LAUSR

Adoptive transfer of tumor infiltrating lymphocytes (TIL) is a feasible and effective therapy for melanoma and lung cancer[1,2]. Multiple factors may determine the quality of the TIL product including components of the tumor microenvironment. In this work, we analyzed the role of melanoma infiltrating B cells in the context of TIL expansion based on their documented association with response to other types of immunotherapies[3]. We stimulated melanoma infiltrating B cells using human recombinant CD40L on the first day of ex-vivo TIL expansion. Samples were expanded from cryopreserved melanoma tumor single cell suspensions, in high dose IL-2 alone (standard protocol), or in high dose IL-2 plus CD40L. After 48h, analysis of activation markers on the CD40-expressing cells by flow cytometry was performed. For further investigation of the changes induced by CD40L stimulation, TIL expansion cultures (+/- CD40L) were analyzed using scRNA-seq (10X Genomics Chromium NextGEM Single Cell 5’ v2 and V(D)J Reagent kits; Illumina NovaSeq 6000 instrument with S4 sequencing flow cell) at 48h of culture (n=7 patients). The TIL expansion success rate was 68% with the CD40L treatment condition compared to 36% with the standard protocol. TILs cultured in the presence of CD40L expanded to on average three times more than with the standard protocol (P ≤ 0.01). Treatment with CD40L increased the percentage of CD39- CD69- T cells (P ≤ 0.05). Within the tumor digests, a higher percentage of B cells, including switched memory B cells (CD27+ IgD− ), was associated with successful TIL expansion (P=0.04). scRNA-seq analysis demonstrated different clustering patterns within the B cell compartment based on culture conditions. No clear partition was observed for other cell types, including the myeloid compartment. B cells displayed 126 DEGs associated to CD40L addition, CCL22, CD83, EBI3 and CD58 were among the upregulated genes in the CD40L-treated B cells. Other cell types experienced minimal to no change in transcriptomic profiles. B cell clusters were sub-classified based on CD27 and IgD expression[4], showing a predominance of naïve and switched memory B cells. Our results show that higher presence of B cells within tumors is associated with better TIL expansion, suggesting an interplay between T and B cells, and providing rationale for the design of improved TIL expansion protocols based on B cell stimulation with CD40L. This work has been supported in part by the Flow Cytometry, Genomics and Biostatistics and Bioinformatics Core Facilities at Moffitt Cancer Center, an NCI designated Comprehensive Cancer Center (P30-CA076292). We acknowledge Moffitt’s Melanoma Center of Excellence and the Mark Foundation for the financial support. [1] Sarnaik, A.A. et al. JCO 39, 2656-2666 (2021). [2] Creelan, B. et al. Nat Med 27, 1410-1418 (2021). [3] Cabrita, R. et al. Nature 577, 561-565 (2020). [4] Sanz, I. et al. Front Immunol 10, 2458 (2019). Citation Format: Renata Ariza Marques Rossetti, Leticia Tordesillas, Matthew Beatty, Dongliang Du, Yian Ann Chen, Amod Sarnaik, Shari Pilon-Thomas, Daniel Abate-Daga. CD40L stimulates melanoma infiltrating B cells and enhances ex vivo TIL expansion. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4055.