Intratumoral T cell clonality and survival in a randomized phase II study of preoperative autophagy inhibition in combination with gemcitabine and nab-paclitaxel treatment in patients with resectable pancreatic cancer.

Abstract

e16001 Background: Autophagy is a cell survival mechanism that is upregulated in pancreatic ductal adenocarcinoma (PDAC). PDAC autophagy results in an altered metabolic phenotype that promotes tumor progression, chemotherapeutic resistance, and immune evasion. Methods: We previously completed a randomized phase II clinical trial of preoperative gemcitabine-nab-paclitaxel with (PGH n = 34) and without (PG, n = 30) autophagy inhibition in patients with resectable and borderline resectable PDAC, which demonstrated increased Evans Grade histopathologic and serum CA 19-9 response with autophagy inhibition (IRB 13-074, NCT01128296 ). Utilizing the resected FFPE tumor specimens from evaluable patients, we completed paired multiplex immunohistochemistry (CD4, CD8, FOXP3, CD20, CD68, Pan-CK) and T & B cell receptor RNA sequencing to assess the intratumoral adaptive immune response and correlates of outcome. Results: Autophagy inhibition increased the number of infiltrating CD8 T cells (1133±490 vs 712±460 average cells per high power field, p = 0.01), CD8:CD20 ratio (2.22±3.1 vs 0.96±1.1, p = 0.02) and reduced the CD4:CD8 ratio (2.04±0.87 vs 3.01±2.09, p = 0.03). No effect was observed on the number of immature or mature germinal center-like tertiary lymphoid structures (TLS), though the number of TLS correlated with increased infiltration of CD4 T cells (r = 0.40, p < 0.001), T-regulatory cells (r = 0.26, p = 0.03) and CD20 B cells (r = 0.65, p < 0.001). Although the total number of productive T and B cell receptors increased with autophagy inhibition (167217±105961 vs 97339±5,1628, p = 0.02), no apparent effects were observed on Vαβ TCR or BCR IgH, Igκ, Igλ clonality. Independent of treatment, intratumoral CD8 counts were associated with an improved CA 19-9 response (r = 0.32, p = 0.04) and in a subset of short term ( < 2 years, n = 17) and long term ( > 4 years, n = 10) survivors (LTS), a lowered CD4:CD8 ratio was identified in LTS (1.83±0.63 vs 2.8±0.90, p = 0.01). Dominance of B cell receptors was a prominent feature of the immune repertoire in all patients (average expression: Vα 0.6%, Vβ 0.8%, IgH 18.9%, Igκ 32.3%, Igλ 47.2%) with an IgA skewed immunoglobulin class switching (mean 63% of all BCRs). Increased αβ T cell receptor clonality above the median level was associated with a CA 19-9 response (r = 0.37, p = 0.06) and greater overall survival (median OS 38.3 vs 19.3 months, p = 0.02), indicative of possible tumor specific clonal expansion. Conclusions: Preoperative autophagy inhibition increased the number of tumor infiltrating CD8 T cells in patients with localized pancreatic cancer. Intratumoral αβ T cell receptor clonality was associated with CA 19-9 response and improved overall survival. Combination treatment regimens increasing PDAC specific CD8 responses are warranted. Clinical trial information: NCT01978184.