RIOK3 promotes pancreatic ductal adenocarcinoma cell invasion and metastasis by stabilizing FAK

Zic family member 5 promotes RIO kinase 3 expression to enhance pancreatic cancer survival

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies with few effective therapies available. We previously determined the essential role of Zic family member 5 (ZIC5) in the survival of PDAC cells. In this study, we showed that targeting ZIC5 can effectively shrink PDAC tumors treated with gemcitabine in vivo and investigated the molecular mechanisms involved. When tumor-bearing mice were injected intravenously with ZIC5-targeting small interfering RNA, tumor volume was significantly reduced by gemcitabine treatment. RNA-sequencing analysis was used to identify the genes affected by ZIC5 knockdown. Among these, we selected the genes whose mRNA expression levels correlated with that of ZIC5 in pancreatic cancer and those associated with poor prognosis in patients with pancreatic cancer. Further analysis revealed that RIO kinase 3 (RIOK3) promotes PDAC cell survival, whereas ALDH3B1, PTGES, and TUFT1 contribute to gemcitabine resistance in MiaPaca-2 cells. We identified RIOK3 as a direct target gene of ZIC5 using ChIP and luciferase assays. Furthermore, stable expression of RIOK3 in PANC-1 cells reversed the reduction in cell number following ZIC5 knockdown. These findings highlight RIOK3 as a critical target of ZIC5, which is involved in survival signaling in PDAC cells.

A role for RIO kinases in the crosshair of cancer research and therapy

RIO (right open reading frame) family of kinases including RIOK1, RIOK2 and RIOK3 are known for their role in the ribosomal biogenesis. Dysfunction of RIO kinases have been implicated in malignancies, including acute myeloid leukemia, glioma, breast, colorectal, lung and prostatic adenocarcinoma suggesting RIO kinases as potential targets in cancer. In vitro, in vivo and clinical studies have demonstrated that RIO kinases are overexpressed in various types of cancers suggesting important roles in tumorigenesis, especially in metastasis. In the context of malignancies, RIO kinases are involved in cancer-promoting pathways including AKT/mTOR, RAS, p53 and NF-κB and cell cycle regulation. Here we review the role of RIO kinases in cancer development emphasizing their potential as therapeutic target and encouraging further development and investigation of inhibitors in the context of cancer.

RIOK3 sustains colorectal cancer cell survival under glucose deprivation via an HSP90α-dependent pathway

Glucose oxidation via the pentose phosphate pathway serves as the primary cellular mechanism for generating nicotinamide adenine dinucleotide phosphate (NADPH). The central regions of solid tumors typically experience glucose deficiency, emphasizing the need for sustained NADPH production crucial to tumor cell survival. This study highlights the crucial role of RIOK3 in maintaining NADPH production and colorectal cancer (CRC) cell survival during glucose deficiency. Our findings revealed upregulated RIOK3 expression upon glucose deprivation, with RIOK3 knockout significantly reducing cancer cell survival. Mechanistically, RIOK3 interacts with heat shock protein 90α (HSP90α), a chaperone integral to various cellular processes, thereby facilitating HSP90α binding to isocitrate dehydrogenase 1 (IDH1). This interaction further upregulates IDH1 expression, enhancing NADPH production and preserving redox balance. Furthermore, RIOK3 inhibition had no discernible effect on intracellular NADPH levels and cell death rates in HSP90α-knockdown cells. Collectively, our findings suggest that RIOK3 sustains colon cancer cell survival in low-glucose environments through an HSP90α-dependent pathway. This highlights the significance of the RIOK3-HSP90α-IDH1 cascade, providing insights into potential targeted therapeutic strategies for CRC in metabolic stress conditions.

RIOK3 promotes mTORC1 activation by facilitating SLC7A2-mediated arginine uptake in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a poor prognosis. Reprogramming of amino acid metabolism is one of the characteristics of PDAC, in which arginine metabolism is significantly altered in PDAC cells and is involved in important signaling pathways. Current studies have identified arginine deprivation as a potential strategy for PDAC treatment. In this study, we performed Liquid Chromatograph Mass Spectrometer (LC-MS)-based non-targeted metabolomic analysis on PDAC cell lines with stable Rio Kinase 3 (RIOK3) knockdown and PDAC tissues with different RIOK3 expressions and found that RIOK3 expression was significantly correlated with arginine metabolism in PDAC. Subsequent RNA sequencing (RNA-Seq) and Western blot analysis showed that RIOK3 knockdown significantly inhibited the expression of arginine transporter solute carrier family 7 member 2 (SLC7A2). Further studies revealed that RIOK3 promoted arginine uptake, mechanistic target of rapamycin complex 1 (mTORC1) activation, cell invasion, and metastasis in PDAC cells via SLC7A2. Finally, we found that patients with high expression of both RIOK3 and infiltrating Treg cells had a worse prognosis. Overall, our study found that RIOK3 in PDAC cells promotes arginine uptake and mTORC1 activation through upregulation of SLC7A2 expression, and also provides a new therapeutic target for therapeutic strategies targeting arginine metabolism.