Apoptosis and restriction of G(1)/S cell cycle by fenretinide in Burkitt's lymphoma mutu I cell line accessed with bcl-6 down-regulation

Sphingolipids and Lymphomas: A Double-Edged Sword

Lymphomas are a highly heterogeneous group of hematological neoplasms. Given their ethiopathogenic complexity, their classification and management can become difficult tasks; therefore, new approaches are continuously being sought. Metabolic reprogramming at the lipid level is a hot topic in cancer research, and sphingolipidomics has gained particular focus in this area due to the bioactive nature of molecules such as sphingoid bases, sphingosine-1-phosphate, ceramides, sphingomyelin, cerebrosides, globosides, and gangliosides. Sphingolipid metabolism has become especially exciting because they are involved in virtually every cellular process through an extremely intricate metabolic web; in fact, no two sphingolipids share the same fate. Unsurprisingly, a disruption at this level is a recurrent mechanism in lymphomagenesis, dissemination, and chemoresistance, which means potential biomarkers and therapeutical targets might be hiding within these pathways. Many comprehensive reviews describing their role in cancer exist, but because most research has been conducted in solid malignancies, evidence in lymphomagenesis is somewhat limited. In this review, we summarize key aspects of sphingolipid biochemistry and discuss their known impact in cancer biology, with a particular focus on lymphomas and possible therapeutical strategies against them.

Somatic hypermutation and mRNA expression levels of the BCL-6 gene in patients with hepatitis C virus-associated lymphoproliferative diseases

Chronic hepatitis C virus (HCV) infection leads to mixed cryoglobulinaemia (MC) and B-cell non-Hodgkin lymphoma (B-NHL). Aberrant somatic hypermutation and deregulation of the oncogene BCL-6 is associated with lymphomagenesis. Recently, HCV was shown to induce BCL-6 mutations in vitro. The BCL-6 gene (area B) was cloned and sequenced from peripheral blood mononuclear cells (PBMC) of 21 chronically HCV-infected patients with or without MC and B-NHL, and six healthy controls. Mutational frequencies, genetic complexity and diversity were calculated. BCL-6 mRNA from PBMC was quantified by real-time polymerase chain reaction, and additional sustained virologic responders to antiviral therapy and HBV patients served as controls. The overall/recurrent mutational frequencies tended to be lower in MC and B-NHL patients when compared with controls (P = 0.15 and 0.06, respectively). Genetic complexity was significantly lower in MC and B-NHL patients (P = 0.025). BCL-6 mRNA concentration was decreased in all HCV patients when compared with healthy controls, sustained virologic responder and HBV patients (P = 0.005). Although HCV can induce BCL-6 mutations in vitro, lower mutational frequencies and decreased BCL-6 mRNA expression in vivo suggest no major role of aberrant somatic hypermutation in HCV-associated MC and B-NHL.

Mechanisms of fenretinide-induced apoptosis

Fenretinide, a synthetic retinoid, has emerged as a promising anticancer agent based on numerous in vitro and animal studies, as well as chemoprevention clinical trials. In vitro observations suggest that the anticancer activity of fenretinide may arise from its ability to induce apoptosis in tumor cells. Diverse signaling molecules including reactive oxygen species, ceramide, and ganglioside GD3 can mediate apoptosis induction by fenretinide in transformed, premalignant, and malignant cells. In many cell types, these signaling intermediates appear to be induced by mechanisms that are independent of retinoic acid receptor activation, and ultimately initiate the intrinsic or mitochondrial-mediated pathway of cell elimination. Numerous investigations conducted during the past 10 years have discovered a great deal about the apoptogenic activity of fenretinide. In this review we explore the mechanisms associated with fenretinide-induced apoptosis and highlight certain mechanistic underpinnings of fenretinide-induced cell death that remain poorly understood and thus warrant further characterization.

Expression of p53, c-Myc, or Bcl-6 suggests a poor prognosis in primary central nervous system diffuse large B-cell lymphoma among immunocompetent individuals

CONTEXT

Primary central nervous system (CNS) diffuse large B-cell lymphoma (DLBCL) in immunocompetent individuals, although rare, has been rising in incidence. Currently, no reliable prognostic markers are available for these individuals.

OBJECTIVE

To study the implications of expression of a panel of oncogenic proteins (Bcl-2, Bcl-6, and c-Myc) and p53 for predicting clinical outcome, particularly overall survival, in immunocompetent individuals with primary CNS DLBCL.

DESIGN

Fourteen primary CNS DLBCL cases were retrospectively studied by immunohistochemistry on formalin-fixed, paraffin-embedded sections for the expression of c-Myc, Bcl-2, Bcl-6, and p53.

RESULTS

The overall frequencies of expression for p53, c-Myc, Bcl-2, and Bcl-6 in these cases were 29%, 50%, 71%, and 57%, respectively. Cases with expression of p53, c-Myc, or Bcl-6 had a poorer overall survival than those without (Kaplan-Meier survival analysis: 50% cumulative overall survival, 2 months vs 30-60 months, P =.02, log-rank test; 9-16 months vs 21-60 months, P =.03, log-rank test; and 9-16 months vs 21-60 months, P =.16, log-rank test, respectively). The expression of Bcl-2 or proliferation activity by MIB-1 showed no correlation with overall survival. Likewise, the clinical parameters, including age, location of tumors, multiplicity of tumor lesions, and lactase dehydrogenase levels revealed no impact on overall survival.

CONCLUSION

Our results suggest that patients with expression of p53, c-Myc, or Bcl-6 have a poorer overall survival than those without. Since traditional prognostic markers in non-CNS DLBCL, such as staging and International Prognostic Index scores, are not applicable to primary CNS DLBCL, evaluation of p53, c-Myc, and Bcl-6 by immunohistochemistry may be warranted as part of prognostic evaluation in immunocompetent patients with primary CNS DLBCL. Further studies are indicated to confirm our observations.