Methylene blue-mediated Photodynamic Therapy in human retinoblastoma cell lines

Mimicking Retinoblastoma Treatment With Repeated Topotecan or Melphalan Develops Cross-Resistance to Classic Agents But Not to Repurposed Drugs

Purpose

Refractory or recurrent retinoblastoma results from acquired chemoresistance and the management of these eyes often requires surgical removal. Our objective was to develop retinoblastoma models resistant to chemotherapy by exposing cancer cells to repeated chemotherapy mimicking the clinical scenario. These newly resistant cells were used to evaluate potential novel therapies.

Methods

Chemoresistant cells were obtained by exposing two primary retinoblastoma cell cultures to three weekly doses of melphalan or topotecan. The sensitivity of these resistant cells to each chemotherapy was evaluated, and cross-resistance to topotecan, melphalan, and carboplatin was assessed. Genomic alterations and differential expression of efflux/influx transporters between chemoresistant and parental cells were analyzed. Subsequently, sensitivity of both resistant and parental cells to the repurposed agents digoxin, methylene blue, and gemcitabine was assessed.

Results

Four chemoresistant models were successfully established, showing significantly higher half-maximal inhibitory concentration (IC50) values for melphalan and topotecan compared to their corresponding parental cells (P < 0.05). Cross-resistance between melphalan and topotecan was demonstrated, with a 3-fold increase in the IC50. Chemoresistant cells also showed reduced sensitivity to carboplatin (P < 0.05) compared to parental cells, whereas sensitivity to the evaluated repurposed agents remained unchanged. Genomic analysis revealed no selective alterations in the resistant cells, although differential expression of influx/efflux transporters was observed across all chemoresistant models.

Conclusions

In vitro simulation of patient treatment was useful to establish chemoresistant retinoblastomas and to identify strategies to overcome resistance to topotecan or melphalan through drug repurposed. Our results warrant further investigation to support the clinical translation.

Singlet Oxygen-Induced Mitochondrial Reset in Cancer: A Novel Approach for Ovarian Cancer Therapy

Background/Objectives: This study explores the generation of singlet oxygen (SO) through methylene blue (MB) activation as a metabolic intervention for ovarian cancer. We aimed to examine the role of SO in modulating mitochondrial function, cellular metabolism, and proliferation in ovarian cancer cell lines compared to control cells. Methods: The study utilized two ovarian cancer cell lines, OV1369-R2 and TOV1369, along with ARPE-19 control cells. Following MB treatment and light activation, mitochondrial function and ATP synthesis were assessed. Metabolomic analyses were performed to evaluate changes in central carbon metabolism, particularly focusing on markers of the Warburg effect. Results: TOV1369 cells exhibited a pronounced sensitivity to MB treatment, resulting in significant inhibition of ATP synthesis and reduced proliferation. Metabolomic analysis indicated that MB-induced SO production partially reversed the Warburg effect, suggesting a shift from glycolysis to oxidative phosphorylation. These effects were less pronounced in OV1369-R2 and ARPE-19 cells, correlating with their lower MB sensitivity. Conclusions: MB-generated SO selectively modulates mitochondrial energetics in ovarian cancer cells, driving a metabolic reorganization that curtails their proliferative capacity. This approach, leveraging the bacterial-like features of cancer metabolism, offers a promising therapeutic avenue to induce apoptosis and enhance treatment outcomes in ovarian cancer.

In Vitro Methylene Blue and Carboplatin Combination Triggers Ovarian Cancer Cells Death

Ovarian cancer presents a dire prognosis and high mortality rates, necessitating the exploration of alternative therapeutic avenues, particularly in the face of platinum-based chemotherapy resistance. Conventional treatments often overlook the metabolic implications of cancer, but recent research has highlighted the pivotal role of mitochondria in cancer pathogenesis and drug resistance. This study delves into the metabolic landscape of ovarian cancer treatment, focusing on modulating mitochondrial activity using methylene blue (MB). Investigating two epithelial ovarian cancer (EOC) cell lines, OV1369-R2 and OV1946, exhibiting disparate responses to carboplatin, we sought to identify metabolic nodes, especially those linked to mitochondrial dysfunction, contributing to chemo-resistance. Utilizing ARPE-19, a normal retinal epithelial cell line, as a control model, our study reveals MB's distinct cellular uptake, with ARPE-19 absorbing 5 to 7 times more MB than OV1946 and OV1369-R2. Treatment with 50 µM MB (MB-50) effectively curtailed the proliferation of both ovarian cancer cell lines. Furthermore, MB-50 exhibited the ability to quell glutaminolysis and the Warburg effect in cancer cell cultures. Regarding mitochondrial energetics, MB-50 spurred oxygen consumption, disrupted glycolytic pathways, and induced ATP depletion in the chemo-sensitive OV1946 cell line. These findings highlight the potential of long-term MB exposure as a strategy to improve the chemotherapeutic response in ovarian cancer cells. The ability of MB to stimulate oxygen consumption and enhance mitochondrial activity positions it as a promising candidate for ovarian cancer therapy, shedding light on the metabolic pressures exerted on mitochondria and their modulation by MB, thus contributing to a deeper understanding of mitochondrial dysregulation and the metabolic underpinnings of cancer cell proliferation.

Methylene Blue Metabolic Therapy Restrains In Vivo Ovarian Tumor Growth

Ovarian cancer remains a significant challenge, especially in platinum-resistant cases where treatment options are limited. In this study, we investigated the potential of methylene blue (MB) as a metabolic therapy and complementary treatment approach for ovarian cancer. Our findings demonstrated a significant in vivo reduction in the proliferation of TOV112D-based ovarian-cell-line xenografts. In this preclinical study, which used a carboplatin-resistant ovarian cancer tumor model implanted into mice, MB-mediated metabolic therapy exhibited superior tumor slowdown compared to carboplatin treatment alone. This indicates, for the first time, MB's potential as an alternative or adjuvant treatment, especially for resistant cases. Our in vitro study on TOV112D and ARPE-19 sheds light on the impact of such an MB-based metabolic therapy on mitochondrial energetics (respiration and membrane potential). MB showed a modulatory role in the oxygen consumption rate and the mitochondrial membrane potential. These results revealed, for the first time, that MB specifically targets TOV112D mitochondria and probably induces cell apoptosis. The differential response of normal (ARPE-19) and cancer (TOV112D) cells to the MB treatment suggests potential alterations in cancer cell mitochondria, opening avenues for therapeutic approaches that target the mitochondria. Overall, our findings suggest the efficacy of MB as a possible treatment for ovarian cancer and provide valuable insights into the mechanisms underlying the efficacy of methylene blue metabolic therapy in ovarian cancer treatment.

Advanced methylene blue - nanoemulsions for in vitro photodynamic therapy on oral and cervical human carcinoma

Photodynamic therapy (PDT) is a therapeutic modality with high contributions in the treatment of cancer. This approach is based on photophysical principles, which presents as a less invasive strategy than conventional therapies. Combined with nanotechnology, the therapy becomes more efficient because nanoparticles (NPs) have advantageous characteristics such as biocompatibility, controlled, and targeted release, promoting solubility and decreasing the toxicity and side effects involved. In this work were developed nanoemulsions containing the methylene blue photosensitizer (MB) (MB/NE) and in the empty form (unloaded/NE). Subsequently, the mentioned nanomaterials were characterized by the measurement of dynamic light scattering (DLS). The MB/NE and unloaded/NE showed appropriate physical and chemical characteristics, with particle size ≤ 200 nm, polydispersity index close to 0.3, and zeta potential exhibiting negative charge, showing stable values during the analysis. The incorporation of the MB did not cause changes in the photophysical profile of the photosensitizer. The quantification performed showed an incorporation rate of 81.9%. Viability studies showed an absence of cytotoxicity for MB/NE in the concentrations of 10-75 µmol·L^-1, free MB at the concentration of 75 µmol·L^-1, and unloaded NE 47.5% (v/v), presenting viability close to 90%, respectively. PDT in vitro protocols applied to OSCC and HeLa cells showed a decrease in cell viability through only one irradiation, evidencing the photodynamic activity of the formulation when applied to cancer cells. The results obtained were superior to those found in the literature where they use free MB, showing that the association between nanotechnology and PDT optimizes the proposed protocol. From the results obtained, it is possible to indicate that the NE have high stability, with satisfactory physical-chemical parameters, in addition to not presenting cytotoxicity in the tested concentrations, showing their in vitro biocompatibility, in addition to presenting satisfactory effects when combined MB/NE with PDT, showing the potential of MB/NE as a very promising nanostructured photosensitizer for the treatment of some types of cancer.