Identification and characterisation of small molecule inhibitors of phosphatidylinositol-4-phosphate 5-kinase


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Sylvie Lachmann1, Sarah Griffiths1, Oliver Kern1, James Smith1, Tracey Hunter1, Mar Jimenez Quesada1, Laura Bill1, Jon Roffey1, Elisabeth Trivier1, Robert Wood1, Ai Ching Wong1, Louise Tonkin1, Marc Pittman1, Leon Pang1, Tim Hammonds1, Caroline Foxton1, David R Jones2, Nullin Divecha2, Martin Swarbrick1, Iris Treinies1

1Cancer Research Technology Discovery Laboratories, London, UK, 2Inositide Laboratory, Paterson Institute for Cancer Research, Manchester, UK

Abstract

The cell membrane phospholipid, phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) is the physiological substrate of PI3K and plays a pivotal role in the regulation of a range of cellular processes including actin cytoskeletal organisation, cell proliferation and survival. Cellular PtdIns(4,5)P2 is synthesised by phosphorylation of PtdIns4P on the 5 position of the inositol head group by phosphatidylinositol-4-phosphate 5-kinases (PIP5Ks). Using siRNA technology we have shown that knock down of PIP5Ks in cancer cell lines results in growth inhibition and induction of apoptosis. These data strongly suggest that PtdIns(4,5)P2 is an important survival factor in tumour cells and implicates PIP5K as a novel target for anti-tumour agents.

CRT Discovery Laboratories developed and validated a novel fluorescence polarisation assay for PIP5K activity and has screened for inhibitors of PIP5K. Compounds from this HTS have been validated and two distinct chemical series were chosen to progress into a hit to lead programme. Representatives of both series inhibit PIP5K with nanomolar potencies and show selectivity against a diverse panel of protein kinases. Using siRNA knock down of PIP5K in cancer cell lines we established pSer473 AKT as a surrogate biomarker. PIP5K inhibitors show pAKT biomarker modulation and we can demonstrate emerging SAR. Furthermore the inhibitors induce growth inhibition in a concentration-dependent manner.