Prostate cancer is the most common cancer among western men, with a significant mortality and morbidity reported for advanced metastatic disease. Current understanding of metastatic disease is limited due to difficulty of sampling as prostate cancer mainly metastasizes to bone. By analysing prostate cancer bone metastases using high density microarrays, we found a common genomic copy number loss at 6q16.1–16.2, containing the FBXL4 gene, which was confirmed in larger series of bone metastases by fluorescence in situ hybridisation (FISH). Loss of FBXL4 was also detected in primary tumours and it was highly associated with prognostic factors including high Gleason score, clinical stage, prostate-specific antigen (PSA) and extent of disease, as well as poor patient survival, suggesting that FBXL4 loss contributes to prostate cancer progression. We also demonstrated that FBXL4 deletion is detectable in circulating tumour cells (CTCs), making it a potential prognostic biomarker by ‘liquid biopsy’. In vitro analysis showed that FBXL4 plays a role in regulating the migration and invasion of prostate cancer cells. FBXL4 potentially controls cancer metastasis through regulation of ERLEC1 levels. Therefore, FBXL4 could be a potential novel prostate cancer suppressor gene, which may prevent cancer progression and metastasis through controlling cell invasion.

Histone methyltransferases (HMTs) are important epigenetic regulators of gene transcription and are disrupted at the genomic level in a spectrum of human tumours including haematological malignancies. Using high-resolution single nucleotide polymorphism (SNP) arrays, we identified recurrent deletions of the SETD2 locus in 3% (8/261) of chronic lymphocytic leukaemia (CLL) patients. Further validation in two independent cohorts showed that SETD2 deletions were associated with loss of TP53, genomic complexity and chromothripsis. With next-generation sequencing we detected mutations of SETD2 in an additional 3.8% of patients (23/602). In most cases, SETD2 deletions or mutations were often observed as a clonal event and always as a mono-allelic lesion, leading to reduced mRNA expression in SETD2-disrupted cases. Patients with SETD2 abnormalities and wild-type TP53 and ATM from five clinical trials employing chemotherapy or chemo-immunotherapy had reduced progression-free and overall survival compared with cases wild type for all three genes. Consistent with its postulated role as a tumour suppressor, our data highlight SETD2 aberration as a recurrent, early loss-of-function event in CLL pathobiology linked to aggressive disease.

Understanding the dynamics of evolution of Follicular Lymphoma (FL) clones during disease progression is important for monitoring and targeting this tumor effectively. Genetic profiling of serial FL biopsies and examples of FL transmission following bone marrow transplant suggest that this disease may evolve by divergent evolution from a common ancestor cell. However where this ancestor cell resides and how it evolves is still unclear. The analysis of the pattern of somatic hypermutation of the immunoglobulin gene (Ig) is traditionally used for tracking the physiological clonal evolution of B cells within the germinal center and allows to discriminate those cells that have just entered the germinal center and display features of ancestor cells from those B cells that keep re-circulating across different lymphoid organs. Here we investigated the pattern of somatic hypermutation of the heavy chain of the immunoglobulin gene (IgH-VH) in 4 flow-sorted B cells subpopulations belonging to different stages of differentiation, from sequential lymph node biopsies of cases displaying diverse patterns of evolution, using the GS-FLX Titanium sequencing platform. We observed an unexpectedly high level of clonality, with hundreds of distinct tumor subclones in the different subpopulations from the same sample, the majority detected at a frequency <10(-2). By using a lineage trees analysis we observed in all our FL and t-FL cases that the oligoclonal FL population was trapped in a narrow intermediate stage of maturation that maintains the capacity to undergo SHM, but was unable to further differentiate. The presence of such a complex architecture highlights challenges currently encountered in finding a cure for this disease.

Distinct patterns of DNA methylation characterize the epigenetic landscape of promyelocytic leukemia/retinoic acid receptor-α (PML-RARα)-associated acute promyelocytic leukemia (APL). We previously reported that the microRNAs (miRNAs) clustered on chromosome 14q32 are overexpressed only in APL. Here, using high-throughput bisulfite sequencing, we identified an APL-associated hypermethylation at the upstream differentially methylated region (DMR), which also included the site motifs for the enhancer blocking protein CCCTC-binding factor (CTCF). Comparing the profiles of diagnostic/remission paired patient samples, we show that hypermethylation was acquired in APL in a monoallelic manner. The cytosine guanine dinucleotide status of the DMR correlated with expression of the miRNAs following a characteristic position-dependent pattern. Moreover, a signature of hypermethylation was also detected in leukemic cells from an established transgenic PML-RARA APL mouse model at the orthologous region on chromosome 12, including the CTCF binding site located upstream from the mouse miRNA cluster. These results, together with the demonstration that the region does not show DNA methylation changes during myeloid differentiation, provide evidence that 14q32 hypermethylation is implicated in the pathogenesis of APL. We propose a model in which loss of imprinting at the 14q32 domain leads to overexpression of the miRNAs in APL.

ATM mutation and BIRC3 deletion and/or mutation have independently been shown to have prognostic significance in chronic lymphocytic leukemia. However, the relative clinical importance of these abnormalities in patients with a deletion of 11q encompassing the ATM gene has not been established. We screened a cohort of 166 patients enriched for 11q-deletions for ATM mutations and BIRC3 deletion and mutation and determined the overall and progression-free survival among the 133 of these cases treated within the UK LRF CLL4 trial. SNP6.0 profiling demonstrated that BIRC3 deletion occurred in 83% of 11q-deleted cases and always co-existed with ATM deletion. For the first time we have demonstrated that 40% of BIRC3-deleted cases have concomitant deletion and mutation of ATM. While BIRC3 mutations were rare, they exclusively occurred with BIRC3 deletion and a wildtype residual ATM allele. In 11q-deleted cases, we confirmed that ATM mutation was associated with a reduced overall and progression-free survival comparable to that seen with TP53 abnormalities, whereas BIRC3 deletion and/or mutation had no impact on overall and progression-free survival. In conclusion, in 11q-deleted patients treated with first-line chemotherapy, ATM mutation rather than BIRC3 deletion and/or mutation identifies a subgroup with a poorer outcome.

Genomic changes affecting tumour suppressor genes are fundamental to cancer. We applied SNP array analysis to a panel of testicular germ cell tumours to search for novel tumour suppressor genes and identified a frequent small deletion on 6q25.3 affecting just one gene, ZDHHC14 . The expression of ZDHHC14 , a putative protein palmitoyltransferase with unknown cellular function, was decreased at both RNA and protein levels in testicular germ cell tumours. ZDHHC14 expression was also significantly decreased in a panel of prostate cancer samples and cell lines. In addition to our findings of genetic and protein expression changes in clinical samples, inducible overexpression of ZDHHC14 led to reduced cell viability and increased apoptosis through the classic caspase‐dependent apoptotic pathway and heterozygous knockout of ZDHHC14 decreased cell colony formation ability. Finally, we confirmed our in vitro findings of the tumour suppressor role of ZDHHC14 in a mouse xenograft model, showing that overexpression of ZDHHC14 inhibits tumourigenesis. Thus, we have identified a novel tumour suppressor gene that is commonly down‐regulated in testicular germ cell tumours and prostate cancer, as well as given insight into the cellular functional role of ZDHHC14 , a potential protein palmitoyltransferase that may play a key protective role in cancer. © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Acute promyelocytic leukemia (APL) is characterized by the chromosomal translocation t(15;17) which results in the expression of the chimeric protein PML- RARα. Compared to the wild type retinoic acid receptor α (RARα), the fusion protein acquires dominant oncogenic properties and the chromosomal rearrangement is identified as the trigger of APL. However the pathogenesis of APL cannot be explained by the sole failure of RARα regulation and additional genetic and epigenetic alterations are required. We and others have shown that the microRNAs (miRNAs) clustered in the chromosome 14q32 imprinted domain and epigenetically regulated by the upstream differentially methylated regions (DMRs) are overexpressed only in APL (Dixon-McIver et al., 2008; Li et al., 2008; Valleron et al., 2012). Here, using high-throughput amplicon bisulfite sequencing (Roche 454), we characterized the DNA methylation profile of the DMRs in bone marrow/peripheral blood samples from patients with APL, other subclasses of acute myeloid leukemia (AML) and from healthy donors. Sequence reads were quality filtered and a total of 923,981 used to determine the methylation status of 202 CpGs. We identified an APL-specific hypermethylation signature (Fig. 1) at the DMR that spans the promoter of the MEG3 gene (MEG3-DMR) and partially overlaps the miRNA cluster. Hypermethylation encompassed the binding site motifs for the enhancer blocking protein CTCF. Consistent with the CTCF insulating activity, CpG methylation at the CTCF binding sites positively correlated with the expression of miRNAs (Fig. 2). Notably, no significant DNA methylation changes were detected at the intergenic imprinting control region (IG-DMR). Indeed, consistent with a scenario whereby only the genes regulated by the MEG3-DMR would be affected by the aberrant methylation, the gene expression profile performed on a cohort of 97 AML patients showed that among the imprinted genes of the domain only MEG3 was distinctively up-regulated in APL. Taking advantage of the long sequence reads obtained, we performed the haplotype analysis of the DNA methylation changes in diagnostic/remission sample pairs and demonstrated that hypermethylation arises in a mono-allelic manner in APL (Fig. 3). As the expression of the 14q32 miRNAs in the adult is normally restricted to the brain, we propose a model in which loss of imprinting (LOI) at 14q32 leads to aberrant expression of the miRNAs in APL cells. This study provides novel insights into the epigenetic characterization of APL and the mechanism underlying the deregulation of a specific cluster of miRNAs in this subtype of leukemia. The 14q32 miRNAs include species with oncogene and tumor-suppressor activity and their up-regulation may play a role in the APL pathogenesis. Further investigations are required to determine whether LOI is involved in the cancer initiation or it occurs at a later stage, possibly in association with the expression of the chimeric protein PML-RARα.Figure 1Unsupervised hierarchical cluster analysis of the CpG methylation levels. Each row represents a CpG site and each column a sample. The percentage of CpG methylation is depicted using color scales of red (CpG methylation > 50%) and green (CpG methylation < 50%). Sample group labels are indicated (APL; Control; Remission; AMLs).Figure 1. Unsupervised hierarchical cluster analysis of the CpG methylation levels. Each row represents a CpG site and each column a sample. The percentage of CpG methylation is depicted using color scales of red (CpG methylation > 50%) and green (CpG methylation < 50%). Sample group labels are indicated (APL; Control; Remission; AMLs).

Chronic lymphocytic leukemia (CLL) is associated with profound defects in immune function, resulting in failure of anti-tumor immunity and increased susceptibility to infection. We have previously demonstrated alterations in gene expression profiles of T cells from CLL patients, which translate into functional defects in T-cell immune synapse formation, motility and cytotoxicity (Gorgun et al. JCI 2005; Ramsay et al. JCI 2008, Blood 2013). However a comparison of the transcriptome of natural killer (NK) cells from CLL patients and controls has not been investigated. NK cells were isolated from the peripheral blood of patients with CLL and healthy donors, followed by gene expression profiling using the Affymetrix U133Plus2.0 platform. 117 probes showed a >2-fold decrease in expression while only 18 probes showed a >2-fold increase in expression (adjusted p-value < 0.05) in CLL NK cells compared to healthy donor NK cells. Strikingly, 52 out of the 117 significantly down-regulated probes (44.4%) were for interferon-inducible genes including STAT1 (Signal Transducers and Activator 1), SOCS1 (Suppressor of cytokine signaling 1), interferon regulatory factor genes IRF7 and IRF9, and oligoadenylate synthetase genes OAS1, OAS2, and OAS3. The majority of these genes were inducible by both type 1 and type 2 interferons. Many of these genes have been implicated in host immunity to viral infections, and so it is possible that decreased NK-cell responsiveness to interferon contributes to the increased susceptibility of CLL patients to viruses. Notably, there was also altered expression of signaling pathways in common with T cells from CLL patients, with dysregulation of the cytoskeleton genes RAB3GAP1, RAB38, and EPHA1 and down-regulation of JUN mirroring the dysregulated JNK-signaling and the altered actin cytoskeleton pathways we have found in T cells from CLL patients. These changes were not due to differences in the relative frequencies of CD56DIM and CD56BRIGHTNK cells.

Many human cancers present as multifocal lesions. Understanding the clonal origin of multifocal cancers is of both etiological and clinical importance. The molecular basis of multifocal prostate cancer has previously been explored using a limited number of isolated markers and, although independent origin is widely believed, the clonal origin of multifocal prostate cancer is still debatable. We attempted to address clonal origin using a genome‐wide copy‐number analysis of individual cancer and high‐grade prostatic intraepithelial neoplasia (HGPIN) lesions. Using Affymetrix array 6.0 copy‐number analysis, we compared the genomic changes detected in 48 individual cancer and HGPIN lesions, isolated from 18 clinically localized prostate cancer cases. Identical genomic copy‐number changes, shared by all same‐case cancer foci, were detected in all 13 informative cases displaying multiple tumor foci. In addition, individual HGPIN lesions in the two multifocal‐HGPIN cases available shared identical genomic changes. Commonly known genomic alterations, including losses at 6q15, 8p21.3‐8p21.2, 10q23.2‐10q23.31, 16q22.3, 16q23.2‐16q23.3 and 21q22.2‐21q22.3 regions and gain of 8q24.3 were the most frequently detected changes in this study and each was detected in all same‐case foci in at least one case. Microarray data were confirmed by fluorescence in situ hybridization in selected foci. Our high‐resolution genome‐wide copy‐number data suggest that many multifocal cases derive from a single prostate cancer precursor clone and that this precursor may give rise to separate HGPIN foci and may further progress to multifocal invasive prostate cancer. These findings, which demonstrate the monoclonal origin of multifocal prostate cancer, should significantly enhance our understanding of prostate carcinogenesis. © 2012 Wiley Periodicals, Inc.

Abstract Abstract 790 Several investigators have defined gene expression profiling (GEP) signatures in Diffuse Large B-cell Lymphoma (DLBCL) enriched for macrophage and stromal genes, suggesting an active innate immune response against lymphoma. We hypothesize that the malignant B-cells drive tumor-associated macrophage (TAM) dysfunction in a subset of patients with DLBCL which is relevant for their biology and prognosis. We performed GEP on TAM from diagnostic DLBCL in order to recognise key genes and pathways open to functional validation. Single cell suspensions from 8 DLBCL and 8 reactive lymph nodes were used in this study. TAMs were flow sorted using CD36 expression. cDNA synthesis and amplification was performed using the Nugen Ovation Pico WTA system and the Affymetrix GeneChip human gene 1.0 ST platform was used. We used bioinformatics analysis of GEP data from DLBCL whole tumors, DLBCL purified B-cells, in vitro manipulated macrophages and other immune cells in order to define macrophage-enriched genes as well as specific M1/M2 signatures. We identified a 221 gene signature that significantly distinguished DLBCL TAMs from control macrophages, with 165 genes upregulated and 56 genes downregulated. Moreover, a comparative transcriptome analysis of 22 diverse immune cell phenotypes/activation states (IRIS: GSE22886) revealed that 26% of these genes are highly macrophage-enriched. Gene Ontology analysis revealed an over-representation for transcripts involved in inflammatory response (p 6.8×10−23), wound healing (p 1.9×10−20), chemotaxis (p 3.2 ×10−9), and cell motility (p 1.7×10−7). Upregulated genes in TAMs included well known M1 (complement components, CXCL9 or CXCL10) as well as M2 genes (MSR, CD163 or MARCO) (Table 1). In our signature, there was enrichment for M1 compared to M2 genes as defined by bioinformatics analysis. TAMs showed overexpression of the CSF1R gene as well as the chemokines CCL2 and CCL5, suggesting an autocrine feed-back loop of macrophage chemotaxis and survival in DLBCL. Moreover, TAMs showed upregulation of the lymphocyte attractants CCL20, CXCL9 and CXCL10, together with T-cell immunosupressants indoleamine 2,3-dioxygenase 1 and PD-L1, which would support a role for macrophages in T-cell recruitment and dysfunction in DLBCL. We also saw strong upregulation of 7 metallothionein isoforms in TAMs. These are proteins known to be expressed in macrophages and linked to response to oxidative damage, modulation of inflammation and cell proliferation. However their role in cancer microenvironment is unclear. We describe for the first time the GEP from DLBCL TAMs. The TAM transcriptome has partial overlapping genes with both M1 and M2 gene signatures, but also has a characteristic GEP potentially driven by their presence in the DLBCL microenvironment. Although further molecular and functional validation is required, this data provides a platform of genes which serve as excellent candidates for future exploration to understand DLBCL pathogenesis and to define new therapeutic targets. Table 1: Genes of particular interest represented in our TAM signature. Probe collapse was done using the highest expression. The Benjamini-Hochberg multiple hypothesis test was used to determine significance (FDR 0.05). Gene IDs Gene description Log2 Fold Change Adjusted p value MT1E-H, L, M, X, MT2A metallothionein 1E-H, 1M, 1X, 2A 2.3 – 4.4 0.00145 - 0.00017 C1QA, B and C complement component 1, q subcomponent, A, B and C chains 3.1 – 3.6 0.00136 - 0.00255 C2 complement component 2 3.2 0.00136 CCL2, 4, 5, 8, 20 chemokine (C-C motif) ligand 2, 4, 5, 8 and 20 2.4 - 3.7 0.046 - 0.00130 CD163 CD163 molecule 4.6 0.00025 CD14 CD14 molecule 3.4 0.00091 CD274 CD274 molecule 3.7 0.00447 CSF1R colony stimulating factor 1 receptor 2.1 0.00886 CXCL9-11 chemokine (C-X-C motif) ligand 9, 10 and 11 4.2 – 4.4 0.012 - 0.00158 FCGR1B Fc fragment of IgG, high affinity Ib, receptor (CD64) 4.9 0.00091 FCGR2A Fc fragment of IgG, low affinity IIa, receptor (CD32) 3.3 0.00139 FCGR3A Fc fragment of IgG, low affinity IIIa, receptor (CD16a) 5.2 0.00011 IDO1 indoleamine 2,3-dioxygenase 1 4.8 0.00232 MARCO macrophage receptor with collagenous structure 2.6 0.02029 MSR1 macrophage scavenger receptor 1 3.7 0.01467 Disclosures: Gribben: Celgene: Honoraria; Roche: Honoraria; Pharmacyclics: Honoraria; GSK: Honoraria; Mundipharma: Honoraria; Gilead: Honoraria.

Early genetic events in the development of high-grade serous ovarian cancer (HGSOC) may define the molecular basis of the profound structural and numerical instability of chromosomes in this disease. To discover candidate genetic changes we sequentially passaged cells from a karyotypically normal hTERT immortalised human ovarian surface epithelial line (IOSE25) resulting in the spontaneous formation of colonies in soft agar. Cell lines transformed ovarian surface epithelium 1 and 4 (TOSE 1 and 4) established from these colonies had an abnormal karyotype and altered morphology, but were not tumourigenic in immunodeficient mice. TOSE cells showed loss of heterozygosity (LOH) at TP53, increased nuclear p53 immunoreactivity and altered expression profile of p53 target genes. The parental IOSE25 cells contained a missense, heterozygous R175H mutation in TP53, whereas TOSE cells had LOH at the TP53 locus with a new R273H mutation at the previous wild-type TP53 allele. Cytogenetic and array CGH analysis of TOSE cells also revealed a focal genomic amplification of CXCR4, a chemokine receptor commonly expressed by HGSOC cells. TOSE cells had increased functional CXCR4 protein and its abrogation reduced epidermal growth factor receptor (EGFR) expression, as well as colony size and number. The CXCR4 ligand, CXCL12, was epigenetically silenced in TOSE cells and its forced expression increased TOSE colony size. TOSE cells had other cytogenetic changes typical of those seen in HGSOC ovarian cancer cell lines and biopsies. In addition, enrichment of CXCR4 pathway in expression profiles from HGSOC correlated with enrichment of a mutated TP53 gene expression signature and of EGFR pathway genes. Our data suggest that mutations in TP53 and amplification of the CXCR4 gene locus may be early events in the development of HGSOC, and associated with chromosomal instability.

Abstract Tumor suppressor genes (TSGs) play critical roles in preventing tumorigenesis and they are frequently inactivated in tumours. Recently developed high-density microarrays can detect subchromosomal deletions, recurrence of which usually indicates the location of TSGs within the deleted region. We analyzed testicular germ cell tumour (TGCT) clinical samples using SNP arrays and found a frequent small deletion on the region 6q25.3 containing only one known gene, ZDHHC14. While its cellular function is unknown, ZDHHC14 belongs to the recently discovered DHHC family, which are predicted to be involved in protein palmitoylation, a reversible lipid modification that regulates membrane tethering for key proteins in cell signaling, cancer, neuronal transmission, and membrane trafficking. Consistently, we found a dramatic under-expression of ZDHHC14 mRNA and protein in TGCTs, and this associated with chemoresistance. Oncomine database mining showed that ZDHHC14 is also under-expressed in lymphoma, liposarcoma, brain, kidney, lung and colorectal cancers. Thus, it appears that ZDHHC14 downregulation may be involved in other cancers. We studied ZDHHC14 expression in prostate cancer (PCa), detecting a decrease at mRNA and protein level. We also detected that ZDHHC14 mRNA was downregulated in a pilot study on breast cancer samples. As genomic loss of the ZDHHC14 region was only detected in a small number of PCa samples, we checked whether promoter hypermethylation was the cause for ZDHHC14 downregulation. However, no changes in methylation status were found. We then sequenced the whole genomic region surrounding ZDHHC14 by next generation sequencing in TGCTs and PCa and found several mutations in the promoter, the coding region, as well as in intronic regions. Finally, we tested the function of ZDHHC14 in cell-based studies. We generated a 293 T-REx tetracycline inducible ZDHHC14 overexpressing stable cell line, which showed that ZDHHC14 overexpression decreased cell viability. The induction of apoptosis by ZDHHC14 overexpression was detected both by FACS and caspase 7 and PARP cleavage analyses. This was confirmed by transient ZDHHC14 overexpression in the PCa cell line 22RV1. In vivo we xenografted mice using both tetracycline inducible ZDHHC14 overexpressing 293 T-REx cells and control cells transfected with the empty vector. ZDHHC14 expression was induced by tetracycline at the beginning of inoculation and we detected that ZDHHC14 overexpression blocked tumour initiation completely. In conclusion, these results implicate ZDHHC14 as a tumour suppressor gene commonly inactivated in human cancers, indicating that it might exert its tumor suppressor role through the induction of programmed cell death. This is the first study showing the involvement of ZDHHC14 in a specific pathway, the classic caspase-dependent apoptosis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4858. doi:1538-7445.AM2012-4858

Abstract Abstract 658 In CLL, 11q23 deletion (encompassing the ATM gene) predicts a poor response to initial treatment with DNA damaging agents that can be ameliorated by the addition of anti-CD20 antibodies. 30–40% of 11q-deleted CLL cases have an inactivating ATM mutation on the remaining allele. In the UK CLL4 trial, bi-allelic ATM abnormalities were associated with a shorter PFS than those with mono-allelic ATM loss. The additional observation of a shorter PFS in cases with mono-allelic ATM loss compared to those with an ATM mutation in the absence of an 11q deletion suggests a potential pathogenic role for other genes within the 11q deleted region. A recent study provides evidence that loss and/or mutation of BIRC3, located at 11q22, that encodes a negative regulator of non-canonical NFkB signalling, may be an independent marker of poor outcome in CLL. In order to provide more data on the relative frequency and clinical significance of ATM and BIRC3 loss and mutation, we have screened a cohort of previously untreated patients (n=264) enriched for cases with an 11q23 deletion detected by FISH (n=80) using SNP6.0 profiling (n = 264) and HRM-PCR/DHPLC & sequencing of the ATM (all exons; n=130), and BIRC3 (mutation hotspots: exons 5,7,10; n=258) genes. SNP6.0 copy number analysis identified 112 deletions on chromosome 11 in 76 cases, of which 69 had deletions including ATM (27.8Mb; 521kb–58Mb). Although a 416Kb Minimally Deleted Region (MDR) was defined (107.5–107.9Mb; hg18) containing 6 genes including ATM, in only 4% of 11q-deleted cases was a deletion confined to the MDR and invariably 11q23 deletions were much larger. The entire BIRC3 gene was only deleted in cases with ATM loss, and always within a single deletion event encompassing both genes. BIRC3 was deleted in 57 11q-deleted cases (83%) and in 4 cases (6%) the proximal deletion breakpoint resulted in partial deletion of BIRC3 that is predicted to cause protein truncation by removal of the RING domain. Additional deletion events not including ATM were identified in our series, but none of these encompassed BIRC3. In ATM deleted and non-deleted cases, the frequency of an ATM mutation of the retained allele was 38 and 21% respectively. In 11q-deleted cases with a wild-type ATM allele, three harboured both a deletion and mutation of BIRC3 (5% of BIRC3-deleted CLL). Mutations were located in either the CARD (frameshift mutation) or RING domains (STOP codon point mutation & 3bp indel) of the protein, and two are predicted to eliminate the C-terminal RING domain responsible for proteasomal degradation of MAP3K14. These three cases were also positive for trisomy 12, lacked an ATM mutation or TP53 abnormality, and two had mutations within the PEST domain of NOTCH1. Patients with deletion and mutation of BIRC3 were all treated (FC or F) within 39 months (mean TFS = 16 mths; range: 1–39mths) from diagnosis and after 9 years of follow up only one patient survived (mean OS = 83 mths). In conclusion, given the concordance between ATM and BIRC3 loss, and the low incidence of BIRC3 mutations, much larger studies would be required to evaluate whether disruption of BIRC3 has independent prognostic significance in an untreated cohort. Disclosures: No relevant conflicts of interest to declare.