CHN1 suppresses B-cell non-Hodgkin lymphoma progression via akt/mTOR pathway

Abstract Introduction B-cell non-Hodgkin lymphoma (B-NHL) is the most prevalent NHL subtype, exhibiting high heterogeneity. Chimerin 1 (CHN1), a rac guanosine triphosphatase activating protein (racGAP), is predominantly expressed in neurons, especially in the cerebral cortex, and plays an important role in axon guidance. The previous study has estimated that CHN1 was associated with B-NHL aggressiveness, showing higher expression in indolent follicular lymphoma (FL) compared to aggressive Burkitt lymphoma (BL). In silico analysis also linked high CHN1 expression with favorable outcomes in diffuse large B-cell lymphoma (DLBCL) patients, though this prognostic value requires validation. The functional role of CHN1 in B-NHL remains unclear. Therefore, we aimed to validate the prognostic value of CHN1 in DLBCL and elucidate its biological functions and signaling pathways in B-NHL cells. Methods We retrospectively collected pathological specimens from 52 DLBCL patients. CHN1 expression was assessed by immunohistochemical (IHC) staining. Kaplan-Meier analysis evaluated the correlation between CHN1 expression levels and the prognosis of DLBCL patients. Stable CHN1-overexpressing human DLBCL cell line OCI-LY3 and human Burkitt lymphoma cell line Raji were established via lentiviral transduction. Cell proliferation was measured by direct cell counting. Migration and invasion were assessed using Transwell assays. Protein expression was analyzed by Western blotting. Transcriptome sequencing of OCI-LY3^OE^ cells, followed by GO, KEGG, and GSEA enrichment analyses, identified downstream pathways. Results IHC analysis classified DLBCL patients into CHN1-high and CHN1-low groups (cut-off value: 10% positivity). The CHN1-high group exhibited significantly higher objective response (OR: 86.2% vs. 39.1%, p=0.001) and complete response (CR: 65.5% vs. 21.7%, p=0.002) rates compared to the CHN1-low group. The disease progression (PD) rate was significantly lower in the CHN1-high group (10.3% vs. 52.2%, p=0.001). Kaplan-Meier analysis demonstrated that high CHN1 expression was significantly correlated with prolonged overall survival (OS, p=0.036) and progression-free survival (PFS, p=0.002). Successful establishment of CHN1-overexpressing RajiOE and OCI-LY3OE cells was confirmed. CHN1 overexpression significantly inhibited proliferation (p<0.001) and promoted apoptosis in both cell lines (Raji: p<0.001; OCI-LY3: p=0.002). Western blot demonstrated that CHN1 downregulated the anti-apoptotic protein BCL-2 (OCI-LY3OE: p=0.029; RajiOE: p=0.036) and upregulated the pro-apoptotic protein Bax (OCI-LY3OE: p=0.047; RajiOE: p=0.029). Furthermore, CHN1 suppressed migration (OCI-LY3: p=0.004; Raji: p=0.008) and invasion (OCI-LY3: p=0.012; Raji: p=0.007). Transcriptome sequencing of CHN1-overexpressing OCI-LY3 cells identified 867 upregulated and 1,035 downregulated genes. Enrichment analyses suggested that CHN1 involvement in cell adhesion, metabolism, vesicle formation, and cell junctions, and modulate pathways including PI3K/Akt, IL6/JAK/STAT3, and IL2/STAT5 signaling. Consistently, western blot revealed that CHN1 suppressed the phosphorylation of Akt and mTOR. Treatment with the Akt activator Sc79 partially restored Akt/mTOR phosphorylation and rescued the proliferative, migratory, and invasive capacities by CHN1 overexpression. Conclusions High CHN1 expression is a favorable prognostic marker in DLBCL, associated with higher OR/CR rates, lower PD, and prolonged OS and PFS. CHN1 suppresses B-NHL progression by inhibiting proliferation, migration, and invasion in B-NHL cells. Mechanistically, the Akt/mTOR signaling pathway may be a downstream mechanism of CHN1 in B-NHL cells.