Infiltrates of M2-Like Tumour-Associated Macrophages Are Adverse Prognostic Factor in Patients with Human Papillomavirus-Negative but Not in Human Papillomavirus-Positive Oropharyngeal Squamous Cell Carcinoma.

INTRODUCTION

Human papillomavirus with a high oncogenic potential (HR-HPV) is responsible for more than a half of squamous cell carcinomas of the oropharynx. The HR-HPV-dependent cases of this tumour have a better prognosis compared to the HR-HPV-negative cases, despite the usually more advanced disease at the time of diagnosis. In addition to genetic and epigenetic factors, the causes of this more favourable course of the disease are also seen in the participation of the tumour microenvironment, including the patient's immune system. Macrophages are one of the most important elements of the immunocompetent cells landscape that make up the tumour microenvironment. Traditionally, they are divided into 2 groups: inflammatory macrophages with the M1 phenotype and tumour-associated macrophages known as M2 phenotype macrophages.

OBJECTIVE

The aim of this study was to investigate the impact of the macrophage infiltrates intensity of the M1/M2 and M2 phenotype separately on the clinical outcome of patients with squamous cell carcinoma of the oropharynx (OPSCC), taking into account the HR-HPV status of tumours.

METHODS

The study involved 85 patients with OPSCC in which HR-HPV status in tumour tissue was determined using a double-check algorithm including the detection of viral DNA by RT-PCR method with subsequent confirmation of its biological activity by immunohistochemical demonstrating the P16INK4A protein overexpression. In each of the groups formed on the basis of HR-HPV status, macrophages were discriminated using CD68 and CD163 proteins as markers of pan-macrophage and M2 phenotype. The intensity of infiltrates was quantified by means of computer-assisted analysis in digital images of whole slides (virtual slides) separately in tumour tissue and stroma.

RESULTS

In HPV-positive patients, significantly more intense infiltration of both M1/M2 and M2 macrophages was found in the tumour stroma compared to HPV-negative patients. The infiltrates from both types of macrophages in the tumour tissue were less intense and did not differ between these groups. Intensive infiltration of CD68+ macrophages in the tumour front was associated with higher rate of nodal failures and a shorter nodal control in both HR-HPV groups. In the group of HR-HPV-negative patients, heavy infiltration of CD163+ macrophages was associated with significantly shorter: loco-regional control (LRC), metastasis-free survival and overall survival (OS). These parameters and prognosis in patients with scanty CD163+ infiltration were similar to favourable outcomes in HR-HPV-positive patients. The relative risk of local-regional recurrence, distant metastases and disease-related death in HR-HPV-negative patients with intense CD163+ infiltrates was, respectively, 4.7, 5.4 and 5.7 compared to patients with scanty infiltrates.

CONCLUSIONS

Tumours with a positive HR-HPV status demonstrate intense infiltrations of total pool M1/M2 and M2 macrophages. In the group of HPV-negative patients, intensive M1/M2 macrophage infiltrates correlate with higher risk of nodal failures, and intensive M2 infiltrates are an adverse prognostic factor for LRC, metastasis-free survival and OS.