Enrichment of CD8+ cells from melanoma tumor-infiltrating lymphocyte cultures reveals tumor reactivity for use in adoptive cell therapy.

Adoptive cell therapy (ACT) using tumor-infiltrating lymphocytes (TIL) for metastatic melanoma has shown objective response rates as high as 72%. The successful application of this therapy requires the selection of unique tumor-reactive lymphocyte cultures for each patient. This is a technically and logistically difficult undertaking, and patients who do not have tumor-reactive TIL are not considered eligible for treatment. To simplify the methods of TIL generation and extend TIL-based immunotherapy to additional patients, methods were developed to use unselected, minimally cultured ("young") TIL. Young TIL cultures contain a variable number of CD8(+), CD4(+), and CD3(-)CD56(+) natural killer cells. In this study we retrospectively investigated a role for these subsets in the clinical outcome of patients treated with TIL derived from selected microcultures. This analysis demonstrated a suggestive but nonsignificant association between the number of CD8(+) cells administered and tumor regression. We therefore investigated the feasibility of selecting CD8(+) cells from young TIL cultures for ACT therapy. The available methods for clinical scale CD8(+) enrichment proved inadequate for TIL, so an optimized CD8(+) enrichment method was developed and is reported here. We observed that CD8 (+)enrichment of some TIL cultures revealed in vitro tumor recognition that was not evident in bulk culture, and an improved in vitro recognition of tumor in other TIL cultures. In addition, the enriched CD8(+) young TIL expanded more reliably and predictably in rapid expansions than the bulk TIL. Thus, optimized CD8(+) selection combines the benefits of antigen-selected TIL and young TIL for generating lymphocyte cultures for ACT, and should be evaluated in cell transfer therapy protocols.

Minimally cultured tumor-infiltrating lymphocytes display optimal characteristics for adoptive cell therapy.

Adoptive cell therapy (ACT) with tumor-reactive lymphocytes in patients with refractory melanoma can result in tumor regression and prolonged survival. Generating tumor-reactive lymphocyte cultures is technically difficult and resource intensive; these limitations have restricted the widespread application of ACT. Tumor-infiltrating lymphocytes (TIL) from melanoma contain tumor antigen-reactive cells. The "standard" method for producing TIL cultures for clinical administration requires extended in vitro expansion in interleukin-2, then identification of tumor-reactive cells by immunologic assays. We show here that limitations in reagents and methods during screening underrepresent the actual reactivity of TIL cultures. Furthermore, the extended culture times necessitated by the screening assays resulted in telomere shortening and reduced expression of CD27 and CD28 in the TIL cultures, properties that our prior studies showed are correlated with in vivo persistence and clinical response. We have thus developed an alternative "young" TIL method that demonstrated superior in vitro attributes compared with standard TIL. This approach uses the entire resected tumor to rapidly expand TIL for administration without in vitro testing for tumor recognition. Our observations suggest that younger TIL can have an undetermined but high level of antigen reactivity, and other advantageous attributes such as long telomeres and high levels of CD27 and CD28. We suggest that minimally cultured, unselected lymphocytes represent an alternative strategy for generating TIL cultures suitable for use in ACT that, if effective in vivo, may facilitate the widespread application of this approach to a broader population of patients with melanoma.