Adoptive T cell therapy (ACT) with tumor-infiltrating lymphocytes (TIL) can induce prolonged clinical responses in selected patients with gastrointestinal tumors while a significant fraction of patients do not respond. The association between immune profiles and antigenic specificity of TIL and clinical responses remains unclear. We addressed these issues, including the recognition of neoantigens, in order to explore the potential of personalized cell-based and vaccine therapy in colorectal cancer (CRC).
Tumor specimens of primary (n = 11) and metastatic (n = 12) colon adenocarcinoma were dissected in fragments and cultured with IL-2 (6000U/ml) for 17-28 days. TIL were analyzed by multiparametric flow cytometric analyses and interrogated with private sets of predicted neoepitopes derived from non-synonymous mutations. T-cell responses against neoepitopes were detected by IFNγ ELISpot and validated with peptide-MHC multimers.
TIL (i.e.>50x106 cells, mean±SEM 239±52x106) were obtained from 7 and 8 patients with primary and metastatic colon adenocarcinoma, respectively. In primary tumors, the highest potential for TIL expansion was observed for microsatellite-instable tumors as opposed to microsatellite-stable (MSS) tumors (mean±SEM 435±194x106 vs. 84±34x106 cells; p = 0.05, Mann-U). TIL yield was similar in primary and metastatic tumors, however in metastatic tumors the CD4/CD8 T cells ratio was higher (median 11 vs. 1; p = 0.002, Mann-U) and inversely correlated with TIL expansion (rs -0.8; p = 0.005). Most (>90%) T cells had a phenotype of effector-memory (CCR7-CD45RA-) activated (HLADR+PD1+TIM3+) cells. Mutational load (ranging from 23 to 2760) and potential neoepitopes (from 25 to 2373) were determined and, of interest, initial screening experiments identified 2% of neoantigen specific-TIL (mutMALT1; V380A) in a representative MSS metastatic tumor harboring only 47 missense mutations.
We demonstrate the spectrum of TIL expansion across CRC subtypes and stages, including the validation of neoepitopes in a non-hypermutated advanced tumor. These observations stress the potential of CRC patients for different strategies of personalized immunotherapy.
Clinical trial identification
Legal entity responsible for the study
Centre de Thérapies Expérimentales. Département d'oncologie. Centre Hospitalier Universitaire Vaudois
Centre de Thérapies Expérimentales. Département d'oncologie. Centre Hospitalier Universitaire Vaudois. This Research Project was supported by ESMO with the aid of a grant from Amgen. Any views, opinions, findings, conclusions, or recommendations expressed in this material are those solely of the authors and do not necessarily reflect those of ESMO or Amgen
All authors have declared no conflicts of interest.