The mammalian endoglycosidase heparanase (Hpa1) is primarily responsible for cleaving heparan sulphate proteoglycans (HSPGs) present on the basement membrane of cells and its potential for remodelling the extracellular matrix (ECM) could be important in embryonic development and tumour metastasis. Elevated expression of this enzyme has been implicated in various pathological processes including tumour cell proliferation, metastasis, inflammation and angiogenesis. The enzyme therefore represents a potential therapeutic target. Hpa1 protein is initially synthesized as an inactive 65 kDa proenzyme that is then believed to be subsequently activated by proteolytic cleavage to generate an active heterodimer of 8 and 50 kDa polypeptides. By analysis of a series of Hpa1 deletion proteins we confirm that the 8 kDa subunit is essential for enzyme activity. We present here for the first time an insect cell expression system used for the generation of large amounts of recombinant protein of high specific activity. Individual subunits were cloned into baculoviral secretory vectors and co-expressed in insect cells. Active secreted heterodimer protein was recovered from the medium and isolated by a one-step heparin-Sepharose chromatography procedure to give protein of >90% purity. The recombinant enzyme behaved similarly to the native protein with respect to the size of HS fragments liberated on digestion, substrate cleavage specificity and its preference for acidic pH. A significant amount of activity, however, was also detectable at physiological pH values, as measured both by an in vitro assay and by in vivo degradation of cell-bound heparan sulphate.

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Summary Hepatocellular carcinoma (HCC) is the most common type of liver cancer with limited treatments. Asia has the highest HCC incidence rates; China accounts for over 50% of all HCC cases worldwide. T‐cell receptor (TCR) ‐engineered T‐cell immunotherapies specific for human leukocyte antigen (HLA) ‐A*02:01‐restricted α‐fetoprotein (AFP) peptide have shown encouraging results in clinics. HLA‐A*24:02 is more common than HLA‐A*02:01 in Asian countries, including China. Here we identified a novel HLA‐A*24:02‐restricted peptide KWVESIFLIF (AFP2–11) located in AFP signal peptide domain by mass spectrometric analysis of HLA‐bound peptides from HepG2 cells. A TCR (KWV3.1) specific for AFP2–11‐HLA‐A*24:02 was isolated from peripheral blood mononuclear cells of a healthy donor. The binding affinity of soluble KWV3.1 to its antigen was determined to be ~55 μm, within the affinity range of native TCRs for self‐antigens. KWV3.1‐transfected T cells could specifically activate and kill AFP2–11 pulsed T2‐A24 cells and AFP+ HLA‐A*24:02+ tumor cell lines, demonstrating that AFP2–11 can be naturally presented on the surface of AFP+ tumor cell lines. The newly identified antigenic peptide can provide a novel target for immunotherapeutic strategies for patients with AFP+ HLA‐A*24:02+ HCC.

A fundamental understanding of cancer-specific antigens is crucial for successful T-cell immunotherapy. Sarcoma antigen 1 (SAGE1) is a cancer/testis antigen that has not yet been verified for T-cell immunotherapy applications. Here, we examined SAGE1 RNA expression and carried out IHC analyses, revealing that SAGE1 is expressed in 50% of non–small cell lung-cancer samples (n = 40). To verify the immunogenicity of SAGE1, we discovered a novel HLA-A*24:02 (HLA-A24)–restricted SAGE1 epitope (SAGE1597–606, VFSTAPPAFI) using mass spectrometry and identified SAGE1597–606-specific T-cell clones and T-cell receptors (TCR) from peripheral bloods of HLA-A24+ donors. The highest affinity TCR VF3 (KD = 4.3 μM) demonstrated the highest antitumor potency. Moreover, VF3-transduced T cells mediated the efficient killing of HLA-A24+/SAGE1+ tumor cells in vitro and effectively inhibited the growth of lung cancer xenografts in mice. Together, our data suggest that SAGE1 could be a target for T-cell immunotherapies against lung cancer, while its specific TCRs could be candidates for developing reagents to treat SAGE1+ tumors.

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