Sanambar Sadighi - Department of Medical Oncology, Cancer Research Center, Cancer Institute of Iran, Tehran University of Medical Sciences, Tehran, Iran
Ramezanali Sharifian - Department of Hematology and Oncology, Vali-e-Asr Hospital, Tehran University of Medical Sciences, Tehran, Iran
Monireh Kazemimanesh - Department of Molecular Virology, Pasteur Institute of Iran, Tehran, Iran and Université Toulouse III Paul Sabatier, INSERM U۱۰۳۷, Cancer Research Centre of Toulouse (CRCT), Toulouse, France
Ahad Muhammadnejad - Cancer Biology Research Center, Cancer Institute of Iran, Tehran University of Medical Sciences
Zahra Shohosseini - Department of Medical Biotechnology, School of Allied Medical Sciences, Iran University of Medical Sciences, Tehran, Iran
Saeid Amanpour - Cancer Biology Research Center, Cancer Institute of Iran, Tehran University of Medical Sciences
Samad Muhammadnejad - Gene Therapy Research Center, Digestive Diseases Research Institute, Tehran University of Medical Sciences, Tehran, Iran

Objective(s): Immune checkpoint expression on tumor-infiltrating lymphocytes (TILs) has a correlation with the outcome of neoadjuvant chemotherapy (NAC) in breast cancer. However, the reciprocal effect of these regimens on the quality and quantity of immune checkpoints has hitherto not been addressed. We aimed to evaluate the impact of three NAC regimens on TILs and immune checkpoints in a murine triple-negative breast cancer model.Materials and Methods: Syngeneic model of locally-advanced breast cancer was established in immunocompetent mice using a ۴T۱ cell line. Tumor-bearing animals were treated with human-equivalent dosages of doxorubicin, paclitaxel, paclitaxel and carboplatin combination, and placebo. Infiltration of CD۳+, CD۸+, and FoxP۳+ cells into the tumor was assessed by immunohistochemistry. Expression of immune checkpoints, including PD-۱, CTLA-۴, and TIM-۳, was evaluated by real-time PCR.Results: Doxorubicin led to a significant (p <۰.۰۱) increase in the percentage of the stromal infiltrating CD۳+ and CD۸+ lymphocytes. Doxorubicin also suppressed significantly (p <۰.۰۵) the relative expression of PD-۱ compared with the placebo. PD-۱ expression was significantly (p <۰.۰۵) lower in the group treated with paclitaxel and carboplatin combination as compared with the placebo. The relative expression of TIM-۳ was significantly (p <۰.۰۵) suppressed in doxorubicin-treated mice in comparison with other interventions.Conclusion: Our findings hypothesize that NAC with doxorubicin may potentiate antitumor immunity not merely by recruitment of TILs, but via down-regulation of PD-۱ and TIM-۳ checkpoints. Carboplatin-containing NAC may suppress PD-۱ as well.

Animal model Breast neoplasms Immune checkpoints Neoadjuvant chemotherapy Tumor, infiltrating, Lymphocytes