Prediction of improved survival in patients with pancreatic cancer via IL-21 enhanced detection of mesothelin epitope-reactive T-cell responses

Targeting Neoepitopes to Treat Solid Malignancies: Immunosurgery

Successful outcome of immune checkpoint blockade in patients with solid cancers is in part associated with a high tumor mutational burden (TMB) and the recognition of private neoantigens by T-cells. The quality and quantity of target recognition is determined by the repertoire of ‘neoepitope’-specific T-cell receptors (TCRs) in tumor-infiltrating lymphocytes (TIL), or peripheral T-cells. Interferon gamma (IFN-γ), produced by T-cells and other immune cells, is essential for controlling proliferation of transformed cells, induction of apoptosis and enhancing human leukocyte antigen (HLA) expression, thereby increasing immunogenicity of cancer cells. TCR αβ-dependent therapies should account for tumor heterogeneity and availability of the TCR repertoire capable of reacting to neoepitopes and functional HLA pathways. Immunogenic epitopes in the tumor-stroma may also be targeted to achieve tumor-containment by changing the immune-contexture in the tumor microenvironment (TME). Non protein-coding regions of the tumor-cell genome may also contain many aberrantly expressed, non-mutated tumor-associated antigens (TAAs) capable of eliciting productive anti-tumor immune responses. Whole-exome sequencing (WES) and/or RNA sequencing (RNA-Seq) of cancer tissue, combined with several layers of bioinformatic analysis is commonly used to predict possible neoepitopes present in clinical samples. At the ImmunoSurgery Unit of the Champalimaud Centre for the Unknown (CCU), a pipeline combining several tools is used for predicting private mutations from WES and RNA-Seq data followed by the construction of synthetic peptides tailored for immunological response assessment reflecting the patient’s tumor mutations, guided by MHC typing. Subsequent immunoassays allow the detection of differential IFN-γ production patterns associated with (intra-tumoral) spatiotemporal differences in TIL or peripheral T-cells versus TIL. These bioinformatics tools, in addition to histopathological assessment, immunological readouts from functional bioassays and deep T-cell ‘adaptome’ analyses, are expected to advance discovery and development of next-generation personalized precision medicine strategies to improve clinical outcomes in cancer in the context of i) anti-tumor vaccination strategies, ii) gauging mutation-reactive T-cell responses in biological therapies and iii) expansion of tumor-reactive T-cells for the cellular treatment of patients with cancer.

KRAS RENAISSANCE(S) in Tumor Infiltrating B Cells in Pancreatic Cancer

KRAS is a driver mutation for malignant transformation. It is found in 30% of all cancers and in 90% of pancreatic cancers. The identification of small molecules selectively inhibiting KRAS mutants has been challenging, yet mutant KRAS has recently been shown to be targeted by tumor-infiltrating lymphocyte (TIL)-derived T cells that confer tumor regression upon adoptive transfer. Furthermore, a human IgG1 monoclonal antibody interfering with mutant KRAS function inside the cell has been described to inhibit growth of KRAS-mutant xenografts in tumor-bearing mice. B cells have been described to infiltrate pancreatic cancer and may be associated with tertiary lymphoid structures associated with good prognosis, or, in contrast, promote tumor growth. However, their function, nor their antigen-specificity has been clearly defined. We discuss here the presence of tumor-infiltrating B cells (TIB) in patients with pancreatic cancer that produce KRAS-mutant specific IgG, underlining that intratumoral T and B cells may exclusively target mutant KRAS. KRAS-specific IgG may, therefore, serve as a readout of the activation of both arms of the anti-tumor adaptive immune armament although some B-cell populations may promote tumor progression.