Chronic Myeloid Leukaemia

SUMMARY. Fourteen cases of Philadelphia chromosome (Ph1) positive chronic myeloid leukaemia in blast transformation have been investigated using cell surface markers. Morphologically eight cases were lymphoid and the remainder myeloid in appearance. All cases were negative with surface markers for thymocytes and T and B lymphocytes. Five of the lymphoid cases reacted with an antiserum specific for acute lymphoid leukaemia (ALL) of non-T non-B type and were also weakly reactive with a lymphocyte reactive antiserum. A sixth patient, whose blast cells were anti-ALL negative (ALL-) at presentation, subsequently developed central nervous system leukaemia with anti-ALL positive (ALL+) blast cells in the CSF. In all cases the leukaemic blast cells showed greatly diminished expression of cholera toxin receptors when compared to granulocytic cells from the chronic phase of CML. This parallels weak or negligible expression of the cholera toxin receptor in ALL and AML.These results suggest that the blastic phase of CML may involve different cellular derivatives of a pluripotential stem cell in which the primary malignant/genetic changes reside. The blast crisis of CML can therefore be heterogeneous with respect to cellular expression and in a significant proportion of patients involves a cell which is by membrane markers and morphological criteria indistinguishable from that seen in the common form of ALL. In these cases the Philadelphia chromosome may be the only distinguishing cellular characteristic.

SUMMARY. Seven patients presenting as an acute leukaemia caused difficulty in diagnosis. The lymphoid appearance of the blast cells either initially or during treatment suggested acute lymphoid leukaemia (ALL). In each case the Philadelphia chromosome was shown to be present thus suggesting that these cases were examples of chronic myeloid leukaemia (CML) presenting in blast crisis without a detectable chronic phase.The implications of these findings are discussed and the difficulty in achieving a precise diagnosis in the acute leukaemias is emphasized. Cytogenetic analysis should be carried out whenever the type of acute leukaemia present is of critical importance.

In view of the increasing interest in the immunotherapy of CML it seems highly desirable to broaden the present knowledge on the immune reac- tivity of CML patients. A group of 24 patients and 24 healthy controls were studied for the total of 15 immunological parameters, including the prevalence of antibodies against human herpesviruses and papil- lomaviruses. To clearly discriminate

Epidemiological studies were conducted in pesticide-exposed agricultural workers along with an equal number of age-and sex-matched controls. All the 200 exposed volunteers were suffering from fever, nausea, headache and other abnormal symptoms and visited the hospital for ...

Background
Incubation of chronic myeloid leukemia cells in hypoxia inhibits growth and selects BCR/Ablindependent cells with stem cell properties which are refractory to imatinib-mesylate. This study aimed to characterize the relationship of this refractoriness with glucose availability in the environment.
Design and Methods
K562 or primary chronic myeloid leukemia cells were cultured at 0.1% O2, different cell densities and glucose concentrations. The stem and progenitor cell potential of these cultures at different times of incubation in relation to BCR/Ablprotein expression and sensitivity to imatinibmesylate was explored by transferring cells to growth-permissive secondary cultures in normoxia, according to the Culture-Repopulating Ability assay methodology.
Results
Hypoxia-resistant cells maintained BCR/Ablprotein expression until glucose was no longer available in primary hypoxic cultures, where glucose availability appeared to regulate cell number and the balance between the enrichment of cells with kinetic properties typical of stem or progenitor cells. Cells surviving merely hypoxic conditions were, upon transfer to secondary cultures,
immediately available for numerical expansion due to the maintained BCR/Ablprotein expression, and were consequently sensitive to imatinib-mesylate. Instead, BCR/Ablprotein–negative cells selected in primary cultures under oxygen/glucose shortage underwent a delayed numerical expansion in secondary cultures, which was completely refractory to imatinib-mesylate. Cells with the latter properties were also found in primary chronic myeloid leukemia
explants.
Conclusions
Glucose shortage in hypoxia was shown to represent the condition selecting BCR/Ablprotein–negative cells refractory to imatinib-mesylate from either chronic myeloid leukemia lines or patients. These cells, exhibiting stem cell properties in vitro, are metabolically suited to home to stem cell niches in vivo and so may represent the chronic myeloid leukemia cell subset responsible for minimal residual disease.

We previously demonstrated that severe hypoxia inhibits growth of Chronic Myeloid Leukemia (CML) cells and selects stem
cells where BCR/Ablprotein is suppressed, although mRNA is not, so that hypoxia-selected stem cells, while remaining
leukemic, are independent of BCR/Abl signaling and thereby refractory to Imatinib-mesylate. The main target of this study
was to address the effects of the proteasome inhibitor Bortezomib (BZ) on the maintenance of stem or progenitor cells in
hypoxic primary cultures (LC1), by determining the capacity of LC1 cells to repopulate normoxic secondary cultures (LC2)
and the kinetics of this repopulation. Unselected K562 cells from day-2 hypoxic LC1 repopulated LC2 with rapid, progenitortype
kinetics; this repopulation was suppressed by BZ addition to LC1 at time 0, but completely resistant to day-1 BZ,
indicating that progenitors require some time to adapt to stand hypoxia. K562 cells selected in hypoxic day-7 LC1
repopulated LC2 with stem-type kinetics, which was largely resistant to BZ added at either time 0 or day 1, indicating that
hypoxia-selectable stem cells are BZ-resistant per se, i.e. before their selection. Furthermore, these cells were completely
resistant to day-6 BZ, i.e. after selection. On the other hand, hypoxia-selected stem cells from CD34-positive cells of blastcrisis
CML patients appeared completely resistant to either time-0 or day-1 BZ. To exploit in vitro the capacity of CML cells to
adapt to hypoxia enabled to detect a subset of BZ-resistant leukemia stem cells, a finding of particular relevance in light of
the fact that our experimental system mimics the physiologically hypoxic environment of bone marrow niches where
leukemia stem cells most likely home and sustain minimal residual disease in vivo. This suggests the use of BZ as an
enhanced strategy to control CML. in particular to prevent relapse of disease, to be considered with caution and to need
further deepening.