Autologous Bone Marrow Transplantation - Blog Science Connections

Chemoimmunoseparation of T Lymphoma Cells 349
from the peripheral blood of patients; thawed; treated with deoxycoformycin
plus deoxyadenosine, 3A1 plus complement, or both combinations; and
counted in a clonogenic assay in semisolid medium.
With the clonogenic assay, about 6 logs of HSB-2 T cells can be measured
(A. Haleem et ai, unpublished data). Three treatments with 3A1 antibody and
complement eliminated more than 2 logs of malignant cells. Use of deoxycoformycin
and deoxyadenosine for 5 hours eliminated almost 3 logs of
malignant cells. Combined treatment with 3A1, complement, deoxycoformycin
and deoxyadenosine eliminated more than 4 logs. Under these same conditions,
treatment with 3A1 and complement with or without deoxycoformycin and
deoxyadenosine failed to affect growth of CFUs-GM. When deoxycoformycin,
deoxyadenosine, 3A1, and complement were used alone or in combination
against five T leukemia cell lines positive for CD 7, additive toxicity was obtained
against colony-forming units. With two other cell lines that did not strongly
express CD 7, additive effects were not obtained. Using a combination of
deoxycoformycin, deoxyadenosine, 3A1, and complement, all clonogenic units
could be removed from samples of leukemic cells directly cryopreserved from
six patients with T-cell malignancies.
In subsequent studies (R. B. Montgomery et ai, unpublished data), we have
asked whether immunoseparation might be improved through the use of an
immunotoxin conjugate containing 3A1 and pokeweed antiviral protein (3A1-
PAP). When 3A1 -PAP was used in concentrations ranging from 0.1 -10 Aig/ml,
approximately 2 logs of malignant cells could be eliminated at the highest
immunotoxin concentration. Addition of 100 ulA chloroquine to the incubation
mixtures eliminated 1 additional log of malignant cells. A combination of
3A1 -PAP chloroquine with deoxycoformycin and deoxyadenosine proved more
effective than either immunoseparation or chemoseparation alone, permitting
the elimination of more than 4 logs of malignant cells. Increasing concentrations
of 3A1-PAP proved toxic for human CFUs-GM. Similarly, deoxyadenosine
concentrations in excess of 1 mM proved inhibitory for CFUs-GM. Using a
concentration of 3A1 -PAP, deoxycoformycin, and deoxyadenosine that proved
optimal for eliminating malignant cells, we eliminated at least 50% of CFUs-GM.
In summary, a combination of chemoseparation using deoxycoformycin
and deoxyadenosine with immunoseparation using either 3A1 and complement
or 3A1 -PAP and chloroquine was more effective than either single modality for
eliminating malignant clonogenic T cells from human bone marrow. Chemoimmunoseparation
with deoxycoformycin, deoxyadenosine, 3A1, and complement
eliminated 4 logs of HSB-2 T lymphoma cells under conditions that did
not affect CFU-GM, BFU-E, or CFU-GEMM growth. Chemoimmunoseparation
with deoxycoformycin, deoxyadenosine, 3A1-PAP, and chloroquine could also
eliminate at least 4 logs of clonogenic HSB-2 T lymphoma cells, but antitumor
activity had to be weighed against inhibition of CFU-GM growth. Phase 1 studies
with deoxycoformycin, deoxyadenosine, 3A1, and complement are anticipated
in the near future to cleanse marrows from patients with T-cell malignancies.