Brian Van Ness

Nonrandom recurrent chromosomal abnormalities are ubiquitous in multiple myeloma (MM) and include, among others, translocations of the immunoglobulin heavy chain locus (IgH). IgH translocations in MM result in the up-regulation of oncogenes, and include more commonly t(11;14)(q13;q32), t(4;14)(p16;q32), and t(14;16)(q32;q23). Based on the recurrent nature of these translocations and their finding since the early stages of the plasma cell (PC) disorders, we hypothesized that they would confer biologic and clinical variability. In addition, deletions of 13q14 and 17p13 have also been associated with a shortened survival. We used cytoplasmic Ig-enhanced interphase fluorescent in situ hybridization to detect deletions (13q14 and 17p13.1), and translocations involving IgH in 351 patients treated with conventional chemotherapy entered into the Eastern Cooperative Oncology Group clinical trial E9486/9487. Translocations were frequently unbalanced with loss of one of the derivative chromosomes. The presence of t(4; 14)(p16;q32) (n = 42; 26 vs 45 months, P <.001), t(14;16)(q32;q23) (n = 15; 16 vs 41 months, P =.003), - 17p13 (n = 37; 23 vs 44 months, P =.005), and - 13q14 (n = 176; 35 vs 51 months, P =.028) were associated with shorter survival. A stratification of patients into 3 distinct categories allowed for prognostication: poor prognosis group (t(4;14)(p16;q32), t(14; 16)(q32;q23), and - 17p13), intermediate prognosis (- 13q14), and good prognosis group (all others), with median survivals of 24.7, 42.3, and 50.5 months, respectively (P <.001). This molecular cytogenetic classification identifies patients into poor, intermediate, and good risk categories. More importantly it provides further compelling evidence that MM is composed of subgroups of patients categorized according to their underlying genomic aberrations.

The t(11;14)(q13;q32) results in up-regulation of cyclin D1 and is the most common translocation detected in multiple myeloma, where it is also associated with a lymphoplasmacytic morphology. We performed an interphase fluorescent in situ hybridization (FISH) study to determine the clinical and biologic significance of the abnormality when testing a large cohort of myeloma patients. Bone marrow slides from multiple myeloma patients entered into the Eastern Cooperative Oncology Group phase III clinical trial E9486 and associated laboratory correlative study E9487 were analyzed using interphase FISH combined with immune-fluorescent (cytoplasmic immunoglobulin-FISH) detection of clonal plasma cells. We used FISH probes that hybridize to the 14q32 and 11q13 chromosomal loci. The t(11;14)(q13;q32) was correlated with known biologic and prognostic factors. Of 336 evaluable patients, 53 (16%) had abnormal FISH patterns compatible with the t(11;14)(q13;q32). These patients appeared to be more likely to have a serum monoclonal protein of less than 10 g/L (1 g/dL) (28% vs 15%, P =.029) and a lower plasma cell labeling index (P =.09). More strikingly, patients were less likely to be hyperdiploid by DNA content analysis (n = 251, 14% vs 62%, P <.001). Patients with the t(11;14)(q13;q32) appeared to have better survival and response to treatment, although this did not reach statistical significance. Multiple myeloma with the t(11;14)(q13;q32) is a unique subset of patients, not only characterized by cyclin D1 up-regulation and a lymphoplasmacytic morphology, but is also more frequently associated with small serum monoclonal proteins and is much less likely to be hyperdiploid. These patients do not have a worsened prognosis as previously thought.

One of the distinguishing features of multiple myeloma (MM) is the proliferation of a clonal plasma cell population in the bone marrow (BM). It is of particular interest that the tumor plasma cells appear to be restricted to the microenvironment of the BM and are rarely detected in the peripheral system, yet the disease is found widely disseminated throughout the axial skeleton. Furthermore, isolation of MM tumor cell lines has proven to be quite problematic due to their slow growth rate. These observations have instigated the search for earlier cells in the B cell lineage that are clonally related to the plasma cell tumor and that may represent the growth fraction of the tumor. We used allele-specific oligonucleotides (ASO) derived from the third complementarity determining region of the rearranged tumor immunoglobulin heavy chain gene to detect isotypes clonally related to the plasma cell tumor. By reverse transcribing RNA from the BM with a panel of CH primers (mu, delta, alpha, and gamma), followed by ASO-polymerase chain reaction amplification, we demonstrate the existence of preswitch isotype species that are clonally related to the myeloma tumor. Furthermore, we show that separation of the BM cells into CD45+ and CD38+ cell populations results in a lineage-specific expression of the clonally related RNA molecules, with the C mu and C delta in the CD45+, and C gamma in the CD38+ population. Interestingly, clonally related C alpha transcripts are also derived from the CD45+ fraction. These results confirm the presence of B cell populations clonally related to the plasma cell tumor and are consistent with models that propose the existence of myeloma precursors.