Immunotherapy for SMARCB1-Deficient Sarcomas: Current Evidence and Future Developments

Mutations in subunits of the SWItch Sucrose Non-Fermentable (SWI/SNF) complex occur in 20% of all human tumors. Among these, the core subunit SMARCB1 is the most frequently mutated, and SMARCB1 loss represents a founder driver event in several malignancies, such as malignant rhabdoid tumors (MRT), epithelioid sarcoma, poorly differentiated chordoma, and renal medullary carcinoma (RMC). Intriguingly, SMARCB1-deficient pediatric MRT and RMC have recently been reported to be immunogenic, despite their very simple genome and low tumor mutational burden. Responses to immune checkpoint inhibitors have further been reported in some SMARCB1-deficient diseases. Here, we will review the preclinical data and clinical data that suggest that immunotherapy, including immune checkpoint inhibitors, may represent a promising therapeutic strategy for SMARCB1-defective tumors. We notably discuss the heterogeneity that exists among the spectrum of malignancies driven by SMARCB1-loss, and highlight challenges that are at stake for developing a personalized immunotherapy for these tumors, notably using molecular profiling of the tumor and of its microenvironment.

Automated summary

Mutations in subunits of the SWI/SNF complex, especially the core subunit SMARCB1, occur frequently in human tumors, and SMARCB1 loss is a key driver event in several malignancies. Even though SMARCB1-deficient tumors have a simple genome and low mutation burden, they have been found to be immunogenic, with some responses to immune checkpoint inhibitors reported. This review discusses the potential of immunotherapy, including immune checkpoint inhibitors, as a promising therapeutic strategy for SMARCB1-defective tumors. The heterogeneity among these tumors and the challenges in developing personalized immunotherapy based on molecular profiling are also highlighted.