Adoptive Cell Therapy with solid tumours: focus on renal cell carcinoma

Background: Adoptive cell therapy (ACT) involves the transfer of T cells to treat the disease after ex vivo manipulation. T cells can be derived either from peripheral blood mononuclear cells (PBMCs) or tumour infiltrating lymphocytes (TILs). Encouraging results have been achieved after TILs transfer in patients with metastatic melanoma; more recently chronic lymphoblastic leukemia patients were treated with PBMCs transduced with an anti-CD19 chimeric antigen receptor achieving complete and durable responses after a year of follow-up. Unfortunately, attempts to use ACT with other solid tumours failed to obtain comparable clinical responses. This project focuses upon the optimization of the ACT protocol in order to treat renal cell carcinomas (RCC), particularly investigating TILs. The method used to isolate TILs from melanoma samples does not appear to be as effective with RCC TILs and a longer period of time ex vivo is required to grow enough cells to be infused into the patients.Methods: Tumour samples were enzymatically disaggregated overnight or for 2 hours with gentleMACS™ dissociator. Activating beads coated with anti-CD3 and anti-CD28 antibodies were investigated as an alternative method to grow TILs out of renal tumour samples. TILs were isolated, activated with beads for 5 days and expanded for other 10 days using 3000U/ml IL-2. Their in vitro functional activity was assessed by measuring IFN-γ secretion with ELISA assays at the end of the expansion period. Results: Activating beads appear to drive the expansion of isolated TILs. 12 out of 13 cultures overcame the established threshold of 10x106 cells after 15 days of culture. The average fold expansion of TILs in twelve samples was 21.4 ± 6.2 with values ranging from 2.5 to 55.38. T cells were cultured overnight with autologous tumour or HLA-A2-matched cell lines, when possible, and IFN-γ was used as a read-out of their in-vitro activity. 25% of the tumours showed statistically significant secretion of IFN-γ when co-cultured with autologous tumour compared to TILs alone. In particular, 2 out of 3 of the samples disaggregated with gentleMACS™ dissociator showed IFN-γ secretion possibly due to the presence of surface markers/antigens that are lost with the traditional overnight disaggregation.Conclusions: TILs can be successfully grown from RCC tumour achieving satisfactory expansion rates in a shorter period of time compared to previous studies. Future experiments aim to further investigate TILs functionality in vitro and to develop a suitable mouse model to verify their in vivo capability of killing tumour cells.