License to kill: microsatellite instability and immune contexture

Co-expression of PD-1 with TIGIT or PD-1 with TIM-3 on tumor-infiltrating CD8+ T cells showed synergistic effects on improved disease-free survival in treatment-naïve CRC patients

Immune checkpoints (ICs) are highly expressed on tumor-infiltrating immune cells (TIICs) in different malignancies, including colorectal cancer (CRC). T cells play crucial roles in shaping CRC, and their presence in the tumor microenvironment (TME) has proven to be one of the best predictors of clinical outcomes. A crucial component of the immune system is cytotoxic CD8⁺ T cells (CTLs), which play decisive roles in the prognosis of CRC. In this study, we investigated associations of immune checkpoints expressed on tumor-infiltrating CD8⁺ T cells with disease-free survival (DFS) in 45 naïve-treatment CRC patients. First, we examined the associations of single ICs, and found that CRC patients with higher levels of T-cell immunoglobulin and ITIM-domain (TIGIT), T-cell immunoglobulin and mucin domain-3 (TIM-3) and programmed cell death-1 (PD-1) CD8⁺ T cells tended to have longer DFS. Interestingly, when PD-1 expression was combined with other ICs, there were more evident and stronger associations between higher levels of PD-1⁺ with TIGIT⁺ or PD-1⁺ with TIM-3⁺ tumor-infiltrating CD8⁺ T cells and longer DFS. Our findings for TIGIT were validated in The Cancer Genome Atlas (TCGA) CRC dataset. This study is the first to report on the association of co-expression of PD-1 with TIGIT and PD-1 with TIM-3 in CD8⁺ T cells and improved DFS in treatment-naïve CRC patients. This work highlights the significance of immune checkpoint expression on tumor-infiltrating CD8⁺ T cells as critical predictive biomarkers, especially when co-expression of different ICs is considered.

CDT1 drives replication overlicensing and enhances tumorigenesis in the gut†

Colorectal carcinoma (CRC) is one of the most common forms of malignancy in the Western world. Recent decades have witnessed enormous progress in our understanding of the mechanisms that sustain CRC, even though the factors implicated in the initiation and progression of this neoplasia are not fully understood. A recent study published in The Journal of Pathology looked at the consequences of hyperactivity of chromatin licensing and DNA replication factor 1 (CDT1), a regulator of DNA replication that is produced in excess in CRC, on the course of intestinal tumorigenesis. Mice engineered to selectively overexpress CDT1 and/or lack Geminin, an inhibitor of CDT1, in the intestinal epithelium were more susceptible to experimental intestinal tumorigenesis compared to wild-type mice. This work supports the pro-tumorigenic role of CDT1 and suggests the potential prognostic value of this protein in CRC. © 2022 The Pathological Society of Great Britain and Ireland.

PD-1 Blockade Combined with Heated Intraperitoneal Chemotherapy Improves Outcome in Experimental Peritoneal Metastases from Colonic Origin in a Murine Model

BACKGROUND

Heated intraperitoneal chemotherapy (HIPEC) was shown to induce immunogenicity of peritoneal metastases from colorectal cancer (PM-CRC) by induction of immunogenic cell death. We aimed to explore whether the addition of a checkpoint inhibitor would augment the effect of HIPEC in an experimental murine model of PM-CRC.

METHODS

PM-CRC was established in C57BL mice by intraperitoneal inoculation of MC38 colon cancer cells. HIPEC was administered using the closed technique with mitomycin C (MMC). Clinical and immunological parameters were compared between animals treated with HIPEC alone and those treated with HIPEC + anti-programmed death receptor-1 (aPD-1).

RESULTS

MMC-based HIPEC increased the overall survival of animals compared with sham-treated animals (22.8; 95% confidence interval [CI] 21.14-24.53 vs. 18.9 days; 95% CI 17.6-20.3, p < 0.001). The extent of peritoneal disease as measured by the modified peritoneal carcinomatosis index was also reduced by HIPEC. This clinical benefit was accompanied by increased infiltration of CD8⁺, CD68⁺, and CD20⁺ cells into tumor metastases in HIPEC-treated animals compared with sham-treated animals. We identified heat shock protein (HSP) 90 as a potential immunogenic cell death protein whose expression is increased under HIPEC conditions (fold change: 2.37 ± 1.5 vs. 1 without HIPEC, p < 0.05). Combined HIPEC + PD-1 treatment ameliorated survival compared with HIPEC alone and sham treatment (24.66; 95% CI 20.13-29.2 vs. 19; 95% CI 15.85-22.14 and 14.33 days; 95% CI 9.6-19.04, respectively; p = 0.008). This clinical effect was accompanied by increased CD8⁺ tumor infiltration.

CONCLUSIONS

HIPEC induced the expression of immunogenic cell death signals that can support an anti-tumor immune response. This response can be further exploited by a checkpoint inhibitor.

PD-1 expression, among other immune checkpoints, on tumor-infiltrating NK and NKT cells is associated with longer disease-free survival in treatment-naïve CRC patients

A variety of variables, such as microsatellite instability or inflammatory mediators, are critical players in the development and progression of colorectal cancer (CRC). Natural killer (NK) and natural killer T (NKT) cells are involved in the prognoses of CRC. Immunological components of the tumor microenvironment (TME) impact cancer progression and therapeutic responses. We report that CRC patients with higher frequencies of tumor-infiltrating PD-1+ NK and NKT cells had significantly longer disease-free survival (DFS) than patients with lower frequencies. In agreement with that, patients with higher frequencies of tumor-infiltrating PD-1− NK and NKT cells showed shorter DFS. There were no significant associations between tumor-infiltrating PD-1+TIM-3+, PD-1+TIGIT+, PD-1+ICOS+, PD-1+LAG-3+ NK cells, and PD-1+TIM-3+, PD-1+TIGIT+, and PD-1+LAG-3+ NKT cells with DFS. This study highlights the significance of PD-1 expression on tumor-infiltrating NK and NKT cells and its association with disease prognoses in CRC patients.

Advances in the Lung Cancer Immunotherapy Approaches

Despite the progress in the comprehension of LC progression, risk, immunologic control, and treatment choices, it is still the primary cause of cancer-related death. LC cells possess a very low and heterogeneous antigenicity, which allows them to passively evade the anticancer defense of the immune system by educating cytotoxic lymphocytes (CTLs), tumor-infiltrating lymphocytes (TILs), regulatory T cells (Treg), immune checkpoint inhibitors (ICIs), and myeloid-derived suppressor cells (MDSCs). Though ICIs are an important candidate in first-line therapy, consolidation therapy, adjuvant therapy, and other combination therapies involving traditional therapies, the need for new predictive immunotherapy biomarkers remains. Furthermore, ICI-induced resistance after an initial response makes it vital to seek and exploit new targets to benefit greatly from immunotherapy. As ICIs, tumor mutation burden (TMB), and microsatellite instability (MSI) are not ideal LC predictive markers, a multi-parameter analysis of the immune system considering tumor, stroma, and beyond can be the future-oriented predictive marker. The optimal patient selection with a proper adjuvant agent in immunotherapy approaches needs to be still revised. Here, we summarize advances in LC immunotherapy approaches with their clinical and preclinical trials considering cancer models and vaccines and the potential of employing immunology to predict immunotherapy effectiveness in cancer patients and address the viewpoints on future directions. We conclude that the field of lung cancer therapeutics can benefit from the use of combination strategies but with comprehension of their limitations and improvements.

The Role of Interleukin-7 in the Formation of Tertiary Lymphoid Structures and Their Prognostic Value in Gastrointestinal Cancers

Immunotherapies for the treatment of solid tumors continue to develop in preclinical and clinical research settings. Unfortunately, for many patients the tumor fails to respond or becomes resistant to therapies such as checkpoint inhibitors (CPIs) targeting programmed cell death protein-1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T lymphocyte antigen-4 (CTLA-4). In many cancers, failed response to CPIs can be attributed to poor T cell infiltration, dominant immunosuppression, and exhausted immune responses. In gastrointestinal (GI) cancers T cell infiltration can be dismal, with several reports finding that CD8⁺ T cells compose less than 2% of all cells within the tumor. Organized aggregates of lymphocytes, antigen-presenting cells, and vessels, together termed tertiary lymphoid structures (TLSs), are hypothesized to be a major source of T cells within solid tumors. The intratumoral formation of these organized immune centers appears to rely on intricate cytokine and chemokine signaling to heterogeneous cell populations such as B and T cells, innate lymphoid cells, fibroblasts, and dendritic cells. In GI cancers, the presence and density of TLSs provide prognostic value for predicting outcome and survival. Further, TLS presence and density associates with favorable responses to CPIs in many cancers. This review highlights the prognostic value of TLSs in GI cancers, the role of the homeostatic cytokine interleukin-7 (IL-7) in TLS formation, and the induction of TLSs in solid tumors by novel therapeutics.

Homologous recombination deficiency is inversely correlated with microsatellite instability and identifies immunologically cold tumors in most cancer types

Homologous recombination deficiency (HRD) leads to DNA double‐strand breaks and can be exploited by the use of poly (ADP‐ribose) polymerase (PARP) inhibitors to induce synthetic lethality. Extending the original therapeutic concept, the role of HRD is currently being investigated in clinical trials testing immune checkpoint blockers alone or in combination with PARP inhibitors, but the relationship between HRD and immune cell context in cancer is incompletely understood. We analyzed the association between immune cell composition, gene expression, and HRD in 9,041 tumors of 32 solid cancer types from The Cancer Genome Atlas (TCGA). The numbers of genomic scars were quantified by the HRD sum score (HRDsum) including loss of heterozygosity, large‐scale state transitions, and telomeric allelic imbalance. The T‐cell inflamed gene expression profile correlated weakly, but significantly positively, with HRDsum across cancer types (ρ = 0.17). Within individual cancer types, a significantly positive correlation was observed only in breast cancer, ovarian cancer, and four other cancer types, but not in the remaining 26 cancer types. HRDsum and tumor mutational burden (TMB) correlated significantly positively across cancer types (ρ = 0.42) and within 18 cancer types. HRDsum and a proliferation metagene correlated significantly positively across cancer types (ρ = 0.52) and within 20 cancer types. Mismatch repair deficiency and HRD as well as proofreading deficiency showed a high level of exclusivity. High HRD scores were associated with an immunologically activated tumor microenvironment only in a minority of cancer types. Our data favor the combination of genetic markers, complex genomic markers (including HRDsum and TMB), and other molecular markers (including proliferation scores) for a precise and comprehensive read‐out of the tumor biology and an individually tailored treatment.

Know thy immune self and non-self: Proteomics informs on the expanse of self and non-self, and how and where they arise

T cells play an important role in the adaptive immune response to a variety of infections and cancers. Initiation of a T cell mediated immune response requires antigen recognition in a process termed MHC (major histocompatibility complex) restri ction. A T cell antigen is a composite structure made up of a peptide fragment bound within the antigen-binding groove of an MHC-encoded class I or class II molecule. Insight into the precise composition and biology of self and non-self immunopeptidomes is essential to harness T cell mediated immunity to prevent, treat, or cure infectious diseases and cancers. T cell antigen discovery is an arduous task! The pioneering work in the early 1990s has made large-scale T cell antigen discovery possible. Thus, advancements in mass spectrometry coupled with proteomics and genomics technologies make possible T cell antigen discovery with ease, accuracy, and sensitivity. Yet we have only begun to understand the breadth and the depth of self and non-self immunopeptidomes because the molecular biology of the cell continues to surprise us with new secrets directly related to the source, and the processing and presentation of MHC ligands. Focused on MHC class I molecules, this review, therefore, provides a brief historic account of T cell antigen discovery and, against a backdrop of key advances in molecular cell biologic processes, elaborates on how proteogenomics approaches have revolutionised the field.

Immunoprofiling: An Encouraging Method for Predictive Factors Examination in Lung Cancer Patients Treated with Immunotherapy

The efficiency of immunotherapy using monoclonal antibodies that inhibit immune checkpoints has been proven in many clinical studies and well documented by numerous registration approaches. To date, PD-L1 expression on tumor and immune cells, tumor mutation burden (TMB), and microsatellite instability (MSI) are the only validated predictive factors used for the qualification of cancer patients for immunotherapy. However, they are not the ideal predictive factors. No response to immunotherapy could be observed in patients with high PD-L1 expression, TMB, or MSI. On the other hand, the effectiveness of this treatment method also may occur in patients without PD-L1 expression or with low TMB and with microsatellite stability. When considering the best predictive factor, we should remember that the effectiveness of immunotherapy relies on an overly complex process depending on many factors. To specifically stimulate lymphocytes, not only should their activity in the tumor microenvironment be unlocked, but above all, they should recognize tumor antigens. The proper functioning of the anticancer immune system requires the proper interaction of many elements of the specific and non-specific responses. For these reasons, a multi-parameter analysis of the immune system at its different activity levels is considered a very future-oriented predictive marker. Such complex immunological analysis is performed using modern molecular biology techniques. Based on the gene expression studies, we can determine the content of individual immune cells within the tumor, its stroma, and beyond. This includes all cell types from active memory cytotoxic T cells, M1 macrophages, to exhausted T cells, regulatory T cells, and M2 macrophages. In this article, we summarize the possibilities of using an immune system analysis to predict immunotherapy efficacy in cancer patients. Moreover, we present the advantages and disadvantages of immunoprofiling as well as a proposed future direction for this new method of immune system analysis in cancer patients who receive immunotherapy.