Photodynamic Therapy with Zinc Phthalocyanine Inhibits the Stemness and Development of Colorectal Cancer: Time to Overcome the Challenging Barriers?

Zinc phthalocyanine loaded- antibody functionalized nanoparticles enhance photodynamic therapy in monolayer (2-D) and multicellular tumour spheroid (3-D) cell cultures

In conventional photodynamic therapy (PDT), effective delivery of photosensitizers (PS) to cancer cells can be challenging, prompting the exploration of active targeting as a promising strategy to enhance PS delivery. Typically, two-dimensional (2-D) monolayer cell culture models are used for investigating targeted photodynamic therapy. However, despite their ease of use, these cell culture models come with certain limitations due to their structural simplicity when compared to three-dimensional (3-D) cell culture models such as multicellular tumour spheroids (MCTSs). In this study, we prepared gold nanoparticles (AuNPs) that were functionalized with antibodies and loaded with tetra sulphonated zinc phthalocyanine (ZnPcS4). Characterization techniques including transmission electron microscopy (TEM) was used to determine the size and morphology of the prepared nanoconjugates. We also conducted a comparative investigation to assess the photodynamic effects of ZnPcS4 alone and/or conjugated onto the bioactively functionalized nanodelivery system in colorectal Caco-2 cells cultured in both in vitro 2-D monolayers and 3-D MCTSs. TEM micrographs revealed small, well distributed, and spherical shaped nanoparticles. Our results demonstrated that biofunctionalized nanoparticle mediated PDT significantly inhibited cell proliferation and induced apoptosis in Caco-2 cancer monolayers and, to a lesser extent, in Caco-2 MCTSs. Live/dead assays further elucidated the impact of actively targeted nanoparticle-photosensitizer nanoconstruct, revealing enhanced cytotoxicity in 2-D cultures, with a notable increase in dead cells post-PDT. In 3-D spheroids, however, while the presence of targeted nanoparticle-photosensitizer system facilitated improved therapeutic outcomes, the live/dead results showed a higher number of viable cells after PDT treatment compared to their 2-D monolayer counterparts suggesting that MCTSs showed more resistance to PS drug as compared to 2-D monolayers. These findings suggest a high therapeutic potential of the multifunctional nanoparticle as a targeted photosensitizer delivery system in PDT of colorectal cancer. Furthermore, the choice of cell culture model influenced the response of cancer cells to PDT treatment, highlighting the feasibility of using MCTSs for targeted PS delivery to colorectal cancer cells.

Caspase-1 Regulates the Apoptosis and Pyroptosis Induced by Phthalocyanine Zinc-Mediated Photodynamic Therapy in Breast Cancer MCF-7 Cells

Photodynamic therapy (PDT) is an innovative and perspective antineoplastic therapy. Tetra-α-(4-carboxyphenoxy) phthalocyanine zinc (TαPcZn)-mediated PDT (TαPcZn-PDT) has shown antitumor activity in some tumor cells, but the manner in which caspase-1 is involved in the regulation of apoptosis and pyroptosis in the TαPcZn-PDT-treated breast cancer MCF-7 cells is unclear. Therefore, effects of TαPcZn-PDT on cytotoxicity, cell viability, apoptosis, pyroptosis, cellular reactive oxygen species (ROS), mitochondrial membrane potential (ΔΨm), caspase-1, caspase-3, and nuclear transcription factor-κB (NFκB) in MCF-7 cells was firstly examined in the present study. The findings demonstrated that TαPcZn-PDT resulted in the increase in cytotoxicity and the percentage of apoptotic and pyroptotic cells, the reduction in cell viability and ΔΨm, the production of ROS and the activation of caspase-1, caspase-3 and NFκB in MCF-7 cells. Furthermore, the results also revealed that siRNA-targeting caspase-1 (siRNA-caspase-1) attenuated the effect of TαPcZn-PDT on apoptosis, pyroptosis and the activation of caspase-1, caspase-3 and NFκB in MCF-7 cells. Taken together, we conclude that caspase-1 regulates the apoptosis and pyroptosis induced by TαPcZn-PDT in MCF-7 cells.

Alteration of Mesenchymal Stem Cells Isolated from Glioblastoma Multiforme under the Influence of Photodynamic Treatment

The central hypothesis for the development of glioblastoma multiforme (GBM) postulates that the tumor begins its development by transforming neural stem cells into cancer stem cells (CSC). Recently, it has become clear that another kind of stem cell, the mesenchymal stem cell (MSC), plays a role in the tumor stroma. Mesenchymal stem cells, along with their typical markers, can express neural markers and are capable of neural transdifferentiation. From this perspective, it is hypothesized that MSCs can give rise to CSC. In addition, MSCs suppress the immune cells through direct contact and secretory factors. Photodynamic therapy aims to selectively accumulate a photosensitizer in neoplastic cells, forming reactive oxygen species (ROS) upon irradiation, initiating death pathways. In our experiments, MSCs from 15 glioblastomas (GB-MSC) were isolated and cultured. The cells were treated with 5-ALA and irradiated. Flow cytometry and ELISA were used to detect the marker expression and soluble-factor secretion. The MSCs' neural markers, Nestin, Sox2, and glial fibrillary acid protein (GFAP), were down-regulated, but the expression levels of the mesenchymal markers CD73, CD90, and CD105 were retained. The GB-MSCs also reduced their expression of PD-L1 and increased their secretion of PGE2. Our results give us grounds to speculate that the photodynamic impact on GB-MSCs reduces their capacity for neural transdifferentiation.

Increasing cancer permeability by photodynamic priming: from microenvironment to mechanotransduction signaling

The dense cancer microenvironment is a significant barrier that limits the penetration of anticancer agents, thereby restraining the efficacy of molecular and nanoscale cancer therapeutics. Developing new strategies to enhance the permeability of cancer tissues is of major interest to overcome treatment resistance. Nonetheless, early strategies based on small molecule inhibitors or matrix-degrading enzymes have led to disappointing clinical outcomes by causing increased chemotherapy toxicity and promoting disease progression. In recent years, photodynamic therapy (PDT) has emerged as a novel approach to increase the permeability of cancer tissues. By producing excessive amounts of reactive oxygen species selectively in the cancer microenvironment, PDT increases the accumulation, penetration depth, and efficacy of chemotherapeutics. Importantly, the increased cancer permeability has not been associated to increased metastasis formation. In this review, we provide novel insights into the mechanisms by which this effect, called photodynamic priming, can increase cancer permeability without promoting cell migration and dissemination. This review demonstrates that PDT oxidizes and degrades extracellular matrix proteins, reduces the capacity of cancer cells to adhere to the altered matrix, and interferes with mechanotransduction pathways that promote cancer cell migration and differentiation. Significant knowledge gaps are identified regarding the involvement of critical signaling pathways, and to which extent these events are influenced by the complicated PDT dosimetry. Addressing these knowledge gaps will be vital to further develop PDT as an adjuvant approach to improve cancer permeability, demonstrate the safety and efficacy of this priming approach, and render more cancer patients eligible to receive life-extending treatments.

Photodynamic therapy with zinc phthalocyanine enhances the anti-cancer effect of tamoxifen in breast cancer cell line: Promising combination treatment against triple-negative breast cancer?

Photodynamic therapy (PDT) is a light-based anti-neoplastic therapeutic approach. Growing evidence indicates that combining conventional anti-cancer therapies with PDT can be a promising approach to treat malignancies. Herein, we aimed to investigate anti-cancer effects of the combination treatment of zinc phthalocyanine (ZnPc)-PDT with tamoxifen (TA) on MDA-MB-231 cells (as a triple-negative breast cancer (TNBC) cell line). For this purpose, we investigated the cytotoxicity of TA and ZnPc-PDT on MDA-MB-231 cells performing the MTT assay. The effect of TA and ZnPc-PDT on the apoptosis of MDA-MB-231 cells was studied using Annexin V/PI and DAPI staining. The wound-healing assay, and colony formation assay were performed to study the effect of TA and ZnPc-PDT on the migration, and clonogenicity of MDA-MB-231 cells, respectively. The qRT-PCR was done to study the gene expression of caspase-8, caspase-9, caspase-3, ZEB1, ROCK1, SNAIL1, CD133, CD44, SOX2, and ABCG2 (ATP-binding cassette sub-family G member 2). Based on our results, monotherapies with TA and ZnPc-PDT can remarkably increase cell cytotoxicity effects, stimulate apoptosis via downregulating Bcl-2 and upregulating caspase-3 and caspase-9, inhibit migration via downregulating SNAIL1 and ZEB1, and suppress clonogenicity via downregulating SOX2 and CD44 in MDA-MB-231 cells. Besides, these monotherapies can downregulate the expression of ABCG2 in MDA-MB-231 cells. Nevertheless, the combination treatment can potentiate the above-mentioned anti-cancer effects compared to monotherapy with TA. Of interest, the combined treatment of TA with ZnPc-PDT can synergically increase cell cytotoxicity effects on MDA-MB-231 cells. In fact, synergistic effects were estimated by calculation of Combination Index (CI); that synergistic outcomes were observed in all groups. Also, this combination treatment can significantly upregulate the caspase-8 gene expression and downregulate ROCK1 and CD133 gene expression in MDA-MB-231 cells. Overall, our results show that ZnPc-PDT can more sensitize the MDA-MB-231 cells to TA treatment. Based on our knowledge and experiment, the synergistic effects of ZnPc-PDT and TA deserve further evaluation in cancer research.

Deconvoluting the complexity of autophagy in colorectal cancer: From crucial pathways to targeted therapies

Colorectal cancer (CRC) is a common gastrointestinal tumor with a high degree of malignancy, and most clinical cases are diagnosed at an advanced stage, which has unfortunately missed an opportunity for surgery; therefore, elucidation of the crucial pathways of CRC development and discovery of targeted therapeutic strategies should be anticipated. Autophagy, which is an evolutionarily highly conserved catabolic process, may promote tumorigenesis and development of CRC. On the contrary, autophagy can trigger programmed cell death to inhibit CRC progression. Correspondingly, several targeted therapeutic strategies have been reported in CRC, including small-molecule compounds, polypeptides, non-coding RNAs, photodynamic, and adjuvant therapies. Thus, in this review, we focus on summarizing the crucial pathways of autophagy in CRC, and further discuss the current therapeutic strategies targeting autophagy. Together, these findings may shed light on the key regulatory mechanisms of autophagy and provide more promising therapeutic approaches for the future CRC therapies.