1.7 year follow-up after bortezomib therapy for refractory antibody mediated rejection.

In summary, 1.7 years after transplantation, bortezomib rescue has been durably effective in salvaging our patient with refractory antibody mediated rejection. The only price has been persistently high levels of BK viruria. The presence of ongoing and even recurrent donor specific antibody has made it difficult to reduce immunosuppression further, and the concern that the high levels of BK viruria will eventually progress to viremia and nephropathy necessitates continued therapy with very low dose cidofovir and leflunomide. The absence of C1q binding DSA with stable renal function may provide some reserved optimism that the DSA that is detectable by convention Luminex assay may have reduced pathological implications. However, more data and prolonged follow-up are needed to determine whether or not non-complement binding DSA has an adverse pathological role.

High-dose sequential chemotherapy followed by autologous stem cell transplantation in relapsed and refractory aggressive non-Hodgkin's lymphoma: results of a multicenter phase II study.

BACKGROUND: Combination chemotherapy can cure patients with non-Hodgkin's lymphoma (NHL), but those who suffer treatment failure or relapse still have a poor prognosis. High-dose chemotherapy (HDCT) with autologous stem cell transplantation (ASCT) can improve the outcome of these patients. We evaluated an intensified high-dose sequential chemotherapy program with a final myeloablative course. PATIENTS AND METHODS: Inclusion criteria were age 18-65 years, histologically proven primary progressive or relapsed aggressive NHL and eligibility for HDCT. The therapy consists of two cycles DHAP: dexamethasone 40 mg (day 1-4), high-dose cytarabine 2 g/m2 12q (day 2), cisplatin 100 mg/m2 (day 51); patients with partial (PR) or complete remission (CR) received cyclophosphamide 4 g/m2 (day 37), followed by peripheral blood stem cell (PBSC) harvest; methotrexate 8 g/m2 (day 1) plus vincristine 1.4 mg/m2 (day 51); and etoposide 500 mg/m2 (day 58-62). The final myeloblative course was BEAM: cytarabine 200 mg/m2 12q (day 81-84), etoposide 150 mg/m2 12q (day 81-84), melphalan 140 mg/m2 (day 80), carmustin 300 mg/m2 (day 80) followed by PBSCT. RESULTS: Fifty-seven patients (median age 43 years, range 24-65) were enrolled: 23 (40%) patients were refractory to primary therapy and 34 (60%) patients had relapsed NHL. The response rate (RR) after 2 cycles of DHAP was 72% (9% CR, 63% PR) and at the final evaluation (100 days post transplantation) 43% (32% CR, 11% PR). Toxicity was tolerable. Median follow-up was 25 months (range 1-76 months). Freedom from second failure (FF2F) and overall survival (OS) at 2 years were 25% and 47% for all patients, respectively. FF2F at 2 years for patients with relapse and for patients refractory to primary therapy were 35% and 9% (P=0.0006), respectively. OS at 2 years for patients with relapse and for patients refractory to primary therapy were 58% and 24% (P=0.0044), respectively. CONCLUSIONS: We conclude that this regimen is feasible, tolerable and effective in patients with relapsed NHL. In contrast, the results in patients with progressive disease are unsatisfactory. This program is currently being modified by addition of rituximab for patients with relapsed aggressive NHL.

Cologne high-dose sequential chemotherapy in relapsed and refractory Hodgkin lymphoma: results of a large multicenter study of the German Hodgkin Lymphoma Study Group (GHSG).

BACKGROUND: We designed a dose- and time-intensified high-dose sequential chemotherapy regimen for patients with relapsed and refractory Hodgkin lymphoma (HD). PATIENTS AND METHODS: Eligibility criteria included age 18-65 years, histologically proven primary progressive (PD) or relapsed HD. Treatment consisted of two cycles DHAP (dexamethasone, high-dose cytarabine, cisplatinum); patients with chemosensitive disease received cyclophosphamide followed by peripheral blood stem cell harvest; methotrexate plus vincristine, etoposide and BEAM plus peripheral blood stem cell transplantation (PBSCT). RESULTS: A total of 102 patients (median age 34 years, range 18-64) were enrolled. The response rate was 80% (72% complete response, 8% partial response). With a median follow-up of 30 months (range 3-61 months), freedom from second failure (FF2F) and overall survival (OS) were 59% and 78% for all patients, respectively. FF2F and OS for patients with early relapse were 62% and 81%, for late relapse 65% and 81%; for PD 41% and 48%, and for multiple relapse 39% and 48%, respectively. In multivariate analysis response after DHAP (P <0.0001) and duration of first remission (PD and multiple relapse versus early and late relapse; P=0.0127) were prognostic factors for FF2F. Response after DHAP (P <0.0081), duration of first remission (P=0.0017) and anemia (P=0.019) were significant for OS. CONCLUSION: Based on the promising results of this study, a prospective randomized European intergroup study was started comparing this intensified regimen with two courses of DHAP followed by BEAM (HD-R2 protocol).

Nonmyeloablative stem cell transplantation in metastatic renal cell carcinoma: delayed graft-versus-tumor effect is associated with chimerism conversion but transplantation has high toxicity.

Seven out of 29 patients with metastatic renal cell carcinoma (RCC) considered eligible for allogeneic stem cell transplantation underwent nonmyeloablative stem cell transplantation (NST) from HLA-identical donors. Conditioning comprised cyclophosphamide, fludarabine and antithymocyte globulin. Prolonged mixed chimerism (MC) after engraftment converted to complete donor chimerism (CC) after infusion of donor lymphocytes and/or graft-versus-host disease (GvHD) in six patients. Five patients developed severe GvHD. Two of seven patients had a delayed tumor response after conversion to CC. After a median follow-up of 10 months (4-24 months), 5/7 patients are alive, one in very good partial remission (PR), one with stable and three with progressive disease. One of the seven patients died from sepsis in PR and 1/7 died from rapid tumor progression after sustained MC. None of the 22 nontransplanted patients responded to further therapies. Survival after 1 year was 59% in transplanted and 66% in nontransplanted patients (n.s.). A pooled data analysis from the literature suggests a graft-versus-tumor effect after transplant in patients with metastatic RCC, which becomes effective after chimerism conversion. Available data demonstrate high nonrelapse mortality in these patients. NST in RCC still has to be regarded as an investigational approach requiring careful patients' selection and longer follow-up within clinical studies.

Coinfection with Cryptosporidium, Isospora and S. stercoralis in a patient with AIDS--a case report.

A thirty eight year old lady, positive for human immunodeficiency virus (HIV) antibodies, was found to be positive for three different opportunistic parasitic infections. Cryptosporidium, Isospora and S.stercoralis were simultaneously detected from her stool samples. Her CD4 count was 116/cmm. The patient belonged to a slum area with poor sanitation.

Time-intensified dexamethasone/cisplatin/cytarabine: an effective salvage therapy with low toxicity in patients with relapsed and refractory Hodgkin's disease.

BACKGROUND: An important variable affecting outcome in relapsed and refractory Hodgkin's disease (HD) is the potential of conventional salvage chemotherapy to reduce tumor volume before high-dose chemotherapy (HDCT) and autologous stem cell transplantation. Currently, the optimal salvage chemotherapy regimen for these patients is unclear. Since dexamethasone/cisplatin/cytarabine (DHAP) given at 3-4 week intervals has been shown to be very effective in patients with relapsed aggressive non-Hodgkin's lymphoma, we evaluated this regimen given at a median of 16-day intervals in patients with relapsed and refractory HD. PATIENTS AND METHODS: Patients with relapsed or refractory HD were treated with two cycles of DHAP [dexamethasone 40 mg intravenously (i.v.) day 1-4, cisplatin 100 mg/m(2) i.v. as 24-h continuous infusion day 1, and cytarabine 2 g/m(2) i.v. 12q day 2]. Granulocyte colony-stimulating factor (G-CSF) was given at a dose of 5 micro g/kg from day 4 until day 13. Patients with partial remission (PR) or complete remission (CR) after two cycles of DHAP received sequential HDCT. RESULTS: The median age of the 102 patients included was 34 years (range 21-64 years). Forty-two percent of the patients had late relapse, 29% early relapse, 12% multiple relapse and 16% primary progressive/refractory disease. The response rate (RR) after two cycles of DHAP was 89% (21% CR, 68% PR). The RRs for patients with late, early, multiple and progressive HD were 91%, 93%, 92% and 65%, respectively. Using the chi-square test for independence, remission status (relapsed HD versus progressive HD) and stage at relapse (stage I/II versus stage III/IV) were significant factors for response to DHAP. WHO grade 4 leukocytopenia and thrombocytopenia were the main toxic- ities occurring in 43% (mean duration 1.1 days, range 0-6) and 48% (mean duration 1.4 days, range 0-11) of all courses, respectively. Neither severe infections nor treatment-related deaths occurred. Peripheral blood stem cells (PBSCs) were collected after the first cycle DHAP in eight patients. The hematopoietic progenitors showed a very rapid increase from day 10 with a synchronous and impressive peak on day 12. A mean of 6.1 x 10(6)/kg CD34(+) cells were collected per apheresis. As originally recommended in the protocol, PBSCs were routinely collected during sequential HDCT in the remaining patients. CONCLUSIONS: A brief tumor-reducing program with two cycles of DHAP given in short intervals supported by G-CSF is effective and well-tolerated in patients with relapsed and refractory HD. This regimen can be used to mobilize stem cells and select those patients with chemosensitive relapse who should subsequently be treated with HDCT.

Infectious complications after high-dose chemotherapy and autologous stem cell transplantation: comparison between patients with lymphoma or multiple myeloma and patients with solid tumors.

From November 1994 to May 1998, 117 patients (66 with solid tumor, 36 with lymphoma, 14 with multiple myeloma, one with acute leukemia) underwent 178 cycles of high-dose chemotherapy and autologous stem cell transplantation (ASCT) at our institution. We retrospectively analyzed the infectious complications that occurred after ASCT. Median duration of neutropenia (granulocyte count <0.5 x 10(9)/l ) was 8 days, the overall incidence of fever requiring antimicrobial treatment was 63%. 35.4% of patients had fever of unknown orign (FUO), whereas primary bacteremia occurred in 21.3%, pneumonia in 3.4% and severe skin infection in 1.1% of patients. Invasive fungal infections occurred in three, and enterocolitis in one patient. Infection was fatal in three patients (2.6%), in each case due to septic shock. The most frequently isolated pathogens were Gram-positive cocci. Median time to defervescence with antimicrobial therapy was 4 days (6 days in patients with bacteremia or other severe infection, and 3 days in patients with FUO). First-line antimicrobial therapy was successful in 65% of patients with FUO and 30.6% of patients with documented infections. With respect to the incidence, type and clinical course of infection, no significant differences between patients with lymphoma or multiple myeloma and those with solid tumors were detected.

Induction of stable long-term mixed hematopoietic chimerism following nonmyeloablative conditioning with T cell-depleting antibodies, cyclophosphamide, and thymic irradiation leads to donor-specific in vitro and in vivo tolerance.

BACKGROUND: Successful transplantation of solid organs relies on long-term immunosuppression for the prevention of graft rejection. Donor-specific tolerance without the need for continuous immunosuppression can be observed after allogeneic BMT. However, its routine use for tolerance induction has been precluded so far by the high conditioning-related toxicity of standard BMT regimens. Our laboratory has recently established a cyclophosphamide (CTX) plus thymic irradiation (TI)-based nonmyeloablative conditioning protocol for the treatment of hematologic malignancies. We have recently described the successful clinical application of this approach for the induction of donor-specific tolerance in a patient receiving a living-related kidney transplant, which resulted in graft acceptance without long-term immunosuppression. The aim of this study was to evaluate the induction and maintenance of host-versus-graft tolerance following this CTX-plus-TI-based regimen in a mouse model. METHODS: Induction of mixed hematopoietic chimerism and development of donor-specific tolerance following the CTX-based nonmyeloablative conditioning regimen (200 mg/kg CTX, in vivo T-cell depletion [anti-CD4 monoclonal antibody (MoAb) GK1.5 and anti-CD8 MoAb 2.43], and 7 Gy TI) was studied in the fully major histocompatibility complex (MHC)-mismatched B10.A (H2a)-->B6 (H2b) strain combination. RESULTS: The conditioning regimen allowed allogeneic bone marrow engraftment and persistent (>30 weeks) mixed lymphohematopoietic chimerism in almost all recipients. TI was essential to allow engraftment and development of tolerance, which was evident in all lasting chimeras. Compared to animals receiving a similar TBI-based conditioning regimen, overall levels of chimerism were significantly lower in the CTX-plus-TI-conditioned animals. However, donor-specific tolerance in vitro and in vivo was evident in CTX-plus-TI-conditioned chimeras. Tolerance was associated with the presence of donor-type MHC class II+ cells in the thymus and deletion of donor-reactive cells, as determined by Mtv-8 and Mtv-9 superantigen-mediated deletion of Vbeta11+ and Vbeta5/1.2+ T cells. CONCLUSION: Engraftment, long-term chimerism, and induction of donor-specific tolerance can be achieved using a nonmyeloablative CTX-based conditioning regimen in fully MHC-mismatched BMT recipients without the induction of GVHD.

Anti-CD20- and B-cell receptor-mediated apoptosis: evidence for shared intracellular signaling pathways.

Clinical administration of the anti-CD20 antibody IDEC-C2B8 can induce remission of low-grade B-cell lymphoma. Whereas it has been suggested that the main mechanisms of action are complement-mediated and antibody-dependent cell-mediated cytotoxicity, we demonstrate that monoclonal antibody IDEC-C2B8 is a strong inducer of apoptosis in CD20-positive B-cell lymphoma cell lines reflecting different stages of lymphomagenesis. Thus, CD20-dependent apoptosis was inducible in human surface IgM-positive Burkitt's lymphoma cell lines as well as in more mature surface IgM-negative B-cell lymphoma cell lines carrying the t(14;18) translocation. Furthermore, in Burkitt's lymphoma cell lines, we observed a striking correlation between anti-CD20- and B-cell receptor-mediated apoptosis with regard to sensitivity toward the apoptotic stimuli and the execution of the apoptotic pathway. Thus, induction of anti-CD20- or B-cell receptor-mediated apoptosis involved rapid up-regulation of the proapoptotic protein Bax. In addition, we show similar changes in the mRNA expression level of two early response genes, c-myc and Berg36, as well as activation of the mitogen-activated protein kinase family members p44 (extracellular signal-regulated kinase 1) and p42 (extracellular signal-regulated kinase 2) and activation of activator protein 1 (AP-1) DNA binding activity. These data support our hypothesis that both pathways are mediated in part by the same signal-transducing molecules. These results might help explain the resistance and regression of lymphomas to IDEC-C2B8 and give new insights in the signaling cascade after CD20 ligation.

Successful peripheral blood stem cell mobilization with etoposide (VP-16) in patients with relapsed or resistant lymphoma who failed cyclophosphamide mobilization.

High-dose chemotherapy (HDCT) followed by autologous blood stem cell transplantation is considered the treatment of choice for patients with relapsed or resistant aggressive non-Hodgkin's lymphoma (NHL) or Hodgkin's disease (HD). However, several authors report failure of standard mobilization regimens in 29% to 56% of these patients making the completion of HDCT impossible and as a result, negatively influencing long-term outcome. Thus, effective new regimens for patients failing initial mobilization are needed. Here we report the results of using etoposide as a mobilizing agent in 16 patients with primary resistant or relapsed malignant lymphoma who had failed prior mobilization of peripheral blood stem cells (PBSC) with cyclophosphamide (4 g/m2) followed by G-CSF. The use of etoposide 500 mg/m2 (days 1-4) + G-CSF resulted in the successful collection of adequate numbers of PBSC with a median harvest of 3.6 x 10(6)/kg (range 2.2-12.6) CD34+ cells in all 16 patients. In 7/16 (44%) patients, the target yield of at least 2.0 x 10(6) CD34+ cells was harvested by a single apheresis and the maximum number of separations for all patients was two. No excessive toxicities appeared, allowing all patients to proceed to myeloablative chemotherapy. In addition, median peak values of circulating CD34+ cells were significantly higher after etoposide as compared to cyclophosphamide (49.2/microl vs 4.7/microl; P = 0.0004). These results indicate that etoposide + G-CSF is a highly effective mobilization regimen in patients who have failed cyclophosphamide mobilization.

Combined positive/negative purging and transplantation of peripheral blood progenitor cell autografts in breast cancer patients: a pilot study.

This trial studied the feasibility and efficiency of a novel procedure of double purging to eliminate tumor cells from leukapheresis products of stage IV breast cancer patients. After induction and mobilization therapy, 35 leukapheresis products from 16 breast cancer patients were subjected to CD34+ enrichment (i.e., positive selection) with the Isolex 300 device and subsequent immunomagnetic depletion of tumor cells (i.e., negative selection) using a cocktail of three monoclonal antibodies directed against epithelial antigens. Patients with clinical response to induction chemotherapy proceeded to tandem high-dose chemotherapy, which consisted of melphalan (140 mg/m2) followed by retransfusion of the purged graft. After hematologic recovery, patients received ifosfamide 14 g/m2, carboplatin 1.5 g/m2, and etoposide 1.5g/m2 (ICE), again followed by autografting. After positive selection, a median purity of 96.6% CD34+ cells (range 48.4-99.2%) and a recovery of 56.8% (range 25.8-92.6%) were achieved. Subsequent negative purging resulted in a median CD34+ purity of 97.2%. Overall CD34+ recovery after both purging procedures was 51.1% (range 18.5-82.4%). Tumor cells were detectable in 8 of 16 (50%) starting fractions before purging. After both purging cycles, only 1 of 16 autografts remained positive for tumor cells compared to 3 of 16 after CD34+ selection. A calculated purging efficiency of 2 to >4 log was achieved. Engraftment was rapid, reaching > or =500/microL neutrophils on day +10 after melphalan and on day +9 after ICE. A platelet count of > or =20.000/microL was reached on day +12 after melphalan and on day +11 after ICE. Thus, combining positive and negative purging is feasible, further enhances purging efficiency, and does not compromise the quality of the graft, leading to rapid engraftment after high-dose chemotherapy.

Detection of tumor cells in peripheral blood samples from patients with germ cell tumors using immunocytochemical and reverse transcriptase-polymerase chain reaction techniques.

The aim of this study was to establish sensitive techniques for the detection of residual germ cell tumor cells in peripheral blood and progenitor cell harvests. For this purpose, we used immunocytochemical staining for cytokeratin filaments and reverse transcriptase-polymerase chain reaction (RT-PCR) for epidermal growth factor receptor (EGF-R) and germ cell alkaline phosphatase (GCAP). Germ cell tumor lines Tera-1 and Tera-2 were titrated into normal peripheral blood. Immunocytochemical staining allowed detection of one cytokeratin-positive tumor cell in 10(5) cells. RT-PCR for EGF-R revealed one tumor cell in 10 cells for Tera-1 and one tumor cell in 10(3) cells for Tera-2, while RT-PCR for GCAP displayed a sensitivity of one tumor cell in 10(6) cells for Tera-1, one tumor cell in 10(4) cells for Tera-2, and no positivity in normal mononuclear cells (n = 20) and progenitor cell harvests (n = 5). The analysis of peripheral blood and progenitor cell harvests from 20 patients with germ cell tumors revealed tumor cell contamination in three patients using immunocytochemical staining and in seven patients by RT-PCR for GCAP. We conclude that RT-PCR for GCAP appears to be suitable for the sensitive detection of residual germ cell tumor cells in peripheral blood and progenitor cell harvests.

Growth and differentiation of human stem cell factor/erythropoietin-dependent erythroid progenitor cells in vitro.

Stem cell factor (SCF) and erythropoietin (Epo) effectively support erythroid cell development in vivo and in vitro. We have studied here an SCF/Epo-dependent erythroid progenitor cell from cord blood that can be efficiently amplified in liquid culture to large cell numbers in the presence of SCF, Epo, insulin-like growth factor-1 (IGF-1), dexamethasone, and estrogen. Additionally, by changing the culture conditions and by administration of Epo plus insulin, such progenitor cells effectively undergo terminal differentiation in culture and thereby faithfully recapitulate erythroid cell differentiation in vitro. This SCF/Epo-dependent erythroid progenitor is also present in CD34(+) peripheral blood stem cells and human bone marrow and can be isolated, amplified, and differentiated in vitro under the same conditions. Thus, highly homogenous populations of SCF/Epo-dependent erythroid progenitors can be obtained in large cell numbers that are most suitable for further biochemical and molecular studies. We demonstrate that such cells express the recently identified adapter protein p62(dok) that is involved in signaling downstream of the c-kit/SCF receptor. Additionally, cells express the cyclin-dependent kinase (CDK) inhibitors p21(cip1) and p27(kip1) that are highly induced when cells differentiate. Thus, the in vitro system described allows the study of molecules and signaling pathways involved in proliferation or differentiation of human erythroid cells.

Ex vivo breast cancer cell purging by adenovirus-mediated cytosine deaminase gene transfer and short-term incubation with 5-fluorocytosine completely prevents tumor growth after transplantation.

Peripheral blood progenitor harvests of breast cancer patients are contaminated with tumor cells, suggesting a potential role for these cells in the relapse after high-dose chemotherapy. Whereas physical purging methods do not eliminate contaminating tumor cells completely, pharmacological purging, although highly efficient, is hampered by a strong nonspecific toxicity toward hematopoietic progenitor cells. Taking advantage of the high efficiency of adenovirus-mediated gene transfer to epithelial cells, we selectively loaded breast cancer cells in vitro with a cytotoxic drug by gene transfer of the prodrug-converting enzyme cytosine deaminase (AdCMV.CD) and 5-fluorocytosine (5-FC). Despite the low dose of vector administered, limited exposure to 5-FC, and transplantation only of viable tumor cells into SCID mice, all animals that received cells treated in vitro with AdCMV.CD plus 5-FC were completely free of tumor development. These data show that the selective loading of tumor cells with AdCMV.CD/5-FC might be useful for purging of autografts.

Inhibition of CPP32 blocks surface IgM-mediated apoptosis and D4-GDI cleavage in human BL60 Burkitt lymphoma cells.

Apoptosis (programmed cell death) is instrumental in the process of controlling lymphocyte growth and selection. Negative selection, mediated by surface IgM (sIgM) signaling after encountering self antigen, eliminates autoreactive B cells. To identify proteins which are potentially involved in anti-IgM-mediated apoptosis, we used an anti-IgM-sensitive subclone of the human Burkitt lymphoma cell line BL60. After anti-IgM treatment and separation of apoptosis-committed cells, we performed high resolution two-dimensional gel electrophoresis (2-DE). Comparison of the 2-DE protein patterns from apoptotic and non-apoptotic cells showed differences in approximately 80 spots. Subsequent analysis of these proteins was performed by mass spectrometry and Edman microsequencing. We report that one of these spots which disappears after sIgM cross-linking turned out to be D4-GDI. D4-GDI is an abundant hematopoietic cell GDP dissociation inhibitor for the Ras-related Rho family GTPase. D4-GDI was rapidly truncated to a 23-kDa fragment in BL60 cells. By using a Rho-GDI-specific antiserum, which cross-reacts with D4-GDI, we observed the onset of cleavage after 8 h of stimulation with anti-IgM. Cleavage and apoptosis could be completely inhibited by z-DEVD-fmk, a selective irreversible inhibitor of CPP32 (caspase-3), whereas ac-YVAD-cmk, an inhibitor for interleukin-1beta-converting enzyme-like proteases, did not block cleavage of D4-GDI or apoptosis. Our results revealed the functional importance of caspases and a new target protein in the process of anti-IgM-mediated apoptosis.

Overexpression of the death-promoting gene bax-alpha sensitizes human BL-41 Burkitt lymphoma cells for surface IgM-mediated apoptosis.

Major regulators of programmed cell death, or apoptosis, are the members of the bcl-2 gene family. Recently, we reported that surface(s) IgM triggering of the human B lymphoma cell line BL-41 led to strong induction of bax-alpha, a death-promoting member of the bcl-2 family, and subsequently to induction of apoptosis, suggesting a potential regulatory role of bax-alpha in sIgM-mediated cell death. In contrast, apoptosis-resistant subclones of this cell line showed only weak bax-alpha expression, which was not inducible by sIgM cross-linking. In this study, we were able to demonstrate the functional significance of this observation. We stably transfected bax-alpha into a BL-41 subline resistant against sIgM-mediated apoptosis. Several bax-alpha overexpressing clones could be selected, which all showed enhanced sensitivity for sIgM-mediated apoptosis. In contrast, no sensitive clone could be identified in a large number of mock controls. This clearly indicates that induction of bax-alpha is a critical regulatory step, which sensitizes B cells for sIgM-mediated apoptosis.

Nuclear localization and increased levels of transcription factor YB-1 in primary human breast cancers are associated with intrinsic MDR1 gene expression.

Breast cancers are either primarily resistant to chemotherapy (intrinsic resistance), or respond to chemotherapy but later recur with a multidrug-resistant phenotype because of overexpression of the multidrug transporter P-glycoprotein. The MDR1 gene encoding P-glycoprotein may be transcriptionally regulated by a Y-box transcription factor. We now report that, in multidrug-resistant MCF-7 breast cancer cells, nuclear localization of YB-1 is associated with MDR-1 gene expression. In drug-sensitive MCF-7 cells, however, YB-1 was localized to the cytoplasm. Regulated overexpression of YB-1 in drug-sensitive diploid breast epithelial cells induced MDR-1 gene expression and multidrug resistance. In 27 out of 27 untreated primary breast cancers, YB-1 protein was expressed in the cytoplasm although it was undetectable in normal breast tissue of these patients. In a subgroup of tumors (9/27), however, YB-1 was also localized to the nucleus and, in these cases, high levels of P-glycoprotein were present. These results show that in a subset of untreated primary breast cancers, nuclear localization of YB-1 protein is associated with intrinsic multidrug resistance. Our data show that YB-1 has an important role in controlling MDR1 gene transcription and this finding provides a basis for the analysis of molecular mechanisms responsible for intrinsic multidrug resistance in human breast cancer.

Activation and activation-induced death of human tonsillar B cells and Burkitt lymphoma cells: lack of CD95 (Fas/APO-1) ligand expression and function.

Activation of T cells was shown to up-regulate the Fas ligand (FasL) which binds to the CD95 (APO-1/Fas) antigen and mediates activation-induced cell death (AICD) of activated T cells and T lymphoma cells. A recent report showed that mouse B cells express the FasL upon activation with lipopolysaccharide (LPS). We therefore asked whether activation of human B cells induces expression of FasL and whether AICD is mediated, as in T cells, through autocrine production of the FasL. We used human tonsillar B cells and Burkitt lymphoma cell lines which were activated by CD40 ligand, surface (s)IgM cross-linking, or LPS. Northern and Western blot analysis failed to detect FasL during B cell activation or AICD of both normal and malignant B cells. Low-level expression of FasL was detected by reverse transcriptase-polymerase chain reaction. Functional experiments, however, showed that FasL is not functionally expressed upon activation. IgM-mediated AICD in the tonsillar or Burkitt lymphoma B cells could not be inhibited by FasL blocking. Thus, our data show that, in contrast to T cells, activation of normal or malignant human B cells does not lead to functional FasL expression.