Enlarging the Scope of 5-Aminolevulinic Acid-Mediated Photodiagnosis towards Breast Cancers

Today, most research on treating cancers targets one single cancer, often because of the very specific operation principle of the therapy. For instance, immunotherapies require the expression of a particular antigen, which might not be expressed in all cancers or in all patients. What about metastases? Combination therapies are promising but require treatment personalization and are an expensive approach that many health systems are not willing to pay for. Resection of cancerous tissues may be conducted beforehand. However, the precise location and removal of tumors are in most cases, hurdles that require margins to prevent recurrence. Herein, we further demonstrate the wide application of aminolevulinate-based photodynamic diagnosis and therapy toward breast cancers. By selecting four breast cancer cell lines that represent the main breast tumor subtypes, we investigated their ability to accumulate the fluorescent protoporphyrin IX upon treatment with the marketed 5-aminolevulinic acid hexyl ester (ALA-Hex) or our new and more stable derivative PSI-ALA-Hex. We found that all cell lines were able to accumulate PpIX under a few hours independent of their hormonal status with both treatments. Additionally, this accumulation was less dose-dependent with PSI-ALA-Hex and induced similar or higher fluorescence intensity than ALA-Hex in three out of four cell lines. The toxicity of the two molecules was not different up to 0.33 mM. However, PSI-ALA-Hex was more toxic at 1 mM, even though lower concentrations of PSI-ALA-Hex led to the same PpIX accumulation level. Additional illumination with blue light to induce cell death by generating reactive oxygen species was also considered. The treatments led to a dramatic death of the BT-474 cells under all conditions. In SK-BR-3 and MCF-7, ALA-Hex was also very efficient at all concentrations. However, increasing doses of PSI-ALA-Hex (0.33 and 1 mM) surprisingly led to a higher viability rate. In contrast, the triple-negative breast cancer cells MDA-MB-231 showed a higher death induction with higher concentrations of ALA-Hex or PSI-ALA-Hex. Derivatives of ALA seem promising as fluorescence-guided resection tools and may enable subsequent completion of cancer cell destruction by blue light irradiation.