Related Experiment Video

Updated: Jul 12, 2026

Assessing Cellular Target Engagement by SHP2 (PTPN11) Phosphatase Inhibitors
08:45

Assessing Cellular Target Engagement by SHP2 (PTPN11) Phosphatase Inhibitors

Published on: July 17, 2020

A platelet biomarker for assessing phosphoinositide 3-kinase inhibition during cancer chemotherapy

Rita K Bowers1, Philip Marder, Lisa J Green

  • 1Lilly Research Laboratories, Indianapolis, Indiana, USA . bowers_rita_k@lilly.com

Molecular Cancer Therapeutics
|September 4, 2007
PubMed

Insights

Platelet activation, triggered by proteinase-activated receptors (PAR), can indicate phosphoinositide 3-kinase (PI3K) activity. Measuring this platelet response offers a novel biomarker for evaluating PI3K inhibitors in cancer drug development.

Area of Science:

  • Biochemistry
  • Pharmacology
  • Hematology

Background:

  • Proteinase-activated receptors (PARs) initiate signaling cascades in platelets, including phosphoinositide 3-kinase (PI3K) activation.
  • PAR activation leads to conformational changes in platelet fibrinogen receptors, enhancing fibrinogen binding.

Purpose of the Study:

  • To establish a surrogate biomarker assay for assessing PI3K activity in platelets.
  • To evaluate the efficacy of PI3K inhibitors using this novel platelet activation assay.

Main Methods:

  • Flow cytometry was utilized to measure fluorescent ligand and antibody binding, quantifying PAR-induced platelet activation.
  • The assay measured changes in fibrinogen receptor conformation as a readout for PI3K signaling.
  • In vitro and in vivo experiments were conducted using PI3K inhibitors (wortmannin, LY294002) and platelet activation assays.

Main Results:

  • A significant signal window (16- to 45-fold) was observed for PAR-induced platelet activation.
  • PI3K inhibitors wortmannin and LY294002 demonstrated concentration-dependent inhibition of platelet activation.
  • Platelets from wortmannin-treated mice showed inhibited ex vivo activation, correlating with decreased AKT phosphorylation in tumor xenografts.
  • The assay successfully detected PI3K inhibitor effects in blood samples from cancer patients.

Conclusions:

  • Platelet activation measurement serves as a sensitive surrogate biomarker for PI3K activity.
  • This assay can be effectively used in the clinical evaluation of PI3K inhibitors.
  • The findings support the development of novel cancer therapeutics targeting the PI3K pathway.

More Related Videos

Procoagulant Platelet Characterization by Measuring Phosphatidylserine Exposure and Microvesicle Release from Human Purified Platelets05:49

Procoagulant Platelet Characterization by Measuring Phosphatidylserine Exposure and Microvesicle Release from Human Purified Platelets

Published on: November 29, 2024

Related Concept Videos

Phosphoinositides and PIPs01:42

Phosphoinositides and PIPs

Phosphoinositides are a group of phospholipids containing a glycerol backbone with two fatty acid chains and a phosphate attached to a myoinositol sugar ring. The inositol head group extends into the cytoplasm, where it is modified by adding phosphate groups to form phosphatidylinositol phosphates or PIPs.
Different phosphoinositides are synthesized and recruited on the cytosolic face of the plasma membrane. The localization of specific phosphoinositides concentrated in separate membrane...
PI3K/mTOR/AKT Signaling Pathway01:22

PI3K/mTOR/AKT Signaling Pathway

The mammalian target of rapamycin  (mTOR) is a serine/threonine kinase that regulates growth, proliferation, and cell survival in response to hormones, growth factors, or nutrient availability. This kinase exists in two structurally and functionally distinct forms: mTOR complex 1  (mTORC1) and mTOR complex 2  (mTORC2). The first form (mTORC1) is composed of a rapamycin-sensitive Raptor and proline-rich Akt substrate, PRAS40. In contrast,  mTORC2 consists of a rapamycin-insensitive companion...