Structural determinants of mitochondrial STAT3 targeting and function

Signal transducer and activator of transcription (STAT) 3 has been found within mitochondria in addition to its canonical role of shuttling between cytoplasm and nucleus during cytokine signaling. Mitochondrial STAT3 has been implicated in modulation of cellular metabolism, largely through effects on the respiratory electron transport chain. However, the structural requirements underlying mitochondrial targeting and function have remained unclear. Here, we show that mitochondrial STAT3 partitions between mitochondrial compartments defined by differential detergent solubility, suggesting that mitochondrial STAT3 is membrane associated. The majority of STAT3 was found in an SDS soluble fraction copurifying with respiratory chain proteins, including numerous components of the complex I NADH dehydrogenase, while a minor component was found with proteins of the mitochondrial translation machinery. Mitochondrial targeting of STAT3 required the amino-terminal domain, and an internal linker domain motif also directed mitochondrial translocation. However, neither the phosphorylation of serine 727 nor the presence of mitochondrial DNA was required for the mitochondrial localization of STAT3. Two cysteine residues in the STAT3 SH2 domain, which have been previously suggested to be targets for protein palmitoylation, were also not required for mitochondrial translocation, but were required for its function as an enhancer of complex I activity. These structural determinants of STAT3 mitochondrial targeting and function provide potential therapeutic targets for disrupting the activity of mitochondrial STAT3 in diseases such as cancer.

BCL10 Mutations Define Distinct Dependencies Guiding Precision Therapy for DLBCL

Activated B cell-like diffuse large B-cell lymphomas (ABC-DLBCL) have unfavorable outcomes and chronic activation of CARD11-BCL10-MALT1 (CBM) signal amplification complexes that form due to polymerization of BCL10 subunits, which is affected by recurrent somatic mutations in ABC-DLBCLs. Herein, we show that BCL10 mutants fall into at least two functionally distinct classes: missense mutations of the BCL10 CARD domain and truncation of its C-terminal tail. Truncating mutations abrogated a motif through which MALT1 inhibits BCL10 polymerization, trapping MALT1 in its activated filament-bound state. CARD missense mutations enhanced BCL10 filament formation, forming glutamine network structures that stabilize BCL10 filaments. Mutant forms of BCL10 were less dependent on upstream CARD11 activation and thus manifested resistance to BTK inhibitors, whereas BCL10 truncating but not CARD mutants were hypersensitive to MALT1 inhibitors. Therefore, BCL10 mutations are potential biomarkers for BTK inhibitor resistance in ABC-DLBCL, and further precision can be achieved by selecting therapy based on specific biochemical effects of distinct mutation classes.

SIGNIFICANCE

ABC-DLBCLs feature frequent mutations of signaling mediators that converge on the CBM complex. We use structure-function approaches to reveal that BCL10 mutations fall into two distinct biochemical classes. Both classes confer resistance to BTK inhibitors, whereas BCL10 truncations confer hyperresponsiveness to MALT1 inhibitors, providing a road map for precision therapies in ABC-DLBCLs. See related commentary by Phelan and Oellerich, p. 1844. This article is highlighted in the In This Issue feature, p. 1825.

Mechanistic rationale for inhibition of poly(ADP-ribose) polymerase in ETS gene fusion-positive prostate cancer

Recurrent fusions of ETS genes are considered driving mutations in a diverse array of cancers, including Ewing's sarcoma, acute myeloid leukemia, and prostate cancer. We investigate the mechanisms by which ETS fusions mediate their effects, and find that the product of the predominant ETS gene fusion, TMPRSS2:ERG, interacts in a DNA-independent manner with the enzyme poly (ADP-ribose) polymerase 1 (PARP1) and the catalytic subunit of DNA protein kinase (DNA-PKcs). ETS gene-mediated transcription and cell invasion require PARP1 and DNA-PKcs expression and activity. Importantly, pharmacological inhibition of PARP1 inhibits ETS-positive, but not ETS-negative, prostate cancer xenograft growth. Finally, overexpression of the TMPRSS2:ERG fusion induces DNA damage, which is potentiated by PARP1 inhibition in a manner similar to that of BRCA1/2 deficiency.

Real-time multiplex PCR assays

The ability to multiplex PCR by probe color and melting temperature (T(m)) greatly expands the power of real-time analysis. Simple hybridization probes with only a single fluorescent dye can be used for quantification and allele typing. Different probes are labeled with dyes that have unique emission spectra. Spectral data are collected with discrete optics or dispersed onto an array for detection. Spectral overlap between dyes is corrected by using pure dye spectra to deconvolute the experimental data by matrix algebra. Since fluorescence is temperature dependent and depends on the dye, spectral overlap and color compensation constants are also temperature dependent. Single-labeled probes are easier to synthesize and purify than more complex probes with two or more dyes. In addition, the fluorescence of single-labeled probes is reversible and depends only on hybridization of the probe to the target, allowing study of the melting characteristics of the probe. Although melting curves can be obtained during PCR, data are usually acquired at near-equilibrium rates of 0.05-0.2 degrees C/s after PCR is complete. Using rapid-cycle PCR, amplification requires about 20 min followed by a 10-min melting curve, greatly reducing result turnaround time. In addition to dye color, melting temperature can be used for a second dimension of multiplexing. Multiplexing by color and T(m) creates a "virtual" two-dimensional multiplexing array without the need for an immobilized matrix of probes. Instead of physical separation along the X and Y axes, amplification products are identified by different fluorescence spectra and melting characteristics.

Solution-based scanning for single-base alterations using a double-stranded DNA binding dye and fluorescence-melting profiles

DNA molecules differing by as little as a single-base substitution have traditionally been distinguished by gel electrophoresis-based methodologies that exploit differences in the sequence-specific properties of double-stranded DNA (dsDNA) such as melting temperature and secondary conformational configuration. By comparison, solution-based fluorescence methods using sequence-specific probes are limited to detecting mutations restricted to very short segments of DNA ( approximately 20 bp). We describe a solution-based fluorescence method that discriminates between wild-type and mutant sequences using a dsDNA binding dye, and interrogates a region of >200 nucleotides. This method is based on melting theory and entails fluorescence monitoring of the melting temperatures of GC-clamped amplicons subjected to gradual and progressive thermal denaturation in the presence of a constant concentration of urea. Heterozygous samples are easily identified by the lower melting temperatures of the less thermodynamically stable heteroduplex mismatches from the wild-type:mutant DNA hybrids as compared to the more stable wild-type Watson-Crick duplexes. All of the four possible sets of mismatches (A.G/T.C, T.G/A.C, G.G/C.C, and T.T/A.A) represented in 17 heterozygous mutations distributed throughout the length of 20 different amplicons (104 to 212 bp), were distinguished from the wild-type by their altered melting profiles. This methodology is advantageous in that it obviates gel electrophoresis or labeled oligonucleotide probes. Significantly, it expands the region of interrogation for detection of single-base changes using fluorescence-based methods in solution, and is amenable for automation and adaptation to high-throughput systems.

ALK1 and p80 expression and chromosomal rearrangements involving 2p23 in inflammatory myofibroblastic tumor

BACKGROUND

Inflammatory myofibroblastic tumor (IMT) is an uncommon tumor of extrapulmonary and pulmonary tissues with an unpredictable clinical course, occasional recurrences, and rare malignant transformation. Clonal abnormalities with rearrangements of chromosome of 2p23 and the ALK gene have been reported in a few cases. The purpose of this study is to investigate whether these are consistent abnormalities among IMTs or represent a distinct subset.

DESIGN

Formalin-fixed, paraffin-embedded archival tissue sections from 47 IMTs in 40 patients were immunostained with monoclonal antibodies against ALK and p80. Fluorescence in situ hybridization for ALK rearrangements was done on 22 IMTs from 19 patients. Findings were correlated with clinical features and outcome.

RESULTS

ALK positivity was observed in 17 of 47 IMTs (36%) and p80 positivity in 16 of 47 IMTs (34%). Fluorescence in situ hybridization showed ALK rearrangements in nine cases (47%), aneuploidy in three cases (16%), and no rearrangement in seven cases (37%). IMTs with ALK abnormalities by immunohistochemistry and/or fluorescence in situ hybridization originated in the abdomen/pelvis/retroperitoneum, chest, and extremities. The mean age was 6.6 years, with a male/female ratio of 1.3. 64% of patients had no evidence of disease at last follow-up, 45% had one or more recurrences, and 18% displayed histologic evidence of malignant transformation. The IMTs without ALK abnormalities occurred in older children, were more frequent in females, and had fewer recurrences. However, in this group of 40 patients, the differences between the groups with and without ALK abnormalities did not have statistical significance. Aneuploidy without ALK abnormalities was associated with malignant transformation in three of five cases.

CONCLUSIONS

Abnormalities of ALK and p80 and evidence of chromosomal rearrangements of 2p23 occur in a significant proportion of IMTs. These changes are most frequent in abdominal and pulmonary IMTs in the first decade of life and are associated with a higher frequency of recurrence. These findings confirm the neoplastic nature of a subset IMT with ALK abnormalities and suggest that aneuploid IMT is a subset with more aggressive clinical behavior.

Loss of p53 tumor suppressor function is required for in vivo progression of Friend erythroleukemia

A role for p53 in the in vivo progression of Friend virus-induced erythroleukemia has been suggested but not clearly defined. We developed a Friend virus-sensitive, p53-deficient mouse model to directly address the role of p53 in Friend erythroleukemia. When infected with the polycythemia-inducing strain of Friend virus (FVP), p53 null mice exhibited accelerated progression to erythroleukemia and accelerated death following diagnosis when compared to wild type mice. Confirmation that p53 mutations were required for disease progression was provided by sequence analysis of p53 transcripts in leukemic wild type and heterozygous mice. All transcripts evaluated had point mutations, deletions or insertions in the p53 gene. The ability to grow tumor colonies in vitro and derive cell lines was enhanced in FVP-infected p53 null animals. Although PU.1 oncogene overexpression is a common mutation observed in cell lines derived from Friend virus-infected p53 wild type mice, it was not a universal finding in cell lines derived from p53 null animals. Our data conclusively demonstrate that loss of p53 function is a requirement for progression of Friend erythroleukemia in vivo. Further, the data demonstrate that erythroleukemias arising in Friend virus-infected p53 null mice are biologically and genetically distinct from those that occur in wild type animals, suggesting that the temporal order of PU.1 and p53 mutations is an important parameter in the pathogenesis of leukemic development.

Significance of lymphoglandular bodies in bone marrow aspiration smears

The presence of lymphoglandular bodies (LGB) or Söderström bodies is often stated to be a feature of lymphoid processes. In our experience, LGB are typically identified in B-cell processes but not in T-cell lymphomas or myeloid leukemias. We reviewed 136 bone marrow aspirate smears. The number of LGB per five high-power fields was counted, and median counts for B-cell processes, non-B-cell processes, myeloid leukemias, and T-cell malignancies were obtained and compared by the Wilcoxon rank sum test. Bone marrow aspirate smears involved with B-cell malignancies contained a median of 30 (range, 1-250) LGB per five high-power fields. Compared to myeloid leukemias (median, 11; range, 1-253) and T-cell malignancies (median, 7; range, 0-41), the differences were statistically significant (P < 0.001 and P = 0.01, respectively). While lymphoglandular bodies can be seen in a variety of malignant hematopoietic and nonhematopoietic disorders, they are found in significantly greater numbers in B-cell malignancies.

Phenotypic distinction and functional characterization of pro-B cells in adult mouse bone marrow

A lymphoid-committed progenitor population was isolated from mouse bone marrow based on the cell surface phenotype Thy-1.1(neg)Sca-1(pos)c-Kit(low)Lin(neg). These cells were CD43(pos)CD24(pos) on isolation and proliferated in response to the cytokine combination of steel factor, IL-7, and Flt3 ligand. Lymphoid-committed progenitors could be segregated into more primitive and more differentiated subsets based on expression of AA4.1. The more differentiated subset generated only B lymphoid cells in 92% of total colonies assayed, lacked T lineage potential, and expressed Pax5. These studies have therefore defined and isolated a B lymphoid-committed progenitor population at a developmental stage corresponding to the initial expression of CD45R.

Small lymphocytic lymphoma with perifollicular, marginal zone, or interfollicular distribution

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) typically involves nodal or extranodal tissues as a diffuse proliferation with pseudofollicular growth centers obliterating normal architecture. We describe 16 cases of CLL/SLL in which the neoplasm was confined to the marginal zone, perifollicular, or interfollicular regions surrounding benign lymphoid follicles in either nodal or extranodal sites. Twelve of 12 (100%) patients with adequate staging data had disseminated disease (Stage III or IV) at presentation. Eight of the 16 (50%) patients had absolute peripheral lymphocytosis (range, 5 to 30 x 10(9)/L). Pseudofollicular growth centers were identified in 14 of 16 cases (87.5%). Immunophenotypic studies revealed that the tumor cells were positive for CD20 (16/16) and CD5 (11/11) in all cases examined. CD23 was positive in 12 of 14 (86%) interpretable cases. IgM and IgD were positive in 13 of 14 (93%) and 10 of 10 (100%) interpretable cases, respectively. All cases were negative for CD3 (16/16), CD45RO (16/16), CD10 (15/15), and cyclin D1 (15/15). We conclude that CLL/SLL can have unusual patterns of involvement, including marginal zone, perifollicular, and interfollicular patterns that can be difficult to recognize histologically. Thirteen of 16 (81%) cases in this study were misinterpreted by the referring pathologists. Recognition of proliferation centers coupled with demonstration of a CD5+ CD23+ B-cell immunophenotype establishes the correct diagnosis of CLL/SLL.

Follicular lymphoma with monocytoid B-cell proliferation: molecular assessment of the clonal relationship between the follicular and monocytoid B-cell components

Although a number of studies have recognized that follicular lymphomas may be accompanied by a prominent proliferation of monocytoid B-cells, the clonal relationship between these components has not been adequately assessed. Using laser capture microdissection, we isolated the follicular and monocytoid B-cell components from four well-characterized cases of follicular lymphoma with prominent monocytoid B-cells. DNA from each component was analyzed using polymerase chain reaction (PCR)-based methods to assess for clonal rearrangements of the immunoglobulin heavy chain gene (IgH) and for the presence of the bcl-2 gene major breakpoint region/joining region (MBR/JH) DNA fusion products by conventional PCR and fluorescence melting curve analysis. Evidence of clonal identity was established in the follicular and monocytoid B-cell components of three cases by demonstration of IgH gene rearrangements of identical size using IgH PCR, by comparison of complementarity determining region III (CDRIII) DNA sequences, or by detection of bcl-2 MBR/JH fusion products of identical size and/or melting temperature. Molecular analysis of the fourth case revealed a monoclonal and MBR/JH-positive follicular component accompanied by a polyclonal and MBR/JH-negative monocytoid B-cell proliferation. We conclude that the follicular and monocytoid B-cell components of this variant of follicular lymphoma are clonally identical in the majority of cases. However, in a minority of these cases, the monocytoid B-cell component is reactive. Larger studies that assess the prognostic significance of follicular lymphoma with monocytoid B-cells will benefit from molecular studies that assess the clonal relationship of both components.

B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma involving bone marrow with an interfollicular pattern

B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) may involve the bone marrow in nodular, interstitial, diffuse, or mixed patterns. However, B-cell CLL/SLL associated with large reactive germinal centers (the so-called interfollicular pattern) involving the bone marrow is not reported. We describe 2 examples of B-cell CLL/SLL that subtotally replaced the bone marrow with an interfollicular pattern. In both cases, the neoplasms were composed of small round lymphoid cells; proliferation centers also were present. The neoplasms surrounded large reactive germinal centers that were devoid of peripheral mantle zones. The germinal centers were paratrabecular and nonparatrabecular in case 1 and nonparatrabecular in case 2. Flow cytometry immunophenotypic studies done on bone marrow aspiration samples of both cases showed a uniform population of neoplastic cells positive for pan-B-cell antigens and the CD5 and CD23 antigens. Immunohistochemical studies done on bone marrow biopsy sections supported the flow cytometry results and demonstrated that the germinal centers were negative for BCL-2. B-cell CLL/SLL may rarely involve the bone marrow with an interfollicular pattern. Knowledge of this pattern will prevent confusion with follicle center lymphoma and large cell transformation, both of which initially were considered in the differential diagnosis of these cases.

PCR analysis of the immunoglobulin heavy chain gene in polyclonal processes can yield pseudoclonal bands as an artifact of low B cell number

Polymerase chain reaction (PCR)-based analysis for detecting immunoglobulin heavy chain gene (IgH) rearrangements in lymphoproliferative disorders is well established. The presence of one or two discrete bands is interpreted as a monoclonal proliferation, whereas a smear pattern represents a polyclonal population. Prompted by our observation of discrete bands in histologically reactive processes with a relative paucity of B cells, we sought to determine whether low numbers of B cells in biopsy specimens could artifactually produce pseudomonoclonal bands. We performed IgH PCR analysis on serially diluted DNA samples from 5 B cell non-Hodgkin's lymphomas (B-NHLs), 5 reactive lymph nodes, 5 reactive tonsils and 10 microdissected germinal centers from a lymph node with follicular hyperplasia. We also assessed multiple aliquots of DNA samples from small biopsy specimens of reactive lymphocytic processes from the stomach (5 cases). PCR products were evaluated using high resolution agarose or polyacrylamide gels, and DNA sequencing was performed on IgH PCR products from two reactive germinal centers, which yielded monoclonal bands of identical size. All 5 B-NHLs harboring monoclonal B cell populations yielded single discrete bands, which were maintained in all dilutions. By contrast, all of the reactive lesions with polyclonal patterns at 50 ng/microl starting template concentration showed strong pseudomonoclonal bands at dilutions of 1:1,000 to 1:1,500 in placental DNA. Two of the microdissected reactive germinal centers that showed bands of identical size on duplicate reactions were proven to have different IgH sequences by sequencing. We conclude that specimens containing low numbers of polyclonal B cells may produce pseudomonoclonal bands on IgH PCR analysis. IgH PCR analysis should be performed on multiple aliquots of each DNA sample, and only samples that yield reproducible bands of identical size can be reliably interpreted as monoclonal.

Primary anaplastic large cell lymphoma of the small intestine

We describe the clinicopathologic, immunophenotypic, and molecular findings in 4 cases of anaplastic large cell lymphoma (ALCL) arising in the small intestine. All patients were men with acute symptoms of gastrointestinal tract obstruction. The clinical preoperative diagnosis was gastrointestinal carcinoma in 3 cases, and pancreatic carcinoma in 1 case. Histologic examination revealed cohesive aggregates of neoplastic cells, with multiple vesicular nuclei, prominent nucleoli, and abundant amphophilic cytoplasm. There was no clinical or histopathologic evidence of enteropathy. All cases were CD30+, and all showed evidence of T-cell lineage with cytotoxic potential by expression of CD3, CD43, or CD45RO; T-cell intracellular antigen-1; or perforin. One tumor showed p80 and anaplastic lymphoma kinase (ALK) overexpression corroborated by the presence of the t(2:5). One tumor expressed Epstein-Barr virus latent membrane protein. In all cases, the tumor cells were negative for CD20, CD15, CD56, and cytokeratin. Polymerase chain reaction revealed clonal rearrangements of the T-cell receptor gamma-chain gene, without evidence of immunoglobulin heavy-chain gene rearrangement. The diagnosis of primary bowel ALCL is facilitated by immunophenotypic and molecular studies. With 24 months of clinical follow-up, only the patient with the t(2:5)-positive tumor is alive and free of disease, suggesting that p80/ALK overexpression may be a good prognostic indicator.

Fluorescence melting curve analysis for the detection of the bcl-1/JH translocation in mantle cell lymphoma

PCR amplification and product analysis for the detection of chromosomal translocations such as bcl-1/JH have traditionally been performed as a two-step process with separate amplification and product detection. PCR product detection has generally entailed gel electrophoresis, hybridization, or sequencing for confirmation of assay specificity. By using a microvolume fluorimeter integrated with a thermal cycler and the PCR compatible double-stranded DNA (dsDNA) binding dye SYBR Green I, we simultaneously amplified and detected bcl-1/JH translocation products by using rapid cycle PCR and fluorescence melting curve analysis. We analyzed DNA from 25 cases of lymphoproliferative disorders comprising 12 previously documented bcl-1/JH-positive mantle cell lymphomas, and 13 reactive lymphadenopathies. The samples were coded and analyzed in a blind manner for the presence of bcl-1/JH translocations by fluorescence melting curve analysis. The results of fluorescence analysis were compared with those of conventional PCR and gel electrophoresis. All of the 12 cases (100%) previously determined to be bcl-1/JH positive by conventional PCR analysis showed a characteristic sharp decrease in fluorescence at about 86 degrees C by melting curve analysis. For easier visualization of melting temperatures (Tm), fluorescence melting peaks were obtained by plotting the negative derivative of fluorescence over temperature (-dF/dT) versus temperature (T). Dilutional assays revealed that fluorescence melting curve analysis was more sensitive than conventional PCR and agarose gel electrophoresis with ultraviolet transillumination by as much as 40-fold. Our results indicate that nucleic acid amplification integrated with fluorescence melting curve analysis is a simple, reliable, sensitive, and rapid method for the detection of bcl-1/JH translocations. The feasibility of specific PCR product detection without electrophoresis or expensive fluorescently labeled probes makes this methodology attractive for studies in molecular pathology.

Rapid simultaneous amplification and detection of the MBR/JH chromosomal translocation by fluorescence melting curve analysis

Polymerase chain reaction (PCR) amplification and product analysis for the detection of chromosomal translocations, such as the t(14;18), has traditionally been a two-step process. PCR product detection has generally entailed gel electrophoresis and/or hybridization or sequencing for confirmation of assay specificity. Using a microvolume fluorimeter integrated with a thermal cycler and a PCR-compatible double-stranded DNA (dsDNA) binding fluorescent dye (SYBR Green I), we investigated the feasibility of simultaneous thermal amplification and detection of MBR/JH translocation products by fluorescence melting curve analysis. We analyzed DNA from 30 cases of lymphoproliferative disorders comprising 19 cases of previously documented MBR/JH-positive follicle center lymphoma and 11 reactive lymphadenopathies. The samples were coded and analyzed blindly for the presence of MBR/JH translocations by fluorescence melting curve analysis. We also performed dilutional assays using the MBR/JH-positive cell line SUDHL-6. Multiplex PCR for MBR/JH and beta-globin was used to simultaneously assess sample adequacy. All (100%) of the 19 cases previously determined to be MBR/JH positive by conventional PCR analysis showed a characteristic sharp decrease in fluorescence at approximately 90 degrees C by melting curve analysis after amplification. Fluorescence melting peaks obtained by plotting the negative derivative of fluorescence over temperature (-dF/dT) versus temperature (T) showed melting temperatures (Tm) at 88.85+/-1.15 degrees C. In addition, multiplex assays using both MBR/JH and beta-globin primers yielded easily distinguishable fluorescence melting peaks at approximately 90 degrees C and 81.2 degrees C, respectively. Dilutional assays revealed that fluorescence melting curve analysis was more sensitive than conventional PCR and agarose gel electrophoresis with ultraviolet transillumination by as much as 100-fold. Simultaneous amplification and fluorescence melting curve analysis is a simple, reliable, and sensitive method for the detection of MBR/JH translocations. The feasibility of specific PCR product detection without electrophoresis or utilization of expensive fluorescently labeled probes makes this method attractive for routine molecular diagnostics.

Pathological findings in human autoimmune lymphoproliferative syndrome

The defects in lymphocyte apoptosis that underlie the autoimmune lymphoproliferative syndrome (ALPS) are usually attributable to inherited mutations of the CD95 (Fas) gene. In this report, we present the histopathological and immunophenotypic features seen in the lymph nodes (n = 16), peripheral blood (n = 10), bone marrow (n = 2), spleen (n = 3), and liver (n = 2) from 10 patients with ALPS. Lymph nodes showed marked paracortical hyperplasia. Interfollicular areas were expanded and populated by T cell receptor-alphabeta CD3+ CD4-CD8- (double-negative, DN) T cells that were negative for CD45RO. CD45RA+ T cells were increased in all cases studied. The paracortical infiltrate was a result of both reduced apoptosis and increased proliferation, as measured by in situ detection of DNA fragmentation and staining with MIB-1, respectively. The paracortical proliferation may be extensive enough to suggest a diagnosis of malignant lymphoma. Many of the paracortical lymphocytes expressed markers associated with cytotoxicity, such as perforin, TIA-1, and CD57. CD25 was negative. In addition, most lymph nodes exhibited florid follicular hyperplasia, often with focal progressive transformation of germinal centers; in some cases, follicular involution was seen. A polyclonal plasmacytosis also was present. The spleens were markedly enlarged, more than 10 times normal size. There was expansion of both white pulp and red pulp, with increased DN T cells. DN T cells also were observed in liver biopsies exhibiting portal triaditis. In the peripheral blood, the T cells showed increased expression of HLA-DR and CD57 but not CD25. CD45RA+ T cells were increased in the four cases studied. Polyclonal B cell lymphocytosis with expansion of CD5+ B cells was a characteristic finding. Taken together, the histopathological and immunophenotypic findings, particularly in lymph nodes and peripheral blood, are sufficiently distinctive to suggest a diagnosis of ALPS. Of note, two affected family members of one proband developed lymphoma (T-cell-rich B-cell lymphoma and nodular lymphocyte predominance Hodgkin's disease, respectively).

Splenic marginal zone cell lymphoma associated with clonal B-cell populations showing different immunoglobulin heavy chain sequences

Splenic marginal zone cell lymphomas (SMZCLs) are low-grade B-cell lymphomas that usually present with massive splenomegaly and subtle (subleukemic) peripheral blood involvement. Polymerase chain reaction (PCR) analysis of peripheral blood from a patient with subleukemic SMZCL showed evidence of two clonal immunoglobulin heavy chain (IgH) gene rearrangements. IgH PCR analysis of DNA derived from the patient's splenic neoplasm demonstrated a single clonal IgH rearrangement, which had a different electrophoretic mobility from either of the two PCR products detected in the patient's peripheral blood. Additional characterization of these PCR products by DNA sequencing demonstrated two independent IgH rearrangements in the peripheral blood, one of which used IgH joining region 6c (JH6C) and the other JH4. A different IgH rearrangement was present in the splenic tumor, which used JH4a. No sequences from the splenic neoplasm were detected in the peripheral blood and vice versa. This case illustrates that PCR might reveal monoclonal populations in peripheral blood unrelated to the presence of lymphoma in other anatomic compartments.

Cytotoxic granular protein expression, Epstein-Barr virus strain type, and latent membrane protein-1 oncogene deletions in nasal T-lymphocyte/natural killer cell lymphomas from Mexico

Nasal T-lymphocyte/natural killer cell lymphomas (nT/NKLs) are a distinct group of neoplasms highly associated with Epstein-Barr virus (EBV), with a high prevalence in Asia but rare in Western countries. Recent studies indicate that these neoplasms are of cytotoxic T- or NK-cell derivation. Previous studies identifying a characteristic 30-base pair deletion within the 3' end of latent membrane protein-1 (del-LMP-1) in other EBV-associated lymphomas suggested a pathogenetic role for del-LMP-1 in those neoplasms. We examined 23 cases of nT/NKL from Mexico for expression of the cytolytic granular proteins TIA-1 and perforin (PRF), and for the presence of EBV by in situ hybridization (ISH). Polymerase chain reaction was performed to identify the EBV (EBNA-2) strain type and the status of the LMP-1 gene (del-LMP-1). Controls consisted of 11 sinonasal B-cell lymphomas (nBLs) and 30 reactive tonsils (RTs) from healthy Mexican individuals. The nT/NKLs expressed TIA-1 in 21 (91%) of 23 cases and PRF in 15 (65%) of 23 cases. In contrast, all of the nBLs were negative for TIA-1 and PRF. Twenty-two (96%) of 23 nT/NKLs were positive for EBV by ISH. In contrast, only 2 (18%) of 11 nBLs were positive for EBV by ISH. EBV strain Type A was identified in 21 (91%) of 23 cases, whereas strain Type B was present in 2 (9%) of the 23 nT/NKLs. A similar percentage (80%) of Type A was noted in 12 of the 15 RTs. del-LMP-1 was detected in 6 (26%) of 23 nT/NKLs, comprising 4 cases of Type A and 2 of Type B. del-LMP-1 was detected in 9 (45%) of 20 RTs. Our results indicated that TIA-1 and PRF were sensitive markers of nT/NKL. The presence of del-LMP-1 in comparable frequencies in the RTs and nT/NKLs suggested to us that this genotype was common in the Mexican population and argued against a definite pathogenetic role for del-LMP-1 in nT/NKL.

Homozygous deletions at chromosome 9p21 involving p16 and p15 are associated with histologic progression in follicle center lymphoma

Low-grade follicle center lymphoma (LGFCL) is characterized genetically by the t(14;18) translocation and an indolent clinical course. Histologic progression from LGFCL to an aggressive diffuse large B-cell lymphoma (DLCL) occurs in 60% to 80% of cases, and this transformation is associated with the accumulation of secondary genetic alterations. Using 10 polymorphic microsatellite markers spanning the chromosome 9p21 region harboring the p15 (p15(INK4B)/MTS-2/CDKN2B) and p16 (p16(INK4A)/MTS-1/CDKN2) tumor-suppressor gene loci, we analyzed 11 matched pairs of LGFCL and their corresponding progressed DLCL biopsies for loss of heterozygosity and homozygous deletions at 9p21. A comparative multiplex polymerase chain reaction assay was also used for the detection of homozygous deletions. Deletions were identified in 8 of the 11 cases studied (73%): 6 homozygous (54%) and 2 hemizygous (18%). The deletions were identified exclusively in the progressed DLCL biopsies. Immunohistochemical studies showed an excellent correlation with the results from the genetic analyses. Of the 9 matched pairs of LGFCL and progressed DLCL with interpretable immunohistochemical staining, 9 of 9 (100%) of the LGFCL showed diffuse reactivity for p16. Four of the 9 (44%) immunohistochemically evaluable cases of progressed DLCL showed loss of or, in 1 case, markedly diminished p16 expression. All 4 of these cases correspondingly showed homozygous deletions at 9p21. Five of the 9 progressed DLCL cases showed p16 expression and demonstrated retention of one or both 9p21 alleles by genetic analysis. This is the first longitudinal series examining sequential biopsy specimens of low-grade and progressed FCL for genetic loss at 9p21 encompassing the p16 and p15 loci. The high frequency and exclusive occurrence of deletions involving p16 in the progressed DLCLs suggests that genetic loss at 9p21 targeting p16 and/or p15 is an important secondary genetic event in the histologic progression of FCL.

Subcutaneous panniculitic T-cell lymphoma is a tumor of cytotoxic T lymphocytes

Subcutaneous panniculitic T cell lymphoma (SCPTCL) is characterized by primary involvement of the subcutaneous fat in a manner mimicking panniculitis. We studied 16 cases of this lymphoma to define its immunophenotypical profile as well as cellular origin. Involvement of the subcutaneous fat in a lacelike pattern with neoplastic cells rimming individual fat spaces was present in all cases. All 16 cases were of T cell phenotype. Thirteen of the 16 cases were CD8+, whereas three were negative for both CD4 and CD8. Twelve cases were stained for betaF1; of these, eight were betaF1+ and four were betaF1-. Focal staining for CD56 and CD30 was seen in 2 of 13 and two of eight cases, respectively. Intense diffuse positivity for the cytotoxic granular proteins T cell intracellular antigen-1 (TIA-1) and perforin was present in all cases, indicating an origin from cytotoxic T lymphocytes. Ten cases studied for Epstein-Barr viral sequences were negative. Eight of 9 cases with amplifiable DNA showed a clonal TCR gamma gene rearrangement by polymerase chain reaction. Controls included seven cases of benign panniculitis and seven other peripheral T cell lymphomas involving the skin and subcutaneous tissues: two peripheral T cell lymphomas, not otherwise specified (PTL,NOS), four anaplastic large cell lymphomas (ALCL), one T/NK cell lymphoma. The seven cases of panniculitis lacked cytological atypia and were characterized by an admixture of CD4+ and CD8+ cells with interspersed aggregates of L26+ B cells. Only infrequent cells showed staining for TIA-1 and perforin. In the control cases of T cell lymphoma, the infiltrate had a tendency for dermal and sometimes even epidermal involvement, with sheeting out of malignant cells, in contrast to the characteristic subcutaneous localization and rimming of fat spaces noted in SCPTCL. The two PTL, NOS were CD4+ and negative for both TIA-1 and perforin. Although the remaining controls expressed TIA-1 and perforin, in keeping with their cytotoxic T or natural killer (NK) cell origin, histological and other immunophenotypical features allowed distinction from SCPTCL. Five cases of SCPTCL were also stained for apoptosis using a tdt-mediated end labeling kit. All cases showed numerous positive apoptotic bodies, suggesting apoptosis as the mechanism of cell death in these tumors. Our study indicates that SCPTCL constitutes a distinctive clinicopathological entity derived from cytotoxic T lymphocytes and should be differentiated from other benign and malignant lymphoid infiltrates involving the subcutis. The apoptosis seen in these tumors may be mediated by release of cytotoxic granular proteins.

Epstein-Barr virus strain type and latent membrane protein 1 gene deletions in lymphomas in patients with rheumatic diseases

OBJECTIVE

Recent studies have shown that immunomodulatory therapy for the treatment of rheumatic diseases can be associated with the development of Epstein-Barr virus (EBV)-associated lymphoproliferative disorders. The present study was undertaken to determine the strain type of EBV in lymphoproliferative disorders that occur in patients with rheumatic disease and to investigate EBV latent membrane protein 1 (LMP-1) gene deletions that occur in these lymphoproliferative disorders.

METHODS

Ten EBV-associated lymphoid neoplasms in patients with rheumatoid arthritis or dermatomyositis were analyzed by polymerase chain reaction to determine EBV strain type and to investigate for the presence of a previously characterized 30-basepair deletion in the LMP-1 gene.

RESULTS

The results indicated that lymphoproliferative disorders in these patients can harbor EBV strain type A or B, with a predominance of type A infection (80%). It was also shown that both wild-type and mutated LMP-1 genes can be found in these neoplasms, with the deleted form of the LMP-1 gene occurring in one-third of cases in this series.

CONCLUSION

LMP-1 deletions associated with certain aggressive lymphoid neoplasms are not required for the genesis of lymphoproliferative disorders in patients with rheumatic disease. The relative frequencies of type A and type B EBV strains in these lymphoproliferative disorders show similarities to the frequencies in patients with post-solid organ transplantation immunosuppression-associated lymphoproliferative disorders.

Lymphoproliferative disorders associated with congenital immunodeficiencies

This report reviews the clinicopathologic, immunologic, and molecular biological features of the congenital immunodeficiencies and their associated lymphoproliferative disorders (LPD) including cases presented at the Third Slide Workshop of the Society of Hematopathology, held in Duarte California, in October 1995. The congenital immunodeficiencies most commonly associated with LPD include Wiskott-Aldrich syndrome (WAS), common variable immunodeficiency (CVID), ataxia telangiectasia (AT), severe combined immunodeficiency (SCID), X-linked lymphoproliferative disorder (XLP), and hyper-IgM syndrome. Each form of immunodeficiency disorder is associated with its own risk factors, which affect the pattern of LPD encountered. AT is characterized by a defect in DNA repair. The lymphomas and leukemias in this syndrome resemble those seen in sporadic LPD, but tend to occur at an earlier age. Epstein-Barr virus (EBV) plays an important role in the LPD associated with many immunodeficiency disorders including WAS, CVID, SCID, and XLP. One should use a combination of clinical, histopathologic and molecular data in the evaluation of lymphoproliferative lesions in this group of patients. Immunophenotypic and molecular evidence of clonality does not necessarily imply an aggressive clinical course, an exemplified by some LPD in WAS, which may show evidence of monoclonality in serum and lymph nodes, and yet still behave in a benign or indolent fashion.

Marginal zone B-cell lymphoma with monocytoid B-cell lymphocytes in pediatric patients without immunodeficiency. A report of two cases

We report two cases of marginal zone B-cell lymphoma in two patients 6 and 18 years of age, respectively (cases 1 and 2) who had no clinical evidence of immunodeficiency or risk factors for human immunodeficiency virus (HIV) infection. Histologic analysis in both cases revealed diffuse nodal effacement by a monotonous population of atypical lymphoid cells with abundant pale cytoplasm and round to oval nuclei, with very infrequent mitotic activity. The neoplastic cells in both cases were of B-cell lineage (CD20 and CD79a positive), with CD43 coexpression. One case showed monoclonal light chain expression, and polymerase chain reaction analysis demonstrated clonal rearrangements of the immunoglobulin heavy chain gene in both cases. Abnormal cytogenetic findings were detected in case 2, in which metaphase spreads revealed trisomy 13 (karyotype 47, XY, +13). Although trisomy 13 has been described in association with acute nonlymphocytic leukemias and myelodysplastic syndromes, this case represents the first documented association of trisomy 13 with marginal zone B-cell lymphoma. Interphase cytogenetics analysis for trisomy 3, reported to be associated with mucosa-associated lymphoid tissue (MALT) lymphomas, was negative in both cases. Although low-grade lymphomas of the MALT type have been reported in HIV-positive patients, the two cases reported here are unique in that they occurred in young patients without HIV infection or any other evidence of immunodeficiency.

P53 expression in Reed-Sternberg cells does not correlate with gene mutations in Hodgkin's disease

Immunohistochemically detectable p53 protein expression is common in the Reed-Sternberg and Hodgkin's (RS-H) cells of Hodgkin's disease, but p53 gene mutations have only rarely been identified. The authors found p53 expression in RS-H cells in 16 of 30 cases of Hodgkin's disease (53%), with the percentage of RS-H positive cells ranging from 4% to 85%. In 12 of 30 cases (40%), at least 10% of the RS-H cells were positive for p53. p53 gene mutations were detected in only two cases (7%) using a single-stranded conformational polymorphism assay with a detection sensitivity of between 1% and 5%. The cellular protein, mdm-2, which can stabilize and functionally inactivate wild-type p53 protein, was expressed in RS-H cells in most of these cases (86%). However, neither case with a p53 gene mutation expressed mdm-2 (P < .005). The two cases with p53 gene mutations had a higher mean proliferative index than cases without detectable mutations (90% versus 72%; P < .02). p53 expression in RS-H cells may be related to concurrent mdm-2 protein expression and a p53-positive, mdm-2-negative immunophenotype may be predictive of gene mutations in RS-H cells.

Zoonotic Brugian lymphadenitis. An unusual case with florid monocytoid B-cell proliferation

Human infection with a zoonotic Brugia species in the United States is uncommon. Positive identification of the filarial nematode is required for histopathologic diagnosis. Many cases may go unrecognized because of the nonspecific clinical manifestations and the nondiagnostic histologic changes occurring in involved lymph nodes. A case of zoonotic Brugia lymphadenitis is described in a patient from Rhode Island, in which a small nongravid female worm was identified in a lymph node biopsy specimen. The lymph node also showed a spectrum of reaction changes including the presence of florid monocytoid B-cell proliferation, which has not been described in association with zoonotic Brugian filariasis.