Sequential Drug Release to Modulate Collagen Synthesis and Promote Micelle Penetration in Tumors

Cancer chemotherapy is confronted with insufficient drug penetration in tumors. "Solid tumor priming" is proposed to modulate the abnormal tumor microenvironment but suffers from limited digestion efficiency and underlying tumor metastasis. Losartan (Los) and telmisartan (Tel) are well-known antihypertensive agents and show capabilities in inhibiting collagen synthesis by cancer-associated fibroblasts. Up to now, no attempt has been made to achieve a local and sustained release of Los and Tel in tumors while alleviating the side effects after systemic administration. In the previous study, micelles were loaded into fiber fragments to achieve high drug accumulation in tumors after intratumoral administration. In the current study, Los and Tel are blend electrospun into fibers to retard the collagen synthesis and promote the tissue penetration of micelles released from fiber fragments. The loading of Los and Tel shows no effect on the micelle release, cellular uptake, and cytotoxicities of micelles released from fiber fragments. Because of the hydrophilicity, Los is almost released out after 5 day in pH 6.8 buffers, while hydrophobic Tel is gradually released for 30 days. Thus, fiber fragments with loaded Los and Tel are combined to achieve a sustained remodeling of collagen levels in tumors, and the combination with a ratio of 1/2 showed the most significant and consistent reductions of collagen I levels in tumors, as determined via Western blotting, Masson's trichrome, and immunofluorescence staining. A wide distribution of micelles is observed in the tumor tissues, as well as strong fluorescence in the distal sections of tumors during 14 days. Compared with pristine fiber fragments, the sequential release of Los and Tel induces stronger inhibition of tumor growth, lower expression of hypoxia-inducible factor-α (HIF-α), and fewer tumor metastases to lungs. Thus, this study demonstrates a feasible strategy to enhance the local retention and even distribution of chemotherapeutic agents in tumors in favor of therapeutic efficacy.