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Ref Type Journal Article
PMID (21668414)
Authors Jamieson S, Flanagan JU, Kolekar S, Buchanan C, Kendall JD, Lee WJ, Rewcastle GW, Denny WA, Singh R, Dickson J, Baguley BC, Shepherd PR
Title A drug targeting only p110α can block phosphoinositide 3-kinase signalling and tumour growth in certain cell types.
Abstract Text Genetic alterations in PI3K (phosphoinositide 3-kinase) signalling are common in cancer and include deletions in PTEN (phosphatase and tensin homologue deleted on chromosome 10), amplifications of PIK3CA and mutations in two distinct regions of the PIK3CA gene. This suggests drugs targeting PI3K, and p110α in particular, might be useful in treating cancers. Broad-spectrum inhibition of PI3K is effective in preventing growth factor signalling and tumour growth, but suitable inhibitors of p110α have not been available to study the effects of inhibiting this isoform alone. In the present study we characterize a novel small molecule, A66, showing the S-enantiomer to be a highly specific and selective p110α inhibitor. Using molecular modelling and biochemical studies, we explain the basis of this selectivity. Using a panel of isoform-selective inhibitors, we show that insulin signalling to Akt/PKB (protein kinase B) is attenuated by the additive effects of inhibiting p110α/p110β/p110δ in all cell lines tested. However, inhibition of p110α alone was sufficient to block insulin signalling to Akt/PKB in certain cell lines. The responsive cell lines all harboured H1047R mutations in PIK3CA and have high levels of p110α and class-Ia PI3K activity. This may explain the increased sensitivity of these cells to p110α inhibitors. We assessed the activation of Akt/PKB and tumour growth in xenograft models and found that tumours derived from two of the responsive cell lines were also responsive to A66 in vivo. These results show that inhibition of p110α alone has the potential to block growth factor signalling and reduce growth in a subset of tumours.


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Molecular Profile Treatment Approach
Gene Name Source Synonyms Protein Domains Gene Description Gene Role
Therapy Name Drugs Efficacy Evidence Clinical Trials
A66 A66 6 0
Drug Name Trade Name Synonyms Drug Classes Drug Description
A66 PIK3CA inhibitor 21 A66 inhibits PIK3CA, preventing the activation of the PI3K signaling pathway and potentially inhibiting tumor cell proliferation (PMID: 21668414, PMID: 28360038).
Gene Variant Impact Protein Effect Variant Description Associated with drug Resistance
Molecular Profile Indication/Tumor Type Response Type Therapy Name Approval Status Evidence Type Efficacy Evidence References
PIK3CA H1047R ovarian cancer sensitive A66 Preclinical - Cell line xenograft Actionable In a preclinical study, A66 delayed tumor growth in an ovarian cancer cell line xenograft model harboring PIK3CA H1047R (PMID: 21668414). 21668414
PIK3CA H1047R Advanced Solid Tumor sensitive A66 Preclinical Actionable In a preclinical study, A66 delayed tumor growth in human tumor xenograft models harboring PIK3CA H1047R mutations (PMID: 21668414). 21668414
PTEN loss glioblastoma resistant A66 Preclinical - Cell line xenograft Actionable In a preclinical study, A66 did not inhibit tumor growth in a PTEN-null cell line xenograft model of glioblastoma (PMID: 21668414). 21668414
PIK3CA E545K Advanced Solid Tumor resistant A66 Preclinical Actionable In a preclinical study, cancer cell lines harboring PIK3CA E545K did not demonstrate sensitivity to A66 in culture, in contrast with cells harboring PIK3CA H1047R (PMID: 21668414). 21668414