<i>PIK3CA</i> and <i>AKT1</i> Mutations Have Distinct Effects on Sensitivity to Targeted Pathway Inhibitors in an Isogenic Luminal Breast Cancer Model System

Beaver, Julia A.; Gustin, John P.; Yi, Kyung Hee; Rajpurohit, Anandita; Thomas, Matthew C.; Gilbert, Sarah L.; Rosen, David; Park, Ben Ho; Lauring, Josh

doi:10.1158/1078-0432.ccr-13-0884

Cited by 94 publications

(99 citation statements)

References 33 publications

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“…AKT1 activation in MCF-7 cells is dependent on PIK3CA-E545K mutation (28) and results presented in Figs. 1 and 2 suggest preferential effect of this PIK3CA mutation on AKT1 activation.…”

Section: Discussionmentioning

confidence: 81%

Molecular Insights of Pathways Resulting from Two Common PIK3CA Mutations in Breast Cancer

et al. 2016

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The PI3K pathway is activated in approximately 70% of breast cancers. PIK3CA gene mutations or amplifications that affect the PI3K p110a subunit account for activation of this pathway in 20% to 40% of cases, particularly in estrogen receptor alpha (ERa)-positive breast cancers. AKT family of kinases, AKT1-3, are the downstream targets of PI3K and these kinases activate ERa. Although several inhibitors of PI3K have been developed, none has proven effective in the clinic, partly due to an incomplete understanding of the selective routing of PI3K signaling to specific AKT isoforms. Accordingly, we investigated in this study the contribution of specific AKT isoforms in connecting PI3K activation to ERa signaling, and we also assessed the utility of using the components of PI3K-AKT isoform-ERa signaling axis as predictive biomarkers of response to PI3K inhibitors. Using a variety of physiologically relevant model systems with defined natural or knock-in PIK3CA mutations and/or PI3K hyperactivation, we show that PIK3CA-E545K mutations (found in $20% of PIK3CA-mutant breast cancers), but not PIK3CA-H1047R mutations (found in 55% of PIK3CA-mutant breast cancers), preferentially activate AKT1. Our findings argue that AKT1 signaling is needed to respond to estrogen and PI3K inhibitors in breast cancer cells with PIK3CA-E545K mutation, but not in breast cancer cells with other PIK3CA mutations. This study offers evidence that personalizing treatment of ER-positive breast cancers to PI3K inhibitor therapy may benefit from an analysis of PIK3CA-E545K-AKT1-estrogen signaling pathways. Cancer Res; 76(13); 3989-4001. Ó2016 AACR.

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“…AKT1 activation in MCF-7 cells is dependent on PIK3CA-E545K mutation (28) and results presented in Figs. 1 and 2 suggest preferential effect of this PIK3CA mutation on AKT1 activation.…”

Section: Discussionmentioning

confidence: 81%

Molecular Insights of Pathways Resulting from Two Common PIK3CA Mutations in Breast Cancer

et al. 2016

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“…Whatever the explanation, AKT1 E17K clearly has the potential to confer two properties of oncogenic transformation on recipient breast epithelial cells: the ability to grow anchorage independently in semisolid medium and the ability to form mammary lesions in immunodeficient rodents. Moreover, recent data have shown that knock-in of AKT1 E17K into isogenic MCF-7 cells that have previously been depleted of their endogenous PIK3CA E545K mutation restored proliferation and tumor growth (16).…”

Section: Discussionmentioning

confidence: 99%

“…The E17K mutation has been shown to constitutively activate AKT1 by increased localization to the plasma membrane, where it stimulates downstream signaling and can transform Rat1 fibroblasts and induce leukemia in mice (15). Although knock-in of AKT1 E17K into isogenic MCF-7 breast cancer cells depleted of endogenous PIK3CA E545K restored proliferation in vitro and tumor growth in vivo (16), knock-in of E17K into the AKT1 gene of nontransformed MCF10A mammary epithelial cells had minimal phenotypic consequences and did not recapitulate the transforming properties induced by somatic cell knock in of PIK3CA hotspot mutations (17). In addition, the consequences of directly inhibiting this target in endogenous models of breast and urinary bladder cancer have not been reported.…”

Section: Introductionmentioning

confidence: 99%

Tumors with AKT1E17K Mutations Are Rational Targets for Single Agent or Combination Therapy with AKT Inhibitors

Davies

Guan²,

Logié

et al. 2015

Molecular Cancer Therapeutics

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AKT1E17K mutations occur at low frequency in a variety of solid tumors, including those of the breast and urinary bladder. Although this mutation has been shown to transform rodent cells in culture, it was found to be less oncogenic than PIK3CA mutations in breast epithelial cells. Moreover, the therapeutic potential of AKT inhibitors in human tumors with an endogenous AKT1 E17K mutation is not known. Expression of exogenous copies of AKT1 E17K in MCF10A breast epithelial cells increased phosphorylation of AKT and its substrates, induced colony formation in soft agar, and formation of lesions in the mammary fat pad of immunodeficient mice. These effects were inhibited by the allosteric and catalytic AKT inhibitors MK-2206 and AZD5363, respectively. Both AKT inhibitors caused highly significant growth inhibition of breast cancer explant models with AKT1 E17K mutation. Furthermore, in a phase I clinical study, the catalytic Akt inhibitor AZD5363 induced partial responses in patients with breast and ovarian cancer with tumors containing AKT1 E17K mutations. In MGH-U3 bladder cancer xenografts, which contain both AKT1 E17K and FGFR3 Y373C mutations, AZD5363 monotherapy did not significantly reduce tumor growth, but tumor regression was observed in combination with the FGFR inhibitor AZD4547. The data show that tumors with AKT1 E17K mutations are rational therapeutic targets for AKT inhibitors, although combinations with other targeted agents may be required where activating oncogenic mutations of other proteins are present in the same tumor.

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“…Interestingly, both MCF7-corrected and MCF7-corrected + V777L cells had dramatically reduced AKT phosphorylation. Although it has been shown that the absence of PIK3CA mutations in MCF7 cells lowers activation of the PI3 kinase/AKT pathway (19), it was unexpected that isolated activation of HER2 signaling via the V777L mutation MCF-10A Targeted WT 1 Targeted WT 2 Targeted WT 3 G309A S310F L755S I767M V777L Y835F did not lead to any discernible increase in AKT phosphorylation. This result, along with the concurrent increases in ERK phosphorylation, again suggests that V777L HER2 preferentially activates the MAP kinase signaling pathway rather than the PI3 kinase/AKT signaling pathway.…”

Section: Her2 V777l Mutation Increases Her2 Signaling Pathway Activatmentioning

confidence: 99%

“…Numerous studies have implicated PIK3CA mutations in transformation and activation of the PI3 kinase/AKT pathway (17,20). To test this hypothesis, we used genome editing to introduce the HER2 V777L mutation into MCF7 cells that had previously undergone gene targeting to restore the PIK3CA alleles to wild type (referred to as MCF7 corrected) (19). The resulting cells have three wildtype copies of PIK3CA and a heterozygous HER2 V777L mutation (referred to as MCF7 corrected + V777L).…”

Section: Her2 V777l Mutation Increases Her2 Signaling Pathway Activatmentioning

confidence: 99%

HER2 missense mutations have distinct effects on oncogenic signaling and migration

Zabransky

Yankaskas

Cochran

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Recurrent human epidermal growth factor receptor 2 (HER2) missense mutations have been reported in human cancers. These mutations occur primarily in the absence of HER2 gene amplification such that most HER2-mutant tumors are classified as "negative" by FISH or immunohistochemistry assays. It remains unclear whether nonamplified HER2 missense mutations are oncogenic and whether they are targets for HER2-directed therapies that are currently approved for the treatment of HER2 gene-amplified breast cancers. Here we functionally characterize HER2 kinase and extracellular domain mutations through gene editing of the endogenous loci in HER2 nonamplified human breast epithelial cells. In in vitro and in vivo assays, the majority of HER2 missense mutations do not impart detectable oncogenic changes. However, the HER2 V777L mutation increased biochemical pathway activation and, in the context of a PIK3CA mutation, enhanced migratory features in vitro. However, the V777L mutation did not alter in vivo tumorigenicity or sensitivity to HER2-directed therapies in proliferation assays. Our results suggest the oncogenicity and potential targeting of HER2 missense mutations should be considered in the context of cooperating genetic alterations and provide previously unidentified insights into functional analysis of HER2 mutations and strategies to target them. A great success in the treatment of breast cancer has come from the identification of human epidermal growth factor receptor 2 (HER2)/Neu (ERBB2) amplification/overexpression as a targetable driver in ∼20% of breast cancers (1). HER2 is a member of the ErbB family of transmembrane receptor tyrosine kinases, which includes the epidermal growth factor receptor (EGFR/ErbB1), HER3 (ErbB3), and HER4 (ErbB4) (2). Activation of ErbB signaling causes receptor tyrosine autophosphorylation and induces interactions with cytoplasmic signal transduction partners that promote a wide variety of cellular processes including proliferation, motility, and escape from apoptosis. In addition to their key role in normal cellular growth and maintenance, the dysregulation of ErbB receptors has been extensively implicated in the development of numerous cancers (1).Whereas overexpression or amplification of HER2 has been well described to deregulate ErbB signaling, cancer genome sequencing studies have demonstrated that somatic point mutations in the HER2 gene occur in a number of cancers, including 2-4% of breast cancers (3-6). Importantly, these mutations are most often found in patients as single copies without amplification/overexpression of HER2 (HER2-"negative" breast cancers), though HER2 protein expression is often still present. Overexpression studies have implicated a number of these mutations as activating and oncogenic (4, 7-9). Additionally, one mutation, L755S, has been described to be associated with lapatinib resistance when overexpressed (4, 10).Past studies comparing overexpression of a mutant cDNA to single nucleotide knockin of mutant oncogenes have shown dramatic differences ...

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PIK3CA and AKT1 Mutations Have Distinct Effects on Sensitivity to Targeted Pathway Inhibitors in an Isogenic Luminal Breast Cancer Model System

Cited by 94 publications

References 33 publications

Molecular Insights of Pathways Resulting from Two Common PIK3CA Mutations in Breast Cancer

Molecular Insights of Pathways Resulting from Two Common PIK3CA Mutations in Breast Cancer

Tumors with AKT1E17K Mutations Are Rational Targets for Single Agent or Combination Therapy with AKT Inhibitors

HER2 missense mutations have distinct effects on oncogenic signaling and migration

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