Sequential effects of photodynamic treatment of basal cell carcinoma

Background: Photodynamic therapy (PDT) of superficial basal cell carcinoma (SBCC) acts as a biological response modifier or killing target cells, but sequential biological effects have not been reported in depth in humans. Methods: In 15 patients with SBCC treated with aminolevulinic acid (ALA)-PDT, inflammatory infiltrate, apoptosis phenomena and tumor-derived molecules were investigated on biopsies at baseline, and after 15 min and 4, 24, 48 and 72 h, by immunohistochemistry and ultrastructure. Results: Early apoptosis of keratinocytes was already observed at 15 min, while late apoptotic markers were maximally found at 24 h. Baseline mast cells tended to slightly increase up to 72 h; polymorphonuclear phagocytes significantly increased at 4 h but decreased at 24/48/72 h; on the contrary, lymphocytes and macrophages gradually increased starting at baseline. At baseline, SBCC cells expressed stem cell factor in all cases, and granulocyte-monocyte colony-stimulating factor, basic fibroblastic growth factor, interleukin (IL)-8 and vascular endothelial growth factor in most cases. IL-6 and monocyte chemoattractant protein-1 were poorly expressed, and transforming growth factor-beta was absent. Conclusions: We show a clear time-dependent profile of apoptotic markers and inflammatory infiltrate composition in SBCC after ALA-PDT. SBCC cells express cytokines and chemotactic molecules that are likely related to the recruitment of inflammatory cells.