HDAC6 Identified as Biomarker for B-ALL Dissemination and Relapse Risk

A new study published in The British Journal of Cancer identifies histone deacetylase 6 (HDAC6查看药品详情) as a clinically significant biomarker for dissemination and relapse in B-cell acute lymphoblastic leukemia (搜索)搜索该疾病 (B-ALL), the most common pediatric malignancy accounting for approximately 80% of ALL cases. The research, led by Jiménez-Camacho and colleagues, demonstrates that elevated HDAC6 levels correlate with aggressive disease trajectory and treatment failure across both pediatric and adult patient cohorts.

The findings address a persistent clinical challenge: although most B-ALL patients achieve complete remission, relapse occurs in roughly 20% of cases and remains the leading cause of treatment failure. Relapse is typically driven by therapy-resistant leukemic clones, with the majority arising in the bone marrow, either in isolation or with central nervous system, testicular, or other extramedullary involvement.

HDAC6查看药品详情 Overexpression Correlates with Relapse

Analysis of RNA-seq data from 22 pediatric B-ALL patients showed significantly higher HDAC6查看药品详情 expression compared with healthy controls. In an independent cohort of 72 pediatric B-ALL patients assessed by flow cytometry, HDAC6 protein levels were significantly increased in samples from relapsed patients compared with both normal CD19⁺ B cells and cells at debut. Critically, in 16 paired debut–relapse samples, HDAC6 protein levels were significantly higher at relapse, indicating a more prominent role for HDAC6 during disease recurrence.

The pattern held in adults. Among 54 adult B-ALL patients, those who subsequently relapsed exhibited significantly higher HDAC6查看药品详情 levels at debut than those who remained in remission. "These findings position HDAC6 as a promising biomarker of relapse risk," the authors note.

Mechanistic Basis: Cortactin (搜索)搜索该靶点, F-Actin, and Receptor Regulation

Using the B-ALL cell line REH, which exhibits significantly higher HDAC6查看药品详情 levels than healthy bone marrow-derived CD19⁺ B cells, the team demonstrated that HDAC6 localizes predominantly to the cytoplasm. Upon CXCL12 stimulation, both HDAC6 and cortactin (搜索)搜索该靶点 enriched at the leading edge of polarized cells with lamellipodia-like protrusions.

Pharmacologic inhibition with tubastatin A查看药品详情 (TubA), a selective HDAC6查看药品详情 inhibitor, at 20 μM significantly reduced CXCL12-induced transendothelial migration across HUVEC monolayers. The IC50 of TubA was determined to be 94 μM after 24 hours. Treated cells exhibited significantly reduced F-actin polymerization following CXCL12 stimulation.

Experiments in cortactin (搜索)搜索该靶点-knockdown REH cells revealed that HDAC6查看药品详情 inhibition did not further reduce transendothelial migration compared with DMSO-treated cortactin-KD cells or TubA-treated wild-type cells, indicating that HDAC6 promotes transendothelial migration predominantly via cortactin deacetylation.

Beyond cytoskeletal effects, HDAC6查看药品详情 inhibition reduced surface expression of CXCR4 (搜索)搜索该靶点 and the integrin subunits CD49d and CD29 (components of VLA-4 (搜索)搜索该靶点), with the latter effect being time-dependent and consistent with altered receptor trafficking rather than acute internalization.

Bone Marrow Niche Drives HDAC6查看药品详情 Upregulation

In 9 of 12 patients with paired bone marrow and peripheral blood samples, HDAC6查看药品详情 levels were higher in bone marrow-derived blasts. Co-culture experiments demonstrated that direct contact with bone marrow mesenchymal stromal cells (HS5 line) significantly increased HDAC6 levels in both primary B-ALL cells and REH cells, while non-adherent cells did not exhibit such changes. Individual stimuli including CXCL12, VCAM-1 adhesion, and Activin-A each modestly increased HDAC6 levels, but none recapitulated the robust upregulation observed in 2D and 3D MSC co-culture systems.

In Vivo Validation

In a xenograft model using NSG mice transplanted with REH cells, TubA treatment (50 mg/kg/day, intraperitoneally, every other day for 27 days) markedly impaired leukemic homing to the bone marrow and significantly reduced infiltration of the brain and liver. By day 27, all vehicle-treated mice exhibited overt disease signs including reduced activity and hind-limb paralysis, whereas none of the TubA-treated mice showed overt disease at this time point. A trend toward reduced leukemic burden was observed in the spleen and lungs, though no differences were detected in testicular infiltration, suggesting that leukemic colonization of this sanctuary site may occur independently of HDAC6查看药品详情 activity.

Genetic depletion of HDAC6查看药品详情 via shRNA (~70% knockdown) phenocopied the pharmacologic effects, significantly reducing CXCL12-induced transmigration and bone marrow MSC spheroid colonization, with TubA producing no additional effect in HDAC6-depleted cells.

Clinical Implications and Limitations

The study nominates HDAC6查看药品详情 as both a biomarker for relapse risk stratification and a therapeutic target to limit leukemic dissemination. The authors acknowledge several limitations: mechanistic analyses were primarily performed in REH cells; some patient-derived experiments were constrained by sample availability; and while HDAC6 inhibition reduced dissemination in vivo, it did not significantly extend survival, suggesting combination strategies may be needed. Xenograft studies with HDAC6-depleted cells could not be performed due to insufficient cell numbers.

"Genetic and pharmacologic inhibition across complementary functional assays identifies HDAC6查看药品详情 as a key regulator of B-ALL cell migration, BM homing, and organ infiltration," the authors conclude. "The highest HDAC6 levels occur in relapsed patients, underscoring its clinical relevance."