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PubMed1988

Membrane-associated forms of peptidylglycine alpha-amidating monooxygenase activity in rat pituitary. Tissue specificity.

Membrane-associated peptidylglycine alpha-amidating monooxygenase (PAM) activity was investigated in rat anterior and neurointermediate pituitary tissues and in pituitary AtT-20/D-16v and GH3 cell lines. A substantial fraction of total pituitary PAM activity was found to be membrane-associated. Triton X-100, N-octyl-beta-D-glucopyranoside, and Zwittergent were effective in solubilizing PAM activity from crude pituitary membranes. The distribution of enzyme activity between soluble and membrane-associated forms was tissue-specific. In the anterior pituitary lobe and pituitary cell lines, 40-60% of total PAM activity was membrane-associated while only 10% of the alpha-amidating activity in the neurointermediate lobe was membrane-associated. Soluble and membrane-associated forms of PAM shared nearly identical characteristics with respect to copper and ascorbate requirements, pH optima, and Km values. Upon subcellular fractionation of anterior and neurointermediate pituitary lobe homogenates on Percoll gradients, 12-18% of total PAM activity was found in the rough endoplasmic reticulum/Golgi fractions and 42-60% was localized to secretory granule fractions. For both tissues, membrane-associated PAM activity was enriched in the rough endoplasmic reticulum/Golgi pool, whereas most of the secretory granule-associated enzyme activity was soluble.

Animals↗

PubMed1987

Flow cytometry analysis of DNA damage and the evaluation of cytotoxicity of alkylating agents.

Monoclonal antibody (MAb) F7-26 generated against nitrogen mustard (HN2)-treated DNA (O.S. Frankfurt, Exp. Cell Res., 170: 369-380, 1987) reacted with regions of local DNA denaturation (distortion) induced by DNA alkylation. The relationship between immunoreactivity of cellular DNA with MAb F7-26 and cytotoxic effects of HN2, L-phenylalanine mustard (L-PAM), and 1,3-bis(2-chloroethyl)-1-nitrosourea was studied in HeLa S3 cultures. Cells were treated with drugs for 1 h and assessed for cell survival by colony formation assay and for DNA immunoreactivity by flow cytometry. Cells were fixed in ethanol, exposed to MAb, and stained with fluorescein-labeled anti-mouse immunoglobulin. Immunofluorescence (IF) intensity was measured on a flow cytometer. For each drug the cell killing and the binding of MAb to DNA appeared in the same dose ranges. A strong correlation (r = 0.96) between cell survival (log10 surviving fraction) and IF was observed when data for HN2, L-PAM, and 1,3-bis(2-chloroethyl)-1-nitrosourea were combined. This correlation was apparent in the range of 1-5 log10 cell killing. Enhancement of L-PAM cytotoxicity by buthionine sulfoximine (BSO) or hyperthermia was accompanied by a proportional increase of DNA immunoreactivity with MAb F7-26. The enhancement factors calculated from survival curves (a ratio of the dose decreasing cell survival by 1 log10 for L-PAM alone to that for L-PAM combined with modulating factor) were 1.67, 1.58, and 3.07 for BSO, hyperthermia, and BSO plus hyperthermia, respectively. For the same treatment regimens the enhancement factors calculated from drug dose-IF curves were 1.73, 1.34, and 3.79. A strong correlation between log10 surviving fraction and IF intensity (r = 0.93) was observed when data for L-PAM alone or L-PAM combined with BSO and/or hyperthermia were considered together in the range of 1-6 log10 cell killing. The cytotoxicity of alkylating agents and nitrosoureas and the effectiveness of factors modulating chemotherapeutic effects can be predicted by flow cytometry analysis of DNA immunoreactivity with MAb F7-26.

Alkylating Agents↗

PubMed1984

Surface membrane heterogeneity among human mononuclear phagocytes.

Considerable information has been accumulated about the functional and metabolic differences that exist among human mononuclear phagocytes isolated from different anatomic sites. This heterogeneity may reflect the influence of environmental factors that stimulate circulating monocytes to differentiate in a distinctive manner, or may suggest the existence of predetermined subsets of macrophage precursors. The present study was designed to evaluate macrophage diversity at the membrane level by defining the expression of antigenic determinants on the surface of these cells. The expression of two new membrane differentiation antigens, BMM1 and PAM1, and of Mo1 and Mo2 were evaluated on blood monocytes, macrophages derived from cultured monocytes, breast milk macrophages (BMM), pulmonary alveolar macrophages (PAM), and peritoneal macrophages. Anti-BMM1 is a mouse IgG2a monoclonal antibody obtained by immunization with breast milk cells that recognizes an antigen expressed only on BMM but not on blood monocytes (or any other circulating cells), PAM, and peritoneal macrophages. BMM1 expression is also seen on HL60 promyelocytes induced toward macrophage differentiation by lymphokines but not by phorbol diester. Anti-PAM1, an IgG1 monoclonal antibody raised by immunization with PAM, reacts with an antigen found only on PAM. Blood monocytes, BMM, and peritoneal macrophages all share the previously described differentiation antigens, Mo1 and Mo2 (as well as Ia), whereas these markers are not found on PAM. BMM1 is associated with a two subunit surface protein of 46 and 40 Kd, and PAM1 resides on a 200 Kd polypeptide. The appearance of new antigens during differentiation (BMM1 on milk macrophages and PAM1 on PAM) and the disappearance of antigens more common to the macrophage lineage (absence of Mo1 and Mo2 on alveolar macrophages) indicate a significant heterogeneity at the membrane level among phagocytes obtained from different anatomic sites (but arising from a common myeloid precursor). The functional relevance of these structures selectively expressed by BMM and PAM is the object of further investigation.

Antibodies, Monoclonal↗

PubMed1984

Cryopreservation of human pulmonary alveolar macrophages.

Human pulmonary alveolar macrophages (PAM) from 30 patients with a variety of pulmonary diseases were tested for their ability to undergo cryopreservation. The cells were cryopreserved and stored under liquid nitrogen for intervals of 2, 4, 6, 8, or 12 wk, then assayed for viability (using the trypan dye exclusion method as well as the NADH-dependent cytochrome c reductase (cytochrome c) assay) and cellular function (as documented by the measurement of in vitro aryl hydrocarbon hydroxylase (AHH) induction by benzanthracene (BA) and by quantitation of PAM particulate phagocytosis). These results demonstrated no decrease in PAM viability after 2 wk of cryopreservation compared with that of the control cells (p greater than 0.30, paired, 2-tailed t test). However, PAM viability decreased slightly compared with the 0-time (p less than 0.003 in all instances) when cells were stored for intervals of 4, 6, 8, or 12 wk. In addition, cells demonstrated no further decrease in viability after being cryopreserved for as long as 12 wk, thawed, and cultured for as long as 48 h compared with the 0-time control cells (p greater than 0.10 in all instances). Similarly, when AHH induction was fluorometrically quantitated in PAM cultured for 24 h, there was no decrease in BA-induced AHH levels after a 2-wk cryopreservation period. However, AHH levels decreased slightly compared with those in the 0-time control cells (p less than 0.004), when PAM were stored for longer intervals of 4, 6, or 8 wk. The phagocytic activity of cryopreserved PAM was also quantitated using amorphous silica as a substrate.(ABSTRACT TRUNCATED AT 250 WORDS)

Aryl Hydrocarbon Hydroxylases↗

PubMed1981

Lysosomal enzyme activity in pulmonary alveolar macrophages from conventional, germfree, monoassociated, and conventionalized rats.

Pulmonary alveolar macrophages (PAM) were harvested from conventional (CONV), germfree (GF), conventionalized, and monoassociated (MA) rats. Germfree rats had significantly fewer PAM than did their CONV, conventionalized or MA counterparts. The bronchopulmonary wash from the CONV and conventionalized rats contained higher lysosomal specific activity for beta-glucuronidase and cathepsin D than did similar washes from GF rats. Cellular and subcellular PAM fractions from GF rats also showed decreased enzyme activity in comparison with similar fractions from the PAM or CONV rats. Colonization of GF rats with one (MA) or more bacterial species (conventionalized) increased the beta-glucuronidase and cathepsin D activity of their PAM as well as total PAM. These data suggest that the intestinal flora not only enhances PAM proliferation but also is associated with an increase in their lysosomal enzyme activity.

Animals↗

PubMed1994

Cooperation between staphylococcal enterotoxin B and low dose melphalan in the cure of mice bearing a large MOPC-315 tumor and extensive metastases.

We have recently demonstrated the importance of V beta 8+/CD8+ cells for the curative effectiveness of a suboptimal low dose (0.75 mg/kg) of melphalan (L-phenylalanine mustard; L-PAM) for mice bearing a large s.c. MOPC-315 tumor and extensive metastases. Here we show that staphylococcal enterotoxin B (SEB), which is known to selectively stimulate T cells expressing members of the TCR-V beta 8 gene family, substantially improved the curative effectiveness of the suboptimal dose of L-PAM for mice bearing a large MOPC-315 tumor. Moreover, treatment of mice with mAb F23.1 (anti-V beta 8) abrogated the in vivo therapeutic effect of SEB for low dose L-PAM-treated MOPC-315 tumor bearers (L-PAM TuB mice). Analysis of the effect of SEB on the tumor-infiltrating lymphocytes (TILs) demonstrated that the SEB-mediated therapeutic effect was associated with a significant increase in: 1) the percentage of V beta 8+ cells among the CD8+ T cells that accumulated in the s.c. tumor nodules, 2) the total number of V beta 8+/CD8+ cells present per tumor on day 4 after low dose L-PAM therapy, and 3) the ability of the TILs to lyse MOPC-315 tumor cells in vitro in a short term assay. Furthermore, treatment of mice with mAb F23.1 abolished the ability of SEB to render the TIL population of L-PAM TuB mice more cytotoxic in vitro for MOPC-315 tumor cells. Thus, the SEB-mediated improvement in the therapeutic outcome of low dose L-PAM therapy for mice bearing a large MOPC-315 tumor may be due in part to SEB-mediated increase in the contribution of the V beta 8+ T cells to tumor eradication through enhancement in the magnitude of the anti-MOPC-315 lytic activity exhibited by the TIL population.

Animals↗

PubMed1993

Involvement of TCR-V beta 8.3+ cells in the cure of mice bearing a large MOPC-315 tumor by low dose melphalan.

We have previously shown that the curative efficacy of low dose melphalan (L-phenylalanine mustard; L-PAM) for mice bearing a large s.c. MOPC-315 tumor requires the participation of CD8+ (but not CD4+) T cell-dependent antitumor immunity. Here we show that CD8+ T cells obtained from regressing tumors on day 4 or 5 after low dose L-PAM therapy of MOPC-315 tumor bearers (L-PAM TuB mice) display a preferential enhancement in the utilization of the TCR-V beta 8.3 gene segment as compared to CD8+ T cells from normal lymph nodes. Treatment of L-PAM TuB mice with mAb F23.1, which leads to the depletion of V beta 8.3+ cells, as well as V beta 8.1 and 8.2+ cells, led to a significant reduction in the ability of their tumor-infiltrating lymphocytes as well as their spleen cells to lyse MOPC-315 tumor cells in vitro in a short term assay. In addition, the mAb F23.1 treatment almost completely abrogated the lytic activity of the tumor-infiltrating lymphocytes against another syngeneic, antigenically related plasmacytoma (the MOPC-104E). Moreover, the mAb F23.1 treatment significantly reduced the curative effectiveness of low dose L-PAM for mice bearing a large MOPC-315 tumor. In contrast, mAb KJ16 treatment, which leads to the depletion of V beta 8.1 and 8.2+ cells (but not V beta 8.3+ cells), did not reduce significantly the curative effectiveness of low dose L-PAM for such MOPC-315 tumor bearers. Thus, V beta 8.3+ T cells are important for the curative effectiveness of low dose L-PAM therapy for MOPC-315 tumor bearers, and it is conceivable that the V beta 8.3+ cells mediate their effect (at least in part) by contributing to the acquisition of CTL activity against plasmacytoma-shared Ag.

Animals↗

PubMed2000

Synergism of buthionine sulfoximine and melphalan against neuroblastoma cell lines derived after disease progression.

BACKGROUND: Despite intensive-alkylator based regimens, >50% of patients with high-risk neuroblastoma (NB) die from recurrent disease that is probably due, in part, to acquired alkylator resistance. PROCEDURE: Using buthionine sulfoximine (BSO)-mediated, glutathione (GSH) depletion to modulate melphalan (L-PAM) resistance, we examined six NB cell lines established after progressive disease following either standard chemotherapy, BSO/L-PAM therapy, or myeloablative therapy and autologous hematopoietic stem cell transplant (AHSCT). RESULTS: Four of the six cell lines (three p53-nonfunctional and one p53-functional) showed high-level L-PAM resistance. CONCLUSIONS: Fixed ratio analysis demonstrated BSO/L-PAM synergy (combination index >1) for all cell lines tested. In L-PAM-resistant cell lines, the minimal cytotoxicity observed for BSO combined with nonmyeloablative concentrations of L-PAM was markedly enhanced (>4 logs total cell kill) when BSO was combined with myeloablative concentrations of L-PAM. In alkylator-resistant NB, the optimal use of BSO may require dose escalation of L-PAM to levels requiring AHSCT.

Antimetabolites, Antineoplastic↗

PubMed1991

Comparative morphology and morphometry of alveolar macrophages from six species.

Pulmonary alveolar macrophages (PAM) were collected from normal, healthy mice, rats, dogs, cynomolgus monkeys, chimpanzees, and humans and evaluated for morphologic and morphometric characteristics. The PAM of mice, rats, and dogs were morphologically similar and had statistically similar frequency distributions for size. The cell size distribution for these three species was relatively homogeneous. The PAM of nonhuman primates and humans were morphologically heterogenous with sometimes prominent cytoplasmic vacuolation, irregular cell outlines, and increased numbers of multinucleated cells as compared to the PAM of rodents and dogs. The mean size of human PAM was statistically greater than that for all other species evaluated, including nonhuman primates. These data indicate that significant differences in PAM morphology and size exist among species.

Animals↗

PubMed2004

Paint-assisted microdissection-FISH: Rapid and simple mapping of translocation breakpoints in the embryonal rhabdomyosarcoma cell line RD.

BACKGROUND: Spectral karyotyping and multiple fluorophore fluorescence in situ hybridisation (M-FISH) facilitate identification of inter-chromosomal rearrangements, but are of low cytogenetic resolution in mapping translocation breakpoints. Reverse chromosome painting yields increased cytogenetic information but isolation of aberrant chromosomes is technically difficult. We have developed the technique of paint-assisted microdissection FISH (PAM-FISH), which enables microdissection of aberrant chromosomes to be carried out easily and rapidly using relatively simple apparatus. METHODS: A selected chromosome paint is hybridised to abnormal metaphases to label a chromosome of interest, which is then microdissected, amplified, labelled by polymerase chain reaction (PCR), and reverse painted onto extended normal metaphases. RESULTS: PAM-FISH was used to reassess structural chromosomal abnormalities identified by molecular cytogenetics in the rhabdomyosarcoma cell line RD. PAM-FISH improved the analysis of virtually all structural abnormalities, identifying six novel translocations and indicating that seven previously described rearrangements were in fact not present in RD. Accuracy of the breakpoint mapping obtained was confirmed by bacterial artificial chromosome-FISH. CONCLUSIONS: PAM-FISH is ideally suited to analysis of tumour metaphases as it is not affected by poor chromosome morphology. Reagents generated by PAM-FISH are also suitable for other investigations, such as mapping using sequence tagged-site PCR or genomic microarrays. PAM-FISH is technically straightforward and could readily be adopted in a routine cytogenetics laboratory for accurate high-throughput analysis of chromosome breakpoints.

Cell Line, Tumor↗

PubMed1987

Alveolar macrophage phagocytic kinetics following pulmonary parainfluenza-3 virus infection.

Qualitative and quantitative evaluations of the cellular components of bronchoalveolar washings of calves with experimental parainfluenza-3 virus pneumonitis and control calves were made. Calves were exposed to 10(9) TCID50 of PI-3 by intranasal aerosol exposure and bronchoalveolar cells obtained 7 days after infection by volume-controlled bronchopulmonary lavage. Transient tachypnea and pyrexia occurred in all infected calves, and virus was recoverable at 7 days from nasal swabs and lung tissue. Pulmonary lesions were typical of viral pneumonitis, characterized by patchy alveolitis and bronchiolitis with accumulations of cells and inflammatory debris. The mean total lavage cell yield was elevated in the virus-infected calves, and the percentage of neutrophils was elevated (P less than 0.05). Increased numbers of pulmonary alveolar macrophages (PAM) were also recovered but the difference was not significant. Linear regression equations showed that a decreased proportion of PAM from virus-infected animals were phagocytic. The mean initial phagocytic rates of macrophages from calves with viral pneumonitis were significantly decreased (P less than 0.05) over controls. This difference was concentration dependent and required a phagocytic stimulus in excess of 12.5 X 10(6) beads/ml. Studies of phagocytic kinetics showed that PAM from calves with viral pneumonitis had a lower Vmax than PAM from control calves, but that Km values were comparable. No differences in PAM beta-glucuronidase and acid phosphatase activity were observed. These results indicate depressed phagocytic function in PI-3 virus-inflamed lungs relative to controls. In concert with virus-induced airway lesions, such in vivo depression of PAM phagocytic functions would be expected to depress pulmonary particulate clearance and lung defense mechanisms.

Animals↗

PubMed1988

Two distinct cytolytic mechanisms of macrophages and monocytes activated by phorbol myristate acetate.

Pulmonary alveolar macrophages (PAM) and peripheral blood monocytes (PBMO) of the miniature swine can be converted to cytolytically active effector cells by treating with phorbol myristate acetate (PMA) as determined by enhancement of cytotoxicity to various target cells. Kinetics of the PMA-activated PAM and PBMO in cytotoxicity show that the effective PMA concentration ranges from 10 to 1,000 ng/ml. Induction of cytotoxic macrophages and monocytes occurred as early as 30 min and to their maximum cytotoxicity after 1 hr exposure to PMA and the enhanced cytotoxic activity persisted up to 24 to 40 hr when PMA was removed by washing after 1 hr exposure, but prolonged exposure to PMA for more than 6 hr resulted in a drastic decrease of cytolytic activities suggesting the prolonged exposure to PMA causes macrophages and monocytes to become refractory to PMA stimulation. Target cells displayed varying degrees of cytotoxic sensitivity to the PMA-activated PAM and PBMO; PRBC, SRBC, and K562 were sensitive, WEHI-164 and U937 were relatively sensitive, and SB was very resistant to these activated effector cells. The mechanisms of PMA-induced cytotoxicity could largely be divided into two categories. One was the H2O2 mediated killing as shown by complete reduction of cytotoxicity after adding catalase in the assay. The other was the proteases mediated cytolysis, which could be blocked by protease inhibitors, Phenyl methyl sulfonyl fluoride (PMSF), and N- alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK). H2O2 was the only mediator produced in large enough quantities from PBMO to kill target cells, whereas PAM could produce both mediators (H2O2 and proteases). PRBC, SRBC, and K562 appeared to be killed by H2O2 produced by PAM and PBMO. In contrast, U937 and WEHI-164 appeared to be killed by proteases in PAM mediated cytolysis but by H2O2 in PBMO-mediated cytolysis. These results suggest that the observed cytolytic mechanisms can be differed by type of target cells as well as the source of mononuclear phagocytes within the individual animal.

Animals↗

PubMed1991

Porcine alveolar and pulmonary intravascular macrophages: comparison of immune functions.

Although a substantial amount of information is available on pulmonary alveolar macrophages (PAMs), little is known about pulmonary intravascular macrophages (PIMs), a separate population of lung macrophages found apposed to the endothelium of pulmonary capillaries. We compared these two populations of lung immunocytes to determine their relative immunological activity. Our results suggest that PAMs are more phagocytic than PIMs; however, PIMs may be more efficient at lysing ingested bacteria than PAMs. Although similar in antibody-dependent cellular cytotoxicity, PIMs are more spontaneously cytolytic than PAMs. Depending upon the effector:target cell ratio studied, the tumoricidal activity of PIMs was less than or equal to that of PAMs. Both cell populations produced the cytokines interleukin-1 and tumor necrosis factor-alpha at similar concentrations. These data suggest that PIMs are immunologically active, although the degree of activity may differ between PIMs and PAMs.

Animals↗

PubMed2003

Androgen-independent expression of adrenomedullin and peptidylglycine alpha-amidating monooxygenase in human prostatic carcinoma.

Most of the locally advanced and metastatic prostate carcinomas (PCs) treated with antiandrogenic therapy eventually become refractory to this treatment. Locally produced factors may control prostate tumor biology after androgen withdrawal. Adrenomedullin (AM) is expressed in the prostate and could control cell growth in androgen-independent conditions. AM needs to be amidated by the enzyme peptidylglycine alpha-amidating monooxygenase (PAM) to become fully active. The objective of the present study was to analyze whether the expression of preproadrenomedullin (preproAM) and PAM in PC is regulated by androgens. For this purpose, human in vitro and in vivo PC models were grown in the presence or absence of androgens, and the expression of AM and PAM was examined by immunohistochemistry, Western blotting, RT-PCR, and Northern blotting. Furthermore, immunohistochemical analysis of AM in clinical specimens was performed to test if its expression is related to Gleason score and antiandrogenic therapy. In PC cell lines and xenografts, mRNA and protein AM levels were similar in the presence or absence of androgens. PAM expression seemed to be induced by androgen-withdrawal. Our results in clinical samples showed no relationship between AM expression and Gleason score or antiandrogenic treatment. In conclusion, our results demonstrate that preproAM and PAM expression in the human prostate is androgen-independent. In addition, we also report for the first time the expression of a novel PAM transcript in PC, which has not been previously described in other tissues.

Adolescent↗

PubMed2000

Genomic organization and splicing variants of a peptidylglycine alpha-hydroxylating monooxygenase from sea anemones.

Cnidarians are primitive animals that use neuropeptides as their transmitters. All the numerous cnidarian neuropeptides isolated, so far, have a carboxy-terminal amide group that is essential for their actions. This strongly suggests that alpha-amidating enzymes are essential for the functioning of primitive nervous systems. In mammals, peptide amidation is catalyzed by two enzymes, peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL) that act sequentially. These two activities are contained within one bifunctional enzyme, peptidylglycine alpha-amidating monooxygenase (PAM), which is coded for by a single gene. In a previous paper (F. Hauser et al., Biochem. Biophys. Res. Commun. 241, 509-512, 1997) we have cloned the first known cnidarian PHM from the sea anemone Calliactis parasitica. In the present paper we have determined the structure of its gene (CP1). CP1 is >12 kb in size and contains 15 exons and 14 introns. The last coding exon (exon 15) contains a stop codon, leaving no room for PAL and, thereby, for a bifunctional PAM enzyme as in mammals. Furthermore, we found a CP1 splicing variant (CP1-B) that contains exon-9 instead of exon-8, which was present in the previously characterized PHM cDNA (CP1-A). CP1-A and -B have 97% amino acid sequence identity, whereas both splicing variants have around 42% sequence identity with the PHM part of rat PAM. Essential amino acid residues for the catalytic activity and the 3D structure of PHM are conserved between CP1-A, -B and the PHM part of rat PAM. Furthermore, eight introns in CP1 occur in the same positions and have the same intron phasing as eight introns in the rat PAM gene, showing that the sea anemone PHM is not only structurally, but also evolutionarily related to the PHM part of rat PAM.

Alternative Splicing↗

PubMed1987

Some characteristics of the in vivo antitumor immunity exhibited by mice cured of a large MOPC-315 tumor by a low dose of melphalan.

BALB/c mice cured of a large MOPC-315 or MOPC-104E plasmacytoma following treatment with a low dose (2.5 mg/kg) of melphalan (L-PAM) were resistant to challenge with the other plasmacytoma but to a much lesser extent than to challenge with the autochthonous plasmacytoma. The resistance of the L-PAM-cured MOPC-315-tumor bearers to challenge with MOPC-104E tumor cells was increased when the MOPC-104E tumor cells were admixed with MOPC-315 tumor cells prior to their inoculation. This enhanced resistance to MOPC-104E cells was due to elimination of the MOPC-104E tumor cells through an innocent bystander killing effect since it did not render the mice more resistant to a subsequent challenge with MOPC-104E tumor cells alone. Administration of carrageenan to L-PAM-cured MOPC-315-tumor bearers 1 day after the challenge with the mixture of MOPC-104E and MOPC-315 tumor cells drastically reduced the ability of the mice to resist the tumor challenge. All of the tumors that developed in such mice were of MOPC-104E origin only (as judged by the binding specificity of the myeloma proteins secreted by the tumor cells as well as that present on their surface) even though (a) the tumor inoculum used consisted of up to 10-fold more MOPC-315 than MOPC-104E tumor cells and (b) the MOPC-315 tumor cells divide more rapidly. The same protocol of carrageenan treatment did not reduce the ability of normal BALB/c mice to develop in vivo a primary cell-mediated cytotoxic response nor a primary antibody response indicating that it has no effect on the initiation of an immune response. Therefore, it is conceivable that carrageenan treatment reduced the ability of L-PAM-cured MOPC-315-tumor bearers to reject a challenge with MOPC-315 and MOPC-104E tumor cells by interfering at the effector stage. The ability of the L-PAM-cured MOPC-315-tumor bearers to reject the MOPC-315 cells present in the challenge mixture was reduced when the mice were treated with anti-Thy 1.2 antibody but not with carrageenan, indicating that T-cells independent from carrageenan-sensitive effector cells are required for the rejection of the MOPC-315 tumor cells. Thus, at least two different effector mechanisms participate in the rejection of a challenge composed of MOPC-315 and MOPC-104E tumor cells by L-PAM-cured MOPC-315-tumor bearers.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1984

Melphalan-mediated potentiation of antitumor immune responsiveness of immunosuppressed spleen cells from mice bearing a large MOPC-315 tumor.

Administration of a low dose of L-PAM (0.75 mg/kg) to mice bearing a large SC MOPC-315 tumor and extensive metastases led to the development of augmented antitumor immune potential in their hitherto immunosuppressed spleen cells. Such drug-induced potentiation of antitumor immune responsiveness appeared by day 2 after chemotherapy, and it could not be further enhanced but was actually reduced by depletion of glass-adherent cells, a procedure which is effective in depleting the cells known to have inhibitory activity (i.e., macrophages and metastatic tumor cells). To establish that L-PAM can lead to selective in situ abrogation of the inhibitory effectiveness of the splenic macrophages and metastatic tumor cells, we demonstrated that incubation of immunosuppressed tumor-bearer spleen cells with a low concentration of L-PAM in vitro also resulted in augmented antitumor immune potential that could not be further augmented by depletion of glass-adherent cells. L-PAM-mediated enhancement of the antitumor immune potential of immunosuppressed tumor bearer spleen cells was due at least in part to the effects of the drug on the splenic metastatic tumor cells. Isolated tumor cells treated with a low concentration of L-PAM were not only devoid of inhibitory activity for the primary in vitro antitumor immune response by normal spleen cells, but actually manifested a strong immunostimulatory capacity. Thus, L-PAM given at a low dose enhances the development of potent antitumor immunity which brings about the eradication of a large tumorigenic load that remains after the drug has been cleared from the circulation.

Animals↗

PubMed1989

Relevance of the hydrolysis and protein binding of melphalan to the treatment of multiple myeloma.

Experiments to determine the hydrolysis and protein binding of melphalan (L-phenylalanine mustard, L-PAM) were carried out in vitro for therapeutic concentration of the drug: the decrease in L-PAM concentration in plasma and whole blood during 24 h incubation at 37 degrees C was only 5% due to hydrolysis. Serum protein binding was about 90%, whereby 60% and 20% of this binding was due to interactions with albumin and acid alpha 1-glycoprotein, respectively. Immunoglobulins did not participate in the binding of L-PAM. The covalently bound part of L-PAM in serum was 30% in the concentration range of 1-30 micrograms/ml. The binding of dihydroxymelphalan (DOH) in serum did not exceed 20%. Glucocorticoids used in combination with L-PAM for treating multiple myeloma did not influence its protein binding. Our study with 35 sera from 15 patients with multiple myeloma shows that high levels of paraproteins do not increase but may decrease the binding of L-PAM, resulting in an elevated concentration of free drug.

Blood Proteins↗