 .- 5 . (canceled) 
     
     
         6 . The method of  claim 1 , wherein the let-7 family member is selected from the group consisting of let-7a, let-7a1, let-7b, let-7c, let-7d, let-7e and let-7f and homologues thereof that are effective in gene silencing. 
     
     
         7 . (canceled) 
     
     
         8 . The method of  claim 1 , wherein the miRNA is a pri-miRNA, pre-miRNA, mature miRNA or a fragment or variant thereof effective in gene silencing. 
     
     
         9 . The method of  claim 1 , wherein the let-7 miRNA comprises SEQ ID NO:1-8 or a fragment or homologue thereof effective in gene silencing. 
     
     
         10 .- 15 . (canceled) 
     
     
         16 . The method of  claim 1 , wherein the agent is selected from a group consisting of; a small molecule, protein, antibody, aptamer, ribozyme, nucleic acid or nucleic acid analogue. 
     
     
         17 . (canceled) 
     
     
         18 . (canceled) 
     
     
         19 . The method of  claim 1 , wherein the cancer is selected from at least one of the group consisting of a pre-cancer, malignant cancer, therapy resistant cancer, breast cancer. 
     
     
         20 .- 22 . (canceled) 
     
     
         23 . The method of  claim 1 , wherein let-7 miRNA further comprises a binding moiety and a targeting moiety, wherein the binding moiety binds let-7 miRNA to the targeting moiety. 
     
     
         24 . The method of  claim 23 , wherein the targeting moiety is a cell surface receptor ligand or binds to a cell surface antigen present on a cancer stem cell. 
     
     
         25 . The method of  claim 24 , wherein the cell surface receptor ligand is selected from a group consisting of CD133, CD44, mini-MUC; MUC-1; HER2/neu; HER2; mammoglobulin; labyrinthin; SCP-1; NY-ESO-1; SSX-2; N-terminal blocked soluble cytokeratin; 43 kD human cancer antigen; human tumor associated antigen (PRAT); human tumor associated antigen (TUAN); L6 antigen; carcinoembryonic antigen; CA15-3; oncoprotein 18/stathmin (Op18); human glandular kallikrein (hK2); NY—BR antigens, tumor protein D52, and prostate-specific antigen; and EEA, c-kit, ABC7, SCA1, CD24−, lin-, Oct4+ or combinations thereof. 
     
     
         26 . The method of  claim 23 , wherein the targeting moiety is selected from the group consisting of an antibody, a single chain antibody, a Fab portion of an antibody or a (Fab′)2 segment. 
     
     
         27 . The method of  claim 26 , wherein the antibody is an antibody to a cell surface antigen on a cancer stem cell. 
     
     
         28 . (canceled) 
     
     
         29 . The method of  claim 23 , wherein the binding moiety is a protein or a nucleic acid binding domain of a protein, and the binding moiety is fused to the carboxyl terminus of the targeting moiety. 
     
     
         30 . The method of  claim 23 , wherein the binding moiety is the protein protamine or nucleic acid binding fragment of protamine. 
     
     
         31 . The method of  claim 1 , further comprising administering to the subject one or more additional cancer therapies selected from the group consisting of surgery, chemotherapy, radiotherapy, thermotherapy, immunotherapy, hormone therapy and laser therapy. 
     
     
         32 .- 42 . (canceled) 
     
     
         43 . The method of  claim 1 , wherein the subject is a mammal or a human. 
     
     
         44 .- 99 . (canceled) 
     
     
         100 . A pharmaceutical composition comprising a let-7 miRNA, a binding moiety, a targeting moiety and a pharmaceutically acceptable carrier, wherein the let-7 miRNA binds to and inhibits an RNA transcript comprising a let-7 target sequence and wherein binding moiety binds to the let-7 miRNA and the targeting moiety, and wherein the targeting moiety targets a cancer stem cell. 
     
     
         101 . A pharmaceutical composition comprising an agent which increases the expression of let-7 miRNA in a cancer stem cell, and a pharmaceutically acceptable carrier, wherein the let-7 miRNA binds to and inhibits an RNA transcript comprising a let-7 target sequence. 
     
     
         102 . The pharmaceutical composition of  claim 100 , wherein the let-7 target sequence comprises SEQ ID NO:9 or SEQ ID NO: 10 or SEQ ID NO:11 or a homologue thereof effective in gene silencing. 
     
     
         103 .- 107 . (canceled) 
     
     
         108 . The pharmaceutical composition of  claim 101 , wherein the agent is selected from the group comprising a small molecule, nucleic acid, nucleic acid analogue, aptamer, ribosome, peptide, protein, antibody, or variants and fragments thereof. 
     
     
         109 . (canceled) 
     
     
         110 . The pharmaceutical composition of  claim 100  for the treatment or prevention of cancer in a subject, or a human subject. 
     
     
         111 . The pharmaceutical composition of  claim 110 , wherein the cancer is breast cancer. 
     
     
         112 . (canceled)