Establishment and characterization of a mantle cell lymphoma cell line

A mantle cell lymphoma (MCL) cell line (JeKo-1) was established from peripheral blood mononuclear cells of a patient with a large cell variant of MCL showing leukaemic conversion. JeKo-1 cells were Epstein-Barr virus negative and showed a B-cell phenotype with IgM⁺, IgD⁺, CD3^?, CD5⁺, CD10^?, CD19⁺, CD20⁺ and CD23^?; they overexpressed cyclin Dl, Bcl-2, c-Myc and Rb proteins. Bcl-1/J_H gene rearrangement was confirmed by polymerase chain reaction, although karyotypic analysis showed 40/41 chromosomes devoid of apparent t(11;14)(q13;q32) translocation. JeKo-1 cells were highly tumourigenic in SCID mice.     

Blastic variant of mantle cell lymphoma shows a heterogenous pattern of somatic mutations of the rearranged immunoglobulin heavy chain variable genes

Mantle cell lymphoma is a distinct clinicopathological entity associated with t(11;14) and cyclin D1 overexpression. The majority of cases show uniform morphological and phenotypic features characterized by a monotonous proliferation of small-to-medium-sized irregular B cells that express CD5 and bright surface immunoglobulin IgM and IgD. By sequence analysis of the rearranged immunoglobulin heavy chain variable genes (VH), it has been shown that these lymphoma cells carry little if no somatic mutations, as described for the fetal CD5⁺ cells or B1 cells. Besides mantle cell lymphoma with classic histological features, a morphological variant of mantle cell lymphoma with blastic features and a more aggressive clinical course has been described. To investigate whether this variant is closely related, by the cell of origin, to typical cases, we analysed the presence and the pattern of somatic mutations of the VH genes in a series of nine cases diagnosed as such. Our cases of blastic mantle cell lymphomas rearrange most frequently VH4 and VH3 family genes. In three cases there was a complete homology to published germline genes, and a near complete homology was documented in another three. In contrast, the remaining three cases showed somatic mutations in their rearranged VH genes. Mutation analysis revealed evidence for antigen selection in one of these three cases. Taken together, these data are similar to those of normal adult-type B1 cells and those described for chronic lymphocytic leukaemia (CLL) but slightly different to those reported for classic mantle cell lymphoma. It is likely that blastic mantle cell lymphoma as well as CLL originates from adult-type B1 cells. More cases will need to be studied to determine whether classic mantle cell lymphoma is different from the blastic subtype and if it arises from fetal-type B1 cells.     

Sialosylated lewis x expression in CD30-positive anaplastic large-cell lymphomas

Summary The expression of sialosylated Lewis ^x (SLEX), a ligand for endothelial leukocyte adhesion molecule 1 in malignant lymphomas, was immunohistochemically examined, using the monoclonal antibody, CSLEX1, which specifically reacts with SLEX. It was expressed in 6 out of 64 non-Hodgkin's lymphomas, which consisted of 1 nasal large-cell lymphoma and 5 of 8 (62%) Ki-1-positive anaplastic large-cell lymphomas (ALCL). One nasal lymphoma positive for SLEX co-expressed a T cell marker, cluster of differentiation (CD) 5, and natural killer (NK) cell markers such as CD56 and CD16, indicating that SLEX⁺ nasal lymphoma cells are possibly malignant counterparts of SLEX⁺ NK cells. SLEX did not react with 30 B cell lymphomas or most Hodgkin's disease lymphomas, though it did with one lymphocyte predominance type. Although SLEX⁺ ALCL exhibit T cell markers in some cases, some ALCL expressing SLEX may represent histiocytic differentiation of the neoplastic cells. The lymphoma cells of ALCL were preferentially positive for SLEX, in contrast to Hodgkin's disease cells, and thus CSLEX1 in conjunction, with CD30 and CD15 should be of use for analyzing and making differential diagnoses of routine paraffin-embedded sections of ALCL.Abbreviations SLEX sialosylated Lewis ^x - ALCL anaplastic large-cell lymphomas     

The splenic form of mantle cell lymphoma

OBJECTIVES: To describe the clinical, immunophenotypic and molecular features, as well as the clinical course of patients with unusual presentation of mantle cell lymphoma (MCL) purely located to the spleen. PATIENTS AND METHODS: We describe seven patients presented with splenomegaly and a leukemic picture without lymphadenopathy, fulfilling the diagnostic criteria of MCL. In addition to clinical and pathologic features, patients were studied with respect to surface immunophenotype, including adhesion molecule profile, immunohistochemical expression of cyclin-D1 and bcl-1 rearrangement by polymerase chain reaction. RESULTS: Four patients were male and three female. The median palpable spleen size was 15 cm. A preliminary diagnosis of MCL was made, based on blood cell morphology and immunophenotype. All patients underwent splenectomy for therapeutic purposes. Studies done in blood and splenic lymphocytes revealed the following: 7/7 patients were CD19/CD5, CD20 and CD38 positive; CD10 negative and 6/7 CD23 negative. The adhesion molecule expression pattern was consistent in all patients: L-Selectin and CD11c were negative, CD11alpha and CD18 weakly positive and CD54 strongly positive. The median spleen weight was 1775 g. Histology disclosed a cytologic and architectural pattern consistent with MCL. Cyclin-D1 was positive in 6/6 studied patients. Bcl-1 rearrangement was found in 5/7 patients. Splenectomy was applied as the sole treatment and was beneficial in all patients, with median blood values as following: prior to splenectomy, Ht 29.5%, platelets 110 x 10(9)/l, lymphoma cells 5.0 x 10(9)/L, and at 6 months post-splenectomy, Ht 43%, platelets 311 x 10(9)/l and lymphoma cells 3.0 x 10(9)/L. Of the seven patients, two developed progressive disease 11 and 26 months post-splenectomy. The remaining five are in improving clinical and hematological condition without chemotherapy at a median follow up of 20 months. CONCLUSIONS: We conclude that this presentation represents a separate form of MCL which requires splenectomy. It remains to be seen whether it carries a better prognosis than classical MCL.     

The Bruton tyrosine kinase (BTK) inhibitor PCI‐32765 synergistically increases proteasome inhibitor activity in diffuse large‐B cell lymphoma (DLBCL) and mantle cell lymphoma (MCL) cells sensitive or resistant to bortezomib

Interactions between the Bruton tyrosine kinase (BTK) inhibitor PCI‐32765 and the proteasome inhibitor (bortezomib) were examined in diffuse large‐B cell lymphoma (DLBCL) and mantle cell lymphoma (MCL) cells, including those highly resistant to bortezomib. Co‐administration of PCI‐32765/bortezomib synergistically increased mitochondrial injury and apoptosis in germinal centre‐ or activated B‐cell‐like‐DLBCL cells and in MCL cells. These events were accompanied by marked AKT and nuclear factor (NF)‐κB (NFKB1) inactivation, down‐regulation of Mcl‐1 (MCL1), Bcl‐xL (BCL2L1), and XIAP, and enhanced DNA damage (e.g., γH2A.X formation) and endoplasmic reticulum (ER) stress. Similar interactions were observed in highly bortezomib‐resistant DLBCL and MCL cells, and in primary DLBCL cells. In contrast, PCI‐32765/bortezomib regimens displayed minimal toxicity toward normal CD34⁺ bone marrow cells. Transfection of DLBCL cells with a constitutively active AKT construct attenuated AKT inactivation and significantly diminished cell death, whereas expression of an NF‐κB “super‐repressor” (IκBα_ser34/36) increased both PCI‐32765 and bortezomib lethality. Moreover, cells in which the ER stress response was disabled by a dominant‐negative eIF2α construct were resistant to this regimen. Finally, combined exposure to PCI‐32765 and bortezomib resulted in more pronounced and sustained reactive oxygen species (ROS) generation, and ROS scavengers significantly diminished lethality. Given promising early clinical results for PCI‐32765 in DLBCL and MCL, a strategy combining BTK/proteasome inhibitor warrants attention in these malignancies.     

Phase 1–2 study of vorinostat (SAHA), cladribine and rituximab (SCR) in relapsed B-cell non-Hodgkin lymphoma and previously untreated mantle cell lymphoma

Altered DNA methylation and histone acetylation in lymphoma provided the rationale for using vorinostat (SAHA), cladribine and rituximab (SCR) in non-Hodgkin lymphomas (NHL) in this phase 1–2 study (NCT00764517). Treatment included cladribine 5 mg/m² intravenously (IV) (days 1–5), rituximab 375 mg/m² IV (weekly 4× for cycle 1 and 1×/month) and vorinostat orally once daily (days 1–14) every 28 days for up to six cycles. Phase 1 included relapsed patients (n = 10) in a standard 3 + 3 dose escalation design (vorinostat: 200, 300 and 400 mg). No dose-limiting toxicities were seen. The phase 2 dose for vorinostat was 400 mg po (days 1–14). The majority of phase 2 patients had mantle cell lymphoma (MCL) (n = 57; 39 previously untreated, 10 relapsed). The primary objective was objective response rate [complete response (CR) + partial response] which was 39% (7/18) in relapsed patients and 97% (38/39) with 80% (31/39) attaining a CR in previously untreated MCL. At a median follow-up of 42 months, median progression-free survival (PFS) and overall survival (OS) for relapsed NHL were 19·5 [95% confidence interval (CI): 2·0–33·0] and 25·0 (95% CI: 12·0–45·0) months respectively. Median PFS for previously untreated MCL was 84·0 months; OS could not be estimated. Toxicities were primarily haematological.     

Immune evasion of mantle cell lymphoma: expression of B7-H1 leads to inhibited T-cell response to and killing of tumor cells

Clinical trials of immunotherapy in mantle cell lymphoma have not yet delivered desirable results, partly because of the inhibitory machinery of the tumor and its microenvironment. Here we investigated the role of B7-H1, a member of the B7 family of co-stimulatory/co-inhibitory ligands, in mantle cell lymphoma-mediated immunosuppression. Allogeneic CD3⁺, CD4⁺ and CD8⁺ T cells were purified and co-cultured with irradiated mantle cell lymphoma cells. Mantle cell lymphoma-reactive T-cell lines from HLA-A*0201⁺ healthy blood donors were generated after in vitro restimulation, and were subjected to functional tests. We found that B7-H1 expressed on mantle cell lymphoma cells was able to inhibit T-cell proliferation induced by the tumor cells, impair the generation of antigen-specific T-cell responses, and render mantle cell lymphoma cells resistant to T-cell-mediated cytolysis. Blocking or knocking down B7-H1 on mantle cell lymphoma cells enhanced T-cell responses and restored tumor-cell sensitivity to T-cell-mediated killing in vitro and in vivo. Knocking down B7-H1 on mantle cell lymphoma cells primed more CD4⁺ or CD8⁺ memory effector T cells. Our study demonstrates for the first time that lymphoma cell-expressed B7-H1 may lead to the suppression of host anti-tumor immune responses in mantle cell lymphoma and targeting tumor cell B7-H1 may represent a novel approach to improve the efficacy of immunotherapy in patients with mantle cell lymphoma.     

Primary subcutaneous mantle cell lymphoma treated successfully with THP-COP therapy

A 73-year-old man noticed a subcutaneous tumor on the left upper palpebra from April 1998, but did not seek therapy for it. Facial subcutaneous tumors appeared from November 1999, and multiple tumors appeared on the skin of the chest and both upper arms from January 2000. Tumor biopsy revealed that these tumors were non-Hodgkin lymphoma showing CD19 (+), CD20 (+), CD5 (+), CD10 (-), smIgM (+), sm lambda (+) and cyclin D1 (+). The karyotype was t(11;14) (q13;q32), but bcl-1 gene rearrangement was not detected. On the basis of these data, primary mantle cell lymphoma (MCL) of the subcutis was diagnosed. The patient underwent eight courses of THP-COP therapy, and complete remission was achieved. Primary subcutaneous B-cell lymphoma, especially MCL, is rare. MCL is aggressive and difficult to cure; the median survival of patients is 3 to 5 years, and the 5-year survival is 30%. However, the present patient showed a good response to chemotherapy, and complete remission has continued for 17 months since the MCL was first diagnosed.     

De novo CD5-positive diffuse large B-cell lymphoma: clinical characteristics and therapeutic outcome

To determine the clinical significance of CD5 expression in diffuse large B-cell lymphoma (DLBL) without a clinical history of low-grade B-cell lymphoma, we have reviewed the clinical features and therapeutic outcome of 25 patients with de novo CD5-positive DLBL, and compared the results with those of 87 patients with CD5-negative DLBL and 22 patients with mantle cell lymphoma (MCL). The patients with de novo CD5-positive DLBL had clinical characteristics of elderly onset (median age 63, range 37-91), and female predominance (male/female 10/15). 21 (84%) of these patients had extranodal involvement at presentation, with great variation in the sites. In comparison with the patients with CD5-negative DLBL, the treatment outcome for the patients with de novo CD5-positive DLBL was very poor with frequent relapse. The failure-free survival curve was almost identical to that of patients with MCL, showing that standard chemotherapy for DLBL was not effective for most of the patients with de novo CD5-positive DLBL. These findings suggest that de novo CD5-positive DLBL forms a distinct subgroup of DLBL.     

Four‐year follow‐up of a single arm,phase II clinical trial of ibrutinib with rituximab (IR) in patients with relapsed/refractory mantle cell lymphoma (MCL)

Ibrutinib has shown significant activity in patients with relapsed or refractory mantle cell lymphoma (RR‐MCL). We report the long‐term outcome and safety profile of a single‐centre, single arm, open‐label, phase 2 study of RR‐MCL treated with IR. Overall, the median follow‐up time was 47 months (range 1–52 months), median duration on treatment was 16 months (range 1–53 months) and median number of treatment cycles was 17 (range 1–56). Twenty‐nine patients (58%) achieved complete remission and of these, 12 patients continue on study. Thirty‐eight patients discontinued treatment, 14 due to disease progression (2 transformed). Patients with blastoid morphology, high risk MCL International Prognostic Index score and high Ki67% had inferior survival. The commonest grade 1–2 toxicities were fatigue, diarrhoea, nausea, arthralgias and myalgias. None had long term toxicities. Median progression‐free survival was 43 months. Eighteen patients (36%) died (14 deaths were MCL‐related). The median overall survival has not been reached. Treatment with IR can provide durable remissions in a subset of patients with RR‐MCL, especially those with low Ki67%. The possible benefit of adding other therapies in combination with IR in RR‐MCL is under exploration.     

Indolent mantle cell leukemia: a clinicopathological variant characterized by isolated lymphocytosis, interstitial bone marrow involvement, kappa light chain restriction, and good prognosis

Background

Cases of mantle cell lymphoma with indolent behavior have been reported, but are poorly identified by current clinical risk models. Early studies found peripheral blood involvement to be an adverse prognostic factor; however, cases of a seemingly indolent variant of mantle cell lymphoma, characterized by peripheral blood involvement and minimal nodal disease, have been incompletely described, particularly with regard to bone marrow findings. We report a series of leukemic phase mantle cell lymphomas with a non-progressive or slowly progressive course.

Design and Methods

Cases presenting with mantle cell lymphoma limited to the peripheral blood/bone marrow from 2000–2010 were identified. Diagnoses were established by morphology, flow cytometric analysis and requisite evidence of IGH-CCND1@ by fluorescence in-situ hybridization or t(11;14)(q13;q32) by cytogenetics. Patients with lymphadenopathy, splenomegaly and gastrointestinal symptomatology were excluded.

Results

Patients (n=8, median age 60.5 years) were asymptomatic with mild lymphocytosis (8.7×10⁹/L; range, 4.5–14.2×10⁹/L) and cytology typical of mantle cell lymphoma. Flow cytometric analysis showed that all expressed CD5, CD19, CD20, variable CD23, and a striking kappa immunoglobulin light chain restriction (7/8 cases). Bone marrow biopsy at diagnosis showed interstitial single or small lymphoid aggregates with similar patterns of CD20 and cyclin D1 immunostaining which were not readily discernable by hematoxylin and eosin stain. SOX11 was negative (4/5) or only weakly expressed (1/5). The median follow-up was 27 months (range, 5–109 months) and all patients, but one, are alive with no clinical evidence of disease. The prevalence of indolent mantle cell lymphoma presenting only with lymphocytosis, among all mantle cell lymphomas diagnosed during the same period, was 3%.

Conclusions

Leukemic mantle cell lymphoma limited to blood and bone marrow is an indolent variant characterized by mild-moderate lymphocytosis, interstitial low-level bone marrow involvement, simple karyotype, kappa light chain expression, cyclin D1 expression with lack of SOX11, and slow or absent clinical progression. Some cases may represent a mantle cell lymphoma counterpart to chronic lymphocytic leukemia – phenotype monoclonal B-cell lymphocytosis. Recognition of this variant could inform treatment decisions and possibly avoid unnecessary treatment.     

PRAD1 gene over-expression in mantle-cell lymphoma but not in other low-grade B-cell lymphomas, including extranodal lymphoma

Summary. Employing Northern blot analysis and the polymerase chain reaction, we investigated PRAD1 gene over-expression in the tumour tissues of 58 patients with B-cell lymphoma. These findings were then examined in relation to the patients' clinical and immunohistological characteristics. The over-expression of this gene was detected in 6/8 patients with mantle cell lymphoma (MCL) and in only 1/50 other lymphomas, indicating its close association with MCL. The patients with MCL had common clinical findings of advanced disease with generalized lymphadenopathy on admission, and they had a CD5+CD10–IgD+ phenotype. The patients with chronic lymphocytic leukaemia (CLL) also showed findings indicating a distinctive disease entity: a CD5+CD10–IgD+ phenotype and lack of PRAD1 over-expression. In contrast, most patients with diffuse low-grade lymphoma other than MCL and CLL had localized extranodal disease, expressed a CD5-CD10–IgD– phenotype, and lacked PRAD1 over-expression. These findings suggest that extranodal low-grade lymphomas differ from nodal MCL and are not part of the spectrum of CLL.     

Somatic hypermutation and V(H) gene usage in mantle cell lymphoma

Abstract: Mantle cell lymphoma (MCL) is considered to derive from naïve, pregerminal center (GC) CD5⁺ B‐cells. However, the cell of origin has been questioned in recent studies that showed somatic hypermutations in the immunoglobulin (Ig) variable heavy chain (V_H) genes in subsets of MCL. To clarify this issue, we analyzed the IgV_H genes for the presence of somatic hypermutations in 51 MCL cases. Twenty percent of the MCL cases displayed somatically mutated V_H genes (defined as >2% mutated), whereas 80% showed unmutated V_H genes. This finding suggests that MCL is a genetically heterogeneous disease, with the majority of cases originating from unmutated pre‐GC B‐cells and a subset deriving from more mature B‐cells which have been exposed to the GC environment and have undergone somatic hypermutation. A biased V_H gene usage has been demonstrated in several B‐cell malignancies; however, this has not yet been investigated in MCL, although V_H4‐34 overusage has been indicated by small studies. Interestingly, we found a restricted usage of three individual V_H genes in our MCL material; V_H4‐34 (22%), V_H3‐21 (16%) and V_H5‐51 (12%). This novel finding of preferential V_H gene usage in half of the MCL cases may suggest an antigen driven process occurring in B‐cells expressing specific V_H genes, thus implicating that Ig specificity could be involved in mantle cell lymphoma development.     

Bcl-2 family of proteins in indolent B-cell non-Hodgkin's lymphoma: study of 116 cases

The bcl-2 family of proteins comprises both antagonists and agonists of apoptosis. We have investigated whether subsets of indolent B-cell non-Hodgkin's lymphoma (IB-NHL) differ in the expression of the bcl-2 family members; 116 cases of IB-NHL, composed of chronic lymphocytic leukemia (CLL, n = 48), follicular lymphoma (FL, n = 38), marginal zone B-cell lymphoma (MZBCL, n = 15), and mantle cell lymphoma (MCL, n = 15), were investigated for expression of bcl-2, bcl-X, mcl-1, bax, and bak proteins by immunohistochemistry. Expression of bcl-2 and bcl-X proteins was moderate/high among most IB-NHLs. Expression of mcl-1 was low/absent in most cases of CLL and MCL and low/moderate in most cases of FL and MZBCL. Most MCLs did not express bax protein. Bax expression was absent/low among most cases of CLL and low/moderate among most cases of FL and MZBCL. Expression of bak was moderate/low among most cases of CLL, MZBCL, and MCL but was absent/low among most cases of FL. The different subsets of IB-NHLs differ in their expression of mcl-1, bax, and bak proteins.     

p53 overexpression as a marker of poor prognosis in mantle cell lymphomas with t(11;14)(q13;q32)

The t(11;14)(q13;q32) translocation, which juxtaposes the BCL1 oncogene with the Ig heavy chain locus, has been associated with an uncommon subtype of non-Hodgkin's lymphoma (NHL) termed mantle cell lymphoma (MCL). To date, no molecular marker that serves as an indicator of tumor progression or clinical prognosis has been described for NHLs with this translocation. We examined a panel of NHLs with t(11;14) for overexpression of p53 and correlated the results with single-strand conformation polymorphism (SSCP) analysis, karyotypic features, and clinical course. NHLs with t(11;14) were identified from 30 patients. The diagnosis was MCL for 23 of 30, small lymphocytic lymphoma for 4 of 30, and diffuse large-cell lymphoma for 3 of 30 cases. The results of immunohistochemistry analysis using a monoclonal anti-p53 antibody on paraffin-embedded specimens were compared with the SSCP data, the tumor karyotypes, and clinical course of each patient. DNA sequencing of exons was performed on cases that showed conformational changes by SSCP analysis. NHLs from 5 of 23 patients with MCL were positive for p53 overexpression. Deletions of chromosome 17p were identified in 2 of 30 cases, both of which were MCLs showing p53 overexpression. Two of the five MCLs with p53 overexpression showed evidence for TP53 mutations. None of the 18 MCLs negative for p53 overexpression showed conformational changes by SSCP. For these 18 patients with MCLs that did not overexpress p53, the median survival was 63 months, compared with 12 months for the 5 patients with MCLs positive for p53 overexpression (P < .001). These results suggest that p53 overexpression in MCL with t(11;14)(q13;q32) may serve as a marker of poor prognosis.     

Prognostic impact of monocyte count at presentation in mantle cell lymphoma

An increased number of circulating monocytes at presentation has recently been associated with shorter survival in Hodgkin lymphoma, follicular lymphoma and diffuse large B cell lymphoma. This study aimed to assess the prognostic impact of the absolute monocyte count (AMC) at diagnosis in mantle cell lymphoma (MCL). AMC at diagnosis was available in 97 MCL cases recorded in the databases of the Oncology Institute of Southern Switzerland in Bellinzona (Switzerland) and the Division of Haematology of the Amedeo Avogadro University of Eastern Piedmont in Novara (Italy). With a median follow up of 7 years, the 5‐year overall survival was 29% for patients with AMC >0·50 × 10⁹/l and 62% for patients with AMC ≤0·50 × 10⁹/l (P = 0·008). Elevated AMC and beta‐2 microglobulin at diagnosis remained independent outcome predictors at multivariate analysis, controlling for the MCL International Prognostic Index (MIPI), and have been used to build a simple prognostic scoring system. In this relatively small and heterogeneous series an increased AMC identified poor‐risk patients. Our results suggest that AMC together with the beta‐2 microglobulin level might provide an inexpensive way to stratify MCL patient risk as a complement to the MIPI, which was confirmed to be a very powerful prognostic tool.     

Stem cell mobilization in resistant or relapsed lymphoma: superior yield of progenitor cells following a salvage regimen comprising ifosphamide, etoposide and epirubicin compared to intermediate-dose cyclophosphamide

We analysed the factors influencing the efficacy of peripheral blood stem cell (PBSC) collection in patients with lymphoma. Sixty-six patients underwent initial PBSC collection following mobilization with chemotherapy plus recombinant granulocyte colony-stimulating factor (300 μg/d). Patients were mobilized with one of two chemotherapy regimens, either cyclophophamide (3 g/m² or 4 g/m²) (n=50) or ifosphamide, etoposide and epirubicin (IVE; n=16). The target of collecting >2.0×10⁶ CD34⁺ cells/kg was achieved in 43/66 (65%) patients with a median of two apheresis procedures. The IVE plus G-CSF mobilization regimen gave a significantly higher median yield of CD34⁺ cells (8.62 × 10⁶/kg) compared with cyclophosphamide plus G-CSF (3.59 × 10⁶/kg) (P=0.045). The median yield of CD34⁺ cells per leukapheresis was almost twice as high in patients receiving IVE (1.94 × 10⁶/kg) compared to cyclophosphamide (1.03 ×10⁶/kg) (P= 0.035). In a univariate analysis of the factors affecting mobilization, the subtype of lymphoma (high-grade NHL) and the mobilization regimen were the only factors associated with high CD34⁺ cell yield. However, in a multivariate analysis of factors affecting mobilization including age, lymphoma subtype, previous chemotherapy and radiotherapy, only the use of the IVE protocol was predictive of a high yield of CD34⁺ cells. In 13 patients undergoing a second mobilization procedure the use of IVE was associated with a significantly higher yield of CD34⁺ cells compared to cyclophosphamide; three patients who failed cyclophosphamide plus G-CSF mobilization were able to proceed to transplantation following success-ful mobilization with IVE + G-CSF. These results demon-strate that IVE is a highly effective mobilization regimen which is superior to cyclophophamide and has the benefit of being effective salvage therapy for lymphoma patients.     

Synergistic antitumor effects of lenalidomide and rituximab on mantle cell lymphoma in vitro and in vivo

Rituximab (RTX), a chimeric anti‐CD20 antibody, is associated with direct induction of apoptosis and antibody‐dependent cell‐mediated cytotoxicity (ADCC) with clinical efficacy in mantle cell lymphoma (MCL). Lenalidomide (LEN), a novel immunomodulatory agent, sensitizes tumor cells and enhances ADCC. Our study attempted to elucidate the mechanism of LEN‐enhanced RTX‐mediated cytotoxicity of MCL cells. We found that LEN and RTX induced growth inhibition of both cultured and fresh primary MCL cells. LEN enhanced RTX‐induced apoptosis via upregulating phosphorylation of c‐Jun N‐terminal protein kinases (JNK), Bcl‐2, Bad; increasing release of cytochrome‐c; enhancing activation of caspase‐3, ‐8, ‐9 and cleavage of PARP. Meanwhile, LEN activated NK cells and increased CD16 expression on CD56^lowCD16⁺ NK cells. Whole PBMCs but not NK cell‐depleted PBMCs treated with LEN augmented 30% of RTX‐dependent cytotoxicity. Daily treatment with LEN increased NK cells by 10‐folds in SCID mice, and combination of LEN and RTX decreased tumor burden and prolonged survival of MCL‐bearing SCID mice. Taken together, our study demonstrates that LEN plus RTX provides a synergistically therapeutic effect on MCL cells by enhancing apoptosis and RTX‐dependent NK cell‐mediated cytotoxicity and may be an optimal combination in the clinical trial of relapsed or refractory MCL. Am. J. Hematol. 2009. © 2009 Wiley‐Liss, Inc.