Abstract 3451: Testing signaling algorithm in platinum-resistant ovarian carcinomas: A simultaneous inhibition of RAS-RAF and cell-cycle pathways signals by trametinib with paclitaxel or ribociclib/abemaciclib

INTRODUCTION: Ovarian cancer (OC) frequently harbors genetic or epigenetic alterations that aberrantly activate CDK4/CDK6 pathway (Nam & Kim. Int J Gynecol Cancer 2008). Ribociclib (R) is being used in Phase I clinical trial in metastatic epithelial ovarian cancer (NCT03294694). CDK4/6 inhibitor, abemaciclib (A) is effective in KRAS mutant NSCLC. Platinum-taxol chemotherapy is the part of the standard of care for epithelial OC patients. However, acquired resistance to the platinum therapy can poorly affect prognosis (Jayson et al., Lancet, 2014; Sonego et al., Sci. REP. 2017). Additionally, the recurrent resistant EOCs almost invariably grow as metastatic disease (Jayson et al., Lancet, 2014). AIM: We interrogated the genomic alterations of the RAS-RAF (RR) and the cell-cycle (CC) pathways to generate a signaling algorithm in precision medicine for testing rational combinations of RR pathway inhibitor, Trametinib (T) with Paclitaxel (P) or CDK4/6 inhibitor (R/A) in platinum-resistant OC. METHODS: We analyzed genomic alterations (FoundationOne) of 90 tumor samples from 75 consecutive OC patients (Avera Cancer Institute; ‘14-‘17). The genomic changes in FoundationOne results were resolved into RR and CC pathways. Parental and cis-platin resistant RAF mutated A2780 iso-genic cell lines were used to study time-dependent effect of T (MEK1/2 inhibitor) and A/R (CDK4/6 inhibitor), single or in combination with P on (1) proliferative signals (WB), (2) cell cycle (Flowcytometry), (3) live-dead staining, (4) apoptosis (Flowcytometry; TMRE-based Mitochondrial potential; Triple IF by MitoView Blue+NucView488 Casp3 substrate + CF 594 AnnexinV) and (5) 3D clonogenic growth. RESULTS: 100 genes were altered in a total of 87% metastatic and 11% adjuvant tumors with a predominant histological type of high grade serous (58%). 7 genes including NF1> KRAS>MAP3K1>NF2>BRAF>MAP2K4>NRAS of the RR pathway were altered in 33% of tumors. 10 CC pathway genes including CCNE1, CDKN2A/B, in addition to TP53 and MYC were altered. We observed that 20-24% tumors had co-alterations of the two pathways and importantly, all tumors with co-alterations were metastatic. Although treatment of R and P as single agent significantly increased pRSK in resistant cell line at 6 hours, a combination of T + P or T + A/R was effective in inhibiting proliferative signals and inducing apoptosis abrogating downstream pERK and pRSK. A combination of T+P was most effective in inducing cl-casp3 at 24 hours. 3D ON-TOP assay for 10 days demonstrated a significant blockade of clonogenic growth with T+P and T+R in resistant cells. CONCLUSION: Plotting an in-depth information about co-alterations of genes of the RR and the CC pathway on the landscape of cell signaling is a useful tool to crack the code of cis-platin-resistance for improved treatment options. Citation Format: Nandini Dey, Casey Williams, Kirstin Williams, Jessica Klein, Jennifer H. Carlson, David Starks, Luis Rojas Espaillat, Pradip De, Brian Leyland Jones. Testing signaling algorithm in platinum-resistant ovarian carcinomas: A simultaneous inhibition of RAS-RAF and cell-cycle pathways signals by trametinib with paclitaxel or ribociclib/abemaciclib [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 3451.