A new “off-the shelf” combinatorial CAR therapy targeting two antigens to prevent tumor escape in prostate cancer

Prostate cancer is one of the most common cancers worldwide. The early stages of the disease can be managed through surgery or radiation, but treatments for more advanced stages are mostly limited to chemotherapy, which aims to slow tumor progression but often with limited success. Nowadays, immunotherapy appears to be one of the most promising solutions for treating advanced stages of prostate cancer. Immunotherapy aims to induce a specific anti-tumor immune response to eradicate the disease in the patient. One of the most powerful resources in immunotherapy is Adoptive Cell Therapy (ACT), which uses immune cells engineered to express a chimeric antigen receptor (CAR) targeting specific tumor antigens. ACT with CAR-engineered NK cells overcomes the main limitations related to the laborious and expensive production of CAR-transduced T-effector cells and to their frequent toxic effect. CAR-NK cells can be produced from different sources, but the most convenient approach in terms of time and cost is based on the NK-92 cell line that have been most thoroughly investigated and have already reached the testing phase in the clinical setting and also hold the potential for the development as standardized off-the-shelf therapeutics for adoptive cancer immunotherapy (ACT). Unfortunately, the tumor often manages to evade the immune system (and so CAR therapy) by downregulating the expression of the specific antigen through a mechanism known as tumor antigen escape. The aim of this study is to produce a safe, cost-effective, off-the-shelf ACT for prostate cancer treatment capable of bypassing tumor antigen escape through the use of a combinatorial or a Dual-CAR strategy that targets two different antigens overexpressed on prostate tumors. To achieve this, various NK-92 cell lines were generated to create a powerful prostate cancer-specific therapeutic tool. Specifically, NK-92 cells were engineered with an anti-hPSMA CAR or an anti-hPSCA CAR for a combinatorial therapy, otherwise with a Dual-CAR targeting both antigens. In this work we demonstrated that CAR-engineered NK-92 cells display a high and specific recognition of hPSMA+/hPSCA+ PCa and that a combinatorial or a Dual-CAR therapy could represent an efficient strategy to prevent antigen escape in prostate carcinoma, thus paving the way to off-the-shelf cellular therapeutics for targeted elimination of cancer cells.