[Does multiple myeloma response to induction therapy depend on plasma cell IL6 receptor gene expression?]. / L'expression de l'IL6-r par les plasmocytes influe-t-elle la réponse au traitement d'induction au cours du myélome multiple ?

BACKGROUND: Interleukine 6 (IL-6) is the most important cytokine involved in malignant plasma cells growth and survival. AIM: To analyse bone marrow plasma cells IL6 receptor gene expression in both multiple myeloma patients at diagnosis and healthy bone marrow donors. METHODS: Clinical and biological patients' features and responses to Dexamethasone-Thalidomide induction therapy were gathered. 47 patients and 16 case controls were analyzed: Bone marrow plasma cells were isolated; and IL6 receptor gene expression was quantified using Taqman quantitative PCr technology and 2-ΔCT formula. RESULTS: Quantitative and qualitative IL6 receptor gene expression were negatively correlated with the degree of response to therapy (p= 0.02). In this study, plasma cells IL6 receptor gene expression seems to be decisive in predicting the response to treatment. CONCLUSION: Understanding the mechanisms involved in plasma cells IL6 receptor gene expression may offer a better appreciation of the physiopathologic and anti-oncogenic ways of drug resistance in multiple myeloma and consequently the discovery of new specific drugs.

Abnormal repression of SHP-1, SHP-2 and SOCS-1 transcription sustains the activation of the JAK/STAT3 pathway and the progression of the disease in multiple myeloma.

Sustained activation of JAK/STAT3 signaling pathway is classically described in Multiple Myeloma (MM). One explanation could be the silencing of the JAK/STAT suppressor genes, through the hypermethylation of SHP-1 and SOCS-1, previously demonstrated in MM cell lines or in whole bone marrow aspirates. The link between such suppressor gene silencing and the degree of bone marrow invasion or the treatment response has not been evaluated in depth. Using real-time RT-PCR, we studied the expression profile of three JAK/STAT suppressor genes: SHP-1, SHP-2 and SOCS-1 in plasma cells freshly isolated from the bone marrows of MM patients and healthy controls. Our data demonstrated an abnormal repression of such genes in malignant plasma cells and revealed a significant correlation between such defects and the sustained activation of the JAK/STAT3 pathway during MM. The repressed expression of SHP-1 and SHP-2 correlated significantly with a high initial degree of bone marrow infiltration but was, unexpectedly, associated with a better response to the induction therapy. Collectively, our data provide new evidences that substantiate the contribution of JAK/STAT suppressor genes in the pathogenesis of MM. They also highlight the possibility that the decreased gene expression of SHP-1 and SHP-2 could be of interest as a new predictive factor of a favorable treatment response, and suggest new potential mechanisms of action of the therapeutic molecules. Whether such defect helps the progression of the disease from monoclonal gammopathy of unknown significance to MM remains, however, to be determined.