Faculty Bibliography

Repair of DNA strand breaks induced during lymphoid antigen receptor rearrangement involves non-homologous end-joining (NHEJ). We investigated NHEJ in the aetiology of lymphoproliferative disorders (LPDs) and the disease subtypes therein through real-time quantitative RT-PCR gene expression analysis. Lower expression of XRCC6 and MRE11A was observed in all tumours, with higher expression of both XRCC4 and RAD50 observed only in multiple myeloma (MM). Hierarchical clustering enabled tumours to be clearly distinguished from controls, and by morphological sub-type. We postulate this identifies targets worthy of investigation in the genetic predisposition, pathogenesis and prognosis of lymphoid malignancies.

PURPOSE/OBJECTIVE:Myeloma is a clonal malignancy of plasma cells. Poor-prognosis risk is currently identified by clinical and cytogenetic features. However, these indicators do not capture all prognostic information. Gene expression analysis can be used to identify poor-prognosis patients and this can be improved by combination with information about DNA-level changes. EXPERIMENTAL DESIGN/METHODS:Using single nucleotide polymorphism-based gene mapping in combination with global gene expression analysis, we have identified homozygous deletions in genes and networks that are relevant to myeloma pathogenesis and outcome. RESULTS:We identified 170 genes with homozygous deletions and corresponding loss of expression. Deletion within the "cell death" network was overrepresented and cases with these deletions had impaired overall survival. From further analysis of these events, we have generated an expression-based signature associated with shorter survival in 258 patients and confirmed this signature in data from two independent groups totaling 800 patients. We defined a gene expression signature of 97 cell death genes that reflects prognosis and confirmed this in two independent data sets. CONCLUSIONS:We developed a simple 6-gene expression signature from the 97-gene signature that can be used to identify poor-prognosis myeloma in the clinical environment. This signature could form the basis of future trials aimed at improving the outcome of poor-prognosis myeloma.

Immunoglobulin production by myeloma plasma cells depends on the unfolded protein response for protein production and folding. Recent studies have highlighted the importance of IRE1alpha and X box binding protein 1 (XBP1), key members of this pathway, in normal B-plasma cell development. We have determined the gene expression levels of IRE1alpha, XBP1, XBP1UNSPLICED (XBP1u), and XBP1SPLICED (XBP1s) in a series of patients with myeloma and correlated findings with clinical outcome. We show that IRE1alpha and XBP1 are highly expressed and that patients with low XBP1s/u ratios have a significantly better overall survival. XBP1s is an independent prognostic marker and can be used with beta2 microglobulin and t(4;14) to identify a group of patients with a poor outcome. Furthermore, we show the beneficial therapeutic effects of thalidomide in patients with low XBP1s/u ratios. This study highlights the importance of XBP1 in myeloma and its significance as an independent prognostic marker and as a predictor of thalidomide response.

We report the results of a Phase I/II dose escalation study to determine the maximum tolerated dose (MTD) of cyclophosphamide when combined with lenalidomide and dexamethasone in relapsed/refractory myeloma. Thirty-one patients were enrolled in cohorts of 3, at five dose levels of cyclophosphamide to a maximum of 700 mg on days 1 and 8 of a 28-d cycle. Patients received lenalidomide 25 mg days 1-21 and dexamethasone 20 mg orally days 1-4 and 8-11. The MTD was 600 mg cyclophosphamide, days 1 and 8. Grade 3/4 haematological complications occurred in 26% of patients, grade 3/4 infection in 3% (both at 700 mg cyclophosphamide), with thromboembolic complications in 6% of patients. Overall complete response (CR) rate was 29%, very good partial response rate 7% and partial response rate 45% giving an overall response rate of 81%. After 21 months median follow-up, projected 2-year progression-free survival was 56%, with 80% overall survival at 30 months. Ten further patients were treated at MTD with a 40% CR rate. No dose reductions for any study drugs or deaths occurred during cycles 1-9. Lenalidomide, cyclophosphamide and dexamethasone is a safe, effective combination in relapsed myeloma inducing a high response rate, warranting further investigation in phase III trials.