Angelo Dinota

Overexpression of multidrug resistance‐associated p170‐glycoprotein in acute non‐lymphocytic leukemia

Abstract: Resistance to several cytotoxic agents, including anthracyclines, vinca alkaloids and epipodophylline derivatives (multidrug resistance, or MDR) can develop in tumor cells by overexpression of a 170‐kd glycoprotein (p170) which is an essential component of a membrane transport system leading to increased drug efflux and decreased intracellular drug concentration. By means of a p170‐directed monoclonal antibody (MRK‐16) and immunocytochemistry (alkaline phosphatase anti‐alkaline phosphatase technique), we investigated the expression of p170 in marrow blast cells of 59 cases (38 at diagnosis and 21 in relapse) of acute‐non‐lymphocytic leukemia (ANLL). The proportion of strongly MDR‐positive cells was higher in relapse that at diagnosis (median 15.5% vs 1.5%). Out of 31 patients who were evaluable for the results of first remission induction, failure of first‐line treatment (including Daunorubicin, standard‐dose and high‐dose Arabinosyl Cytosine, and sometimes also Mitoxantrone) occurred in 8/22 MDR‐positive cases and in 1/9 MDR‐negative ones (p = 0.21). Failure of first‐line treatment was always associated with a progressive increase of p170 expression. Total failures (no remission plus early relapse) were more frequent (p = 0.001) among MDR‐positive cases (16/22) than among the others (2/9). These data show that MDR is very frequent in ANLL also at diagnosis and suggest that MDR can contribute to early failure of standard treatment.

An immunotoxin containing momordin suitable for bone marrow purging in multiple myeloma patients.

Attempts have been made by a number of methods to eliminate minimal residual disease from bone marrow to be reinfused in autologous transplantation. In this paper we describe a conjugate containing a monoclonal antibody, named 8A, recognising a plasma cell-associated antigen, and momordin, a ribosome-inactivating protein similar to the ricin A-chain. This immunotoxin is active on target cell lines and on neoplastic plasma cells, while myeloid progenitors are fairly resistant. The conjugate is shown to be acceptable for ex vivo purging in autologous bone marrow transplantation in multiple myeloma patients.

Purification and properties of a new ribosome-inactivation protein with RNA N-glycosidase activity suitable for immunotoxin preparation from the seeds of Momordica cochinchinensis

A ribosome-inactivating protein similar to those already known (Stirpe and Barbieri (1986) FEBS Lett. 195, 1-8) was purified from the seeds of Momordica cochinchinensis. This protein, for which the name of momorcochin-S is proposed, is a glycoprotein, has an Mr of approx. 30,000, and an alkaline isoelectric point and can be considered as an iso-form of the previously purified momorcochin from the roots of M. cochinchinensis. Momorcochin-S inhibits protein synthesis by a rabbit-reticulocyte lysate and phenylalanine polymerization by isolated ribosomes, and alters rRNA in a similar manner as the A-chain of ricin and related toxins (Endo et al. (1987) J. Biol. Chem. 262, 5908-5912). Momorcochin-S was linked to a monoclonal antibody (8A) against human plasma cells, and the resulting immunotoxin was selectively toxic to target cells.

Autologous bone marrow transplantation with immunotoxin‐purged marrow for advanced multiple myeloma

A system to purge the bone marrow of myeloma cells has been developed in our laboratories with the aim of treating with myeloablative radiochemotherapy patients suffering from advanced multiple myeloma. This system is based on the ex vivo incubation of the marrow with an immunotoxin composed of the 8A monoclonal antibody — that recognizes plasma cells and B‐cell precursors — and the ribosome‐inactivating protein momordin. 8 patients have so far been treated. 4 are surviving from 4 to 18 months after ABMT, whereas 4 died after 1 to 6 months, 2 from infections, 1 from relapsing disease and 1 from veno‐occlusive disease. A marked tumour reduction was observed in all evaluable patients; however, none has achieved complete disappearance of the disease. The hæmopoietic reconstitution was significantly delayed in 3 patients. These preliminary results show the feasibility of this approach in advanced MM patients with heavily infiltrated marrow. The place of ABMT in the treatment of MM remains to be determined; the selection of patients with still responding and less advanced disease would probably produce better results.

Immunotoxins containing saporin 6 and monoclonal antibodies recognizing plasma cell-associated antigens: effects on target cells and on normal myeloid precursors (CFU-GM)

Monoclonal antibodies 8A and 62B1, recognizing plasma cell‐associated antigens, were covalently linked to saporin 6, a ribosome‐inactivating protein similar to the A‐chain of ricin. Both immunotoxins were tested on target human cell lines U266 and Raji, on non‐target K562 cell line and on myeloid CFU‐GM progenitors. The cloning efficiency and viability of target cells were strongly reduced by 8A‐saporin 6 and 62B1‐saporin 6 immunotoxins, with an ID50 up to 200000‐fold lower than free saporin 6, whilst the K562 non‐target cell line was unaffected. Normal human myeloid precursors (CFU‐GM) were inhibited by immunotoxins only to a limited extent. An application of this model for autologous bone marrow transplantation in multiple myeloma patients is proposed. Since no eradication of cloning target cells was achieved by a single immunotoxin, mixtures made with different antibodies could help to reach this goal.

A sensitive test for the detection of NK activity. Plasma clot clonogenic assay

Natural killer (NK) activity, which has been implicated in the immune response against viral infections and neoplasias, is currently evaluated by means of a chromium (51Cr) release assay. However, criticisms have been raised with regard to the reliability and reproducibility of the test. We have developed a different in vitro method for measuring NK activity, based on the inhibition of the target clone growth in plasma clot semisolid medium. This method overcomes the limitations inherent to the 51Cr release test and more closely mimics the in vivo situation. The inhibitory activity revealed by the cloning assay was always greater than the lytic activity in the 51Cr release assay. Moreover, effector/target ratios of 3:1 and 1.5:1 still produced clonal inhibition. B-CLL cells, used as effectors, showed no inhibitory activity and the Raji cell line employed as target was resistant in both techniques. Thus, the clonogenic assay appears to be more sensitive for the evaluation of low levels of NK activity, for basic studies on the effector/target interactions, for the evaluation of LAK cell activity, and in diseases in which an involvement of the NK compartment has been hypothesized.

Cytotoxicity of, and DNA damage by, active oxygen species produced by xanthine oxidase

Toxicity to Raji cells of the xanthine oxidase/hypoxanthine system is related to the formation of single‐strand DNA breaks. DNA damage was proportional to the concentration of xanthine oxidase and to the time of exposure. It was prevented by the absence of hypoxanthine, or by the presence of allopurinol, or both superoxide dismutase and catalase. The release of 51Cr from damaged cells was detectable 12h after the inhibition of cloning efficiency and the production of DNA breakage. These data suggest that DNA damage induced by the oxygen products precedes the severe lesion to the cellular membrane.

Selective killing of CD4+ and CD8+ cells with immunotoxins containing saporin

Saporin, a ribosome‐inactivating protein from the seeds of Saponaria officinalis, was covalently linked to an anti‐CD4 monoclonal antibody. The resulting immunotoxin at 10‐9 M concentration was toxic to CD4+ lymphocytes without affecting other cells. Selective elimination of CD4+ and CD8+ cells was also obtained with murine monoclonal anti‐CD4 and anti‐CD8 antibodies and an immunotoxin consisting of saporin linked to an anti‐mouse IgG antibody.

Cryopreserved autologous bone marrow transplantation in patients with acute nonlymphoid leukemia: Chemotherapy before harvesting is the main factor in delaying hematological recovery

We analyzed the kinetics of hematological recovery after autologous bone marrow transplantation in 13 patients with acute nonlymphoid leukemias (ANLL). A comparison was made with 31 patients with non-Hodgkins lymphoma (NHL) whose bone marrow was harvested and cryopreserved, either at diagnosis or after intensive chemotherapy. Hematological recovery of ANLL patients was similar to that of pretreated NHL patients and significantly slower than that of untreated NHL patients. We suggest that chemotherapy before harvest (more than the possible decreased stem cell marrow potentiality resulting from the underlying disease) appears to be the main factor responsible for delayed recovery after autologous bone marrow transplantation in ANLL.

Evidence that long-term bone marrow culture of patients with multiple myeloma favors normal hemopoietic proliferation.

Long-term bone marrow cultures (LTBMC) were initiated with marrow aspirate cells from 12 patients with multiple myeloma (MM) using the Dexter system. The myeloid and the neoplastic myeloma cell growths were evaluated for up to 6-9 weeks. Our results demonstrate the development of an adherent layer capable of supporting normal granulopoiesis with a concomitant drop in the growth of myeloma cells. The B lymphocyte monoclonal proliferative compartment was also studied with bromodeoxyuridine (Brdurd), an analog of thymidine incorporated during the S-phase, and the labeling index was calculated. The ability to form myeloma stem cell colonies in a modified plasma clot short-term assay was also evaluated. The results confirmed that the neoplastic B lineage compartment was not able to grow in Dexters system for more than 4 weeks in 11 of 12 cases studied, with the disappearance of Brdurd-positive cells after two weeks, whereas LTBMC were able to sustain the growth of myeloid progenitors. These data indicate the potential applicability of this culture method in selecting normal hematopoietic progenitors from patients with multiple myeloma. This approach can have significant implications for aggressive treatment of patients with multiple myeloma, especially in trials involving autologous bone marrow transplantation (ABMT).