Attenuated polyethylene glycol immunogenicity and overcoming accelerated blood clearance of a fully PEGylated dendrimer.

Polyethylene glycol (PEG) is a popular biocompatible polymer and PEGylated nanoparticles passively accumulate in tumor tissues because of their enhanced permeability and retention effects. Recently, the anti-PEG immunity of PEGylated nanoparticles has become an issue that needs to be solved for their clinical applications. Dendrimers are highly branched and well-defined polymers with many terminal groups, which act as potent drug carriers. In this study, we examined the pharmacokinetics, biodistribution, anti-PEG immunity, and tumor accumulation of a fully PEGylated polyamidoamine (PAMAM) dendrimer after the first and second injections and compared them to those of a PEGylated liposome with the same lipid component as Doxil®. The PEGylated dendrimer showed greater blood circulation than that of the PEGylated liposome after the first and second injections in rats. In mice injected with the PEGylated dendrimer, much less anti-PEG immunoglobulin M (IgM) was generated than that in mice injected with the PEGylated liposome. The PEGylated dendrimer accumulated in the tumor after both the first and second injections. Our results indicated that the PEGylated dendrimer with a small size and high PEG density showed attenuated anti-PEG immunity and overcame the accelerated blood clearance phenomenon, which is useful for drug delivery systems for cancer treatment.

Synthesis and biological evaluation of EGFR binding peptides for near-infrared photoimmunotherapy.

Near-infrared photoimmunotherapy (NIR-PIT) is a new cancer treatment that involves photoimmunotherapy drug injection and NIR light exposure. In NIR-PIT, antibodies are commonly used as target-directed molecules carrying IRDye700DX (IR700). However, antibodies have disadvantages, such as high cost, complex development strategies, and poor tumor penetration. In contrast, peptides have lower production costs, can be easy to chemically synthesize and modify, and can also be used for tumor-targeting like antibodies. In this study, we developed a novel PIT drug using a peptide as the target-directed molecule. Epidermal growth factor receptor (EGFR) was selected as the target, and monovalent and bivalent EGFR-binding peptides were synthesized. The bivalent peptide showed sufficient binding to EGFR-positive cells, and a bivalent peptide-IR700 conjugate with a long linker induced morphological changes in EGFR-positive cells. Additionally, the drug significantly reduced cell viability in vitro in an NIR light-dose- and drug-concentration-dependent manner. These results indicate the feasibility of NIR-PIT in treating cancer using peptide-based drugs.

Advantages of enhanced recovery after surgery program in robot-assisted radical cystectomy.

Radical cystectomy is a gold-standard treatment for muscle-invasive bladder cancer. We recently introduced robot-assisted radical cystectomy (RARC) with perioperative enhanced recovery after surgery (ERAS). The medical records of patients with bladder cancer who underwent open radical cystectomy (ORC) or RARC/ERAS at NTT Medical Center Tokyo were retrospectively reviewed to compare the surgical outcomes, hospital stay, and medical costs between groups. Multidisciplinary full ERAS items were provided for the RARC/ERAS group. The median estimated blood losses in the ORC and RARC/ERAS groups were 650 and 100 mL, and the median operative times were 312 and 445 min, respectively. In addition, the median times to liquid food intake in these groups were 6 and 0 days, the median times to first flatus and first defecation were 2 and 1 day, and 3 and 1.5 days, respectively. The rates of postoperative ileus in the ORC and RARC/ERAS groups were 27.5% and 4.5%, and the median postoperative hospital stays was 26.5 and 12 days, respectively. Medical costs excluding surgery were significantly lower in the RARC/ERAS group. In conclusion, RARC/ERAS represents a safe treatment option for muscle-invasive bladder cancer with decreased perioperative complications and lower medical costs.

Plasma Cabozantinib Level Measurement in Patients with Renal Cell and Hepatocellular Carcinomas Using a Simple HPLC-UV Method Suitable for Clinical Application.

Cabozantinib, which is used to treat renal cell and hepatocellular carcinomas, is often associated with dose-dependent adverse events. Monitoring the levels of cabozantinib in the blood may maximize the therapeutic effect and prevent serious adverse events. In this study, we developed a high-performance liquid chromatography-ultraviolet (HPLC-UV) method of measuring plasma cabozantinib concentration. Human plasma samples (50 µL) were processed by simple deproteinization with acetonitrile, followed by chromatographic separation on a reversed-phase column with an isocratic mobile phase of 0.5% KH2PO4 (pH 4.5) and acetonitrile (43:57, v/v) at a flow rate of 1.0 mL/min, with a 250 nm ultraviolet detector. The calibration curve was linear over the concentration range (0.05-5 µg/mL) with a coefficient of determination of 0.99999. The accuracy of the assay ranged from -4.35% to 0.98%, and recovery was >96.04%. The measurement time was 9 min. These findings confirm the effectiveness of this HPLC-UV method for cabozantinib quantification in human plasma, which is sufficiently simple for use for monitoring patients in clinical settings.

In vivo imaging of acute physiological responses after treatment of cancer with near-infrared photoimmunotherapy.

PURPOSE: Near-infrared photoimmunotherapy (NIR-PIT) is a new cancer phototherapy using an antibody-photosensitizer conjugate (Ab-IR700). By NIR light irradiation, Ab-IR700 forms a water-insoluble aggregation on the plasma membrane of cancer cells, leading to lethal membrane damage of cancer cells with high selectivity. However, IR700 produces singlet oxygen, which induces non-selective inflammatory responses such as edema in normal tissues around the tumor. Understanding such treatment-emergent responses is important to minimize side effects and improve clinical outcomes. Thus, in this study, we evaluated physiological responses during NIR-PIT by magnetic resonance imaging (MRI) and positron emission tomography (PET). PROCEDURES: Ab-IR700 was intravenously injected into tumor-bearing mice with two tumors on the right and left sides of the dorsum. At 24 h after injection, a tumor was irradiated with NIR light. Edema formation was examined by T1/T2/diffusion-weighted MRI and inflammation was investigated by PET with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG). Because inflammation can increase vascular permeability via inflammatory mediators, we evaluated changes in oxygen levels in tumors using a hypoxia imaging probe, [18F]fluoromisonidazole ([18F]FMISO). RESULTS: The uptake of [18F]FDG in the irradiated tumor was significantly decreased compared to the control tumor, indicating the impairment of glucose metabolism induced by NIR-PIT. MRI and [18F]FDG-PET images showed that inflammatory edema with [18F]FDG accumulation was present in the surrounding normal tissues of the irradiated tumor. Furthermore, [18F]FMISO accumulation in the center of the irradiated tumor was relatively low, indicating the enhancement of oxygen supply due to increased vascular permeability. In contrast, high [18F]FMISO accumulation was observed in the peripheral region, indicating enhancement of hypoxia in the region. This could be because inflammatory edema was formed in the surrounding normal tissues, which blocked blood flow to the tumor. CONCLUSIONS: We successfully monitored inflammatory edema and changes in oxygen levels during NIR-PIT. Our findings on the acute physiological responses after light irradiation will help to develop effective measures to minimize the side effects in NIR-PIT.

Trends in surgical treatment for prostate cancer: Analysis of National Database Open Data in Japan.

We conducted a study to clarify the trends in surgical treatments for prostate cancer in Japan between 2014 and 2020 by analyzing the National Database (NDB) Open Data in Japan. Intriguingly, the number of patients over 70 years old who underwent robotic-assisted radical prostatectomy (RARP) nearly doubled from 2015 to 2019, while that in those 69 years old and younger remained almost constant during the same period. The increase in the number of patients over 70 years of age may reflect the fact that RARP can be safely applied to elderly patients. With the new development and spread of surgery-assisting robots, we can foresee a further increase in the number of RARPs performed for elderly patients in the future.

Low hemoglobin and PSA kinetics are prognostic factors of overall survival in metastatic castration-resistant prostate cancer patients.

The objective of this study was to identify the prognostic factors and to propose a new risk model in metastatic castration-resistant prostate cancer (mCRPC) patients. The clinical data were retrospectively obtained for 102 mCRPC patients who received cancer treatment between 2005 and 2018 at the University of Tokyo Hospital. We investigated clinical and pathological parameters, including prostate-specific antigen (PSA) kinetic profiles under androgen deprivation treatment, and identified predictors of overall survival (OS). The median age and PSA were 73 (Interquartile range [IQR], 68-79) years and 5.00 (IQR, 2.77-13.6) ng/ml. The median follow-up was 34 (IQR, 17-56) months. In univariate analysis, 'lymph node metastasis', 'Hemoglobin (Hb)', 'Time to nadir PSA (TNPSA)', 'PSA doubling time (PSADT)', 'Time to CRPC', and 'presence of pain' were prognostic factors. Multivariate analysis identified 'Hb < 11 g/dL', 'TNPSA < 7 months' and 'PSADT < 5 months' as independent prognostic factors of OS. The high-risk group (patients with two or three factors) demonstrated shorter OS (23 vs. 50 months) with an increased risk of death (HR = 2.997; 95% CI 1.632-5.506; P = 0.0004). The proposed risk stratification model may contribute to the prediction of survival and provide supportive information in treatment decision-making.

Subclassification of pT3 upper tract urothelial carcinoma: a multicenter retrospective study.

PURPOSE: The prognosis of patients with pT3 upper tract urothelial carcinoma (UTUC) varies. The current study aimed to further classify patients with pT3 UTUC into different survival outcome groups based on tumor location and site of invasion. METHODS: This retrospective study included 323 patients with pT3 UTUC who underwent nephroureterectomy at 11 hospitals in Japan. Histological and clinical data were obtained via a chart review. Univariate and multivariate Cox proportional hazards analyses showed the effect of different variables on recurrence-free survival (RFS), cancer-specific survival (CSS), and overall survival (OS). RESULTS: The median age of the patients was 72 years. Patients with pT3 UTUCs were divided into two groups: those with renal parenchymal invasion only (pT3a, n = 95) and those with peripelvic or periureteral fat invasion (pT3b, n = 228). pT3b UTUC was significantly associated with hydronephrosis, low preoperative estimated glomerular filtration rate (eGFR), histological nodal metastasis, nuclear grade 3, lymphovascular invasion (LVI), carcinoma in situ, and positive surgical margin. Based on the univariate analyses, patients with pT3b UTUC had a significantly lower 5-year RFS (42.4% vs. 70.1%, p < 0.0001), 5-year CSS (54.3% vs. 80.0%, p = 0.0002), and 5-year OS (47.8% vs. 76.8%, p < 0.0001) than those with pT3a UTUC. According to the multivariate analyses, nodal metastasis, LVI, adjuvant chemotherapy, preoperative eGFR, nuclear grade (RFS only), surgical margin (RFS only), and Charlson comorbidity index (OS only), but not pT3b stage, were associated with survival. CONCLUSION: Compared with pT3a UTUC, pT3b UTUC was significantly associated with worse histological features, consequently resulting in unsatisfactory survival outcomes.

Prevalence of Human Papillomavirus Types 16/18 and Effect of Vaccination among Japanese Female General Citizens in the Vaccine Crisis Era.

The Japanese government withdrew its recommendation for human papillomavirus (HPV) vaccination in June 2013 and resumed it in April 2022. This period is known as the vaccine crisis in Japan. This study aimed to elucidate the prevalence and genotype distribution of HPV among Japanese female citizens, and the effect of vaccination against HPV-16/18 in the era of the vaccine crisis. We recruited Japanese female citizens and asked them to provide self-collected samples from the vaginal wall using cotton swabs for HPV genotyping. Furthermore, we collected the participants' characteristics, including lifestyle and experience of vaccination against HPV, to determine the significant association with HPV infection. HPV-16/18 positivity was found in 5.6% (115/2044) of participants. The highest vaccination rate was observed in the age group of 20-24 years (60.6%), whereas the lowest HPV-16/18 positivity was observed in the age group of 45-49 years (2.8%), followed by the age group of 20-24 years (4.0%). Experience with HPV vaccination significantly reduced the risk of HPV-16/18 infection (adjusted odds ratio, 0.047; 95% confidence interval, 0.011-0.196). Vaccinated women were much less likely to be infected by HPV-16/18, regardless of the HPV vaccine type or the vaccination dose.

Cumulative Incidence and Clinical Risk Factors of Radiation Cystitis after Radiotherapy for Prostate Cancer.

OBJECTIVES: This study aimed to evaluate the cumulative incidence of overall and severe radiation cystitis following external beam radiation therapy for prostate cancer and investigate the clinical factors predictive of radiation cystitis. METHODS: This retrospective study comprised 246 patients who received external beam radiation therapy for localized or locally advanced prostate cancer between 2013 and 2016 in our institution. Of these, 189 received primary radiation therapy and 57 received adjuvant/salvage radiation therapy. Radiation cystitis was recorded using the Common Terminology Criteria for Adverse Events version 5.0 definition, and severe radiation cystitis was defined as grade 3 or higher. All medical records were reviewed to calculate the cumulative incidence of radiation cystitis. Univariate and multivariate Cox regression analyses were used to evaluate its association with clinicopathologic features. RESULTS: The median follow-up period after radiation therapy was 56 months (range 5-81). The 5-year cumulative incidence of radiation cystitis and severe radiation cystitis was 16.2% and 3.0%, respectively. Multivariate analyses identified radiation therapy in the adjuvant/salvage setting was the sole risk factor associated with the development of radiation cystitis (hazard ratio: 2.75, p = 0.02). CONCLUSIONS: Radiation therapy in the post-prostatectomy setting was associated with increased risk of radiation cystitis compared with radiotherapy as the primary treatment.

Clinical features and treatment outcomes of Fournier's gangrene in a single tertiary emergency hospital: Simplified Fournier's Gangrene Severity Index score is a predictor for death.

To assess the predictive reliability of the Simplified Fournier's Gangrene Severity Index Score (SFGSI) for mortality in Japanese patients with Fournier's gangrene (FG), we compared the clinical features and outcomes of a patient sample with the SFGSI. The medical records of 36 patients diagnosed with FG at our hospital between October 2007 and September 2022 were reviewed retrospectively. Clinical and laboratory variables, including SFGSI, were evaluated and predictive factors for fatality were investigated using multivariate logistic regression analysis. The median age and body mass index were 65 and 24.2, respectively. Eight patients had cooccurring chronic kidney disease and 23 had diabetes. None were taking sodium-glucose co-transporter-2 (SGLT-2) inhibitors. The causative organisms were diverse, and no specific trends in causative organisms were observed. 26 patients underwent debridement of necrotic tissue including eight colostomies, two orchiectomies, and one cystectomy. Multivariate logistic regression analysis revealed that SFGSI alone was an independent predictor of case fatality, with an odds ratio of 20.167 (95% CI: 1.66-245.53). In conclusion, the fatality rate was 19.4%, which was comparable to that reported in other studies. The SFGSI was an independent predictor of mortality in this study.

Preservation of pelvic floor muscles contributes to early continence recovery after robot-assisted radical prostatectomy.

PURPOSE: Postoperative recovery of urinary continence has a great impact on quality of life for patients undergoing robot-assisted radical prostatectomy (RARP). A variety of surgical techniques including reconstruction of the periurethral structure have been introduced, and yet there are no effective methods that promote early urinary continence recovery after surgery. We hypothesized that the preservation of pelvic floor muscle structure could be responsible for early recovery of urinary continence after surgery. METHODS: A total of 94 consecutive patients who underwent RARP at our hospital were enrolled in this study. Operative video records were reviewed and the severity of pelvic floor muscle injury was classified according to the scoring system that we devised in this study. Briefly, damage of pelvic floor muscles was classified into 4 categories; intact, fascial injury, unilateral muscle injury, and bilateral muscle injury. The volume of urinary incontinence was measured for 2 days after removal of the urethral catheter, and the incontinence ratio (amount of incontinence/total volume of urine per day) was calculated. Predictive factors for immediate incontinence after catheter removal were identified by multivariate regression analysis. RESULTS: The severity of puboperineal muscle injury was significantly associated with the early incontinence ratio after catheter removal (p < 0.001). Age at surgery and severity of puboperineal muscle injury were independent predictors for early incontinence after catheter removal. CONCLUSION: Preservation of the pelvic floor muscle, particularly the puboperineal muscle is an important factor for early continence recovery after RARP.

Time to castration resistance is a novel prognostic factor of cancer-specific survival in patients with nonmetastatic castration-resistant prostate cancer.

We aimed to identify prognostic factors of cancer-specific survival (CSS) in non-metastatic castration-resistant prostate cancer (M0CRPC) patients. The final analysis of this retrospective cohort included 82 patients who were diagnosed as M0CRPC between 1998 and 2018 at the University of Tokyo Hospital. CRPC was defined as prostate-specific antigen (PSA) progression (increased PSA ≥ 25% and ≥ 2 ng/mL above the nadir or detection of a metastatic lesion). The median value of age and PSA at the time of CRPC were 76 (range 55-94) years and 2.84 (range 2.04-22.5) ng/mL, respectively. The median follow-up time from CRPC diagnosis was 38 (range 3-188) months. The prognostic factors of CSS were 'PSA doubling time (PSADT) ≤ 3 months', 'time to CRPC diagnosis from the start of androgen deprivation therapy (TTCRPC) ≤ 12 months', of which TTCRPC was a novel risk factor of CSS. In the multivariate analysis, 'PSADT ≤ 3 months' and TTCRPC ≤ 12 months' remained as statistically significant predictors of CSS. Novel risk stratification was developed based on the number of these risk factors. The high-risk group showed a hazard ratio of 4.416 (95% confidence interval 1.701-11.47, C-index = 0.727).

PD1 blockade alters cell-cycle distribution and affects 3'-deoxy-3'-[18F]fluorothymidine uptake in a mouse CT26 tumor model.

OBJECTIVE: We previously reported that alterations of the tumor microenvironment (TME) by programmed death receptor-1 (PD1) blockade affected tumor glucose metabolism and tumor 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) uptake. In cancer cells, high glycolysis allows cells to sustain rapid proliferation since glycolysis is closely related to the proliferation of cancer cells. Therefore, imaging of cellular proliferation may provide more detail of TME alterations. In this study, we investigated how TME alterations by PD1 blockade affects the uptake of 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT), which is a 18F-radiolabeled thymidine derivative and is taken up by proliferating cells. METHODS: Mice inoculated with murine colon carcinoma CT26 cells were intraperitoneally administered an anti-PD1 antibody on Day 0, when the tumor volume exceeded 50 mm3, and Day 5. [18F]FLT-PET imaging was performed pre-treatment (Day 0) and post treatment (Day 7). Tumor infiltrating lymphocytes (TILs) were identified by flow cytometry. [18F]FLT accumulation and localization in tumor tissue was evaluated by autoradiography and immunohistochemistry. The cell-cycle distribution of tumors and CT26 cells exposed to cytokines (interleukin-2, interferon [INF]-γ, and tumor necrosis factor [TNF]-α) was analyzed by flow cytometry. RESULTS: PD1 blockade increased CD8+ and CD4+ T cells in tumor tissue and significantly suppressed tumor proliferation; however, tumor [18F]FLT uptake remained unchanged. Autoradiography and immunohistochemistry showed that [18F]FLT was mainly taken up by cancer cells, but not TILs. Flow cytometric analysis demonstrated that the population of cells in G2/M phase increased after PD1 blockade. Moreover, INF-γ and TNF-α significantly increased cells in G2/M phase in vitro. CONCLUSION: PD1 blockade-induced alteration of the TME increased CT26 tumor cells in the G2/M phase, which have high thymidine kinase 1 activity. Therefore, [18F]FLT is taken up by tumor cells even if tumor proliferation is suppressed. This observation may be useful for evaluating the response to immunotherapy.

Correction: Takakura et al. In Vitro and In Vivo Cell Uptake of a Cell-Penetrating Peptide Conjugated with Fluorescent Dyes Having Different Chemical Properties. Cancers 2021, 13, 2245.

There was an error in the description in the original publication, and it contained information that should not have been disclosed [...].

Reduction of tumor hypoxia by anti-PD-1 therapy assessed using pimonidazole and [18F]FMISO.

INTRODUCTION: Hypoxia is common in solid tumors and creates an immunosuppressive environment that leads to resistance to immunotherapy, such as an anti-programmed death receptor-1 (PD-1) therapy. It has been suggested that anti-PD-1 therapy may reduce tumor hypoxia by remodeling the tumor vasculature; however, it is unclear how anti-PD-1 therapy reduces hypoxia over time. Therefore, we investigated the relationship between hypoxia and immune activation by anti-PD-1 therapy in murine cancer models. METHODS: Anti-PD-1 antibody was injected to CT26- and MC38-tumor-bearing mice on days 0 and 5. Tumor hypoxia was non-invasively evaluated using positron emission tomography (PET) with [18F]fluoromisonidazole ([18F]FMISO) on days 3 and 7. Histological analysis was conducted to investigate the infiltration of immune cells in [18F]FMISO-accumulated hypoxic area. In addition, the immune cell population in tumors and the percentages of cancer and immune cells under hypoxic conditions were analyzed at single-cell level using flow cytometry. RESULTS: Flow cytometric analysis of CT26 tumors on day 3 showed that anti-PD-1 therapy reduced hypoxia without inhibition of tumor growth. In addition, the infiltration of CD8+ T cells was increased in treated tumors. In contrast to CT26 tumors, the percentage of hypoxic cells in MC38 tumors did not change on days 3 and 7, and there was minimal immune activation induced by anti-PD-1 antibody. Changes in hypoxia in CT26 tumors were not detected by [18F]FMISO-PET, but autoradiogram showed that [18F]FMISO accumulated in immunosuppressed areas, where the infiltration of immune cells was relatively low. CONCLUSION: Reduction of hypoxia was induced in CT26 tumor, in which adequate immune response to anti-PD-1 therapy was exhibited, at an early time point before suppression of tumor growth. Our findings suggest that anti-PD-1 therapy can create a tumor microenvironment that facilitates immune activation by reducing hypoxia.

Eribulin improves tumor oxygenation demonstrated by 18F-DiFA hypoxia imaging, leading to radio-sensitization in human cancer xenograft models.

PURPOSE: Eribulin, an inhibitor of microtubule dynamics, is known to show antitumor effects through its remodeling activity in the tumor vasculature. However, the extent to which the improvement of tumor hypoxia by eribulin affects radio-sensitivity remains unclear. We utilized 1-(2,2-dihydroxymethyl-3-18F-fluoropropyl)-2-nitroimidazole (18F-DiFA), a new PET probe for hypoxia, to investigate the effects of eribulin on tumor hypoxia and evaluate the radio-sensitivity during eribulin treatment. METHODS: Mice bearing human breast cancer MDA-MB-231 cells or human lung cancer NCI-H1975 cells were administered a single dose of eribulin. After administration, mice were injected with 18F-DiFA and pimonidazole, and tumor hypoxia regions were analyzed. For the group that received combined treatment with radiation, 18F-DiFA PET/CT imaging was performed before tumors were locally X-irradiated. Tumor size was measured every other day after irradiation. RESULTS: Eribulin significantly reduced 18F-DiFA accumulation levels in a dose-dependent manner. Furthermore, the reduction in 18F-DiFA accumulation levels by eribulin was most significant 7 days after treatment. These results were also supported by reduction of the pimonidazole-positive hypoxic region. The combined treatment showed significant retardation of tumor growth in comparison with the control, radiation-alone, and drug-alone groups. Importantly, tumor growth after irradiation was inversely correlated with 18F-DiFA accumulation. CONCLUSION: These results demonstrated that 18F-DiFA PET/CT clearly detected eribulin-induced tumor oxygenation and that eribulin efficiently enhanced the antitumor activity of radiation by improving tumor oxygenation.

Early recurrence of bladder cancer in the colon after robot-assisted radical cystectomy: Disappearance following dose-dense methotrexate, vinblastine, doxorubicin and cisplatin treatment.

INTRODUCTION: The popularity of robot-assisted radical cystectomy over open radical cystectomy has been increasing because the former, a minimally invasive surgery, contributes to earlier recovery and shorter hospitalization. However, atypical recurrences may be more frequent after robot-assisted radical cystectomy than after open radical cystectomy. We report a case of an atypical early recurrence of bladder cancer including the descending colon. CASE PRESENTATION: A 70-year-old Japanese man underwent robot-assisted radical cystectomy for muscle-invasive bladder cancer. Four months later, he was hospitalized for severe anemia (hemoglobin, 5.1 g/dL). Colonoscopy revealed a 4-cm submucosal oozing tumor in the descending colon. Computed tomography revealed multiple recurrent lesions including recurrence in the descending colon, all of which disappeared completely after chemotherapy with six cycles of dose-dense methotrexate, vinblastine, doxorubicin, and cisplatin. CONCLUSION: We encountered a rare case of an atypical recurrence of bladder cancer in the colon after robot-assisted radical cystectomy.

Comparison of low-molecular-weight ligand and whole antibody in prostate-specific membrane antigen targeted near-infrared photoimmunotherapy.

Near-infrared photoimmunotherapy (NIR-PIT) is a cancer phototherapy that uses antibody-IR700 conjugate (Ab-IR700) and NIR light. Ab-IR700 forms aggregates on the plasma membranes of targeted cancer cells after light exposure, inducing lethal physical damage within the membrane. Low-molecular-weight (LMW) ligands are candidate targeting moieties instead of antibodies, but whether LMW-IR700 conjugates induce cell death by aggregation, the same mechanism as Ab-IR700, is unknown. Thus, we investigated differences in cytotoxicity and mechanisms between LMW-IR700 and Ab-IR700 targeting prostate-specific membrane antigen (PSMA). Both conjugates decreased cell viability to the same degree after light irradiation, but different morphological changes were observed in PSMA-positive LNCaP cells by microscopy. Cell swelling and bleb formation were induced by Ab-IR700, but only swelling was observed in cells treated with LMW-IR700, suggesting the cells were damaged via different cytotoxic mechanisms. However, LMW-IR700 induced bleb formation, a hallmark of NIR-PIT with Ab-IR700, when singlet oxygen was quenched or LMW-IR700 was localized only on the plasma membrane. Moreover, the water-soluble axial ligands of LMW-IR700 were cleaved, consistent with previous reports on Ab-IR700. Thus, the main cytotoxic mechanisms of Ab-IR700 and LMW-IR700 differ, although LMW-IR700 on the plasma membrane can cause aggregation-mediated cytotoxicity as well as Ab-IR700.