The invention is directed to a compound that binds to a BCL6 lateral groove and prevents binding of a corepressor to the lateral groove. The present invention is further directed to methods for blocking corepressor binding to a BCL6 lateral groove, methods for inhibiting BCL6 repression in a mammalian cell, and methods for treating a mammal with cancer, wherein the cancer requires BCL6 repression. The present invention is further directed to polypeptides comprising a portion of the corepressor binding site for BCL6 and related polynucleotides and vectors.
