Tumor-infiltrating lymphocyte composition, organization and PD-1/ PD-L1 expression are linked in breast cancer

Abstract

The clinical relevance of tumor-infiltrating lymphocytes (TIL) in breast cancer (BC) has been clearly established by their demonstrated correlation with long-term positive outcomes. Nevertheless, the relationship between protective immunity, observed in some patients, and critical features of the infiltrate remains unresolved. This study examined TIL density, composition and organization together with PD-1 and PD-L1 expression in freshly collected and paraffin-embedded tissues from 125 patients with invasive primary BC. Tumor and normal breast tissues were analyzed using both flow cytometry and immunohistochemistry. TIL density distribution is a continuum with 25% of tumors identified as TIL-negative at a TIL density equivalent to normal breast tissues. TIL-positive tumors (75%) were equally divided into TIL-intermediate and TIL-high. Tumors had higher mean frequencies of CD4+ T cells and CD19+ B cells and a lower mean frequency of CD8+ T cells compare with normal tissues, increasing the CD4+/CD8+ T-cell ratio. Tertiary lymphoid structures (TLS), principally located in the peri-tumoral stroma, were detected in 60% of tumors and correlated with higher TIL infiltration. PD-1 and PD-L1 expression were also associated with higher TIL densities and TLS. TIL density, TLS and PD-L1 expression were correlated with more aggressive tumor characteristics, including higher proliferation and hormone receptor negativity. Our findings reveal an important relationship between PD-1/PD-L1 expression, increased CD4+ T and B-cell infiltration, TIL density and TLS, suggesting that evaluating not only the extent but also the nature and location of the immune infiltrate should be considered when evaluating antitumor immunity and the potential for benefit from immunotherapies.

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

“…However, fresh tissue is required and no information is provided on the distribution or organization of the immune infiltrate or relationship to other microenvironmental structures. Nevertheless, recent study of TILs in invasive breast carcinoma found a significant positive correlation between fresh tumor tissue analyzed by flow cytometry and IHC stained sections scored by a pathologist [26]. Messenger RNA (mRNA) profiling of tumor tissue can detect “immune gene signatures”, using the level of expression of immune related genes to describe the composition and functional status of the immune infiltrate [27].…”

Targeting immune checkpoints in breast cancer: an update of early results

“…111 123 Noteworthy, spontaneous antitumour immune infiltration was shown to be higher in primary tumours with respect to matched metastases (reviewed in Solinas et al 124 ), suggesting that administration of ICB in the early setting might be more effective than in the advanced setting. Novel immune strategies aiming at inducing (ie, vaccines, adoptive T cell therapy or ICB combinations including CT and RT) or boosting a pre-existing not-sufficient immune response 44 should be developed in BC to increase the benefit from ICB.…”

“…In BC, PD-L1 expression correlates with hormone receptor negativity, higher histological grade, proliferation and TIL infiltration. 44 As such, PD-1/PD-L1 have been evaluated as therapeutic targets in a variety of trials, of which results are discussed below.…”

CXCL13-producing TFH cells link immune suppression and adaptive memory in human breast cancer

“…+ tumor-infiltrating lymphocytes (TIL) in human BC specifically expressing CXCL13 (5,25), but curiously, the majority were CXCR5 -cells located both in TLS containing a GC (TLS/GC) and the tumor bed. CXCR5 -CXCL13 + CD4 + T cells have also been detected in rheumatoid synovitis from patients but were not viewed as T FH cells because of their CXCR5 negativity (26,27).…”