Introduction: Of all the gynecological malignancies, ovarian cancer (OC) has the highest mortality rate. This can be attributed to the late detection and acquired drug resistance. It metastasizes mainly in the serosal cavities, and produces cancerous cells dispersed in the peritoneal and pleural fluids called effusions. Transforming Growth Factor β (TGFβ) is a family of growth factors that play a significant role in cellular processes. There are three homologous isoforms of TGFβ expressed in humans: TGFβ1-3. These 3 ligands activate 3 transmembrane receptors, TβRI-III. The 3 receptors and the ligand TGF-β2 have different splice variants. TGFβ signaling induces canonical and non-canonical signaling. The Non-canonical pathways consist of a variety of different pathways, including MAP kinase, Rho-like GTPase, and phosphatidylinositol-3-kinase (PI3K)/ AKT pathways.

Aims and methods: Our first aim was to investigate the metastatic role of TGFβ receptor variants. This was accomplished through the creation of specific receptor variant knockouts (KO's) using the CRISPR/Cas9 genome editing system and subsequent metastatic tests. Next we characterized chosen non-canonical pathways and downstream effectors in the CRISPR KO's through Western Blot analysis and qPCR respectively. The Second aim of this study was to characterize the non-canonical pathways In-vivo. Using human tumor tissue samples, we examined the expression and activation of the different pathways via Western Blot analysis and checked for correlation with clinical parameters.

Results: KO cells showed significantly lower migration and invasion capabilities compared to Wild Type (WT) cells. Our results show a decrease in the activation of ERK1/2, JNK1 and JNK2 in the TβRI variant 1 KO in ES-2 cells (p=0.058, p=0.002 and p<0.0001 respectively). The downstream effectors SNAIL and TWIST show significantly higher levels in the KO compared to WT cells. Of the pathways examined, p-AKT was found to be higher in post chemotherapy samples (p=0.029) and JNK1 was higher in effusions from patients with poor chemotherapy response (p=0.045). Site-related findings show that p85 (PI3K), AKT and p-AKT were highest in metastasis, medium in solid ovarian carcinoma and lowest in effusions (p<0.0001, p=0.0024 and p=0.0021 respectively).

Closing statement: These findings provide new insight on the importance of TGFβ‘s role in the progression of OC, and is, as far as we know, is the first study done on the metastatic roles of the receptor variants.

Citation Format: Liora Jacobs Catane, Claes G. Trope, Ben Davidson, Reuven Reich. The noncanonical pathways of transforming growth factor β in ovarian carcinoma [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 2031.