Ral Gtpase-Activating Protein Regulates The Malignancy Of Pancreatic Ductal Adenocarcinoma

The small GTPases RalA and RalB are members of the Ras family and activated downstream of Ras. Ral proteins are found in GTP-bound active and GDP-bound inactive forms. The activation process is executed by guanine nucleotide exchange factors, while inactivation is mediated by GTPase-activating proteins (GAPs). RalGAPs are complexes that consist of a catalytic alpha 1 or alpha 2 subunit together with a common beta subunit. Several reports implicate the importance of Ral in pancreatic ductal adenocarcinoma (PDAC). However, there are few reports on the relationship between levels of RalGAP expression and malignancy in PDAC. We generated RalGAP beta-deficient PDAC cells by CRISPR-Cas9 genome editing to investigate how increased Ral activity affects malignant phenotypes of PDAC cells. RalGAP beta-deficient PDAC cells exhibited several-fold higher Ral activity relative to control cells. They had a high migratory and invasive capacity. The RalGAP beta-deficient cells grew more rapidly than control cells when injected subcutaneously into nude mice. When injected into the spleen, the RalGAP beta-deficient cells formed larger splenic tumors with more liver metastases, and unlike controls, they disseminated into the abdominal cavity. These results indicate that RalGAP beta deficiency in PDAC cells contributes to high activities of RalA and RalB, leading to enhanced cell migration and invasion in vitro, and tumor growth and metastasis in vivo.