Establishment of a novel MALT lymphoma cell line, ma-1, from a patient with t(14;18)(q32;q21)-positive Helicobacter pylori-independent gastric MALT lymphoma

Although t(11;18)(q21;q21), t(1;14)(p22;q32), and a few other genetic mutations are specific markers for the Helicobacter pylori (HP)-independent status of gastric mucosa-associated lymphoid tissue (MALT) lymphoma, the molecular mechanisms responsible for HP-independence of gastric MALT lymphoma without such translocations and mutations remain uncharacterized. In the present study, we describe the establishment and characterization of a novel MALT lymphoma cell line, MA-1, which was derived from a gastric MALT lymphoma which was negative for both t(11;18)(q21;q21) and t(1;14)(p22;q32); the patient had failed HP eradication therapy and chemotherapy. The cell morphology and the immunophenotype of this cell line were similar to that of the original gastric MALT lymphoma. Comparative genomic hybridization analysis showed no significant gene copy number changes. Spectral karyotyping displayed a near-diploid chromosome content (48 < 2n>XY), with at least 13 chromosome structural abnormalities. Furthermore, fluorescence in situ hybridization analyses disclosed the existence of three sub-clones, characterized by t(14;18)(q32;q21)/IGH-BCL2, t(14;18)(q32;q21)/IGH-MALT1, and the presence of both chromosomal translocations in the same cell, respectively; whereas amplification of the genes CRAD9, TRAF2, and BCL10 were not found. In conclusion, we have established the first human gastric MALT lymphoma cell line, which is characterized by unusual and complex chromosome translocations and will be useful to explore further the molecular mechanisms of HP-independence in gastric MALT lymphoma.     

MALT lymphoma: many roads lead to nuclear factor-κb activation

Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) lymphoma is characterized genetically by several recurrent, but mutually exclusive, chromosome translocations. To date, it has been shown that at least the oncogenic products of t(1;14)(p22;q32)/BCL10-IGH, t(14;18)(q32;21)/IGH-MALT1 and t(11;18)(q21;q21)/API2-MALT1 activate the nuclear factor (NF)-κB activation pathway. Recently, A20, an essential global NF-κB inhibitor, was found to be inactivated by somatic deletion and/or mutation in translocation-negative MALT lymphomas. However, these genetic abnormalities alone are not sufficient for malignant transformation and thus need to cooperate with other factors in MALT lymphomagenesis. Recent studies have shown steady, exciting progresses in our understanding of the biological functions of BCL10, MALT1 and A20 in the regulation of the NF-κB activation pathways and the biology of lymphocytes. This review discusses the implication of these recent advances in the molecular pathogenesis of MALT lymphoma, and explores how the above genetic abnormalities cooperate with immunological stimulation in the development of lymphoma.     

MALT lymphoma with t(14;18)(q32;q21)/IGH-MALT1 is characterized by strong cytoplasmic MALT1 and BCL10 expression

Mucosa-associated lymphoid tissue (MALT) lymphoma is specifically associated with t(11;18)(q21;q21), t(1;14)(p22;q32) and t(14;18)(q32;q21). t(11;18)(q21;q21) fuses the N-terminus of the API2 gene to the C-terminus of the MALT1 gene and generates a functional API2-MALT1 product. t(1;14)(p22;q32) and t(14;18)(q32;q21) bring the BCL10 and MALT1 genes respectively to the IGH locus and deregulate their expression. The oncogenic activity of the three chromosomal translocations is linked by the physiological role of BCL10 and MALT1 in antigen receptor-mediated NFkappaB activation. In this study, MALT1 and BCL10 expression was examined in normal lymphoid tissues and 423 cases of MALT lymphoma from eight sites, and their expression was correlated with the above translocations, which were detected by molecular and molecular cytogenetic methods. In normal B-cell follicles, both MALT1 and BCL10 were expressed predominantly in the cytoplasm, high in centroblasts, moderate in centrocytes and weak/negative in mantle zone B-cells. In MALT lymphoma, MALT1 and BCL10 expression varied among cases with different chromosomal translocations. In 9/9 MALT lymphomas with t(14;18)(q32;q21), tumour cells showed strong homogeneous cytoplasmic expression of both MALT1 and BCL10. In 12/12 cases with evidence of t(1;14)(p22;q32) or variants, tumour cells expressed MALT1 weakly in the cytoplasm but BCL10 strongly in the nuclei. In all 67 MALT lymphomas with t(11;18)(q21;q21), tumour cells expressed weak cytoplasmic MALT1 and moderate nuclear BCL10. In MALT lymphomas without the above translocations, both MALT1 and BCL10, in general, were expressed weakly in the cytoplasm. Real-time quantitative RT-PCR showed a good correlation between MALT1 and BCL10 mRNA expression and underlining genetic changes, with t(14;18)(q32;q21)- and t(1;14)(p22;q32)-positive cases displaying the highest MALT1 and BCL10 mRNA expression respectively. These results show that MALT1 expression pattern is identical to that of BCL10 in normal lymphoid tissues but varies in MALT lymphomas, with high cytoplasmic expression of both MALT1 and BCL10 characterizing those with t(14;18)(q32;q21).     

Chromosome 18 breakpoint in t(11;18)(q21;q21) translocation associated with MALT lymphoma is proximal to BCL2 and distal to DCC

The t(11;18)(q21;q21) translocation has recently been identified as a recurring chromosomal abnormality in a subset of extranodal marginal zone B‐cell lymphoma, a low‐grade lymphoma of mucosa‐associated lymphoid tissue (MALT). Neither the 11q21 nor the 18q21 breakpoints have been characterized by molecular genetic analysis. As a prelude to isolation of the gene(s) involved in this translocation, we have mapped the 18q21 breakpoint region by fluorescence in situ hybridization (FISH) of YAC and PAC clones. We mapped 37 YACs assigned to a 29‐cM region within the chromosomal band 18q21. Using nine of these YACs in single‐ and/or dual‐color FISH to analyze three cases of MALT lymphomas with the t(11;18)(q21;q21) translocation, we localized the breakpoints within a 1.6‐Mb nonchimeric YAC (938E1). This YAC is useful for the detection of the translocation in metaphase and in interphase cells. A nonchimeric YAC contig of an 8‐cM region around the breakpoint comprising nine YACs and a PAC contig of YAC 938E1 were constructed, which enabled the refinement of the breakpoint region in the proximal region of the YAC within a <820‐kb segment. This breakpoint is proximal to the BCL2 locus and distal to DCC and DPC4 loci in chromosomal band 18q21. Genes Chromosomes Cancer 24:156–159, 1999. © 1999 Wiley‐Liss, Inc.     

MALT1, BCL10 and FOXP1 in salivary gland mucosa-associated lymphoid tissue lymphomas

In view of the certain anatomic site-dependent frequency of chromosomal translocations involved in extranodal marginal zone B cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) pathogenesis, 17 salivary gland MALT lymphoma cases were analyzed for MALT1 and FOXP1 translocations. B cell CLL/lymphoma 10 (BCL10) and forkhead box PA (FOXP1) protein expression were studied by immunohistochemistry and translocations identified using fluorescence in situ hybridization (FISH)-specific probes FOXP1, t(11;18)(q21;q21)/API2-MALT1 and t(14;18)(q32;q21)/IgH-MALT1. None of the 11 analyzed cases showed FOXP1 rearrangement or amplification. The t(11;18) was present in five of 13 cases and the t(14;18) in three of 13 cases. MALT1 translocations were mostly mutually exclusive except in a single case. FOXP1 protein expression showed differences in the proportion of tumor cells with nuclear expression but not in their intensity, with the exception of one case where very intense nuclear staining was noted. BCL10 nuclear expression was present in four of 17 cases, two of which lacked t(11;18). Our results suggest that MALT1-specific translocations and FOXP1 rearrangements are not commonly involved in pathogenesis. A case with strong FOXP1 protein expression indicates the possibility that the upregulation of FOXP1 expression is significant in a small subset of salivary gland MALT lymphomas. Also a single case in which both MALT1 translocations were present indicates that these are not always mutually exclusive.     

Unfavourable prognosis of patients with trisomy 18q21 detected by fluorescence in situ hybridisation in t(11;18) negative, surgically resected, gastrointestinal B cell lymphomas

BACKGROUND: The most frequent cytogenetic alteration in gastrointestinal (GI) B cell lymphoma (BCL) is t(11;18)(q21;q21). GI B cell non-Hodgkin lymphomas lacking this translocation vary in their biology and clinical outcome. The t(11;18) negative subgroup shows increased numerical changes of chromosome 18, although its clinical relevance remains unknown. METHODS: Thirty surgically resected primary GI BCLs were examined-11 low grade marginal zone mucosa associated lymphoid tissue (MALT) lymphomas, four marginal zone lymphomas with diffuse large BCL (DLBCL), and 15 de novo DLBCLs. Chromosome 18 aberrations were examined using interphase fluorescence in situ hybridisation. Trisomy 18 was studied applying a centromere 18 probe and a dual colour probe for the MALT1 gene at 18q21. RESULTS: Using the MALT1 probe, only one marginal zone MALT lymphoma had a break apart pattern, indicating t(11;18) or variants. In the GI BCLs lacking MALT1 breaks, trisomy 18q21 was seen in seven patients (four with complete trisomy 18 and three with partial trisomy of 18q21). Trisomy 18q21 was found in two of 10 low grade MALT lymphomas and five of 19 GI BCLs with large cell component. Six of 17 patients with trisomy 18q21 presented with >/= stage II and one of 12 with stage I disease. Trisomy 18q21 was associated with significantly shorter disease specific survival in the whole group and GI BCLs with large cell component, but not in the low grade group. CONCLUSIONS: Trisomy 18q21, including MALT1, may be associated with advanced tumour stage and may be a predictor of poor outcome in surgically resected primary GI BCLs.     

T(14;18)(q32;q21) involving MALT1 and IGH genes in an extranodal diffuse large B-cell lymphoma

Two translocations involving the MALT1 gene have been described in extranodal marginal zone B-cell lymphomas of MALT type. A t(11;18)(q21;q21) involving API2 and MALT1 occurs in a subset of MALT lymphomas but with only rare exception is absent in diffuse large B-cell lymphomas (DLBCL), even at MALT sites. More recently, a t(14;18)(q32;q21) involving IGH and MALT1 has been described in nongastric extranodal MALT lymphomas. This translocation is indistinguishable from the IGH-BCL2 translocation by using classical cytogenetics. We report the IGH-MALT1 translocation in a cutaneous DLBCL as shown by classical cytogenetics and molecular cytogenetic analysis. This is the first report of an IGH-MALT1 translocation in DLBCL. These findings indicate that MALT1 translocations are not restricted to indolent-appearing lymphomas, provide further evidence that API2-MALT1 and IGH-MALT1 translocations exhibit biologic differences, have implications regarding the pathogenesis of some extranodal DLBCL, and emphasize that a t(14;18)(q32;q21) cannot be assumed to reflect a BCL2 translocation.     

t(11;18)(q21;q21.1): A recurring translocation in lymphomas of mucosa-associated lymphoid tissue (malt)?

A distinct subtype of extranodal malignant lymphoma derived from mucosa-associated lymphoid tissues (MALT) has recently been defined. We have detected an acquired t(11;18)(q21;q21.1) in a patient with a MALT lymphoma of the stomach. This translocation has previously been described in two other patients with extranodal lymphoma. The BCL2 oncogene, which is located at band 18q21.3 and is activated by the t(14;18)(q32;q21) in follicular lymphoma, was not rearranged in this case. This newly identified t(11;18) may be a recurring translocation specifically associated with MALT lymphomas. Genes located at the breakpoint sites of chromosome 11 and/or chromosome 18 may be crucial to the pathogenesis of this type of malignant lymphoma.     

Chromosomal imbalances are associated with outcome of Helicobacter pylori eradication in t(11;18)(q21;q21) negative gastric mucosa-associated lymphoid tissue lymphomas

Approximately 70% of gastric mucosa-associated lymphoid tissue (MALT) lymphomas can be successfully treated with H. pylori eradication. The translocation t(11;18)(q21;q21) characteristic of MALT lymphoma is recognized as a marker for H. pylori independency, but this marker is found in only a half of the MALT lymphomas resistant to H. pylori eradication. Detailed analyses of the genomic features of eradication resistant as well as responsive groups are important for understanding their molecular basis. We performed array-based comparative genomic hybridization (array-CGH) for 29 gastric MALT lymphomas treated with H. pylori eradication. These comprised ten cases of t(11;18) positive MALT, nine cases of t(11;18) negative MALT with H. pylori dependency, and ten cases of t(11;18) negative MALT with H. pylori independency. Array-CGH analysis demonstrated that no significant genetic alterations were found in t(11;18) positive MALT lymphomas, but numerous genomic alterations were detected in t(11;18) negative MALT lymphomas. Many of these alterations were similar to those found in diffuse large B-cell lymphoma with trisomy 3 being the most recurrent alteration. Within the t(11;18) negative MALT lymphoma without large cell components group, genomic imbalances occurred more frequently in the H. pylori independent than in the H. pylori dependent group (P = 0.02). Genomic imbalances are associated with H. pylori independency in t(11;18) negative gastric MALT lymphomas. They may thus play an important role in the development of H. pylori independency.     

A novel t(2;6)(p12;q23) appearing during transformation of follicular lymphoma with t(18;22)(q21;q11) to diffuse large cell lymphoma

Follicular lymphoma is characterized genetically by t(14;18)(q32;q21), whereas t(18;22)(q21;q11), a rare variant form of t(14;18), has been preferentially observed in chronic lymphocytic leukemia (CLL). We describe here an unusual case of follicular lymphoma with a t(18;22)(q21;q11), that progressed to diffuse large cell lymphoma with a novel t(2;6)(p12;q23). Spectral karyotyping revealed that add(2)(p12) and add(6)(q23) were derived from a t(2;6)(p12;q23). Fluorescence in situ hybridization analysis confirmed rearrangements of the BCL2 gene at 18q21 and the BCL6 gene at 3q27. Our results indicate that a reciprocal translocation involving 6q23 could be implicated in the progression of follicular lymphoma and that t(18;22) may have a specific role in the pathogenesis of follicular lymphoma as well as CLL.     

t(11;14)(q23;q32) involving IGH and DDX6 in nodal marginal zone lymphoma

Nodal marginal zone lymphoma (NMZL) is a primary nodal B‐cell lymphoma that shares morphological and immunophenotypic characteristics with extranodal and splenic marginal zone lymphoma. Data on altered genes and signaling pathways are scarce in this rare tumor entity. To gain further insights into the genetic background of NMZL, seven cases were investigated by microarray analysis, G‐banding, and FISH. Chromosomal imbalances were observed in 3/7 cases (43%) with gains of chromosome arms 1q, 8q, and 12q being the most frequent findings. Furthermore, we identified a translocation t(11;14)(q23;q32) involving IGH and DDX6. Chromosomal walking, expression analysis, siRNA‐mediated gene knockdown and a yeast two hybrid screen were performed for further characterization of the translocation in vitro. In siRNA experiments, DDX6 appeared not to be involved in NF‐κB activation as frequently observed for genes promoting lymphomagenesis but was found to interfere with the expression of BCL6 and BCL2 in an NF‐κB independent manner. In conclusion, we identified several unbalanced aberrations and a t(11;14) involving IGH and DDX6 providing evidence for a contribution of DDX6 to lymphomagenesis by deregulation of BCL6 in NMZL. © 2012 Wiley Periodicals, Inc.     

MALT1 and BCL10 aberrations in MALT lymphomas and their effect on the expression of BCL10 in the tumour cells.

Among the genetic abnormalities reported to occur in mucosa-associated lymphoid tissue (MALT) lymphomas, the three translocations t(11;18)(q21;q21), t(1;14)(p22;q32) and t(14;18)(q32;q21) are of particular interest because they appear to be specific for, or at least closely related to this type of B-cell non-Hodgkin's lymphoma. These translocations affect the MALT1 (18q21) and BCL10 (1p22) genes. We retrieved 77 consecutive biopsies of MALT lymphomas (documented with frozen material) over a 10-year period and investigated these cases for the presence of these three translocations with fluorescence in situ hybridisation, along with the immunohistochemical analysis of the intracellular localisation of the BCL10 protein. The above-listed translocations occurred mutually exclusive and were detected in 10, 1 and 3% of the cases, respectively (the latter incidence being much lower than in the previously reported studies by one single group). These genetic rearrangements corresponded well with the aberrant subcellular localisation of the BCL10 protein as found by immunohistochemistry: t(11;18)(q21;q21) and (1;14)(p22;q32) were marked by a, respectively, moderate to strong nuclear BCL10 staining pattern while t(14;18)(q32;q21)-positive MALT lymphomas were characterised by a perinuclear BCL10 staining pattern. This study further supports the close interaction between the MALT1 and BCL10 proteins in the pathogenesis of MALT lymphomas and may indicate that BCL10 immunohistochemistry is a simple technique to identify those MALT lymphoma cases with an underlying genetic aberration.     

t(11;18)(q21;q21) may delineate a spectrum of diffuse small B-cell lymphoma with extranodal involvement

We describe a patient with stage IV non-Hodgkin's lymphoma (NHL) and a t(11;18)(q21;q21) translocation. He presented with a gastric small B-cell lymphocytic lymphoma, expressing IgAL immunoglobulins without expression of CD10, CD5, and CD23 antigens. The lymphoma was the final development of a 6-year history of a monoclonal IgAL increase complicated by severe renal failure due to membranoproliferative glomerulonephritis. The clinical, histological, immunologic, and cytogenetic features of this patient are very similar to those observed in the five other patients with t(11;18) reported to date. This translocation therefore seems to delineate a new subtype of diffuse small B-cell lymphoma with involvement of mucosal sites. Involvement of the BCL2 oncogene on 18q21 could not be detected using molecular techniques with 5′ as well as 3′ BCL2 probes, indicating that other, so far unknown, genes relevant to lymphoid differentiation could be located in 18q21 and 11q21. © 1993 Wiley-Liss, Inc.     

Activation of the NF-kappaB signalling pathway in diffuse large B-cell lymphoma: clinical implications

Aim: To characterize the activation of the nuclear factor (NF)‐κB pathway in diffuse large B‐cell lymphoma (DLBCL) by immunohistochemistry. Methods and results: Sixty‐six DLBCLs treated with anthracycline‐containing chemotherapy were evaluated with antibodies against phosphorylated p65 (P‐p65), p65, p50, p52, IKKα, and phosphorylated IκB (P‐IκB). NF‐κB activation was based on the expression of P‐p65, P‐IκB, and nuclear expression of p65 or p52 in the tumour cells. P‐p65 and P‐IκB were expressed in 13 (20%) and 17 cases (26%), respectively. p65, p52 and IKKα were found in the cytoplasm. A correlation was found between expression of P‐p65 and P‐IκB (P < 0.0001), but not between the two subtypes of DLBCL [germinal centre B cell and non‐germinal centre (GC)]. P‐p65+ tumours showed a better response to chemotherapy (P = 0.025) and a trend to increased event‐free survival (P = 0.08). However, P‐IκB expression was not associated with either clinical response or survival. Bcl‐2 was not preferentially expressed on DLBCL tumours with NF‐κB activation, as determined by expression of P‐p65 and P‐IκB proteins. Conclusions: NF‐κB activation in DLBCL is preferentially mediated through the classical pathway and a novel mechanism involving phosphorylation of p65. Activation of NF‐κB by P‐p65 is associated with good prognosis. NF‐κB activation is not confined to non‐GC DLBCL exclusively.     

Mucosa-associated lymphoid tissue lymphoma: molecular pathogenesis and clinicopathological significance

Mucosa-associated lymphoid tissue (MALT) lymphoma is a low-grade tumor closely associated with chronic inflammation such as that of Helicobacter pylori gastritis, Sjogren's syndrome, and Hashimoto's thyroiditis. Tumor regression by H. pylori eradication alone is well known in gastric MALT lymphoma, but some tumors occur in the absence of pre-existing chronic inflammation. The understanding of MALT lymphoma biology has significantly improved, and recurrent cytogenetic alterations have been detected. These include the trisomies 3 and 18, and the translocations t(11;18)(q21;q21), t(1;14)(p22;q32), t(14;18)(q32;q21), and t(3;14)(p14.1;q32). At least some of these alterations result in the constitutive activation of the nuclear factor (NF)-kappaB pathway, and may exert anti-apoptotic action. Apoptosis inhibitor 2-MALT lymphoma-associated translocation 1 (API12-MALT1) fusion, resulting from t(11;18)(q21;q21), is specific to, and is the most common in, MALT lymphomas, and its clinicopathological significance has been studied extensively. The focus of the present review is on the recent progress made in elucidating MALT lymphomagenesis and its clinicopathological impact, especially in terms of the effect of API2-MALT1 fusion on this unique tumor.     

18q21 Rearrangement and trisomy 3 in extranodal B-cell lymphomas: a study using a fluorescent in situ hybridisation technique

t(11;18)(q21;q21) Translocation and trisomy 3 are the most common chromosomal aberrations reported in low-grade mucosa-associated lymphoid tissue (MALT) lymphoma. The current study aims to investigate the frequency of these chromosomal aberrations in a series of 52 extranodal B-cell lymphomas. The tumours were categorised into three histological grades: grade 1 (low-grade lymphoma of MALT type), grade 2 [diffuse large B-cell lymphoma (DLBCL) with MALT component] and grade 3 (DLBCL without MALT component). Fluorescence in situ hybridisation analyses on paraffin tissue sections were performed using a locus-specific probe for the 18q21 region and a centromeric probe for chromosome 3. The 18q21 rearrangement was detected in 9 of 40 (23%) cases, including 7 of 23 (30%) grade-1 and 2 of 11 (18%) grade-3 tumours. Amplification of the 18q21 region was detected in 10 of 40 (25%) cases, and trisomy 3 was detected in 9 of 34 (26%) cases. Amplification of the 18q21 region may be an important alternative pathogenetic pathway in MALT lymphoma and was found almost exclusively in tumours without 18q21 rearrangement. Our study showed that tumours with 18q21 rearrangement and 18q21 amplification develop along two distinct pathways, and the latter was more likely to transform into high-grade tumours upon acquisition of additional genetic alterations, such as trisomy 3. Trisomy 3 was more frequently found in coexistence with 18q21 abnormalities, suggesting that it was more likely to be a secondary aberration.