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