Association of a bovine CXCR2 gene polymorphism with neutrophil survival and killing ability.

Recent research in our lab has demonstrated a significant association between the incidence of subclinical mastitis and specific polymorphisms of the CXCR2 gene in Holstein dairy cows. This gene encodes a receptor for interleukin-8 (IL-8), a key regulator of neutrophil migration, killing and survival. Because of the importance of this gene in neutrophil function, we hypothesized that differences in neutrophil killing and survival may exist among the CXCR2 genotypes and potentially contribute to the observed variation in intramammary infections. To test this hypothesis, neutrophils were isolated from cows representing each CXCR2 +777 genotype (GG, GC or CC) and tested for suppression of apoptosis, reactive oxygen species (ROS) generation, glutathione levels, and bactericidal activity. A significant increase in survival was observed in neutrophils from cows with a CC genotype when compared to those with a GG genotype in response to IL-8, but not dexamethasone. In contrast, a significant reduction in neutrophil ROS generation in response to phorbol-13-myristate-12 acetate (PMA) was observed in cows with a CC genotype when compared to those with a GG genotype. However, no differences in bactericidal activity or glutathione levels were observed among genotypes. The functional activity of neutrophils from cows heterozygous for this polymorphism was intermediate between those with homozygous genotypes for those assays where differences were observed among homozygous genotypes. In summary, our results suggest that neutrophils from Holstein cows with different CXCR2 genotypes vary in their ability to suppress apoptosis and produce ROS. These differences have the potential to influence overall neutrophil function and may partially explain the variation observed with respect to mastitis in vivo. These results provide a foundation for future research aimed at better understanding the basic differences between dairy cows genetically more or less susceptible to mastitis and has the potential to provide novel preventive and therapeutic measures against inflammatory diseases such as mastitis.

Allogeneic marrow transplantation for chronic granulocytic leukemia.

A retrospective analysis is presented of results obtained with allogeneic bone marrow transplantation (BMT) in three phases of Philadelphia chromosome-positive chronic granulocytic leukemia. At BMT, 23 patients were in blastic phase (BP), 33 were in accelerated phase (AP), and 45 were in chronic phase (CP). With a follow-up time of 1-8 years after BMT, the probability of long-term survival was 14, 10, and 58%, respectively, for patients transplanted in BP, AP, or CP. The probability of cytogenetic relapse with or without clinical hematologic relapse at 3 years after BMT was 80, 38, and 31%, respectively, for patients transplanted in BP, AP, or CP. Splenectomy did not influence posttransplant survival. Given the dismal prognosis on conventional therapy, patients younger than 50 in BP or AP should be considered for BMT. For the patient in CP, BMT offers the possibility of cure but with a significant risk of early death. Patients under 40 who fully understand the risks and potential benefits of BMT should be offered BMT early in CP before any change to AP occurs.

High-dose cyclophosphamide, carmustine, and etoposide followed by autologous bone marrow transplantation in patients with lymphoid malignancies who have received dose-limiting radiation therapy.

PURPOSE: To evaluate high-dose chemotherapy followed by autologous bone marrow transplantation (ABMT) in patients with lymphoid malignancy who had received prior radiation therapy. PATIENTS AND METHODS: Fifty-seven patients with non-Hodgkin's lymphoma (NHL; n = 23), Hodgkin's disease (HD, n = 32), or acute lymphoblastic leukemia (ALL; n = 2) with a history of previous radiation therapy were treated with cyclophosphamide (Cy; 7.2 g/m2), carmustine (300 mg/m2 or 600 mg/m2), and etoposide (2,400 mg/m2) (CBV) followed by ABMT. RESULTS: The projected 2-year probabilities of survival, event-free survival (EFS), and relapse were .31, .24, and .76, respectively. For patients with intermediate- and high-grade lymphoma and HD the probabilities were .27, .10, and .14 for EFS and .57, .90, and .77 for relapse. The probability of nonrelapse mortality in the first 100 days post-ABMT was 33%. Idiopathic pneumonia syndrome (IPS) was observed in no patients who received carmustine 300 mg/m2 and 23% of patients who received carmustine 600 mg/m2 (P = .05). Eight-three percent of patients who received mediastinal radiation therapy less than 3 months before transplant developed IPS, compared with 13% who received radiation therapy more than 3 months before transplant (P = .001). CONCLUSION: ABMT following high-dose CBV resulted in long-term disease-free survival in 25% of patients with lymphoid malignancies who had previously received dose-limiting radiation therapy. Fatal IPS and a high relapse rate were major factors limiting successful outcome following ABMT. The morbidity and mortality rates associated with the administration of carmustine 600 mg/m2 were prohibitively high, especially in patients who received mediastinal radiation immediately before ABMT, and were not associated with a decrease in post-ABMT relapse.

Autologous marrow transplantation for patients with acute myeloid leukemia in untreated first relapse or in second complete remission.

PURPOSE: This study compares outcomes of autologous bone marrow transplantation (ABMT) in patients with acute myeloid leukemia (AML) in untreated first relapse (REL1) or in second complete remission (REM2). PATIENTS AND METHODS: Forty-seven patients with AML in REL1 (n = 21) or in REM2 (n = 26) were treated with busulfan (BU) and cyclophosphamide (CY) with or without total-body irradiation (TBI) followed by ABMT. All REL1 patients and four REM2 patients had marrow stored during first remission (REM1). Twenty-seven had marrow stored with and 20 without treatment in vitro with 4-hydroperoxycyclophosphamide (4-HC). Eighteen patients received BU and CY and 29 received BU, CY, and TBI. REL1 patients relapsed within a median of 9 months (range, 2 to 26) after marrow harvest and were transplanted a median of 30 days (range, 9 to 87) from detection of relapse. RESULTS: With a median follow-up of 2.1 years (range, 0.4 to 5.3), 19 patients survive in remission (10 of 21 in REL1; nine of 26 in REM2). The actuarial probabilities of relapse-free survival at 2 years for patients transplanted in REL1 and REM2 were 45% +/- 22% and 32% +/- 18%, respectively (P = .33). The corresponding probabilities of relapse were 30% +/- 26% and 44% +/- 23%, respectively (P = .45). No conclusions could be drawn about the benefits of adding TBI to BU plus CY. There were no significant differences in neutrophil or platelet recovery or in posttransplant probabilities of relapse and nonrelapse mortality between patients who received marrow treated or not treated with 4-HC. CONCLUSION: These results suggest that ABMT may produce long-term leukemia-free survival in approximately one third of patients with AML in REL1 or in REM2. There is no apparent clinical advantage in attempting to obtain second remissions in relapsed patients before ABMT if marrow has been cryopreserved during REM1. Although a strategy of transplantation in REL1 has advantages for the patient, such an approach involves the storage of marrow, which may not be used, and is impractical without the coordinated support of the treating physician, the patient, and the marrow transplant center.

High-dose cyclophosphamide, carmustine, and etoposide followed by allogeneic bone marrow transplantation in patients with lymphoid malignancies who had received prior dose-limiting radiation therapy.

PURPOSE: To evaluate a high-dose chemotherapy regimen without total-body irradiation (TBI) followed by allogeneic (allo) bone marrow transplantation (BMT) in patients with lymphoid malignancies who had received prior dose-limiting radiotherapy. PATIENTS AND METHODS: Fifty-six patients with non-Hodgkin's lymphoma (NHL, n = 26), Hodgkin's disease (HD, n = 17), or acute lymphoblastic leukemia (ALL, n = 13) with a history of previous radiation therapy were treated with cyclophosphamide (7.2 g/m2), carmustine (300 mg/m2 or 600 mg/m2), and etoposide (2,400 mg/m2; CBV) followed by allo BMT. RESULTS: Nine of 56 patients are alive and disease-free a median of 1,091 (range, 512 to 1,784) days post-transplant. The probabilities of transplant-related mortality, relapse, and event-free survival at 2 years for the entire group of 56 patients were .62, .59, and .17, respectively. Patients who received 600 mg/m2 of carmustine had a higher incidence of grade 3 or 4 regimen-related toxicities (RRTs) (14 of 22) than did patients who received 300 mg/m2 (12 of 33; P < .04), whereas there was no difference in relapse (.34 and .53, respectively, P = .73). Fourteen of 16 patients who received allo BMT for advanced disease (n = 12) or less-advanced disease (n = 4) but who were also eligible for auto BMT relapsed (n = 4) or died of transplant-related complications (n = 10). CONCLUSIONS: Allo BMT following a high-dose CBV regimen resulted in long-term disease-free survival in 17% of patients with lymphoid malignancies who had received prior dose-limiting radiotherapy. A high incidence of transplant-related complications, especially fatal idiopathic pneumonia syndrome (IPS) and a high relapse rate limited success. Morbidity and mortality associated with carmustine 600 mg/m2 were high and were not associated with a decrease in relapse. The number of patients in this study eligible for either allo or auto BMT was limited and precluded meaningful analysis of relative effectiveness.

Allogeneic marrow transplantation for myelodysplastic syndrome with advanced disease morphology: a phase II study of busulfan, cyclophosphamide, and total-body irradiation and analysis of prognostic factors.

PURPOSE: To determine if an intensive preparative regimen of busulfan (BU), cyclophosphamide (CY), and total-body irradiation (TBI) could improve outcome after marrow transplantation for advanced morphology myelodysplasia (refractory anemia with excess blasts [RAEB], RAEB in transformation [RAEB-T], and chronic myelomonocytic leukemia [CMML]) compared with that obtained with conventional CY/TBI and to analyze prognostic factors for transplantation for myelodysplasia. PATIENTS AND METHODS: A phase II study was conducted of 31 patients (median age, 41 years) treated with BU (7 mg/kg), CY (50 mg/kg), TBI (12 Gy), and human leukocyte antigen (HLA)-matched (n = 23) or -mismatched (n = 2) related or unrelated donor (n = 6) marrow transplantation. Results were compared with 44 historical control patients treated with CY (120 mg/kg) and TBI. RESULTS: The 3-year actuarial disease-free survival (DFS) rate was similar for the BU/CY/TBI group and the CY/TBI group (23% v 30%, P = .6), but there were trends toward lower relapse rates (28% v 54%, P = .27) and higher nonrelapse mortality rates (68% v 36%, P = .12) among the current patients compared with historical controls. Multivariate analysis showed that a normal karyotype pretransplant and the use of methotrexate as part of posttransplant immunosuppression were associated with improved survival and reduced nonrelapse mortality. Univariate analysis showed significant differences in relapse rates based on marrow source (57% for HLA genotypically matched marrow v 18% for all others, P = .04) and on disease morphology (66% for RAEB-T v 38% for RAEB and CMML, P = .05). CONCLUSION: Patients with advanced morphology myelodysplasia tolerated the intensified BU/CY/TBI preparative regimen and reduced posttransplant immunosuppression poorly. Novel transplant procedures are needed to reduce relapse rates without increasing nonrelapse mortality rates. In addition, transplantation before progression to RAEB-T, if possible, may reduce the risk of relapse.

Allogeneic marrow transplantation during untreated first relapse of acute myeloid leukemia.

PURPOSE: The purpose of this report was to review the Seattle experience in bone marrow transplantation (BMT) for acute myeloid leukemia (AML) during untreated first relapse. PATIENTS AND METHODS: Through 1990, 126 patients were transplanted during untreated first relapse of AML. Several preparative regimens were used, two of which involved more than 20 patients. Regimen 1 (29 patients) consisted of cyclophosphamide (CY) 120 mg/kg and 15.75 Gy of fractionated total-body irradiation (TBI) with methotrexate (MTX) given intermittently during a 102-day period to prevent graft-versus-host disease (GVHD). Regimen 2 (22 patients) consisted of the same CY and TBI treatment and a combination of MTX and cyclosporine (CSP) for GVHD prophylaxis. The remaining 75 patients were treated with 17 other transplant regimens. Outcome was compared for patients who were treated with regimen 1, regimen 2, and any other regimen. RESULTS: The 5-year probabilities of relapse-free survival (RFS), relapse, and nonrelapse mortality for 126 patients were .23, .57, and .44, respectively. With regimen 1, relapse (.26) was significantly less than for regimen 2 (.70; P = .004) or any other regimen (.76; P = .004). Regimen 1 patients developed more acute GVHD (.67) than regimen 2 patients (.26; P = .02) or patients on other regimens (.41; P = .02), and had increased nonrelapse mortality. Nevertheless, regimen 1 patients had a significantly higher 3-year RFS (.38) than those treated with regimen 2 (.18; P = .04) or any other regimen (.20; P = .05). CONCLUSIONS: For patients who received 120 mg/kg CY and 15.75 Gy TBI, relapse incidence was less and survival was better after GVHD prophylaxis with MTX alone than after a combination of MTX and CSP, despite a significantly higher incidence of acute GVHD. The results of treatment with regimen 1 justify future studies of the optimal timing of allogeneic BMT in the treatment of patients with AML.

Effect of different chemotherapy regimens on peripheral-blood stem-cell collections in patients with breast cancer receiving granulocyte colony-stimulating factor.

PURPOSE: To evaluate the effects of chemotherapy regimens on peripheral-blood stem-cell (PBSC) yields in patients with breast cancer who receive granulocyte colony-stimulating factor (G-CSF). PATIENTS AND METHODS: One hundred patients with breast cancer received cyclophosphamide 4 g/m2 for dose (CY) (n = 10), CY and etoposide 600 mg/m2 (CE) (n = 13), CE and cisplatin 105 mg/m2 (CEP) (n = 19), or CY and paclitaxel 170 mg/m2 (n = 58), followed by G-CSF. PBSC collections were initiated when the WBC count recovered to greater than 1 x 10(9)/L. A multivariate analysis was undertaken to evaluate the effects of different chemotherapy regimens and patient variables on PBSC collections as measured by the yield of CD34+ cells. RESULTS: The medians of average daily CD34+ cell yields for patients who received paclitaxel plus CY, CE, and CEP with G-CSF were 12.9, 11.03, and 5.37 x 10(6)/kg, respectively, compared with 2.02 x 10(6)/kg in the reference group that received CY with G-CSF (P = < .0001, .002, and .09, respectively). On first-day collections, patients who received paclitaxel plus CY, CE, and CEP with G-CSF yielded medians of 11.07, 8.09, and 3.52 x 10(6) CD34+ cells/kg, respectively, compared with 0.90 x 10(6)/kg in the reference group that received CY with G-CSF (P = .0006, .02, and .09, respectively). The number of previous cycles of chemotherapy, previous radiotherapy, marrow involvement, and phase and stage of disease did not have statistically significant effects on CD34+ cell yield. CONCLUSION: Combination chemotherapy regimens were superior to single-agent CY for the mobilization of CD34+ cells.

Treatment of malignant lymphoma in 100 patients with chemotherapy, total body irradiation, and marrow transplantation.

Between July 1970 and January 1985, 100 patients with malignant lymphoma were treated with high-dose chemoradiotherapy and bone marrow transplantation. Twenty-eight of the 100 are alive and the actuarial probability of disease-free survival 5 years from transplantation is 22%. The most common reason for treatment failure was disease recurrence, with an actuarial probability of 60%. A proportional hazards regression analysis showed that the likelihood of disease-free survival was less in those patients transplanted in resistant relapse and in those previously treated with chest radiotherapy. Neither disease histology (Hodgkin's disease, high-grade lymphoma or intermediate-grade lymphoma), nor source of marrow (syngeneic, allogeneic, or autologous) significantly influenced either disease-free survival or probability of relapse. The use of high-dose chemoradiotherapy and marrow transplantation appears to offer a better chance for long-term survival than any other form of therapy for young patients with disseminated malignant lymphoma whose disease has progressed after initial combination chemotherapy. The best results with marrow transplantation were obtained in patients transplanted in early relapse or second remission who had not received prior chest radiotherapy.

Regimen-related toxicity in patients undergoing bone marrow transplantation.

Bone marrow transplantation is associated with significant morbidity and mortality, some of which is due to high-dose chemoradiotherapy. In order to quantitate toxicity that was felt to be due to the preparative regimen (termed regimen-related toxicity [RRT]), a system was developed in which toxicities were graded from 0 (none) to 4 (fatal). One hundred ninety-five patients who underwent marrow transplantation for leukemia were studied retrospectively to determine whether toxicities that were clinically felt to be due to the preparative regimen were influenced by other factors such as disease status, graft-versus-host disease (GVHD) prophylaxis, and allogenicity. All patients developed grade I toxicity in at least one organ, and 30 developed grades III-IV (life-threatening or fatal) RRT. RRT was more common in relapsed patients v remission patients (P = .04), in those receiving 15.75 Gy total body irradiation (TBI) v 12.0 Gy TBI (P = .028), and in those receiving allogeneic marrow v autologous marrow (P = .0029). Autologous marrow recipients did not develop grades III-IV toxicity in this study. A multivariate analysis controlling for autologous marrow grafting showed that the dose of TBI was the only statistically significant predictor of grades III-IV RRT. Those patients who developed grade III RRT were unlikely to survive 100 days from transplant, though not all deaths could be attributed to RRT. Patients who developed grade II toxicity in three or more organs were more likely to die within 100 days than those developing grade II toxicity in two or less organs (P = .0027). This system was generally able to distinguish RRT from other toxicities observed in marrow recipients.

Relapse of acute leukemia after marrow transplantation: natural history and results of subsequent therapy.

Of 455 acute nonlymphocytic leukemia (ANL) patients who underwent marrow transplantation, 95 (21%) relapsed a median of 6.5 months posttransplantation and 62 received further treatment. Twenty achieved remission. Success of therapy was related to the length of time from marrow transplant to relapse and to the use of cytarabine (Ara-C) and daunomycin. Aggressive chemotherapy for patients relapsing within 100 days of marrow transplant was associated with a high incidence of early death (six of 14 patients) and a low probability of remission (one of 14). Of 23 patients who relapsed in excess of 1 year from marrow transplant, 15 achieved a complete remission. The median disease-free survival is 6 months (range, 0.4 to 53+ months). Acute lymphocytic leukemia (ALL) recurred in 130 of 366 patients (36%), and 94 received further therapy. Fifty-two achieved a remission. Remissions were more common in late relapse patients (greater than 1 year from transplantation): 65% v 7% for those relapsing within 100 days from transplant (P less than .05). Testicular relapse occurred in 11 patients and was the sole site of relapse in seven. Three are alive and free of disease 58 to 109+ months after relapse. The median survival for the treated patients is 10.5 months (range, 5 to 109+ months). We propose that reinduction be attempted in all patients relapsing greater than 1 year from marrow transplantation. Ara-C and daunomycin should be employed in the treatment of ANL. The decision for treatment of patients relapsing earlier than 1 year should be made on an individual basis.

High-dose cytarabine and total body irradiation with or without cyclophosphamide as a preparative regimen for marrow transplantation for acute leukemia.

Twenty-nine patients were conditioned for allogeneic marrow transplant with cytarabine (ara-C) (3 g/m2 every 12 hours for 12 doses) and total body irradiation (TBI) (200 cGy daily for six days) with or without cyclophosphamide (CY) (60 mg/kg) to determine toxicity and efficacy. Four patients had chronic myelogenous leukemia (CML) in accelerated phase or blast crisis, and 25 patients had acute leukemia, 24 at stages later than first remission. Three patients (10%) had fatal regimen-related toxicity and another 10% experienced severe toxicity in at least one organ system. The addition of CY to the ara-C and TBI regimen was not associated with an increase in the frequency of severe toxicity. Twenty-five of 29 patients engrafted eight to 33 days posttransplant: three died early before engraftment, and one patient failed to engraft. Ten of 29 patients are alive without disease, and the actuarial probability of disease-free survival for the entire group at 3 years is 33%. Three of ten patients with acute nonlymphocytic leukemia (ANL), six of 15 with acute lymphocytic leukemia (ALL), and one of four with CML are alive and disease free 25 to 42 months (median, 30 months) after transplant. High-dose ara-C (HDara-C) and TBI with or without CY can be administered with approximately the same toxicity as CY plus TBI. Phase III studies appear warranted to determine if these newer regimens provide improved results compared with currently used regimens.

Phase I study of busulfan and cyclophosphamide in preparation for allogeneic marrow transplant for patients with multiple myeloma.

PURPOSE: To study the toxicity and potential efficacy of busulfan (BU) and cyclophosphamide (CY) as a conditioning regimen before allogeneic bone marrow transplantation (ABMT) in patients with multiple myeloma (MM). PATIENTS AND METHODS: Twenty patients with MM underwent conditioning, which was followed by ABMT from 16 HLA-identical donors, three one-antigen-mismatched donors, and one HLA A, B, D-identical unrelated donor. Four levels of BU plus CY were evaluated. RESULTS: Severe regimen-related toxicity occurred in two of five patients who received BU 16 mg/kg and CY 120 mg/kg, in none of the four patients who received BU 14 mg/kg and CY 120 mg/kg, in one of eight patients who received BU 14 mg/kg and CY 147 mg/kg, and in two of three patients who received BU 14 mg/kg and CY 174 mg/kg. Twelve of 15 (80%) assessable patients achieved a complete remission with the disappearance of M-protein and the return of normal marrow morphology. Ten patients died of complications related to the ABMT, and two patients died of progressive or relapsed MM. Overall, eight of 20 patients were alive; seven (35%) were in complete remission 190 to 1,271 days after ABMT. CONCLUSIONS: The maximum-tolerable dose given in this setting was BU 14 mg/kg and CY 147 kg/mg. These results suggest that this regimen may have significant antimyeloma activity. Further phase II studies are warranted.

Allogeneic marrow transplantation in the treatment of MOPP-resistant Hodgkin's disease.

Eight patients with disseminated Hodgkin's disease resistant to MOPP (mechlorethamine, vincristine, procarbazine, and prednisone) chemotherapy were treated with high-dose chemoradiotherapy and marrow transplantation from an HLA-identical sibling. Two patients remain alive in unmaintained complete remission (CR) at 38 and 39 months after transplant. In the other six patients, reasons for failure included relapse of lymphoma (two patients), or death due to complications of the transplant procedure, including Legionnaire's disease, disseminated zoster, graft-v-host disease, and aspiration pneumonia secondary to severe mucositis. These results demonstrate that some patients with MOPP-resistant Hodgkin's disease can obtain prolonged CR following intensive chemoradiotherapy and allogeneic marrow transplantation.

High-dose therapy followed by autologous hematopoietic stem-cell infusion for patients with multiple myeloma.

PURPOSE: To evaluate the outcome of patients with multiple myeloma (MM) who received high-dose therapy followed by autologous bone marrow (BM) or peripheral-blood stem-cell (PBSC) infusion. PATIENTS AND METHODS: Sixty-three consecutive patients with MM received autologous BM (n = 13) or PBSC with or without BM (n = 50) following regimens that contained busulfan (Bu) and cyclophosphamide (Cy) (n = 18), modified total-body irradiation (TBI) followed by Bu and Cy (n = 36), or Bu, melphalan, and thiotepa (n = 9). Two thirds of the patients had resistant disease and 69% had received more than 6 months of previous chemotherapy. RESULTS AND CONCLUSION: Recovery of peripheral-blood cell counts was more rapid in patients who received PBSC with or without BM than in patients who received BM alone. Sixteen of 63 patients (25%) died of complications of treatment within 100 days. Nineteen (40%) of 48 assessable patients achieved a complete response (CR), 23 (48%) had a partial response (PR), and six (12%) had no response. The probabilities of survival and survival without relapse or progression for all 63 patients at 3.0 years were .43 and .21, respectively. The probability of relapse or progression at 3 years was .69, and 17 patients (27%) have died of progressive MM. The probabilities of survival and relapse-free survival at 3 years for the 19 patients who achieved a CR were .42 and .17, respectively. In the multivariate analysis, beta2-microglobulin levels more than 2.5 micrograms/mL, more than two regimens of prior therapy and eight cycles of treatment, time to transplant longer than 3 years from diagnosis, and prior radiation were associated with adverse outcomes. Additional strategies, such as intervention earlier in the disease course, improved treatment regimens, sequential high-dose treatments, and posttransplant therapies may improve outcome of selected patients with MM.

Assay for thrombopoietin: a comparison of time of isotope incorporation into platelets and the effects of different strains and sexes of mice.

Several workers have used mice for thrombocytopoiesis-stimulating factor (TSF) assays, but the methods have differed. In quest of the optimum TSF assay conditions, we investigated the effects of interval between isotope injection and measurement of 35S incorporation into platelets, different mouse strains and sexes of mice. The 35S incorporation into platelets of mice increased with increase of the interval after isotope injection. However, the greatest difference in radioactivity between control and TSF-injected mice occurred at 16-40 h for normal mice and 24 h for rebound-thrombocytotic mice. When C3H, BALB/c or B6D2F1 mice were injected with platelet specific antisera, similar degrees of thrombocytopenia and rebound-thrombocytosis occurred. After injection of a standard dose of TSF, C3H and B6D2F1 mice showed greater isotopic incorporation levels, compared to suitable controls, than did BALB/c mice. Female and male mice exhibited essentially the same response to a standard dose of TSF. The data show that the mouse strain and isotopic incorporation time influence the sensitivity of the TSF assay but sex of test animals does not.

Hematologic changes and thrombopoietin production in mice after X-irradiation and platelet-specific antisera.

Sera or plasma thrombopoietin (TSF) levels of mice were determined after: (a) no treatment; (b) induction of thrombocytopenia by injection of rabbit anti-mouse platelet serum (RAMPS); (c) exposure to 750 R or 900 R whole-body x-irradiation; or (d) irradiation and injection with RAMPS. Levels of TSF were assayed in thrombocythemic mice, using Na235SO4 uptake. RAMPS produced an immediate, severe thrombocytopenia without altering RBC or WBC counts of mice. Plasma collected from mice 4 hours after RAMPS injection increased both 35S incorporation into platelets (170% of control, P less than 0.005) and platelet counts (P less than 0.025) of TSF-assay mice. Although severe thrombocytopenia persisted, plasma TSF levels decreased thereafter, i.e., 111% of control after 8 hours and 99% of control after 16 hours. Platelet counts in mice exposed to 750 R and 900 R x-rays progressively decreased to severe thrombocytopenia by day 7, but almost normal RBC counts were maintained. Sera or plasma from animals with x-ray-induced thrombocytopenia caused significant increases in 35S incorporation into platelets of TSF-assay mice (196% of control, P less than 0.005 after 750 R and 141% of control, P less than 0.025 after 900 R). A combination of x-irradiation and RAMPS-injection did not produce greater TSF levels in mice than did x-ray or RAMPS treatment alone.

Characterization of a thrombocytopoietic-stimulating factor from kidney cell culture medium.

The chemical characteristics of a thrombocytopoietic-stimulating factor (TSF or thrombopoietin) found in serum-free kidney cell culture medium were further delineated by subjecting the TSF-rich medium to varying temperatures, different pH, and trypsin digested; the ability of TSF to bind lectins on affinity chromatography was also determined. After treatment, the TSF was assayed in immunothrombocythemic mice by its ability to increase the incorporation of 35S-sodium sulfate into newly formed platelets. TSF appeared to be relatively heat stable; incubation of TSF for 16 h at temperatures of 4, 37, and 56 degrees C showed no loss of TSF activity. However, after incubation at 85 degrees C, TSF was completely inactivated TSF in culture medium was stable of pH 1-8. Above these pH values, the potency of the TSF material decreased sharply. Digestion of TSF with trypsin completely destroyed the thrombocytopoietic-stimulating activity. For TSF purification, two different lectin-agarose derivatives were used; i.e., wheat germ agglutinin (WGA) and concanavalin A (Con A). Both lectins bound TSF, and the hormone was eluted by the sugars specific for the particular lectin. lectins, therefore, can be used to partially purify the hormone; a further 10 to 200-fold purification was achieved by these techniques. Since other workers have shown that TSF from plasma of thrombocytopenic rabbits will bind WGA and Con A, TSF from kidney cell culture medium and TSF from animal sources appear to have similar carbohydrate compositions.

A four-step procedure for the purification of thrombopoietin.

The present work reports the preparation of a highly bioactive and stable thrombocytopoiesis-stimulating factor (TSF or thrombopoietin) by a four-step purification procedure, i.e., Sephadex column chromatography, ethanol precipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and reverse phase-high performance liquid chromatography. The molecular weight (MW) of the purified product depended upon the method of purification, i.e., using denaturing buffers at 56 degrees C for 10 min, the MW was approximately 30,000 daltons; whereas, after preparing in denaturing buffers and heating to 100 degrees C for 10 min, the purified protein had an apparent MW of approximately 15 kd. Both moieties had significant biological activity. The data indicate that TSF may exist normally as a dimer (30 kd), but can disassociate to 15 kd without loss of bioactivity. The present work illustrates that the purified TSF has an isoelectric pH of 4.47 and exists in trace amounts in human embryonic kidney (HEK) cell culture media. The final product prepared in the presence of Tween-20 had a specific activity of approximately 21,000 U of TSF per mg of protein, representing a purification factor of approximately 164,000. Using this four-step purification procedure, a homogeneous product was obtained as judged by SDS-PAGE and chromatofocusing. This purified material will be suitable for further studies, including amino acid sequencing.

High doses of recombinant erythropoietin stimulate platelet production in mice.

Previously, recombinant erythropoietin (rEpo) was shown to increase the number and size of megakaryocytic colonies in vitro, and in vivo it elevates the number of megakaryocytes in mouse spleens. To test the hypothesis that rEpo would stimulate platelet production in mice, both normal mice and mice in rebound-thrombocytosis were injected with rEpo and the %35S incorporation into platelets was measured. A thrombocytopoiesis-stimulating factor (TSF or thrombopoietin) was used as a positive control. rEpo increased isotopic incorporation into platelets of both normal mice and mice in rebound-thrombocytosis, as did TSF, but required large doses (15 U rEpo/mouse). In other mice, hematocrits, platelet counts, platelet sizes, and 24-hr %35S incorporation into platelets were measured 2 days after injection of two equally divided doses of either rEpo or TSF. Significant increases in both platelet sizes and %35S incorporation into platelets were found after injections of 15 U rEpo/mouse or 2.3 U TSF/mouse. These data indicate that rEpo, at high doses, will stimulate platelet production in mice, and may suggest molecular similarities between rEpo and TSF and their ability to compete for common receptor sites on megakaryocytes and their progenitor cells.