Peripheral blood NK cells from breast cancer patients are tumor-induced composite subsets.

Human NK lymphocytes are involved in antitumor immunity. The therapeutic potential of this population against cancers has stimulated their study and led to the discovery of several NK cell subsets, each of which is endowed with different immunoregulatory functions. We have previously reported that NK cell functions are profoundly altered in advanced breast cancer patients. In this study, we show that these tumor-mediated alterations also variably affect NK cell subsets. We found that in addition to the known human CD56(dim)CD16(+), CD56(bright)CD16(-), and CD56(-)CD16(+) NK cell subsets, two additional subsets, namely the CD56(bright)CD16(+) and CD56(dim)CD16(-) subsets, were increased in the peripheral blood of patients with advanced invasive breast cancers. These subsets corresponded to the main two subsets found at the tumor site. The extensive phenotype of these subsets revealed an "à la carte" pattern of expression for the various NK receptors, functional molecules, adhesion molecules, and chemokine receptors, depending on the subset. We next compared these subsets to known NK cell populations endowed with specific phenotypic characteristics, but also with functional properties. Our data show that advanced breast cancer patients have an increased proportion of more immature and noncytotoxic NK cell subsets in their peripheral blood, which might account for at least part of the low cytotoxic functions observed in these patients. They reveal a major heterogeneity and plasticity of the NK cell compartment, which are both tightly linked to the microenvironment. The identification of NK cell subsets endowed with particular functional capabilities might help monitor residual antitumor NK cell-mediated responses in breast cancer patients.

Early lesions of follicular lymphoma: a genetic perspective.

The pathogenesis of follicular lymphoma is a multi-hit process progressing over many years through the accumulation of numerous genetic alterations. Besides the hallmark t(14;18), it is still unclear which other oncogenic hits contribute to the early steps of transformation and in which precursor stages these occur. To address this issue, we performed high-resolution comparative genomic hybridization microarrays on laser-capture micro-dissected cases of follicular lymphoma in situ (n=4), partial involvement by follicular lymphoma (n=4), and duodenal follicular lymphoma (n=4), assumed to represent, potentially, the earliest stages in the evolution of follicular lymphoma. Cases of reactive follicular hyperplasia (n=2), uninvolved areas from follicular lymphoma in situ lymph nodes, follicular lymphoma grade 1-2 (n=5) and follicular lymphoma grade 3A (n=5) were used as controls. Surprisingly, alterations involving several relevant (onco)genes were found in all entities, but at significantly lower proportions than in overt follicular lymphoma. While the number of alterations clearly assigns all these entities as precursors, the pattern of partial involvement by follicular lymphoma alterations was quantitatively and qualitatively closer to that of follicular lymphoma, indicating significant selective pressure in line with its faster rate of progression. Among the most notable alterations, we observed and validated deletions of 1p36 and gains of the 7p and 12q chromosomes and related oncogenes, which include some of the most recurrent oncogenic alterations in overt follicular lymphoma (TNFRSF14, EZH2, MLL2). By further delineating distinctive and hierarchical molecular and genetic features of early follicular lymphoma entities, our analysis underlines the importance of applying appropriate criteria for the differential diagnosis. It also provides a first set of candidates likely to be involved in the cascade of hits that pave the path of the various progression phases to follicular lymphoma development.

Germinal center reentries of BCL2-overexpressing B cells drive follicular lymphoma progression.

It has recently been demonstrated that memory B cells can reenter and reengage germinal center (GC) reactions, opening the possibility that multi-hit lymphomagenesis gradually occurs throughout life during successive immunological challenges. Here, we investigated this scenario in follicular lymphoma (FL), an indolent GC-derived malignancy. We developed a mouse model that recapitulates the FL hallmark t(14;18) translocation, which results in constitutive activation of antiapoptotic protein B cell lymphoma 2 (BCL2) in a subset of B cells, and applied a combination of molecular and immunofluorescence approaches to track normal and t(14;18)(+) memory B cells in human and BCL2-overexpressing B cells in murine lymphoid tissues. BCL2-overexpressing B cells required multiple GC transits before acquiring FL-associated developmental arrest and presenting as GC B cells with constitutive activation-induced cytidine deaminase (AID) mutator activity. Moreover, multiple reentries into the GC were necessary for the progression to advanced precursor stages of FL. Together, our results demonstrate that protracted subversion of immune dynamics contributes to early dissemination and progression of t(14;18)(+) precursors and shapes the systemic presentation of FL patients.