Andrew P. Jewell

TIS11 Family Proteins and Their Roles in Posttranscriptional Gene Regulation

Posttranscriptional regulation of gene expression of mRNAs containing adenine-uridine rich elements (AREs) in their 3′ untranslated regions is mediated by a number of different proteins that interact with these elements to either stabilise or destabilise them. The present review concerns the TPA-inducible sequence 11 (TIS11) protein family, a small family of proteins, that appears to interact with ARE-containing mRNAs and promote their degradation. This family of proteins has been extensively studied in the past decade. Studies have focussed on determining their biochemical functions, identifying their target mRNAs, and determining their roles in cell functions and diseases.

Cancer‐testis antigens in haematological malignancies

Immunotherapy is an attractive therapeutic option for patients with haematological malignancies. Until recently, the progress in the development of tumour vaccines for haematological malignancies had been slow due to the lack of suitable targets. Cancer‐testis (CT) antigens are potentially suitable molecules for tumour vaccines of haematological malignancies because of their high immunogenicity in vivo and their relatively restricted normal tissue distribution. This review evaluates the properties and potential functions of CT antigens. We discuss the expression of CT antigens in patient with haematological malignancies and provide evidence in support of their immunogenicity in vivo in these patients. We also address the role of ‘epigenetic’ regulation of CT antigens in haematological malignancies and how hypomethylating agents could induce the expression of some of these antigens in tumour cells to overcome the problem of heterogeneity of expression of the antigen within individual tumour specimens. Data implicating the interaction of the promoter genes of some of these CT antigens with the MeCP2 protein also suggest the potential role of the histone deacetylase inhibitors in inducing antigen expression in tumour cells. Finally, we discuss the direction of future research in advancing the development of tumour vaccines for haematological malignancies.

Expansion of CD4+ T cells with a cytotoxic phenotype in patients with B-chronic lymphocytic leukaemia (B-CLL)

Abnormal CD4/CD8 ratios and T‐cell function have previously been shown in patients with B‐chronic lymphocytic leukaemia (B‐CLL). We have demonstrated that CD4+ T cells containing both serine esterase and perforin (PF) are increased in the blood of these patients. Using flow cytometry, we have shown that the CD4+ PF+ cells were CD57+ but lacked expression of CD28, suggesting a mature population. The same phenotype in CD8+ T cells is characteristic of mature cytotoxic T cells. However, in contrast to the CD8+ T cells, the CD4+ T cells were more frequently CD45RO positive than CD45RA positive, indicating prior antigen experience. In contrast, this population lacked expression of either CD69 or HLA‐DR, arguing that they were not activated or that they are an abnormal population of T cells. Their constitutive cytokine levels showed them mainly to contain IL4 and not IFNγ, suggesting a Th2 phenotype. The role of the CD4+ PF+ T‐cell population is at present uncertain. However, this potentially cytotoxic T‐cell population could contribute both to enhancing survival of the B‐CLL tumour cells through production of IL4, and to the immunodeficient state frequently seen in patients with this tumour, independent of drug treatment.

CD5 B cells and B-cell malignancies

Over the past year, progress has been made in understanding of the physiology and disease associations of CD5+ (B1) B cells, although their exact role in pathogenesis remains unclear. Earlier studies on the negative function of CD5 within the B-cell receptor complex have been substantiated, and it seems likely that soon the signaling pathways used by this coreceptor will be elucidated. Progress in diagnosis, physiology, and etiopathogenesis of CD5+ malignancies has been made, particularly in B-cell chronic lymphocytic leukemia. The low-level expression of surface immunoglobulin has been explained by the mutations that occur in the associated CD79b. Two new potential tumor-suppressor genes have been identified in the hot spot of chromosome 13q, which provides an exciting step forward in understanding of the etiopathogenesis of some B-cell chronic lymphocytic leukemia. Activated signal transducers for activation of transcription factors molecules have been shown to be phosphorylated on different amino acids in B1 and chronic lymphocytic leukemia tumors, although the significance of this is, as yet, unclear. Finally, aberrant expression of CD40L by chronic lymphocytic leukemia T cells may contribute to the immunodeficiency that develops in these patients.

Differential expression of CD180 and IgM by B-cell chronic lymphocytic leukaemia cells using mutated and unmutated immunoglobulin VH genes

We have studied the surface expression of the Toll‐like receptor family member CD180 on cells from 78 patients with B‐chronic lymphocytic leukaemia (B‐CLL). B‐CLL cells had variable levels of CD180 expression, but this was always less than that expressed by normal blood B cells and was stable for 24 months. Significantly higher levels of CD180 were expressed by B‐CLL cells with mutated IGVH genes compared with those using unmutated IGVH genes. This was in contrast to the higher levels of expression of surface immunoglobulin M by B‐CLL cells using unmutated, rather than mutated IGVH genes. CD180 was functional on B‐CLL cells from some of the patients, as shown by the increased expression of CD86 following incubation in vitro with anti‐CD180. The differential expression of CD180 amongst B‐CLL patients is one more marker that may define more precisely the different biological properties of this heterogeneous disease.

Involvement of Tis11b, an AU-rich binding protein, in induction of apoptosis by rituximab in B cell chronic lymphocytic leukemia cells

B-cell chronic lymphocytic leukemia is the commonest form of leukemia in the Western world, characterized by an accumulation of monoclonal CD5+ B cells in the peripheral blood and lymphoid organs. It is clinically a heterogenous disease with overall variable response to many drugs used either alone or in combination, and is currently untreatable.

Role of apoptosis in the pathogenesis of B-cell chronic lymphocytic leukaemia

Abstract B-cell chronic lymphocytic leukaemia (B-CLL) is a clinically heterogeneous disease characterised by the accumulation of a clonal population of B lymphocytes. This accumulation is considered to result from the prolonged survival of B-CLL cells arrested in the G0 stage of the cell cycle. However, when cultured in vitro, B-CLL cells die rapidly by apoptosis. It is now clear that a number of factors can delay or postpone the onset of apoptosis, including a number of cytokines and direct contact with different cell types. Although many drugs are now known to cause clinical improvement in B-CLL by causing apoptosis of B-CLL cells, in only a few cases have biological mechanisms been reported to have similar effects. It is now important to understand the role of these mechanisms in the pathogenesis and progression of B-CLL, and to devise strategies to exploit them for therapeutic use.

Resistance of Chronic Lymphocytic Leukaemia Cells to Interferon-α Generated Lymphokine Activated Killer Cells

Recent studies have shown that, when used in early stage disease, interferon-alpha (IFN-alpha) can produce a fall in the number of malignant cells in the peripheral blood of patients with B-CLL. In this study, we investigated the effect of IFN-alpha on natural killer (NK) cell and lymphokine-activated cell (LAK) activity in patients with B-CLL. In vitro, IFN-alpha (500 U/ml for 18 hours) induced LAK activity in patients with B-CLL (27.7 +/- 9.9%, n = 20), and IL-2 (500 U/ml for 5 days) produced similar activity (35.9 +/- 8.8%, n = 7). Despite the induction of LAK activity by IFN-alpha and IL2 in patients with B-CLL, the malignant cells remained resistant to both allogeneic and autologous LAK effectors. NK activity in patients with B-CLL is also low (23.1 +/- 7.2%, n = 20), and B-CLL cells were resistant to NK cell activity. In cold target competition assays, CLL cells did not compete with labelled K562 or Daudi targets in the NK and LAK assays, suggesting that the malignant cells are not recognised by the effector cells, and this may be related to low level of expression of the adhesion receptors, LFA-1 and ICAM-1. Finally, CLL cells were also resistant to antibody dependent cell mediated cytotoxicity, but were susceptible to antibody dependent complement mediated lysis. These results suggest that it is unlikely that the effects of IFN-alpha in B-CLL are due to the enhancement of NK or LAK activity.

Serum macrophage colony‐stimulating factor (M‐CSF) levels correlate with clinical response to interferon‐alpha in patients with early‐stage B‐CLL

Summary Interferon‐alpha (IFN‐α) reduces peripheral lymphocyte counts in B‐CLL (CLL). In eight patients with stage 0 CLL on IFN‐α therapy, peripheral lymphocyte counts fell to 61·7 19·5% of baseline at week 2 (P<0·01), while serum M‐CSF levels rose from 455 183 U/ml to 686 110 U/ml (P<0·05). Neopterin levels also showed a significant rise. M‐CSF levels were correlated with clinical response in these patients. Increased production of M‐CSF and the activation of mononuclear phagocytes may be involved in clinical responses to IFN‐α in early‐stage CLL.

Transendothelial migration confers a survival advantage to activated T lymphocytes: role of LFA-1/ICAM-1 interactions

The clearance of activated T lymphocytes by apoptosis is an essential component in the resolution of the immune response; however, certain signals received within inflamed tissue may result in the persistence of activated T cells. Our previous work has shown that, when compared with resting cells, effector cells migrate more efficiently across endothelium, thus such cells may be selectively recruited to sites of inflammation. We hypothesized that transmigration of T cells across endothelium might influence cell survival. We have generated T cell lines by culturing in IL‐2 following PHA activation. These T cell lines die rapidly by apoptosis when deprived of IL‐2 (53·7 ± 4·0% survival after 24 h). In contrast, cells that have migrated across human umbilical vein endothelial cells (HUVEC) survived significantly better than control cells (80·3 ± 3·6%, n= 18, P < 0·001). Endothelial cell conditioned medium was also able to reduce apoptosis, but this effect was small when compared with the protective effect of transmigration. Culture of T lymphocytes on fibronectin, or RGD peptides, or in suspension with a range of chemokines active on T cells, including RANTES and lymphotactin had no effect on survival. In contrast, blocking LFA‐l/ICAM‐l interactions reduced the protective effect of transmigration (42·3 ± 6·7% reduction). Culture of activated T cells on immobilized ICAM‐l alone also increased survival. These results indicate that signals received by activated T cells during extravasation can influence their subsequent survival within tissue, and implicates the involvement of LF A‐l/ICAM‐l interactions.