Introduction: Dysregulated alternative splicing is a prominent feature of cancer. The
inhibition and knockdown of the SR splice factor kinase SRPK1 reduces tumour growth in
vivo. As a result several SPRK1 inhibitors are in development including SPHINX, a 3-
(trifluoromethyl)anilide scaffold. The objective of this study was to treat two leukaemic cell
lines with SPHINX in combination with the established cancer drugs azacitidine and
imatinib.
Materials and Methods: We selected two representative cell lines; Kasumi-1, acute
myeloid leukaemia, and K562, BCR-ABL positive chronic myeloid leukaemia. Cells were
treated with SPHINX concentrations up to 10μM, and in combination with azacitidine (up to
1.5 μg/ml, Kasumi-1 cells) and imatinib (up to 20 μg/ml, K562 cells). Cell viability was
determined by counting the proportion of live cells and those undergoing apoptosis
through the detection of activated caspase 3/7. SRPK1 was knocked down with siRNA to
confirm SPHINX results.
Results: The effects of SPHINX were first confirmed by observing reduced levels of
phosphorylated SR proteins. SPHINX significantly reduced cell viability and increased
apoptosis in Kasumi-1 cells, but less prominently in K562 cells. Knockdown of SRPK1 by
RNA interference similarly reduced cell viability. Combining SPHINX with azacitidine
augmented the effect of azacitidine in Kasumi-1 cells. In conclusion, SPHINX reduces
cell viability and increases apoptosis in the acute myeloid leukaemia cell line Kasumi-1, but
less convincingly in the chronic myeloid leukaemia cell line K562.
Conclusion: We suggest that specific types of leukaemia may present an opportunity for
the development of SRPK1-targeted therapies to be used in combination with established
chemotherapeutic drugs.