Photodynamic therapy in cholangiocarcinoma: an overview

Novel zinc‑ and silicon‑phthalocyanines as photosensitizers for photodynamic therapy of cholangiocarcinoma

Photodynamic therapy (PDT) has emerged as an effective and minimally invasive cancer treatment modality. In the present study, two novel phthalocyanines, tetra‑triethyleneoxysulfonyl substituted zinc phthalocyanine (ZnPc) and dihydroxy‑2,9(10),16(17),23(24)‑tetrakis(4,7,10‑trioxaundecan‑1‑sulfonyl) silicon phthalocyanine (Pc32), were investigated as photosensitizers (PS) for PDT of cholangiocarcinoma (CC). ZnPc showed a pronounced dose‑dependent and predominantly cytoplasmic accumulation in EGI‑1 and TFK‑1 CC cell lines. Pc32 also accumulated in the CC cells, but this was less pronounced. Without photoactivation, the PS did not exhibit any antiproliferative or cytotoxic effects. Upon photoactivation, ZnPc induced the formation of reactive oxygen species (ROS) and immediate phototoxicity, leading to a dose‑dependent decrease in cell proliferation, and an induction of mitochondria‑driven apoptosis and cell cycle arrest of EGI‑1 and TFK‑1 cells. Although photoactivated Pc32 also induced ROS formation in the two cell lines, the extent was less marked, compared with that induced by ZnPc‑PDT, and pronounced antipoliferative effects occurred only in the less differentiated EGI‑1 cells, whereas the more differentiated TFK‑1 cells did not show sustained growth inhibition upon Pc32‑PDT induction. In vivo examinations on the antiangiogenic potency of the novel PS were performed using chorioallantoic membrane (CAM) assays, which revealed reduced angiogenic sprouting with a concomitant increase in nonperfused regions and degeneration of the vascular network of the CAM following induction with ZnPc‑PDT only. The study demonstrated the pronounced antiproliferative and antiangiogenic potency of ZnPc as a novel PS for PDT, meriting further elucidation as a promising PS for the photodynamic treatment of CC.

Novel Silicone-Coated 125I Seeds for the Treatment of Extrahepatic Cholangiocarcinoma

125I seeds coated with titanium are considered a safe and effective interstitial brachytherapy for tumors, while the cost of 125I seeds is a major problem for the patients implanting lots of seeds. The aim of this paper was to develop a novel silicone coating for 125I seeds with a lower cost. In order to show the radionuclide utilization ratio, the silicone was coated onto the seeds using the electro-spinning method and the radioactivity was evaluated, then the anti-tumor efficacy of silicone 125I seeds was compared with titanium 125I seeds. The seeds were divided into four groups: A (control), B (pure silicone), C (silicone 125I), D (titanium 125I) at 2 Gy or 4 Gy. Their anti-tumour activity and mechanism were assessed in vitro and in vivo using a human extrahepatic cholangiocarcinoma cell line FRH-0201 and tumor-bearing BALB/c nude mice. The silicone 125I seeds showed higher radioactivity; the rate of cell apoptosis in vitro and the histopathology in vivo demonstrated that the silicone 125I seeds shared similar anti-tumor efficacy with the titanium 125I seeds for the treatment of extrahepatic cholangiocarcinoma, while they have a much lower cost.

Prioritization of natural extracts by LC-MS-PCA for the identification of new photosensitizers for photodynamic therapy

Photodynamic therapy (PDT) is an alternative treatment for cancer that involves administration of a photosensitive drug or photosensitizer that localizes at the tumor tissue followed by in situ excitation at an appropriate wavelength of light. Tumour tissues are then killed by cytotoxic reactive oxygen species generated by the photosensitizer. Targeted excitation and photokilling of affected tissues is achieved through focal light irradiation, thereby minimizing systemic side effects to the normal healthy tissues. Currently, there are only a small number of photosensitizers that are in the clinic and many of these share the same structural core based on cyclic tetrapyrroles. This paper describes how metabolic tools are utilized to prioritize natural extracts to search for structurally new photosensitizers from Malaysian biodiversity. As proof of concept, we analyzed 278 photocytotoxic extracts using a hyphenated technique of liquid chromatography-mass spectrometry coupled with principal component analysis (LC-MS-PCA) and prioritized 27 extracts that potentially contained new photosensitizers for chemical dereplication using an in-house UPLC-PDA-MS-Photocytotoxic assay platform. This led to the identification of 2 new photosensitizers with cyclic tetrapyrrolic structures, thereby demonstrating the feasibility of the metabolic approach.

A review of progress in clinical photodynamic therapy

Photodynamic therapy (PDT) has received increased attention since the regulatory approvals have been granted to several photosensitizing drugs and light applicators worldwide. Much progress has been seen in basic sciences and clinical photodynamics in recent years. This review will focus on new developments of clinical investigation and discuss the usefulness of various forms of PDT techniques for curative or palliative treatment of malignant and non-malignant diseases.