Introduction

Photodynamic therapy (PDT) is a relatively non-invasive anti-cancer therapy that employs a photosensitizer and a specific wavelength of light irradiation. PDT induces tumor shrinkage in various malignancies due to three main mechanisms, direct effects of reactive oxygen species (ROS), vascular shutdown leading to tumor infarction, and acute inflammation with immune response. Among them, ROS is important factor of DNA damage. It was reported that cGAS (cyclic GMP-AMP synthase)-STING (stimulator of interferon genes) pathway regulates a transcriptional program that controls the generation of ROS and that STING loss alters ROS homeostasis. STING loss reduces ROS induction and that causes therapeutic resistance. Thus, we predicted that pharmacological activation of cGAS-STING pathway would be an actionable target for reducing therapeutic resistance and enhance DNA damage caused by PDT. Our study investigated the efficacy of STING agonist (2'-3'-cyclic GMP-AMP sodium or AUS-100) combined with talaporfin sodium PDT.

Aims & Methods

1. We established STING knockout cells in a colon cancer cell line (HCT116) using CRISPER-Cas9.
2. We compared the induction of cell death after in vitro talaporfin PDT in parental and knockout cells. We analyzed IC50 by MMT assay.
3. We measured ROS generation, using DCFDA assay after in vitro talaporfin PDT in parental and knockout cells.
4. We analyzed the induction of cell death treated with ROS scavenger (N-acetyl cysteine; NAC) after in vitro talaporfin PDT in parental and knockout cells.
5. We measured DNA damage by immunofluorescence microscopy with an anti–g-H₂AX antibody after in vitro talaporfin PDT in parental and knockout cells.
6. We investigated PDT-induced STING pathway activation of STING-regulated genes by western blot analyses after in vitro PDT in parental and knockout cells.
7. We compared the in vivo efficacy of talaporfin PDT between the parental and knockout cells.
8. We assessed the in vivo efficacy of talaporfin PDT, STING agonist (2'-3'-cyclic GMP-AMP sodium or AUS-100), and their combination in a xenograft tumor model bearing HCT116.

Results

1. We established STING knockout cell. STONG knockout was confirmed by western blot analyses.
2. STING KO suppressed cell death induction of TS-PDT (IC₅₀ 12.5 (±1.35) vs 14.5 (±1.18)μmol/L).
3. STING KO suppressed TS-PDT induced ROS generation (M.F.I. 4491 vs 1706).
4. STING KO suppressed cell death induction of TS-PDT with NAC.
5. Treating parental cell lines with talaporfin PDT led to significantly more γ-H₂AX foci formation than in STING knockout cells.
6. At the protein level, TS-PDT enhanced TBK-1 phosphorylation in parental cell. STING dependent signaling was enhanced by TS-PDT, and the effects were eliminated by STING loss.
7. The in vivo efficacy against towards parental cells was significantly greater than that towards STING knockout cells.
8. The combination exhibited significantly greater tumor growth inhibition than by single agents alone in a xenograft tumor model.

Conclusion

We have established STING knockout cell using CRISPER-Cas9 and identified novel regulators of DNA damage in Photodynamic therapy. Our results point to a role for STING in DNA damage sensing and cyclic dinucleotide detection that goes beyond its conventional function. According to these results, talaporfin PDT is more effective when a STING agonist is used to control the degree of DNA damage. Combining talaporfin PDT with a STING agonist would offer a potentially strong combination for next-generation anticancer treatments.

Introduction

Esophageal squamous cell carcinoma (ESCC) is a major global health concern, with a high recurrence rate after chemoradiotherapy (CRT). Despite being a curative approach, CRT alone is often insufficient, leading to local recurrence in 30–40% of cases (1). Salvage treatments such as surgery and endoscopic resection have limitations, particularly in patients with comorbidities or advanced lesions (2). Photodynamic therapy (PDT) using talaporfin sodium (TS) has emerged as a promising, minimally invasive salvage treatment, offering advantages such as reduced phototoxicity and repeatability (3). Since its approval in Japan in 2015, TS-PDT has gained traction, yet further clinical evidence is needed to validate its efficacy and safety. This study aims to evaluate the clinical outcomes of TS-PDT as a salvage treatment for locally recurrent or residual ESCC following CRT or radiotherapy (RT).

Aims & Methods

A retrospective study was conducted at Nagoya City University Hospital between May 2016 and December 2023. A total of 29 patients with histologically confirmed local recurrence or residual ESCC post-CRT/RT were included. Eligible patients had lesions classified as ≤T2, without lymph node or distant metastasis. TS-PDT was administered with a diode laser (664 nm) 4–6 hours post-intravenous TS injection (40 mg/m²). Patients were monitored for adverse events, local complete response (L-CR), progression-free survival (PFS), and overall survival (OS). Kaplan–Meier analysis was used for survival estimation, and comparisons between single and multiple PDT sessions were evaluated.

Results

Table 1. The best response to PDT
	Local-CR	Non L-CR	L-CR rate
patients	22	5	81.5%
lesions	36	5	87.8%
T1b lesions	28	1	96.6%
T2 lesions	8	4	66.7%

Among the 29 patients (23 males, 6 females; median age, 72 years), TS-PDT achieved an L-CR rate of 82.1% per patient and 87.8% per lesion, with superior outcomes in T1b lesions (96.6%) compared to T2 lesions (66.7%) (Table1). The median local PFS was 1,324 days, and the median PFS was 912 days. OS was not reached during follow-up, with a 3-year survival rate of 70.7%. Seventeen patients underwent a single PDT session, while 12 required multiple sessions. The 3-year OS rate was 83.3% in the single-session group and 44.4% in the multiple-session group. No skin phototoxicity was observed. Adverse events included esophageal strictures (1 case, asymptomatic) and esophageal perforations (2 cases), one of which required surgical intervention.

Conclusion

TS-PDT demonstrated high local control rates and favorable survival outcomes, making it a promising salvage therapy for ESCC recurrence post-CRT/RT (4). Despite some adverse events, its minimal invasiveness and reduced phototoxicity enhance its applicability, particularly in elderly or high-risk patients. The effectiveness of multiple PDT sessions supports its role as a flexible treatment strategy. Further multicenter prospective trials are warranted to optimize patient selection, treatment protocols, and long-term outcomes, solidifying TS-PDT as a key salvage therapy for recurrent ESCC (5).

References

1. Hironaka S, Ohtsu A, Boku N, et al.: Nonrandomized comparison between definitive chemoradiotherapy and radical surgery in patients with T(2-3)N(any) M(0) squamous cell carcinoma of the esophagus. Int J Radiat Oncol Biol Phys 57: 425-433, 2003.
2. Tachimori Y, Kanamori N, Uemura N, Hokamura N, Igaki H and Kato H: Salvage esophagectomy after high-dose chemoradiotherapy for esophageal squamous cell carcinoma. J Thorac Cardiovasc Surg 137: 49-54, 2009.
3. Yano T, Kasai H, Horimatsu T, et al.: A multicenter phase II study of salvage photodynamic therapy using talaporfin sodium (ME2906) and a diode laser (PNL6405EPG) for local failure after chemoradiotherapy or radiotherapy for esophageal cancer. Oncotarget 8: 22135-22144, 2017.
4. Ikebuchi Y, Yoshida A, Kurumi H, et al.: Salvage Photodynamic Therapy Using Talaporfin Sodium for Local Failure of Esophageal Squamous Cell Carcinoma. Yonago Acta Med 64: 120-125, 2021.
5. Kai K, Nakashima K, Kawakami H, et al.: Clinical Impact of the Charlson Comorbidity Index on the Efficacy of Salvage Photodynamic Therapy Using Talaporfin Sodium for Esophageal Cancer. Intern Med 63: 903-910, 2024.

Introduction

Photodynamic therapy (PDT) is a treatment method in which tumor tissues incorporated with a photosensitizer (PS) are irradiated with incident light at an appropriate wavelength, causing a photochemical reaction that releases free radicals, resulting in the necrosis of tumor cells via oxidative stress. The second-generation photosensitizer, talaporfin, is rapidly eliminated from the skin and requires a shorter sunshade period (two weeks). The "abscopal effect," where radiotherapy at one site leads to regression of metastatic tumors not irradiated, has been reported in PDT (1). Studies on the synergistic effect of the abscopal effect in combination with immune checkpoint inhibitors (ICIs) have been reported in radiotherapy and other related fields. PDT induces not only a direct cytotoxic effect but also enhances tumor immunity (2). Therefore, we hypothesized that the addition of ICIs to PDT would regulate the immune system and promote the cancer immunity cycle, leading to the effective inhibition of tumor growth at both irradiated and non-irradiated sites. CTLA-4 and PD-1 inhibit T-cell activation through distinct and potentially synergistic mechanisms (3). In this study, we investigated the therapeutic efficacy of combining talaporfin PDT (TS-PDT) with dual ICIs (targeting PD-L1 and targeting CTLA-4).

Aims & Methods

1. To analyze the cell death mechanism induced by TS-PDT, we performed an apoptosis/necrosis assay and stained the cells with annexin V-fluorescein isothiocyanate and propidium iodide for flow cytometric analysis.
2. Furthermore, we measured CRT translocation after TS-PDT using immunofluorescence staining. We also measured the supernatant concentration of HMGB1 in the culture medium treated with TS-PDT to evaluate the release of HMGB1.
3. We assessed the in vivo efficacy of Talaporfin PDT, ICIs, and their combination using a xenograft tumor model.
4. For immunohistochemical analysis, we examined the expression of CD4 , CD8, and PD-L1.
5. IFN-γ, perforin 1 and granzyme B mRNA expression lvels in tumors were measured by qRT-PCR.

Results

1. The percentage of cells undergoing apoptosis and necrosis was higher in the TS-PDT group than in the untreated group. The mean fluorescence intensity of active caspase-3, a marker of apoptosis, was higher in the TS-PDT-treated cells than in the untreated cells.
2. Translocation of CRT from the nucleus to the cytoplasm was induced by TS-PDT. HMGB1 levels in the supernatant increased after TS-PDT.
3. The combination exhibited significantly greater tumor growth inhibition than either agent alone in a xenograft tumor model.
4. In non-irradiated tumors, the expression levels of CD4, CD8, and PD-L1 were elevated in the TS-PDT group. Combination of TS-PDT and ICIs reduced PD-L1 expression.
5. In the tumors on the non-irradiated side, combination therapy tended to induce IFN-γ, perforin 1, and granzyme B

Conclusion

Our results demonstrate that TS-PDT not only induces a direct cytotoxic effect on tumor cells but also enhances anti-tumor immunity and exhibits synergism with dual ICIs. Therefore, these findings suggest that a combination of TS-PDT and dual ICI antibodies may be a promising approach for the development of anti-tumor therapeutics.

References

(1) Duan X., Chan C., Guo N., Han W., Weichselbaum R.R., Lin W. Photodynamic therapy mediated by nontoxic core-shell nanoparticles synergizes with immune checkpoint blockade to elicit antitumor immunity and antimetastatic effect on breast cancer. J. Am. Chem. Soc. 2016;138:16686–16695. doi: 10.1021/jacs.6b09538.
(2) Makiko Sasaki, Mamoru Tanaka, Yuki Kojima, Hirotada Nishie, Takaya Shimura, Eiji Kubota, Hiromi Kataoka. Anti-tumor immunity enhancement by photodynamic therapy with talaporfin sodium and anti-programmed death 1 antibody. Mol Ther Oncolytics. 2023 Jan 2:28:118-131. doi: 10.1016/j.omto.2022.12.009. eCollection 2023 Mar 16.
(3) Parry RV, Chemnitz JM, Frauwirth KA, Lanfranco AR, Braunstein I, Kobayashi SV, Linsley PS, Thompson CB, Riley JL. CTLA-4 and PD-1 receptors inhibit T-cell activation by distinct mechanisms. Mol Cell Biol. 2005 Nov; 25(21): 9543–9553. doi: 10.1128/MCB.25.21.9543-9553.2005.

Introduction

Chemoradiotherapy (CRT) is a standard non-surgical treatment for esophageal squamous cell carcinoma (ESCC). One of the major disadvantages of CRT is poor local control, and salvage esophagectomy is generally indicated for local failure; however, it is invasive with a high rate of postoperative complications and mortality so that patients often refused or are intolerant to salvage esophagectomy. Alternatively, photodynamic therapy (PDT) with talaporfin sodium (TS) is less invasive salvage treatment for local failure after CRT/ radiotherapy (RT) and was reported to have relatively high local complete response (L-CR) rate and few adverse events (AEs) in the short term. However, long-term outcomes of PDT with TS are unknown.

Aims & Methods

This retrospective study aimed to clarify the long-term outcomes of PDT with TS for local failure after CRT/RT for ESCC. Patients who underwent PDT with TS for histologically proven local failure of ESCC between December 2012 and December 2021 at the National Cancer Center Hospital East were enrolled. Patients with other active cancers or a prior history of PDT were excluded. Basic indication criteria of PDT were as follows: invasion depth limited to the shallow muscle layer, <1/2 of the esophageal circumference, absence of metastasis, and patient’s refusal or unsuitable physical condition for salvage surgery. We assessed L-CR rate, incidence of AEs, clinical courses after PDT, 3-year overall survival (OS), progression free survival (PFS) and major PFS (mPFS) in which major disease progression after PDT which defined as disease progression requiring more invasive treatment than repeated endoscopic treatment and death from all causes were considered as events. We also assessed pre-PDT factors associated with L-CR. L-CR was defined as no apparent residual tumor, disappearance of post-PDT ulcer and confirmation of the scar formation, and absence of cancer cells in biopsy.

Results

108 patients (92 men; median age 74 years [range, 52-88 years]) were enrolled. Patients with pre-CRT/RT cT1/ T2/ T3/ T4/ unknown were 50/ 22/ 24/ 9/ 3. Those with residual lesion/ local recurrence/ unknown were 63/ 39/ 6. Patients with pre-PDT ycT1a/ T1b/ T2 were 6/ 85/ 17. Pre-PDT median lesion size was 20 mm (range, 4-50 mm). 60 patients achieved L-CR after PDT, 41 had L-nonCR, and 7 were not evaluable. L-CR rate of PDT was 58.8% (60/101). During median follow-up of 23 months (range, 1-90 months), 39 patients (36.1%) finally had no recurrence after PDT. 18 patients, including 8 with L-nonCR after PDT and 10 with local recurrence after achieving L-CR, underwent re-endoscopic treatments alone and remained disease-free afterward. The other 44 patients had major disease progression, and 15 received salvage surgery among them. As for the lesion characteristics associated with L-CR, the lesions with <1/2 circumference and with <20 mm in size were more likely to achieve L-CR than those with ≥1/2 circumference (64.4% vs. 16.7%, P=0.003) and with ≥20 mm (80.0% vs. 45.2%, P=0.001), respectively. The 3-year OS/ PFS/ mPFS of all patients were 78.1%/ 29.8%/ 48.1%. The 3-year OS of L-CR cases was better than that of L-nonCR cases (89.3% vs. 67.7%, P=0.003). There was no grade 3 < AEs. Non-cardiac chest pain (60.2%), skin phototoxicity (4.6%), and esophageal stricture requiring balloon dilatation (4.7%) occurred.

Conclusion

PDT with TS for local failure after CRT/RT for ESCC showed the preferable long-term outcomes. Moreover, achieving local control with PDT could improve prognosis of patients even with local failure after CRT/RT.

Introduction

Early detection of gastric neoplasms remains challenging, even with enhanced endoscopic imaging. Photodynamic endoscopic imaging (PEI) with 5-aminolevulinic acid (5-ALA) is a novel diagnostic approach that exploits tumor-selective fluorescence. After oral administration, 5-ALA is converted via the heme biosynthesis pathway to protoporphyrin IX (PpIX), which accumulates in neoplastic cells and emits red fluorescence under violet-blue excitation. We developed specialized endoscope prototypes (first-generation prototype using a 410 nm laser, second-generation prototype with an enhanced 410 nm laser, and third-generation prototype employing a high-intensity LED light source) to visualize PpIX fluorescence in the stomach. These successive devices improved image brightness and enabled more objective tumor detection.

Aims & Methods

In this exploratory study at Tottori University Hospital, 54 patients with 60 early-stage gastric lesions (gastric adenomas or early gastric carcinomas) were examined. Patients received oral 5-ALA (20 mg/kg) three hours before endoscopy. PEI was performed using the prototype systems (excitation at 410 nm and detection of ~635 nm red fluorescence). Lesions were identified by their red fluorescent contrast against surrounding mucosa. After the procedure, patients were protected from strong light for 24 hours to prevent photosensitivity. Key outcomes were the fluorescence detection rate of known tumors, discovery of any additional lesions, and safety (adverse events).

Results

The overall fluorescence detection rate was 85.0% (51/60 lesions). PEI newly identified 11 synchronous lesions in 8 patients (14.8%). Among lesions with fluorescence, histological types included tubular adenocarcinoma and adenoma (tub/sig/adenoma: 49/0/13). All signet ring cell carcinomas (5/5) were fluorescence-negative. Among 12 post-H. pylori eradication gastric cancers, 11 (91.6%) exhibited detectable fluorescence. Adverse events included transient elevations in liver enzymes (9 cases), mild hypotension (1 case), and low-grade fever (1 case), all resolving spontaneously. No phototoxic reactions were observed under light-shielding protocols.

Conclusion

Oral 5-ALA-mediated photodynamic endoscopic imaging is a feasible and effective technique for objective visualization of early-stage gastric tumors. This method provides bright tumor-specific fluorescence in gastric adenomas and differentiated early cancers, enhancing lesion contrast and aiding detection. Although diffuse-type (signet ring cell) carcinoma may evade fluorescence due to limited PpIX accumulation, the overall ability of 5-ALA-PEI to highlight tumors could significantly augment current endoscopic screening practices. This emerging molecular imaging approach offers endoscopists a valuable tool for identifying gastric neoplasms, and ongoing device refinements may further improve sensitivity for subtle lesions.

Disclosure

Hiroki Kurumi and Yuichiro Ikebuchi declare no conflict of interest. Hajime Isomoto received research funding from FUJIFILM Corporation.

Introduction

Photodynamic therapy (PDT) is one of the local salvage treatment options for local failure after chemoradiotherapy (CRT) or radiotherapy (RT) for esophageal squamous cell carcinoma (ESCC). PDT using talaporfin sodium, second-generation photosensitizer, has shown acceptably high local complete response (L-CR) rate for local failure after CRT or RT. PDT is usually performed via ordinary sized conventional endoscopes (CE), however, some patients with local failure that indicated for PDT have the esophageal stenosis due to CRT/RT or endoscopic resection. The ultra-thin endoscope (UTE) is sometimes used for such case unavoidably, but it might be difficult to illuminate stably due to less operability of UTE. Therefore, there are concern about decrease in the efficacy of PDT and increase in adverse events due to the inappropriate illumination for the lesion.

Aims & Methods

This study aimed to clarify the efficacy and safety of PDT using UTE (UTE-PDT) compared with PDT using CE (CE-PDT). This retrospective study enrolled the consecutive patients underwent PDT with talaporfin sodium using CE or UTE for histologically proven local failure of ESCC between October 2015 and June 2022 at the National Cancer Center Hospital East. The inclusion criteria of PDT in this study were as follow;
1) invasion depth limited within T2,
2) located at thoracic esophagus,
3) <5 cm in tumor size,
4) <3/4 of the esophageal circumference,
5) absence of lymph node or distant metastasis, and
6) patient’s refusal or unsuitable physical condition for salvage surgery.
We evaluated the L-CR rate and the incidence of adverse events in the UTE-PDT and the CE group. The L-CR was defined when absence of an obvious residual tumor, disappearance of post-PDT ulcer and scarring, and histological confirmation of absence of cancer cells by biopsy. We used L590ZW (Fujifilm Co., Tokyo, Japan) or GIF-H190 (Olympus Co., Tokyo, Japan) as CE, and used L580NW (Fujifilm Co., Tokyo, Japan) as UTE for PDT.

Results

Eight patients in the UTE-PDT group and 87 patients in the CE-PDT group were enrolled in this study. The tumor size (median, [range]) before PDT was 20mm [4-40mm] in the UTE group and 20mm [10-20mm] in the CE group, and the circumference of the lesion (1/2< /≤1/2) was 7/1 patients in the UTE group and 84/3 patients in the CE-PDT group. The number of the patients with recurrent/residual tumor/unknown in the appearance of local failure before PDT were 6/2/0 patients in the UTE-PDT group and 47/34/6 patients in the CE-PDT group, and those with T1/T2 in invasion depth before PDT were 7/1 patients in the UTE-PDT group and 74/13 patients in the CE-PDT group. In the UTE-PDT group, endoscopic resection was the most common cause of the esophageal stenosis (50.0%). Finally, the L-CR rate was 50.0% (4/8) in the UTE-PDT and 59.3% (48/81) in the CE-PDT group, excluding 6 cases with insufficient follow-up. As for adverse events in the UTE-PDT/CE-PDT group, esophageal pain in 12.5%/41.4%, skin phototoxicity in 0.0%/5.7%, and esophageal stricture with grade 2 after PDT in 12.5%/4.6% were observed, but all were grade 2 or less.

Conclusion

Comparing with PDT using CE, PDT using UTE for local failure after CRT/RT for ESCC are favorable and can be the promising therapeutic option for the patients without other treatment option. To improve the efficacy and reduce the esophageal stricture of UTE-PDT, several devices designed specifically for UTE should be further developed.