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Imatinib does not affect Philadelphia-chromosome-positive haematopoietic stem cells in patients achieving molecular response (MR); however, prolonged relapse-free survival can be achieved before treatment discontinuation, implying that efficient immunosurveillance has been establishedIn addition to targeting tumoural BCR–ABL1and KIToncogene products, imatinib modulates protein tyrosine kinases involved in key signalling pathways in both effector and regulatory immune cells implicated in cancer immunosurveillanceLow-dose imatinib has stimulatory effects on haematopoiesis and can contribute to immune-mediated clearance of pathogensIn patients with chronic myeloid leukaemia, imatinib elicits antigen-specific T-cell responses that can protect against relapses in patients with cytogenetically controlled or minimal diseaseImatinib boosts natural killer-cell-induced IFNα secretion and decreases regulatory T-cell numbers in patients with gastrointestinal tumours; NKp30 isoform patterns dictate the prognosis of the diseaseWe propose that novel treatment regimens combining imatinib with immunotherapies will enable long-term relapse-free survival to be achieved in a larger number of patients and will prevent the emergence of imatinib-resistant clones

Stage III metastatic melanomas require adequate adjuvant immunotherapy to prevent relapses. Prognostic factors are awaited to optimize the clinical management of these patients. The magnitude of metastatic lymph node invasion and the BRAFV600activating mutation have clinical significance. Based on a comprehensive immunophenotyping of 252 parameters per patient in paired blood and metastatic lymph nodes performed in 39 metastatic melanomas, we found that blood markers were as contributive as tumor-infiltrated lymphocyte immunotypes, and parameters associated with lymphocyte exhaustion/suppression showed higher clinical significance than those related to activation or lineage. High frequencies of CD45RA+CD4+and CD3–CD56–tumor-infiltrated lymphocytes appear to be independent prognostic factors of short progression-free survival. High NKG2D expression on CD8+tumor-infiltrated lymphocytes, low level of regulatory T-cell tumor-infiltrated lymphocytes, and low PD-L1 expression on circulating T cells were retained in the multivariate Cox analysis model to predict prolonged overall survival. Prospective studies are needed to determine whether such immunological markers may guide adjuvant therapies in stage III metastatic melanomas.

Previous studies have indicated that the infiltration of CD8+ T cells in colorectal cancer is an independent predictor of increased survival but clinical observations have suggested that the cytotoxic function of CD8+ T cells infiltrating colorectal cancer may often be limited. In this study, we have assessed the phenotype of colorectal cancer CD8+ tumor-infiltrating lymphocytes (TILs) isolated ex vivo from tumor tissue, and assessed the perforin content of TIL with respect to their location using immunohistochemistry. We found that CD8+ T cells TILs isolated from colorectal cancer are mainly composed of antigen-experienced cells of effector memory type (TEM, CD45RA-CCR7−, and CD27+/CD28− or CD27−/CD28−), and contain only minor proportions of terminally differentiated CD8+ T cells (TEMRA, CD45RA+CCR7−). The perforin content of these TILs, however, is significantly lower than that of antigen-experienced T cells in PBMCs due to the much lower levels of perforin found in the CD27-CD28− subset in TILs compared with CD8+ T cells of similar phenotype in PBMCs.Previous studies have indicated that the infiltration of CD8+ T cells in colorectal cancer is an independent predictor of increased survival but clinical observations have suggested that the cytotoxic function of CD8+ T cells infiltrating colorectal cancer may often be limited. In this study, we have assessed the phenotype of colorectal cancer CD8+ tumor-infiltrating lymphocytes (TILs) isolated ex vivo from tumor tissue, and assessed the perforin content of TIL with respect to their location using immunohistochemistry. We found that CD8+ T cells TILs isolated from colorectal cancer are mainly composed of antigen-experienced cells of effector memory type (TEM, CD45RA-CCR7−, and CD27+/CD28− or CD27−/CD28−), and contain only minor proportions of terminally differentiated CD8+ T cells (TEMRA, CD45RA+CCR7−). The perforin content of these TILs, however, is significantly lower than that of antigen-experienced T cells in PBMCs due to the much lower levels of perforin found in the CD27-CD28− subset in TILs compared with CD8+ T cells of similar phenotype in PBMCs.

Two distinct types of CpG oligodeoxynucleotide (ODN) have been identified that differ in their capacity to stimulate antigen-presenting cells: CpG-A induces high amounts of interferon-α (IFN-α) and IFN-β in plasmacytoid dendritic cells (PDCs), whereas CpG-B induces PDC maturation and is a potent activator of B cells but stimulates only small amounts of IFN-α and IFN-β. Here we examined the ability of these CpG ODNs to enhance peptide-specific CD8+ T-cell responses in human peripheral blood mononuclear cells (PBMCs). The frequency of influenza matrix–specific “memory” CD8+ T cells was increased by both types of CpG ODN, whereas the frequency of Melan-A specific “naive” CD8+ T cells increased on stimulation with CpG-B but not with CpG-A. The presence of PDCs in PBMCs was required for this CpG ODN-mediated effect. The expanded cells were cytotoxic and produced IFN-γ on peptide restimulation. Soluble factors induced by CpG-A but not CpG-B increased the granzyme-B content and cytotoxicity of established CD8+ T-cell clones, each of which was IFN-α/-β dependent. In conclusion, CpG-B seems to be superior for priming CD8+ T-cell responses, and CpG-A selectively enhances memory CD8+ T-cell responses and induces cytotoxicity. These results demonstrate distinct functional properties of CpG-A and CpG-B with regard to CD8 T cells.

Two distinct types of CpG oligodeoxynucleotide (ODN) have been identified that differ in their capacity to stimulate antigen-presenting cells: CpG-A induces high amounts of interferon-α (IFN-α) and IFN-β in plasmacytoid dendritic cells (PDCs), whereas CpG-B induces PDC maturation and is a potent activator of B cells but stimulates only small amounts of IFN-α and IFN-β. Here we examined the ability of these CpG ODNs to enhance peptide-specific CD8+T-cell responses in human peripheral blood mononuclear cells (PBMCs). The frequency of influenza matrix–specific “memory” CD8+T cells was increased by both types of CpG ODN, whereas the frequency of Melan-A specific “naive” CD8+T cells increased on stimulation with CpG-B but not with CpG-A. The presence of PDCs in PBMCs was required for this CpG ODN-mediated effect. The expanded cells were cytotoxic and produced IFN-γ on peptide restimulation. Soluble factors induced by CpG-A but not CpG-B increased the granzyme-B content and cytotoxicity of established CD8+T-cell clones, each of which was IFN-α/-β dependent. In conclusion, CpG-B seems to be superior for priming CD8+T-cell responses, and CpG-A selectively enhances memory CD8+T-cell responses and induces cytotoxicity. These results demonstrate distinct functional properties of CpG-A and CpG-B with regard to CD8 T cells.

A novel approach for the identification of tumor antigen-derived sequences recognized by CD8⁺ cytolytic T lymphocytes (CTL) consists in using synthetic combinatorial peptide libraries. Here we have screened a library composed of 3.1×10¹¹ nonapeptides arranged in a positional scanning format, in a cytotoxicity assay, to search the antigen recognized by melanoma-reactive CTL of unknown specificity. The results of this analysis enabled the identification of several optimal peptide ligands, as most of the individual nonapeptides deduced from the primary screeningwere efficiently recognized by the CTL. The results of the library screening were also analyzed with a mathematical approach based on a model of independent and additive contribution of individual amino acids to antigen recognition. This biometrical data analysis enabled the retrieval, in public databases, of the native antigenic peptide SSX-241–49, whose sequence is highly homologous to the ones deduced from the library screening, among the ones with the highest stimulatory score. These results underline the high predictive value of positional scanning synthetic combinatorial peptide library analysis and encourage its use for the identification of CTL ligands.

Telomerase is a ribonucleoprotein complex responsible for the maintenance of the length of the telomeres during cell division, which is active in germ-line cells as well as in the vast majority of tumors but not in most normal tissues. The wide expression of the human telomerase catalytic subunit (hTERT) in tumors makes it an interesting candidate vaccine for cancer. hTERT-derived peptide 540–548 (hTERT540) has been recently shown to be recognized in an HLA-A*0201-restricted fashion by T cell lines derived from peptide-stimulated peripheral blood mononuclear cells (PBMC) from healthy donors. As a first step to the inclusion of this peptide in immunotherapy clinical trials, it is crucial to assess hTERT540-specific T cell reactivity in cancer patients as wellas the ability of hTERT-specific CD8⁺ T lymphocytes to recognize and lyse hTERT-expressing target cells. Here, we have analyzed the CD8⁺ T cell response to peptide hTERT540 in HLA-A*0201 melanoma patients by using fluorescent HLA-A*0201/hTERT540 peptide tetramers. HLA-A*0201/hTERT540 tetramer⁺ CD8⁺ T cells were readily detected in peptide-stimulated PBMC from a significant proportion of patients and could be isolated by tetramer-guided cell sorting. hTERT540-specific CD8⁺ T cells were able to specifically recognize HLA-A*0201 cells either pulsed with peptide or transiently transfected with a minigene encoding the minimal epitope. In contrast, they failed to recognize hTERT-expressing HLA-A*0201⁺ target cells. Furthermore, in vitro proteasome digestion studies revealed inadequate hTERT processing. Altogether, these results raise questions on the use of hTERT540 peptide for cancer immunotherapy.

Peptide vaccines based on the use of MHC class I restricted epitopes are currently assayed for anti-tumor and anti-viral immunotherapy. With the aim of designing minimally modified, peptidase-resistant analogs, we developed a rational approach based on a detailed understanding of the degradation mechanism of peptides in serum. Degradation of murine tumor antigen P198 and human tumor antigen MAGE-3.A1 was followed by on line high performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS). This method provided high precision and sensitivity for rapid and direct analysis of degradation fragments in a complex mixture and, very importantly, precise identification of transient degradation fragments present at low concentrations. The design of structurally modified analogs, and the analysis of their degradation by on-line HPLC/ESI-MS, allowed us to demonstrate the efficiency of local modifications in the protection of a given peptide bond towards a specific peptidase activity. © 1998 John Wiley & Sons, Ltd.

Peptide vaccines based on the use of MHC class I restricted epitopes are currently assayed for anti‐tumor and anti‐viral immunotherapy. With the aim of designing minimally modified, peptidase‐resistant analogs, we developed a rational approach based on a detailed understanding of the degradation mechanism of peptides in serum. Degradation of murine tumor antigen P198 and human tumor antigen MAGE‐3.A1 was followed by on line high performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI‐MS). This method provided high precision and sensitivity for rapid and direct analysis of degradation fragments in a complex mixture and, very importantly, precise identification of transient degradation fragments present at low concentrations. The design of structurally modified analogs, and the analysis of their degradation by on‐line HPLC/ESI‐MS, allowed us to demonstrate the efficiency of local modifications in the protection of a given peptide bond towards a specific peptidase activity. © 1998 John Wiley & Sons, Ltd.

ABSTRACTγδ T lymphocytes diverge from conventional T CD8 lymphocytes for ontogeny, homing, and antigen specificity, but whether their differentiation in tumors also deviates was unknown. Using innovative analyses of our original and ~150 published single-cell RNA sequencing datasets validated by phenotyping of human tumors and murine models, here we present the first high-resolution view of human γδ T cell differentiation in cancer. While γδ T lymphocytes prominently encompass TCRVγ9 cells more differentiated than T CD8 in healthy donor’s blood, a different scenario is unveiled in tumors. Solid tumors and lymphomas are infiltrated by a majority of TCRVγnon9 γδ T cells which are quantitatively correlated and remarkably aligned with T CD8 for differentiation, exhaustion, gene expression profile, and response to immune checkpoint therapy. This cancer-wide association is critical for developing cancer immunotherapies.

ABSTRACTImmunotherapies have achieved clinical benefit in many types of cancer but remain limited to a subset of patients in colorectal cancer (CRC). Resistance to immunotherapy can be attributed in part to tissue-specific factors constraining antitumor immunity. Thus, a better understanding of how the colon microenvironment shapes the immune response to CRC is needed to identify mechanisms of resistance to immunotherapies and guide the development of novel therapeutics.In an orthotopic mouse model of MC38-CRC, tumor progression was monitored by bioluminescence imaging and the immune signatures were assessed at a transcriptional level using NanoString and at a cellular level by flow cytometry. Despite initial tumor growth in all mice, only 25% to 35% of mice developed a progressive lethal CRC while the remaining animals spontaneously rejected their solid tumor. No tumor rejection was observed in the absence of adaptive immunity, nor when MC38 cells were injected in non-orthotopic locations, subcutaneously or into the liver. We observed that progressive CRC tumors exhibited a protumor immune response, characterized by a regulatory T-lymphocyte pattern, discernible shortly post-tumor implantation, as well as suppressive myeloid cells. In contrast, tumor-rejecting mice presented an early inflammatory response and an antitumor microenvironment enriched in CD8+T cells.Taken together, our data demonstrate the role of the colon microenvironment in regulating the balance between anti or protumor immune responses. While emphasizing the relevance of the CRC orthotopic model, they set the basis for exploring the impact of the identified signatures in colon cancer response to immunotherapy.

Despite the clinical success of blocking inhibitory immune checkpoint receptors such as programmed cell death-1 (PD-1) in cancer, the mechanisms controlling the expression of these receptors have not been fully elucidated. Here, we identify a post-transcriptional mechanism regulating PD-1 expression in T cells. Upon activation, the PDCD1mRNA and ribonucleoprotein complexes coalesce into stress granules that require microtubules and the kinesin 1 molecular motor to proceed to translation. Hence, PD-1 expression is highly sensitive to microtubule or stress granule inhibitors targeting this pathway. Evidence from healthy donors and cancer patients reveals a common regulation for the translation of CTLA4, LAG3, TIM3, TIGIT, and BTLAbut not of the stimulatory co-receptors OX40, GITR, and 4-1BBmRNAs. In patients, disproportionality analysis of immune-related adverse events for currently used microtubule drugs unveils a significantly higher risk of autoimmunity. Our findings reveal a fundamental mechanism of immunoregulation with great importance in cancer immunotherapy.

A strategic challenge facing clinicians treating patients afflicted with non-small cell lung cancer (NSCLC) is the development of approaches that combine conventional and novel therapies, including targeted therapies and immunotherapeutics. In a recent study, we explored the correlation between the expression of the tumor antigen family MAGE-A and the presence of EGFRand KRASgene mutations in a large cohort of resected NSCLC patient specimens.

In a recent study, we have demonstrated that T helper type 1 (TH1) cells specific for the tumor antigen NY-ESO-1 are amplified at ovarian tumor sites but are not “perverted” into immunosuppressive FOXP3+regulatory T cells (Tregs). These findings encourage the development of protocols aiming to eliminate, or inactivate, FOXP3+Tregs and reinforce Type I anticancer immunity, to improve clinical outcomes.

Whereas preclinical investigations and clinical studies have established that CD8+T cells can profoundly affect cancer progression, the underlying mechanisms are still elusive. Challenging the prevalent view that the beneficial effect of CD8+T cells in cancer is solely attributable to their cytotoxic activity, several reports have indicated that the ability of CD8+T cells to promote tumor regression is dependent on their cytokine secretion profile and their ability to self-renew. Evidence has also shown that the tumor microenvironment can disarm CD8+T cell immunity, leading to the emergence of dysfunctional CD8+T cells. The existence of different types of CD8+T cells in cancer calls for a more precise definition of the CD8+T cell immune phenotypes in cancer and the abandonment of the generic terms “pro-tumor” and “antitumor.” Based on recent studies investigating the functions of CD8+T cells in cancer, we here propose some guidelines to precisely define the functional states of CD8+T cells in cancer.