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.