RAS mutations contribute to evolution of chronic myelomonocytic leukemia to the proliferative variant.
OBJECTIVE
The biological and clinical heterogeneity of chronic myelomonocytic leukemia features renders its classification difficult. Moreover, because of the limited knowledge of the mechanisms involved in malignant evolution, chronic myelomonocytic leukemia remains a diagnostic and therapeutic challenge and a poor prognosis disease. We aimed to verify the biological and clinical significance of the discrimination, based on the leukocyte count, between myelodysplastic chronic myelomonocytic leukemia (MD-CMML) and myeloproliferative chronic myelomonocytic leukemia (MP-CMML).


METHODS
Peripheral blood samples from 22 patients classified as MD-CMML and 18 as MP-CMML were collected at different time points during disease course, and patients' clinical characteristics were examined. RAS mutational screening was done by sequencing and, for each substitution identified, a highly selective allele-specific PCR was set up to screen all specimens.


RESULTS
MP-CMML patients showed a significantly poorer survival (P = 0.003) and a higher frequency of RAS mutations (P = 0.033) by sequencing compared with MD-CMML. Overall, five MD-CMML patients progressed to myeloproliferative disease: in two, allele-specific PCR unveiled low levels of the RAS mutations predominating in the myeloproliferative phase at the time of myelodysplastic disease, documenting for the first time the expansion of a RAS mutated clone in concomitance with chronic myelomonocytic leukemia evolution. Moreover, one of the progressed patients harbored the FLT3-ITD and two MP-CMML patients presented with the JAK2 V617F substitution. All these lesions were mutually exclusive.


CONCLUSIONS
Our results strongly suggest RAS mutations to function as a secondary event that contributes to development of the chronic myelomonocytic leukemia variant with the poorer prognosis (MP-CMML) and therefore advise their detection to be implemented in chronic myelomonocytic leukemia diagnostics and monitoring.
Ricci
Clara
C
Fondazione Matarelli, Dipartimento di Farmacologia, Chemioterapia e Tossicologia Medica e Università di Milano, Milan, Italy.
Fermo
Elisa
E
Corti
Stefania
S
Molteni
Mauro
M
Faricciotti
Alessio
A
Cortelezzi
Agostino
A
Lambertenghi Deliliers
Giorgio
G
Beran
Miloslav
M
Onida
Francesco
F
D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D003114:Colony-Forming Units Assay; D018450:Disease Progression; D019143:Evolution, Molecular; D005260:Female; D011905:Genes, ras / Q000235:genetics*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D053614:Janus Kinase 2 / Q000235:genetics; D015477:Leukemia, Myelomonocytic, Chronic / Q000235:genetics* / Q000473:pathology; D008017:Life Expectancy; D008297:Male; D051379:Mice; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D009190:Myelodysplastic Syndromes / Q000235:genetics* / Q000473:pathology; D009196:Myeloproliferative Disorders / Q000235:genetics* / Q000473:pathology; D041681:NIH 3T3 Cells; D011379:Prognosis; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras); D015996:Survival Rate; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics; D018631:ras Proteins / Q000235:genetics*
C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D006160:Guanosine Triphosphate; D051941:fms-Like Tyrosine Kinase 3; D053614:Janus Kinase 2; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins