[Genetic abnormalities in multiple myeloma: role in oncogenesis and impact on survival]. / Anomalies génétiques dans le myélome: rôle dans l'oncogenèse et implications pronostiques.

PURPOSE: Recent development of interphase fluorescence in situ hybridization (FISH) allows analysis on non-proliferant plasma cells. We describe the most frequent genetic abnormalities in multiple myeloma and their prognostic value. CURRENT KNOWLEDGE AND KEY POINTS: Most frequent genetic abnormalities are illegitimate rearrangements involving the IGH gene at 14q32 (60% of patients), hyperdiploidy (50 to 60% of patients), chromosome 13 deletion (40 to -50% of patients), chromosome 1q gain (30 to -40% of patients) chromosome 17 deletion (10% of patients). Some of these genetics abnormalities are observed in monoclonal gammopathy of undetermined significance (MGUS), a pre-malignant state. t(4;14) and t(14;16) translocations and chromosome 17 deletion negatively impact the overall survival. Patients with these genomic aberrations should be treated with specific treatment. FUTURE PROSPECTS AND PROJECTS: Identification of genetic abnormalities is important for evaluation of prognosis and treatment protocol in multiple myeloma.

Genetic heterogeneity in multiple myeloma.

In the past decade, many progresses have been made in our knowledge of the genetics of multiple myeloma. The use of molecular cytogenetic techniques has led to the identification of several recurrent (cyto)genetic abnormalities, representing either prognostic markers, or novel therapeutic targets. More global analyses of this genetic heterogeneity using expression array technologies should further extend our understanding of the disease, hopefully enabling some improvements in the treatment of the patients. The goal of this minireview is to summarize these recent advances.

Ploidy, as detected by fluorescence in situ hybridization, defines different subgroups in multiple myeloma.

Ploidy appears as an important parameter in both the biology and the clinical evolution of multiple myeloma. However, its evaluation requires either a successful karyotyping (obtained in 30% of the patients) or a DNA index calculation by flow cytometry (not routinely performed in myeloma). We validated a novel method based on interphase fluorescence in situ hybridization that can be utilitized to analyze almost all the patients. The method was very specific and sensitive for the detection of hyperdiploidy. Extended studies showed that most recurrent 14q32 translocations occur in nonhyperdiploid clones, and that deletions of chromosome 13 were less frequently observed in hyperdiploid clones (48 vs 66%). Further large studies are ongoing to evaluate the prognostic value of ploidy in myeloma.

Minor clone provides a reservoir for relapse in multiple myeloma.

Recent studies have provided direct evidence for genetic variegation in subclones for various cancer types. However, little is known about subclonal evolutionary processes according to treatment and subsequent relapse in multiple myeloma (MM). This issue was addressed in a cohort of 24 MM patients treated either with conventional chemotherapy or with the proteasome inhibitor, bortezomib. As MM is a highly heterogeneous disease associated with a large number of chromosomal abnormalities, a subset of secondary genetic events that seem to reflect progression, 1q21 gain, NF-κB-activating mutations, RB1 and TP53 deletions, was examined. By using high-resolution single-nucleotide polymorphism arrays, subclones were identified with nonlinear complex evolutionary histories. Such reordering of the spectrum of genetic lesions, identified in a third of MM patients during therapy, is likely to reflect the selection of genetically distinct subclones, not initially competitive against the dominant population but which survived chemotherapy, thrived and acquired new anomalies. In addition, the emergence of minor subclones at relapse appeared to be significantly associated with bortezomib treatment. These data support the idea that new strategies for future clinical trials in MM should combine targeted therapy and subpopulations' control to eradicate all myeloma subclones in order to obtain long-term remission.

A new Leukemia Prognostic Scoring System for refractory/relapsed adult acute myelogeneous leukaemia patients: a GOELAMS study.

A simplified prognostic score is presented based on the multivariate analysis of 138 refractory/relapsed acute myeloid leukaemia (AML) patients (median age 55 years, range: 19-70) receiving a combination of intensive chemotherapy+Gemtuzumab as salvage regimen. Overall, 2-year event-free survival (EFS) and overall survival (OS) were 29±4% and 36±4%, respectively. Disease status (relapse <12 months, including refractory patients), FLT3-ITD-positive status and high-risk cytogenetics were the three strongest independent adverse prognostic factors for OS and EFS in this series. We then defined three subgroups with striking different outcomes at 2 years: no adverse factor (favourable, N=36): OS 58%, EFS 45%; one adverse factor (intermediate, N=54): OS 37%, EFS 31%; two or three adverse factors (poor, N=43): OS 12%, EFS 12% (P<10(-4), P=0.001). This new simplified Leukemia Prognostic Scoring System was then validated on an independent cohort of 111 refractory/relapsed AML patients. This new simplified prognostic score, using three clinical and biological parameters routinely applied, allow to discriminate around two third of the patients who should benefit from a salvage intensive regimen in the setting of refractory/relapsed AML patients. The other one third of the patients should receive investigational therapy.

Prevalence of CFTR mutations in hypertrypsinaemia detected through neonatal screening for cystic fibrosis.

Nowadays, most of the neonatal screening programs for cystic fibrosis (CF) combine the assay of immunoreactive trypsinogen (IRT) with the analysis of the most common mutations of the CFTR gene. The efficiency of this strategy is now well established, but the identification of heterozygotes among neonates with increased IRT is perceived as a drawback. We proposed to assess the heterozygosity frequency among the children with hypertrypsinaemia detected through the CF screening program implemented in Brittany (France) 10 years ago, to describe the CFTR mutations detected in them and to determine the frequency of the IVS8-5T variant. The molecular analysis relies, in our protocol, on the systematic analysis of three exons of the gene (7-10-11). A total of 160,019 babies were screened for CF in western Brittany between 1992 and 1998. Of the 1964 newborns with increased IRT (1.2%), 60 were CF and 213 were carriers. Heterozygosity frequency was 12.8%), i.e. 3 times greater than in the general population (3.9%; p < 10(-6)), Variability of mutations detected in carriers was greater than in CF children (21 mutations versus 10) and a high proportion of mild mutations or variants (A349V, R297Q, R347H, V317A, G544S, R553G, etc) was observed in carriers. The allelic frequency of the 5T (5.6%) was not significantly increased in this cohort. This study is consistent with previous ones in finding a significantly higher rate of heterozygotes than expected among neonates with hypertrypsinaemia. The strategy of screening used here allows to highlight the variability of mutations detected in heterozygotes and to show that severe mutations, as well as mild mutations, have been observed in neonates with hypertrypsinaemia. If there is no doubt that neonatal hypertrypsinaemia is associated with an elevated frequency of carriers, the underlying mechanisms remain obscure.