Targeted Biological and Cellular Immunotherapies for Osteosarcoma

Abstract

Osteosarcoma (OSA) is the most common cancer of the bone and third most common cancer diagnosed in children and adolescent. The five-year survival rate for OSA patients approaches 70%; however, this rate drops to less than 30% with metastatic disease. There have been no changes in treatment options or patient outcome in over four decades. Consequently, there is a pressing need to identify actionable targets and develop novel immunotherapies for the treatment of OSA. Immunotherapies have proven to be successful for the treatment of hematological malignancies as well as some solid tumors, including cancers of the lung, kidney, and bladder. To date, OSA remains impervious to treatment with immunotherapies. We hypothesize that treating OSA using targeted immunotherapies will decrease proliferation in vitro and decrease tumor growth and invasion/migration while improving survival in vivo. To this end, we evaluated the efficacy of two different, targeted immunotherapies for the treatment of OSA. First, we tested a monoclonal antibody (mAb) targeting SEMA4D, a candidate gene previously identified in a forward genetic screen of OSA. Anti-SEMA4D treatment decreased OSA cell proliferation and MET production in vitro. In vivo, we saw anti-SEMA4D treatment slow tumor growth, decrease collagen deposition, decrease the incidence of metastasis, and modulate the immune cell infiltrate. OSA is traditionally an immunologically ‘cold’ tumor with poor immune cell infiltration and activity. As such, we also utilized a cell-based approach to target OSA using natural killer (NK) cells. NK cells are lymphocytes of the innate immune system involved in killing infected or malignantly transformed cells. Previous work has shown that unmanipulated NK cells are minimally effective in the treatment of cancer, likely due to poor persistence and suppression within the tumor microenvironment. To circumvent these challenges, we delivered a CD70-specific chimeric antigen receptor (CAR), soluble interleukin 15 (IL-15), and a transforming growth factor beta (TGF-β) dominant negative mutant receptor. These armored CD70-CAR NK cells show remarkable in vitro killing and pro-inflammatory cytokine activity against OSA. In vivo, we see armored CD70-NK cells home to the tumor as well as sustained persistence and strong anti-tumor activity. The goal of this work was to develop novel and effective therapies to treat OSA for use in the clinical setting. Future work will focus on developing multi-targeted approaches for these hard to treat and genetically diverse tumors.