Alfred Zippelius

Effector Function of Human Tumor-Specific CD8 T Cells in Melanoma Lesions: A State of Local Functional Tolerance

Although tumor-specific CD8 T-cell responses often develop in cancer patients, they rarely result in tumor eradication. We aimed at studying directly the functional efficacy of tumor-specific CD8 T cells at the site of immune attack. Tumor lesions in lymphoid and nonlymphoid tissues (metastatic lymph nodes and soft tissue/visceral metastases, respectively) were collected from stage III/IV melanoma patients and investigated for the presence and function of CD8 T cells specific for the tumor differentiation antigen Melan-A/MART-1. Comparative analysis was conducted with peripheral blood T cells. We provide evidence that in vivo-priming selects, within the available naive Melan-A/MART-1-specific CD8 T-cell repertoire, cells with high T-cell receptor avidity that can efficiently kill melanoma cells in vitro. In vivo, primed Melan-A/MART-1-specific CD8 T cells accumulate at high frequency in both lymphoid and nonlymphoid tumor lesions. Unexpectedly, however, whereas primed Melan-A/MART-1-specific CD8 T cells that circulate in the blood display robust inflammatory and cytotoxic functions, those that reside in tumor lesions (particularly in metastatic lymph nodes) are functionally tolerant. We show that both the lymph node and the tumor environments blunt T-cell effector functions and offer a rationale for the failure of tumor-specific responses to effectively counter tumor progression.

Selective Survival of Naturally Occurring Human CD4+CD25+Foxp3+ Regulatory T Cells Cultured with Rapamycin

Naturally occurring CD4+CD25+ regulatory T (nTreg) cells are essential for maintaining T cell tolerance to self Ags. We show that discrimination of human Treg from effector CD4+CD25+ non-nTreg cells and their selective survival and proliferation can now be achieved using rapamycin (sirolimus). Human purified CD4+CD25high T cell subsets stimulated via TCR and CD28 or by IL-2 survived and expanded up to 40-fold in the presence of 1 nM rapamycin, while CD4+CD25low or CD4+CD25− T cells did not. The expanding pure populations of CD4+CD25high T cells were resistant to rapamycin-accelerated apoptosis. In contrast, proliferation of CD4+CD25− T cells was blocked by rapamycin, which induced their apoptosis. The rapamycin-expanded CD4+CD25high T cell populations retained a broad TCR repertoire and, like CD4+ CD25+ T cells freshly obtained from the peripheral circulation, constitutively expressed CD25, Foxp3, CD62L, glucocorticoid-induced TNFR family related protein, CTLA-4, and CCR-7. The rapamycin-expanded T cells suppressed proliferation and effector functions of allogeneic or autologous CD4+ and CD8+ T cells in vitro. They equally suppressed Ag-specific and nonspecific responses. Our studies have defined ex vivo conditions for robust expansion of pure populations of human nTreg cells with potent suppressive activity. It is expected that the availability of this otherwise rare T cell subset for further studies will help define the molecular basis of Treg-mediated suppression in humans.

Limitations of reverse-transcriptase polymerase chain reaction analyses for detection of micrometastatic epithelial cancer cells in bone marrow.

PURPOSE This study was designed to evaluate the potential of reverse-transcriptase polymerase chain reaction (RT-PCR) analyses for the detection of micrometastatic carcinoma cells in bone marrow (BM). PATIENTS AND METHODS The specificity of RT-PCR assays with primers specific for various tumor-associated and organ-specific mRNA species was examined by analysis of 53 BM aspirates from control patients with no epithelial malignancy. In addition, BM samples from 63 patients with prostate cancer (n = 53) or breast cancer (n = 10) were analyzed by RT-PCR with primers specific for prostate-specific antigen (PSA) mRNA. As a reference method, all samples were analyzed simultaneously by an established immunocytochemical assay, using monoclonal antibodies (mAbs) against cytokeratins (CK) for tumor-cell detection. RESULTS Seven of eight marker species could be detected in a considerable number of BM samples from control patients: epithelial glycoprotein-40 (EGP-40; 53 of 53 samples), desmoplakin I (DPI I; five of five), carcinoembryonic antigen (CEA; five of 19), erb-B2 (five of seven), erb-B3 (six of seven), prostate-specific membrane antigen (PSM; four of nine), and CK18 (five of seven). Only PSA mRNA was not detected in any of the 53 control BM samples. In serial dilution experiments, the PSA RT-PCR assay was able to detect five LNCaP prostate carcinoma cells in 4 x 10(6) BM cells. CK-positive cells were found in 20 patients (37.7%) with prostate cancer, while PSA mRNA was found in only 15 (28.3%; P = .04). Moreover, despite the recent observation that PSA is also expressed in mammary carcinomas, none of the 10 CK-positive BM samples were PSA mRNA-positive. CONCLUSION Limiting factors in the detection of micrometastatic tumor cells by RT-PCR are (1) the illegitimate transcription of tumor-associated or epithelial-specific genes in hematopoietic cells, and (2) the deficient expression of the marker gene in micrometastatic tumor cells.

Four Functionally Distinct Populations of Human Effector-Memory CD8+ T Lymphocytes

In humans, the pathways of memory and effector T cell differentiation remain poorly defined. We have dissected the functional properties of ex vivo effector-memory (EM) CD45RA−CCR7− T lymphocytes present within the circulating CD8+ T cell pool of healthy individuals. Our studies show that EM T cells are heterogeneous and are subdivided based on differential CD27 and CD28 expression into four subsets. EM1 (CD27+CD28+) and EM4 (CD27−CD28+) T cells express low levels of effector mediators such as granzyme B and perforin and high levels of CD127/IL-7Rα. EM1 cells also have a relatively short replicative history and display strong ex vivo telomerase activity. Therefore, these cells are closely related to central-memory (CD45RA−CCR7+) cells. In contrast, EM2 (CD27+CD28−) and EM3 (CD27−CD28−) cells express mediators characteristic of effector cells, whereby EM3 cells display stronger ex vivo cytolytic activity and have experienced larger numbers of cell divisions, thus resembling differentiated effector (CD45RA+CCR7−) cells. These data indicate that progressive up-regulation of cytolytic activity and stepwise loss of CCR7, CD28, and CD27 both characterize CD8+ T cell differentiation. Finally, memory CD8+ T cells not only include central-memory cells but also EM1 cells, which differ in CCR7 expression and may therefore confer memory functions in lymphoid and peripheral tissues, respectively.

Thymic selection generates a large T cell pool recognizing a self-peptide in humans.

The low frequency of self-peptide–specific T cells in the human preimmune repertoire has so far precluded their direct evaluation. Here, we report an unexpected high frequency of T cells specific for the self-antigen Melan-A/MART-1 in CD8 single–positive thymocytes from human histocompatibility leukocyte antigen-A2 healthy individuals, which is maintained in the peripheral blood of newborns and adults. Postthymic replicative history of Melan-A/MART-1–specific CD8 T cells was independently assessed by quantifying T cell receptor excision circles and telomere length ex vivo. We provide direct evidence that the large T cell pool specific for the self-antigen Melan-A/MART-1 is mostly generated by thymic output of a high number of precursors. This represents the only known naive self-peptide–specific T cell repertoire directly accessible in humans.

Ex Vivo IFN-γ Secretion by Circulating CD8 T Lymphocytes: Implications of a Novel Approach for T Cell Monitoring in Infectious and Malignant Diseases

To elucidate the functional heterogeneity of Ag-specific T lymphocyte populations, we combined labeling of lymphocytes with MHC/peptide tetramers and a cell surface affinity matrix for IFN-γ. Magnetic cell sorting of IFN-γ-positive lymphocytes allowed the selective enrichment and identification of live Ag-specific cytokine-secreting cells by flow cytometry. Naive, memory, and effector Ag-specific populations were evaluated in healthy HLA-A2 individuals. Significant fractions of influenza- and CMV-specific cells secreted IFN-γ upon challenge with cognate peptide, consistent with an effector/memory status. The sensitivity of the approach allowed the detection of significant numbers of CMV-specific IFN-γ-secreting cells ex vivo (i.e., without Ag stimulation). This was not apparent when using previously described assays, namely, ELISPOT or intracellular IFN-γ staining (cytospot). CD8+ T cells specific for the melamoma-associated Ag Melan-A/MART-1 did not produce IFN-γ upon challenge with cognate peptide, reminiscent with their naive functional state in healthy individuals. In contrast, CD45RAlow Melan-A/MART-1 tumor-specific cells from three of three melanoma patients presented levels of activity similar to those found for influenza- or CMV virus-specific lymphocytes, compatible with a functional differentiation into competent effector/memory T lymphocytes in vivo. Notably, a sizable fraction of Melan-A/MART-1-specific cells from a patient secreted IFN-γ ex vivo following peptide-based vaccination. Thus, the high sensitivity of the assay provides a valuable tool to monitor effector T cell responses in different clinical situations.

Antigenicity and immunogenicity of Melan-A/MART-1 derived peptides as targets for tumor reactive CTL in human melanoma.

Summary: Some cancer patients mount spontaneous T‐ and B‐cell responses against their tumor cells. Autologous tumor reactive CD8 cytolytic T lymphocyte (CTL) and CD4 T‐cell clones as well as antibodies from these patients have been used for the identification of genes encoding the target antigens. This knowledge opened the way for new approaches to the immunotherapy of cancer. In this review, we describe the characterization of the structure‐function properties of the melanocyte/melanoma tumor antigen Melan‐A/MART‐1, the assessment of the T‐cell repertoire available against this antigen in healthy individuals, and the analysis of naturally acquired and/or vaccine‐induced CTL responses to this antigen in patients with metastatic melanoma.

Acute heart failure due to autoimmune myocarditis under pembrolizumab treatment for metastatic melanoma

Antibodies that stimulate the immune system by targeting inhibitory T cell receptors were successfully introduced into oncological practice and are capable to overcome tumor-induced immune evasion. In particular, targeting of the inhibitory receptors CTLA-4 and PD-1 or its ligand PD-L1 have been shown to be beneficial for patients with melanoma, renal cell cancer, non-small cell lung cancer and a growing list of other cancers with impressive response rates. Here, we report a severe, potentially life-threatening side effect of anti-PD-1 immunotherapy with pembrolizumab, which has not been previously described in the literature. A 73-year-old woman with metastatic uveal melanoma treated with pembrolizumab in third line developed severe heart failure due to pembrolizumab-mediated autoimmune myocarditis. Echocardiographic studies revealed a severely impaired left ventricular function with dyssynchrony. All tests for cardiotropic viruses were negative and histological analysis of a myocardial biopsy showed lymphocytic infiltration with a predominance of CD8 positive cells and a reduction of FOXP3 positive regulatory T cells. After initiation of corticosteroids and guideline-conform heart failure therapy, the symptoms rapidly improved and the left ventricular function recovered. While autoimmune myocarditis is a documented side effect of other checkpoint inhibitors, as for example ipilimumab and in one case with anti-PD-L1 antibody, it is not described for anti-PD-1-antibodies like pembrolizumab or nivolumab. As the FDA recently approved both pembrolizumab and nivolumab for melanoma progressing after anti-CTLA-4 treatment with ipilimumab, more patients will soon receive anti-PD-1 therapy. Thus, it is important to be aware of such rare, but severe immune-related adverse events.

Trastuzumab emtansine (T-DM1) renders HER2+ breast cancer highly susceptible to CTLA-4/PD-1 blockade

An antibody-drug conjugate overcomes resistance to immune checkpoint blockade in HER2-positive breast cancer. Targeted therapy with more punch Overexpression of the human epidermal growth factor receptor 2 (HER2) is common in breast cancer, and it is associated with poor outcomes despite the availability of trastuzumab, an antibody against HER2, and other HER2-targeted agents. The reason for the poor outcomes is that many patients develop resistance to the targeted drugs. Müller et al. have now shown that this resistance can be overcome with trastuzumab emtansine, an antibody-drug conjugate that combines the HER2-targeting ability of trastuzumab with a cytotoxic drug, which the antibody delivers directly to the tumor. In addition to its cytotoxic effects, treatment with trastuzumab emtansine activated a strong antitumor immune response and effectively combined with immune checkpoint inhibitors, suggesting that it can be used in combination therapy. Targeted drug delivery with antibody-drug conjugates such as the HER2-directed ado-trastuzumab emtansine (T-DM1) has emerged as a powerful strategy for cancer therapy. We show that T-DM1 is particularly effective in eliciting antitumor immunity in patients with early breast cancer (WSG-ADAPT trial) and in a HER2-expressing orthotopic tumor model. In the latter, despite primary resistance to immunotherapy, combined treatment with T-DM1 and anti–CTLA-4/PD-1 (cytotoxic T lymphocyte–associated protein-4/programmed cell death protein-1) was curative because it triggered innate and adaptive immunity. Tumor rejection was accompanied by massive T cell infiltration, TH1 (T helper 1) cell polarization, and, notably, a substantial increase in regulatory T cells. Depletion of regulatory T cells resulted in inflammation and tissue damage, implying their essential role in protecting the host during therapy. This study provides insights into the mechanisms of T-DM1’s therapeutic activity and a rationale for potential therapeutic combination strategies with immunotherapy.

Induction chemoradiation in stage IIIA/N2 non-small-cell lung cancer: a phase 3 randomised trial

BACKGROUND One of the standard options in the treatment of stage IIIA/N2 non-small-cell lung cancer is neoadjuvant chemotherapy and surgery. We did a randomised trial to investigate whether the addition of neoadjuvant radiotherapy improves outcomes. METHODS We enrolled patients in 23 centres in Switzerland, Germany and Serbia. Eligible patients had pathologically proven, stage IIIA/N2 non-small-cell lung cancer and were randomly assigned to treatment groups in a 1:1 ratio. Those in the chemoradiotherapy group received three cycles of neoadjuvant chemotherapy (100 mg/m(2) cisplatin and 85 mg/m(2) docetaxel) followed by radiotherapy with 44 Gy in 22 fractions over 3 weeks, and those in the control group received neoadjuvant chemotherapy alone. All patients were scheduled to undergo surgery. Randomisation was stratified by centre, mediastinal bulk (less than 5 cm vs 5 cm or more), and weight loss (5% or more vs less than 5% in the previous 6 months). The primary endpoint was event-free survival. Analyses were done by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00030771. FINDINGS From 2001 to 2012, 232 patients were enrolled, of whom 117 were allocated to the chemoradiotherapy group and 115 to the chemotherapy group. Median event-free survival was similar in the two groups at 12·8 months (95% CI 9·7-22·9) in the chemoradiotherapy group and 11·6 months (8·4-15·2) in the chemotherapy group (p=0·67). Median overall survival was 37·1 months (95% CI 22·6-50·0) with radiotherapy, compared with 26·2 months (19·9-52·1) in the control group. Chemotherapy-related toxic effects were reported in most patients, but 91% of patients completed three cycles of chemotherapy. Radiotherapy-induced grade 3 dysphagia was seen in seven (7%) patients. Three patients died in the control group within 30 days after surgery. INTERPRETATION Radiotherapy did not add any benefit to induction chemotherapy followed by surgery. We suggest that one definitive local treatment modality combined with neoadjuvant chemotherapy is adequate to treat resectable stage IIIA/N2 non-small-cell lung cancer. FUNDING Swiss State Secretariat for Education, Research and Innovation (SERI), Swiss Cancer League, and Sanofi.