Chronic lymphocytic leukaemia (CLL) is a malignancy of CD5+ B cells that is characterized by the accumulation of small, mature-appearing lymphocytes in the blood, marrow and lymphoid tissues. Signalling via surface immunoglobulin, which constitutes the major part of the B cell receptor, and several genetic alterations play a part in CLL pathogenesis, in addition to interactions between CLL cells and other cell types, such as stromal cells, T cells and nurse-like cells in the lymph nodes. The clinical progression of CLL is heterogeneous and ranges from patients who require treatment soon after diagnosis to others who do not require therapy for many years, if at all. Several factors, including the immunoglobulin heavy-chain variable region gene (IGHV) mutational status, genomic changes, patient age and the presence of comorbidities, should be considered when defining the optimal management strategies, which include chemotherapy, chemoimmunotherapy and/or drugs targeting B cell receptor signalling or inhibitors of apoptosis, such as BCL-2. Research on the biology of CLL has profoundly enhanced our ability to identify patients who are at higher risk for disease progression and our capacity to treat patients with drugs that selectively target distinctive phenotypic or physiological features of CLL. How these and other advances have shaped our current understanding and treatment of patients with CLL is the subject of this Primer.

IntroductionThe division of chronic lymphocytic leukemia (CLL) into 2 major subsets, based on the presence or absence of a significant level of somatic mutations in the immunoglobulin variable (V) region genes has had a major effect on our understanding of this B-cell malignancy. [1][2][3] The difference in clinical behavior, with unmutated CLL (U-CLL) showing a worse prognosis, is clearly relevant for clinical management, and has led to an intensive search for more easily measurable markers that parallel V-gene status. Meanwhile the subtle differences in the biology of the tumor cells that dictate the variable course are being sought. Gene expression analysis detected up-regulation of several cell cycle-associated genes in U-CLL. 4 A powerful discriminator was identified as the protein tyrosine kinase -associated protein 70 (ZAP-70), with a 4-to 5-fold increase in U-CLL. 5 Expression at the protein level was also shown to be highly associated with U-CLL, 6 and measurement by flow cytometry appears to provide a clinically relevant surrogate marker for prognosis. 7 ZAP-70 is a member of the Syk family of tyrosine kinases and is known to be a critical component of the T-cell receptor signaling pathway. 8 It was an unexpected component of a B-cell malignancy because it was thought to be confined to T cells and natural killer (NK) cells. 9 However, ZAP-70 can be expressed in normal B cells, 9 and the high level of expression in U-CLL, but not in mutated CLL (M-CLL), added to the interest in possible differences in signaling pathways between the subsets.The B-cell receptor (BCR) is critical for survival of normal peripheral B cells. 10 It is also likely to have a role in maintenance or growth of tumors derived from mature B cells, which are rarely sIg Ϫ . In CLL, levels are low compared to normal B lymphocytes and to other B-cell malignancies. Based on observations of self-reactive B cells in double transgenic mice continuously expressing antigen, 11 it has been suggested that the low levels reflect an anergic state consequent on interaction with antigen in the absence of T-cell help. 12 However, no direct evidence for this had been obtained.The BCR includes sIg and the Ig-␣/Ig-␤ heterodimer (CD79a and CD79b) associated noncovalently in a 1:1 ratio. 13 Following engagement of antigen, receptors aggregate leading to phosphorylation of the Ig-␣/Ig-␤ ITAM motifs by Src-family tyrosine kinases, including Lyn. 14 Recruitment and phosphorylation of other kinases, with Syk being an important component, then activates intracellular signaling cascades. Phosphorylation of Syk therefore provides an indicator of membrane proximal events that depend on the structural integrity and oligomeric form of the BCR. It is this ability to signal via Ig-␣/Ig-␤ that is critical for survival of mature normal B cells. 15 We 16 and others 17 have reported that this early response to ligation of sIgM in CLL varies between the subsets, with an increased tendency for U-CLL to phosphorylate Syk. A parallel phosphorylation of ZAP-70 with recruitmen...

The mutational status of tumor immunoglobulin V H genes is providing a powerful prognostic marker for chronic lymphocytic leukemia (CLL), with patients having tumors expressing unmutated V H genes being in a less favorable subset. However, the biologic differences correlating with

IntroductionIf we are to exploit biologic insights for new therapies of hematologic malignancies, it is important to consider 2 distinct features of the target tumor: (1) the developmental process, by which a normal cell becomes transformed into an established tumor; and (2) the susceptibility or resistance of the malignant cells to current therapies. Most investigators do not separate these 2 features, focusing only on the link between the particular aspect being studied and clinical outcome. For example, in B-cell lymphoma, gene expression profiles have been used to predict survival, an outcome more likely to be determined by susceptibility to treatment than by the pathogenic process. 1 In many cases, this restricted view is inevitable because hematologic malignancies are often treated quite quickly, making the connection between cellular features and the natural history of the tumor difficult to analyze.Among B-cell malignancies, chronic lymphocytic leukemia (CLL) is a shining exception because its relatively indolent nature enables detailed investigation of tumor cells, often in the absence of treatment, as well as observation of tumor behavior over time. This window of opportunity has facilitated the identification of prognostic factors that relate to pathogenesis. It is even possible now to detect minor clonal expansions, defined as monoclonal B-cell lymphocytoses, in ϳ 3% of healthy persons, potentially revealing the very early stages of CLL. 2 In CLL, there is the added advantage of availability of tumor cells from blood, although conclusions based on this compartment have to be tempered by the fact that critical proliferative events occur in tissue sites.There is now strong evidence that signaling via the B-cell receptor (BCR) plays a major role in the development of CLL and that it determines the variable clinical behavior. In this Perspective, we discuss the functional significance of the BCR in CLL and we describe strategies to target BCR signaling as a new therapeutic approach. Insights into pathogenesis from the expressed IgB-cell malignancies offer a major advantage to investigators, in that the immunoglobulin (Ig) component of the BCR has unique molecular features that mark the tumor cell and reveal the nature of the B cell of origin. 3 Most cases of CLL express IgM and IgD, and it is now clear that the disease can be divided into 2 main subsets, based on whether the tumor arose from a B cell before initiation of somatic hypermutation in Ig variable (V) region genes (unmutated [U] CLL) or after this process had taken place and then stopped (mutated [M] CLL). The rather dramatic difference in tumor behavior, with U-CLL being generally more aggressive than M-CLL, 4,5 was unexpected, although perhaps it should not have been, given the clinical differences between other B-cell tumor categories.In CLL, the Ig expressed at the cell surface is rarely lost, indicating an essential influence on the tumor cell. Because the IGHVHDHJ and IGLVLJ sequences, and the isotype, reflect the normal counterpart, it i...

Conclusions: These experiments elucidate a mechanism by which the DR in pancreatic cancer may form and, via the collagen within it, promote the malignant phenotype of pancreatic cancer cells, suggesting significant detriment to the host.

Mcl-1 is a Bcl-2 family protein which can act as an apical molecule in apoptosis control, promoting cell survival by interfering at an early stage in a cascade of events leading to release of cytochrome c from mitochondria. Mcl-1 has a short half life and is a highly regulated protein, induced by a wide range of survival signals and also rapidly down regulated during apoptosis. Mcl-1 can also readily be cleaved by caspases during apoptosis to produce a cell death promoting molecule. The multiple levels of control of Mcl-1 expression suggest that Mcl-1 plays a critical role in controlling life and death decisions in response to rapidly changing environmental cues and Mcl-1 is required for embryonic development and the function of the immune system. Expression of Mcl-1 may be useful in informing decision making in the treatment of various cancers, and countering Mcl-1 function may be an attractive therapeutic strategy in malignancy, inflammatory conditions and infectious disease where Mcl-1 may play a major role in suppressing apoptosis.

Hypoxia inducible factor-1 (HIF-1) is a heterodimeric transcription factor that acts as the master regulator of cellular response to reduced oxygen levels, thus playing a key role in the adaptation, survival, and progression of tumors. Here we report cyclo-CLLFVY, identified from a library of 3.2 million cyclic hexapeptides using a genetically encoded high-throughput screening platform, as an inhibitor of the HIF-1α/HIF-1β protein–protein interaction in vitro and in cells. The identified compound inhibits HIF-1 dimerization and transcription activity by binding to the PAS-B domain of HIF-1α, reducing HIF-1-mediated hypoxia response signaling in a variety of cell lines, without affecting the function of the closely related HIF-2 isoform. The reported cyclic peptide demonstrates the utility of our high-throughput screening platform for the identification of protein–protein interaction inhibitors, and forms the starting point for the development of HIF-1 targeted cancer therapeutics.

Follicular lymphoma is an incurable B-cell malignancy1 characterized by the t(14;18) and mutations in one or more components of the epigenome2,3. Whilst frequent gene mutations in signaling pathways, including JAK-STAT, NOTCH and NF-κB, have also been defined2-7, the spectrum of these mutations typically overlap with the closely-related diffuse large B cell lymphoma (DLBCL)6-13. A combination of discovery exome and extended targeted sequencing revealed recurrent somatic mutations in RRAGC uniquely enriched in FL patients (17%). More than half of the mutations preferentially co-occurred with ATP6V1B2 and ATP6AP1 mutations, components of the vacuolar H+-adenosine triphosphate ATPase (v-ATPase) known to be necessary for amino acid-induced mTORC1 activation. The RagC mutants increased raptor binding whilst rendering mTORC1 signaling resistant to amino acid deprivation. Collectively, the activating nature of the RRAGC mutations, their existence within the dominant clone and stability during disease progression supports their potential as an excellent candidate to be therapeutically exploited.