iRGD Tumor-Penetrating Peptide-Modified Nano-Delivery System Based on a Marine Sulfated Polysaccharide for Enhanced Anti-Tumor Efficiency Against Breast Cancer

Background: Breast cancer is a common malignancy in women. Conventional clinical therapies for breast cancer all display moderate clinical efficacies and limitations. It is urgent to explore the novel and combined therapeutic strategies for breast cancer to meet clinical demand. Methods: An iRGD tumor-penetrating peptide-modified nano-delivery system (denoted as iRGD-PSS@PBAE@JQ1/ORI nanopar-ticles) based on a marine sulfated polysaccharide was developed by codelivery of JQ1 (BET inhibitor) and oridonin (ORI, bioactive diterpenoid derived from traditional Chinese medicine herb). The iRGD-PSS@PBAE@JQ1/ORI NPs, surface modified with iRGD peptide conjugated propylene glycol alginate sodium sulfate (iRGD-PSS). The antitumor efficacy was evaluated both in vitro and in vivo. Results: The prepared iRGD-PSS@PBAE@JQ1/ORI NPs effectively enhanced the tumor targeting and cellular internalization of JQ1 and ORI. Thus, JQ1 exerted the reversal effect on immune tolerance by decreasing the expression of PD-L1, while ORI displayed multiple antitumor effects, such as antiproliferation, inhibition of intracellular ROS production and inhibition of lactic acid secretion. Conclusion: Our data revealed that iRGD peptide could significantly improve the cellular internalization and tumor penetration of the nano-delivery system. The combination of JQ1 and ORI could exert synergistic antitumor activities. Taken together, this study provides a multifunctional nanotherapeutic system to enhance the anti-tumor efficiency against breast cancer.