Investigate how RHOA Tyr42Cys mutation drives gastric cancer

Dr Choi, Jeeeun   (Principal Investigator (PI))

36

2022-06-01

38760

Investigate how RHOA Tyr42Cys mutation drives gastric cancer

gastric cancer, mutation, RHOA gene, Tyr42Cys

Cancer

PDFS2223-7S04

RGC Postdoctoral Fellowship Scheme

2022

On-going

• Recurrent nonsynonymous mutation of the RHOA gene (RHOA A125G, encoding Tyr42Cys) has been identified by whole-genome sequencing in diffuse-subtype gastric cancer patients (Wang et al., 2014 & Kakiuchi et al., 2014). However, its functional characterization, downstream targets, and pathophysiological mechanisms in gastric cancer have not been thoroughly investigated. • Diffuse-subtype gastric cancer presents a poor prognosis and higher metastatic potential than the other subtypes in gastric cancer (Cutsem et al., 2016). It remains challenging to target these cancer cells mainly because little is known about molecular and cellular mechanisms and very high stroma content. Currently, the first treatment option for these gastric cancer patients is a combination of chemotherapy and radiation therapy, both of which are non-selective treatment options to kill any highly proliferative cells (Joshi et al., 2021). • Comprehensive characterization of RHOA Y42C mutation at molecular, cellular, and tissue level in the suitable model systems would pinpoint the major downstream effector targets, possibly leading to the development of precision therapy for those harboring this mutation. • One of the major challenges in studying RHOA Y42C mutation is the lack of appropriate and relevant experimental systems. To tackle this problem, the latest CRISPR/Cas9-based technique with several modifications (to improve efficiency) will be utilized to create this specific mutation at the endogenous gene loci using human stomach 3D organoid culture. In this way, the nature of the mutation and its impact in normal and neoplastic cells will be clearly examined with multi-omics approaches. • Another big challenge in developing effective targeted therapy is highly infiltrated fibroblasts in diffuse-subtype gastric cancer, which makes it very difficult to target gastric cancer cells associated with fibroblasts. There has been no extensive study in possible crosstalk between gastric cancer cells and fibroblasts though essential to understand such interaction to develop more efficient therapeutic options for gastric cancer patients. To solve this problem, a 3D co-culture system, called assembloids (Kim et al., 2020), will be established in vitro with cancer-associated fibroblasts and gastric cancer cells from diffusesubtype gastric cancer patients. With single-cell RNA sequencing at different time points being co-cultured, possible paracrine/juxtacrine interactions will be discovered and subsequently validated.