The transcriptional modulator BCL6 as a molecular target for breast cancer therapy.

Inappropriate expression or activation of transcription factors can drive patterns of gene expression, leading to the malignant behavior of breast cancer cells. We have found that the transcriptional repressor BCL6 is highly expressed in breast cancer cell lines, and its locus is amplified in about half of primary breast cancers. To understand how BCL6 regulates gene expression in breast cancer cells, we used chromatin immunoprecipitation followed by deep sequencing to identify the BCL6 binding sites on a genomic scale. This revealed that BCL6 regulates a unique cohort of genes in breast cancer cell lines compared with B-cell lymphomas. Furthermore, BCL6 expression promotes the survival of breast cancer cells, and targeting BCL6 with a peptidomimetic inhibitor leads to apoptosis of these cells. Finally, combining a BCL6 inhibitor and a signal transducer and activator of transcription3 inhibitor provided enhanced cell killing in triple-negative breast cancer cell lines, suggesting that combination therapy may be particularly useful. Thus, targeting BCL6 alone or in conjunction with other signaling pathways may be a useful therapeutic strategy for treating breast cancer.

A different ontogenesis for chronic lymphocytic leukemia cases carrying stereotyped antigen receptors: molecular and computational evidence.

Chronic lymphocytic leukemia (CLL) is uniquely characterized by the existence of subsets of cases with quasi-identical, 'stereotyped' B-cell receptors (BCRs). Herein we investigate this stereotypy in 2662 patients with CLL, the largest series yet, using purpose-built bioinformatics methods based on sequence pattern discovery. Besides improving the identification of 'stereotyped' cases, we demonstrate that CLL actually consists of two different categories, based on the BCR repertoire, with important biological and ontogenetic differences. The first ( approximately 30% of cases) shows a very restricted repertoire and is characterized by BCR stereotypy (clustered cases), whereas the second includes cases with heterogeneous BCRs (nonclustered cases). Eleven major CLL clusters were identified with antigen-binding sites defined by just a few critically positioned residues, regardless of the actual immunoglobulin (IG) variable gene used. This situation is closely reminiscent of the receptors expressed by cells participating in innate immune responses. On these grounds, we argue that whereas CLL cases with heterogeneous BCRs likely derive from the conventional B-cell pool, cases with stereotyped BCRs could derive from progenitor cells evolutionarily adapted to particular antigenic challenges, perhaps intermediate between a true innate immune system and the conventional adaptive B-cell immune system, functionally similar to what has been suggested previously for mouse B1 cells.