Potential impact of PD-L1 (SP-142) immunohistochemical heterogeneity in clear cell renal cell carcinoma immunotherapy
Introduction
Renal cell carcinoma is included in the top-ten list of the most common malignancies in Western countries [1]. Clear cell renal cell carcinoma (CCRCC) is the most frequent renal malignancy, accounting for roughly 70%–80% of the cases [2]. CCRCC is an aggressive neoplasm with different molecular profiles influencing treatment response [3]. Despite all therapeutic efforts, however, only radical surgery and early diagnosis have had a significant influence on survival [4].
CCRCC is a paradigmatic example of intratumor heterogeneity (ITH) typically displaying both temporal and spatial differences at the morphological, immunohistochemical and molecular levels [5]. Importantly ITH is the cornerstone of many therapeutic failures, and many efforts are being made to achieve a full characterization of tumors that may eventually allow better personalized approaches [6]. Immune checkpoint inhibitors, alone or in combination with anti-angiogenic drugs, have emerged in recent years as promising new therapeutic options for advanced CCRCC [7]. As a consequence, the influence of the cancer immune microenvironment is attracting great interest [8].
The expression of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), and programmed death-1 (PD-1) on activated T-cells inhibits the immune-mediated attack on tumor cells. Checkpoint inhibitors, in particular anti-CTLA-4 and anti-PD-1 (and its ligand anti-PD-L1), show great promise for renal cancer patients, however not all patients receive a benefit from these therapies, and as a consequence there is great interest in finding effective predictive biomarkers [9,10].
Currently patient selection for anti-PD-L1 treatments relies on the identification of PD-1/PD-L1 by routine immunohistochemical protocols, and several anti PD-1/PD-L1 clones have been developed for this purpose. However, up to 17% of patients that respond to PD-L1 therapy appear not to express PD-L1 when tested using current methodologies [9]. This apparent contradiction suggests that either factors other than PD-L1 are involved in the therapeutic action of anti-PD-L1 treatment, or more likely that current protocols are suboptimal for detection of PD-L1 expression [10].
Recent evidence has shown that routine protocols may be insufficient to reliably detect ITH in large tumors [11,12]. We have developed a multi-site tumor sampling (MSTS) protocol that out-performs routine sampling (RS) protocols in detecting histological ITH, and prognostic biomarkers [13]. MSTS follows the rationale the more you sample the more you find, and it is based in the divide-and-conquer algorithm [14], a successful strategy to solve complex problems in physics [15] that has been successfully applied also in biology [16] and in medicine [17]. Here, we have applied this strategy to analyze the expression of PD-L1 in the microenvironment of CCRCC tumors.
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Material and methods
The authors declare that all the analyses carried out in this study comply with current Spanish and European Union legal regulations. Samples from patients included in this study were obtained retrospectively from the archive of the Pathology Lab, Cruces University Hospital, Barakaldo, Spain. All patients gave written consent for the use of their samples in this study as approved by the Ethical and Scientific Committees of the Basque Health Service (Osakidetza) (CEIC-E PI2016096).
Twenty-two
Results
The main clinicopathological data of the patients included in this study are depicted in Table 1. Most cases were male (16 M/6 F), and the average age of patients was 60 years (range 15–82). Radical nephrectomy was carried out on 20 patients, and partial nephrectomy in two patients. The average tumor diameter was 8.5 cm with a range between 3.5 and 15 cm. Eight cases were low-grade (G1/2) and fourteen cases high-grade (G3/4). Pathological staging revealed an equal distribution of organ-confined
Discussion
RCC is a health problem of major concern in Western countries as well as a source of great interest to pathologists, with around 20 well-recognized clinical entities, and several emerging subtypes proposed in the last update of ISUP classification [20]. Traditionally, radio- and chemo-resistant CCRCC patients are treated with antiangiogenic drugs and checkpoint inhibitors, alone or in combination with radical surgery.
Drugs targeting the immune checkpoints (i.e., immunotherapy) represent a new
Compliance with ethical standards
The study has been approved by local ethical committee (CEIC-Euskadi PI2016096)
Funding
This work is supported by the grant SAF 2016-79847-R from Ministerio de Economía y Competitividad (MINECO), Spain.
Conflict of interest
The authors declare no conflict of interest
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