Tumor-infiltrating lymphocyte subsets and tertiary lymphoid structures in pulmonary metastases from colorectal cancer

Tertiary lymphoid structures in cancer - considerations for patient prognosis

Tertiary lymphoid structures (TLS) are ectopic lymphoid formations that form within nonlymphoid tissue. They share structural and functional characteristics with secondary lymphoid structures such as lymph nodes and can contain B-cell follicles and germinal centers surrounded by a T-cell region. TLS have been described in several types of cancers and are usually associated with positive patient outcomes. However, TLS differ vastly in cellular composition and location within tissue types. In this review, we discuss factors confounding the interpretation of the evidence for a prognostic role for TLS in cancer and frame these factors in the context of translation to regular clinical use.

Immunological potential of tertiary lymphoid structures surrounding the primary tumor in gastric cancer

Tertiary lymphoid structures (TLSs), which consist of B cells, T cells, follicular dendritic cells and high endothelial venules, have recently been found to be associated with effective antitumor immune responses in patients with cancer. Tumor-infiltrating T cells and B cells have each been demonstrated to be associated with survival in patients with cancer. We hypothesized that TLSs, an assembly of immune cells, may be important for the initiation and/or maintenance of T cell and B cell responses against tumors. The aim of the present study was to examine the cellular mechanism of B cells in TLSs within gastric cancer and to understand the antitumor immune response of TLSs. Each B cell subset in a tumor was examined using flow cytometry to evaluate B cell differentiation and the functional status of B cells. In addition, B cell clonality was investigated by analyzing the B cell antigen receptor gene using PCR, and the function and formation/maintenance of TLSs were evaluated using reverse transcription-quantitative PCR. Tumor-infiltrating B cells were more differentiated compared with that in distant non-tumor tissues and tumor-draining lymph nodes. The PCR results revealed specific BCR gene expression in tumor-infiltrating B cells. The expression of co-stimulatory factors, CD80 and CD86, was observed, in addition to the constantly expressed major histocompatibility complex molecules (HLA-ABC and HLA-DR). CD70 was expressed in addition to CD27 in both CD20⁺ B cells and CD8⁺ T cells, indicating that these factors are activated together through their interaction. The mRNA expression levels of CCL21, CXCL13, PD-L1, perforin and granzyme B in TLSs was significantly higher compared with that in non-TLSs. The majority of tumor-infiltrating B cells in gastric cancer exist in the form of TLSs around the tumor and have been antigen-sensitized and differentiated, and proliferated in TLSs but not in the lymph nodes. In addition, B cells in TLSs might primarily function as antigen-presenting cells and be associated with the induction of cytotoxic T cells.

The local inflammatory response in colorectal cancer - Type, location or density? A systematic review and meta-analysis

INTRODUCTION

The host anti-tumour inflammatory response is a strong prognostic indicator, and tumour infiltrating lymphocytes (TILs) are believed to have a complimentary role alongside TNM assessment in dictating future management. However, there is wide disagreement regarding the most efficacious and cost-effective method of assessment.

METHODS

A comprehensive literature search was performed of EMBASE, MedLine and PubMed as well as an assessment of references to identify all relevant studies relating to the assessment of the peri-tumoural inflammatory response or TILs and prognosis in colorectal cancer (CRC). A meta-analysis was performed of 67 studies meeting the REMARK criteria using RevMan software.

RESULTS

Intratumoural assessment of both CD3 and CD8 in CRC were significant for disease-free survival (DFS) (combined HRs 0.46; 95%CI: 0.39-0.54 and 0.54; 95%CI: 0.45-0.65), as well as overall survival (OS) and disease-specific survival (DSS). The same was true for assessment of CD3 and CD8 at the invasive margin (DFS: combined HRs 0.45; 95%CI: 0.33-0.61 and 0.51; 95%CI: 0.41-0.62). However, similar fixed effects summaries were also observed for H&E-based methods, like Klintrup-Makinen grade (DFS: HR 0.62; 95%CI: 0.43-0.88). Furthermore, inflammatory assessments were independent of MSI status.

CONCLUSION

The evidence suggests that it is the density of a co-ordinated local inflammatory infiltrate that confers survival benefit, rather than any individual immune cell subtype. Furthermore, the location of individual cells within the tumour microenvironment does not appear to influence survival. The authors advocate a standardised assessment of the local inflammatory response, but caution against emphasizing the importance of any individual immune cell subtype.

Tumor-infiltrating lymphocytes in primary tumors of colorectal cancer and their metastases

The presence of tumor cells in the large intestine stimulates hypoxia and local inflammatory mediators that activate numerous inflammatory cells, including a diverse lymphoid tumor cell population. The aim of the present study was to evaluate tumor-infiltrating lymphocytes (TILs) located in the invasive primary tumor, surrounding deposits of tumor cells and those present in distal metastatic cells in the liver of patients with colorectal cancer. Furthermore, the correlation of TILs with anatomical parameters was assessed. The study group included 123 patients with primary tumor colorectal cancer without distant metastasis, 25 cases with deposits of colorectal cancer cells and 15 cases of colorectal cancer liver metastasis. TILs were assessed in tissues stained with hematoxylin-eosin using light microscopy and evaluated by two independent pathologists blinded to the clinical information. Infiltration of TILs in the invasive front of primary tumor was stronger compared with those surrounding deposits of cancer cells and liver metastases (P<0.001). TILs in the invasive front of primary tumor masses were associated with various variables linked with tumor progression and inflammatory cell infiltrate. TILs distributed around the deposits of cancer cells were associated with postoperative treatment; however, those localized in the invasive front of liver metastases were correlated with preoperative therapy. In conclusion, TILs assessment in primary tumors of colorectal cancer, surrounding deposits of tumor cells and in the metastatic cells in the liver may be helpful in understanding the role of these cells in the organization of immune response.

The prognostic significance of peritumoral tertiary lymphoid structures in breast cancer

Tumors and their surrounding area represent spatially organized "ecosystems", where tumor cells and the immune contextures of the different compartments are in a dynamic interplay, with potential clinical impact. Here, we aimed to investigate the prognostic significance of peritumoral tertiary lymphoid structures (TLS) either alone or jointly with the intratumoral densities and spatial distribution of CD8 + and CD163 + cells in breast cancer (BCa) patients. TLS were identified peritumorally, within the area distancing up to 5 mm from the infiltrative tumor border, counted and further characterized as adjacent or distal, in formalin-fixed, paraffin-embedded tumor tissue samples from a cohort of 167 patients, with histologically confirmed invasive ductal BCa. TLS and tumor-infiltrating immune cells were determined by H&E and immunohistochemistry. Clinical follow-up was available for 112 of these patients. Patients with peritumoral TLS exhibited worse disease-free survival (DFS) and overall survival (OS) as compared to patients lacking TLS. Moreover, the density of peritumoral TLS was found to be crucial for prognosis, since patients with abundant TLS exhibited the worst DFS and OS. By combining the density of adjacent TLS (aTLS) with our recently published intratumoral signatures based on the differential distribution of CD8 + and CD163 + in the tumor center and invasive margin, we created two improved immune signatures with superior prognostic strength and higher patient population coverage. Our observations strengthen the notion for the fundamental role of the dynamic interplay between the immune cells within the tumor microenvironment (center/invasive margin) and the tumor surrounding area (peritumoral TLS) on the clinical outcome of BCa patients.

The Crohn's-Like Lymphoid Reaction to Colorectal Cancer-Tertiary Lymphoid Structures With Immunologic and Potentially Therapeutic Relevance in Colorectal Cancer

The Crohn's-like lymphoid reaction (CLR) to colorectal cancer (CRC), a CRC-specific ectopic lymphoid reaction, is thought to play an important role in the host response to CRC. CLR is characterized by peritumoral lymphocytic aggregates that are found at the advancing edge of the tumor. Spatial and molecular characterization of CLR within the tumor microenvironment (TME) have uncovered a spectrum of peritumoral lymphoid aggregates with varying levels of organization and maturation. In early stages of CLR development, CD4+ T-cells cluster predominantly with mature antigen presenting dendritic cells. As CLR matures, increasing numbers of B-cells, as well as follicular dendritic cells are recruited to create lymphoid follicles. When highly organized, CLR resembles functional tertiary lymphoid structures (TLS), allowing for lymphocyte recruitment to the TME and promoting a tumor-specific adaptive immune response. CLR has been consistently associated with favorable prognostic factors and improved survival among CRC patients, often providing more prognostic information than current clinical staging systems. However, consensus is lacking regarding CLR scoring and it is not clinically assessed or reported. Differences between CLR and other cancer-associated lymphoid structures exist both in primary and metastatic disease, underscoring the need to characterize organ-specific TLS. Further research is needed to explore the role of CLR in predicting response to immunotherapy and to leverage CLR to promote immunotherapeutic strategies in CRC.

Tertiary lymphoid structures in the era of cancer immunotherapy

Tertiary lymphoid structures (TLSs) are ectopic lymphoid organs that develop in non-lymphoid tissues at sites of chronic inflammation including tumours. Key common characteristics between secondary lymphoid organogenesis and TLS neogenesis have been identified. TLSs exist under different maturation states in tumours, culminating in germinal centre formation. The mechanisms that underlie the role of TLSs in the adaptive antitumour immune response are being deciphered. The description of the correlation between TLS presence and clinical benefit in patients with cancer, suggesting that TLSs could be a prognostic and predictive factor, has drawn strong interest into investigating the role of TLSs in tumours. A current major challenge is to exploit TLSs to promote lymphocyte infiltration, activation by tumour antigens and differentiation to increase the antitumour immune response. Several approaches are being developed using chemokines, cytokines, antibodies, antigen-presenting cells or synthetic scaffolds to induce TLS formation. Strategies aiming to induce TLS neogenesis in immune-low tumours and in immune-high tumours, in this case, in combination with therapeutic agents dampening the inflammatory environment and/or with immune checkpoint inhibitors, represent promising avenues for cancer treatment.

Harnessing the innate immune system and local immunological microenvironment to treat colorectal cancer

Significant progress in the development of new immunotherapies has led to successful clinical trials for malignant melanoma and non-small cell lung cancer; however, for the majority of solid tumours of the gastrointestinal tract, little or no progress has been seen. The efficacy of immunotherapies is limited by the complexities of a diverse set of immune cells, and interactions between the tumour cells and all other cells in the local microenvironment of solid tumours. A large fraction of immune cells present in and around solid tumours derive from the innate arm of the immune system and using these cells against tumours offers an alternative immunotherapeutic option, especially as current strategies largely harness the adaptive arm of the immune system. This option is currently being investigated and attempts at using the innate immune system for gastrointestinal cancers are showing initial results. Several important factors, including cytokines, chemotherapeutics and the microbiome, influence the plasticity and functionality of innate (myeloid) cells in the microenvironment, and this complexity of regulation has limited translation into successful trials so far. In this review, current concepts of the immunobiology of the innate arm in the tumour microenvironment are presented in the context of clinical translation.

Dissimilar patterns of tumor-infiltrating immune cells at the invasive tumor front and tumor center are associated with response to neoadjuvant chemotherapy in primary breast cancer

BACKGROUND

Tumor-infiltrating lymphocytes (TILs) are described as an important immune modulator in the tumor microenvironment and are associated with breast cancer (BC) outcome. The spatial analysis of TILs and TIL subtype distribution at the invasive tumor front (ITF) and the tumor center (TC) might provide further insights into tumor progression.

METHODS

We analyzed core biopsies from 87 pre-therapeutic BC patients for total TILs and the following subtypes: CD3+, CD4+, CD8+, CD20+ and CD68+ cells in correlation to clinicopathological parameters and disseminated tumor cells (DTCs) in the bone marrow.

RESULTS

TILs and TIL subtypes showed significantly different spatial distribution among both tumor areas. TILs, especially CD3+ T cells were associated with the tumor status and tumor grading. BC patients responding to neoadjuvant chemotherapy had significantly more TILs and CD3+ T cells at the TC. The presence of DTCs after NACT was related to CD4+ infiltration at the TC.

CONCLUSION

The dissimilar spatial association of TILs and TIL subtypes with clinicopathological parameters, NACT response and minimal residual disease underlines the necessity of detailed TIL analysis for a better understanding of immune modulatory processes.

Presence of tertiary lymphoid structures determines the level of tumor-infiltrating lymphocytes in primary breast cancer and metastasis

The level of tumor-infiltrating lymphocytes and presence of tertiary lymphoid structures are significant prognostic and predictive factors in primary breast cancer. However, the understanding about differences in tumor-infiltrating lymphocytes and tertiary lymphoid structures at various metastatic sites or between primary breast tumors and metastatic sites is limited. A total of 335 cases of metastatic breast cancer from four metastatic sites (lung, liver, brain, and ovary) were included. We analyzed the percentages of tumor-infiltrating lymphocytes and presence of tertiary lymphoid structures in the primary and metastatic sites. The mean level of tumor-infiltrating lymphocytes in the lung metastases was higher than in the liver, brain, ovary, and matched primary tumors, while metastatic tumors of the liver and brain showed lower levels of tumor-infiltrating lymphocytes than primary tumors. Tertiary lymphoid structures were only found in the lung and liver, and in cases of brain metastases the change of tertiary lymphoid structures from present to absent significantly affected the level of tumor-infiltrating lymphocytes in metastases compared with that in matched primary tumors. Patients with a lower histological grade, hormone receptor positivity in primary tumors and metastases, a lower level of tumor-infiltrating lymphocytes and absence of tertiary lymphoid structures in primary tumors, a higher level of tumor-infiltrating lymphocytes and presence of tertiary lymphoid structures in metastases, and lung metastases showed significantly better overall survival. Our results showed that metastatic breast tumors in the lung had more tumor-infiltrating lymphocytes than did tumors at other sites and matched primary tumors. In addition, the presence of tertiary lymphoid structures in metastatic sites is a critical factor for the level of tumor-infiltrating lymphocytes.

The correlation and prognostic value of serum levels of soluble programmed death protein 1 (sPD-1) and soluble programmed death-ligand 1 (sPD-L1) in patients with hepatocellular carcinoma

Background

Blocking the programmed death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) pathway in hepatocellular carcinoma (HCC) is a very promising approach in immunotherapy. However, the correlation and prognostic values of serum soluble PD-1 and PD-L1 (sPD-1/sPD-L1) have not been explored conjointly in HCC patients.

Methods

This study retrospectively included 120 HCC patients receiving radical resection. The serum levels of sPD-1/sPD-L1 and inflammatory cytokines were measured by antibody array assay. Immunohistochemistry was applied to assess both the expression of membrane-bound PD-L1, and the number of CD4⁺ tumor-infiltrating lymphocytes (TILs) and CD8⁺ TILs.

Results

The best cut-off values of sPD-1 and sPD-L1 for predicting disease-free survival (DFS) were 33.0 µg/ml and 11.2 µg/ml, respectively. Multivariable analysis showed that sPD-L1 was a negative independent prognostic factor [DFS, Hazard Ratio (HR) 2.58, 95% CI 1.14–5.84, P = 0.023; overall survival (OS), HR 1.77, 95% CI 1.01–3.12, P = 0.048], while sPD-1 was a favorable independent prognostic factor (DFS, HR 0.32, 95% CI 0.14–0.74, P = 0.007; OS, HR 0.54, 95% CI 0.30–0.98, P = 0.044) in HCC patients. We also observed some similar associations between inflammatory cytokines (IL-10, IL-17, TNF-α) and sPD-1 or sPD-L1, as well as a close positive association between sPD-1 and sPD-L1. No significant associations of sPD-1/sPD-L1 with either intra-tumoral PD-L1 expression, or the numbers of CD4⁺ TILs and CD8⁺ TILs were determined.

Conclusions

Our findings indicate that sPD-1 and sPD-L1 are independent prognostic factors with opposite prognostic roles in predicting both DFS and OS in HCC patients.

Electronic supplementary material

The online version of this article (10.1007/s00262-018-2271-4) contains supplementary material, which is available to authorized users.

Stromal and intraepithelial tumor-infiltrating lymphocytes in colorectal carcinoma

The local mechanisms of antitumor immune defense determine the development and organization of the tumor microenvironment, and the composition and relative proportions of the inflammatory cell population affect the quality and characteristics of the immune response. The aim of the present study was to conduct a quantitative morphological evaluation of two types of tumor-infiltrating lymphocyte (TILs) populations, including those located in the stroma and intraepithelial cancer structures, in the invasive front and the center of the tumor in patients with colorectal cancer (CRC). The study included 160 patients with CRC who had undergone surgery. The tissue material was stained with hematoxylin and eosin, as used in routine histopathological diagnosis, and the two TIL populations were observed and counted with light microscopy. The relative extent of infiltration of stromal and intraepithelial TILs into the front and center of the primary tumors was similar. The extent of infiltration by stromal TILs was negatively correlated with the morphological features of tumor progression including the cancer infiltration of blood vessels (P=0.016), the invasion of lymph vessels (P=0.007), perineural invasion (P=0.036), lymph node involvement (P=0.047) and distant metastases (P=0.032). The infiltration by intraepithelial TILs was positively correlated with a desmoplastic reaction (P=0.002). Disease-free survival time was statistically shorter in patients without intraepithelial TILs in the center of the primary tumor mass (P=0.049; hazard ratio = 1.45). These results confirm that the infiltration of TILs into the invasive front and center of the tumor in patients with CRC serves an important role in the invasion and progression of the disease, and should be considered in routine histopathological examinations.

Pulmonary metastasectomy for colorectal cancer: analysis of prognostic factors affecting survival

Background

Pulmonary metastasectomy is considered a standard procedure in the treatment of metastatic colorectal cancer (CRC). Different prognostic factors including multiple metastatic nodules, the presence of extra-pulmonary metastases and BRAF mutation status have been associated with poor survival. The aim of this study was to evaluate which factors influenced survival in CRC patients undergoing pulmonary metastasectomy by studying primary tumors and pulmonary metastases.

Methods

All patients treated for primary CRC who presented pulmonary metastases in a 10-year period were considered (group A). A control group treated for primary CRC who did not develop any pulmonary or extra-pulmonary metastases was taken for comparison (group B). Different prognostic factors including gender, age, tumor location, histological type, inflammatory infiltrate, BRAF, CDX2 and extra-pulmonary metastases were analyzed. Overall survival (OS) and patients' survival after pulmonary metastasectomy were also considered.

Results

Fifty-four patients were evaluated in group A and twenty-three in group B. In group A, BRAF immunohistochemistry did not significantly differ between primary tumors and pulmonary metastases; no difference of BRAF expression was found between group A and B. Even the expression of CDX2 was not significantly different in primary tumors and metastases. Similarly, in group B CDX2 did not significantly differ from primary CRC of group A. The most significant prognostic factor was the presence of extra-pulmonary metastases. Patients with extra-pulmonary metastases experienced a significant shorter survival compared to patients with pulmonary metastases alone (P=0.001 with log-rank test vs. P=0.003 with univariate Cox regression). Interestingly, patients with right pulmonary metastases presented a significant longer survival than those with left pulmonary metastases (P=0.027 with log-rank test vs. 0.04 with univariate Cox regression).

Conclusions

The main prognostic factor associated with poor survival after lung resection of CRC metastases is a history of extra-pulmonary metastases. BRAF and CDX2 did not have a significant role in this small series of patients.

Assessing Tumor-infiltrating Lymphocytes in Solid Tumors: A Practical Review for Pathologists and Proposal for a Standardized Method From the International Immunooncology Biomarkers Working Group: Part 1: Assessing the Host Immune Response, TILs in Invasive Breast Carcinoma and Ductal Carcinoma In Situ, Metastatic Tumor Deposits and Areas for Further Research

Assessment of tumor-infiltrating lymphocytes (TILs) in histopathologic specimens can provide important prognostic information in diverse solid tumor types, and may also be of value in predicting response to treatments. However, implementation as a routine clinical biomarker has not yet been achieved. As successful use of immune checkpoint inhibitors and other forms of immunotherapy become a clinical reality, the need for widely applicable, accessible, and reliable immunooncology biomarkers is clear. In part 1 of this review we briefly discuss the host immune response to tumors and different approaches to TIL assessment. We propose a standardized methodology to assess TILs in solid tumors on hematoxylin and eosin sections, in both primary and metastatic settings, based on the International Immuno-Oncology Biomarker Working Group guidelines for TIL assessment in invasive breast carcinoma. A review of the literature regarding the value of TIL assessment in different solid tumor types follows in part 2. The method we propose is reproducible, affordable, easily applied, and has demonstrated prognostic and predictive significance in invasive breast carcinoma. This standardized methodology may be used as a reference against which other methods are compared, and should be evaluated for clinical validity and utility. Standardization of TIL assessment will help to improve consistency and reproducibility in this field, enrich both the quality and quantity of comparable evidence, and help to thoroughly evaluate the utility of TILs assessment in this era of immunotherapy.

PD1-positive tumor-infiltrating lymphocytes are associated with poor clinical outcome after pulmonary metastasectomy for colorectal cancer

Pulmonary metastasectomy (PM) is routinely performed in colorectal cancer (CRC) patients with oligometastatic spreading to the lungs. Patients with an aggressive tumor phenotype should be excluded from PM, since its benefit is outweighed by early tumor recurrence and impaired prognosis. Expression of PD-1 and its ligands are prognostic factors in a variety of primary tumors. However, their impact on patients' outcome in the setting of PM for CRC has not been evaluated before. 53 CRC patients with pulmonary metastases receiving PM with curative intent were included in this study. Tissue samples of resected pulmonary metastases and available corresponding primary tumors were collected and assessed for PD-1, PD-L1 and PD-L2 expression by tumor-infiltrating lymphocytes (TILs) and tumor cells. Expression patterns were correlated with clinical outcome parameters. PD-1 and PD-L1 expression was commonly found in TILs and tumor cells. Expression levels significantly differed between metastases and primary tumors. High PD-1 expression by TILs was associated with impaired overall survival (low vs high expression (mean, 95% CI): 78 mo (60-96) vs 35 mo (25-44); p = 0.011). Additionally, the subgroup of patients, who experienced an upgrading in their TILs/PD1 status between primary and metastasis had a worse survival outcome compared with patients with the same grade or a downgrading (34 mo (26-42) vs 96 mo (72-120); p = 0.004). Thus, PD-1 expression by TILs is a strong prognostic marker in CRC patients with pulmonary spreading treated by PM. Moreover, this study provides a rationale for a therapeutic PD-1 pathway blockade in the treatment of CRC lung metastases. Future, large-scale studies are warranted to validate the findings of this single-center, retrospective analysis.

Impact of cyclooxygenase-2 and prostaglandin-E2 expression on clinical outcome after pulmonary metastasectomy

BACKGROUND

Pulmonary metastasectomy (PM) is a standard procedure in the treatment of stage IV colorectal cancer (CRC). In most centers the indication for PM is solely based on clinical factors without taking the tumor biology into account. This results in diverse outcomes ranging from long-term remission to early recurrence. Inflammation is considered a hallmark of cancer development and progression. On the other hand the accessibility of CRC cells to the immune system reflects the grade of tumor aggressiveness. We sought to investigate the impact of cyclooxygenase-2 (COX-2) and prostaglandin-E2 (PGE2) expression in pulmonary metastases on different outcome parameters following PM.

METHODS

From 04/2009 to 11/2013 53 patients with complete PM for CRC were included in this single-center study. Tissue samples of resected pulmonary metastases and available corresponding primaries were collected and assessed by immunohistochemistry for COX-2 and PGE2 expression of the tumor tissue and the peritumoral stroma. Results were correlated with clinical outcome parameters.

RESULTS

COX-2 and PGE2 were detected in nearly every pulmonary CRC metastasis. Staining intensities of pulmonary metastases correlated only weakly with intensities found in primary tumors. When dividing metastases in high expressing and low expressing tumors, a trend towards longer recurrence free survival and improved survival was found in tumors with strong COX-2 and PGE2 staining.

CONCLUSIONS

In conclusion, this pilot study shows that COX-2 and PGE2 are uniformly overexpressed in pulmonary metastases from CRC. High expression of COX-2 and PGE2 seems to reflect a beneficial tumor biology with late tumor recurrence and prolonged overall survival after PM.

The proportion of circulating CD45RO+CD8+ memory T cells is correlated with clinical response in melanoma patients treated with ipilimumab

BACKGROUND

Immune checkpoint blockade (ICB) has been a breakthrough in the treatment of metastatic melanoma. But with only about 20-40% long-term responders and severe side-effects in about 12-17%, finding predictive markers for treatment response is of great interest.

METHODS

We prospectively assessed clinical data, haematologic parameters and freshly isolated peripheral blood mononuclear cells of 30 patients treated with ipilimumab (n = 21) and pembrolizumab (n = 9) prior to the first 4 cycles with ICB and before the first tumour assessment.

RESULTS

We discovered that the baseline levels of CD45RO⁺CD8⁺ T cells significantly differed among the patients. Thirteen (43%) of our patients had normal baseline levels of CD45RO⁺CD8⁺ T cells, whereas 17 (57%) patients were low on CD45RO⁺CD8⁺ T cells. The baseline levels of CD45RO⁺CD8⁺ T cells correlated significantly with the response to ipilimumab but not pembrolizumab. Patients with baseline levels of lower/equal 25% of CD45RO⁺CD8⁺ T cells did not respond to treatment with ipilimumab. Phenotyping the CD8⁺ T cells in patients treated with ipilimumab revealed an activated HLA-DR⁺CD25^- phenotype, implying antigen non-specific stimulation. The levels of the HLA-DR⁺CD25^-CD8⁺ T cells were significantly higher in patients with a normal baseline of CD45RO⁺CD8⁺ T cells and even increased significantly during treatment. Furthermore, proliferation of melanoma antigen recognized by T cells 1 (MART-1)-specific CD8⁺ T cells was not observed. Patients with normal baseline levels of CD45RO⁺CD8⁺ T cells showed a significant longer overall survival when treated with ipilimumab but not pembrolizumab.

CONCLUSION

Patients with normal baseline levels of CD45RO⁺CD8⁺ T cells respond significantly more frequently to treatment with ipilimumab and the CD8⁺ T cells appear to be antigen non-specifically activated. The baseline level of CD45RO⁺CD8⁺ T cells represents a promising factor as biomarker for the prediction of the response to ipilimumab.