Literature Review: Asiaticoside Potentiates MSLN-Targeted CAR-T Cell Antitumor Efficacy in Ovarian Cancer - Multiplex Immunofluorescence Validation of the Tumor Microenvironment

Literature Review: Asiaticoside Enhances the Antitumor Efficacy of MSLN-Targeted CAR-T Cells in Ovarian Cancer

1. Publication Overview

• Title: Asiaticoside enhances the antitumor efficacy of MSLN-targeted CAR-T cells in ovarian cancer

• Journal: Journal of Translational Medicine (2026, Vol. 24:631; latest IF = 9.7, JCR Q1 translational medicine journal)

• DOI: 10.1186/s12967-026-08053-w

2. Core Conclusions

Asiaticoside (AC), a natural small molecule, targets the TGF-beta/SMAD signalling axis. This relieves exhaustion of MSLN-targeted CAR-T cells, blocks Treg differentiation and reverses the immunosuppressive tumour microenvironment of ovarian cancer. Both in vitro co-culture assays and in vivo peritoneal metastasis and subcutaneous xenograft models confirm that AC combined with CAR-T produces stronger antitumour activity without evident organ toxicity, positioning AC as a clinically translatable immuno-adjuvant for CAR-T therapy in solid tumours.

3. Role of Absin Products in the Study

The study used the Absin four-colour multiplex immunofluorescence kit abs50012-20T for multiplex in situ co-staining of tumour tissue. Based on TSA signal amplification, a single paraffin section simultaneously labels CD3, Ki67, CD31 and DAPI, providing direct visualisation of the spatial association between T-cell infiltration, tumour proliferation and angiogenesis within the tumour mass. This in situ histological evidence supports the in vivo conclusion that AC improves CAR-T tumour infiltration and suppresses proliferation and vascularisation, and the data meet the quality-control standards of high-impact translational medicine journals.

4. Background

CAR-T therapy has produced breakthrough efficacy in haematological malignancy, but its activity in solid tumours such as ovarian cancer remains limited. Two core bottlenecks are recognised: (i) high local secretion of TGF-beta1 by the tumour microenvironment continuously stimulates CAR-T cells to overexpress the exhaustion markers PD-1, TIM-3 and LAG-3, abolishing cytotoxic function; (ii) TGF-beta1 induces differentiation of CAR-T cells towards the immunosuppressive Treg lineage, creating a negative-feedback immunosuppressive loop.

Existing strategies to overcome this, such as dominant-negative TGF-beta receptor engineering or SMAD7 overexpression, involve complex gene editing with in vivo safety concerns. Natural small molecules offer a favourable alternative with better safety and simpler administration. AC is a triterpenoid saponin extracted from Centella asiatica; although its modulation of NK-cell immunity has been reported, whether AC regulates the TGF-beta pathway to improve CAR-T efficacy in solid tumours had not been systematically examined.

To address this, the authors constructed MSLN-targeted CAR-T cells and applied ovarian cancer SKOV-3 and OVCAR-3 models to investigate the molecular mechanism and in vivo therapeutic potential of AC in improving CAR-T antitumour function.

5. Overall Study Design

1. Single-cell secretome profiling of the baseline phenotype: co-culture confirmed that MSLN CAR-T cells secrete large amounts of immunosuppressive TGF-beta1 upon contact with ovarian tumour cells, driving exhaustion;

2. In vitro functional validation of AC synergy: RTCA and LDH release assays demonstrated that AC specifically enhances CAR-T killing of MSLN-positive tumour cells without affecting antigen-negative cells; transcriptome and flow cytometry confirmed downregulation of exhaustion markers and upregulation of IFN-gamma, perforin and granzyme B;

3. Molecular mechanism analysis: AC inhibits the TGF-beta/SMAD pathway, blocks SMAD2/3 phosphorylation and suppresses Treg differentiation; comparison with the TGF-beta receptor inhibitor SB431542 confirmed that AC activity depends on TGF-beta pathway blockade;

4. In vivo efficacy in a peritoneal metastasis model: SKOV-3-luc peritoneal metastasis in NCG mice, with in vivo bioluminescence imaging to monitor tumour burden, showed that AC plus CAR-T significantly cleared peritoneal metastases, with no body weight loss or organ damage;

5. Subcutaneous xenograft model plus in situ verification: the subcutaneous model confirmed antitumour effect, and Absin abs50012 multiplex fluorescence staining of tumour tissue demonstrated that AC increased intratumoural CD3+ T-cell infiltration while reducing Ki67 proliferation and CD31 angiogenesis.

6. Detailed Module-by-Module Analysis

Module 1. Single-cell secretome profiling confirms high TGF-beta1 secretion and exhaustion after CAR-T co-culture

Logic: single-cell cytokine profiling compares ordinary T cells with MSLN CAR-T cells after contact with SKOV-3 tumour cells, to define TGF-beta1 as the key inhibitory factor underlying CAR-T functional impairment.

Key experiments: IsoLight single-cell multi-factor detection and t-SNE visualisation of single-cell cytokine secretion clusters.

Key results: after co-culture, CAR-T cells showed increased secretion of effector cytokines including GM-CSF and granzyme B, but immunosuppressive TGF-beta1 and IL-6 were significantly higher than in ordinary T cells. Sustained TGF-beta1 stimulation drove CAR-T exhaustion. In this work, Fig. 1 presents PSI values comparing CAR-T cells against control T cells after stimulation with MSLN-positive targets, the proportion of cytokine-secreting cells in CAR-T versus control populations, signal intensities of secreted cytokines, and the 2D t-SNE projection of the single-cell cytokine landscape.

Module 2. AC specifically enhances MSLN-CAR-T antitumour activity in vitro

Logic: MSLN-positive (SKOV-3, OVCAR-3) and MSLN-negative (ES-2) ovarian cancer cell lines were compared using RTCA real-time impedance and LDH release cytotoxicity assays to verify the antigen dependence of AC synergy, and a safe working concentration of 20 uM was selected.

Key experiments: CCK-8 viability, RTCA real-time killing, LDH cytotoxicity.

Key results: 20 uM AC did not compromise CAR-T viability; the CAR-T+AC group showed significantly enhanced killing efficiency only in the MSLN-positive setting, whereas no difference was observed across groups in the ES-2 antigen-negative setting, excluding direct AC cytotoxicity. Fig. 2 shows MSLN surface expression by flow cytometry, MSLN protein levels by western blot, and RTCA curves for CAR-T co-cultured with OVCAR-3, SKOV-3 and ES-2 at an E:T ratio of 2:1, with CAR-T cells pre-treated with TGF-beta1 (10 ng/mL) for 24 h where indicated and AC (20 uM) added to the relevant groups, together with quantification of specific lysis at different E:T ratios (mean +/- SEM, n = 3).

Module 3. AC reverses TGF-beta1-induced CAR-T exhaustion and restores effector molecule secretion

Logic: RNA-seq screening of exhaustion and effector genes, plus flow cytometry of the exhaustion markers PD-1, TIM-3 and LAG-3 and intracellular IFN-gamma, perforin and granzyme B.

Key experiments: RNA sequencing, flow cytometry for exhaustion markers and intracellular cytokines.

Key results: TGF-beta1 treatment significantly upregulated exhaustion genes and downregulated effector genes; the combination with AC fully reversed this transcriptional phenotype. Flow cytometry quantification confirmed that AC reduced the proportion of inhibitory receptors and increased the fraction of cells positive for killing factors. Fig. 3 presents the heatmap of differentially expressed genes associated with T-cell exhaustion and effector functions across the indicated groups (n = 3), representative flow cytometry distributions and pooled quantification of PD-1, TIM-3 and LAG-3 in CAR-T, CAR-T+TGF-beta1, CAR-T+AC and CAR-T+TGF-beta1+AC groups after 24 h co-culture with SKOV-3 (E:T = 2:1), with pooled bar graphs from three donors, and intracellular staining of IFN-gamma, perforin and granzyme B with statistical summary; data are mean +/- SEM (n = 3), one-way ANOVA, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

Module 4. AC inhibits the TGF-beta/SMAD pathway and blocks CAR-T conversion to Treg

Logic: flow cytometry of the CD4+FOXP3+ Treg fraction, western blot and phospho-flow detection of SMAD2/3 phosphorylation, transcriptome enrichment of TGF-beta pathway genes, and validation with the positive control SB431542.

Key experiments: FOXP3 Treg flow cytometry, phospho-SMAD2/3 western blot, phospho-flow, KEGG pathway enrichment, pathway inhibitor control.

Key results: TGF-beta1 induced extensive differentiation of CAR-T cells into FOXP3+ Treg, and AC significantly reduced the Treg fraction. AC significantly suppressed SMAD2/3 phosphorylation and downregulated core TGF-beta pathway genes, with pathway suppression comparable to that achieved by SB431542. Fig. 4 shows flow cytometric analysis of CD4 and FOXP3 expression in CAR-T cells cultured with SKOV-3 (E:T = 2:1) in the presence of TGF-beta1, AC or both, with representative plots and pooled quantification from three donors; assessment of TGF-beta1 levels in the indicated groups by flow cytometry; intracellular staining of phospho-SMAD2/3; a heatmap of differentially expressed genes related to the TGF-beta signalling pathway; and western blot analysis of phospho-SMAD2/3 and total SMAD2/3 protein in the four groups. One-way ANOVA, **p < 0.01, ***p < 0.001, ****p < 0.0001, mean +/- SEM.

Module 5. AC combined with CAR-T suppresses ovarian cancer peritoneal metastasis with favourable in vivo safety

Logic: SKOV-3-luc peritoneal metastasis model in NCG mice, group-wise dosing of CAR-T with or without AC, in vivo bioluminescence imaging for dynamic tumour burden monitoring, and recording of body weight, endpoint peritoneal nodules, ascites, liver metastasis and organ H&E staining for safety assessment.

Key experiments: in vivo bioluminescence imaging, mouse body weight monitoring, gross abdominal photography, organ H&E histopathology.

Key results: the tumour bioluminescent signal declined continuously in the CAR-T+AC group, with residual tumour absent in 4 of 5 mice; body weight did not differ significantly between groups; organ H&E showed no necrosis or inflammatory injury and no systemic toxicity, while control groups displayed extensive peritoneal dissemination and liver metastasis. Fig. 5 presents the schematic of the SKOV-3-luc intraperitoneal metastasis model design, bioluminescence imaging of tumour burden during treatment, quantification of bioluminescent signals (ROI) at the indicated time points and body weight monitoring (mean +/- SEM, n = 5 per group, ****p < 0.0001). Fig. 6 shows macroscopic observation of metastatic nodules in the abdominal cavity with corresponding H&E images (scale bars 100 um and 20 um), appearance of peritoneal lavage fluid, and liver metastasis in the NC and CAR-T+TGF-beta1 groups.

Module 6. Subcutaneous xenograft model and Absin mIHC-based microenvironment verification

Logic: SKOV-3 subcutaneous xenograft with tumour volume and weight measurement, and in situ analysis of the tumour microenvironment using the Absin abs50012-20T four-colour multiplex immunofluorescence kit to co-stain CD3 (T cells), Ki67 (proliferation), CD31 (vasculature) and DAPI (nuclei).

Product workflow: 4 um tumour paraffin sections were processed through antigen retrieval, HRP blocking, several rounds of TSA fluorescent signal amplification and antibody elution, so that three protein targets plus DAPI nuclear counterstain were detected on the same section. TSA signal amplification addresses the weak fluorescence of low-abundance CD3+ T cells, and multi-channel imaging allows direct comparison of T-cell infiltration, tumour proliferation and microvessel density across groups.

Key results: the CAR-T+AC group showed the lowest tumour volume and weight; multiplex fluorescence sections showed significantly increased CD3+ infiltration together with markedly reduced Ki67 tumour proliferation and CD31 angiogenesis in this group, and H&E staining of heart, liver, kidney, spleen and lung showed no pathological damage, confirming in vivo safety. Fig. 7 presents the treatment scheme, excised xenograft images, tumour volume recorded every three days, xenograft tumour weights, and representative mIHC images of xenograft tumours: yellow, CD3; green, Ki67; pink, CD31; blue, DAPI, with scale bars of 100 um and 20 um. Data are mean +/- SEM, n = 5 per group, *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001.

7. Summary of the Role of the Absin abs50012-20T Kit

1. Core tool for in situ visualisation of the tumour microenvironment: the in vivo mechanistic conclusion of this work rests on the abs50012 four-colour multiplex fluorescence kit, which simultaneously marks T cells, tumour proliferation and vascular endothelium on a single section, establishing the spatial link between AC dosing, CAR-T infiltration and tumour growth inhibition — a capability that single-plex IHC cannot provide.

2. TSA signal amplification adapted to low-abundance immune markers: the built-in TSA tyramide amplification system resolves the small numbers of infiltrating CD3+ CAR-T cells in tumour tissue, avoiding weak-signal and false-negative problems in conventional immunofluorescence and ensuring reliable quantitative statistics.

3. Standardised workflow matching high-impact journal requirements: the kit provides pre-loaded reagents with stable elution steps and good staining reproducibility, and the mIHC imaging data satisfy the histological data quality-control standards expected by translational medicine SCI journals.

4. Extension to clinical sample cohorts: the kit can process human ovarian cancer clinical paraffin samples in batch, detecting infiltrating T cells, proliferation and vascular markers simultaneously, which supports future work on patient stratification and efficacy prediction for AC combined with CAR-T.

Contact Absin

Absin provides antibodies, proteins, ELISA kits, cell culture, detection kits, and other research reagents. If you have any product needs, please contact us.

Absin Bioscience Inc. worldwide@absin.cn

Follow us on Facebook: Absin Bio