Acute Myeloid Leukemia (AML) is a hematologic malignancy with poor prognosis that can occur from myelodysplastic syndrome (MDS) progression. RHOC is a Rho GTPase protein involved in cancer progression, but its expression and function have not been explored in these diseases.

To investigate the expression and signaling pathways related to RHOC in AML and MDS.

RHOC gene expression was analyzed by quantitative PCR in bone marrow samples from patients with MDS (n = 47) or AML (n = 58), and heathy donors (n = 14), attended at University of Campinas. The study was approved by the local Ethical Committee on Human Research. Clinical and genomic data of AML patients from The Cancer Genome Atlas (TCGA, n = 173) were also analyzed. Risk factors impacting overall survival (OS) and disease-free survival (DFS) were estimated using a Cox regression model. SRC expression was evaluated by western blot in U937 leukemia cell line stably silenced for RHOC using lentiviral vector-mediated shRNA.

RHOC expression was increased in AML patients with previous MDS (n = 15) and de novo AML (n = 43), compared to normal hematopoietic cells (all p < 0.05). No significant differences in RHOC expression were observed in MDS patients. Bone marrow samples from four MDS patients of our cohort were analyzed before and after progression to AML. Interestingly, these patients presented increased RHOC expression after the progression. Analysis from TCGA study revealed that RHOC was upregulated in patients with adverse cytogenetic risk compared to AML with intermediate cytogenetic risk. Univariate analysis showed that higher levels of RHOC (above median) impacted OS and DFS (all p < 0.05). Multivariate analysis confirmed that higher RHOC was an independent prognostic factor for inferior OS (HR = 1.378, CI= 1.194-1.699, p < 0.001) and DFS (HR = 1.421, CI=1.086-1.860, p < 0.010). Higher RHOC expression was associated with the presence of TP53 mutations, and lower RHOC was associated with the presence of CEBPA or NPM1 or WT1 mutations (Fisher's exact test). Gene set enrichment analysis revealed that RHOC is associated with signaling pathways such as regulation of actin cytoskeleton, apoptosis, and DNA damage responses. In addition, RHOC expression positively correlated with the expression of SRC oncogene (R = 0,61, Spearman; p = 4,63e-19). Notably, leukemia cells silenced for RHOC presented decreased SRC protein expression.

RHOC expression is increased in AML and negatively impacts patient survival. These results may be possibly explained by the RHOC relation with SRC and participation in signaling pathways such as migration, apoptosis, and DNA damage responses. Funding: FAPESP, and CAPES.