Table 1.

Summary of the imaging studies related to the PI3K/Akt/mTOR pathway

Imaging Modality	Agents	Molecular component of PI3K/Akt/mTOR pathway involved and its application in in-vitro/ in-vivo	Reference
PET Imaging	[18F]FDG-PET for evaluating the Gamma Secretase Inhibitor(GSI) activity	ERBB2 (receptor involved in PI3K/ Akt signalling) transgenic mice showed reduced expression of Glut1 on treatment with GSI which correlated with decreased uptake of glucose ([18F]FDG) in tumor.	[73]
	[18F]FLT-PET for evaluating everolimus, the mTOR inhibitor	[18F]-FLT uptake correlated with the level of mTOR inhibition by everolimus in the SKOV3 (cisplatin resistant cells) ovarian tumor model.	[74]
Bioluminescence Imaging	BAR (Akt sensor) for evaluating the activity of the API2 and perifosine	Akt activity is inhibited by Akt inhibitor, API2 and a PI3K inhibitor, perifosine in a time- and dose-dependent manner. Increased bioluminescence activity in in-vitro and in-vivo model indicated Akt inhibition.	[76]
	AST (Akt sensor) for evaluating the activity of perifosine and LY294002	Inhibition of Akt activity by inhibitors like perifosine and LY29004, increased bioluminescence activities in temporal- and dose-dependent manner in in-vitro and in-vivo models.	[79]
Fluorescence Imaging	Use of Intra-vital fluorescence microscopy for evaluating the action of PI3K inhibitor Wortmannin- NBD (Wm-NBD)	Wm-NBD in its active form arrest tumor growth in mice. Intra-vital fluorescence microscopy was used to calculate the concentration that activates neutrophils, required for tumor arrest.	[81]