Abstract 5451: Testing a combination of AKT inhibitor (AZD5363) with PARP inhibitor olaparib plus carboplatin in TNBC
Authors: Carlson Jennifer H. , O'Connor Mark J. , Williams Casey , De Pradip , Dey Nandini , Leyland-Jones Brian 
Published: August 2018

Abstract
Background: AKT, a hallmark of cancer in a wide range of solid tumors, is a serine/threonine protein kinase. Inhibition of AKT is known to cause the perturbation of cell proliferation signals and induction of apoptosis in several preclinical in vitro and in vivo models. AKT inhibitor AZD5363 shows promise in different solid tumors in patients with activating mutations of AKT (E17K) (Hyman D. M. et al., JCO 2017), the efficacy is not substantial in patients with PIK3CA mutations (Banerji. U, CCR 2017). PI3K-PTEN-AKT pathway alterations are very common in TNBC. Alterations of AKT1/2/3 (15%), PTEN (29%) and PIK3CA (25%) mediated upregulation of the PI3K pathway are common in TNBC (De et al., 2016; cBioPortal). In our Avera cohort (January 2014-June 2017) of TNBC patients (n=93), we have recorded a total of 16.5 % alteration in AKT1/2/3. We have also identified an integral role of the PI3K-AKT pathway in the DDR-mediated antitumor action of PARP inhibitor in TNBC (De et al., 2014).
Aim: Here we tested the role of genetic background in determining the effectiveness of a combination of AZD5363 with PARP inhibitor Olaparib (O, Lynparza) plus carboplatin (C) in TNBC.
Methods: Using cell line based models of TNBC with defined genetic backgrounds, we studied proliferation (Incucyte) and cell cycle by PI (Accuri). Mechanistic induction of apoptosis was evaluated by live-cell triple immuno-fluorescence (IF) (MitoView Blue+NucView488 Casp3 substrate + CF 594 AnnexinV) with a simultaneous quantification of Annexin (Accuri). Long-term clonogenic response to triple combination was tested using 3D On-Top Matrigel assay.
Result: AZD5363 treatment in PTEN-null SUM149 cells with BRCA1 mutation [2288delT (fs&gt;735X)] responded synergistically to O and C with a dose-dependent increase apoptosis but with limited G1 increase. AZD5363 treatment in PTEN-null MDA-MB468 cells with wt BRCA1 led to an additive effect in slowing proliferation when combined with O and C and a very strong G1 increase but limited induction of apoptosis. AZD5363 as a single agent slowed proliferation and increased G1 in PIK3CA (P539R/H1074R) mutated BT20 cells with a concomitant increase in apoptosis. Mechanistically AZD5363 inhibited pophoyrlation of AKT substrates PRAS40 and GSKβ in TNBC cell lines. As expected KRAS/BRAF mutated (G13D/G464V), BRCA1 wt MDA-MB231 cells showed no effect on either proliferation or apoptosis. Best effect on the inhibition of clonogenic growth (reducing 3D colony formation and size as compared to control over single or double treatment) was recorded in SUM149 compared to MDA468 &gt; BT20, &gt; HCC1937.
Summary: Here we present the effect of the combination of AZD5363 and O plus C in several TNBC cell line based models. Our data demonstrate that maximum effect of the triple combination is seen in PTEN-null cell line harboring BRCA1 mutations followed by PTEN-null cell BRCA1wt. Mechanistic work utlizing AKT1-E17K transfected cells is ongoing.
Citation Format: Jennifer H. Carlson, Mark J. O'Connor, Casey Williams, Pradip De, Nandini Dey, Brian Leyland-Jones. Testing a combination of AKT inhibitor (AZD5363) with PARP inhibitor olaparib plus carboplatin in TNBC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5451.