Oncogene-specific T cells fail to eradicate lymphoma-initiating B cells in mice.

To date, little is known about the interaction between (pre-)malignant B cells and T cells. We generated transgenic mice that allow B cell-specific induction of the oncogene SV40 large T-antigen (TAg) to analyze the role of oncogene-specific T cells during sporadic B-cell lymphoma development. Constitutive TAg expression in CD19-Cre × LoxP-Tag mice resulted in TAg-tolerant CD8+ T cells and development of B-cell lymphomas. In contrast, CD19-CreERT2 × LoxP-Tag mice retained TAg-competent CD8+ T cells at time of oncogene induction and TAg expression in few B cells of adult mice resulted in exceptionally rare lymphoma formation late in life. Increased lymphoma incidence in the absence of TAg-specific T cells suggested T cell-mediated inhibition of lymphoma progression. However, TAg-initiated B cells were not eliminated by T cells and detected long term. Our results demonstrate a failure of the immune system to eradicate lymphoma-initiating B cells, retaining the risk of lymphoma development.

EBAG9 controls CD8+ T cell memory formation responding to tumor challenge in mice.

Insight into processes that determine CD8+ T cell memory formation has been obtained from infection models. These models are biased toward an inflammatory milieu and often use high-avidity CD8+ T cells in adoptive-transfer procedures. It is unclear whether these conditions mimic the differentiation processes of an endogenous repertoire that proceed upon noninflammatory conditions prevailing in premalignant tumor lesions. We examined the role of cytolytic capacity on CD8+ T cell fate decisions when primed by tumor cells or by minor histocompatibility antigen-mismatched leukocytes. CD8+ memory commitment was analyzed in Ebag9-deficient mice that exhibited enhanced tumor cell lysis. This property endowed Ebag9-/- mice with extended control of Tcl-1 oncogene-induced chronic lymphocytic leukemia progression. In Ebag9-/- mice, an expanded memory population was obtained for anti-HY and anti-SV-40 T antigen-specific T cells, despite unchanged effector frequencies in the primary response. By comparing the single-cell transcriptomes of CD8+ T cells responding to tumor cell vaccination, we found differential distribution of subpopulations between Ebag9+/+ and Ebag9-/- T cells. In Ebag9-/- cells, these larger clusters contained genes encoding transcription factors regulating memory cell differentiation and anti-apoptotic gene functions. Our findings link EBAG9-controlled cytolytic activity and the commitment to the CD8+ memory lineage.

Gene expression studies in kiwifruit and gene over-expression in Arabidopsis indicates that GDP-L-galactose guanyltransferase is a major control point of vitamin C biosynthesis.

Vitamin C (L-ascorbic acid, AsA) is an essential metabolite for plants and animals. Kiwifruit (Actinidia spp.) are a rich dietary source of AsA for humans. To understand AsA biosynthesis in kiwifruit, AsA levels and the relative expression of genes putatively involved in AsA biosynthesis, regeneration, and transport were correlated by quantitative polymerase chain reaction in leaves and during fruit development in four kiwifruit genotypes (three species; A. eriantha, A. chinensis, and A. deliciosa). During fruit development, fruit AsA concentration peaked between 4 and 6 weeks after anthesis with A. eriantha having 3-16-fold higher AsA than other genotypes. The rise in AsA concentration typically occurred close to the peak in expression of the L-galactose pathway biosynthetic genes, particularly the GDP-L-galactose guanyltransferase gene. The high concentration of AsA found in the fruit of A. eriantha is probably due to higher expression of the GDP-mannose-3',5'-epimerase and GDP-L-galactose guanyltransferase genes. Over-expression of the kiwifruit GDP-L-galactose guanyltransferase gene in Arabidopsis resulted in up to a 4-fold increase in AsA, while up to a 7-fold increase in AsA was observed in transient expression studies where both GDP-L-galactose guanyltransferase and GDP-mannose-3',5'-epimerase genes were co-expressed. These studies show the importance of GDP-L-galactose guanyltransferase as a rate-limiting step to AsA, and demonstrate how AsA can be significantly increased in plants.