Abstract LB-263: Enhancing of CD8+ tumor-infiltrating lymphocyte expansion from triple-negative breast cancer patients using of 41BB costimulation

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background: Triple negative breast cancer (TNBC) is the most aggressive form of breast cancer with few treatment options. Recently, it was shown that infiltration of TNBC with CD8+ tumor-infiltrating lymphocytes (TIL) is associated with improved prognosis, suggesting that T-cell responses at the tumor site can be harnessed as an autologous T-cell therapy for TNBC. Although TIL therapy has been developed for solid tumors such as melanoma, cervical, and ovarian cancer, whether TIL, especially CD8+ cells, with effector-memory properties can be expanded with reasonable yields from primary TNBC is not known. Given the high rates of relapse and refractory nature of recurrent TNBC disease, autologous TIL therapy may offer a life-saving option for these patients. Moreover, methods to facilitate CD8+ TIL expansion from TNBC are also desirable given the cytotoxic potential of these cells. One approach to address this need is to manipulate TNF-R family member signaling, such as 41BB/CD137, to provide potent costimulatory signals for CD8+ T-cell activation and division. In this study, we established a method of isolating and generating TIL from patients with primary TNBC surgical specimens and core biopsies using an agonistic 41BB/CD137 antibody. Patients and methods: Four primary human TNBC tumor samples were obtained by surgical resection or core biopsy after neoadjuvant chemotherapy. Small tumor fragments were cultured in 24-well plates in medium containing 3000 IU/ml IL-2, or 3000 IU/ml IL-2 plus 10 μg/ml added agonistic anti-41BB IgG4 (BMS663513). Viable cell numbers and the expression of CD3, CD8, CD4, CD27, CD28, CCR7, CD45RA, CD56, CD16, Granzyme B, and Perforin was determined by flow cytometry on days 7, 14, 21, 28, and 35 after culture set-up. Cytotoxic function of the TIL was evaluated by measuring Caspase 3 cleavage in target cells. Results: Although TIL were successfully expanded from the tumor fragments in 4/4 tumor samples, IL-2 alone yielded fewer cells than IL-2 together with 41BB costimulation provided early during the culture. Anti-41BB markedly increased the percentage and yield of CD8+CD3+ T cells at all times (6.34x106 vs , 202x106, P<0.01). However, the resulting CD8+ cells had decreased CD27 expression coincident with increased CD70 when anti-41BB was added. 41BB costimulation also increased the cytotoxic T-cell activity of the expanded TIL. The expanded TIL could also be cryopreserved and later expanded using anti-CD3 and IL-2. Conclusions: We have established a method to expand CD8+ TIL with cytotoxic activity with high yield from small samples of remaining primary tumor after neoadjuvant chemotherapy using IL-2. Provision of 41BB costimulation immediately upon tumor fragment culture initiation was critical in enhancing the rate and yield of CD8+ T cells with increased effector function; these could be cryopreserved and later thawed with high viability for secondary expansion. Our results support further development of an autologous TIL expansion protocol after neoadjuvant therapy for use in an adoptive cell therapy approach to treat TNBC recurrence or metastasis. Citation Format: Michiko Harao, Elizabeth A. Mittendorf, Gildy V. Babiera, Naoto T. Ueno, Laszlo G. Radvanyi. Enhancing of CD8+ tumor-infiltrating lymphocyte expansion from triple-negative breast cancer patients using of 41BB costimulation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr LB-263. doi:10.1158/1538-7445.AM2014-LB-263