Pathological Examination of Mouse Tissues by H&E and IHC Staining Following EV-Based Cancer Immunotherapy

Background: Cancer immunotherapy aims to harness and enhance the host immune response to target tumor cells. Extracellular vesicles (EVs), particularly those derived from macrophages, have recently gained attention for their immunomodulatory and antigen-presenting capacities. This study investigated the pathological and proliferative effects of macrophage-derived EV immunotherapy in a ۴T۱ breast cancer mouse model. Methods: BALB/c mice were subcutaneously injected with ۴T۱ breast cancer cells to establish tumors. Macrophage RAW ۲۶۴.۷ cells were stimulated with lipopolysaccharide (LPS) and loaded with ۴T۱ tumor lysates to generate EVs enriched with tumor antigens. Purified EVs were administered intradermally either prophylactically (prior to tumor challenge) or therapeutically (after tumor establishment). Tumor tissues were examined histologically using Hematoxylin and Eosin (H&E) staining, and proliferative activity was assessed via Ki-۶۷ immunohistochemistry. Tumor growth and survival were monitored throughout ۳۵ days. Results: Control mice exhibited extensive tumor infiltration, high mitotic indices, and multiple lung metastases. Prophylactically treated mice displayed markedly reduced tumor cellularity, fewer mitotic figures, and no detectable metastasis. Therapeutic treatment produced intermediate pathological improvements. Ki-۶۷ expression was significantly reduced from ۲۹% in controls to ۱۴% in prophylactically treated mice (p=۰.۰۰۱). Tumor volume analysis revealed substantial suppression in both treated groups, with near-complete inhibition in the prophylactic group (day ۳۵: ۰.۰۵۴۳ mm³ vs. ۲۴,۸۰۰ mm³ in controls, p=۰.۰۰۱). Survival analysis showed improved, though not statistically significant, longevity in the prophylactic group. Conclusion: Macrophage-derived EV immunotherapy effectively reduced tumor proliferation, inhibited metastasis, and suppressed tumor growth in ۴T۱ breast cancer-bearing mice. These findings highlight the therapeutic potential of EV-based immunomodulation as a promising approach for cancer treatment.

کلیدواژه ها:

Pathology ، Extracellular Vesicles ، Breast Cancer ، ۴T۱ Cell Line ، Immunotherapy