This review highlights a decade of investigations into the role of CD38 in CLL. CD38 is accepted as a dependable marker of unfavorable prognosis and as an indicator of activation and proliferation of ...cells when tested. Leukemic clones with higher numbers of CD38+ cells are more responsive to BCR signaling and are characterized by enhanced migration. In vitro activation through CD38 drives CLL proliferation and chemotaxis via a signaling pathway that includes ZAP-70 and ERK1/2. Finally, CD38 is under a polymorphic transcriptional control after external signals. Consequently, CD38 appears to be a global molecular bridge to the environment, promoting survival/proliferation over apoptosis. Together, this evidence contributes to the current view of CLL as a chronic disease in which the host's microenvironment promotes leukemic cell growth and also controls the sequential acquisition and accumulation of genetic alterations. This view relies on the existence of a set of surface molecules, including CD38, which support proliferation and survival of B cells on their way to and after neoplastic transformation. The second decade of studies on CD38 in CLL will tell if the molecule is an effective target for antibody-mediated therapy in this currently incurable leukemia.
The engagement of the B cell receptor (BcR) on the surface of leukemic cells represents a key event in chronic lymphocytic leukemia (CLL) since it can lead to the maintenance and expansion of the ...neoplastic clone. This notion was initially suggested by observations of the CLL BcR repertoire and of correlations existing between certain BcR features and the clinical outcomes of single patients. Based on these observations, tyrosine kinase inhibitors (TKIs), which block BcR signaling, have been introduced in therapy with the aim of inhibiting CLL cell clonal expansion and of controlling the disease. Indeed, the impressive results obtained with these compounds provided further proof of the role of BcR in CLL. In this article, the key steps that led to the determination of the role of BcR are reviewed, including the features of the CLL cell repertoire and the fine mechanisms causing BcR engagement and cell signaling. Furthermore, we discuss the biological effects of the engagement, which can lead to cell survival/proliferation or apoptosis depending on certain intrinsic cell characteristics and on signals that the micro-environment can deliver to the leukemic cells. In addition, consideration is given to alternative mechanisms promoting cell proliferation in the absence of BcR signaling, which can explain in part the incomplete effectiveness of TKI therapies. The role of the BcR in determining clonal evolution and disease progression is also described. Finally, we discuss possible models to explain the selection of a special BcR set during leukemogenesis. The BcR may deliver activation signals to the cells, which lead to their uncontrolled growth, with the possible collaboration of other still-undefined events which are capable of deregulating the normal physiological response of B cells to BcR-delivered stimuli.
The human
TP53
locus, located on the short arm of chromosome 17, encodes a tumour suppressor protein which functions as a tetrameric transcription factor capable of regulating the expression of a ...plethora of target genes involved in cell cycle arrest, apoptosis, DNA repair, autophagy, and metabolism regulation.
TP53
is the most commonly mutated gene in human cancer cells and
TP53
germ-line mutations are responsible for the cancer-prone Li-Fraumeni syndrome. When mutated, the
TP53
gene generally presents missense mutations, which can be distributed throughout the coding sequence, although they are found most frequently in the central DNA binding domain of the protein.
TP53
mutations represent an important prognostic and predictive marker in cancer. The presence of a
TP53
mutation does not necessarily imply a complete P53 inactivation; in fact, mutant P53 proteins are classified based on the effects on P53 protein function. Different models have been used to explore these never-ending facets of
TP53
mutations, generating abundant experimental data on their functional impact. Here, we briefly review the studies analysing the consequences of
TP53
mutations on P53 protein function and their possible implications for clinical outcome. The focus shall be on Chronic Lymphocytic Leukemia (CLL), which also has generated considerable discussion on the role of
TP53
mutations for therapy decisions.
Chronic lymphocytic leukemia (CLL) is the most frequent leukemia in Western countries. Although characterized by the progressive expansion and accumulation of leukemic B cells in peripheral blood, ...CLL cells develop in protective niches mainly located within lymph nodes and bone marrow. Multiple interactions between CLL and microenvironmental cells may favor the expansion of a B cell clone, further driving immune cells toward an immunosuppressive phenotype. Here, we summarize the current understanding of bone tissue alterations in CLL patients, further addressing and suggesting how the multiple interactions between CLL cells and osteoblasts/osteoclasts can be involved in these processes. Recent findings proposing the disruption of the endosteal niche by the expansion of a leukemic B cell clone appear to be a novel field of research to be deeply investigated and potentially relevant to provide new therapeutic approaches.
Chronic lymphocytic leukemia (CLL) is characterized by the progressive expansion of B lymphocytes CD5+/CD23+ in peripheral blood, lymph-nodes, and bone marrow. The pivotal role played by the ...microenvironment in disease pathogenesis has become increasingly clear. We demonstrated that bone marrow stromal cells and trabecular bone cells sustain survival of leukemic B cells through the production of hepatocyte growth factor (HGF). Indeed the trans-membrane kinase receptor for HGF, c-MET, is expressed on CLL cells and STAT3 TYR
or AKT phosphorylation is induced after HGF/c-MET interaction. We have further observed that c-MET is also highly expressed in a peculiar type of cells of the CLL-microenvironment showing nurturing features for the leukemic clone (nurse-like cells: NLCs). Since HGF treatment drives monocytes toward the M2 phenotype and NLCs exhibit features of tumor associated macrophages of type 2 we suggested that HGF, released either by cells of the microenvironment or leukemic cells, exerts a double effect: i) enhances CLL cells survival and ii) drives differentiation of monocytes-macrophages to an oriented immune suppressive phenotype. We here discuss how paracrine, but also autocrine production of HGF by malignant cells, may favor leukemic clone expansion and resistance to conventional drug treatments in CLL, as well as in other hematological malignancies. Novel therapeutic approaches aimed to block HGF/c-MET interactions are further proposed.
B-cell chronic lymphocytic leukemia (CLL) results from accumulation of leukemic cells that are subject to iterative re-activation cycles and clonal expansion in lymphoid tissues. The effects of the ...well-tolerated alkaloid Berberine (BRB), used for treating metabolic disorders, were studied on ex-vivo leukemic cells activated in vitro by microenvironment stimuli. BRB decreased expression of survival/proliferation-associated molecules (e.g. Mcl-1/Bcl-xL) and inhibited stimulation-induced cell cycle entry, irrespective of TP53 alterations or chromosomal abnormalities. CLL cells rely on oxidative phosphorylation for their bioenergetics, particularly during the activation process. In this context, BRB triggered mitochondrial dysfunction and aberrant cellular energetic metabolism. Decreased ATP production and NADH recycling, associated with mitochondrial uncoupling, were not compensated by increased lactic fermentation. Antioxidant defenses were affected and could not correct the altered intracellular redox homeostasis. The data thus indicated that the cytotoxic/cytostatic action of BRB at 10-30 μM might be mediated, at least in part, by BRB-induced impairment of oxidative phosphorylation and the associated increment of oxidative damage, with consequent inhibition of cell activation and eventual cell death. Bioenergetics and cell survival were instead unaffected in normal B lymphocytes at the same BRB concentrations. Interestingly, BRB lowered the apoptotic threshold of ABT-199/Venetoclax, a promising BH3-mimetic whose cytotoxic activity is counteracted by high Mcl-1/Bcl-xL expression and increased mitochondrial oxidative phosphorylation. Our results indicate that, while CLL cells are in the process of building their survival and cycling armamentarium, the presence of BRB affects this process.
B cell receptor Immunoglobulin (BcR IG) repertoire of Chronic Lymphocytic Leukemia (CLL) is characterized by the expression of quasi-identical BcR IG. These are observed in approximately 30% of ...patients, defined as stereotyped receptors and subdivided into subsets based on specific VH CDR3 aa motifs and phylogenetically related IGHV genes. Although relevant to CLL ontogeny, the distribution of CLL-biased stereotyped immunoglobulin rearrangements (CBS-IG) in normal B cells has not been so far specifically addressed using modern sequencing technologies. Here, we have investigated the presence of CBS-IG in splenic B cell subpopulations (s-BCS) and in CD5
and CD5
B cells from the spleen and peripheral blood (PB).
Fractionation of splenic B cells into 9 different B cell subsets and that of spleen and PB into CD5
and CD5
cells were carried out by FACS sorting. cDNA sequences of BcR IG gene rearrangements were obtained by NGS. Identification of amino acidic motifs typical of CLL stereotyped subsets was carried out on IGHV1-carrying gene sequences and statistical evaluation has been subsequently performed to assess stereotypes distribution.
CBS-IG represented the 0.26% average of IGHV1 genes expressing sequences, were detected in all of the BCS investigated. CBS-IG were more abundant in splenic and circulating CD5
B (0.57%) cells compared to CD5
B cells (0.17%). In all instances, most CBS IG did not exhibit somatic hypermutation similar to CLL stereotyped receptors. However, compared to CLL, they exhibited a different CLL subset distribution and a broader utilization of the genes of the IGHV1 family.
CBS-IG receptors appear to represent a part of the "public" BcR repertoire in normal B cells. This repertoire is observed in all BCS excluding the hypothesis that CLL stereotyped BcR accumulate in a specific B cell subset, potentially capable of originating a leukemic clone. The different relative representation of CBS-IG in normal B cell subgroups suggests the requirement for additional selective processes before a full transformation into CLL is achieved.
Bone skeletal alterations are no longer considered a rare event in chronic lymphocytic leukemia (CLL), especially at more advanced stages of the disease. This study is aimed at elucidating the ...mechanisms underlying this phenomenon. Bone marrow stromal cells, induced to differentiate toward osteoblasts in osteogenic medium, appeared unable to complete their maturation upon co-culture with CLL cells, CLL-cell-derived conditioned media (CLL-cm) or CLL-sera (CLL-sr). Inhibition of osteoblast differentiation was documented by decreased levels of RUNX2 and osteocalcin mRNA expression, by increased osteopontin and DKK-1 mRNA levels, and by a marked reduction of mineralized matrix deposition. The addition of neutralizing TNFα, IL-11 or anti-IL-6R monoclonal antibodies to these cocultures resulted in restoration of bone mineralization, indicating the involvement of these cytokines. These findings were further supported by silencing TNFα, IL-11 and IL-6 in leukemic cells. We also demonstrated that the addition of CLL-cm to monocytes, previously stimulated with MCSF and RANKL, significantly amplified the formation of large, mature osteoclasts as well as their bone resorption activity. Moreover, enhanced osteoclastogenesis, induced by CLL-cm, was significantly reduced by treating cultures with the anti-TNFα monoclonal antibody infliximab. An analogous effect was observed with the use of the BTK inhibitor, ibrutinib. Interestingly, CLL cells co-cultured with mature osteoclasts were protected from apoptosis and upregulated Ki-67. These experimental results parallel the direct correlation between amounts of TNFα in CLL-sr and the degree of compact bone erosion that we previously described, further strengthening the indication of a reciprocal influence between leukemic cell expansion and bone structure derangement.
Chronic lymphocytic leukaemia (CLL) is characterised by a heterogeneous clinical course. Such heterogeneity is associated with a number of markers, including TP53 gene inactivation. While TP53 gene ...alterations determine resistance to chemotherapy, it is not clear whether they can influence early disease progression. To clarify this issue, TP53 mutations and deletions of the corresponding locus del(17p) were evaluated in 469 cases from the O-CLL1 observational study that recruited a cohort of clinically and molecularly characterised Binet stage A patients. Twenty-four cases harboured somatic TP53 mutations accompanied by del(17p) in 9 cases, 2 patients had del(17p) only, and 5 patients had TP53 germ-line variants. While del(17p) with or without TP53 mutations was capable of significantly predicting the time to first treatment, a reliable measure of disease progression, TP53 mutations were not. This was true for cases with high or low variant allele frequency. The lack of predictive ability was independent of the functional features of the mutant P53 protein in terms of transactivation and dominant negative potential. TP53 mutations alone were more frequent in patients with mutated IGHV genes, whereas del(17p) was associated with the presence of adverse prognostic factors, including CD38 positivity, unmutated-IGHV gene status, and NOTCH1 mutations.
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