Abstract Inflammation is a natural immune response that can protect against cancer in early stages but, when becomes chronic, creates an immunosuppressive tumour microenvironment (TME) that promotes tumour progression. Recognized as a hallmark of cancer, chronic inflammation offers potential for new therapeutic strategies, particularly immunotherapy. However, some solid tumours, such as breast cancer, show partial resistance to these treatments. Cytokines are key regulators of inflammation, influencing cell communication and immune responses within the TME (1,2). Importantly, current clinical classification of BC often neglects the immune landscape, limiting the ability to predict responses to immunotherapy. Our hypothesis is that the cytokine profile of metastatic breast cancer possesses prognostic and predictive value and that cytokines can be potential biomarkers in breast cancer. Understanding how cytokine loops are coordinated within the breast TME could also lead to novel cytokine-based therapeutic strategies. Cytokine levels in serum and fresh tissue samples from metastatic BC patients (n=150) and in serum samples from metastatic cancer patients from other solid tumour types (n=186) were measured by Olink cytokine panel, which quantitatively assess 40 cytokines. Cytokine levels were correlated with clinical data, including overall and relapse free survival. The statistical analysis was done using different mathematical modelling methods. Our unpublished results show that the serum and tumour cytokine profiles do not correlate significantly, supporting the idea that some cytokines act locally in the TME. In addition, comparison with other metastatic tumour samples, led to the identification of some cytokines that are differentially expressed in BC. Integration of these data will shed light on the characterization of cytokine interactions in metastatic BC, helping to define its immune landscape. 1. Soler MF, Abaurrea A, Azcoaga P, Araujo AM, Caffarel MM. New perspectives in cancer immunotherapy: targeting IL-6 cytokine family. J Immunother Cancer. 2023;11(11):e007530; 2. Manzano S, Caffarel MM. Cytokine-centered strategies to boost cancer immunotherapy. Mol Oncol. 2025;19(3):579-583 Citation Format: M. M. CaffarelU. AlvarezP. AzcoagaA. RomoS. ManzanoP. PetitI. GarmendiaM. GarzónZ. TelletxeaM. OtañoA. UrruticoecheaI. Alvarez-Lopez. Characterization of the cytokine profile of metastatic Breast Cancer, from mediators of chronic inflammation to potential biomarkers abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-03-16.
Caffarel et al. (Tue,) studied this question.