# HBx hijacks the miR‐19a‐3p/BAMBI/TGF‐β1 axis to impair the anti‐tumour activity of CD4+ T cells in diffuse large B‐cell lymphoma

## TL;DR

This study shows how the HBV protein HBx weakens CD4+ T cell function in lymphoma, leading to worse outcomes, and suggests targeting TGF-β or restoring miR-19a-3p as potential therapies.

## Contribution

The study identifies a novel HBx-mediated miR-19a-3p/BAMBI/TGF-β1 axis that drives CD4+ T cell dysfunction in HBV+ DLBCL.

## Key findings

- Reduced CD4+ T cell infiltration predicts poor survival in HBV+ DLBCL.
- HBx down-regulates miR-19a-3p, activating Wnt signaling and increasing TGF-β1 to suppress CD4+ T cell activity.
- Targeting TGF-β or restoring miR-19a-3p improves CD4+ T cell immunity and limits tumor progression.

## Abstract

Hepatitis B virus (HBV) is clinically associated with poor prognosis in diffuse large B‐cell lymphoma (DLBCL), while cellular communication in the tumour microenvironment (TME) is recognized as a critical driver of tumour progression. Nevertheless, whether HBV infection mediates DLBCL cell‐immune cell crosstalk remains undefined, with the precise mechanisms and associated key molecules remaining elusive.

SsGSEA, Cox regression (univariate/multivariate), WGCNA, and Kaplan–Meier analyses identified prognostic immune subsets and miRNAs in HBV+ DLBCL. Dual luciferase assay, qRT‐PCR, western blot, ChIP, Co‐IP, flow cytometry, enzyme‐linked immunosorbent assay, immunohistochemistry, and murine models were employed together to evaluate CD4+ T cell dysfunction in vitro and in vivo. ScRNA‐seq analyses encompassed clustering, pseudotemporal trajectory, and ligand–receptor networks to decode TME dynamics.

TME profiling identified diminished CD4⁺ T cell infiltration as an independent predictor of poor survival in HBV⁺ DLBCL. Mechanistically, HBx‐mediated down‐regulation of miR‐19a‐3p activated the BAMBI/Wnt signalling pathway, thereby enhancing TGF‐β1 secretion and suppressing the anti‐tumour activity of CD4+ T cells. Single‐cell analysis revealed that BAMBIhigh DLBCL cells engage CD4+ T cells via TGFB1‐TGFBR2 pair, with TGFBR2 enriched in exhausted subsets of CD4+ T cells and shaping their dysfunctional fate. Therapeutic restoration of miR‐19a‐3p or blockade of TGF‐β reinforced the CD4⁺ T cell anti‐tumour activity and restrained the progression of HBx‐overexpressing DLBCL in vivo.

HBx promoted TGF‐β1 hypersecretion via miR‐19a‐3p repression‐mediated Wnt/β‐catenin activation, directly driving CD4+ T cell depletion and functional exhaustion in DLBCL. Our work provided important insights into the immune determinants of poor prognosis in HBV+ DLBCL, highlighting the pivotal role of CD4+ T cell dysfunction in driving disease progression and adverse clinical outcomes.

Reduced CD4+ T cell enrichment in the TME predicted poor survival in HBV+ DLBCL.Down‐regulation of miR‐19a‐3p by HBx activated the BAMBI‐mediated Wnt signalling, amplifying TGF‐β1 secretion to suppress anti‐tumour activity of CD4⁺ T cells.The TGF‐B1/TGFBR2 pair mediated the HBV+ DLBCL‐CD4+ T cell communication.Targeting TGF‐β or miR‐19a‐3p improved CD4+ T cell immunity to suppress HBV+ DLBCL progression

Reduced CD4+ T cell enrichment in the TME predicted poor survival in HBV+ DLBCL.

Down‐regulation of miR‐19a‐3p by HBx activated the BAMBI‐mediated Wnt signalling, amplifying TGF‐β1 secretion to suppress anti‐tumour activity of CD4⁺ T cells.

The TGF‐B1/TGFBR2 pair mediated the HBV+ DLBCL‐CD4+ T cell communication.

Targeting TGF‐β or miR‐19a‐3p improved CD4+ T cell immunity to suppress HBV+ DLBCL progression

HBx down‐regulated miR‐19a‐3p, leading to activation of BAMBI‐mediated Wnt signalling and increased TGF‐β1 secretion by malignant B cells. The TGF‐B1/TGFBR2 signalling axis mediated tumour‐CD4+ T cell communication, suppressing CD4+ T cell anti‐tumour activity and resulting in reduced CD4+ T cell enrichment and poor prognosis. Therapeutic targeting of TGF‐β or restoration of miR‐19a‐3p enhanced CD4+ T cell immunity and limited HBV+ DLBCL progression.