British Journal of Haematology

We have used global protein expression analysis to characterize the pathways of dexamethasone‐mediated apoptosis and resistance in myeloma. Analysis of MM.1S cells by two‐dimensional polyacrylamide gel electrophoresis (2D‐PAGE) identified a series of proteins that were up‐ and downregulated following dexamethasone treatment. Downregulated proteins included proteins involved in cell survival and proliferation, whereas upregulated proteins were involved in post‐translational modification, protein folding and trafficking. A comparison with published gene expression studies identified FK binding protein 5 (FKBP5) (also known as FKBP51), a key regulatory component of the Hsp90‐steroid‐receptor complex to be increased at the mRNA and protein level postdexamethasone exposure. Quantitative real time polymerase chain reaction and 2D‐PAGE analysis of the dexamethasone resistant cell line MM.1R demonstrated no increase in FKBP5, consistent with its association with dexamethasone‐mediated apoptosis. Western blot analysis of FKBP5 and other members of the Hsp90‐receptor complex showed an increase in FKBP5 whilst FKBP4 (also known as FKBP52) and Hsp90 expression remained constant. No changes were observed in MM.1R. In conclusion, we demonstrated that following steroid receptor signalling, the cell carries out a number of adaptive responses prior to cell death. Interfering with these adaptive responses may enhance the myeloma killing effect of dexamethasone.

Tumour necrosis factor (TNF)‐related apoptosis‐inducing ligand (TRAIL), a member of the TNF family, which is being developed as an anti‐tumour agent due to its selective toxicity to tumour cells, induces apoptosis by binding to two membrane‐bound receptors, TRAIL‐R1 and TRAIL‐R2. Clinical trials have been initiated with various preparations of TRAIL as well as agonistic monoclonal antibodies to TRAIL‐R1 and TRAIL‐R2. Previously we reported that prior treatment of primary chronic lymphocytic leukaemia (CLL) cells with histone deacetylase inhibitors was required to sensitize CLL cells to TRAIL and, using various receptor‐selective TRAIL mutant ligands, we demonstrated that CLL cells signalled to apoptosis primarily through TRAIL‐R1. Some, but not all, agonistic TRAIL‐receptor antibodies require cross‐linking in order to induce apoptosis. The present study demonstrated that CLL cells can signal to apoptosis through the TRAIL‐R2 receptor, but only after cross‐linking of the agonistic TRAIL‐R2 antibodies, LBY135 and lexatumumab (HGS‐ETR2). In contrast, signalling through TRAIL‐R1 by receptor‐selective ligands or certain agonistic antibodies, such as mapatumumab (HGS‐ETR1), occurs in the absence of cross‐linking. These results further highlight important differences in apoptotic signalling triggered through TRAIL‐R1 and TRAIL‐R2 in primary tumour cells. Such information is clearly important for the rational optimisation of TRAIL therapy in primary lymphoid malignancies, such as CLL.

doi: 10.1111/j.1365-2141.2007.06833.xpmid: 17916100

The transcriptome of the CD34+ cells was determined in a group of 10 patients with the 5q− syndrome using a comprehensive array platform, and was compared with the transcriptome of CD34+ cells from 16 healthy control subjects and 14 patients with refractory anaemia and a normal karyotype. The majority of the genes assigned to the commonly deleted region (CDR) of the 5q− syndrome at 5q31–q32 showed a reduction in expression levels in patients with the 5q− syndrome, consistent with the loss of one allele. Candidate genes showing haploinsufficiency in the 5q− syndrome included the tumour suppressor gene SPARC and RPS14, a component of the 40S ribosomal subunit. Two genes mapping to the CDR, RBM22 and CSNK1A1, showed a >50% reduction in gene expression, consistent with the downregulation of the remaining allele. This study identified several significantly deregulated gene pathways in patients with the 5q− syndrome and gene pathway analysis data supports the proposal that SPARC may play a role in the pathogenesis of the 5q− syndrome. This study suggests that several of the genes mapping to the CDR of the 5q− syndrome play a role in the pathogenesis of this disorder.

Radioimmunotherapy (RIT) is an alternative approach in the treatment of resistant/refractory B‐cell non‐Hodgkin lymphoma (NHL). We performed a feasibility and toxicity pilot study of escalating activity of 90Y‐ibritumomab tiuxetan followed by autologous stem cell transplantation (ASCT). Three activity levels were fixed – 30 MBq/kg (0·8 mCi/kg), 45 MBq/kg (1·2 mCi/kg) and 56 MBq/kg (1·5 mCi/kg) – and 13 patients enrolled. One week before treatment all patients underwent dosimetry. ASCT was performed 13 d after Zevalin® administration. Treatment was well tolerated and all patients engrafted promptly. No differences in terms of haematological toxicities were observed among the three levels, apart from a delayed platelet recovery in heavily pretreated patients receiving 56 MBq/kg. Non‐haematologic toxicity was mainly related to infections and liver toxicity. One patient died 4 months after treatment because of hepatitis C virus reactivation. One patient developed a myelodysplastic syndrome 2 years after treatment. In conclusion, high‐activity Zevalin® with ASCT is feasible and could be safely delivered in elderly and heavily pretreated NHL patients, including those who previously received high‐dose chemotherapy and ASCT. Maximum tolerated dose was not clearly defined according to dosimetry and clinical toxicities, and further studies are needed to confirm the toxicity profile and evaluate efficacy.