Evaluation of immune cell infiltrates and expression of cytokines/biological molecules in the microenvironment of tumours and tumour-draining axillary lymph nodes in patients with large and locally advanced breast cancers undergoing neoadjuvant chemotherapy: crucial contribution to immune-mediated tumour cell death

Background Neoadjuvant chemotherapy (NAC) is being used as first line treatment in women with large and locally advanced breast cancers (LLABCs). However, the response to NAC is difficult to predict. Growing evidence suggests that these patients are immunosuppressed and that circulating immunosuppressive regulatory cells and humoral factors affect the response to NAC. We explored the possible role of the in situ tumour immune milieu in inducing and affecting the responses to NAC, and the contribution of concomitant systemic circulating regulatory cells. Methods Paraffin-embedded breast cancers and ipsilateral axillary lymph nodes (ALNs) from pre- and post-NAC samples of a cohort of 33 women with LLABCs, 16 of whom had their blood regulatory cells previously investigated. Various immune cell infiltrations and expression of cytokines/ biological molecules in the specimens were studied using appropriate monoclonal antibodies and immunohistochemistry. Statistical analysis was carried out using non-parametric tests with SPSS version 21. Results High levels of pre-NAC tumour-infiltrating lymphocytes (TILs) (p<0.001) and subsets of CD4⁺T cells (intratumoural, p=0.023; peritumoural, p=0.001), CD8+T cells (intratumoural, p=0.008; peritumoural, p=0.002) and CD56⁺NK cells (intratumoural, p=0.001; peritumoural, p<0.001) were significantly associated with a pathological complete response (pCR). High levels of CD163⁺macrophages were also significantly associated with a good pathological response (p=0.004) and pCR (p=0.008). There was a positive correlation between the CD8:FOXP3 ratio and grade of pathological response. In multivariate analyses, TILs and peritumoural CD56+NK cells were found to be independent predictive factors for pCR. There was a significantly high expression of IL-10 in post-NAC breast specimens with poor responses to NAC (p