Abstract
BackgroundFulfilling the promise of cancer immunotherapy requires novel predictive biomarkers to characterise the host immune microenvironment. Deciphering the complexity of immune cell interactions requires an automated multiplex approach to histological analysis of tumour sections. We tested a new automatic approach to select tissue and quantify the frequencies of cell-cell spatial interactions occurring in the PD1/PD-L1 pathway, hypothesised to reflect immune escape in oropharyngeal squamous cell carcinoma (OPSCC).MethodsSingle sections of diagnostic biopsies from 72 OPSCC patients were stained using multiplex immunofluorescence (CD8, PD1, PD-L1, CD68). Following multispectral scanning and automated regions-of-interest selection, the Hypothesised Interaction Distribution (HID) method quantified spatial proximity between cells. Method applicability was tested by investigating the prognostic significance of co-localised cells (within 30 μm) in patients stratified by HPV status.ResultsHigh frequencies of proximal CD8+ and PD-L1+ (HR 2.95, p = 0.025) and PD1+ and PD-L1+ (HR 2.64, p = 0.042) cells were prognostic for poor overall survival in patients with HPV negative OPSCC (n = 31).ConclusionThe HID method can quantify spatial interactions considered to reflect immune escape and generate prognostic information in OPSCC. The new automated approach is ready to test in additional cohorts and its applicability should be explored in research and clinical studies.
Highlights
It is recognised that a plethora of immune regulatory factors in the tumour microenvironment (TME) contribute to the progression of cancers and limit their response to treatment.[1,2,3] An important class of inhibitory factors, designated immune checkpoints, have been associated with sustained tumour responses in a variety of cancers.[4,5] The programmed cell death 1 (PD-1) receptor has emerged as a dominant negative regulator of anti-tumour effector function
This state of local immune privilege can be reversed by blocking antibodies to PD-1 or PD-L1 and such single agent therapies are licensed for the treatment of patients with multiple types of cancers.[4,5,6,7,8,9,10]
124 patients with concordant HPV status for all three assays had sufficient formalin fixed, paraffin embedded tissue available for multiplex immunofluorescence staining with antibodies against PD-L1, CD8, CD68 and PD-1.15 Analyses were performed on randomly selected regions of interest (ROIs) from sections taken from pre-treatment diagnostic biopsies of oropharyngeal squamous cell carcinoma (OPSCC)
Summary
It is recognised that a plethora of immune regulatory factors in the tumour microenvironment (TME) contribute to the progression of cancers and limit their response to treatment.[1,2,3] An important class of inhibitory factors, designated immune checkpoints, have been associated with sustained tumour responses in a variety of cancers.[4,5] The programmed cell death 1 (PD-1) receptor has emerged as a dominant negative regulator of anti-tumour effector function. IFN-γ+ release leads to upregulation of PD-L1 on the local tumour and other cells, which in turn can compromise T cell function through adaptive immune resistance This state of local immune privilege can be reversed by blocking antibodies to PD-1 or PD-L1 and such single agent therapies are licensed for the treatment of patients with multiple types of cancers.[4,5,6,7,8,9,10] Response rates can be as high as 90% for some tumour types but as low as 15% with others, but selection of patients likely to respond favourably to such single agent therapy proves a challenge, as it requires an in depth understanding of immune interactions in the TME.[4,5]. The new automated approach is ready to test in additional cohorts and its applicability should be explored in research and clinical studies
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