Review of Bruton tyrosine kinase inhibitors for the treatment of relapsed or refractory mantle cell lymphoma

Mantle cell lymphoma (mcl) is a rare subtype of aggressive B-cell non-Hodgkin lymphoma that remains incurable with standard therapy. Patients typically require multiple lines of therapy, and those with relapsed or refractory (r/r) disease have a very poor prognosis. The Bruton tyrosine kinase (btk) inhibitor ibrutinib has proven to be an effective agent for patients with r/r mcl. Although usually well tolerated, ibrutinib can be associated with unique toxicities, requiring discontinuation in some patients. Effective and well-tolerated alternatives to ibrutinib for patients with r/r mcl are therefore needed. Novel btk inhibitors such as acalabrutinib, zanubrutinib, and tirabrutinib are designed to improve on the safety and efficacy of first-generation btk inhibitors such as ibrutinib. Data from single-arm clinical trials suggest that, compared with ibrutinib, second-generation btk inhibitors have comparable efficacy and might have a more favourable toxicity profile. Those newer btk inhibitors might therefore provide a viable treatment option for patients with r/r mcl.

Abstract P2-09-12: Perilymphatic IRX-2 cytokine therapy to enhance tumor infiltrating lymphocytes (TILs) and PD-L1 expression preceding curative-intent therapy in early stage breast cancer (ESBC)

Background: Cytokines are being explored as a therapeutic strategy to modulate the tumor microenvironment and facilitate immunotherapy benefit in breast cancer. Here, we investigate a locoregional therapeutic approach whereby cytokines (IRX-2) are administered into the subcutaneous peri-areolar tissue (in an anatomic distribution similar to sentinel lymph node mapping) to facilitate immune cell recruitment/activation within the draining lymph nodes and tumor in ESBC. IRX-2 is derived from ex vivo phytohemagglutinin-stimulated lymphocytes and contains multiple cytokines including IL-1β, IL-2, TNF-α, IFN-γ, IL-6, IL-8, and GM-CSF, with stable concentrations from lot to lot. Preclinically, IRX-2 activates T-cells and natural killer (NK) cells, facilitates antigen presentation, and enhances activity of anti-PD-1/L1 in a SCC7 model. In a preceding head/neck squamous cell carcinoma phase I trial, perilymphatic IRX-2 was safe and increased TILs. Here, we report the final clinical results of a phase Ib trial evaluating the feasibility and immunologic activity of IRX-2 in ESBC.

Methods: Beginning 21 days prior to surgical resection, enrolled operable patients with stage I-III ESBC (all subtypes) received the pre-operative IRX-2 regimen consisting of a single low-dose cyclophosphamide (300 mg/m2 to facilitate T-regulatory cell depletion), followed by 10 days of subcutaneous peri-areolar IRX-2 injections into the affected breast (1 mL × 2 at tumor axis and at 90°). Endpoints were feasibility (primary endpoint), stromal TIL (sTIL) count (pre-treatment versus post-treatment, blinded average of two pathologist reads using San Antonio H&E sTIL guidelines), PD-L1 expression (Nanostring) and enumeration of peripheral immune cells by flow cytometry.

Results: All patients (n=16/16) completed and tolerated the regimen with no surgical delays or treatment-attributed grade III/IV toxicities. Common adverse events (occurring in >15% subjects) attributed to IRX-2 injections were: injection site reaction (grade 1, n=8/16), bruising (grade 1, n=7/16), and pain (grade 1, n=3/16). Common adverse events attributed to low-dose cyclophosphamide were: fatigue (grade 1, n=5/16) and nausea (grade 1/2, n=3/16). Treatment was associated with an increase in sTIL score (Wilcoxon signed-rank p=.04), with 4/10 sTIL-low tumors (0-10% score) re-categorized to sTIL-moderate (11-50% score). Increases in PD-L1 RNA expression were observed (Wilcoxon signed-rank p=.04) in 12/16 tumors (median 57% increase, range: -53% to 185% increase), as well as increases in Nanostring NK and Th1 cell signatures. In blood, increases in CD4 and CD8 effector T-cell activation (ICOS, HLA-DR, and CD38) and T-reg depletion were observed.

Conclusions: IRX-2 was well tolerated with preliminary evidence of sTIL increase, PD-L1 upregulation, and peripheral lymphocyte activation. Based upon these data and preclinical evaluations demonstrating synergy with checkpoint inhibition, the IRX-2 regimen is being evaluated for clinical efficacy in conjunction with pembrolizumab and neoadjuvant chemotherapy (doxorubicin, cyclophosphamide, paclitaxel) in patients with stage II-III triple negative breast cancer.

Citation Format: Pucilowska J, Egan JE, Berinstein NL, Moxon N, Aliabadi-Wahle S, Imatani JH, Conlin A, Acheson A, Massimino K, Martel M, Campbell M, Wu Y, Sun Z, Redmond W, Shah M, Urba WJ, Page DB. Perilymphatic IRX-2 cytokine therapy to enhance tumor infiltrating lymphocytes (TILs) and PD-L1 expression preceding curative-intent therapy in early stage breast cancer (ESBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-09-12.

Treatment outcomes for older patients with relapsed/refractory aggressive lymphoma receiving salvage chemotherapy and autologous stem cell transplantation are similar to younger patients: a subgroup analysis from the phase III CCTG LY.12 trial

Background

High-dose therapy and autologous stem cell transplantation (ASCT) is often considered for older patients (age >60 years) with relapsed/refractory aggressive lymphomas. Although registry data support the safety and potential efficacy of this approach, there are no prospective trials evaluating outcomes of ASCT in older patients. We evaluated the result of second-line chemotherapy and ASCT in older versus younger patients in the CCTG randomized LY.12 trial.

Patients and methods

From August 2003 to November 2011, 619 patients with relapsed/refractory aggressive lymphoma were randomized to gemcitabine, dexamethasone, cisplatin (GDP) or dexamethasone, cytarabine, cisplatin (DHAP); 177 patients (28.6%) enrolled were >60.0 years of age (range, 60-74) and 442 were ≤60.0 years of age. After two to three cycles, responding patients proceeded to ASCT. Intention-to-treat analysis was used to compare response rate, transplantation rate, event-free survival (EFS) and overall survival (OS) between patients aged ≤60.0 and >60.0 years.

Results

Patient characteristics were comparable between the two cohorts, except a larger proportion of older patients had high International Prognostic Index risk scores. Response to salvage therapy was 48.6% for patients aged  >60.0 versus 43.0% for those aged  ≤60.0 (P = 0.21). Transplantation rates were also similar: 50.3% versus 49.8% (P = 0.87) for older versus younger patients. Rates of febrile neutropenia and adverse events requiring hospitalization were comparable for older and younger patients (30.5% versus 22.9% and 37.9% versus 32.1%, respectively). With a median follow-up of 53 months, there was no difference in 4-year OS (36% and 40% for patients aged >60.0 and ≤60.0 years, P = 0.42), or 4-year EFS (20% versus 28%, P = 0.43). Mortality from salvage therapy was 8/174 (4.60%) and 5/436 (1.15%), and 100-day mortality post-ASCT was 7/88 (8.06%) and 4/219 (1.85%).

Conclusion

This subgroup analysis suggests that older patients derive similar benefit from salvage therapy and ASCT to younger patients, with acceptable toxicity.

ClinicalTrials.gov Identifier

NCT00078949.

Prognostic value of the trichorhinophalangeal syndrome-1 (TRPS-1), a GATA family transcription factor, in early-stage breast cancer

BACKGROUND

TRPS-1 is a new GATA transcription factor that is differentially expressed in breast cancer (BC) where it been found recently to regulate epithelial-to-mesenchymal transition (EMT).

PATIENTS AND METHODS

We carried out a quantitative immunohistochemistry (qIHC) analysis of TRPS-1 expression in 341 primary-stage I-III BC samples in relation to patient clinical characteristics as well as its prognostic value, especially in an estrogen receptor-positive (ER+) subgroup.

RESULTS

Higher TRPS-1 expression was significantly associated with a number of clinical and pathological characteristics as well as with improved overall survival (OS) and disease-free survival (DFS). Among stage I/II ER+ BC patients who received endocrine therapy alone, those with high TRPS-1 expression had significantly longer OS and DFS. There was also a strong association between TRPS-1 levels and the EMT marker E-cadherin in the ER+ invasive ductal carcinoma cases. Analysis of gene expression data on a panel of BC lines found that TRPS-1 expression was low or absent in BC lines having enriched mesenchymal features.

CONCLUSIONS

Our data indicated that TRPS-1 is an independent prognostic marker in early-stage BC and a new EMT marker that can distinguish patients with ER+ BC who will respond longer to adjuvant endocrine therapy.

Intensive chemotherapy and autologous stem-cell transplantation plus rituximab is superior to conventional chemotherapy for newly diagnosed advanced stage mantle-cell lymphoma: a matched pair analysis

BACKGROUND

The outcome of 20 patients with newly diagnosed mantle-cell lymphoma (MCL) treated on a prospective trial of autologous stem-cell transplantation (ASCT) and rituximab immunotherapy was compared with the outcome of 40 matched historical control patients treated with standard combination chemotherapy.

PATIENTS AND METHODS

Control patients with MCL were identified from a lymphoma database, and pairs were matched with patients receiving ASCT-rituximab for stage of disease, gender and age (+/-5 years). Only patients treated with an anthracycline- or cyclophosphamide-fludarabine-based regimen were included.

RESULTS

Seventeen of 20 patients who received ASCT-rituximab remain alive in remission at a median of 30 months from diagnosis; one patient relapsed 2 years post-ASCT, and two died at 7 and 11 months post-ASCT without evidence of lymphoma. Of 40 patients treated with conventional chemotherapy, with a median follow-up of 80 months, 33 have relapsed or progressed and 29 have died. Overall (OS) and progression-free (PFS) survival were superior in patients treated with ASCT-rituximab compared with those treated with conventional chemotherapy (PFS at 3 years, 89% versus 29%, P <0.00001; OS at 3 years, 88% versus 65%, P = 0.052).

CONCLUSIONS

This matched-pair analysis suggests that patients with advanced-stage MCL treated with ASCT-rituximab had statistically significantly better PFS and a trend toward better OS than patients treated with conventional chemotherapy. Longer follow-up will determine response duration and the true impact of this treatment strategy on PFS and OS.

Spontaneous regression of Hodgkin's disease: two case reports and a review of the literature

We present two cases of patients with Hodgkin's lymphoma who experienced spontaneous regressions of their disease. The first case was a 31-year-old man diagnosed with stage IIIA lymphocyte predominant Hodgkin's disease in 1994, who elected to be followed without any treatment. Over the subsequent 3 years, he experienced significant regression in his lymphadenopathy, and still remains asymptomatic of his disease 70 months after diagnosis. The second case was a 47-year-old man with a bulky anterior mediastinal mass found on a thoracic CT scan, ultimately diagnosed with stage IIB Nodular Sclerosing Hodgkin's Lymphoma. Repeat imaging of the chest performed two months later, just prior to initiating treatment, revealed that the mass had spontaneously decreased by >75% of its original size. Spontaneous regressions of Hodgkin's lymphoma are exceedingly rare. A review of the literature regarding spontaneous regressions of lymphoma and cancer in general is discussed.

Pharmacokinetic study of patients with follicular or mantle cell lymphoma treated with rituximab as 'in vivo purge' and consolidative immunotherapy following autologous stem cell transplantation

BACKGROUND

Little is known about the pharmacokinetics of rituximab in an autologous stem cell transplant (ASCT) setting.

PATIENTS AND METHODS

We evaluated serum rituximab levels in 26 patients with follicular or mantle cell lymphoma treated with a combination of ASCT and immunotherapy. Patients received nine infusions of rituximab (375 mg/m(2)): one dose as an 'in vivo purge' prior to stem cell collection, and two 4-week cycles at 8 and 24 weeks following ASCT. Pre- and post-infusion serum rituximab levels were measured during the purging dose, with doses 1 and 4 of both sets of maintenance rituximab cycles, and 12 weeks and 24 weeks following treatment.

RESULTS

Rituximab levels were detectable after the first infusion, and peaked at a mean concentration of 463.8 micro g/ml after the final dose. Levels remained detectable 24 weeks after completion of treatment. There was a trend toward higher rituximab levels in patients with follicular lymphoma. Serum concentrations achieved during the maintenance cycles were similar to levels observed in patients with measurable lymphoma treated during 'the pivotal trial'. No correlation was observed between serum rituximab levels achieved in the minimal disease state and the risk of later clinical relapse, nor with the ability to achieve a molecular remission following ASCT.

CONCLUSIONS

The finding that patients treated in minimal disease states and at the time of active disease both achieve similar final serum rituximab concentrations after four infusions suggests that the pharmacokinetics are complex, and may not necessarily correlate with disease burden. The precise factors influencing rituximab clearance in patients with lymphoma are unresolved, and this remains an area of active research.

Bcl-2 clearance: optimising outcomes in follicular non-Hodgkin's lymphoma

The long median survival time of patients with follicular non-Hodgkin's lymphoma (NHL), means that the efficacy of new treatments are difficult to assess in the short term. Bcl-2 is an inhibitor of apoptosis and overexpression of the bcl-2 gene in the blood or bone marrow is a feature in up to 85% of patients with follicular NHL. Levels of bcl-2(+) cells in the peripheral blood or bone marrow therefore are a useful measure of disease status in such patients and can be detected by polymerase chain reaction (PCR). Complete bcl-2 clearance from the bone marrow (molecular remission) following autologous stem cell transplant (ASCT) for follicular NHL is considered to be an important prognostic factor for disease-free survival. Tumour cell contamination of the stem cell grafts used in ASCT is commonly associated with relapse. This can be addressed by purging the stem cell harvest prior to transplantation. Various methods of in vitro purging after stem cell collection have been shown to reduce the level of contamination but yield is invariably reduced and grafts remain bcl-2 positive. However, in vivo purging with rituximab during the process of collection has been used to obtain bcl-2-negative stem cell harvests without compromising the yield. Rituximab is a monoclonal antibody licensed for treatment of relapsed and refractory low-grade or follicular NHL. Rituximab targets the CD20 antigen, which is found on cells of the B cell lineage. When used for in vivo purging it depletes the peripheral blood of CD20-positive cells and prevents contamination by lymphoma cells. Molecular remission, as measured by bone-marrow bcl-2 clearance, has been achieved in 7/7 patients with follicular NHL at 1 year after treatment with ASCT using rituximab as an 'in vivopurse', followed by rituximab maintenance. Early clinical outcomes are also encouraging.

ALVAC-mediated gene transfer is efficient in lymphoid malignancies of T-and early B-cell origin, but not in tumors arising from mature B-cells

Natural attenuation of ALVAC virus in mammals makes it an attractive vector for cancer vaccine therapy of immunocompromised hosts, such as patients with lymphoid malignancies. However, the transduction efficiency of ALVAC constructs in lymphoid tumors has not yet been characterized. We studied a wide spectrum of human T- and B-cell leukemia and lymphomas and found significant heterogeneity of the ALVAC-mediated gene product expression in these tumors. While ALVAC-B7.1, ALVAC-B7.2, or ALVAC-luciferase vectors effectively expressed recombinant genes in malignancies arising from T- or early B-cell precursors, negative or low expression of ALVAC recombinant genes occurred in tumors arising from mature B-cells. We showed that ALVAC-encoded B7.1 or B7.2 was continuously expressed on the infected, and subsequently irradiated, leukemia cells, and only cells with ALVAC-mediated expression of costimulatory molecules (but not unmodified leukemia cells or those infected with the ALVAC-parental vector) induced significant proliferation and IFN-gamma production by alloreactive T-cells. These data provide the rationale for clinical studies using the ALVAC vector system for gene transfer into lymphoid tumors of T- and early B-cell origin to render them more immunogenic, while alternative strategies should be considered for immunotherapy of mature B-cell malignancies.

4-1BBL enhances anti-tumor responses in the presence or absence of CD28 but CD28 is required for protective immunity against parental tumors

A20 is an aggressive BALB/c B cell lymphoma that, despite its expression of B7-2, rapidly forms tumors in syngeneic mice. We have generated A20 transfectants expressing elevated levels of B7-2 (A20/B7-2high) or 4-1BBL (A20/4-1BBL(low,mod,high)) and found that mice which were able to reject the A20/B7-2 or A20/4-1BBL transfectants were also resistant to subsequent systemic challenge with the parental cell line. To assess whether the effectiveness of 4-1BBL in enhancing anti-tumor immunogenicity was dependent on additional signals from B7-CD28 interaction, we injected the A20 variants into BALB/c CD28(-/-) mice. We found that CD28(-/-) mice were able to reject the A20/4-1BBL variants while A20/B7-2 cells formed tumors. However, when the A20/4-1BBL resistant CD28(-/-) mice were systemically challenged with the A20 parental line, tumors formed rapidly. Upon restimulation in vitro, splenocytes from A20/4-1BBL immunized CD28(+/+) mice were able to kill parental tumors whereas splenocytes from CD28(-/-) mice showed a reduction in CTL activity against A20 or A20/4-1BBL targets. Examination of cytokine production by the immunized animals indicated that the CD28(-/-) splenocytes secreted substantially less IL-2 as well as reduced levels of IFN-gamma compared with their CD28(+/+) counterparts. Thus, 4-1BBL expressing tumors are capable of priming CTL responses against 4-1BBL transfected as well as parental tumors in the absence of CD28. However, in the absence of CD28 signaling, the production of cytokines and particularly IL-2 was lower, resulting in a weaker CTL recall response and reduced ability to survive challenge with parental tumor.

Prolonged molecular and clinical remission after treatment of a patient with follicular lymphoma with rituximab

Rituximab is a chimeric anti-CD20 monoclonal antibody that has approval for single agent therapy in the treatment of relapsed/refractory low grade or follicular non-Hodgkin's Lymphoma. In published phase II trials, molecular remissions of PCR detectable t(14;18) disease in the peripheral blood have been reported in up to 62% of patients by three months. We report a case of a patient who achieved prolonged clinical and molecular remission following a single four week course of Rituximab that has exceeded any previous remission achieved with chemo-radiotherapy. The implications of molecular remission as a surrogate of clinical remission and molecular relapse as a harbinger of clinical relapse are reviewed and discussed.

Molecular diagnostics in follicular non-Hodgkin's lymphoma: a review

Follicular lymphoma is a low-grade, indolent non-Hodgkin's lymphoma characterized by the presence of the t(14;18) translocation. The detection of this translocation using polymerase chain reaction techniques has been increasingly studied. However, the diagnostic and prognostic value of detecting t(14;18) rearrangements has been questioned. Translocation has been identified in a significant proportion of healthy donors and patients with nonmalignant diseases. Clearance of t(14;18) rearrangements following conventional treatments, purging of bone marrow/peripheral blood stem cells, and transplantation is associated with improved long-term outcome of patients with follicular lymphoma. Until randomized studies confirm the clinical utility of polymerase chain reaction detection of the translocation, emphasis should be placed on improving the accuracy and reproducibility of polymerase chain reaction techniques, and standardizing assays among laboratories.

Characterization of the human B cell RAG-associated gene, hBRAG, as a B cell receptor signal-enhancing glycoprotein dimer that associates with phosphorylated proteins in resting B cells

Affinity-purified polyclonal antibodies against the hBRAG (human B cell RAG-associated gene) protein were generated to characterize hBRAG at the biochemical level. Immunoblotting and immunoprecipitation experiments with these antibody reagents demonstrate that this protein can be expressed in B cells as a membrane-integrated glycoprotein disulfide-linked dimer. However, both glycosylated and unglycosylated isoforms of hBRAG are detectable with these reagents. Additionally, their use in cell surface biotinylation and flow cytometry reveals subcellular hBRAG pools both at cell surface and intracellular locations. Co-immunoprecipitation experiments with hBRAG antisera detected the association of hBRAG with phosphorylated proteins in resting B cells, including the protein tyrosine kinase Hck, which is subsequently dephosphorylated upon B cell receptor (BCR) ligation. Consistent with its cell surface expression and possible link to BCR signaling, experiments in which alpha-hBRAG antibodies were used to generate early activation signals suggest a modest but specific element of tyrosine phosphorylation occurring through a putative hBRAG receptor. Additional experiments also suggest that hBRAG may be involved in positively enhancing BCR ligation-mediated early activation events. Collectively, these results are consistent with a function for hBRAG as a B cell surface signaling receptor molecule. Coupled with the earlier observation that hBRAG expression correlates with early and late B cell-specific RAG expression, we submit that hBRAG may mediate regulatory signals key to B cell development and/or regulation of B cell-specific RAG expression.

Immunogenicity of whole-cell tumor preparations infected with the ALVAC viral vector

The immunogenicity of recombinant canarypox (ALVAC) viral vectors within murine whole-cell tumor vaccines was evaluated using the T cell thymic lymphoma STF10 and the B16 melanoma. Tumor cells were modified with the recombinant ALVAC vectors and injected into syngeneic mice. Control mice receiving cells alone all developed tumors, while mice injected with tumor variants bearing parental and recombinant vectors either completely rejected their tumors, or exhibited a significant delay in tumor formation. Rechallenge of mice receiving STF10-variant vaccines yielded a protective effect against parental tumor cells only when a modified regimen incorporating two vaccinations was utilized. Notably, the parental ALVAC virus was equivalent to all other recombinant ALVAC viruses in conferring antitumor immunity when using a prime-and-boost protocol. Tumorigenicity experiments in nude mice revealed that the effector mechanism mediating rejection of tumor cells bearing ALVAC vectors is multifactorial, in that the immunogenicity of STF10/ALVAC vaccines is reduced, but not completely abolished in these mice. Finally, in vitro experiments revealed that cytotoxic T cells specific for parental STF10 cells could be generated as a result of in vivo immunization with STF10/ALVAC vaccines.

Functional analysis of the human RAG 2 promoter

Recombination activating genes RAG1 and RAG2 are essential components of V(D)J recombination, a process that generates the specific antigen receptors in lymphocytes. To understand the mechanisms underlying the lineage and developmental regulation of transcription of RAG2, we have characterized the human RAG2 exon 1A promoter. In this study, a series of deletion constructs were used to isolate the promoter while a linker scanning approach was taken to assess functionally relevant cis elements within the promoter. Two regulatory domains were identified. The -140 to -123 region is critical for promoter activity in all cell lines tested. Mutations to the putative Ets (-122 to -118) or to the C/EBP (-137 to -129) consensus core sequences did abrogate promoter activity, although specific DNA/protein interactions remained, as determined by EMSA. The -69 to -48 region demonstrates lineage specific promoter activity. Mutations to an overlapping, BSAP-myb-Ikaros-myb site (-65 to -39) resulted in differential promoter activity in human B and T cells. EMSA analysis of this region showed a B cell specific protein complex. Transfection of BSAP into cell lines trans-activates the human RAG2 promoter. We conclude that transcriptional regulation of the human RAG2 gene is complex, involving both tissue specific and ubiquitous factors, and both proximal and distal regulatory elements.

Mitoxantrone-DHAP with GM-CSF: an active but myelosuppressive salvage therapy for relapsed/refractory aggressive non-Hodgkin's lymphoma

This study was designed to evaluate the efficacy and toxicity of dose intensifying DHAP (dexamethasone, cytarabine and cisplatin) salvage chemotherapy by adding mitoxantrone with GM-GSF support in patients with relapsed or refractory non-Hodgkin's lymphoma (NHL). From March 1992 to January 1995, 22 patients with intermediate and high grade (aggressive) NHL refractory or relapsed after adriamycin containing chemotherapy regimens were treated with M-DHAP+GM-CSF, (dexamethasone 40 mg i.v. days 1-4, cisplatin 100 mg/m2 i.v. by continuous infusion over 24 hours on day 1, cytarabine 2 gm/m2, i.v. every 12 hours for 2 doses on day 2, mitoxantrone 10 mg/m2 i.v. on days 3 and 4 and GM-CSF 250-500 microg/m2 s.c. daily beginning day 5 until absolute neutrophil count recovery. Most patients had poor prognostic factors including primary refractory disease (18/22), bulky disease (12/22), elevated LDH (9/22), or bone marrow involvement (8/22). All 22 patients were evaluable. The overall response rate was 41% (CR 23% and PR 18%). There were three toxic deaths, all related to sepsis. Median progression free survival (PFS) and overall survival (OS) rates were 5.2 months and 11.8 months respectively. At the same time of the analysis two patients were alive after high-dose therapy and bone marrow transplant at 34 and 36 months follow-up and two were alive with disease. The maximal acceptable dosage of mitoxantrone was 10 mg/m2 x 2 due to serious hematologic toxicity. Treatment delays and dose reductions compromised delivering the optimal dose intensity of M-DHAP. A poor prognostic group of patients with refractory or recurrent aggressive lymphoma, many of whom were not eligible for high-dose therapy and stem cell transplantation were treated with repeated cycles of dose intensified DHAP with growth factor support. Although M-DHAP had therapeutic activity even in patients considered to have primary refractory disease, myelosuppression was dose limiting and frequently limited the number of cycles. Therefore, if M-DHAP is to be further evaluated, therapeutic results may be improved further by incorporating strategies to reduce myelotoxicity such as the use of growth factors to reduce platelet transfusion requirements or the use of autologous stem cell support after each cycle.

Stem cell function and engraftment is not affected by "in vivo purging" with rituximab for autologous stem cell treatment for patients with low-grade non-Hodgkin's lymphoma

The chimeric anti-CD20 monoclonal antibody rituximab (Rituxan; IDEC Pharmaceuticals, San Diego, CA, and Genentech, Inc, San Francisco, CA) has recently been approved by the US Food and Drug Administration as single-agent treatment of relapsed/refractory low-grade or follicular non-Hodgkin's lymphoma. Initial results from the pivotal clinical trial revealed that response rates to rituximab were higher in patients who previously had high-dose therapy and autologous stem cell transplantation. We have initiated a clinical trial that combines the use of rituximab with high-dose chemotherapy followed by autologous stem cell transplantation for patients with chemosensitive relapsed follicular small cleaved or mantle cell lymphoma. A unique feature of this study is that in addition to eight maintenance infusions of rituximab after autologous stem cell transplantation, patients also received rituximab 375 mg/m2 2 days before a granulocyte colony-stimulating factor-mobilized stem cell collection as "in vivo purge." We report on preliminary results demonstrating the safety and efficacy of the in vivo purge on 10 patients undergoing stem cell mobilization, nine of whom have already undergone transplantation. The peripheral blood CD34+ counts were 14.92 and 20 x 10(6)/L on day 4 and day 5, respectively, of the stem cell mobilization with granulocyte colony-stimulating factor. This compares with 11.7 and 11.8 x 10(6)/L, respectively, for the control population. The median CD34 stem cell yield in the graft collection was 3.7 x 10(6)/kg in patients receiving rituximab in vivo purge compared with 3.1 x 10(6)/kg in the control population. The target stem cell collection was successfully collected in six of 10 patients in a 1-day single large-volume leukapheresis collection, while two patients required 2 days and the last two patients required 3 days. Functional assays revealed the stem cell colony-forming unit-granulocyte monocyte and burst-forming unit-erythrocyte to be 55 and 44 colonies per plate, respectively, for the patients receiving the in vivo rituximab purge. This compares favorably with 37 and 38.5 colonies per plate, respectively, for the control population. Neutrophil engraftment took a median of 11 days for both cohorts; platelet independence was achieved in 8 days compared with 10 days for the control population. The median number of platelet transfusions was two for patients receiving rituximab and 2.5 for the control group. Assessment of serum cytokines immediately before the rituximab infusion during the stem cell mobilization and immediately after revealed a twofold to sevenfold increase in interleukin-1beta, tumor necrosis factor-alpha, and interleukin-6. The polymerase chain reaction analysis for minimal residual disease in stem cell collections and in peripheral blood and bone marrow samples of these patients will help to determine the efficacy of rituximab in vivo purge on disease progression.

Delivery of full dose CHOP chemotherapy to elderly patients with aggressive non-Hodgkin's lymphoma without G-CSF support

Because of evidence that failure to deliver full dose CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) may compromise the outcome of elderly patients with aggressive non-Hodgkin's lymphoma (NHL), we attempted to deliver full dose CHOP to these patients. The objective of this review was to assess the relative received dose intensity (ARRDI), toxicity and outcome of elderly patients treated with curative intent with CHOP at our centre. Charts were reviewed of all patients > or = 65 years with newly diagnosed aggressive NHL referred to the Toronto-Sunnybrook Regional Cancer Centre (TSRCC) for initial management from 1990-1995 before routine use of G-CSF. Sixty eligible patients were identified. 31 received CHOP +/- radiation (XRT), 9 other curative treatment and 20, palliative treatment. The mean ARRDI calculated on 29/31 patients receiving CHOP was .86; 41%=1.0, 24%=.90-.99, 14%=.75-.89 and 21%=<.75. During 141 cycles of CHOP. 17 (12%) episodes of febrile neutropenia (FN) occurred in 14 (45%) patients and other grade 3/4 toxicity occurred in <10% of patients. There were 3 (10%) toxic deaths. Sixteen (52%) patients required a total of 29 admissions to hospital for FN (59%) or other causes. Of the 31 patients, 16 (52%) achieved a complete remission (CR), 7 (23%) a partial remission-1 (PR-1), 2 (6%) a partial remission-2 (PR-2), 1 (3%) had no response (NR), 2 (6%) had progressive disease and 3 (10%) were not evaluable (NE). The median progression free survival (PFS) and overall survival (OS) were (16+) months and (24.5) months respectively. We found that physician biases resulted in the selection of; younger patients (median 71 vs. 80 years), patients with a better ECOG performance status (> or =2, 13% vs. 50%) and patients with less co-morbid illness (42% vs. 90%) for attempt at curative treatment with CHOP chemotherapy. Age was never the sole reason for offering palliative treatment. In conclusion, a subset of patients over the age of 65 with aggressive NHL, who have a good performance status and minimal co-morbid illness can tolerate full dose CHOP chemotherapy without G-CSF support. Future strategies should emphasize full dose treatment with curative intent with minimization of both hematologic and non-hematologic toxicity. Clinical studies are required to determine whether routine G-CSF support will reduce toxicity or improve outcome in this group of patients.

Comparison of CMV, RSV, SV40 viral and Vlambda1 cellular promoters in B and T lymphoid and non-lymphoid cell lines

Determining the activity of viral and cellular regulatory elements in B or T lymphoid cell lines would facilitate appropriate utilization of the regulatory sequences for gene transfer- and expression-dependent applications. We have compared the activity of the CMV, RSV and SV40 viral promoter/enhancers as well as the Vlambda1 cellular promoter, in three B cell lines (REH, SMS-SB, C3P), three T cell lines (CEM, Jurkat, ST-F10), and two non-lymphoid cell lines (K-562, HeLa) using the luciferase reporter gene. In B cell lines, the activity of the CMV promoter/enhancer construct was the highest ranging from 10- to 113-fold greater than that of SV40. In contrast, in T cell lines the RSV promoter/enhancer activity was 11-65-fold higher than that of SV40. The Vlambda1 promoter activity was close to that of SV40 promoter/enhancer in most of the cell lines tested. We conclude that CMV and RSV promoter/enhancers contain stronger regulatory elements than do the SV40 and Vlambda1 for expression of genes in lymphoid cell lines.

4-1BBL cooperates with B7-1 and B7-2 in converting a B cell lymphoma cell line into a long-lasting antitumor vaccine

A20 is a B cell lymphoma that constitutively expresses the costimulatory molecule B7-2 yet grows readily as a tumor in syngeneic BALB/c mice. We have compared the tumorigenicity of A20 variants expressing either B7-1 (A20/B7-1) or B7-2 (A20/B7-2) with an A20 variant expressing B7-1 and B7-2 with 4-1BBL (A20/4-1BBL), a costimulatory member of the TNF family. Mice injected with tumors expressing the vector backbone (A20/CMV) or B7-1 developed tumors within 25 days of s.c. injection. In contrast, mice injected with A20/4-1BBL were tumor free for the 150-day follow-up period, while 25% of mice injected with A20/B7-2 developed tumors. Tumorigenicity experiments using nude mice indicated the requirement for T cells for variant rejection. Almost all mice that resisted the initial tumor challenge were resistant to further challenge with the parental tumor. Splenocytes from these mice showed high CTL lytic activity against the parental tumor, A20, as well as the syngeneic BALB/c lymphoma K46J, but showed background levels of lytic activity against the congenic SCID thymoma line ST-D2 or the allogeneic EL4 thymoma. In vitro blocking experiments with anti-B7-1 plus anti-B7-2 and/or soluble 4-1BB receptor showed B7-1, B7-2, and 4-1BBL all contributed to the CTL activity. Thus, the data show that neither B7-1 or B7-2 alone can confer full immunogenicity to the A20 lymphoma but that the addition of 4-1BBL results in a tumor that is highly immunogenic and can confer long-lasting protection against challenge with parental tumor in vivo.

Human lymphoblastoid cell lines expressing mutant p53 exhibit decreased sensitivity to cisplatin-induced cytotoxicity

Human lymphoblastoid cells were transfected with expression vectors containing p53 cDNA mutated at either codon 135 or 246. The cells were subjected to cisplatin treatment or gamma-radiation and observed for changes in the cell cycle arrest and apoptosis. We found that compared to the parental cell line, cells overexpressing mutant p53 (either 246val or 135ser) exhibited decreased apoptosis in response to gamma-radiation or cisplatin as measured by: propidium iodide (PI) staining of the cellular DNA (cell cycle analysis) and decrease in PARP (poly ADP-ribose polymerase) cleavage as detected by Western blotting. Interestingly the cells expressing mutant p53(135ser) protein were less resistant to cisplatin-induced apoptosis than the p53(246val)-bearing cell line. A significant decrease in the G1/S arrest assayed by bromodeoxyuridine and PI staining (cell cycle/proliferation assay) was also observed in response to irradiation and cisplatin in cell lines expressing either of the mutant p53 constructs. A lower basal level and reduced magnitude of protein induction of the cell cycle inhibitor p21/Waf1 was seen both after cisplatin and gamma-radiation treatment in the mutant p53 expressing lymphoblastoid variant when compared to the wild type p53 parental cell line but induction of the p53 regulator MDM2 was comparable in both. No increase in basal levels of Bc12 protein in wild type or mutant p53 expressing cells was observed in response to cisplatin or irradiation. Unexpectedly, following cisplatin treatment we observed an increase in mutant and wild type p53 RNA steady state levels in addition to increased levels of p53 protein. These results suggest that irradiation or cisplatin treatment may not only stabilize wild type p53 protein but also may increase the steady state p53 RNA levels. Finally these results indicate that both irradiation and cisplatin should be used with caution in the treatment of lymphoid tumors bearing mutations of p53.

Isolation of genes negatively or positively co-expressed with human recombination activating gene 1 (RAG1) by differential display PCR (DD RT-PCR)

Differential display PCR (DD RT-PCR) has been extensively used for analysis of differential gene expression, but continues to be hampered by technical limitations that impair its effectiveness. In order to isolate novel genes co-expressing with human RAG1, we have developed an effective, multi-tiered screening/purification approach which effectively complements the standard DD RT-PCR methodology. In 'primary' screens, standard DD RT-PCR was used, detecting 22 reproducible differentially expressed amplicons between clonally related cell variants with differential constitutive expression of RAG mRNAs. 'Secondary' screens used differential display (DD) amplicons as probes in low and high stringency northern blotting. Eight of 22 independent DD amplicons detected nine independent differentially expressed transcripts. 'Tertiary' screens used reconfirmed amplicons as probes in northern analysis of multiple RAG-and RAG+sources. Reconfirmed DD amplicons detected six independent RAG co-expressing transcripts. All DD amplicons reconfirmed by northern blot were a heterogeneous mixture of cDNAs, necessitating further purification to isolate single cDNAs prior to subcloning and sequencing. To effectively select the appropriate cDNAs from DD amplicons, we excised and eluted the cDNA(s) directly from regions of prior northern blots in which differentially expressed transcripts were detected. Sequences of six purified cDNA clones specifically detecting RAG co-expressing transcripts included matches to portions of the human RAG2 and BSAP regions and to four novel partial cDNAs (three with homologies to human ESTs). Overall, our results also suggest that even when using clonally related variants from the same cell line in addition to all appropriate internal controls previously reported, further screening and purification steps are still required in order to efficiently and specifically isolate differentially expressed genes by DD RT-PCR.

hBRAG, a novel B cell lineage cDNA encoding a type II transmembrane glycoprotein potentially involved in the regulation of recombination activating gene 1 (RAG1)

The different display reverse transcription-PCR (DD RT-PCR) technique was used to identify novel cDNA detecting mRNA transcripts co-expressed with human recombination activating gene-1 (RAG1). A 5.0-kb transcript detected by the differential display amplicon 3G1 was found to correlate strongly with RAG1 mRNA expression in various human cell lines. Subsequent screenings of a pre-B cDNA library with 3G1 led to the identification of a complete cDNA we have termed hBRAG (human B-cell RAG-Associated Gene). The hBRAG cDNA encodes a 503-amino acid (aa) protein with no known homology to any nucleotide or protein sequence. The predicted molecular mass of 55 kDa was confirmed by in vitro translation. Based on sequence analysis, the predicted open reading frame encodes for a type II transmembrane spanning glycoprotein with the N-terminal 81 -aa in the cytoplasm, a 17-aa transmembrane domain, and a C-terminal 405-aa extracellular domain with four potential N-glycosylation sites. Northern blot analysis indicated a close association of the 5.0-kb hBRAG mRNA transcript with RAG1 in numerous human pro-B, pre-B and mature B cell lines assessed, but not in human T cell lines. In human tissues, hBRAG is expressed at highest levels in B cell-enriched tissues, but is not expressed in fetal or adult thymus. Southern blotting analysis revealed that this gene is conserved across eukaryotes, is expressed as a single copy in the human genome, and is likely not a multigene family member. The hBRAG gene was localized to the long arm of chromosome 10 (10q26). Transfection of the full-length hBRAG cDNA increased levels of human RAG1 transcripts in the B cell line OCI LY8-C3P, but not in the non-lymphoid line K562, suggesting a B cell-specific role for the hBRAG product in regulating RAG expression.

Association of serum Rituximab (IDEC-C2B8) concentration and anti-tumor response in the treatment of recurrent low-grade or follicular non-Hodgkin's lymphoma

BACKGROUND

Monoclonal antibodies are being utilized for treatment of patients with low-grade non-Hodgkin's lymphoma as well as other cancers. Results from phase I and II clinical studies has shown that the chimeric monoclonal antibody Rituximab has minimal toxicity and significant therapeutic activity in low grade non-Hodgkin's lymphoma.

PATIENTS AND METHODS

We have recently reported on a multicentre pivotal phase III clinical trial involving 166 patients with recurrent low-grade lymphoma who were treated with four infusions of Rituximab. Eighty patients (48%) achieved objective responses including 10 patients (6%) with complete responses. Overall, 126 patients (76%) had a > or = 20% reduction in overall tumor size. The median response duration and time to progression are 11.6 and 13.2 months, respectively. The infusional and long term toxicities were limited.

RESULTS

In this report we describe the pharmacokinetic data obtained on these patients. Measurable concentrations of Rituximab were detected in all patients after the first infusion and increased throughout the treatment course. The half-life of the monoclonal antibody increased from 76.3 hours after the first infusion to 205.8 hours after the fourth infusion and was concomitant with a four-fold decrease in the antibody clearance. At three months and six months post-treatment, the median Rituximab serum levels were 20.3 micrograms/ml (range 0.0 to 96.8 micrograms/ml in 104 patients) and 1.3 micrograms/ml (range 0.0-28.7 micrograms/ml in 13 patients), respectively. A statistically significant correlation was found between the median antibody concentration and response for multiple time points during the treatment and followup. The mean serum antibody concentration was also inversely correlated with measurements of tumor bulk and with the number of circulating B cells at baseline.

CONCLUSIONS

We conclude that Rituximab is therapeutically effective against B-cell lymphoma. Pharmacokinetic data suggests that certain subsets of patients may possibly benefit from increased dosing and studies to address this are currently underway.

Cytomegalovirus retinitis and low-grade non-Hodgkin's lymphoma: case report and review of the literature

Patients with non-Hodgkin's lymphoma may develop retinal or choroidal lesions during the course of their disease. New immunosuppressive therapies currently used in reticuloendothelial malignancies have increased the incidence of opportunistic infections in this patient population. The differentiation of lymphomatous infiltration from opportunistic infection as a cause of chorioretinal infiltrates is critical, as the treatments are fundamentally different. We report a case of a patient with non-Hodgkin's lymphoma who developed a chorioretinal infiltrate that was initially thought to represent progressive disease. The patient received radiation treatment appropriate for intraocular lymphoma. The lesion progressed further and after reevaluation a diagnosis of cytomegalovirus retinitis was made and therapy initiated. Review of the literature for intraocular lymphoma and cytomegalovirus retinitis is provided and diagnostic strategies are described. We recommend analysis of intraocular fluid when there is difficulty in clinically differentiating intraocular lymphoma from opportunistic infection.

Enhanced immunogenicity of B cell lymphoma genetically engineered to express both B7-1 and interleukin-12

The A20 murine B cell lymphoma was transfected with B7-1 and subsequently these variants and vector control variants were retrovirally infected to express murine interleukin-12 (mIL-12). In vitro data showed that the B7-1 variants enhanced secretion of IL-2 and IL-4 by allogeneic T cells in mixed lymphocyte tumor cultures. While IL-12 variants stimulated IFN-gamma, variants expressing both B7-1 and IL-12 stimulated IFN-gamma, IL-2, and IL-4 secretion. Tumorigenicity experiments showed that whereas B7-1 delayed tumor onset, only the mIL-12 variants with or without B7-1 were completely rejected in syngeneic hosts. In addition, tumor-free mice were protected against subsequent challenge with the parental unmodified cells and had enhanced cytotoxic T lymphocyte (CTL) lysis activity. Results from minimal disease mixing experiments demonstrated that only the A20/B7-1/mIL-12 variant was able to reject A20 unmodified cells inoculated at the same site, whereas prolonged survival was observed when the A20 parental cells were inoculated at different sites. Depletion studies and injections into nu-/nu- mice demonstrated that both CD4+ and CD8+ T cells may mediate immunity. These data suggest that vaccinations with tumor cells genetically modified to express both B7-1 and IL-12 may alter cytokine profiles and generate CTL activity and, thus, the mechanisms of enhanced antitumor immunity may be multifactorial.

Cloning and characterization of the human recombination activating gene 1 (RAG1) and RAG2 promoter regions

Recombination activating gene 1 (RAG1) and RAG2 are the essential and tissue-specific components of V(D)J recombination. We have characterized the genomic organization of the human RAG locus, mapped the transcriptional initiation sites, and partially sequenced and performed functional reporter assays on the 5' flanking regions of human RAG1 and RAG2. Transcription initiation sites were mapped by rapid amplification of 5' cDNA ends, primer extension, and/or RNase protection in normal thymocytes, three pre-B cell lines, and a mature B cell line. A single promoter region was used for RAG1 transcription. In contrast, transcription of RAG2 initiates at two distinct regions of the genome. The 5'-flanking region of the human RAG2 gene is TATA-less; however, there is a GATAA consensus at position -34 with respect to the major transcriptional initiation site of RAG1. Promoter regions of human RAG1 and RAG2 are active in both lymphoid and nonlymphoid cell lines, suggesting that an outside regulatory element is probably involved in the tissue-specific transcriptional regulation of the RAG genes.

Cloning and characterization of the human recombination activating gene 1 (RAG1) and RAG2 promoter regions

Recombination activating gene 1 (RAG1) and RAG2 are the essential and tissue-specific components of V(D)J recombination. We have characterized the genomic organization of the human RAG locus, mapped the transcriptional initiation sites, and partially sequenced and performed functional reporter assays on the 5' flanking regions of human RAG1 and RAG2. Transcription initiation sites were mapped by rapid amplification of 5' cDNA ends, primer extension, and/or RNase protection in normal thymocytes, three pre-B cell lines, and a mature B cell line. A single promoter region was used for RAG1 transcription. In contrast, transcription of RAG2 initiates at two distinct regions of the genome. The 5'-flanking region of the human RAG2 gene is TATA-less; however, there is a GATAA consensus at position -34 with respect to the major transcriptional initiation site of RAG1. Promoter regions of human RAG1 and RAG2 are active in both lymphoid and nonlymphoid cell lines, suggesting that an outside regulatory element is probably involved in the tissue-specific transcriptional regulation of the RAG genes.

Enhanced CTL responses mediated by plasmid DNA immunogens encoding costimulatory molecules and cytokines

In the course of examining epitope-specific CTL responses to intramuscular plasmid DNA immunization with influenza nucleoprotein (NP)-expressing vectors, a nonimmunogenic mutant NP (NP(o)) was identified. The coding region of NP(o) differed from the wild-type A/PR/8/34 NP sequence (designated NP(v)) by three amino acid alterations in the carboxyl-terminal portion of the molecule remote from the H-2K(d) epitope (147-155) being monitored. Correction of these mutations restored the immunogenicity of the native sequence, indicating that sequence alterations remote from the CTL epitope in question can profoundly influence its immunogenicity. In an effort to identify general, nonstructural means of enhancing the CTL response to weak plasmid DNA immunogens, vectors were constructed expressing NP(o) in tandem with the costimulatory molecules B7-1 or B7-2. Co-linear expression of NP(o) with B7-2, but not B7-1, significantly increased the NP epitope-specific CTL response. In addition, coinjection of these NP(o) plasmids with granulocyte-macrophage CSF- and/or IL-12-expressing vectors also restored near native NP-specific CTL responses. Thus, the coexpression of certain costimulatory molecules and/or cytokines, in concert with a non-self gene delivered as an intramuscular plasmid DNA immunogen, can significantly enhance Ag-specific CTL responses.

Enhanced CTL responses mediated by plasmid DNA immunogens encoding costimulatory molecules and cytokines

In the course of examining epitope-specific CTL responses to intramuscular plasmid DNA immunization with influenza nucleoprotein (NP)-expressing vectors, a nonimmunogenic mutant NP (NP(o)) was identified. The coding region of NP(o) differed from the wild-type A/PR/8/34 NP sequence (designated NP(v)) by three amino acid alterations in the carboxyl-terminal portion of the molecule remote from the H-2K(d) epitope (147-155) being monitored. Correction of these mutations restored the immunogenicity of the native sequence, indicating that sequence alterations remote from the CTL epitope in question can profoundly influence its immunogenicity. In an effort to identify general, nonstructural means of enhancing the CTL response to weak plasmid DNA immunogens, vectors were constructed expressing NP(o) in tandem with the costimulatory molecules B7-1 or B7-2. Co-linear expression of NP(o) with B7-2, but not B7-1, significantly increased the NP epitope-specific CTL response. In addition, coinjection of these NP(o) plasmids with granulocyte-macrophage CSF- and/or IL-12-expressing vectors also restored near native NP-specific CTL responses. Thus, the coexpression of certain costimulatory molecules and/or cytokines, in concert with a non-self gene delivered as an intramuscular plasmid DNA immunogen, can significantly enhance Ag-specific CTL responses.

Immunosuppressive toxicity of CAMPATH1H monoclonal antibody in the treatment of patients with recurrent low grade lymphoma

We have studied, as part of a group of international multicenter phase II clinical trials, the toxicity and effectiveness of CAMPATH1H administered intravenously three times a week in an outpatient setting to patients with recurrent or progressive low grade lymphoma. We report here on the toxicity and therapeutic results of the first seven patients treated before the study was closed prematurely because of unacceptable toxicity. Classical complete or partial responses of treatment were seen in three of seven patients. One complete response lasted 8.5 months and the other complete response is ongoing at 1 year. Responses occurred in nodal sites as well as in skin and peripheral blood. The first three or four antibody infusions in each patient was associated with grade 1 or 2 side-effects including rigor, fever, facial flushing, nausea, vomiting, hives, wheezes, hypotension, and/or diarrhea but these subsequently decreased or disappeared. The most significant toxicity was profound lymphopenia and associated infection, usually viral. Six of seven patients had culture or serologically documented infections and four patients had two or more such episodes. All infections responded to temporary discontinuation of antibody therapy and appropriate antiviral or antibiotic agents. We conclude that CAMPATH1H monoclonal antibody has therapeutic activity against low grade non-Hodgkin's lymphoma but that this activity is limited by marked lymphopenia and an unacceptably high frequency of serious infection at the dose and schedule used in this trial.

Up-regulation of recombination activating gene expression by signal transduction through the surface Ig receptor

Recent evidence has demonstrated that a signal transduced through the lymphocyte Ag receptor may regulate the expression of the recombination activating genes (RAG). Although several groups have shown that such a signal may be required to down-regulate RAG-1 and RAG-2 after a functional Ag receptor has been generated in early mature T or B cells, recently it has been suggested that under some circumstances, cross-linking the B cell Ag receptor may result in up-regulation of RAG expression. To study this possibility, we used a unique set of cell variants isolated from a human mature B cell line, which differ in their expression of both the surface Ig receptor (sIg) and RAG-1 and RAG-2 genes. Two forms of stimulation were employed to generate a signal; either a soluble F(ab')2 anti-mu fragment or the combination of PMA and ionomycin. Northern blot analysis demonstrated that RAG-1 mRNA levels were increased in sIg+ variants after cross-linking with anti-mu. Increases were also observed in all variants after stimulation with PMA and ionomycin. Further analysis of cross-linked sIg+ variants suggests that the observed up-regulation in RAG expression was a reversible event. Furthermore, we have determined that both increased transcription and transcript stabilization contributed to this inducible up-regulation. We thus describe a mature B cell line in which RAG expression is up-regulated after sIg cross-linking. This finding is discussed in the context of its potential role in situations where sIg+ B cells may undergo secondary rearrangements for the purpose of "editing" their sIg receptors.

Up-regulation of recombination activating gene expression by signal transduction through the surface Ig receptor

Recent evidence has demonstrated that a signal transduced through the lymphocyte Ag receptor may regulate the expression of the recombination activating genes (RAG). Although several groups have shown that such a signal may be required to down-regulate RAG-1 and RAG-2 after a functional Ag receptor has been generated in early mature T or B cells, recently it has been suggested that under some circumstances, cross-linking the B cell Ag receptor may result in up-regulation of RAG expression. To study this possibility, we used a unique set of cell variants isolated from a human mature B cell line, which differ in their expression of both the surface Ig receptor (sIg) and RAG-1 and RAG-2 genes. Two forms of stimulation were employed to generate a signal; either a soluble F(ab')2 anti-mu fragment or the combination of PMA and ionomycin. Northern blot analysis demonstrated that RAG-1 mRNA levels were increased in sIg+ variants after cross-linking with anti-mu. Increases were also observed in all variants after stimulation with PMA and ionomycin. Further analysis of cross-linked sIg+ variants suggests that the observed up-regulation in RAG expression was a reversible event. Furthermore, we have determined that both increased transcription and transcript stabilization contributed to this inducible up-regulation. We thus describe a mature B cell line in which RAG expression is up-regulated after sIg cross-linking. This finding is discussed in the context of its potential role in situations where sIg+ B cells may undergo secondary rearrangements for the purpose of "editing" their sIg receptors.

Rearrangement and expression of the human psi C lambda 6 gene segment results in a surface Ig receptor with a truncated light chain constant region

The constant region of the human Ig lambda locus consists of seven tandemly organized J-C gene segments. Although it has been established that the J-C lambda 1, J-C lambda 2, J-C lambda 3, and J-C lambda 7 gene segments are functional, and code for the four distinct Ig lambda isotypes found in human serum, the J-C lambda 4, J-C lambda 5, and J-C lambda 6 gene segments are generally considered to be pseudogenes. Although one example of a functional J-C lambda 6 gene segment has been documented, in the majority of cases, J-C lambda 6 is rendered nonfunctional by virtue of a single duplication of four nucleotides, creating a premature translational arrest. We show here that rearrangements to the J-C lambda 6 gene segment do occur, and that such a rearrangement encodes an Ig lambda protein that lacks the terminal end of the constant region. We also show that this truncated protein is expressed on the surface with the IgH chain, creating an unusual surface Ig (sIg) receptor (sIg delta CL). Cells that express this receptor on the surface do so at significantly reduced levels compared with clonally related variants, which express sIg receptors with conventional Ig lambda L chains. However, the effects of sIg cross-linking on tyrosine phosphorylation and surface expression of the CD25 and CD71 Ags are similar in cells that express conventional sIg receptors and in those that express sIg delta CL receptors, suggesting that the latter could possibly function as an Ag receptor.

Rearrangement and expression of the human psi C lambda 6 gene segment results in a surface Ig receptor with a truncated light chain constant region

The constant region of the human Ig lambda locus consists of seven tandemly organized J-C gene segments. Although it has been established that the J-C lambda 1, J-C lambda 2, J-C lambda 3, and J-C lambda 7 gene segments are functional, and code for the four distinct Ig lambda isotypes found in human serum, the J-C lambda 4, J-C lambda 5, and J-C lambda 6 gene segments are generally considered to be pseudogenes. Although one example of a functional J-C lambda 6 gene segment has been documented, in the majority of cases, J-C lambda 6 is rendered nonfunctional by virtue of a single duplication of four nucleotides, creating a premature translational arrest. We show here that rearrangements to the J-C lambda 6 gene segment do occur, and that such a rearrangement encodes an Ig lambda protein that lacks the terminal end of the constant region. We also show that this truncated protein is expressed on the surface with the IgH chain, creating an unusual surface Ig (sIg) receptor (sIg delta CL). Cells that express this receptor on the surface do so at significantly reduced levels compared with clonally related variants, which express sIg receptors with conventional Ig lambda L chains. However, the effects of sIg cross-linking on tyrosine phosphorylation and surface expression of the CD25 and CD71 Ags are similar in cells that express conventional sIg receptors and in those that express sIg delta CL receptors, suggesting that the latter could possibly function as an Ag receptor.

Sequence preservation of the third exon of the bcl-2 gene in non-Hodgkin's lymphoma: absence of somatic hypermutation

The t(14;18) translocation juxtaposes the bcl-2 gene on chromosome 18 to a joining (J) gene segment of the immunoglobulin heavy chain gene (IgH) on chromosome 14. Up to 85% of non-Hodgkin's lymphomas (NHL) are t(14;18) positive. Recent reports have documented point mutations in the second exon of translocated bcl-2 alleles and postulated that immunoglobulin variable (V) region somatic hypermutation, related to Ig sequences approximately 250 Kb downstream, may be mediating these mutations. We have examined the third exon of bcl-2, directly adjacent to Ig sequences in the t(14;18), for point mutations. In particular, we studied the translated region of exon 3 in 45 NHLs by SSCP analysis and failed to detect a single point mutation. Further, we sequenced eleven t(14;18) breakpoints, including both bcl-2 and JH sequences, and detected only one point mutation, in a JH-derived sequence. We conclude that immunoglobulin V region somatic hypermutation does not induce point mutations into the t(14;18) breakpoint region or into the translated region of the third exon of bcl-2 alleles involved in the t(14;18) translocation, conserving the membrane insertion properties of the carboxyl tail of this protein.

A mutated promoter of a human Ig V lambda gene segment is associated with reduced germ-line transcription and a low frequency of rearrangement

Several explanations for skewed variable (V) gene usage in the expressed Ig repertoire have been put forth, ranging from cellular selection to differences in the actual rearrangement frequencies of individual V gene segments. In this report we study V gene usage in human Ig lambda rearrangements in an in vitro system, thus largely avoiding selective forces. We find a significant bias in V lambda gene usage in these rearrangements. Through deletional mapping on Southern blots, the relative chromosomal organization of members of the V lambda I, V lambda V, V lambda VI, and V lambda X families was established, which revealed that the bias in V lambda gene usage cannot be readily explained by chromosomal location. We further found that the qualities of the recombination signal sequences, nucleotide sequence/regions of homology of the coding ends or the CpG methylation patterns, do not explain this bias either. We do, however, find a direct correlation between a low frequency of rearrangement and a reduced level of germ-line transcription of a particular V gene segment. We were able to identify three mutations in the octamer motif of the promoter region of this V gene segment. This is the first report showing that mutations in important transcriptional control motifs of individual V gene segments are associated with reduced levels of transcription in the germ line, which in turn may influence the frequency of rearrangement and the shaping of the expressed Ig repertoire.

A mutated promoter of a human Ig V lambda gene segment is associated with reduced germ-line transcription and a low frequency of rearrangement

Several explanations for skewed variable (V) gene usage in the expressed Ig repertoire have been put forth, ranging from cellular selection to differences in the actual rearrangement frequencies of individual V gene segments. In this report we study V gene usage in human Ig lambda rearrangements in an in vitro system, thus largely avoiding selective forces. We find a significant bias in V lambda gene usage in these rearrangements. Through deletional mapping on Southern blots, the relative chromosomal organization of members of the V lambda I, V lambda V, V lambda VI, and V lambda X families was established, which revealed that the bias in V lambda gene usage cannot be readily explained by chromosomal location. We further found that the qualities of the recombination signal sequences, nucleotide sequence/regions of homology of the coding ends or the CpG methylation patterns, do not explain this bias either. We do, however, find a direct correlation between a low frequency of rearrangement and a reduced level of germ-line transcription of a particular V gene segment. We were able to identify three mutations in the octamer motif of the promoter region of this V gene segment. This is the first report showing that mutations in important transcriptional control motifs of individual V gene segments are associated with reduced levels of transcription in the germ line, which in turn may influence the frequency of rearrangement and the shaping of the expressed Ig repertoire.

Immunoglobulin heavy chain variable gene utilization in human large cell and Burkitt's lymphoma cell lines

To elucidate the genetic origins of human B-cell lymphomas, we have used northern analysis to establish the profile of immunoglobulin heavy chain variable region (VH) gene utilization in 14 Burkitt's and 10 large cell lymphomas. Our results indicate that the pattern of VH gene subgroup expression in these tumors is similar to the distribution of VH subgroups utilized in the normal repertoire of adult peripheral blood B cells. This finding suggests that these 2 types of lymphomas originate from a relatively diverse population of B cells and that antigenic drive, at least by a single antigen species, does not represent a major etiologic factor in the genesis of this class of B-cell neoplasms. However, the utilization of genes from the VH3 subgroup by 65% of the lymphomas examined in this study raises the possibility that antibodies directed against conserved VH3 subgroup determinant(s) may be of value in treating at least some affected individuals.

Identification of a new human V lambda gene family--V lambda X

Although approximately 40% of Ig light chains in human sera are of the Ig lambda isotype, until recently very little was known about the human Ig lambda gene locus. The genomic structure of the Ig lambda C region has been determined and consists of seven tandemly organized J-C lambda segments. The structure of the region containing the Ig lambda V gene segments is less well defined. Based on amino acid and nucleotide sequence homologies, the V lambda gene segments isolated have been grouped into nine families. Here we report on the isolation of a V lambda gene from the functional rearrangement of a human B lymphoma cell line that has less than 71% nucleotide sequence and 57% deduced amino acid sequence homology to any known V lambda gene. According to the current classification schemes, this gene does not belong to any existing V lambda family. Thus we suggest that this gene belongs to a new V lambda family, V lambda X. The genomic counterpart of the rearranged V lambda gene, and a second member of the family were isolated. The second member is a pseudogene. Southern analysis suggests that the V lambda X family is a small family. The functional V lambda X gene has a consensus heptamer and a nonamer that differs at two sites from the consensus recombination signal sequence. The promoter region contains a consensus TATA box and an octamer that diverge from the consensus sequence by two base pairs.

Identification of a new human V lambda gene family--V lambda X

Although approximately 40% of Ig light chains in human sera are of the Ig lambda isotype, until recently very little was known about the human Ig lambda gene locus. The genomic structure of the Ig lambda C region has been determined and consists of seven tandemly organized J-C lambda segments. The structure of the region containing the Ig lambda V gene segments is less well defined. Based on amino acid and nucleotide sequence homologies, the V lambda gene segments isolated have been grouped into nine families. Here we report on the isolation of a V lambda gene from the functional rearrangement of a human B lymphoma cell line that has less than 71% nucleotide sequence and 57% deduced amino acid sequence homology to any known V lambda gene. According to the current classification schemes, this gene does not belong to any existing V lambda family. Thus we suggest that this gene belongs to a new V lambda family, V lambda X. The genomic counterpart of the rearranged V lambda gene, and a second member of the family were isolated. The second member is a pseudogene. Southern analysis suggests that the V lambda X family is a small family. The functional V lambda X gene has a consensus heptamer and a nonamer that differs at two sites from the consensus recombination signal sequence. The promoter region contains a consensus TATA box and an octamer that diverge from the consensus sequence by two base pairs.

Significance of a partial or slow response to front-line chemotherapy in the management of intermediate-grade or high-grade non-Hodgkin's lymphoma: a literature review

PURPOSE

The purpose of this review was to assess the outcome of patients with non-Hodgkin's lymphoma (NHL) who achieve an incomplete or slow response to front-line chemotherapy and to determine whether salvage treatment with intensive combination chemotherapy with or without autologous bone marrow transplantation (ABMT) is successful in such patients.

METHODS

A comprehensive literature search of studies using combination chemotherapy for the front-line therapy of advanced-stage intermediate- and high-grade NHL and for salvage therapy of patients with a partial response (PR) was reviewed.

RESULTS

The median survival duration of patients with a PR ranged between 5 to 14 months, while the median survival duration of patients with a complete response (CR) was not reached in many studies. For patients in CR, the probability of survival at 24 months ranged between 0.79 to 1, while for patients in PR it ranged from 0 to 0.31. The rapidity of a response to front-line therapy was often found to be of prognostic importance. Patients who relapsed after a PR to front-line therapy had similar outcomes to intensive salvage therapy as those who relapsed after a CR. ABMT performed immediately after a PR to induction therapy, before progressive disease occurred, resulted in high CR rates in nonrandomized studies.

CONCLUSION

Patients with aggressive NHL who experience a PR or who respond slowly to front-line chemotherapy have a poor prognosis. Early introduction of dose-intensive salvage therapy before the development of progressive disease may benefit patients with a PR and requires testing in randomized clinical trials.

Immunoglobulin somatic variation; studies of receptor editing in a human B cell lymphoma

In order to study mechanisms of immunoglobulin somatic variation in committed immunoglobulin (Ig) expressing B cells, we used the fluorescent activated cell sorter to isolate rare variants from a surface Ig positive (sIg+) diffuse large cell B lymphoma cell line (mu lambda+). These variants were either negative for sIg expression (sIg-) or expressed sIg which differed from the original parental tumor cell line, both in idiotypes and Ig lambda isotypes (sIg+Id-). In the following report we review the results from the studies of these variants. DNA analysis showed that all variants had new Ig lambda gene rearrangements, which had occurred either on a previously excluded allele, or on the productively rearranged allele of the parental cell line. The sIg- variants, which had undergone nonfunctional Ig lambda rearrangements on the expressed parental allele, and thereby deleted the productive rearrangement, continued to functionally rearrange the same allele and regenerated sIg expression. While the parental cell line expressed low levels of the recombination activating genes, RAG1 and RAG2, expression of these genes were considerably upregulated in both the immunoglobulin negative and the idiotypic variants. Somatic immunoglobulin V gene hypermutation did not contribute to the observed immunoglobulin somatic variation. These results demonstrate that, through differential expression of the RAG genes, sIg+ B cells are able to somatically alter their sIg receptors through secondary Ig lambda gene rearrangements. This mechanism may allow B cells with non-selectable, or auto-reactive, antigen receptors to alter these receptors (receptor editing). Ongoing Ig gene rearrangement may limit the usefulness of immunotherapeutic approaches directed at the antigen receptor in some diffuse large cell lymphomas.

Alterations of the p53 tumor suppressor gene in diffuse large cell lymphomas with translocations of the c-MYC and BCL-2 proto-oncogenes

Diffuse large cell lymphomas are aggressive tumors of B-cell origin. In some cases they arise from low-grade follicular lymphomas carrying the t(14;18) translocation, an event that leads to the overexpression of the BCL-2 gene product. More frequently, however, they lack the t(14;18) translocation. Rearrangements of the c-MYC proto-oncogene and mutations of the p53 tumor suppressor gene have also been documented in these lymphomas. This study examines the extent to which alterations in the BCL-2, c-MYC, and p53 genes co-exist within individual lymphomas. Eight diffuse large cell lymphoma cell lines and 11 diffuse large cell lymphoma tumors were assessed for genetic alterations in these three genes. Our results indicate that there is a heterogeneity in the oncogene/suppressor gene profile among diffuse large cell lymphomas. Two cell lines and one tumor carried alterations in all three genes, one cell line carried alterations of c-MYC and p53, and one primary tumor and one cell line carried p53 mutations and the t(14;18). Single alterations of BCL-2 and p53 were also observed. Another cell line had no alterations in any of these genes. The heterogeneity indicates that varied mechanisms may be involved in the generation of diffuse large cell lymphomas.

Up-regulated recombination-activating gene expression in sIg- variants of a human mature B cell line undergoing secondary Ig lambda rearrangements in cell culture

To study the role of surface immunoglobulin (sIg) expression in the control of rearrangement activity at the Ig light chain loci, we established rare sIg- clones (lambda-) from a human sIg+ B cell line (mu lambda+). Upon expansion of these sIg- clones, surface immunofluorescence analysis revealed a gradual emergence of sIg+ subpopulations, differing from the original tumor cell line both in their idiotypes and C lambda isotypes. DNA analysis revealed that this sIg heterogeneity resulted from a process of ongoing Ig lambda rearrangements. That is, one of the Ig lambda rearrangements in the parental cell line was replaced by novel Ig lambda rearrangements in the sIg- clones, which in turn were replaced by yet additional Ig lambda rearrangements in the sIg+ variants. Northern analysis demonstrated that while the expression of the recombination-activating genes RAG1 and RAG2 was relatively low in the parental cell line, their expression was significantly increased in both the sIg- variants and their sIg+ progenies. We thus describe a human mature B cell line, in which differential RAG expression allows sIg heterogeneity to be generated through secondary Ig lambda gene rearrangements. Our results indicate that the induction of RAG expression may be inversely associated with sIg expression, but that sIg expression, alone, is not sufficient to down-regulate this expression.

Detection of occult lymphoma in the peripheral blood and bone marrow of patients with untreated early-stage and advanced-stage follicular lymphoma

PURPOSE

The object of this study was to compare the relative sensitivities of morphologic, immunophenotypic, gene rearrangement, cytogenetic, and polymerase chain reaction (PCR) analyses in the detection of lymphoma cells in the bone marrow and peripheral blood of patients with follicular lymphoma.

PATIENTS AND METHODS

Bone marrow and peripheral-blood samples from 28 newly diagnosed patients with follicular lymphoma referred from several different medical centers were assessed. Routine morphologic assessment was performed initially and the remainder of the sample was aliquoted for DNA extraction to be used for gene rearrangement and PCR analyses and for immunophenotypic and cytogenetic analyses where a sufficient amount of sample remained.

RESULTS

Morphologic assessment of the bone marrow was positive for lymphoma cells in 11 of 28 patients. PCR amplification of t(14;18) breakpoint DNA detected lymphoma cells in 17 of 24 patients assessed. Morphologic assessment detected lymphoma cells in three bone marrow samples that were negative by PCR. PCR analysis was the only method able to detect circulating lymphoma cells in peripheral blood at diagnosis and was positive in 15 of 24 samples. The other methods of assessment did not show lymphoma in any samples in which lymphoma was not detected by morphologic or PCR analysis. Lymphoma cells were found in the bone marrow and/or peripheral blood as frequently in early-stage patients as in advanced-stage patients.

CONCLUSION

PCR amplification of t(14;18) breakpoint DNA together with morphologic assessment had the highest yield of detecting lymphoma cells in the bone marrow and/or peripheral blood of our population of newly diagnosed patients with follicular lymphoma. The clinical significance and prognostic importance of lymphoma cells detected by PCR in the bone marrow and/or peripheral blood of newly diagnosed follicular lymphoma patients awaits long-term follow-up data of these and additional patients.