ABCG2 is a direct transcriptional target of hedgehog signaling and involved in stroma-induced drug tolerance in diffuse large B-cell lymphoma.

Successful treatment of diffuse large B-cell lymphoma (DLBCL) is frequently hindered by the development of resistance to conventional chemotherapy resulting in disease relapse and high mortality. High expression of antiapoptotic and/or drug transporter proteins induced by oncogenic signaling pathways has been implicated in the development of chemoresistance in cancer. Previously, our studies showed that high expression of adenosine triphosphate-binding cassette drug transporter ABCG2 in DLBCL correlated inversely with disease- and failure-free survival. In this study, we have implicated activated hedgehog (Hh) signaling pathway as a key factor behind high ABCG2 expression in DLBCL through direct upregulation of ABCG2 gene transcription. We have identified a single binding site for GLI transcription factors in the ABCG2 promoter and established its functionality using luciferase reporter, site-directed mutagenesis and chromatin-immunoprecipitation assays. Furthermore, in DLBCL tumor samples, significantly high ABCG2 and GLI1 levels were found in DLBCL tumors with lymph node involvement in comparison with DLBCL tumor cells collected from pleural and/or peritoneal effusions. This suggests a role for the stromal microenvironment in maintaining high levels of ABCG2 and GLI1. Accordingly, in vitro co-culture of DLBCL cells with HS-5 stromal cells increased ABCG2 mRNA and protein levels by paracrine activation of Hh signaling. In addition to ABCG2, co-culture of DLBCL cells with HS-5 cells also resulted in increase expression of the antiapoptotic proteins BCL2, BCL-xL and BCL2A1 and in induced chemotolerance to doxorubicin and methotrexate, drugs routinely used for the treatment of DLBCL. Similarly, activation of Hh signaling in DLBCL cell lines with recombinant Shh N-terminal peptide resulted in increased expression of BCL2 and ABCG2 associated with increased chemotolerance. Finally, functional inhibition of ABCG2 drug efflux activity with fumitremorgin C or inhibition of Hh signaling with cyclopamine-KAAD abrogated the stroma-induced chemotolerance suggesting that targeting ABCG2 and Hh signaling may have therapeutic value in overcoming chemoresistance in DLBCL.

Activation of the p53 pathway by the MDM2 inhibitor nutlin-3a overcomes BCL2 overexpression in a preclinical model of diffuse large B-cell lymphoma associated with t(14;18)(q32;q21).

p53 is frequently wild type (wt) in diffuse large B-cell lymphoma (DLBCL) associated with t(14;18)(q32;q21) that overexpresses BCL2. Nutlin-3a is a small molecule that activates the p53 pathway by disrupting p53-MDM2 interaction. We show that nutlin-3a activates p53 in DLBCL cells associated with t(14;18)(q32;q21), BCL2 overexpression and wt p53, resulting in cell cycle arrest and apoptosis. Nutlin-3a treatment had similar effects on DLBCL cells of activated B-cell phenotype with wt p53. Cell cycle arrest was associated with upregulation of p21. Nutlin-3a-induced apoptosis was accompanied by BAX and PUMA upregulation, BCL-XL downregulation, serine-70 dephosphorylation of BCL2, direct binding of BCL2 by p53, caspase-9 upregulation and caspase-3 cleavage. Cell death was reduced when p53-dependent transactivation activity was inhibited by pifithrin-α (PFT-α), or PFT-µ inhibited direct p53 targeting of mitochondria. Nutlin-3a sensitized activation of the intrinsic apoptotic pathway by BCL2 inhibitors in t(14;18)-positive DLBCL cells with wt p53, and enhanced doxorubicin cytotoxicity against t(14;18)-positive DLBCL cells with wt or mutant p53, the latter in part via p73 upregulation. Nutlin-3a treatment in a xenograft animal lymphoma model inhibited growth of t(14;18)-positive DLBCL tumors, associated with increased apoptosis and decreased proliferation. These data suggest that disruption of the p53-MDM2 interaction by nutlin-3a offers a novel therapeutic approach for DLBCL associated with t(14;18)(q32;q21).

The therapeutic potential of p53 reactivation by nutlin-3a in ALK+ anaplastic large cell lymphoma with wild-type or mutated p53.

p53 is expressed frequently, but is rarely mutated in anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL) tumours. Nutlin-3a is a recently developed small molecule that targets Mdm2, a critical negative regulator of p53, and disrupts the p53-Mdm2 interaction resulting in p53 stabilization and activation. We show that nutlin-3a activates p53 in ALK+ ALCL cells carrying a wild type (wt) or mutated but partially functional p53 gene resulting in p53-dependent cell-cycle arrest and apoptosis. Cell-cycle arrest was associated with upregulation of the cyclin-dependent kinase inhibitor p21. Nutlin-3a-induced apoptotic cell death was accompanied by Bax and Puma upregulation, downregulation of Bcl-xl, survivin, and caspase-3 cleavage, and this was reduced when p53-dependent transactivation activity was inhibited by pifithrin-alpha, or when pifithrin-mu was used to inhibit direct p53 targeting of mitochondria. Nutlin-3a sensitized the activation of the extrinsic apoptotic pathway in wt-p53 ALK+ ALCL cells, in part, through upregulation of DR-5 and downregulation of c-Flip(S/L), and was synergistic with TRAIL in cell death induction. In addition, nutlin-3a treatment enhanced doxorubicin cytotoxicity against ALK+ ALCL cells harbouring mt p53, and this was associated with p73 upregulation. These data suggest that disruption of the p53-mdm2 interaction by nutlin-3a offers a novel therapeutic approach for ALK+ ALCL patients.

TCL1 shows a regulated expression pattern in chronic lymphocytic leukemia that correlates with molecular subtypes and proliferative state.

Expression of the human oncogene TCL1 in transgenic mice produces B-cell tumors that resemble chronic lymphocytic leukemia (CLL) suggesting its role in B-cell tumorigenesis. To clarify the expression pattern and regulation of TCL1 in CLL, we assessed 213 primary tumors by immunohistochemistry (IHC), flow-cytometry and/or Western blot, using a new monoclonal antibody. TCL1 protein was detectable in the majority of CLL (90% by IHC) but showed marked variations across cases with virtual absence in approximately 10% of tumors. Higher TCL1 levels correlated with markers of the 'pre-germinal center' CLL subtype including unmutated VH status (P=0.005), ZAP70 expression (P=0.007), and presence of chromosome 11q22-23 deletions (P=0.04). Intratumoral heterogeneity in TCL1 levels was also prominent and explained in part by markedly lower TCL1 expression in proliferating tumor cells. In vitro exposure of CLL cells to interleukin-4 (but not other growth factors) produced progressive and irreversible decrease in TCL1 protein levels in association with the onset of proliferation. TCL1 expression patterns in CLL are complex and highly dynamic and appear to reflect both the histogenetic subtypes of the disease and the growth parameters of individual tumors. The observed regulation pattern suggests that TCL1 may exert its effects predominantly in the unmutated/ZAP70-positive tumor subset.

Fractionated cyclophosphamide, vincristine, liposomal daunorubicin (daunoXome), and dexamethasone (hyperCVXD) regimen in Richter's syndrome.

Approximately 3 to 5% of patients with chronic lymphocytic leukemia (CLL) develop an aggressive large cell non Hodgkin's lymphoma (NHL) known as Richter's syndrome (RS). RS has a poor prognosis and a response rate of < 10% with fludarabine-based or other cytotoxic combination regimens. The aim of this study was to evaluate the efficacy and toxicity of the hyperCVXD regimen in RS. Twenty-nine patients, median age 61 years (36-75) 23 males, were treated. Prior diagnosis was CLL in 26 patients, NHL in 2, and Prolymphocytic leukemia in 1. Treatment consisted of fractionated cyclophosphamide, vincristine, daunoXome and dexamethasone. Six patients (20%) died while receiving study therapy, 4 (14%) during the first cycle of whom 2 had started therapy with overt pneumonia. Grade 4 granulocytopenia occurred in all 95 cycles of therapy with a median time to recovery of 14 days. Twenty three (24%) cycles were complicated by fever, and 15 (15%) by pneumonia. Sepsis was documented in 8 (8%) cycles, and neuropathy in 5 (5%) of cycles. Twenty three patients had a platelet count < 100 x 10(9)/l prior to therapy: a greater than 50% decrease in platelet count over pre-therapy level occurred in 79% of first cycles, overt bleeding occurred in 4 (4%) of all cycles. Eleven of 29 (38%) patients achieved complete remission (CR), 4 of whom have relapsed after 5, 6, 9, and 12 months of remission. Two of 11 CR patients presented with RS without any prior CLL therapy. One patient had a partial remission. Thus the overall response rate was 12/29 (41%). Overall median survival was 10 months, 19 months in patients who achieved CR, 3 months in those who did not (p = 0.0008). A landmark analysis performed at 2 months from start of therapy comparing patients alive in CR versus patients alive but not in CR showed a median survival of 19 months versus 6 months, respectively (p 0.0017). In conclusion the hyper CVXD regimen has a relatively high response rate, significant toxicity and a moderate impact on survival in RS.

Leukemic mantle cell lymphoma: clinical and pathologic spectrum of twenty-three cases.

Twenty-three patients with marked leukemic involvement by mantle cell lymphoma (MCL) are described. Each patient had an absolute lymphocyte count more than 10 x 10(9)/L. The diagnosis of MCL was supported by compatible immunophenotypic findings and the t(11;14)(q13;q32) in all cases. Morphologically, these cases exhibited a spectrum of findings that we divided into two groups using a cutoff of 20% large or blastoid cells (log rank test, P =.004). Patients with small-cell (<20%) morphologic features survived longer than patients with large/blastoid (> or =20%) morphologic features, (P =.003, log rank test). The most common additional karyotypic abnormality identified in this study involved chromosome 17, in 13 of 23 (56.5%) cases, which correlated with p53 overexpression but not with cytologic features. We conclude that cytologic features of MCL predict the prognosis of patients with marked leukemic involvement. Chromosome 17 abnormalities are common in leukemic MCL, may be involved in pathogenesis, and are associated with p53 expression.

Rapid in vitro conversion of fosphenytoin into phenytoin in sera of patients with liver disease: role of alkaline phosphatase.

Fosphenytoin, a phosphate ester pro drug of phenytoin, also cross-reacts with the fluorescence polarization immunoassay (FPIA) for phenytoin. We measured fosphenytoin concentrations using the FPIA kit and TDx analyzer. We prepared serum pools from normal volunteers and patients with liver disease. None of them received either fosphenytoin or phenytoin. Fosphenytoin standard solution (1 mg/ml) was prepared in water. We supplemented aliquots of normal and liver pools with known amounts of fosphenytoin and measured the concentrations at different time intervals. The conversion of fosphenytoin to phenytoin was slow in sera with normal alkaline phosphatase activities. The conversion was rapid in sera collected from patients with liver disease who also had high alkaline phosphatase activities. The observed concentrations were close to target concentrations within 0-2 min of supplementation with fosphenytoin. Surprisingly, the observed concentration then started to decline slightly but significantly with longer incubation time. In contrast, the observed concentration increased steadily in serum with normal alkaline phosphatase activity. For example, in the normal pool supplemented with 15.0 microg/ml fosphenytoin (as the phenytoin equivalent), the observed concentrations were 6.9, 7.3, 7.7, 8.3, and 9.8 microg/ml at 0-2, 10, 20, 30, and 60 min, respectively. However, in a serum pool prepared from patients with liver disease and supplemented with 15.0 microg/ml of fosphenytoin (alkaline phosphatase: 2547 U/l), the observed phenytoin concentrations were 12.9, 12.1, 11.0, 10.7, and 10.7 microg/ml at 0-2, 10, 20, 30, and 60 min, respectively. When we added alkaline phosphatase to the normal serum pool, we observed rapid conversion of fosphenytoin into phenytoin within 10 min, but the concentrations then declined with longer incubation time. However, when we repeated the experiment with protein-free ultrafiltrate, we observed rapid conversion of fosphenytoin to phenytoin, but the concentration did not decline with longer incubation time.

Mature B-cell leukemias with more than 55% prolymphocytes. A heterogeneous group that includes an unusual variant of mantle cell lymphoma.

We studied 20 cases of mature B-cell leukemia with more than 55% prolymphocytes in peripheral blood or bone marrow, fulfilling the French-American-British criteria for B-cell prolymphocytic leukemia (PLL). Cases segregated into 3 groups: de novo PLL, 6; PLL occurring in patients with a previous well-established diagnosis of chronic lymphocytic leukemia (PLL-HxCLL), 10; and t(11;14)(q13;q32)-positive neoplasms, 4. All cases expressed monotypic immunoglobulin light chain, and most were positive for CD5. All t(11;14)-positive neoplasms were CD23- and uniquely positive for cyclin D1. Cytogenetic abnormalities were present in 19; in all 19, the karyotype was complex, indicating clonal evolution and genomic instability. The most frequent cytogenetic abnormality in de novo PLL involved chromosome 7 in 4 cases. Trisomy 12 or add(12p) was present in 4 cases of PLL-HxCLL. We conclude that mature B-cell leukemias with more than 55% prolymphocytes are a heterogeneous group that includes t(11;14)-positive neoplasms, which we suggest are best classified as mantle cell lymphoma. We also suggest that prolymphocytic morphologic features are a common end-stage of transformation for several B-cell neoplasms.

Pleural posttransplantation lymphoproliferative disorder following liver transplantation.

A case of posttransplantation lymphoproliferative disorder (PTLD) involving the pleura is reported. The patient was a 57-year-old man who underwent liver transplantation 2 years prior to the development of PTLD. The PTLD was pleural-based and was first detected by radiologic studies as a pleural effusion. Transbronchial biopsy and cytologic examination of 2 pleural fluid specimens were nondiagnostic. Subsequent open-wedge biopsy revealed a monomorphic PTLD, composed of large immunoblasts with plasmacytoid differentiation. Immunohistochemical studies demonstrated B-cell lineage with expression of monotypic cytoplasmic immunoglobulin kappa light chain and CD79a, and absence of T-cell antigens. Immunohistochemical and in situ hybridization studies demonstrated Epstein-Barr virus protein and RNA, respectively. No evidence of human herpesvirus 8 DNA was detected by polymerase chain reaction. We report this case because pleural-based PTLD is rare. The diagnosis of this entity is made more difficult by the fact that PTLD is often underrepresented in pleural fluid cytology samples.

Cytogenetic findings in mantle cell lymphoma cases with a high level of peripheral blood involvement have a distinct pattern of abnormalities.

We compared conventional cytogenetic findings in mantle cell lymphomas (MCLs) having an absolute peripheral lymphocytosis of more than 10,000/microL (>10 x 10(9)/L) at diagnosis ("leukemic"; n = 30) with those in cases having no or minimal lymphocytosis ("nodal"; n = 19). Only cases positive for t(11;14) were included for study. Forty-six cases (94%) had abnormalities in addition to t(11;14). The most frequent abnormalities involved chromosome 13 (26 cases [53%]), followed by chromosomes 1, 3, 7, 8, 9, 10, 12, 15, 17, and 21 (11-18 cases [22%-37%]). There was no difference in the number of aberrations between the 2 groups. Abnormalities of chromosomes 17, 21, and 22 were more frequent, and breakpoints involving 8q24, 9p22-24, and 16q24 were found exclusively in leukemic MCL. Chromosome 17 aberrations involved were structural (breakpoints involving 17p13, 17p11.2, 17q) in leukemic MCL but were only numeric in nodal MCL. Thus, leukemic MCL differs from nodal MCL in their cytogenetic profiles, which may contribute to the clinical presentation.