Heparanase promotes tumor infiltration and antitumor activity of CAR-redirected T lymphocytes

Gianpietro Dotti and colleagues report that CAR-T cells expressing heparanase to degrade the extracellular matrix may enhance their infiltration of and effects on solid tumors. Adoptive transfer of chimeric antigen receptor (CAR)-redirected T lymphocytes (CAR-T cells) has had less striking therapeutic effects in solid tumors 1 , 2 , 3 than in lymphoid malignancies 4 , 5 . Although active tumor-mediated immunosuppression may have a role in limiting the efficacy of CAR-T cells 6 , functional changes in T lymphocytes after their ex vivo manipulation may also account for the reduced ability of cultured CAR-T cells to penetrate stroma-rich solid tumors compared with lymphoid tissues. We therefore studied the capacity of human in vitro –cultured CAR-T cells to degrade components of the extracellular matrix (ECM). In contrast to freshly isolated T lymphocytes, we found that in vitro –cultured T lymphocytes lack expression of the enzyme heparanase (HPSE), which degrades heparan sulfate proteoglycans, the main components of ECM. We found that HPSE mRNA is downregulated in in vitro –expanded T cells, which may be a consequence of p53 (officially known as TP53 , encoding tumor protein 53) binding to the HPSE gene promoter. We therefore engineered CAR-T cells to express HPSE and showed their improved capacity to degrade the ECM, which promoted tumor T cell infiltration and antitumor activity. The use of this strategy may enhance the activity of CAR-T cells in individuals with stroma-rich solid tumors.