NF-kappaB/STAT3/PI3K signaling crosstalk in iMyc E mu B lymphoma.

BACKGROUND: Myc is a well known driver of lymphomagenesis, and Myc-activating chromosomal translocation is the recognized hallmark of Burkitt lymphoma, an aggressive form of non-Hodgkin's lymphoma. We developed a model that mimics this translocation event by inserting a mouse Myc cDNA gene into the immunoglobulin heavy chain locus, just upstream of the intronic Emu enhancer. These mice, designated iMyc E mu, readily develop B-cell lymphoma. To study the mechanism of Myc-induced lymphoma, we analyzed signaling pathways in lymphoblastic B-cell lymphomas (LBLs) from iMyc E mu mice, and an LBL-derived cell line, iMyc E mu-1. RESULTS: Nuclear factor-kappaB (NF-kappaB) and signal transducer and activator of transcription 3 (STAT3) were constitutively activated in iMyc E mu mice, not only in LBLs but also in the splenic B-lymphocytes of young animals months before tumors developed. Moreover, inhibition of either transcription factor in iMyc E mu-1 cells suppressed growth and caused apoptosis, and the abrogation of NF-kappaB activity reduced DNA binding by both STAT3 and Myc, as well as Myc expression. Inhibition of STAT3 signaling eliminated the activity of both NF-kappaB and Myc, and resulted in a corresponding decrease in the level of Myc. Thus, in iMyc E mu-1 cells NF-kappaB and STAT3 are co-dependent and can both regulate Myc. Consistent with this, NF-kappaB and phosphorylated STAT3 were physically associated with one another. In addition, LBLs and iMyc E mu-1 cells also showed constitutive AKT phosphorylation. Blocking AKT activation by inhibiting PI3K reduced iMyc E mu-1 cell proliferation and caused apoptosis, via downregulation of NF-kappaB and STAT3 activity and a reduction of Myc levels. Co-treatment with NF-kappaB, STAT3 or/and PI3K inhibitors led to additive inhibition of iMyc E mu-1 cell proliferation, suggesting that these signaling pathways converge. CONCLUSIONS: Our findings support the notion that constitutive activation of NF-kappaB and STAT3 depends on upstream signaling through PI3K, and that this activation is important for cell survival and proliferation, as well as for maintaining the level of Myc. Together, these data implicate crosstalk among NF-kappaB, STAT3 and PI3K in the development of iMyc E mu B-cell lymphomas.

Interactions between Mycoplasma pulmonis and immune systems in the mealworm beetle, Tenebrio molitor.

Mycoplasmas, the smallest self-replicating organisms, are unique in that they lack cell walls but possess distinctive plasma membranes containing sterol acquired from their growth environment. Although mycoplasmas are known to be successful pathogens in a wide range of animal hosts, including humans, the molecular basis for their virulence and interaction with the host immune systems remains largely unknown. This study was conducted to elucidate the biochemical relationship between mycoplasma and the insect immune system. We investigated defense reactions of Tenebrio molitor that were activated in response to infection with Mycoplasma pulmonis. The results revealed that T. molitor larvae were more resistant to mycoplasma infection than normal bacteria equipped with cell walls. Intruding M. pulmonis cells were effectively killed by toxins generated from activation of the proPO cascade in hemolymph, but not by cellular reactions or antimicrobial peptides. It was determined that these different anti-mycoplasma effects of T. molitor immune components were primarily attributable to surface molecules of M. pulmonis such as phospholipids occurring in the outer leaflet of the membrane lipid bilayer. While phosphatidylcholine, a phospholipid derived from the growth environment, contributed to the resistance of M. pulmonis against antimicrobial peptides produced by T. molitor, phosphatidylglycerol was responsible for triggering activation of the proPO cascade.

CDKN1A and FANCD2 are potential oncotargets in Burkitt lymphoma and multiple myeloma.

BACKGROUND: Comparative genetic and biological studies on malignant tumor counterparts in human beings and laboratory mice may be powerful gene discovery tools for blood cancers, including neoplasms of mature B-lymphocytes and plasma cells such as Burkitt lymphoma (BL) and multiple myeloma (MM). METHODS: We used EMSA to detect constitutive NF-κB/STAT3 activity in BL- and MM-like neoplasms that spontaneously developed in single-transgenic IL6 (interleukin-6) or MYC (c-Myc) mice, or in double-transgenic IL6MYC mice. qPCR measurements and analysis of clinical BL and MM datasets were employed to validate candidate NF-κB/STAT3 target genes. RESULTS: qPCR demonstrated that IL6- and/or MYC-dependent neoplasms in mice invariably contain elevated mRNA levels of the NF-κB target genes, Cdkn1a and Fancd2. Clinical studies on human CDKN1A, which encodes the cell cycle inhibitor and tumor suppressor p21, revealed that high p21 message predicts poor therapy response and survival in BL patients. Similarly, up-regulation of FANCD2, which encodes a key member of the Fanconi anemia and breast cancer pathway of DNA repair, was associated with poor outcome of patients with MM, particularly those with high-risk disease. CONCLUSIONS: Our findings suggest that CDKN1A and FANCD2 are potential oncotargets in BL and MM, respectively. Additionally, the IL-6- and/or MYC-driven mouse models of human BL and MM used in this study may lend themselves to the biological validation of CDKN1A and FANCD2 as molecular targets for new approaches to cancer therapy and prevention.

Piperlongumine inhibits proliferation and survival of Burkitt lymphoma in vitro.

Piperlongumine (PL), a pepper plant alkaloid from Piper longum, kills solid tumor cells in a highly selective, potent fashion. To evaluate whether PL may have similar effects on malignant blood cells, we determined the efficacy with which PL inhibits the B-lymphocyte derived neoplasm, Burkitt lymphoma (BL). Low micromolar concentrations of PL (IC(50) = 2.8 µM × 8.5 µM) curbed growth and survival of two EBV(+) BL cell lines (Daudi, Raji) and two EBV BL cell lines (Ramos, DG-75), but left normal peripheral blood B-lymphocytes unharmed. PL-dependent cytotoxicity was effected in part by reduced NF-κB and MYC activity, with the former being caused by inhibition of IκBα degradation, nuclear translocation of p65, and binding of NF-κB dimers to cognate DNA sequences in gene promoters. In 4 of 4 BL cell lines, the NF-κB/MYC-regulated cellular target genes, E2F1 and MYB, were down regulated, while the stress sensor gene, GADD45B, was up regulated. The EBV-encoded oncogene, LMP-1, was suppressed in Daudi and Raji cells. Considering that NF-κB, MYC and LMP-1 play a crucial role in the biology of many blood cancers including BL, our results provide a strong preclinical rationale for considering PL in new intervention approaches for patients with hematologic malignancies.