Endoplasmic Reticulum Stress and Resistance to Treatments in Ph-negative Myeloproliferative Neoplasms

Inclusion Criteria: * ET or PV patients diagnosed before acceleration phase and treated by hydroxyurea with a follow up period of at least 6 months following treatment start. * Diagnosis criteria of PV : * WHO criteria of PV with : * Acquired JAK2V617F mutation \> 5% * Absence of evident cause of secondary polycythemia * Diagnosis criteria of ET : * Platelet count \> 450 G/L * Absence of PV or Chronic Myeloid Leukemia * Bone marrow biopsy preferred but not necessary in absence of reactional causes (CRP and ferritin levels normal) and/or presence of acquired JAK2V617F, CALR exon 9 or MPL exon 10 * Availability of RNA sample of total leukocytes before start of treatment. Exclusion Criteria: In absence of clonality marker, presence of secondary cause of : * Thrombocytosis : * Inflammatory syndrom (CRP or SV increased) * Iron deficiency (decreased ferritin level or increased soluble transferrin receptor level) * Polycythemia : * Increased or normal level of EPO in context of : * Hypoxia, respiratory insufficiency * Sleep apnea syndrome * Hyperaffin hemoglobin * Absence of treatment by hydroxyurea * Treatment by anagrelide, P32, pipobroman, interferon without subsequent hydroxyurea treatment. * Concommitant treatment by other cancer chemotherapy (in a context of solid cancer for example). * Diagnostic during transformation to acute leukemia * Treatment by hydroxyurea during less than 6 months * Bad observance of the cytotoxic treatment