A novel role of Cx43-composed GJIC in PDT phototoxicity: an implication of Cx43 for the enhancement of PDT efficacy

Current Photodynamic Therapy for Glioma Treatment: An Update

Research on the development of photodynamic therapy for the treatment of brain tumors has shown promise in the treatment of this highly aggressive form of brain cancer. Analysis of both in vivo studies and clinical studies shows that photodynamic therapy can provide significant benefits, such as an improved median rate of survival. The use of photodynamic therapy is characterized by relatively few side effects, which is a significant advantage compared to conventional treatment methods such as often-used brain tumor surgery, advanced radiotherapy, and classic chemotherapy. Continued research in this area could bring significant advances, influencing future standards of treatment for this difficult and deadly disease.

Systematic Review of Photodynamic Therapy in Gliomas

Over the last 20 years, gliomas have made up over 89% of malignant CNS tumor cases in the American population (NIH SEER). Within this, glioblastoma is the most common subtype, comprising 57% of all glioma cases. Being highly aggressive, this deadly disease is known for its high genetic and phenotypic heterogeneity, rendering a complicated disease course. The current standard of care consists of maximally safe tumor resection concurrent with chemoradiotherapy. However, despite advances in technology and therapeutic modalities, rates of disease recurrence are still high and survivability remains low. Given the delicate nature of the tumor location, remaining margins following resection often initiate disease recurrence. Photodynamic therapy (PDT) is a therapeutic modality that, following the administration of a non-toxic photosensitizer, induces tumor-specific anti-cancer effects after localized, wavelength-specific illumination. Its effect against malignant glioma has been studied extensively over the last 30 years, in pre-clinical and clinical trials. Here, we provide a comprehensive review of the three generations of photosensitizers alongside their mechanisms of action, limitations, and future directions.

The role of fibroblast growth factor 7 in cartilage development and diseases

Fibroblast growth factor 7 (FGF7), also known as keratinocyte growth factor (KGF), shows a crucial biological significance in tissue development, wound repair, tumorigenesis, and immune reconstruction. In the skeletal system, FGF7 directs the cellular synaptic extension of individual cells and facilities functional gap junction intercellular communication of a collective of cells. Moreover, it promotes the osteogenic differentiation of stem cells via a cytoplasmic signaling network. For cartilage, reports have indicated the potential role of FGF7 on the regulation of key molecules Cx43 in cartilage and Runx2 in hypertrophic cartilage. However, the molecular mechanism of FGF7 in chondrocyte behaviors and cartilage pathological process remains largely unknown. In this review, we systematically summarize the recent biological function of FGF7 and its regulatory role on chondrocytes and cartilage diseases, especially through the hot focus of two key molecules, Runx2 and Cx43. The current knowledge of FGF7 on the physiological and pathological processes of chondrocytes and cartilage provides us new cues for wound repair of cartilage defect and therapy of cartilage diseases.

The roles of connexins and gap junctions in the progression of cancer

Gap junctions (GJs), which are composed of connexins (Cxs), provide channels for direct information exchange between cells. Cx expression has a strong spatial specificity; however, its influence on cell behavior and information exchange between cells cannot be ignored. A variety of factors in organisms can modulate Cxs and subsequently trigger a series of responses that have important effects on cellular behavior. The expression and function of Cxs and the number and function of GJs are in dynamic change. Cxs have been characterized as tumor suppressors in the past, but recent studies have highlighted the critical roles of Cxs and GJs in cancer pathogenesis. The complex mechanism underlying Cx and GJ involvement in cancer development is a major obstacle to the evolution of therapy targeting Cxs. In this paper, we review the post-translational modifications of Cxs, the interactions of Cxs with several chaperone proteins, and the effects of Cxs and GJs on cancer. Video Abstract.

Connexin 43 Contributes to the Sensitization of Colorectal Cancer Cells to Photodynamic Therapy through Akt Inhibition

BACKGROUND

Photodynamic therapy could be one approach to treat colorectal cancer, but resistance leads to failure of therapy. Akt activation is a cellular survival response to photodynamic therapy and is also a reason for resistance. Thus, inhibition of Akt is a strategy to decrease resistance. Akt interacts with connexin 43, another protein involved in photodynamic therapy resistance. Connexin 43 is widely expressed in different human tissues and has a complex role in tumor development. However, the mechanism of inhibition of Akt by connexin 43 that sensitizes colorectal cancer cells to photodynamic therapy needs further investigation.

METHODS

In this study, two colorectal cancer cells with low phosphorylated connexin 43 level were used to explore this mechanism. LY294002 was used as an Akt inhibitor, and connexin 43-pCMV3 was transfected into cells to increase connexin 43 expression.

RESULTS

Akt and connexin 43 inhibit each other in both colorectal cancer cell lines. In vitro and in vivo experiments showed that LY294002 and connexin 43 transfection sensitized cells to hematoporphyrin-Photodynamic therapy. LY294002 increased the sensitivity of cells to photodynamic therapy with a pronounced effect in cells with high expression levels of connexin 43.

CONCLUSIONS

Connexin 43 should be considered an important factor in increasing the phototoxicity of photodynamic therapy in colorectal cancer through Akt inhibition.

Opportunities and challenges of patient-derived models in cancer research: patient-derived xenografts, patient-derived organoid and patient-derived cells

Background

As reported, preclinical animal models differ greatly from the human body. The evaluation model may be the colossal obstacle for scientific research and anticancer drug development. Therefore, it is essential to propose efficient evaluation systems similar to clinical practice for cancer research.

Main body

While it has emerged for decades, the development of patient-derived xenografts, patient-derived organoid and patient-derived cell used to be limited. As the requirements for anticancer drug evaluation increases, patient-derived models developed rapidly recently, which is widely applied in basic research, drug development, and clinical application and achieved remarkable progress. However, there still lack systematic comparison and summarize reports for patient-derived models. In the current review, the development, applications, strengths, and challenges of patient-derived models in cancer research were characterized.

Conclusion

Patient-derived models are an indispensable approach for cancer research and human health.

Targeting X box-binding protein-1 (XBP1) enhances the sensitivity of HOS osteosarcoma cells to pyropheophorbide- α methyl ester-mediated photodynamic therapy

Photodynamic therapy (PDT), utilizes a photochemical reaction between photosensitizer and light to cause cancer death by generating reactive oxygen species (ROS). X-box binding protein 1 (XBP1), a downstream product of the IRE1α-XBP1 pathway, regulates diverse target genes, including various proto-oncogenes and its overexpression was closely related to the occurrence and progression of malignant tumors. The present study was performed to explore the role of XBP1 in human osteosarcoma HOS cells treated with pyropheophorbide-α methyl ester (MPPα)-mediated photodynamic therapy (PDT) (MPPα-PDT) and its potential mechanisms. The protein IRE1α and XBP1 increased with a time-dependent manner after MPPα-PDT treated, which indicated that MPPα-PDT induced the activation of the IRE1α-XBP1 pathway in HOS cells. Besides, MPPα-PDT treated alone or combined with XBP1 knockdown could both restrain the cell viability, but the latter one has more notable effect, which indicated that XBP1 knockdown may enhance the cell inhibitory effect by MPPα-PDT. Simultaneously, the apoptotic rate measured by flow cytometry (FCM) was increased surprisedly and the expression of apoptosis proteins was increased when knockdown XBP1 under the MPPα-PDT. In addition, antioxidant-related proteins such as the Catalase and SOD1 protein levels decreased, while the intracellular ROS content increased in HOS cells when knockdown XBP1 under the MPPα-PDT. These results suggested that the mechanism of XBP1 mediating resistance in HOS cells might be related to the expression of antioxidant molecules. In summary, this study found that the IRE1α-XBP1 pathway was activated in HOS cells after MPPα-PDT treated, and furthermore, XBP1 knockdown could decrease HOS cell viability through apoptosis and enhance the anti-tumor effect of MPPα-PDT remarkably in the meantime, which related to the regulation of oxidation-antioxidant system.

Connexin Hemichannel Activation by S-Nitrosoglutathione Synergizes Strongly with Photodynamic Therapy Potentiating Anti-Tumor Bystander Killing

Simple Summary

Bystander effects depend on direct cell-cell communication and/or paracrine signaling mediated by the release of soluble factors into the extracellular environment and may greatly influence therapy outcome. Although the limited data available suggest a role for intercellular gap junction channels, far less is known about the role of connexin hemichannels. Here, we investigated bystander effects induced by photodynamic therapy in syngeneic murine melanoma models in vivo. We determined that (i) photoactivation of a photosensitizer triggered calcium-dependent cell death pathways in both irradiated and bystander tumor cells; (ii) hemichannel activity and adenosine triphosphate release were key factors for the induction of bystander cell death; and (iii) bystander cell killing and antitumor response elicited by photodynamic therapy were greatly enhanced by combination treatment with S-nitrosoglutathione, which promoted hemichannel opening in these experimental conditions. Therefore, these findings in a preclinical model have important translational potential.

Abstract

In this study, we used B16-F10 cells grown in the dorsal skinfold chamber (DSC) preparation that allowed us to gain optical access to the processes triggered by photodynamic therapy (PDT). Partial irradiation of a photosensitized melanoma triggered cell death in non-irradiated tumor cells. Multiphoton intravital microscopy with genetically encoded fluorescence indicators revealed that bystander cell death was mediated by paracrine signaling due to adenosine triphosphate (ATP) release from connexin (Cx) hemichannels (HCs). Intercellular calcium (Ca²⁺) waves propagated from irradiated to bystander cells promoting intracellular Ca²⁺ transfer from the endoplasmic reticulum (ER) to mitochondria and rapid activation of apoptotic pathways. Combination treatment with S-nitrosoglutathione (GSNO), an endogenous nitric oxide (NO) donor that biases HCs towards the open state, greatly potentiated anti-tumor bystander killing via enhanced Ca²⁺ signaling, leading to a significant reduction of post-irradiation tumor mass. Our results demonstrate that HCs can be exploited to dramatically increase cytotoxic bystander effects and reveal a previously unappreciated role for HCs in tumor eradication promoted by PDT.