Enhancement of photodynamic therapy effect by temporally inhibiting infarction with anticoagulant heparin

Photodynamic Therapy (PDT) is one of the tumor-targeting therapeutics, and has been an established medical practice in recent years. PDT mediates tumor destruction mainly by killing tumor cells directly and damaging the tumor-associated vasculature, also inducing an immune response against tumor cells. For the Photofrin-mediated PDT, Vascular system injury is the predominant destruction that results in vascular collapse and blood plasma leakage, then leading to tumor infarction. However, thrombus formation during PDT may influence the light transmission and oxygen supply. Also some tumor cells not killed by PDT may irritate angiogenesis, causing the tumor recurrence under the condition of hypoxia after PDT. In our work, to prolong coagulation and formation of thrombus, an anticoagulant heparin was employed before the Photofrin-mediated PDT. After being administrated both Photofrin and anticoagulant heparin, the BALB/c mice with the subcutaneous EMT6 mammary carcinomas model were exposed to laser (635nm). And then an enhanced effect was received. Our experiments indicated that its antitumor effect may be attributed to the improvement of the light delivery to the deep part of tumor and oxygen supply for PDT. The results suggested that heparin can be used to enhance the effect of PDT in a solid tumor treatment.