The Laboratory of Molecular Hematology, led by IDIVAL researcher Carlos Pipaón, has found while working with G418-resistant stably transfected cells, they realized the neomycin resistance gene (NeoR), which encodes the aminoglycoside-3′-phosphotransferase-IIa [APH(3′)-IIa], also confers resistance to the nucleoside analog fludarabine. Fludarabine is a cytostatic drug widely used in the treatment of hematologic and solid tumors as well as in the conditioning of patients before transplantation of hematopoietic progenitors.
In this research has participated researchers from the IDIVAL Group of Haematologic Neoplasms and Haematopoietic Stem Cells Transplantation, made up of basic researchers and the hematologist Lucrecia Yáñez, and with the collaboration of the group of Elena Cabezón and Iñaki Arechaga from IBBTEC. We present evidence that NeoR-transfected cells do not incorporate fludarabine, thus avoiding DNA damage caused by the drug, evidenced by a lack of FANCD2 monoubiquitination and impaired apoptosis. A screening of other nucleoside analogs revealed that APH(3′)-IIa only protects against ATP purine analogs. Moreover, APH(3′)-IIa ATPase activity is inhibited by fludarabine monophosphate, suggesting that APH(3′)-IIa blocks fludarabine incorporation into DNA by dephosphorylating its active fludarabine triphosphate form. Furthermore, overexpression of the catalytic subunit of the eukaryotic kinase PKA, which is structurally related to APHs, also provides resistance to fludarabine, anticipating its putative utility as a response marker to the drug. Our results preclude the use of Neo marker plasmids in the study of purine analogs and unveils a new resistance mechanism against these chemotherapeuticals.
This paper has been accepted for publication in FASEB Journal. This group is currently conducting a prospective study on allogeneic transplantation patients to investigate whether PKA expression levels can predict the response to fludarabine and thus prevent graft-versus-host disease in a personalized and more efficient way.
