Abstract 3843: Role of CD4/CD8 double positive T cells in modulating response to anti-PD-1 treatment in renal cell carcinoma

Abstract

Abstract Presence of CD4+CD8+ Double Positive T (DPT) cells in the tumor microenvironment has been correlated with good prognosis1. Renal cell carcinoma (RCC) is reported to have relatively much higher DPT cell sub-populations as compared to other cancer types1,2. DPT cells in RCC were reported to express high programmed cell death protein-1(PD-1) and therefore is considered a potential target for checkpoint based immunotherapy2. However, the clinical relevance of these DPT cells in determining response to anti-PD-1 has not yet been studied. Using the near native FarcastTM TruTumor RCC histoculture platform, we attempted to elucidate the role of DPT in anti-PD1 response modulation. Fresh surgically resected RCC samples (n=18) along with matched blood were collected from consented patients. Explants were generated and distributed into arms. These arms were treated in culture with nivolumab (anti-PD1:132µg/ml) for 72 hours. The response was evaluated using histopathology and flow cytometry read-outs. DPT cells were gated and expressed as percentage of CD3 using flowcytometry. We observed a significantly higher proportion of DPT cells in RCC (Mean±SEM: 8.2±2.8) compared to head and neck squamous cell carcinoma (Mean±SEM: 1.2±0.4) and ovarian cancer (Mean±SEM: 0.7±0.1). DPT cell population was found to be well preserved on the TruTumor RCC platform post-culture. We stratified samples as high and low DPT cell sub cohorts based on 5% cut-off. Out of 18, 6 samples (33%) showed high DPT cells (with a range of 7-41%). Eighty-three percent (5 out of 6) of high DPT samples elicited a tumor cytotoxicity on treatment with Nivolumab treatment as compared to only 50% (6 out of 12) in low DPT samples. A significant decrease (p<0.05) in DPT cells was observed in the high DPT sub cohort upon Nivolumab treatment, with a concomitant increase in activated (Granzyme B+) DPT and cytotoxic T cells (CD8+) sub-populations was observed upon nivolumab treatment. However, total CD8+ proportions remained unchanged. In addition, an increase in effector (CD4+ FoxP3-) and decrease in Treg (CD4+FoxP3+) population was also observed. Only one out of six high DPT samples exhibited no cytotoxicity in response to nivolumab treatment. Interestingly in this non-responder sample there was a 3.1-fold increase in M2-like (CD68+CD206+) macrophages, as compared to a M1-like macrophage polarization observed in the remaining high DPT samples. In summary, our data suggests that presence of high percentage of DPT cells could favour better response to anti-PD1 therapy in RCC patients. The FarcastTM TruTumor platform thus provides powerful insights into the role of various immune cell sub-populations in modulating response to treatment with immune-oncology therapies.