The effect of Tocilizumab on molecular mechanisms in a breast cancer model

Breast cancer remains one of the most common and aggressive malignancies worldwide, with triple-negative breast cancer (TNBC) representing a subtype marked by poor prognosis and limited treatment options. In this study, a murine 4T1 TNBC model in BALB/c mice was established to evaluate the therapeutic potential of Tocilizumab, an interleukin-6 receptor (IL-6R) inhibitor, and Cisplatin, a conventional chemotherapeutic, administered individually or in combination. Five groups were formed, including negative and tumor controls, and treatment cohorts receiving Tocilizumab, Cisplatin, or combination therapy. Tumor progression was monitored by serial caliper measurements, while systemic health was assessed via body weight tracking. After treatment, primary tumors were collected for histopathological, immunohistochemical, ELISA, and qPCR analyses. The findings demonstrated that Tocilizumab and Cisplatin exert complementary yet mechanistically distinct effects. Tocilizumab inhibited the IL-6 signaling pathway, leading to reduced STAT3 activation and a marked decrease in PCNA expression, thereby exerting a pronounced antiproliferative effect. The combination therapy resulted in a significant reduction in tumor volume, diminished metastatic activity, and synergistic modulation of PCNA expression. These molecular outcomes were consistent with the histopathological observations and survival data. This study provides new insight into the impact of IL-6 blockade in TNBC progression and demonstrates the enhanced therapeutic efficacy of Tocilizumab with Cisplatin. By integrating tumor biology, molecular pathways, and treatment outcomes, the work highlights the importance of targeting the IL-6/STAT3 axis in TNBC and supports further translational research toward innovative combinational strategies in breast cancer therapy. Key Words: Combination Therapy, IL-6/STAT3 Signaling Pathway, Cisplatin, Tocilizumab, Triple-Negative Breast Cancer (TNBC)