No description available.

It seemed desirable to investigate further the possible role of complement and its components in the protective action of serum against transplanted neoplasms. It is the purpose of this thesis to present data which suggest that the C'4 component plays an active part in this process though the mechanism is not disclosed.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

During stress conditions, glucocorticoids are secreted and exert most of their physiological responses by binding to and modulating the transcriptional activity of the glucocorticoid receptor (GR). Once activated, GR can regulate numerous cellular processes including inflammation, development, growth, metabolism and apoptosis. Although glucocorticoids have been used in the treatment of leukaemia for over 50 years, with the molecular mechanisms by which steroids exert their pro-apoptotic effect, the pathways responsible for the development of resistance to glucocorticoid treatment, as well as their role in the programmed cell death in other tissue types have not been precisely defined. Research has demonstrated that glucocorticoid-induced apoptosis requires a transcriptionally active form of GR and is executed by the induction of the intrinsic pathway of apoptosis. In addition, GR is regulated by diverse types of cytotoxic stress; including UV irradiation and hypoxia, which alter the receptor’s transcriptional activity through multiple mechanisms. These include post-translational modifications, subcellular localisation and interaction of the receptor with co-regulator proteins. The aims of this study are to identify novel members of the Bcl-2 family that are regulated at the transcriptional level by GR in both leukaemia and other tissue types where glucocorticoids promote cell survival. In addition, the molecular crosstalk between signalling pathways activated by cytotoxic stress conditions and the mechanisms by which they differentially modulate the apoptotic response will be investigated. Results obtained in this study have identified putative glucocorticoid response elements in the promoters of the BH3-only pro-apoptotic gene NOXA and the anti-apoptotic gene Mcl-1 and confirmed that both NOXA and Mcl-1 are direct GR transcriptional targets. The glucocorticoid-mediated expression of NOXA and Mcl-1 alters their protein-protein interaction pattern, leading to the subsequent destabilisation of Mcl-1 in cell lines that undergo glucocorticoid-induced apoptosis. Investigation into the effects that other cytotoxic stress pathways have on GR function have revealed that serine 226 phosphorylation of GR by JNK occurs in a rapid and transient manner. Phosphorylation has inhibitory effects on the transcription of GR targets in a gene-specific manner, including the differential regulation of NOXA gene expression. During hypoxia, glucocorticoids differentially regulate the GR and HIF-1 target genes, NOXA and Mcl-1, altering the apoptotic response. This study has provided additional insight into the molecular mechanisms that govern glucocorticoid-induced programmed cell death and revealed mechanisms by which glucocorticoids and cytotoxic stress pathways crosstalk, regulating apoptosis.

Many haematological malignancies are associated with widespread alterations of the transcriptional and epigenetic programmes. Changes in DNA methylation provide the clearest example of epigenetic changes, but the mechanism(s) underlying such changes is unknown. To investigate this I studied DNA methylation across an ~80kb segment of the genome which is not known to be mutated in haematological malignancies. Methylation was perturbed in 35-100% of samples of DNA from individuals with a wide range of haematological malignancies but not in non-malignant haematological disorders. DNA methylation was comprehensively assessed by Southern blot analysis, classical bisulphite sequencing and using a newly developed capture bisulphite sequencing protocol. The results were also compared with analysis by MeDIP, an immunoprecipitation-based technique. These analyses provide methylation status at various levels including individual CpG resolution. This showed both gain and loss of methylation at CpG dinucleotides. Of interest, hypomethylation was most frequently seen in intergenic regions corresponding to transcription factor binding sites and areas of increased chromosome accessibility. These observations suggested that hypomethylation of the genome in haematological malignancies could arise from aberrantly expressed DNA binding proteins which, recruited to sequences in regions of open chromatin, would protect the underlying CpG dinucleotides from the methylation machinery. This, in turn, could lead to passive demethylation accumulating with increasing cell divisions. This hypothesis was tested with electrophoretic mobility shift assays using oligonucleotides representing the DNA underlying one such region. This showed that, compared to nuclear extracts from the lymphocytes of normal individuals, those from patients with CLL were enriched for a protein which binds to oligonucleotides containing the underlying sequence. Using a mass spectrometry approach, I identified a variety of proteins that may bind such regions and account for their passive demethylation in haematological malignancies.

Chronic lymphocytic leukaemia (CLL) is the most common adult leukaemia, and despite recent introduction of targeted therapies, remains incurable. An important hallmark of CLL is severe immune deficiency, including the failure to mount effective anti-tumour immune responses. This can partly be explained by insufficient antigen presentation, but also by the existence of complex CLL-induced T-cell defects. Based on the cancer immuno-editing hypothesis that the immune system not only protects a host against tumour formation but can also be compromised to actively provide a pro-tumour microenvironment, modulating cancer-induced T-cell defects could restore the full anti-tumour response and result in more durable clinical responses. The immune checkpoint molecules PD-1 (expressed on activated immune effector cells) and PD-L1 (expressed on antigen-presenting and microenvironmental cells including tumour cells) have emerged as important mediators of T-cell suppression. Several studies suggest that PD-L1/PD-1 inhibitory signalling in CLL might be overcome by the immune modulatory drug lenalidomide. Furthermore, directly targeting PDL-1/PD-1 interactions produces significant responses in solid cancers. However, similar studies are notably absent in CLL, and the effect of PDL-1/PD-1 blockade on restoring cancer-induced immune dysfunction is not understood. Transgenic Eμ-TCL1 mice have been extensively validated as an adequate preclinical model of aggressive human CLL, and our group showed their suitability to mirror T-cell defects observed in human CLL. Using the Eμ-TCL1 model, this dissertation project substantially extends our previous characterization of CLL-induced T-cell dysfunction and evaluates the functional impact of PD-L1/PD-1 inhibitory signalling both in parallel with disease development and in different microenvironments. The findings to be described here demonstrate that developing CLL is associated with specific T-cell subset alterations, phenotypic changes, and functional defects that are very similar in peripheral blood and secondary lymphoid organs. In addition to PD-L1, PD-L2 is identified as a potential mediator of inhibitory signalling in CLL. CD8+ T cells in leukaemic mice are characterised as a functionally heterogeneous population, in which subsets of cells are able to exert effector functions despite PD-1 expression. In vivo lenalidomide treatment repairs selected phenotypic alterations and immune synapse formation, and a PD-L1 IgG blocking antibody effectively controls disease and reverses global T-cell defects even in cells expressing PD-1. In sum, this work provides a strong rationale to explore PD-L1/PD-1 targeting in CLL clinical trials, potentially in combination with novel agents.

<p>Chronic lymphocytic leukemia (CLL) cells are considered to be derived from antigen-exposed B cells. To further explore the antigen-driven selection behind the leukemogenesis of CLL, we performed immunoglobulin (Ig) specificity screening of 7 CLL cell lines and 23 primary CLL clones from patient peripheral blood. We also included a recombinant monovalent monoclonal antibody (mAb) belonging to a subset of CLL cases with identical or semiidentical heavy chain complementarity determining region 3 (HCDR3) of the IGHV3-21 gene rearrangement. We found CLL mAb specificities against vimentin, filamin B, cofilin-1, proline-rich acidic protein 1, cardiolipin, oxidized low density lipoprotein and Streptococcus pneumoniae polysaccarides. These molecules are functionally associated with microbial infection and/or apoptotic cell removal. An antigen-driven selection would therefore imply that CLL B cell precursors are involved in the elimination and scavenging of pathogens and apoptotic cells, which could trigger the development of the disease.</p><p>The limited in vitro survival of CLL cells makes Epstein-Barr virus (EBV) immortalization of CLL cells a useful experimental model for studies on antibody-specificity screening. Considering the intricate procedure of EBV transformation of CLL cells and the many false cell lines used worldwide, we also wanted to characterize and evaluate the authentic origin of several previously established CLL cell lines and their normal lymphoblastoid counterparts. Three of the CLL cell lines tested were truly authentic (I83-E95, CLL-HG3 and CII), two had features of a biclonal Ig expression (232B4 and WaC3CD5+), one was only tentatively verified (PGA-1), whereas one cell line could not be verified (EHEB) due to lack of original patient cells for comparison. Two of the presumed normal lymphoblastoid cell lines tested were shown to be a neoplastic CLL clone. This study emphasizes the importance of proper cell line authentication and we will continue to verify additional cell lines not yet proven authentic.</p><p>In conclusion, we provide evidence for natural Ab production by CLL cells and suggest that these cells might be derived from B cell precursors involved in the innate immunity and, thus, providing a first-line-defence against pathogens and in elimination of apoptotic cells.</p>

Lymphocytic infiltration is a feature of basal breast cancer tumors. CXCL10 is a chemokine that was found expressed higher in basal tumor RNA compared to estrogen receptor positive tumor RNA. Both CXCL10 and its receptor CXCR3 were expressed in familial breast cancer tissues, a proportion of which have a basal phenotype. CXCL10 expression was associated with lymphocytic infiltration, and with CXCR3 expression. CXCL10 ligand and receptor were overexpressed individually or together in the human MCF7 cell line. Recombinant human CXCL10 was found to dose dependently decrease cell proliferation. CXCR3 and CXCL10-CXCR3 expressing cells had the potential for increased migration independent of CXCL10 concentration. Co-expression of both genes increased proMMP-2 levels, and conditioned media from one of these clones chemoattracted more of the CXCR3 clones, CXCL10-CXCR3 clones, and CD4+ T-lymphocytes. CXCL10 neutralization suggested that CXCL10 could play a role in this chemoattraction, though it is likely not the only factor involved.

Lymphocytic infiltration is a feature of basal breast cancer tumors. CXCL10 is a chemokine that was found expressed higher in basal tumor RNA compared to estrogen receptor positive tumor RNA. Both CXCL10 and its receptor CXCR3 were expressed in familial breast cancer tissues, a proportion of which have a basal phenotype. CXCL10 expression was associated with lymphocytic infiltration, and with CXCR3 expression. CXCL10 ligand and receptor were overexpressed individually or together in the human MCF7 cell line. Recombinant human CXCL10 was found to dose dependently decrease cell proliferation. CXCR3 and CXCL10-CXCR3 expressing cells had the potential for increased migration independent of CXCL10 concentration. Co-expression of both genes increased proMMP-2 levels, and conditioned media from one of these clones chemoattracted more of the CXCR3 clones, CXCL10-CXCR3 clones, and CD4+ T-lymphocytes. CXCL10 neutralization suggested that CXCL10 could play a role in this chemoattraction, though it is likely not the only factor involved.

Previously a t(2;14)(p13;q32) translocation was characterized in four unusually aggressive cases of B cell chronic lymphocytic leukemia (B-CLL). A gene located near the 2p13 breakpoint, B cell lymphoma/leukemia 11A (BCL11A), was shown to overexpress 3 isoforms (BCL11A-XL, L and S). Bcl11a knockout mice are severely impaired in B cell development at the early (pro-B) stage. I have further characterized BCL11A, focusing on the most abundant and evolutionarily conserved isoform, BCL11A-XL (XL). I demonstrated that XL resides in the nuclear matrix, is modified by ubiquitination, and is destabilized by B cell antigen receptor ligation. I identified domains within XL required for its localization within nuclear paraspeckles and for its transcriptional repression. While BCL11A-XL represses model promoters in non-B cells, its biologically relevant targets in B lymphocytes were unknown. I have identified and confirmed a number of XL targets which are both up- and down-regulated by XL over-expression in B cell lines. A number of these genes have been implicated in B cell function, including the V(D)J recombination activating (RAG) genes. Both RAG1 and RAG2 transcripts were up-regulated by XL. XL binds to the RAG1 promoter and RAG enhancer (Erag) in vivo as well as in vitro. Unexpectedly, XL repressed RAG1 transcription in non-B cells, indicating that additional B cell-specific factors are required for activation. Overexpression of XL in a V(D)J recombination-competent pre-B cell line markedly induced RAG expression and VDJ recombination. IRF4 and IRF8, transcription factors previously shown to be required for early B cell development, were also induced by BCL11A-XL. I propose that the early B cell progenitor block in Bcl11a knockout mice is, at least in part, a direct result of BCL11A-XL regulation of V(D)J recombination. Further experiments are required to establish how other XL targets promote B cell lineage development and how malignant transformation such as in B-CLL may corrupt BCL11A function.