Small molecular chelator for comprehensive regulation of tumor lactate levels in synergy with photodynamic therapy for cancer treatment

An increasing number of studies have focused on depleting lactate and modulating the tumor's lactic microenvironment to interfere with tumor progression, particularly in breast cancer. Lactate accumulation in tumors contributes to a highly acidic microenvironment that promotes cancer cell survival and resistance to therapies. However, existing lactate depletion agents, primarily enzymes and macromolecules, fall short of clinical applications due to poor stability and their ability to only perform solitary lactate depletion without interfering with the transport process. Consequently, the development of stable molecules that deplete lactate and interfere with lactate transport is critically needed. Therefore, in this study, chlorin e6 (Ce6)-gadolinium chloride (GdCl₃)-flavin adenine dinucleotide (FAD)/tamoxifen (TAM) molecular chelates were prepared. The chelates fully interfered with lactate transport, depleted lactate in the tumor microenvironment, mitigated photodynamic therapy resistance, and realized synergistic photodynamic-hormonal therapy. FAD has promising capabilities in regulating lactate levels and mitigating acidic microenvironments. However, a strategy for depleting lactate by chelating the coenzyme FAD to form nanoparticles has not yet been reported. Tamoxifen disrupts tumor development and interferes with lactate transport by binding to estrogen receptor and inhibiting the expression of monocarboxylate transporter. In addition, coupling with Gd³⁺ increased the solubility of Ce6, thereby improving the photodynamic therapy effectiveness. This innovative strategy improves therapeutic efficacy and offers a promising approach for breast cancer treatment.