|FMS-like tyrosine kinase 3-internal tandem duplication tyrosine kinase inhibitors display a nonoverlapping profile of resistance mutations in vitro.|
Nikolas von Bubnoff,Richard A Engh,Espen Aberg,Jana Sänger,Christian Peschel,Justus Duyster
FMS-like tyrosine kinase 3 (FLT3) inhibitors have shown activity in the treatment of acute myelogenous leukemia (AML). Secondary mutations in target kinases can cause clinical resistance to therapeutic kinase inhibition. We have previously shown that sensitivity toward tyrosine kinase inhibitors varies between different activating FLT3 mutations. We therefore intended to determine whether different FLT3 inhibitors would produce distinct profiles of secondary, FLT3 resistance mutations. Using a cell-based screening approach, we generated FLT3-internal tandem duplication (ITD)-expressing cell lines resistant to the FLT3 inhibitors SU5614, PKC412, and sorafenib. Interestingly, the profile of resistance mutations emerging with SU5614 was limited to exchanges in the second part of the kinase domain (TK2) with exchanges of D835 predominating. In contrast, PKC412 exclusively produced mutations within tyrosine kinase domain 1 (TK1) at position N676. A mutation at N676 recently has been reported in a case of PKC412-resistant AML. TK1 mutations exhibited a differential response to SU5614, sorafenib, and sunitinib but strongly impaired response to PKC412. TK2 exchanges identified with SU5614 were sensitive to PKC412, sunitinib, or sorafenib, with the exception of Y842D, which caused a strong resistance to sorafenib. Of note, sorafenib also produced a highly distinct profile of resistance mutations with no overlap to SU5614 or PKC412, including F691L in TK1 and exchanges at position Y842 of TK2. Thus, different FLT3 kinase inhibitors generate distinct, nonoverlapping resistance profiles. This is in contrast to Bcr-Abl kinase inhibitors such as imatinib, nilotinib, and dasatinib, which display overlapping resistance profiles. Therefore, combinations of FLT3 inhibitors may be useful to prevent FLT3 resistance mutations in the setting of FLT3-ITD-positive AML.
|Biochemical characterization and analysis of the transforming potential of the FLT3/FLK2 receptor tyrosine kinase.|
Maroc, N, et al.
Oncogene, 8: 909-18 (1993)
We recently cloned an additional member of the receptor type tyrosine kinase class III. This new gene, called Flt3 by our group [Rosnet, O., Matteï, M.G., Marchetto, S. & Birnbaum, D. (1991). Genomics, 9, 380-385; Rosnet, O., Marchetto, S., deLapeyriere, O. & Birnbaum, D. (1991). Oncogene, 6, 1641-1650] and Flk2 by others [Matthews, W., Jordan, C.T., Wieg, G.W., Pardoll, D. & Lemischka, I.R. (1991). Cell, 65, 1143-1152] is strongly related to the important developmental genes Kit, Fms and Pdgfr. The murine 3.2-kb full-length cDNA, when introduced into COS-1 cells, shows the expression of two polypeptides with apparent molecular weights of 155 kDa and 132 kDa. Treatment of cells with N-linked glycosylation inhibitors results in the expression of a 110-kDa protein. We have shown that FLT3 contains an intrinsic tyrosine kinase activity. A point mutation in a highly conserved residue within the phosphoryltransferase domain inactivates the catalytic function of this receptor, whereas activation by way of a chimeric molecule between the ligand-binding domain of colony-stimulating factor type 1 (CSF-1) receptor (CSF-1R) and the kinase domain of FLT3 results, in the presence of CSF-1, in the development of the transforming activity of this receptor as shown by anchorage-independent cell growth. Finally, expression analysis of the FLT3 protein shows that, in addition to the hematopoietic system, FLT3 is strongly expressed in neural, gonadal, hepatic and placental tissues in the mouse.