Elisabetta Mereu

The Krüppel-like factor 2 transcription factor gene is recurrently mutated in splenic marginal zone lymphoma

The Kruppel-like factor 2 transcription factor gene is recurrently mutated in splenic marginal zone lymphoma

Mutations in NOTCH1 PEST domain orchestrate CCL19-driven homing of chronic lymphocytic leukemia cells by modulating the tumor suppressor gene DUSP22

Even if NOTCH1 is commonly mutated in chronic lymphocytic leukemia (CLL), its functional impact in the disease remains unclear. Using CRISPR/Cas9-generated Mec-1 cell line models, we show that NOTCH1 regulates growth and homing of CLL cells by dictating expression levels of the tumor suppressor gene DUSP22. Specifically, NOTCH1 affects the methylation of DUSP22 promoter by modulating a nuclear complex, which tunes the activity of DNA methyltransferase 3A (DNMT3A). These effects are enhanced by PEST-domain mutations, which stabilize the molecule and prolong signaling. CLL patients with a NOTCH1-mutated clone showed low levels of DUSP22 and active chemotaxis to CCL19. Lastly, in xenograft models, NOTCH1-mutated cells displayed a unique homing behavior, localizing preferentially to the spleen and brain. These findings connect NOTCH1, DUSP22, and CCL19-driven chemotaxis within a single functional network, suggesting that modulation of the homing process may provide a relevant contribution to the unfavorable prognosis associated with NOTCH1 mutations in CLL.

SLAMF1 regulation of chemotaxis and autophagy determines CLL patient response.

Chronic lymphocytic leukemia (CLL) is a variable disease; therefore, markers to identify aggressive forms are essential for patient management. Here, we have shown that expression of the costimulatory molecule and microbial sensor SLAMF1 (also known as CD150) is lost in a subset of patients with an aggressive CLL that associates with a shorter time to first treatment and reduced overall survival. SLAMF1 silencing in CLL-like Mec-1 cells, which constitutively express SLAMF1, modulated pathways related to cell migration, cytoskeletal organization, and intracellular vesicle formation and recirculation. SLAMF1 deficiency associated with increased expression of CXCR4, CD38, and CD44, thereby positively affecting chemotactic responses to CXCL12. SLAMF1 ligation with an agonistic monoclonal antibody increased ROS accumulation and induced phosphorylation of p38, JNK1/2, and BCL2, thereby promoting the autophagic flux. Beclin1 dissociated from BCL2 in response to SLAMF1 ligation, resulting in formation of the autophagy macrocomplex, which contains SLAMF1, beclin1, and the enzyme VPS34. Accordingly, SLAMF1-silenced cells or SLAMF1(lo) primary CLL cells were resistant to autophagy-activating therapeutic agents, such as fludarabine and the BCL2 homology domain 3 mimetic ABT-737. Together, these results indicate that loss of SLAMF1 expression in CLL modulates genetic pathways that regulate chemotaxis and autophagy and that potentially affect drug responses, and suggest that these effects underlie unfavorable clinical outcome experienced by SLAMF1(lo) patients.

The heterogeneous landscape of ALK negative ALCL

Anaplastic Large Cell Lymphoma (ALCL) is a clinical and biological heterogeneous disease including systemic ALK positive and ALK negative entities. Whereas ALK positive ALCLs are molecularly characterized and readily diagnosed, specific immunophenotypic or genetic features to define ALK negative ALCL are missing, and their distinction from other T-cell non-Hodgkin lymphomas (T-NHLs) can be controversial. In recent years, great advances have been made in dissecting the heterogeneity of ALK negative ALCLs and in providing new diagnostic and treatment options for these patients. A new revision of the World Health Organization (WHO) classification promoted ALK negative ALCL to a definite entity that includes cytogenetic subsets with prognostic implications. However, a further understanding of the genetic landscape of ALK negative ALCL is required to dictate more effective therapeutic strategies specifically tailored for each subgroup of patients.

Transposable elements: The enemies within

Understanding transformation mechanisms other than genetic aberrations has recently captured the attention of cancer researchers. To date, the role of transposable elements (TEs) in tumor development remains largely undefined. However, an increasing number of studies have reported that loss of epigenetic control causes TE reactivation and consequent oncogenic transcription. Here, we discuss principal examples of TEs-driven oncogenesis. Available data suggest that long terminal repeats and long interspersed nuclear elements play a pivotal role as alternative promoters. These findings provide definitive experimental evidence that repetitive elements are a powerful underestimated force toward oncogenesis and open the possibility to new therapeutic treatments.

ALK expression favorably impacts the prognosis of NRAS‑mutated metastatic melanomas

Recent studies reported the expression of anaplastic lymphoma kinase (ALK) in malignant melanomas. The aim of this study was to investigate whether ALK expression is associated with specific clinical and molecular characteristics of melanoma metastases, and to evaluate its correlation with survival outcomes. Seventy-one patients with metastatic melanoma were investigated. Clinical features and survival outcomes were analyzed and correlated to ALK expression, as detected by immunohistochemistry and reverse transcription-quantitative polymerase chain reaction, and to the mutational status of BRAF, KRAS, NRAS, and PIK3CA. No translocations or ALK alternative isoforms were identified. ALK expression was mainly detected in NRAS mutated metastatic lesions. Interestingly, among NRAS-mutated patients, ALK positive samples displayed a significantly more favorable outcome in terms of disease specific survival, as compared to ALK negative ones. In conclusion, we suggest that ALK positive/NRAS mutated metastases represent a specific subset of metastatic melanomas, associated with a better prognosis. Validation of these observations in larger cohorts could contribute to understand the molecular events cooperating to melanoma progression, in addition to open new perspectives in the clinical and therapeutic management of this subgroup of patients.

Abstract 4575: Three-gene diagnostic classifier for ALK negative ALCL

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Anaplastic Large Cell Lymphomas (ALCL) comprise approximately 12% of all T-cell Non-Hodgkins lymphomas (T-NHL), representing a heterogeneous group whose definition, origin and relationship with other T-NHL remains controversial. The notion that ALCL strongly express CD30, and display recurrent chromosomal translocations involving the Anaplastic Lymphoma Kinase (ALK) gene, led to recognition of two subsets, according to ALK expression. Although ALK positive ALCL can be readily diagnosed, ALK negative ALCL still lack unique genetic features and their distinction from other CD30 positive Peripheral T-Cell Lymphomas (PTCL) is not trivial. To unravel the regulatory network underlying lymphomagenesis of ALCL, and to discover new genomic classifiers for the recognition of ALK-positive and ALK-negative ALCL patients, we undertook a systematic approach of pathway discovery through a gene expression profiling meta-analysis of 309 cases, using data generated by five sets of experiments. In agreement with previous studies, unsupervised analyses were not able to distinguish ALCL from the other T-NHL categories. However, pathway discovery and prediction analyses defined a minimum set of genes useful for the stratification of ALK negative ALCL and strengthened the hypothesis that ALCL correspond to a distinctive pathological subgroup within T-NHL. Application of RT-qPCR in independent data sets of cryo-preserved and formalin-fixed paraffin embedded samples confirmed the gene expression profiling predictions and validated a simple model based on the measurement of three genes. These data suggest the possibility to translate RT-qPCR protocols to routine clinical settings as a new approach to precisely define T-NHL and to select more appropriate therapeutic protocols. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4575. doi:1538-7445.AM2012-4575