Methylene blue photodynamic therapy induces selective and massive cell death in human breast cancer cells

Abstract

BackgroundBreast cancer is the main cause of mortality among women. The disease presents high recurrence mainly due to incomplete efficacy of primary treatment in killing all cancer cells. Photodynamic therapy (PDT), an approach that causes tissue destruction by visible light in the presence of a photosensitizer (Ps) and oxygen, appears as a promising alternative therapy that could be used adjunct to chemotherapy and surgery for curing cancer. However, the efficacy of PDT to treat breast tumours as well as the molecular mechanisms that lead to cell death remain unclear.MethodsIn this study, we assessed the cell-killing potential of PDT using methylene blue (MB-PDT) in three breast epithelial cell lines that represent non-malignant conditions and different molecular subtypes of breast tumours. Cells were incubated in the absence or presence of MB and irradiated or not at 640 nm with 4.5 J/cm2. We used a combination of imaging and biochemistry approaches to assess the involvement of classical autophagic and apoptotic pathways in mediating the cell-deletion induced by MB-PDT. The role of these pathways was investigated using specific inhibitors, activators and gene silencing.ResultsWe observed that MB-PDT differentially induces massive cell death of tumour cells. Non-malignant cells were significantly more resistant to the therapy compared to malignant cells. Morphological and biochemical analysis of dying cells pointed to alternative mechanisms rather than classical apoptosis. MB-PDT-induced autophagy modulated cell viability depending on the cell model used. However, impairment of one of these pathways did not prevent the fatal destination of MB-PDT treated cells. Additionally, when using a physiological 3D culture model that recapitulates relevant features of normal and tumorous breast tissue morphology, we found that MB-PDT differential action in killing tumour cells was even higher than what was detected in 2D cultures.ConclusionsFinally, our observations underscore the potential of MB-PDT as a highly efficient strategy which could use as a powerful adjunct therapy to surgery of breast tumours, and possibly other types of tumours, to safely increase the eradication rate of microscopic residual disease and thus minimizing the chance of both local and metastatic recurrence.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-017-3179-7) contains supplementary material, which is available to authorized users.

Distinct photooxidation-induced cell death pathways lead to selective killing of human breast cancer cells

“…As a first step in our study, we confirmed previous results from our group 13 by showing that cell death kinetics after MB-PDT exerted a higher impact in the malignant cell lines, being TNBC cells the most susceptible ( Figure 1A ). We then set out to investigate the molecular basis of these cell type specific differential responses to the therapy.…”

“…We then set out to investigate the molecular basis of these cell type specific differential responses to the therapy. Since MB-PDT relies on a massive intracellular generation of oxidant species 9,13,17 , with a widespread impact in membranes, we evaluated whether there was a link between the cellular lipid profile and the sensitivity to MB-PDT. For this purpose, we performed a comparative lipidomic profiling of BC using reversed-phase ultra-high-performance liquid chromatography (RP-UHPLC) coupled to electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS).…”

“…In previous studies we have already reported that there were differences in MB-PDT sensitivity regarding MB concentration, time to achieve maximal cell death and the effect of fluence rate 9,13 . Moreover, our results have shown that non-tumorigenic breast cells are more resistant to MB-PDT, whereas the very aggressive triple negative breast cancer cells (TNBC) displayed the highest susceptibility 13 . However, the mechanisms behind these effects are still not well understood.…”

Photodynamic treatment with anionic nanoclays containing curcumin on human triple‐negative breast cancer cells: Cellular and biochemical studies

“…So, there is a need to develop not only effective therapies to reduce the mortality arising, but also increase the life quality of patients. [32][33][34] . In fact, common treatments like drugs and hormone therapy that target receptors are ineffective for this kind of breast cancer.…”

Nanoparticle‐based photothermal and photodynamic immunotherapy for tumor treatment

“…73 It is as a promising candidate for the treatment of cancers, such as colorectal, breast, lung and skin cancers. [74][75][76][77] PDT relies on the selective retention of photosensitizers (PSs) in tumor tissues under the activation of a specific wavelength of excitation light in the presence of molecular oxygen to generate singlet oxygen and other ROS, leading to tumor cell apoptosis and necrosis. 78 Three key factors, namely, PS, excitation light and oxygen, are involved in this process and constrain the efficacy of PDT.…”