Evaluating surface erythropoietin receptor in multiple myeloma

Impact of Inadequate Methods and Data Analysis on Reproducibility

Failure to reproduce results of articles is recognized, but the causes, and therefore solutions, are not. One possibility is that deficits in quality of the work result in varying or inconclusive results. Erythropoiesis-stimulating agents have been used to treat anemia in patients with cancer, but there are concerns that erythropoiesis-stimulating agents might stimulate Epo receptors on tumor cells (Epo receptor-cancer hypothesis). Articles have been published on the topic, but the data and conclusions conflict, making them suitable for examination of a relationship between quality and reproducibility. Comprehensive literature searches were performed, and 280 relevant articles were identified. Numerous conflicts between and within these articles were apparent. The incidence of faults in quality parameters was high, including absence of adequate controls (90% of articles), inadequate validation of reagents and methods (87% of articles), and inadequate or improper statistical methods (84% of articles) with questionable interpretation of the data (81% of articles). This resulted in false-positive/negative data that varied with the reagents and methods used. The low quality of evidence may explain the poor reproducibility of Epo receptor-cancer articles.

Erythropoietin (EPO)-receptor signaling induces cell death of primary myeloma cells in vitro

Background

Multiple myeloma is an incurable complex disease characterized by clonal proliferation of malignant plasma cells in a hypoxic bone marrow environment. Hypoxia-dependent erythropoietin (EPO)-receptor (EPOR) signaling is central in various cancers, but the relevance of EPOR signaling in multiple myeloma cells has not yet been thoroughly investigated.

Methods

Myeloma cell lines and malignant plasma cells isolated from bone marrow of myeloma patients were used in this study. Transcript levels were analysed by quantitative PCR and cell surface levels of EPOR in primary cells by flow cytometry. Knockdown of EPOR by short interfering RNA was used to show specific EPOR signaling in the myeloma cell line INA-6. Flow cytometry was used to assess viability in primary cells treated with EPO in the presence and absence of neutralizing anti-EPOR antibodies. Gene expression data for total therapy 2 (TT2), total therapy 3A (TT3A) trials and APEX 039 and 040 were retrieved from NIH GEO omnibus and EBI ArrayExpress.

Results

We show that the EPOR is expressed in myeloma cell lines and in primary myeloma cells both at the mRNA and protein level. Exposure to recombinant human EPO (rhEPO) reduced viability of INA-6 myeloma cell line and of primary myeloma cells. This effect could be partially reversed by neutralizing antibodies against EPOR. In INA-6 cells and primary myeloma cells, janus kinase 2 (JAK-2) and extracellular signal regulated kinase 1 and 2 (ERK-1/2) were phosphorylated by rhEPO treatment. Knockdown of EPOR expression in INA-6 cells reduced rhEPO-induced phospo-JAK-2 and phospho-ERK-1/2. Co-cultures of primary myeloma cells with bone marrow-derived stroma cells did not protect the myeloma cells from rhEPO-induced cell death. In four different clinical trials, survival data linked to gene expression analysis indicated that high levels of EPOR mRNA were associated with better survival.

Conclusions

Our results demonstrate for the first time active EPOR signaling in malignant plasma cells. EPO-mediated EPOR signaling reduced the viability of myeloma cell lines and of malignant primary plasma cells in vitro. Our results encourage further studies to investigate the importance of EPO/EPOR in multiple myeloma progression and treatment.

Trial registration

[Trial registration number for Total Therapy (TT) 2: NCT00083551 and TT3: NCT00081939].