Faculty Bibliography

To define specific pathways important in the multistep transformation process of normal plasma cells (PCs) to monoclonal gammopathy of uncertain significance (MGUS) and multiple myeloma (MM), we have applied microarray analysis to PCs from 5 healthy donors (N), 7 patients with MGUS, and 24 patients with newly diagnosed MM. Unsupervised hierarchical clustering using 125 genes with a large variation across all samples defined 2 groups: N and MGUS/MM. Supervised analysis identified 263 genes differentially expressed between N and MGUS and 380 genes differentially expressed between N and MM, 197 of which were also differentially regulated between N and MGUS. Only 74 genes were differentially expressed between MGUS and MM samples, indicating that the differences between MGUS and MM are smaller than those between N and MM or N and MGUS. Differentially expressed genes included oncogenes/tumor-suppressor genes (LAF4, RB1, and disabled homolog 2), cell-signaling genes (RAS family members, B-cell signaling and NF-kappaB genes), DNA-binding and transcription-factor genes (XBP1, zinc finger proteins, forkhead box, and ring finger proteins), and developmental genes (WNT and SHH pathways). Understanding the molecular pathogenesis of MM by gene expression profiling has demonstrated sequential genetic changes from N to malignant PCs and highlighted important pathways involved in the transformation of MGUS to MM.

Glutathione S-transferase P1 (GSTP1) is a phase 2 drug metabolism enzyme involved in the metabolism and detoxification of a range of chemotherapeutic agents. A single nucleotide polymorphism (Ile105Val) results in a variant enzyme with lower thermal stability and altered catalytic activity. We hypothesized that patients with the less stable variant have a decreased ability to detoxify chemotherapeutic substrates, including melphalan, and have an altered outcome following treatment for multiple myeloma. We have assessed the impact of GSTP1 codon 105 polymorphisms in 222 patients entered into the Medical Research Council (MRC) myeloma VII trial (comparing standard-dose chemotherapy with high-dose therapy). In the standard-dose arm, patients with the variant allele (105Val) had an improved progression-free survival (PFS) (adjusted hazard ratios for PFS were 0.55 for heterozygotes and 0.52 for 105Val homozygotes, compared with 105Ile homozygotes; P for trend =.04); this was supported by a trend to improved overall survival, greater likelihood of entering plateau and shorter time to reach plateau in patients with the 105Val allele. No difference in outcome by genotype was found for patients treated with high-dose therapy. However, the progression-free survival advantage of the high-dose arm was seen only in patients homozygous for 105Ile (P =.008).

The introduction of microarrays offers the opportunity to examine the expression of many thousands of genes in a single experiment. Investigations in leukaemia and lymphoma have led to the identification of a number of subgroups, with a defined gene expression pattern, not previously identified by morphology, cytogenetics or molecular techniques. In many cases these expression patterns can be linked to the tumour cells normal developmental counterpart, and represent distinct disease subgroups with different clinical presentations and outcomes. The technology has also identified genes that may be important in tumour cell biology including key genes in cell proliferation, adhesion, apoptosis, and the development of drug resistance. These early studies demonstrate that genetic microarrays will be useful in classifying haematological malignancies, predicting response to treatment, predicting prognosis, and identifying novel targets for therapy.

BACKGROUND:High-dose therapy with supporting autologous stem-cell transplantation remains a controversial treatment for cancer. In multiple myeloma, first-line regimens incorporating high-dose therapy yield higher remission rates than do conventional-dose treatments, but evidence that this translates into improved survival is limited. METHODS:In this multicenter study, the Medical Research Council Myeloma VII Trial, we randomly assigned 407 patients with previously untreated multiple myeloma who were younger than 65 years of age to receive either standard conventional-dose combination chemotherapy or high-dose therapy and an autologous stem-cell transplant. RESULTS:Among the 401 patients who could be evaluated, the rates of complete response were higher in the intensive-therapy group than in the standard-therapy group (44 percent vs. 8 percent, P<0.001). The rates of partial response were similar (42 percent and 40 percent, respectively; P=0.72), and the rates of minimal response were lower in the intensive-therapy group than in the standard-therapy group (3 percent vs. 18 percent, P<0.001). Intention-to-treat analysis showed a higher rate of overall survival (P=0.04 by the log-rank test) and progression-free survival (P<0.001) in the intensive-therapy group than in the standard-therapy group. As compared with standard therapy, intensive treatment increased median survival by almost 1 year (54.1 months [95 percent confidence interval, 44.9 to 65.2] vs. 42.3 months [95 percent confidence interval, 33.1 to 51.6]). There was a trend toward a greater survival benefit in the group of patients with a poor prognosis, as defined by a high beta2-microglobulin level (more than 8 mg per liter). CONCLUSIONS:High-dose therapy with autologous stem-cell rescue is an effective first-line treatment for patients with multiple myeloma who are younger than 65 years of age.

Osteolytic bone disease is a major cause of morbidity in patients with multiple myeloma. Our understanding of the pathophysiology of multiple myeloma has increased substantially during the past decade. However the underlying mechanisms of bone destruction and the treatments available have, until recently, received relatively little specific attention. In this review, we provide an overview of the RANK/RANKL/osteoprotegerin system; we describe its interaction with other cellular mechanisms, through which malignant plasma cells drive osteolysis, and explain how bisphosphonates can be used to block this action. We also review the supporting evidence for bisphosphonates as the treatment of choice for patients with bone complications related to multiple myeloma, and discuss possible developments for targeted therapy in the future.

Caveolae, specialized flask-shaped lipid rafts on the cell surface, are composed of cholesterol, sphingolipids, and structural proteins termed caveolins; functionally, these plasma membrane microdomains have been implicated in signal transduction and transmembrane transport. In the present study, we examined the role of caveolin-1 in multiple myeloma cells. We show for the first time that caveolin-1, which is usually absent in blood cells, is expressed in multiple myeloma cells. Analysis of myeloma cell-derived plasma membrane fractions shows that caveolin-1 is co-localized with interleukin-6 receptor signal transducing chain gp130 and with insulin-like growth factor-I receptor. Cholesterol depletion by beta-cyclodextrin results in the loss of caveola structure in myeloma cells, as shown by transmission electron microscopy, and loss of caveolin-1 function. Interleukin-6 and insulin-like growth factor-I, growth and survival factors in multiple myeloma, induce caveolin-1 phosphorylation, which is abrogated by pre-treatment with beta-cyclodextrin. Importantly, inhibition of caveolin-1 phosphorylation blocks both interleukin-6-induced protein complex formation with caveolin-1 and downstream activation of the phosphatidylinositol 3-kinase/Akt-1 pathway. beta-Cyclodextrin also blocks insulin-like growth factor-I-induced tyrosine phosphorylation of insulin-responsive substrate-1 and downstream activation of the phosphatidylinositol 3-kinase/Akt-1 pathway. Therefore, cholesterol depletion by beta-cyclodextrin abrogates both interleukin-6- and insulin-like growth factor-I-triggered multiple myeloma cell survival via negative regulation of caveolin-1. Taken together, this study identifies caveolin-1 and other structural membrane components as potential new therapeutic targets in multiple myeloma.