Abstract 4683: Suppression of ARL6ip1 inhibits malignant phenotypes of human colorectal cancer cells in vivo and > in situ

Abstract

Abstract Introduction: Conophylline is an alkaloid isolated from the leaves of the Thai plant, Ervatamia microphylla. We isolated conophylline as an inhibitor of K-Ras functions and an activator of pancreatic β-cell differentiation. It ameliorates various disease models in animals, including cancer, diabetes mellitus, NASH, and hepatic cirrhosis. On the other hand, its molecular target was determined to be ADP-ribosylation factor-like 6-interacting protein 1 (ARL6ip1) using a conophylline-biotin conjugate. ARL6ip1 is located in the endoplasmic reticulum (ER) membrane, and conophylline binds to the cytoplasmic portion of ARL6ip1. Known functions of ARL6ip1 include inhibition of apoptosis, inhibition of glutamate transporter, and modulation of the ER structure. Previously, we knocked out ARL6ip1 in human colon carcinoma cells by CRISPR-Cas9 and found that either deletion of ARL6ip1 or addition of conophylline inhibited migration, invasion and tumorigenicity in cultured cancer cells. In the present research we have studied the in vivo anticancer effect of conophylline and ARL6ip1 knockout, and the mechanism of anticancer activity in cultured cells. Materials and Methods: Conophylline was isolated from the leaves of Ervatamia microphylla. We employed HCT116 and DLD1 cell lines as human colorectal cancer cells. Cellular migration was measured by a wound-healing assay. The activity of Akt was measured by the phospho-Akt antibody. BALB/cSlc-nu/nu mice were used for the animal experiment. Results: Colon adenocarcinoma tissue microarray comparing tumor and adjacent normal tissues revealed that ARL6ip1 expression was significantly higher in cancer than in normal tissues. Intraperitoneal administration of conophylline and knockout of ARL6ip1 both inhibited the growth of HCT116 in mice. Neither influenced the bodyweight of animals. Conophylline and deletion of ARL6ip1 both inhibited the migration. Rescue of ARL6ip1 canceled the effect of ARL6ip1 deletion on migration in HCT116 and DLD1 cells. As the mechanism, either conophylline or ARL6ip1 knockout inhibited the Akt activity, which was canceled by the rescue of ARL6ip1 in both cell lines. Conclusion: ARL6ip1 was found to be highly expressed in the tumor tissue in colorectal cancer. CRISPR-Cas9 knockout of ARL6ip1 showed a similar anticancer activity as treatment with conophylline in the animal experiment. It is likely that the anticancer activity of conophylline would be mediated by Akt. Thus, ARL6ip1 would be a useful molecular target for the treatment of cancer. Citation Format: Yinzhi Lin, Sivasundaram Karnan, Hideaki Ito, Kazuo Umezawa. Suppression of ARL6ip1 inhibits malignant phenotypes of human colorectal cancer cells in vivo and > in situ [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4683.