Management of proximal metaphyseal curvilinear tibial fractures in 25 skeletally immature dogs (2009 to 2020).

OBJECTIVES: To describe the occurrence, management and outcome of proximal metaphyseal curvilinear tibial fractures in skeletally immature dogs. MATERIALS AND METHODS: A multi-centre retrospective review was conducted, searching for skeletally immature dogs presenting with proximal metaphyseal curvilinear tibial fractures between January 2009 and September 2020. Signalment, fracture description and case management data were retrieved. Outcome was assessed by retrospectively evaluating follow-up radiographs, hospital records and an owner questionnaire. RESULTS: Twenty-five dogs met the inclusion criteria. All but one fracture was a result of minimal trauma. Twenty fractures were managed with internal fixation, two with external fixation and three conservatively. All 25 fractures healed. Eight major complications occurred in seven of 25 (28%) dogs. Twelve minor complications occurred in 10 of 25 (40%) dogs. Owner questionnaire data were available for 12 of 25 dogs; 11 of 12 were reported as having full function and one of 12 as having acceptable function at the time of questioning (median 34.5 months following presentation). At final follow-up, either by clinical examination or owner questionnaire, full function was achieved in 22 of 25 patients and acceptable function in three of 25. CLINICAL SIGNIFICANCE: This study reported a series of proximal metaphyseal tibial fractures in skeletally immature dogs. The most common fixation method was internal fixation, which frequently resulted in full limb function at final follow-up. Owners reported outcome as fully functional in all dogs that underwent surgery at first presentation and had owner follow-up available, though positive outcomes may have been affected by participation bias.

Retrospective study of complications associated with surgically-placed gastrostomy tubes in 43 dogs with septic peritonitis.

OBJECTIVES: To determine the safety of surgically-placed gastrostomy feeding tubes in dogs with septic peritonitis. MATERIALS AND METHODS: Retrospective analysis of 43 dogs with septic peritonitis that had undergone surgical exploration and gastrostomy tube (de Pezzer or Foley) placement as part of the surgical procedure. Postoperative recovery times, hospitalisation times, complication rates and overall survival times were documented. RESULTS: The most common cause of septic peritonitis was dehiscence of an enterotomy or enterectomy site. Fifteen dogs had a Foley gastrostomy tube placed and 28 had a de Pezzer gastrostomy tube placed. The median time from surgery to the start of enteral nutrition was 16 hours (range 3 to 28 hours). There were no major complications relating to the gastrostomy tube; minor complications occurred in 11 (26%) patients. The overall median time spent in hospital was 5 days (range 3 to 29 days) for patients surviving to discharge and 22 (51%) dogs survived overall. CLINICAL SIGNIFICANCE: Gastrostomy feeding tubes provide a safe way to provide enteral nutrition to dogs with septic peritonitis; they are associated with a low complication rate in these patients.

Modified tube gastropexy using a mushroom-tipped silicone catheter for management of gastric dilatation-volvulus in dogs.

OBJECTIVES: To report the short- and long-term complications and clinical outcomes of a cohort of dogs managed for gastric dilatation-volvulus using a modified right-sided tube gastropexy technique. MATERIALS AND METHODS: Retrospective case series. RESULTS: Of 31 dogs treated, 29 (93·5%) had an excellent short-term outcome, and gastric dilatation-volvulus did not recur in any dog. Twenty-six dogs (84%) were initially fed via the gastrostomy tube postoperatively; three (9·7%) suffered a major complication including septic peritonitis (n=1), and premature tube removal (n=2). Fourteen dogs (45·1%) had minor complications including mild, self-limiting discharge from the stoma site in 13. CLINICAL SIGNIFICANCE: Modified tube gastropexy using a mushroom-tipped silicone catheter is an effective and safe surgical method for the management of gastric dilatation-volvulus. The gastrostomy tube allowed early enteral feeding and easy administration of medications, including gastroprotectants.

Comparison of the use of LigaSure versus a standard technique for tonsillectomy in dogs.

The principal aim of this study was to document the effectiveness of tonsillectomy in dogs using a vessel-sealing device compared with a standard technique with tonsillectomy forceps. A secondary aim of the study was to document histopathological changes of the excised tonsillar tissue in dogs with brachycephalic obstructive airway syndrome. 20 dogs were studied. The time taken to remove a tonsil using LigaSure was a mean of 44.8 seconds (sd 15 seconds, 95 per cent CI 40  to 57 seconds) and with the standard technique a mean of 305.9 seconds (sd 67 seconds, 95 per cent CI 272  to 349 seconds). Significantly less haemorrhage occurred using LigaSure compared with the standard technique. Histopathology of the tonsils was characterised by multifocal neutrophilic and lymphocytic inflammation, and 1-2 mm of heat-induced coagulation necrosis at the cut edge of LigaSure tonsils. This study shows that LigaSure is significantly faster and resulted in less bleeding than the standard technique.

Cost-effectiveness of lenalidomide plus dexamethasone vs. bortezomib plus melphalan and prednisone in transplant-ineligible U.S. patients with newly-diagnosed multiple myeloma.

OBJECTIVE: To conduct a cost-effectiveness assessment of lenalidomide plus dexamethasone (Rd) vs bortezomib plus melphalan and prednisone (VMP) as initial treatment for transplant-ineligible patients with newly-diagnosed multiple myeloma (MM), from a U.S. payer perspective. METHODS: A partitioned survival model was developed to estimate expected life-years (LYs), quality-adjusted LYs (QALYs), direct costs and incremental costs per QALY and LY gained associated with use of Rd vs VMP over a patient's lifetime. Information on the efficacy and safety of Rd and VMP was based on data from multinational phase III clinical trials and a network meta-analysis. Pre-progression direct costs included the costs of Rd and VMP, treatment of adverse events (including prophylaxis) and routine care and monitoring associated with MM. Post-progression direct costs included costs of subsequent treatment(s) and routine care and monitoring for progressive disease, all obtained from published literature and estimated from a U.S. payer perspective. Utilities were obtained from the aforementioned trials. Costs and outcomes were discounted at 3% annually. RESULTS: Relative to VMP, use of Rd was expected to result in an additional 2.22 LYs and 1.47 QALYs (discounted). Patients initiated with Rd were expected to incur an additional $78,977 in mean lifetime direct costs (discounted) vs those initiated with VMP. The incremental costs per QALY and per LY gained with Rd vs VMP were $53,826 and $35,552, respectively. In sensitivity analyses, results were found to be most sensitive to differences in survival associated with Rd vs VMP, the cost of lenalidomide and the discount rate applied to effectiveness outcomes. CONCLUSIONS: Rd was expected to result in greater LYs and QALYs compared with VMP, with similar overall costs per LY for each regimen. Results of this analysis indicated that Rd may be a cost-effective alternative to VMP as initial treatment for transplant-ineligible patients with MM, with an incremental cost-effectiveness ratio well within the levels for recent advancements in oncology.

Stifle arthrodesis in two cats.

Two Domestic Shorthaired cats were admitted after sustaining multiligamentous injuries of the stifle joint. In one cat, prosthetic ligamentous reconstruction was unsuccessful at maintaining normal stifle stability. Both cats were treated with stifle arthrodesis using internal fixation with a plate and screws without external coaptation. In one case, arthrodesis was achieved using a 2.7 mm 16-hole dynamic compression plate placed medially. In the second case, a 2.7 mm 14-hole dynamic compression plate was placed cranially. No major complications were noted, and both cats were able to return to good levels of activity in the medium term.

Prevention of thalidomide- and lenalidomide-associated thrombosis in myeloma.

The incidence of venous thromboembolism (VTE) is more than 1 per thousand annually in the general population and increases further in cancer patients. The risk of VTE is higher in multiple myeloma (MM) patients who receive thalidomide or lenalidomide, especially in combination with dexamethasone or chemotherapy. Various VTE prophylaxis strategies, such as low-molecular-weight heparin (LMWH), warfarin or aspirin, have been investigated in small, uncontrolled clinical studies. This manuscript summarizes the available evidence and recommends a prophylaxis strategy according to a risk-assessment model. Individual risk factors for thrombosis associated with thalidomide/lenalidomide-based therapy include age, history of VTE, central venous catheter, comorbidities (infections, diabetes, cardiac disease), immobilization, surgery and inherited thrombophilia. Myeloma-related risk factors include diagnosis and hyperviscosity. VTE is very high in patients who receive high-dose dexamethasone, doxorubicin or multiagent chemotherapy in combination with thalidomide or lenalidomide, but not with bortezomib. The panel recommends aspirin for patients with < or = 1 risk factor for VTE. LMWH (equivalent to enoxaparin 40 mg per day) is recommended for those with two or more individual/myeloma-related risk factors. LMWH is also recommended for all patients receiving concurrent high-dose dexamethasone or doxorubicin. Full-dose warfarin targeting a therapeutic INR of 2-3 is an alternative to LMWH, although there are limited data in the literature with this strategy. In the absence of clear data from randomized studies as a foundation for recommendations, many of the following proposed strategies are the results of common sense or derive from the extrapolation of data from many studies not specifically designed to answer these questions. Further investigation is needed to define the best VTE prophylaxis.

Detection of genes with moderate effects on disease resistance using ovine mhc and resistance to nematodes as an example.

Detecting some of the genes that influence disease resistance would improve our understanding of the processes that cause disease and also simplify disease control. Genes within the major histocompatibility complex (mhc) are strong candidates for disease resistance and they have been intensely studied for the last 30 years. Recently, several groups working independently have reported the existence of alleles within the mhc that are associated with enhanced resistance to nematode infection. This article uses hindsight to describe some of the potential pitfalls that hinder the search for valid disease resistance genes. The search requires a good understanding of disease biology, molecular genetics, statistical genetics and especially, the design and analysis of experiments. The power to detect mhc effects is quite low and is quite sensitive to the frequency of the putative resistance alleles.

A phase II study of bortezomib in mantle cell lymphoma: the National Cancer Institute of Canada Clinical Trials Group trial IND.150.

BACKGROUND: We evaluated the activity and toxic effects of bortezomib in patients with mantle cell lymphoma. PATIENTS AND METHODS: Thirty patients, including 29 eligible patients, were enrolled; 13 had received no prior chemotherapy. The dose of bortezomib was 1.3 mg/m2 given on days 1, 4, 8 and 11 every 21 days. Response was assessed according to the International Workshop Criteria for non-Hodgkin's lymphoma and toxicity graded using the National Cancer Institute Common Toxicity Criteria version 2.0. RESULTS: There were 13 responding patients (46.4%; 95% confidence interval=27.5% to 66.1%), including one unconfirmed complete remission. The median response duration was 10 months. Response rates were similar in previously untreated (46.2%) and treated (46.7%) patients. Neurological toxicity and myalgia led to treatment discontinuation in 10 patients after two to seven treatment cycles. Five serious adverse events (including two deaths) associated with fluid retention were observed in the first 12 patients. We subsequently excluded patients with baseline effusions, dyspnea or edema; no further events were seen. CONCLUSIONS: Bortezomib is active in treating patients with mantle cell lymphoma. While cumulative neuromuscular toxic effects limited therapy duration and specific issues related to fluid retention require further evaluation, continued study of this drug in combination regimens is warranted.

Liposomal encapsulated doxorubicin (Caelyx) in the treatment of relapsed aggressive non-Hodgkin's lymphoma: a phase II study.

Aggressive non-Hodgkin's lymphoma (NHL), such as diffuse large B-cell lymphoma, can be cured in approximately 50% of cases, but those cases that recur and are not amenable to high-dose chemotherapy rely on palliative chemotherapy to improve symptoms and prolong life. Anthracyclines are associated with a high response rate in aggressive NHL but extended treatment results in cardiotoxicity. Liposomal encapsulated doxorubicin has been shown in other tumor types to allow for extended treatment with doxorubicin, but is associated with a low cardiac risk. The present study aimed to assess the response rate, survival and cardiac risk of patients with relapsed aggressive NHL treated with liposomal encapsulated doxorubicin. Eighteen patients with relapsed aggressive NHL were treated with liposomal encapsulated doxorubicin (40 - 50 mg/m2) for a planned six cycles. Some 83% of patients had diffuse large B-cell or mantle cell NHL. Four patients had a partial response (23%), whereas five patients had stable disease. None had a complete response. Eight patients progressed when receiving the liposomal encapsulated doxorubicin therapy. The median survival time was 34 weeks, and the median progression-free survival was 15.7 weeks. Overall survival was 50% at 6 months and 39% at 12 months. Progression-free survival was 33% at 6 months and was 28% at 12 months. The mean ejection fraction pre- and post-liposomal encapsulated doxorubicin treatment remained the same. Only one patient had a drop in ejection fraction to <50%. Liposomal encapsulated doxorubicin offers another choice to patients seeking palliation from their lymphoma recurrence with a response rate of 23% that was well tolerated and had a minimal cardiotoxic risk.

International uniform response criteria for multiple myeloma.

New uniform response criteria are required to adequately assess clinical outcomes in myeloma. The European Group for Blood and Bone Marrow Transplant/International Bone Marrow Transplant Registry criteria have been expanded, clarified and updated to provide a new comprehensive evaluation system. Categories for stringent complete response and very good partial response are added. The serum free light-chain assay is included to allow evaluation of patients with oligo-secretory disease. Inconsistencies in prior criteria are clarified making confirmation of response and disease progression easier to perform. Emphasis is placed upon time to event and duration of response as critical end points. The requirements necessary to use overall survival duration as the ultimate end point are discussed. It is anticipated that the International Response Criteria for multiple myeloma will be widely used in future clinical trials of myeloma.

Gemcitabine, dexamethasone and cisplatin is an active and non-toxic chemotherapy regimen in relapsed or refractory Hodgkin's disease: a phase II study by the National Cancer Institute of Canada Clinical Trials Group.

BACKGROUND: Gemcitabine (difluorodeoxycytidine) is active as a single agent in Hodgkin's disease and has been used successfully in combination with cisplatin to treat a variety of solid tumors. PATIENTS AND METHODS: We evaluated the combination of gemcitabine/dexamethasone/cisplatin (GDP) as salvage chemotherapy in 23 patients with relapsed or refractory Hodgkin's disease (median age 36 years, range 19-57). Treatment consisted of gemcitabine 1000 mg/m(2) intravenously on days 1 and 8, dexamethasone 40 mg orally days 1-4 and cisplatin 75 mg/m(2) on day 1, every 21 days as an outpatient. Response was assessed following two cycles of treatment. RESULTS: There were four complete responses and 12 partial responses for a response rate of 69.5% (95% confidence interval 52% to 87%); the remaining seven patients had stable disease and no patient progressed on treatment. All patients had successful stem cell mobilization and underwent transplantation with a median 10.6 x 10(6) CD34+ cells/kg. Hematological toxicity from GDP was mild (grade 3 neutropenia 8.6%, grade 3 thrombocytopenia 13%). CONCLUSIONS: In summary, GDP is an active regimen for patients with relapsed or refractory Hodgkin's disease. The response rate is similar to the rates of other current salvage regimens, it can be given to outpatients with tolerable toxicity and it does not inhibit the mobilization of autologous stem cells.

Optimising parameters for peripheral blood leukapheresis after r-metHuG-CSF (filgrastim) and r-metHuSCF (ancestim) in patients with multiple myeloma: a temporal analysis of CD34(+) absolute counts and subsets.

Patients (n = 69) with multiple myeloma undergoing peripheral blood stem cell collection (PBSC) were treated with cyclophosphamide and a combination of recombinant methionyl human granulocyte colony-stimulating factor (r-metHuG-CSF, filgrastim) and recombinant methionyl human stem cell factor (r-metHuSCF, ancestim). The objectives of this study were to determine: (1) The proportion of patients reaching a target yield of >or=5 x 10(6) CD34(+) cells/kg in one or two successive large-volume (20 liter) leukapheresis procedures; (2) the optimal collection time for leukapheresis; (3) mobilization kinetics of CD34(+) subsets in response to G-CSF/SCF. All patients were mobilized with cyclophosphamide (2.5 g/m(2)) on day 0 followed by filgrastim (10 microg/kg ) plus ancestim (20 microg/kg) commencing day 1 and continuing to day 11 or 12. Of the 65 evaluable patients, 57 were considered not heavily pretreated and 96.5% obtained a target of >or=5 x 10(6)/kg in one collection. The median CD34(+) cells/kg was 39.5 x 10(6) (range: 5.2-221.2 x 10(6)). Subset analysis demonstrated the number of CD38(-), CD33(-), and CD133(+) peaked at day 11; and CD34(+), CD90(+) cells peaked at day 10. The optimum day for leukapheresis was determined to be day 11. The median absolute peripheral blood CD34(+) cell numbers on day 11 was 665 x 10(6)/l (range: 76-1481 x 10(6)/l). Eight of the 10 heavily pretreated patients were evaluable: three achieved the target dose in one leukapheresis (37.5%) and three (37.5%) achieved the target dose with two leukaphereses. Use of this mobilization strategy allowed the collection of high numbers of CD34(+) cells and early progenitors and the ability to predictably schedule leukapheresis.

Zoledronic acid versus pamidronate in the treatment of skeletal metastases in patients with breast cancer or osteolytic lesions of multiple myeloma: a phase III, double-blind, comparative trial.

PURPOSE: Zoledronic acid, a new and more potent bisphosphonate, was compared with pamidronate, the current standard treatment for patients with osteolytic or mixed bone metastases/lesions. PATIENTS AND METHODS: A total of 1,648 patients with either Durie-Salmon stage III multiple myeloma or advanced breast cancer and at least one bone lesion were randomly assigned to treatment with either 4 or 8 mg of zoledronic acid via 15-minute intravenous infusion or 90 mg of pamidronate via 2-hour intravenous infusion every 3 to 4 weeks for 12 months. The primary efficacy endpoint was the proportion of patients experiencing at least one skeletal-related event over 13 months. RESULTS: The proportion of patients with at least one skeletal-related event was similar in all treatment groups. Median time to the first skeletal-related eventwas approximately 1 year in each treatment group. The skeletal morbidity rate was slightly lower in patients treated with zoledronic acid than in those treated with pamidronate, and zoledronic acid (4 mg) significantly decreased the incidence and event rate for radiation therapy to bone, both overall and in breast cancer patients receiving hormonal therapy. Pain scores decreased in all treatment groups in the presence of stable or decreased analgesic use. Zoledronic acid (4 mg) and pamidronate were equally well tolerated; the most common adverse events were bone pain, nausea, fatigue, and fever and < 5% of serious adverse events were related to the study drug. The incidence of renal impairment among patients treated with 4 mg of zoledronic acid via 15-minute infusion was similar to that among patients treated with pamidronate. CONCLUSIONS: Zoledronic acid (4 mg) via 15-minute intravenous infusion was as effective and well tolerated as 90 mg of pamidronate in the treatment of osteolytic and mixed bone metastases/lesions in patients with advanced breast cancer or multiple myeloma. (Can-

Persistent preswitch clonotypic myeloma cells correlate with decreased survival: evidence for isotype switching within the myeloma clone.

Multiple myeloma (MM) is identified by unique immunoglobulin heavy chain (IgH) variable diversity joining region gene rearrangements, termed clonotypic, and an M protein termed the "clinical" isotype. Transcripts encoding clonotypic pre and postswitch IgH isotypes were identified in MM peripheral blood mononuclear cells (PBMCs), bone marrow (BM), and mobilized blood. For 29 patients, 38 BM, 17 mobilized blood, and 334 sequential PBMC samples were analyzed at diagnosis, before and after transplantation for 2 to 107 months. The clinical clonotypic isotype was readily detectable and persisted throughout treatment. Eighty-two percent of BM and 38% of PBMC samples also expressed nonclinical clonotypic isotypes. Clonotypic immunoglobulin M (IgM) was detectable in 68% of BM and 25% of PBMC samples. Nonclinical clonotypic isotypes were detected in 41% of mobilized blood samples, but clonotypic IgM was detected in only 12%. Patients with persistent clonotypic IgM expression had adverse prognostic features at diagnosis (lower hemoglobin, higher beta(2)-microglobulin) and higher numbers of BM plasma cells compared with patients with infrequent/absent clonotypic IgM. Patients with persistent clonotypic IgM expression had significantly poorer survival than patients with infrequent IgM expression (P <.0001). In a multivariate analysis, persistent clonotypic IgM expression in the blood correlated independently with poor survival (P =.01). In nonobese diabetic severe combined immunodeficiency mice, xenografted MM cells expressed clinical and nonclinical postswitch clonotypic isotypes. MM expressing clonotypic IgM engrafted both primary and secondary mice, indicating their persistence within the murine BM. This study demonstrates that MM clonotypic cells expressing preswitch transcripts are tied to disease burden and outcomes. Because MM pathology involves postswitch plasma cells, this raises the possibility that IgH isotype switching in MM may accompany worsening disease.

Expression of IL-6 and IL-6 receptors by circulating clonotypic B cells in multiple myeloma: potential for autocrine and paracrine networks.

OBJECTIVE: To investigate the participation of clonotypic MM B cells in the IL-6 network in patients with multiple myeloma. METHODS: CD19(+) B cells from 45 patients with multiple myeloma and from 18 healthy donors were sorted and their expression of IL-6, IL-6 receptor (CD126) characterized by flow cytometry, in situ RT-PCR, and ELISA measurement of IL-6 and soluble IL-6R. Expression of CD31 was detected by flow cytometry. RESULTS: Interleukin-6 (IL-6) is a pleiotropic cytokine often overexpressed in multiple myeloma (MM). IL-6 induces growth and inhibits apoptosis of MM plasma cells, and upregulates the activity of osteoclasts. MM plasma cells, the most mature component of the MM clone, secrete IL-6 and induce IL-6 production from other cell types. However, the MM clone also includes circulating clonotypic B lymphocytes. Using ELISA and in situ RT-PCR we demonstrate here that, unlike the healthy control B cells, MM B cells express IL-6 mRNA and secrete IL-6 protein. In vitro, MM B cells were the major producers of IL-6 in peripheral blood mononuclear cells. On average, 50% of MM B cells express the IL-6 receptor (IL-6R, CD126), suggestive of autocrine stimulation. They also express CD31, potentially facilitating their paracrine interactions with osteoclast precursors. CONCLUSION: Secretion of IL-6 by circulating clonotypic B cells in MM may contribute to the autocrine and paracrine cytokine networks that maintain the malignant clone and are responsible for disruption of normal bone metabolism in this incurable disease.

Elevated soluble MUC1 levels and decreased anti-MUC1 antibody levels in patients with multiple myeloma.

Soluble MUC1 (sMUC1) levels are elevated in many MUC1(+) cancers. We and others have shown that MUC1 is expressed on multiple myeloma (MM) plasma cells and B cells. In this study, we measured sMUC1 levels in bone marrow (BM) plasma from 71 MM patients and 21 healthy donors (HDs), and in peripheral blood (PB) plasma from 42 MM patients and 13 HDs using an immunoassay that detects the CA27.29 epitope of MUC1. sMUC1 levels were found to be significantly greater (mean 31.76 U/mL, range 5.69 to 142.48 U/mL) in MM patient BM plasma versus HD BM plasma (mean 9.68 U/mL, range 0.65 to 39.83 U/mL) (P <. 001). Importantly, BM plasma sMUC1 levels were related to tumor burden because sMUC1 levels were significantly higher for MM patients with active disease (34.62 U/mL, range 5.69 to 142.48 U/mL) versus MM patients with minimal residual disease (16.16 U/mL, range 5.7 to 56.68 U/mL) (P =.0026). sMUC1 levels were also elevated in the PB plasma of MM patients (32.79 U/mL, range 4.15 to 148.84 U/mL) versus HDs (18.47 U/mL, range 8.84 to 42.49) (P =.0052). Lastly, circulating immunglobulin M (IgM) and IgG antibodies to MUC1 were measured in 114 MM patients and 31 HDs, because natural antibodies to MUC1 have been detected in patients with other MUC1-bearing malignancies. These studies demonstrated lower levels of circulating IgM (P <.001) and IgG (P =.078) antibodies to MUC1 in MM patients compared with HDs. Our data therefore show that in MM patients, sMUC1 levels are elevated and correlate with disease burden, whereas anti-MUC1 antibody levels are decreased.

Selective targeting of immunoliposomal doxorubicin against human multiple myeloma in vitro and ex vivo.

Circulating malignant CD19(+) B cells have been implicated in the pathogenesis and relapse of multiple myeloma (MM). This study investigated the therapeutic applicability of using long-circulating liposome-encapsulated doxorubicin (DXR) targeted against the internalizing CD19 antigens present on human MM cells. In vitro binding studies using the CD19(+) MM cell line ARH77 demonstrated that CD19-directed immunoliposomes (SIL[anti-CD19]) specifically attached to these cells. Formulations of immunoliposomal doxorubicin (DXR-SIL[anti-CD19]) showed a higher association with, and higher cytotoxicity against, ARH77 cells than did non-targeted liposomal doxorubicin (DXR-SL) or isotype-matched controls (DXR-NSIL[IgG2a]). By using the pH-sensitive fluorophore, 1-hydroxypyrene-3,6, 8-trisulfonic acid, binding of SIL[anti-CD19] to CD19 antigens was shown to trigger receptor-mediated internalization of the antibody-antigen complexes into endosomes. Targeting of SIL[anti-CD19] to CD19(+) B cells was also demonstrated in a heterogeneous mixture of peripheral blood mononuclear cells (PBMC) from MM patients. A decrease in cellular DNA (which is an indicator of apoptosis) caused by the cytotoxicity of DXR-SIL[anti-CD19] to myeloma PBMC was determined by using flow cytometry. While PBMC treatment with free DXR resulted in non-specific cytotoxicity to both B and T cells, DXR-SL were only minimally cytotoxic to either. In contrast, DXR-SIL[anti-CD19] were selectively cytotoxic for B cells in PBMC, indicating that this treatment may be effective in eliminating circulating malignant B cells in MM patients.

Treatment of multiple myeloma by antibody mediated immunotherapy and induction of myeloma selective antigens.

BACKGROUND: In view of the successful use of serotherapy in many B-cell malignancies, we and others have sought to identify tumor selective antigens for the serotherapy of plasma cell dyscrasias (PCD) including multiple myeloma (MM), and Waldenstrom's macroglobulinemia (WM). We recently identified Muc-1 core protein as a MM selective antigen. Though Muc-1 core protein is abundantly expressed on most MM plasma cells, expression of this antigen can be absent, or weak on some plasma cells which could potentially result in the selection of Muc-1 core protein negative clones following serotherapy of PCD. In addition to Muc-1 core protein, we have also been examining the use of CD20 directed serotherapy for PCD. DESIGN: As part of these efforts, we recently initiated a phase II clinical trial examining the use of Rituximab (Rituxan, MabThera) as a single agent in MM patients; as well several WM patients have been treated with Rituximab at our Institutions. RESULTS: In previous studies, we have shown that CD20 is abundantly expressed on the plasma cells of most WM patients; in contrast, CD20 is expressed on plasma cells from a minority of MM patients, and in these patients expression of CD20 can be weak or heterogeneous with both CD20+ and CD20- plasma cells present. As such, we have sought out clinically useful inducers of Muc-1 core protein, and of CD20 on malignant plasma cells. CONCLUSIONS: These efforts resulted in the identification of dexamethasone (Dex) as a potent inducer of Muc-1 core protein on MM plasma cells, and interferon-gamma (IFN-gamma) as a potent inducer of CD20 on MM plasma cells and B-cells. Importantly, these agents induced their respective antigens at pharmacologically achievable doses.