Serum and urinary levels of CD222 in cancer: origin and diagnostic value.

The mannose 6-phosphate/insulin-like growth factor 2 receptor (CD222, M6P/IGF2R) is a multifunctional transmembrane type I receptor, mostly localized intracellularly, less on the surface of all types of mammalian cells. It is known both to transport lysosomal enzymes through their mannose 6-phosphate moieties and to internalize extracellular ligands like insulin-like growth factor 2 or plasminogen. CD222 is involved in regulation of cell proliferation, migration, T cell activation, and apoptosis. Soluble CD222 has been found in higher concentrations in sera of liver disease patients. In this study, we analysed the level of CD222 present in body fluids, namely in serum and urine, of cancer patients. We found significantly elevated levels of soluble CD222 in sera of cancer patients compared to healthy controls irrespective of the type of disease. The urine CD222 levels were increased specifically in breast cancer and multiple myeloma. In contrast to serum, CD222 was present within CD222-positive exosomes in urine pointing to different origins of CD222 present in various human body fluids. Based on this work, we propose serum soluble CD222 as a general biomarker for tumorigenesis.

A randomized phase III study of carfilzomib vs low-dose corticosteroids with optional cyclophosphamide in relapsed and refractory multiple myeloma (FOCUS).

This randomized, phase III, open-label, multicenter study compared carfilzomib monotherapy against low-dose corticosteroids and optional cyclophosphamide in relapsed and refractory multiple myeloma (RRMM). Relapsed and refractory multiple myeloma patients were randomized (1:1) to receive carfilzomib (10-min intravenous infusion; 20 mg/m2 on days 1 and 2 of cycle 1; 27 mg/m2 thereafter) or a control regimen of low-dose corticosteroids (84 mg of dexamethasone or equivalent corticosteroid) with optional cyclophosphamide (1400 mg) for 28-day cycles. The primary endpoint was overall survival (OS). Three-hundred and fifteen patients were randomized to carfilzomib (n=157) or control (n=158). Both groups had a median of five prior regimens. In the control group, 95% of patients received cyclophosphamide. Median OS was 10.2 (95% confidence interval (CI) 8.4-14.4) vs 10.0 months (95% CI 7.7-12.0) with carfilzomib vs control (hazard ratio=0.975; 95% CI 0.760-1.249; P=0.4172). Progression-free survival was similar between groups; overall response rate was higher with carfilzomib (19.1 vs 11.4%). The most common grade ⩾3 adverse events were anemia (25.5 vs 30.7%), thrombocytopenia (24.2 vs 22.2%) and neutropenia (7.6 vs 12.4%) with carfilzomib vs control. Median OS for single-agent carfilzomib was similar to that for an active doublet control regimen in heavily pretreated RRMM patients.

Bortezomib administered subcutaneously is well tolerated in bortezomib-based combination regimens used in patients with multiple myeloma.

OBJECTIVE: Bortezomib (Btz) has emerged as a standard of care in the treatment of patients with multiple myeloma (MM), but Btz-induced peripheral neuropathy (PNP) has a particularly negative impact on patients' quality of life. According to a recent study, PNP was significantly less frequent with subcutaneous administration of Btz. Here, we report our experience regarding the efficacy and tolerability of standard combination regimens in MM with subcutaneous Btz. METHODS: 14 consecutive patients with newly diagnosed MM were included in this analysis. Btz was used in different combination regimens (Btz with dexamethasone with/without thalidomide or Btz combined with melphalan and prednisone). Standard criteria were applied to evaluate response and toxicity. RESULTS: Hematological toxicities occurred only at grades 1-2 and included anemia (71%) and thrombocytopenia (21%). Nonhematologic side effects at grades 1-2 were local skin reactions at the subcutaneous injection site, which were self-limited. No notable gastrointestinal toxicity was observed with subcutaneous Btz, and therefore routine use of intravenous hydration and antiemetics was abandoned. Overall response rate for transplant-eligible patients was 86%. CONCLUSIONS: Our results confirm the improved toxicity profile of the subcutaneous administration of Btz in various standard Btz-based combination regimens. In addition, patient management with subcutaneous administration has been markedly ameliorated at our center.

Efficacy of the combination of bortezomib and dexamethasone in systemic AL amyloidosis.

Bortezomib-dexamethasone (Btz/Dex) is an active regimen in patients with multiple myeloma and has been used in few patients with amyloidosis. Here, we report a retrospective evaluation of the efficacy and toxicity of Btz/Dex in 26 patients with AL amyloidosis (AL). Eighteen patients (69%) received Btz/Dex as first-line treatment. Organs most frequently involved were kidneys (100%) and heart (35%); five patients (19%) had less than two organs involved. The overall response rate was 54% (14 of 26 patients), with eight patients (31%) achieving a hematologic complete remission (CR). All patients who reached a CR received Btz/Dex as first-line therapy. Median time to response was 7.5 weeks. Improvement in organ function was noticed in three patients (12%). Median progression-free survival (PFS) and overall survival (OS) was 5.0 and 18.7 months, respectively; in CR patients, however, median PFS and OS have not yet been reached. Toxicities were manageable, with hematological side effects being most common. No grade 3/4 neuropathy was observed. Our results confirm the activity of bortezomib/dexamethasone in patients with AL amyloidosis and suggest that patients achieving a CR have a marked benefit for survival.

International Myeloma Working Group molecular classification of multiple myeloma: spotlight review.

Myeloma is a malignant proliferation of monoclonal plasma cells. Although morphologically similar, several subtypes of the disease have been identified at the genetic and molecular level. These genetic subtypes are associated with unique clinicopathological features and dissimilar outcome. At the top hierarchical level, myeloma can be divided into hyperdiploid and non-hyperdiploid subtypes. The latter is mainly composed of cases harboring IgH translocations, generally associated with more aggressive clinical features and shorter survival. The three main IgH translocations in myeloma are the t(11;14)(q13;q32), t(4;14)(p16;q32) and t(14;16)(q32;q23). Trisomies and a more indolent form of the disease characterize hyperdiploid myeloma. A number of genetic progression factors have been identified including deletions of chromosomes 13 and 17 and abnormalities of chromosome 1 (1p deletion and 1q amplification). Other key drivers of cell survival and proliferation have also been identified such as nuclear factor- B-activating mutations and other deregulation factors for the cyclin-dependent pathways regulators. Further understanding of the biological subtypes of the disease has come from the application of novel techniques such as gene expression profiling and array-based comparative genomic hybridization. The combination of data arising from these studies and that previously elucidated through other mechanisms allows for most myeloma cases to be classified under one of several genetic subtypes. This paper proposes a framework for the classification of myeloma subtypes and provides recommendations for genetic testing. This group proposes that genetic testing needs to be incorporated into daily clinical practice and also as an essential component of all ongoing and future clinical trials.

Cytogenetic patterns in multiple myeloma after a phase of preceding MGUS.

BACKGROUND: Presenting the same histological diagnosis, multiple myeloma (MM) shows a large genomic variety, resulting in variable times of overall survival. MATERIALS AND METHODS: To investigate major cytogenetic categories (any 14q-translocation, t(11;14), t(4;14), 13q-deletions, 17p-deletions) and their clinical consequences in MM after a pre-existing monoclonal gammopathy (MM post-MGUS), we performed a comparative analysis of 41 patients with MM post-MGUS and 287 patients with unknown prior history MM (U-MM). RESULTS: In MM post-MGUS, a t(11;14) was found to be more frequent than in U-MM (24% vs. 14%) and it was associated with significantly shortened survival (24 months vs. 70 months in U-MM; P = 0.01). MM post-MGUS was further characterized by a higher frequency of 13q-deletions only (absence of all other specific abnormalities; 28% vs. 12% in U-MM; P = 0.02). A 13q-deletion only was an indicator of long survival in MM post-MGUS (median not yet reached) as opposed to U-MM (median survival, 29 months; P = 0.001). 17p-deletions were infrequent in MM post-MGUS (3% vs. 16% in U-MM; P = 0.04). Survival times for patients with t(4;14) and/or 17p-deletions and other abnormalities were similar in both MM patient cohorts. CONCLUSIONS: Our data suggest that t(11;14) and 13q-deletions have distinct prognostic implications in the context of MM post-MGUS.

Chromosomal abnormalities of young multiple myeloma patients (<45 yr) are not different from those of other age groups and are independent of stage according to the International Staging System.

Little is known about tumor-related prognostic factors, in particular specific chromosomal abnormalities, in young patients with multiple myeloma (MM). We therefore investigated the chromosomal pattern by interphase fluorescence in situ hybridization (chromosomes 13q14, 14q32-translocations, chromosomes associated with hyperdiploidy) in 38 young patients with MM (age <45 yr) and compared the results with those observed in 69 patients with intermediate age (45-70 yr) and 64 elderly patients (age >70 yr). All chromosomal patterns were not significantly different between the three age cohorts. Similarly, standard MM parameters were equally distributed between these MM patient populations. However, survival by the International Staging System (ISS) for MM revealed marked differences between stage I/II (median survival not yet reached) and stage III (23.4 months; P < 0.0003) among young MM patients. A significant survival difference between ISS-stage I/II and ISS-stage III patients was also noted in the intermediate age group (median 65.4 months vs. 24.6 months; P = 0.0009). However, this difference disappeared among elderly MM patients (39.6 months in ISS-stage I/II vs. 32 months in ISS-stage III patients; P = 0.94), but it was unrelated to the cytogenetic pattern. Our results indicate that MM in young patients does not represent a distinct biologic entity, and that short survival of younger MM patients at ISS-stage III is independent of the molecular cytogenetic pattern.

Bortezomib in relapsed multiple myeloma: response rates and duration of response are independent of a chromosome 13q-deletion.

Studies of bortezomib in patients with relapsed multiple myeloma (MM) suggested that bortezomib may be active even in the presence of adverse prognostic factors. We therefore evaluated 62 patients with relapsed/refractory MM who were treated with single-agent bortezomib, and addressed the question whether or not the negative prognostic impact of unfavorable cytogenetic abnormalities may be overcome by bortezomib. By interphase fluorescence in situ hybridization (FISH), a deletion of chromosome 13q14 [del(13q14)] was present in 33 patients (53%). Overall response rates to bortezomib were similar in patients with and without del(13q14) (45 versus 55%; P=0.66), and rates of complete remission (CR) near CR were also not different between the two patient populations (18 versus 14%). Three patients had a t(4;14)(p16;q32) in addition to del(13q14), and all of them had a >50% paraprotein reduction. Median duration of response was 12.3 months in patients with del(13q14) compared with 9.3 months in patients with normal 13q-status (P=0.25), and survival was also not different between the two patient populations. Patients not benefiting from single-agent bortezomib were characterized by the combined presence of a del(13q14) and low serum albumin (median survival 4.6 months). Our results provide evidence for remarkable activity of bortezomib in MM with del(13q14). Patients who do not respond to bortezomib and consecutively have short time to treatment failure and overall survival can be identified by low serum albumin in addition to del(13q14) and should be considered for bortezomib combinations.

In vivo effects of imatinib mesylate on human haematopoietic progenitor cells.

BACKGROUND: Imatinib mesylate has considerable antineoplastic activity in patients with chronic myeloid leukaemia (CML) and some solid tumours. Although originally regarded as nontoxic for normal haematopoiesis, mild to moderate myelosuppression is a commonly observed side-effect of this treatment. Recently, this molecule has been shown to suppress normal haematopoietic progenitor cells in vitro. This is the first study that has investigated the effect of imatinib on haematopoietic progenitor cells in vivo. MATERIALS AND METHODS: We investigated the number of circulating haematopoietic progenitor cells in 79 patients with CML and five patients with solid tumours who were treated with imatinib for at least 3 months. Bone marrow progenitor cells were assessed in a subgroup of 18 patients with CML after 12 months of imatinib treatment. Results were compared with haematopoietic progenitor cell numbers of normal controls. RESULTS: Circulating progenitors of all classes were significantly decreased in CML up to 24 months of imatinib therapy compared with healthy controls (median progenitor cells in CML after 12 months: CFU-GM 62, range 0-2543; BFU-E 216, range 0-3259; CFU-GEMM 0, range 0-139; versus controls: CFU-GM 208, range 50-936; BFU-E 690, range 120-1862; CFU-GEMM 20, range 4-77; P < 0.001). Similar reductions in the number of progenitor cells derived from bone marrow were found in a subgroup of 18 patients with CML. In patients with solid tumours the number of circulating progenitor cells was significantly lower under treatment with imatinib when compared with the controls. Withdrawal of imatinib in a patient with a malignant brain tumour resulted in a prompt normalization of circulating progenitors. CONCLUSIONS: This study suggests that imatinib exerts myelosuppressive effects through inhibition of haematopoietic progenitor cells.

Chemotherapy with cyclophosphamide, doxorubicin, etoposide, vincristine and prednisone (CHOEP) is not effective in patients with enteropathy-type intestinal T-cell lymphoma.

BACKGROUND: Enteropathy-type intestinal T-cell lymphoma (ETCL) is a highly aggressive disease with poor response to conventional CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) chemotherapy. According to promising data with the addition of etoposide (E) to the CHOP regimen (CHOEP) in aggressive lymphomas including T-cell lymphomas, we have treated patients with ETCL with CHOEP chemotherapy. PATIENTS AND METHODS: Ten consecutive patients (six female, four male) suffering from ETCL were given CHOEP at our institution. Four patients had advanced disease (stage III/IV), while five patients were rated to be in stage II and one in stage I. Treatment consisted of doxorubicin 50 mg/m2, cyclophosphamide 750 mg/m2 and vincristine 1.4 mg/m2 by intravenous infusion on day 1, etoposide 100 mg/m2 intravenously days 1-3 and oral prednisone days 1-5. Cycles were repeated every 3 weeks for a maximum of six courses. Assessment of response was done by means of conventional computed tomography scanning, endoscopy and also [18F]fluorodeoxyglucose positron emission tomography (FDG PET) in seven patients. RESULTS: A total of 41 cycles (median six, range one to six) were administered to our patients. Leukocytopenia/neutropenia WHO grade IV necessitating granulocyte colony-stimulating factor support occurred in all patients evaluable for toxicity, and febrile neutropenia was seen in two patients. Two patients had to undergo emergency surgery due to intestinal perforation after one and three courses of treatment, respectively. Therapeutic results, however, were disappointing: two patients had complete remission (CR), three had partial remissions and five patients progressed during treatment. Remissions, however, where only short-lasting, as only two patients are alive at a median follow-up of 7 months (range 2-16). One patient is in ongoing CR 10 months after initiation of chemotherapy and the other is currently undergoing second-line treatment for progressive disease as judged by follow-up investigations after three cycles of CHOEP. CONCLUSIONS: Our data demonstrate that CHOEP chemotherapy results in a high rate of hematotoxicity in patients with ETCL. In spite of this, therapeutic results were disappointing and do not appear to be superior to conventional CHOP chemotherapy. We conclude that CHOEP cannot be recommended for routine use in patients with ETCL.

Both IGH translocations and chromosome 13q deletions are early events in monoclonal gammopathy of undetermined significance and do not evolve during transition to multiple myeloma.

Molecular and genetic events associated with the transition from monoclonal gammopathy of undetermined significance (MGUS) to multiple myeloma (MM) are still poorly characterized. We investigated serial bone marrow specimens from 11 patients with MGUS who eventually progressed to MM (MM post-MGUS) by interphase fluorescence in situ hybridization for immunoglobulin heavy-chain gene (IgH) translocations and chromosome 13q deletions (del(13q)). In nine patients, IgH translocations were present both in MGUS and MM post-MGUS plasma cells, including three t(11;14)(q13;q32) and one t(4;14)(p16;q32), which was observed already 92 months prior to MM. Similarly, all five MM patients with del(13q) had this aberration already at the MGUS stage. Two patients without IgH translocation and del(13q) had chromosomal gains suggesting hyperdiploidy, but IgH translocations and/or del(13q) did not emerge at MM post-MGUS. IgH translocations and del(13q) are early genetic events in monoclonal gammopathies, suggesting that additional events are required for the transition from stable MGUS to progressive MM.

Rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) for treatment of early-stage gastric diffuse large B-cell lymphoma.

BACKGROUND: Diffuse large B-cell lymphoma (DLBCL) of the stomach is a relatively common disease. Recently, chemotherapy consisting of doxorubicin, cyclophosphamide, vincristine and prednisone (CHOP) has been reported as effective treatment for early-stage gastric DLBCL. Given the fact that the application of the CD20 antibody rituximab (R) in addition to CHOP has improved outcomes in nodal DLBCL, we have analysed our experience with application of R-CHOP in patients with early-stage gastric DLBCL. PATIENTS AND METHODS: Patients with histologically verified early-stage gastric DLBCL undergoing treatment with R-CHOP for initial management were analysed. RESULTS: Fifteen patients received a total of 79 cycles, with a median of six cycles per patient. All patients responded to therapy, 13 had a complete remission (CR) (87%) and two (13%) a partial remission. All patients in CR, except one who died unrelated to lymphoma, have remained so with a median follow-up of 15 months (range 4-42) after treatment. Subjective tolerance was moderate, and toxicities were mainly haematological, including leukocytopenia WHO grade 3 and 4 in 10 and five patients each. The addition of rituximab to the standard CHOP regimen did not appear to significantly increase toxicity. CONCLUSIONS: Our data indicate that R-CHOP is an effective regimen for management of early-stage gastric DLBCL. However, given the excellent results with CHOP alone in such patients, the value of adding rituximab to standard CHOP remains to be determined in a randomised trial.

Diffuse large B-cell lymphomas with plasmablastic/plasmacytoid features are associated with TP53 deletions and poor clinical outcome.

To define reproducible criteria for subgroups of diffuse large B-cell lymphomas (DLBCL), including lymphomas with plasmablastic/plasmacytoid features (PB/PC-Fs), we investigated 66 DLBCL; the samples were categorized as either centroblastic (CB), immunoblastic (IB) or PB/PC-F applying standardized morphologic criteria. Blinded specimens were reviewed by three independent pathologists. The final consensus classification included 44 CB (67%), seven IB (10%) and 15 PB/PC-F (23%). The interobserver agreement between two centers (Vienna, Würzburg) was 93.5%. Most PB/PC-F were CD20+, cIgM+, MUM-1+, CD138+/-, bcl-6-, corresponding to an activated B-cell phenotype. Immunoglobulin-V(H) gene mutation analysis was consistent with a germinal or postgerminal center-cell origin. By fluorescence in situ hybridization analysis, 11/13 (85%) PB/PC-F had a monoallelic TP53 deletion. The pretreatment characteristics of patients with PB/PC-F included a tendency for more B symptoms, extranodal disease and a higher IPI. Importantly, PB/PC-F were resistant to standard chemotherapy (complete remission rate 47%, relapse rate 71%) and even autologous stem-cell transplantation. The median overall survival (OS) (14 months, P<0.002) and disease-free survival (6 months, P=0.02) were significantly shorter compared to patients with CB and IB. The OS difference was pronounced within the low and low-intermediate IPI risk group (P<0.001). Our data indicate a strong association of plasmablastic/plasmacytoid morphology with TP53 deletions, poor response to chemotherapy and short survival.

Treatment of extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) with mitoxantrone, chlorambucil and prednisone (MCP).

BACKGROUND: Mucosa-associated lymphoid tissue (MALT) lymphoma is a relatively common type of lymphoma arising in various tissues throughout the human body. Currently, there is no standard chemotherapy for advanced stage MALT lymphoma. This has prompted us to retrospectively analyse our experience with the MCP regimen (mitoxantrone, chlorambucil and prednisone) in patients with MALT lymphoma. PATIENTS AND METHODS: Patients with histologically verified MALT lymphoma undergoing chemotherapy with MCP were evaluated retrospectively. The MCP regimen consists of mitoxantrone 8 mg/m(2) intravenously on days 1 and 2, chlorambucil 3 x 3 mg/m(2) per os (p.o.) on days 1-5 and prednisone 25 mg/m(2) p.o. on days 1-5. Information analysed included localisation of the lymphoma, clinical stage, pretreatment, number of chemotherapy cycles administered, toxicity, response to treatment, follow-up time, relapse and survival. RESULTS: A total of 15 patients (six females and nine males aged between 34 and 88 years) with histologically ascertained MALT lymphoma undergoing treatment with the MCP regimen were identified from our records. Ten patients had extragastric lymphoma, while five patients suffered from gastric MALT lymphoma. All patients were chemotherapy-naïve, while two had been locally irradiated before application of MCP for recurrent disease. A total of 74 cycles was administered to our patients, with a median number of five cycles per patient. Eight (53%) patients achieved complete remission, six (40%) patients partial response and only one (7%) patient had progressive disease. Subjective tolerance was excellent, and toxicities were mainly haematological, including granulocytopenia World Health Organisation grade 3 and 4 in three patients each. In two patients, this was accompanied by single episodes of uncomplicated herpes simplex infection. At the time of analysis, all patients are still alive. No relapses have occurred after a median follow-up time of 16 (range 12-29) months. CONCLUSIONS: Our data suggest that MCP is an effective and well-tolerated regimen for treatment of patients with MALT lymphoma irrespective of localisation. Judging from our data, MCP also appears to be a feasible regimen in elderly patients.

Beneficial effect of high-dose chemotherapy in multiple myeloma patients with unfavorable prognostic features.

It has been established that high-dose chemotherapy (HDT) improves the therapeutic outcome of patients with multiple myeloma (MM) as compared with standard-dose therapy (SDT); however, little is known about the impact of HDT on different prognostic groups of MM patients. We therefore compared the survival times of 77 patients with previously untreated MM who were enrolled in HDT regimens with those of 64 similar patients <65 years old, who would be eligible for HDT but were treated by SDT. Overall, HDT was superior to SDT with respect to achievement of complete remissions (28% versus 2%; P <0.0001) and improvement of progression-free survival (PFS) (30.2 versus 21.2 months; P = 0.01) as well as overall survival (OS) (median 54.9 versus 49.4 months; P = 0.048). According to the chromosome 13q14 status as determined by fluorescence in situ hybridization and serum levels of beta(2)-microglobulin (beta(2)M), MM patients were separated into a standard-risk group (normal chromosome 13q14 and beta(2)M 4 mg/l). Among patients of the high-risk group, both PFS (26.4 versus 10.7 months; P = 0.004) and OS times (40 versus 23 months; P = 0.05) were longer in patients receiving HDT compared with patients treated by SDT. In the standard-risk group, PFS and OS times were not significantly different between HDT patients and SDT patients. Results of this retrospective analysis suggest that the beneficial effects of HDT are greater in MM patients with high-risk features than in patients with absence of such poor prognostic indicators.

Low dose thalidomide in patients with relapsed or refractory multiple myeloma.

Remarkable results of the treatment of refractory multiple myeloma with thalidomide have been reported. In most preceding studies, the given thalidomide dose was escalated to a maximum tolerated dose of up to 800 mg/d. The frequency of adverse effects correlates with dose intensity. Since a significant gain of therapeutic effects could not be observed as thalidomide dosage was escalated, the optimal dose of thalidomide remains to be determined. We report the results of a study with low dose thalidomide (median administered dose 100 mg/d, range 50-400 mg/d). Twenty-four relapsed (n = 19) or resistant (n = 5) multiple myeloma patients were included in the study. Twelve patients (50%) received thalidomide as monotherapy, 8 patients (33%) received a combination of thalidomide and dexamethasone (every 4 weeks 40 mg/day for 4 days) and 4 patients (17%) who were resistant to vincristine, doxorubicin, dexamethasone (VAD) received VAD combined with thalidomide. Overall, a response was observed in 12 patients (50%). Of the 12 patients treated with low dose thalidomide alone 5 (42%) responded, of the 8 patients who received a combination of thalidomide and dexamethasone 5 (63%) responded and of the 4 patients who had thalidomide in addition to VAD 2 patients (50%) responded. In 3 patients, thalidomide treatment had to be discontinued because of side effects and 1 patient died before response could be assessed. We conclude that low dose thalidomide is an effective and safe rescue therapy in relapsing or refractory multiple myeloma. Response to thalidomide might be dependent on prognostic parameters and tumor burden. To answer these questions larger prospective studies are necessary.

Serum tryptase measurements in patients with myelodysplastic syndromes.

Abnormal differentiation and maturation of hemopoietic cells are characteristic features of myelodysplastic syndromes (MDS). Tryptases (alpha- and beta-type) are lineage-restricted serine proteases primarily expressed in mast cells (MC). We have analyzed expression of tryptase in 89 de novo MDS patients (refractory anemia (RA), n = 30; RA with ringed sideroblasts (RARS), n = 21; RA with excess of blasts (RAEB/RAEB-t), n = 27; chronic myelomonocytic leukemia (CMML), n = 11). Serum levels of total tryptase (alpha - protryptase + beta - tryptase) were measured by FIA. The numbers of tryptase+ cells were determined in paraffin-embedded bone marrow (bm) sections by immunohistochemistry and morphometry. In healthy individuals, serum total tryptase levels ranged between < 1 and 15 ng/ml (5.6 +/- 2.8 ng/ml). Tryptase levels of > 20 ng/ml were detected in 5/22 patients with RA (22.7%), 4/17 with RARS (23.5%), 0/16 with RAEB/RAEB-t, and 3/8 with CMML (37.5%). Thus, serum tryptase concentrations were higher in RA (16.6 +/- 14.3 ng/ml), RARS (12.9 +/- 8.2), and CMML (16.5 +/- 7.6) compared to RAEB/-t (8.7 +/- 3.8). By morphometry, elevated numbers of tryptase+ bm cells were detected in all MDS groups (RA: 139 +/- 131; RARS: 118 +/- 98; RAEB/RAEB-t: 80 +/- 79; CMML: 105 +/- 114 cells/mm2) compared to controls (54 +/- 51 cells/mm2). As assessed by Northern blotting and protein analysis, bm cells in MDS primarily produced alpha-(pro)tryptase, but little or no beta-tryptase. Together, our data show that elevated levels of tryptase are detectable in a group of patients with MDS probably because of an increase in neoplastic (mast) cells producing the enzyme(s). In addition, serum tryptase levels appear to correlate with MDS variants. Follow up studies should clarify whether an elevated tryptase concentration in MDS is of prognostic significance.