RET fusion genes, BCR-RET and FGFR1OP-RET, are associated with chronic myelomonocytic leukemia, display sensitivity to Sorafenib, an inhibitor of tyrosine-kinase activity and enhance monocytic differentiation

Myeloproliferative neoplasms are frequently associated with aberrant constitutive tyrosine kinase (TK) activity resulting from point mutations or chimaeric fusion genes, such as BCR ABL1 or JAK2 V617F. We report here for the first time in hematological malignancies, two novel fusion genes involving the TK RET, BCR-RET and FGFR1OP-RET, in chronic myelo monocytic leukemia (CMML) cases. The two RET fusion genes lead to the aberrant activation of RET, are able to transform hematopoietic cells and skew the hematopoietic differentiation program towards the monocytic/macrophage lineage. We also report that the BCR-RET fusion protein is insensitive to Imatinib but sensitive to Sorafenib in vivo. CMML is an hematopoietic malignancy associated with the frequent activation of the RAS pathway. The RET fusion genes seems to constitutively mimic the same signaling pathway than RAS mutations. Overall, the RET fusion genes behaviors in the monocytic lineage underlie the role of the normal RET TK activity during the physiological monocytic differentiation.

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Ballerini P, Struski S, Cresson C, Prade N, Toujani S, Deswarte C, Dobbelstein S, Petit A, Lapillonne H, Gautier EF, Demur C, Lippert E, Pages P, Mansat-De Mas V, Donadieu J, Huguet F, Dastugue N, Broccardo C, Perot C, Delabesse E