Prevention of Distant Lung Metastasis After Photodynamic Therapy Application in a Breast Cancer Tumor Model.

The objective of this study was to investigate the activity of photodynamic therapy mediated by aluminum-chlorophthalocyanine contained in a polymeric nanostructured carrier composed by methyl vinyl ether-co-maleic anhydride (PVM/MA) against local subcutaneous breast cancer tumors and its effects against distant metastasis in a mouse tumor model. In our results, we observed a decrease in breast cancer tumor growth, prevention of distant lung metastases, and a significant increased survival in mice treated with photodynamic therapy. In addition to these results, we observed that tumor-bearing mice without treatment developed a significant extension of liver hematopoiesis that was significantly reduced in mice treated with photodynamic therapy. We hypothesized and showed that this reduction in (1) metastasis and (2) liver hematopoiesis may be related to the systemic activity of immature hematopoietic cells, specifically the myeloid-derived suppressor cells, which were suppressed in mice treated with photodynamic therapy. These cells produce a tolerogenic tumor environment that protects tumor tissues from immunological surveillance. Therefore, we suggest that photodynamic therapy could be employed in combination with other conventional therapies; such as surgery and radiotherapy, to improve the overall survival of patients diagnosed with breast cancer, as observed in our experimental resuIts.