Effects of photodynamic therapy with hypericin in mice bearing highly invasive solid tumors

The tumoricidal properties of photodynamic therapy (PDT) with hypericin (HY) were evaluated in a highly metastatic adenocarcinoma (DA3^Hi) and anaplastic squamous cell carcinoma (SQ2) tumors in vivo. Photosensitization of the tumor site with hypericin (HY-PDT) reduced primary tumor development and significantly prolonged the survival of tumor-bearing (TB) mice. Of these two tumors the squamous cell carcinoma emerged as more sensitive to HY-PDT compared with DA3^Hi adenocarcinoma both in vitro and in vivo. HY-PDT caused extensive tumor necrosis that was followed by local, intratumoral, and systemic inflammatory reactions. Analyses of cytokine mRNA profiles reveal increases in mRNA levels of expression confined to inflammation-related cytokines both within the tumor and also systemically (measured in spleens). However, there was no evidence for any HY-PDT-induced antitumoral immune reactions. Our results suggest that PDT with hypericin can be considered as a supplementary treatment in the management of some invasive and metastatic cancers such as squamous carcinoma and similar tumors.