Targeting SALL4 with an HLA Class I–restricted TCR for cancer immunotherapy

Aberrant expression of the oncogene SALL4 is associated with stemness, more aggressive cancer phenotype, and reduced patient survival in various tumor types making SALL4 a potential target for cancer immunotherapy. We conducted a transcriptional analysis of SALL4 expression in colorectal cancer (CRC) tissues and demonstrated that SALL4 was overexpressed in primary tumor and paired liver metastasis. Then, we identified the SALL4-derived S9V peptide as a naturally processed peptide that induced specific CD8+ T-cell responses from the peripheral blood of gastrointestinal cancer patients whereas no responses were observed for the peripheral blood of healthy donors. Thereafter, we isolated a SALL4-specific T-cell receptor (TCR) that recognized this peptide in the most common HLA molecule in the Caucasian population, HLA-A2, and used this to develop TCR-engineered T cells. In vitro analysis showed that SALL4 TCR-redirected primary CD8+ T cells exhibited cytotoxic effects against SALL4-expressing tumor cells and produced effector cytokines. In vivo, SALL4-TCR T cells significantly reduced tumor growth and improved survival of tumor-bearing mice. Moreover, SALL4-TCR T cells displayed no toxicity against hematopoietic stem cells. Thus, we conclude that T cells engineered to express a SALL4-specific TCR have the potential to be effective as immunotherapy for solid cancers and pave the way for further clinical development.