Abstract
During our efforts to develop tumor-infiltrating lymphocyte (TIL) therapy to counter the devastating recurrence rate in patients with primary resectable pancreatic ductal adenocarcinoma (PDA), we found that PDA TILs can readily be expanded in vitro and that the majority of resulting TIL cultures show reactivity against the autologous tumor. However, the fraction of tumor-reactive T cells is low. We investigated to which extent this was related to the in vitro expansion. We compared the clonal composition of TIL preparations before and after in vitro expansion using T-cell receptor (TCR) deep sequencing. Our findings for PDA were benchmarked to experiments with melanoma TILs. We found that the TIL TCR repertoire changes dramatically during in vitro expansion, leading to loss of tumor- dominant T-cell clones and overgrowth by newly emerging T-cell clones that are barely detectable in the tumor. These changes are primarily driven by differences in the intrinsic in vitro expansion capacity of T-cell clones. Single-cell experiments showed an association between poor proliferative capacity and expression of markers related to antigen experience and dysfunction. Furthermore, we found that spatial heterogeneity of the TIL repertoire resulted in TCR repertoires that are greatly divergent between TIL cultures derived from distant tumor samples of the same patient. Culture-induced changes in clonal composition are likely to affect tumor reactivity of TIL preparations. TCR deep sequencing provides important insights into the factors that govern the outcome of in vitro TIL expansion and thereby a path toward optimization of the production of TIL preparations with high therapeutic efficacy.See related commentary by Lozano-Rabella and Gros, p. 4177.
Highlights
The positive prognostic role of tumor-infiltrating lymphocytes (TIL) in many human cancers indicates that the immune system is able to recognize and respond to tumors
We found that the TIL T-cell receptor (TCR) repertoire changes dramatically during in vitro expansion, leading to loss of tumordominant T-cell clones and overgrowth by newly emerging T-cell clones that are barely detectable in the tumor
We found that spatial heterogeneity of the TIL repertoire resulted in TCR repertoires that are greatly divergent between TIL cultures derived from distant tumor samples of the same patient
Summary
The positive prognostic role of tumor-infiltrating lymphocytes (TIL) in many human cancers indicates that the immune system is able to recognize and respond to tumors. Recent developments demonstrate that the antitumor T-cell response can be effectively harnessed, in that blocking of negative regulatory signals with checkpoint inhibitory antibodies in vivo, as well as in vitro expansion and reinfusion of TIL, can result in striking clinical impact in patients with metastatic cancer [1, 2]. Objective response rates range from 35% to 72%, including up to 20% complete responses, which are often longlasting [5,6,7,8,9,10,11] These data support the notion that TILs contain— and likely are enriched for—tumor-reactive T cells. These clinical results are highly encouraging, our understanding of parameters characterizing effective TIL infusion products remains limited. Several studies have investigated different means of TIL expansion, for example employing specialized culture vessels to improve gas and AACRJournals.org | 4289
Submitted Version (Free)
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have