Evaluating and manipulating the immune landscape in hepatic verses peritoneal metastases arising from colorectal primary tumors.

Abstract

568 Background: Colorectal metastases arise predominantly in the liver, lung and peritoneum. It is becoming increasingly clear that these locations might be distinct in terms of tumor cell tropism and genetics. We explored the immunological landscape in primary colorectal tumors along with hepatic and peritoneal metastases. The ultimate intent is to identify opportunities to implore immunomodulatory strategies to improve patient outcomes. Methods: Cancer biopsies were processed to generate tumor-derived organoids and TILs from patients with primary and/or metastatic tumors. These were co-cultured with patient matched TILs to assess immune competency and opportunities to employ checkpoint blockade using an in vitro platform we recently developed to explore TIL activity in patients with rectal cancer prior to standard of care therapy. Results: We found substantively different levels of TILs, their sub-set composition and most importantly their capacity to kill tumor cells. The nature of the metastatic peritoneal and hepatic tumor TILs were distinct. Where high programmed cell death 1 (PD-1) expression was high on TILs there was an opportunity to test PD-1 receptor function with blocking antibodies whereby some TILs showed enhanced cytotoxicity while others did not. Conclusions: Using our immune function assay we have demonstrated the distinct activities of patient-matched TILs in terms of killing at different organ sites of metastases. We also found differences in response to checkpoint inhibition blockade and de novo immune resistance.