Haematologica 2003 - Supplements

093
The predominant pathway of transformation to multiple
myeloma is associated with clonal homogeneity in VH
genes at the MGUS stage
Niklas Zojer, MD 1 2, Heinz Ludwig, MD 2, Michael Fiegl,
MD 3, Freda K. Stevenson, DPhil 1 and Surinder S.
Sahota, PhD 1.
1 Tenovus Laboratory, Southampton University Hospitals, UK; 2
1st Department of Internal Medicine with Medical Oncology,
Wilhelminenspital, Vienna, Austria and 3Department of Internal
Medicine, Division of Hematology and Oncology, Innsbruck,
Austria.
The transition of MGUS to multiple myeloma (MM) is now being
evaluated at the molecular level to identify important features of
disease progression. These will impact on clinical evaluation and
treatment. In B-cell tumors, immunoglobulin variable (V) region
gene analysis identifies salient characteristics of the cell of origin
of disease, and it's clonal history following neoplastic arrest to be
identified. In MM, V gene analysis has firmly established
features of extensive somatic mutation with intraclonal
homogeneity of sequence. This is consistent with origins from a
post-follicular cell which arrests at a stage where somatic
mutation is silenced. Intriguingly, C transcripts in typical,
isotype switched MM raise the possibility of a less mature
precursor cell, but clonal stabilty of V gene sequences is still
apparent in this putative cell. In contrast, we showed previously
that in some MGUS cases, there is marked intraclonal variation in
tumor-derived V gene sequences, suggesting at least in these
cases an origin from a less differentiated cell which is able to
continually engage the somatic mutation mechanism. This cell is
likely to be sIg+ve to maintain on-going somatic mutation, which
is generally thought to occur in the germinal center (GC).
We recently reported our findings in tracking progression from
MGUS to MM longitudinally using VH gene analysis in 2 cases.
In each case, the same tumor-clone evolves to malignancy. In 1
case, clonal stability of sequence was observed at both stages of
disease. In the other case, intraclonal heterogeneity in MGUS
confirmed previous findings and at the MM stage on-going
somatic mutation was apparently silenced. However, at this stage
some residual MGUS clones showing heterogeneity could still be
identified, most likely as time to transformation was notably
short. These findings suggested transformation in a cell in which
somatic mutation has ceased, with clonal outgrowth at the MM
stage. Heterogeneity clearly does not correlate with a benign
outcome. We have now expanded this study in a further 3 paired
MGUS/MM cases. In these 3/3 cases, homogeneity of V gene
sequences was observed at both stages of disease. Therefore, in
our analysis of the transition of MGUS to MM, VH genes reveal
that stability of sequences is already evident at the MGUS stage
(4/5 cases), and that this is likely to be the predominant pathway
of progression. Transformation to myeloma here retains
homogeneity. Our data is consistent with clonal outgrowth of a
cell which has transformed, in which cessation of somatic
mutation suggests that sIg may no longer be present. This also
identifies a site in which mutational activity has ceased, such as
the bone marrow. It raises the possibilty of transformation at the
level of a late stage B-cell, such as a plasmablast or MGUS
plasma cell, which acquires the necessary complement of
oncogenic events.
094
MULTIPLE MYELOMA EVOLVING FROM MGUS: HIGH
INCIDENCE OF CHROMOSOME 13q DELETIONS,
WHICH ARE INVARIABLY ASSOCIATED WITH IgH
TRANSLOCATIONS
1,2 H.Kaufmann, 1,2 J.Ackermann, 4 T.Nösslinger, 1,3
H.Gisslinger, 5 R.Wieser, 5 E.Krömer, 6 H.Ludwig, 1,2
J.Drach
1 University Hospital Vienna, Department of Medicine I, 2 Clinical
Division of Oncology, and 3 Division of Hematology and
Hemostaseology; 4 Hanuschspital, 3rd Department of Medicine; 5
University of Vienna, Institute of Medical Biology; 6
Wilhelminenspital, 1st Department of Internal Medicine with
Medical Oncology; Vienna, Austria
Background: Patients with monoclonal gammopathy of
undetermined significance (MGUS) are at increased risk for
progression to multiple myeloma (MM) with an annual actuarial
probability of 1%. Reliable molecular predictors of progression
or parameter indicating a high risk of transformation are still
poorly characterized. We investigated cytogenetic abnormalities
in plasma cells from patients with MM evolving from a
preexisting MGUS (MM post-MGUS) and performed a
comparative analysis between plasma cells obtained at MGUS
and MM-post MGUS stages in the same patients.
Methods: Interphase fluorescence in situ hybridization (FISH)
combined with the detection of cytoplasmic immunoglobulins (cIg-
FISH) was used to determine (a) the incidence of deletion 13q14 (rb-
1 probe), (b) the incidence of translocations at the immunoglobulin
heavy-chain (IgH) locus (14q32; CH and VH break apart probes) and
the type of the translocation [t(11;14)(q13;q32); t(4;14)(p16;q32)],
and (c) the exact percentage of cIg positive plasma cells exhibiting
these abnormalities.
Results: Between 1995 and now, 34 patients with MM post-MGUS
(24 patients with overt MM requiring therapy and 10 patients with
smoldering MM) were identified. Time from the first recognition of
MGUS and progression to MM ranged between 1.4 and 19.7 years
(mean, 8.7 years). Among patients with MM post-MGUS, a deletion
of chromosome 13q14 was detected by cIg-FISH in 14 patients out of
24 treated patients (58.3%) as opposed to 2 patients (20%) with
smoldering MM, 17 of 52 subjects with MGUS (32.7%), and 137 of
318 patients with newly diagnosed MM (43.1%). Evidence for an
IgH translocation was obtained in 15 of 19 evaluable patients with
MM post-MGUS (79%). All 12 patients of this cohort with a deletion
of 13q14 also had an IgH translocation. A t(11;14)(q13;q32) was
present in 5 of the 15 patients with an IgH translocation. Paired
samples of bone marrow plasma cells (both MGUS and MM post-
MGUS specimens) were available in 9 patients to perform a direct
comparison of chromosome 13q14 and 14q32 status. In 2 patients,
probes for 13q14 and 14q32 revealed normal results in MGUS and
MM plasma cells. In 4 patients, the IgH translocation was detected in
both MGUS and MM plasma cells, with a somewhat higher
percentage of cIg abnormal plasma cells in MM. In the 3 remaining
patients, both abnormalities [deletion 13q14 and IgH translocation]
were observed in the paired MGUS and MM samples, again with a
trend towards higher numbers of abnormal cIg positive cells in MM.
Conclusion: Our results indicate that deletions 13q14 are frequent
findings in MM post-MGUS and all patients with this aberration
concomitantly had an IgH translocation. Deletions of 13q14 and
IgH translocations are early events in monoclonal gammopathies
and do not emerge at the time of progression from MGUS to
MM. Presence of both a deletion 13q14 and and an IgH
translocation in MGUS plasma cells may lead to dysregulation of
genes that later contribute to progression to MM.
S130