Determinants of the t(14;18) translocation and their role in t(14;18)-positive follicular lymphoma.

PURPOSE: The strong association between t(14;18) translocation and follicular lymphoma (FL) is well known. However, the determinants of this chromosomal aberration and their role in t(14;18) associated FL remain to be established. METHODS: t(14;18) frequency within the B cell lymphoma 2 major breakpoint region was determined for 135 incident FL cases and 251 healthy controls as part of a nested case-control study within the European Prospective Investigation into Cancer cohort. Quantitative real-time PCR was performed in DNA extracted from blood samples taken at recruitment. The relationship between prevalence and frequency of the translocation with baseline anthropometric, lifestyle, and dietary factors in cases and controls was determined. Unconditional logistic regression was used to explore whether the risk of FL associated with these factors differed in t(14;18)(+) as compared to t(14;18)(-) cases. RESULTS: Among incident FL cases, educational level (χ(2) p = 0.021) and height (χ(2) p = 0.025) were positively associated with t(14;18) prevalence, and cases with high frequencies [t(14;18)(HF)] were significantly taller (t test p value = 0.006). These findings were not replicated in the control population, although there were a number of significant associations with dietary variables. Further analyses revealed that height was a significant risk factor for t(14;18)(+) FL [OR 6.31 (95% CI 2.11, 18.9) in the tallest versus the shortest quartile], but not t(14;18)(-) cases. CONCLUSIONS: These findings suggest a potential role for lifestyle factors in the prevalence and frequency of the t(14;18) translocation. The observation that the etiology of FL may differ by t(14;18) status, particularly with regard to height, supports the subdivision of FL by translocation status.

CD146 mediates VEGF-induced melanoma cell extravasation through FAK activation.

CD146 is an adhesion molecule expressed by both melanoma and endothelial cells and thus is well positioned to control melanoma extravasation. Nevertheless, during melanoma metastasis, the involvement of CD146 expressed within tumor microenvironment has never been analyzed. To investigate whether host CD146 mediates the extravasation of melanoma cells across the endothelium, we generated CD146 KO mice. We demonstrated that host CD146 did not affect melanoma growth or tumor angiogenesis but promoted hematogenous melanoma metastasis to the lung. Accordingly, the survival of CD146-deficient mice was markedly prolonged during melanoma metastasis. Interestingly, vascular endothelial growth factor-induced vascular permeability was significantly decreased in CD146 KO mice. We also provided evidence that VEGF-induced transendothelial migration of melanoma cells was significantly reduced across CD146 KO lung microvascular endothelial cells (LMEC). CD146 deficiency decreased the expression of VEGFR-2/Ve-cadherin and altered focal adhesion kinase (FAK) activation in response to VEGF. In addition, inhibition of FAK phosphorylation reduced transmigration of B16 melanoma cells across WT LMEC at the same level that across CD146 KO LMEC. Altogether, we propose a novel mechanism involving the VEGF/CD146/FAK/Ve-cadherin network in melanoma extravasation across the vessel barrier that identifies CD146-targeted therapy as a potential strategy for the treatment of melanoma metastasis.

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.

t(14;18) Translocation: A predictive blood biomarker for follicular lymphoma.

PURPOSE: The (14;18) translocation constitutes both a genetic hallmark and critical early event in the natural history of follicular lymphoma (FL). However, t(14;18) is also detectable in the blood of otherwise healthy persons, and its relationship with progression to disease remains unclear. Here we sought to determine whether t(14;18)-positive cells in healthy individuals represent tumor precursors and whether their detection could be used as an early predictor for FL. PARTICIPANTS AND METHODS: Among 520,000 healthy participants enrolled onto the EPIC (European Prospective Investigation Into Cancer and Nutrition) cohort, we identified 100 who developed FL 2 to 161 months after enrollment. Prediagnostic blood from these and 218 controls were screened for t(14;18) using sensitive polymerase chain reaction-based assays. Results were subsequently validated in an independent cohort (65 case participants; 128 controls). Clonal relationships between t(14;18) cells and FL were also assessed by molecular backtracking of paired prediagnostic blood and tumor samples. RESULTS: Clonal analysis of t(14;18) junctions in paired prediagnostic blood versus tumor samples demonstrated that progression to FL occurred from t(14;18)-positive committed precursors. Furthermore, healthy participants at enrollment who developed FL up to 15 years later showed a markedly higher t(14;18) prevalence and frequency than controls (P < .001). Altogether, we estimated a 23-fold higher risk of subsequent FL in blood samples associated with a frequency > 10(-4) (odds ratio, 23.17; 95% CI, 9.98 to 67.31; P < .001). Remarkably, risk estimates remained high and significant up to 15 years before diagnosis. CONCLUSION: High t(14;18) frequency in blood from healthy individuals defines the first predictive biomarker for FL, effective years before diagnosis.

The involvement of CD146 and its novel ligand Galectin-1 in apoptotic regulation of endothelial cells.

CD146 is a highly glycosylated junctional adhesion molecule, expressed on human vascular endothelial cells and involved in the control of vessel integrity. Galectin-1 is a lectin produced by vascular cells that can binds N- and O-linked oligosaccharides of cell membrane glycoproteins. Because both CD146 and Galectin-1 are involved in modulation of cell apoptosis, we hypothesized that Galectin-1 could interact with CD146, leading to functional consequences in endothelial cell apoptosis. We first characterized CD146 glycosylations and showed that it is mainly composed of N-glycans able to establish interactions with Galectin-1. We demonstrated a sugar-dependent binding of recombinant CD146 to Galectin-1 using both ELISA and Biacore assays. This interaction is direct, with a K(D) of 3.10(-7) M, and specific as CD146 binds to Galectin-1 and not to Galectin-2. Moreover, co-immunoprecipitation experiments showed that Galectin-1 interacts with endogenous CD146 that is highly expressed by HUVEC. We observed a Galectin-1-induced HUVEC apoptosis in a dose-dependent manner as demonstrated by Annexin-V/7AAD staining. Interestingly, both down-regulation of CD146 cell surface expression using siRNA and antibody-mediated blockade of CD146 increase this apoptosis. Altogether, our results identify Galectin-1 as a novel ligand for CD146 and this interaction protects, in vitro, endothelial cells against apoptosis induced by Galectin-1.

Mouse CD146/MCAM is a marker of natural killer cell maturation.

CD146/melanoma cell adhesion molecule is an adhesion molecule expressed by endothelial cells and by a small fraction of activated T and B lymphocytes in humans. In order to analyze the pattern of CD146 expression in mouse leukocytes at steady-state conditions, we generated a set of novel rat anti-mouse CD146 monoclonal antibodies. CD146 expression was undetectable on monocytes, dendritic cells, T cells or B cells, but was expressed on about 30% of neutrophils and 60% of NK cells. Within murine lymphocytes, CD146 was defined as a novel NK-specific surface molecule. An increased percentage of CD146+ cells was found in the most mature CD27(-)CD11b+ NK cell subpopulation, which also displays higher expression of Ly49C/I, Ly49D and KLRG1 and lower expression of NKG2A/C/E molecules. CD146+ NK cells were found to be less cytotoxic and produce less IFN-gamma than CD146(-) NK cells upon stimulation with target cells or activating antibodies. These findings define CD146 as a marker of mouse NK cell maturation that may be used as an alternative to the combined use of CD27 and CD11b staining to detect final stages of NK cell maturation.