Guidelines for permanent iodine-125 seed interstitial brachytherapy for pancreatic cancer (2023 edition): The Chinese expert consensus workshop report.

ABSTRACT: The incidence of pancreatic cancer is increasing worldwide. Approximately, 60% of patients with pancreatic cancer have distant metastases at the time of diagnosis, of which only 10% can be removed using standard resection. Further, patients derive limited benefits from chemotherapy or radiotherapy. As such, alternative methods to achieve local control have emerged, including permanent iodine-125 seed interstitial brachytherapy. In 2023, the Chinese College of Interventionalists, affiliated with the Chinese Medical Doctor Association, organized a group of multi-disciplinary experts to compose guidelines for this treatment modality. The aim of this conference was to standardize the procedure for permanent iodine-125 seed interstitial brachytherapy, including indications, contraindications, pre-procedural preparation, procedural operations, complications, efficacy evaluation, and follow-up.

Thymosin ß4 and Actin: Binding Modes, Biological Functions and Clinical Applications.

Thymosin ß4 (Tß4) is the ß-thymosin (Tßs) with the highest expression level in human cells; it makes up roughly 70-80% of all Tßs in the human body. Combining the mechanism and activity studies of Tß4 in recent years, we provide an overview of the subtle molecular mechanism, pharmacological action, and clinical applications of Tß4. As a G-actin isolator, Tß4 inhibits the polymerization of G-actin by binding to the matching site of G-actin in a 1:1 ratio through conformational and spatial effects. Tß4 can control the threshold concentration of G-actin in the cytoplasm, influence the balance of depolymerization and polymerization of F-actin (also called Tread Milling of F-actin), and subsequently affect cell's various physiological activities, especially motility, development and differentiation. Based on this, Tß4 is known to have a wide range of effects, including regulation of inflammation and tumor metastasis, promotion of angiogenesis, wound healing, regeneration of hair follicles, promotion of the development of the nervous system, and improving bone formation and tooth growth. Tß4 therefore has extensive medicinal applications in many fields, and serves to preserve the kidney, liver, heart, brain, intestine, and other organs, as well as hair loss, skin trauma, cornea repairing, and other conditions. In this review, we focus on the mechanism of action and clinical application of Tß4 for its main biological functions.

Discovery of Anti-PD-L1 Human Domain Antibodies for Cancer Immunotherapy.

Immunotherapy using monoclonal antibodies targeting the PD-1/PD-L1 interaction has shown enormous success for various cancers. Despite their encouraging results in clinics, antibody-based checkpoint inhibitors have several limitations, such as poor tumor penetration. To address these limitations of monoclonal antibodies, there is a growing interest in developing low-molecular-weight checkpoint inhibitors, such as antibody fragments. Several antibody fragments targeting PD-1/PD-L1 were recently discovered using phage libraries from camel or alpaca. However, animal-derived antibody fragments may elicit unwanted immune responses, which limit their therapeutic applications. For the first time, we used a human domain antibody phage library and discovered anti-human PD-L1 human single-domain antibodies (dAbs) that block the PD-1/PD-L1 interaction. Among them, the CLV3 dAb shows the highest affinity to PD-L1. The CLV3 dAb also exhibits the highest blocking efficacy of the PD-1/PD-L1 interaction. Moreover, the CLV3 dAb significantly inhibits tumor growth in mice implanted with CT26 colon carcinoma cells. These results suggest that CLV3 dAb can be potentially used as an anti-PD-L1 inhibitor for cancer immunotherapy.

Hypoxia-induced Tie1 drives stemness and cisplatin resistance in non-small cell lung carcinoma cells.

BACKGROUND: Drug resistance and metastasis involving hypoxic tumor environments and persistent stem cell populations are detrimental to the survival of patients with non-small cell lung carcinoma (NSCLC). Tie1 is upregulated in hypoxia and is believed to counteract the effectiveness of platinum agents by promoting the stemness properties in cells. We have investigated the association of Tie1 with HIF-1α and cisplatin resistance in NSCLC cell lines. METHODS: The expression of Tie1 in a pulmonary microvascular endothelial cell line (HPMEC) and NSCLC cell lines was detected using qRT-PCR and western blotting. The effect of Tie1 on cell stemness and migration was examined by sphere-forming and transwell assays in NSCLC cells with Tie1 silenced. The regulation of Tie1 by HIF-1α was evaluated by a dual-luciferase reporter assay and chromatin immunoprecipitation. RESULTS: We found that hypoxia could induce stemness and cisplatin resistance in vitro. Tie1 was expressed at low levels in NSCLC cells when compared with human pulmonary microvascular endothelial cells, however, its expression was increased by hypoxia. Additionally, Tie1 knockdown could reduce stemness properties and increase sensitivity to cisplatin in vitro and in a xenograft mouse model. The promoter of Tie1 contains two predicted hypoxia-response elements (HREs). We mutated both HRE sites and conducted chromatin immune-precipitation and promoter luciferase reporter assays and were able to conclude that the induction of Tie1 by hypoxia was HIF-1α-dependent. CONCLUSIONS: Our findings indicated that Tie1 is upregulated in a hypoxic environment by HIF-1α and contributes to tumorigenesis and cisplatin resistance through the promotion of stemness in NSCLC cells.

A retrospective study of the use of percutaneous vesselplasty for pathological vertebral compression fractures.

Objective and Aims: To assess percutaneous vesselplasty's safety and efficacy in treating pathological vertebral compression fractures (VCFs). Subjects and Methods: This retrospective review covered nine patients with an equal number of symptomatic pathological VCFs treated with vesselplasty. The study assessed the patients' pain scores, subjective conditions, imaging guidance, and incidence of procedure-related complications. Results: The VCFs were at the T4 and L5 spine regions. The procedure success rate was 100%. In 88.89% (8/9) of the examined cases, there was a posterior vertebral body or pedicle involvement or both. Two patients with high thoracic VCFs underwent combined computed tomography and mobile C-arm fluoroscopy guidance. The other patients underwent digital subtraction angiography guidance. The average visual analog scale (VAS) score and the Oswestry Disability Index (ODI) before the treatment were 7.78 ± 0.67 standard deviation (SD) and 75.45 ± 7.55, respectively. The average VAS score and ODI 3 months after the treatment were 2.67 ± 0.50 (SD) and 32.45 ± 6.19 (P < 0.001), respectively. There were no recorded cases of symptomatic cement leakage or other operation-associated complications. Conclusions: Percutaneous vesselplasty appears to be a safe and effective minimally invasive local treatment for pathological VCFs. This approach may offer benefits in improving pain, mobility, and function and minimizing the bone cement leakage rate while providing a safe and effective alternative treatment for pathological VCFs.

Robo1-specific CAR-NK Immunotherapy Enhances Efficacy of 125I Seed Brachytherapy in an Orthotopic Mouse Model of Human Pancreatic Carcinoma.

BACKGROUND/AIM: The aim of the current study was to investigate the synergistic efficacy of Robo1 bichimeric antigen receptor-natural killer cell (BiCAR-NK) immunotherapy and 125I seed brachytherapy in an orthotopic pancreatic cancer mouse model. MATERIALS AND METHODS: The orthotopic pancreatic tumor model was established with human pancreatic cancer BxPC-3 cells expressing red fluorescent protein. The mice were treated with 125I seed implantation alone or the combination of 125I seeds with Robo1-specific CAR-NK cells. To assess tumor inhibition, in vivo fluorescence imaging was conducted. 7 Tesla magnetic resonance (7T-MR) scanning was applied to measure the changes in the metabolic profiles of tumor tissues. RESULTS: Tumor size was significantly reduced in the 125I and 125I +CAR-NK treated group compared to the untreated group (p<0.05). The 125I seed +CAR-NK treated group showed significantly higher tumor reduction than 125I seed treatment alone (p<0.05). T1 diffusion weighted imaging (T1DWI) sequence showed that the tumors of the 125I +BiCAR-NK treated group had a significantly higher grey scale value than the tumors from the untreated control and the group treated with 125I seed alone (p<0.05). CONCLUSION: Robo1 specific CAR-NK immunotherapy enhances efficacy of 125I seed brachytherapy in an orthotopic pancreatic cancer mouse model.

The safety and efficacy of interstitial 125I seed implantation brachytherapy for metastatic epidural spinal cord compression.

OBJECTIVE: The objective of this study is to investigate the safety and efficacy of 125I seed interstitial implantation brachytherapy for metastatic epidural spinal cord compression (MESCC) as well as the life quality of patients. MATERIALS AND METHODS: From April 2009 to May 2015, 28 patients who met the eligibility criteria were retrospectively reviewed. The number of implanted 125I seeds ranged from 7 to 62, with appropriate activity of 0.5-0.8 mCi. The postplan showed that the matched peripheral dose (MPD) of tumors was 80-140 Gy. The duration of follow-up ranged from 1 to 32 months with a median of 18 months. Visual analog scale (VAS), Karnofsky Performance Scale (KPS), and motor performance were evaluated before and after treatment. RESULTS: Seed implantation was well tolerated by all patients. Pain was obviously alleviated in all patients. VAS score of patients was significantly decreased from 4.89 ± 1.52 before treatment to 1.61 ± 1.20 after treatment, and KPS score was significantly increased from 73.93 ± 12.27 to 86.76 ± 10.90 (P < 0.05). The local control rates of 1, 2, and 3 years were 77%, 34%, and 14%, respectively, with a median of 19 months (7-32 months). The survival rates of 1, 2, and 3 years were 81%, 54%, and 14%, respectively, with a median of 25 months. Seven (100%) nonwalking patients regained motor ability. No myelopathy or other neurologic sequelae were encountered. CONCLUSION: Interstitial 125I seed implantation brachytherapy may be a promising local therapy, which was an alternative and palliative way for treating MESCC.

Preliminary application of 3D-printed coplanar template for iodine-125 seed implantation therapy in patients with advanced pancreatic cancer.

AIM: To evaluate a 3D-printed coplanar template for iodine-125 seed implantation therapy in patients with pancreatic cancer. METHODS: A retrospective analysis of our database was performed, and a total of 25 patients with pancreatic cancer who underwent iodine-125 seed implantation between January 2014 and November 2017 were analyzed. Of these, 12 implantations were assisted by a 3D-printed coplanar template (group A), and 13 implantations performed freehand were selected as a control group (group B). A 3D coplanar template was designed and printed according to a preoperative CT scan and treatment planning system. The iodine-125 seeds were then implanted using the template as a guide. Dosimetric verification was performed after implantation. Pre- and postoperative D90, V100, and V150 were calculated. The success rate of iodine-125 seed implantation, dosimetric parameters, and complications were analyzed and compared between the two groups. RESULTS: Iodine-125 seed implantation was successfully performed in both groups. In group A, the median pre- and postoperative D90 values were 155.32 ± 8.05 Gy and 154.82 ± 16.43 Gy, respectively; the difference between these values was minimal and not statistically significant (P > 0.05). Postoperative V100 and V150 were 91.05% ± 4.06% and 64.54% ± 13.40%, respectively, which met the treatment requirement. A better dosimetric parameter was observed in group A than in group B, and the difference was statistically significant (V100: 91.05% ± 4.06% vs 72.91% ± 13.78%, P < 0.05). No major procedure-related complications were observed in either group. For group A, mild hemorrhage was observed in 1 patient with a peritoneal local hematoma due to mesenteric vein damage from the iodine-125 seed implantation needle. The hematoma resolved spontaneously without treatment. Postoperative blood amylase levels remained within the normal range for all patients. CONCLUSION: A 3D-printed coplanar template appears to be a safe and effective iodine-125 seed implantation guidance tool to improve implantation accuracy and optimize dosimetric distribution.

Percutaneous intraductal radiofrequency ablation for treatment of biliary stent occlusion: A preliminary result.

AIM: To assess the feasibility and effectiveness of a novel application of percutaneous intraductal radiofrequency (RF) for the treatment of biliary stent obstruction. METHODS: We specifically report a retrospective study presenting the results of percutaneous intraductal RF in patients with biliary stent occlusion. A total of 43 cases involving biliary stent obstruction were treated by placing an EndoHPB catheter and percutaneous intraductal RF was performed to clean stents. The stent patency was evaluated by cholangiography and follow-up by contrast enhanced computed tomography or ultrasound after the removal of the drainage catheter. RESULTS: Following the procedures, of the 43 patients, 40 survived and 3 died with a median survival of 80.5 (range: 30-243) d. One patient was lost to follow-up. One patient had the stent patent at the time of last follow-up. Two patients with stent blockage at 35 d and 44 d after procedure underwent percutaneous transhepatic drain insertion only. The levels of bilirubin before and after the procedure were 128 ± 65 µmol/L and 63 ± 29 µmol/L, respectively. There were no related complications (haemorrhage, bile duct perforation, bile leak or pancreatitis) and all patients' stent patency was confirmed by cholangiography after the procedure, with a median patency time of 107 (range: 12-180) d. CONCLUSION: This preliminary clinical study demonstrated that percutaneous intraductal RF is safe and effective for the treatment of biliary stent obstruction, increasing the duration of stent patency, although randomized controlled trials are needed to confirm the effectiveness of this approach.

Discovery of PSMA-specific peptide ligands for targeted drug delivery.

Prostate-specific membrane antigen (PSMA) has been widely used as a biomarker and targeting receptor for prostate cancer therapy because of its overexpression in most prostate cancer cells. In this study, a novel combinatorial phage biopanning procedure was developed to discover PSMA-specific peptides that can be potentially used as ligands for targeted drug delivery to prostate cancer cells. Five rounds of biopanning against recombinant human PSMA extracellular domain (ECD), PSMA-positive LNCaP cells, and LNCaP xenografts in nude mice were conducted. Various affinity assays were conducted to identify high-affinity peptides for PSMA ECD and PSMA-positive prostate cancer cells. Among them, the GTI peptide shows the highest affinity as well as specificity to PSMA in prostate cancer cells. The apparent Kd values of the GTI peptide to PSMA-positive LNCaP and C4-2 cells are 8.22µM and 8.91µM, respectively. The GTI peptide can specifically deliver the proapoptotic peptide D(KLAKLAK)2 to LNCaP cells to induce cell death. In the biodistribution study, the GTI peptide shows the highest uptake in C4-2 xenografts, while its uptake in other major organs, such as the liver and spleen, are either low or negligible. Compared to its scrambled control (random permutation of the GTI peptide), the GTI peptide exhibits higher and more specific uptake in C4-2 xenografts. All the results suggest that the GTI peptide is a potentially promising ligand for PSMA-targeted drug delivery for prostate cancer therapy.

A comparison of the biological effects of 125I seeds continuous low-dose-rate radiation and 60Co high-dose-rate gamma radiation on non-small cell lung cancer cells.

OBJECTIVES: To compare the biological effects of 125I seeds continuous low-dose-rate (CLDR) radiation and 60Co γ-ray high-dose-rate (HDR) radiation on non-small cell lung cancer (NSCLC) cells. MATERIALS AND METHODS: A549, H1299 and BEAS-2B cells were exposed to 125I seeds CLDR radiation or 60Co γ-ray HDR radiation. The survival fraction was determined using a colony-forming assay. The cell cycle progression and apoptosis were detected by flow cytometry (FCM). The expression of the apoptosis-related proteins caspase-3, cleaved-caspase-3, PARP, cleaved-PARP, BAX and Bcl-2 were detected by western blot assay. RESULTS: After irradiation with 125I seeds CLDR radiation, there was a lower survival fraction, more pronounced cell cycle arrest (G1 arrest and G2/M arrest in A549 and H1299 cells, respectively) and a higher apoptotic ratio for A549 and H1299 cells than after 60Co γ-ray HDR radiation. Moreover, western blot assays revealed that 125I seeds CLDR radiation remarkably up-regulated the expression of Bax, cleaved-caspase-3 and cleaved-PARP proteins and down-regulated the expression of Bcl-2 proteins in A549 and H1299 cells compared with 60Co γ-ray HDR radiation. However, there was little change in the apoptotic ratio and expression of apoptosis-related proteins in normal BEAS-2B cells receiving the same treatment. CONCLUSIONS: 125I seeds CLDR radiation led to remarkable growth inhibition of A549 and H1299 cells compared with 60Co HDR γ-ray radiation; A549 cells were the most sensitive to radiation, followed by H1299 cells. In contrast, normal BEAS-2B cells were relatively radio-resistant. The imbalance of the Bcl-2/Bax ratio and the activation of caspase-3 and PARP proteins might play a key role in the anti-proliferative effects induced by 125I seeds CLDR radiation, although other possibilities have not been excluded and will be investigated in future studies.

Nitinol stents loaded with a high dose of antitumor 5-fluorouracil or paclitaxel: esophageal tissue responses in a porcine model.

BACKGROUND: A poor prognosis associated with esophageal cancer leads to surgical resection not suitable for most patients. Nitinol stents loaded with 50% 5-fluorouracil (5-FU) or paclitaxel (PTX), functioning both as a stent and local chemotherapy, could provide a new therapy modality for these patients. OBJECTIVE: To investigate esophageal tissue responses to nitinol stents loaded with 50% 5-FU or PTX implanted in the esophagus of healthy pigs. DESIGN: Twenty-three healthy Bama mini-pigs were randomly divided into 4 groups for stent implantation: group A (PTX stent, n = 13), group B (5-FU stent, n = 8), group C (blank film-covered stent, n = 1), and group D (bare stent, n = 1). Tissue responses were observed by endoscopy or pathologic analyses, and 5-FU or PTX concentrations were measured in the esophagus at the stent implantation site at different time points. SETTING: Animal laboratory. INTERVENTIONS: Endoscopic placement of esophagus stent. MAIN OUTCOME MEASUREMENTS: Endoscopic examination, histology, and drug concentration analysis. RESULTS: In general, the esophageal tissue responses varied according to different parts of 5-FU or PTX stent (middle part [drug-containing part] and bare ends [drug-free part]). Severe tissue responses at the bare ends of the stent included inflammation, ulceration, and granulation. However, the tissue responses were greatly reduced in the middle part of the stent. The drug concentrations in the esophagus that had contact with the 5-FU stent or PTX stent were very high, especially for the first period after implantation, which did not cause obvious tissue damage. LIMITATION: Some subjects had incomplete follow-up because of unexpected deaths and stent migration. CONCLUSION: The nitinol stents loaded with 50% 5-FU or PTX did not cause severe esophageal tissue responses, although there was a large concentration of the drug in these tissues.

Biological effects of low-dose-rate irradiation of pancreatic carcinoma cells in vitro using 125I seeds.

AIM: To determine the mechanism of the radiation-induced biological effects of 125I seeds on pancreatic carcinoma cells in vitro. METHODS: SW1990 and PANC-1 pancreatic cancer cell lines were cultured in DMEM in a suitable environment. Gray's model of iodine-125 (125I) seed irradiation was used. In vitro, exponential phase SW1990, and PANC-1 cells were exposed to 0, 2, 4, 6, and 8 Gy using 125I radioactive seeds, with an initial dose rate of 12.13 cGy/h. A clonogenic survival experiment was performed to observe the ability of the cells to maintain their clonogenic capacity and to form colonies. Cell-cycle and apoptosis analyses were conducted to detect the apoptosis percentage in the SW1990 and PANC-1 cells. DNA synthesis was measured via a tritiated thymidine (3H-TdR) incorporation experiment. After continuous low-dose-rate irradiation with 125I radioactive seeds, the survival fractions at 2 Gy (SF2), percentage apoptosis, and cell cycle phases of the SW1990 and PANC-1 pancreatic cancer cell lines were calculated and compared. RESULTS: The survival fractions of the PANC-1 and SW1990 cells irradiated with 125I seeds decreased exponentially as the dose increased. No significant difference in SF2 was observed between SW1990 and PANC-1 cells (0.766±0.063 vs 0.729±0.045, P<0.05). The 125I seeds induced a higher percentage of apoptosis than that observed in the control in both the SW1990 and PANC-1 cells. The rate of apoptosis increased with increasing radiation dosage. The percentage of apoptosis was slightly higher in the SW1990 cells than in the PANC-1 cells. Dose-dependent G2/M cell-cycle arrest was observed after 125I seed irradiation, with a peak value at 6 Gy. As the dose increased, the percentage of G2/M cell cycle arrest increased in both cell lines, whereas the rate of DNA incorporation decreased. In the 3H-TdR incorporation experiment, the dosimetry results of both the SW1990 and PANC-1 cells decreased as the radiation dose increased, with a minimum at 6 Gy. There were no significant differences in the dosimetry results of the two cell lines when they were exposed to the same dose of radiation. CONCLUSION: The pancreatic cancer cell-killing effects induced by 125I radioactive seeds mainly occurred via apoptosis and G2/M cell cycle arrest.

A novel rapamycin-polymer conjugate based on a new poly(ethylene glycol) multiblock copolymer.

PURPOSE: Rapamycin has demonstrated potent anti-tumor activity in preclinical and clinical studies. However, the clinical development of its formulations was hampered due to its poor solubility and undesirable distribution in vivo. Chemical modification of rapamycin presents an opportunity for overcoming the obstacles and improving its therapeutic index. The objective of this study is to develop a drug-polymer conjugate to increase the solubility and cellular uptake of rapamycin. METHODS: We developed the rapamycin-polymer conjugate using a novel, linear, poly(ethylene glycol) (PEG) based multiblock copolymer. Cytotoxicity and cellular uptake of the rapamycin-polymer conjugate were evaluated in various cancer cells. RESULTS: The rapamycin-polymer conjugate provides enhanced solubility in water compared with free rapamycin and shows profound activity against a panel of human cancer cell lines. The rapamycin-polymer conjugate also presents high drug loading capacity (wt% ~ 26%) when GlyGlyGly is used as a linker. Cellular uptake of the conjugate was confirmed by confocal microscopic examination of PC-3 cells that were cultured in the presence of FITC-labled polymer (FITC-polymer). CONCLUSION: This study suggests that the rapamycin-polymer conjugate is a novel anti-cancer agent that may provide an attractive strategy for treatment of a wide variety of tumors.

Development of cholesteryl peptide micelles for siRNA delivery.

Despite the rapid progress in the siRNA field, developing a safe and efficient delivery system of siRNA remains to be an obstacle in the therapeutical application of siRNA. The purpose of this study is to develop an efficient peptide-based siRNA delivery system for cancer therapy. To this end, cholesterol was conjugated to a series of peptides composed of lysine and histidine residues. The resultant cholesteryl peptides were characterized, and their potential for siRNA delivery was evaluated. Our results indicate that short peptides (11-21 mer) composed of various numbers of lysine and histidine residues alone are not sufficient to mediate efficient siRNA delivery. However, the amphiphilic cholesteryl peptides can self-assemble to form a micelle-like structure in aqueous solutions, which significantly promotes the siRNA condensation capability of the peptides. The cholesteryl peptides form stable complex with siRNA and effectively protect siRNA from degradation in rat serum up to three days. Furthermore, the cholesteryl peptides efficiently transfect siRNA into different cancer cells and trigger potent gene silencing effect, whereas peptides without cholesterol modification cannot deliver siRNA into the cells. In addition, one of the cholesteryl peptides Chol-H3K2s displays comparable cellular uptake and gene silencing effect but less cytotoxicity compared with branched polyethylenimine (bPEI) and Lipofectamine-2000. Our results reveal that the cholesteryl peptides possess great potential as an efficient siRNA delivery system.

Expression profile and functional activity of peptide transporters in prostate cancer cells.

Peptide transporters are expressed predominantly in intestinal and renal epithelial cells. The functional expression of peptide transporters is also identified in other types of tissues, such as glia cells, macrophages, and the epithelia of the bile duct, the lungs, and the mammary glands. However, their presence and role are poorly understood in carcinomas. We explored the expression profile and functional activity of peptide transporters in the prostate cancer cell lines LNCaP, PC-3, and DU145. Quantitative real time RT-PCR (qRT-PCR) and Western blot were used to evaluate the expression profile of peptide transporter 1 (PEPT1), peptide transporter 2 (PEPT2), peptide histidine transporter 1 (PHT1), and peptide histidine transporter 2 (PHT2) in these cells. LNCaP expresses high levels of PEPT2 and PHT1, while PC-3 demonstrates strong expression of PEPT1 and PHT1. DU145 shows only weak expression of PEPT1 and PHT1. Functional activities were studied in these cell lines using radiolabeled glycylsarcosine ([(3)H]Gly-Sar) and l-histidine ([(3)H]-l-histidine). The uptake of [(3)H]Gly-Sar and [(3)H]-l-histidine was time- and pH-dependent. A kinetic study showed that the uptake of Gly-Sar and l-histidine is saturable over the tested concentration range. The binding affinity (K(m)) and the maximal velocity (V(max)) exhibited in the three cell lines were consistent with the expression profiles we observed in qRT-PCR and Western blot analysis. A competitive inhibition study revealed that peptide transporters in prostate cancer cells exhibited broad substrate specificity with a preference for hydrophobic dipeptides, such as Leu-Leu. Fluorescence microscopy study revealed that the fluorescent dipeptide probe d-Ala-Lys-AMCA (a substrate of peptide transporters) specifically accumulated in the cytoplasm of LNCaP and PC-3, but not DU145 cells. Inhibiting the peptide transporter activity by Gly-Sar suppressed the growth of LNCaP and PC-3 cells. Our study indicated that PC-3 cells can be established as a new cell culture model for PEPT1 study, and LNCaP can be used as a model for PEPT2 study. Moreover, our results suggested that peptide transporters are overexpressed in prostate cancer cells and can be adopted as a promising target for tumor-specific drug delivery.

Gadolinium-loaded polymeric nanoparticles modified with Anti-VEGF as multifunctional MRI contrast agents for the diagnosis of liver cancer.

Molecular imaging is essential to increase the sensitivity and selectivity of cancer diagnosis especially in the early stage of tumor. Here, we designed a novel multifunctional polymeric nanoparticle contrast agent (Anti-VEGF PLA-PEG-PLL-Gd NP) simultaneously modified with Gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) and anti-vascular endothelial growth factor (VEGF) antibody to deliver Gd-DTPA to the tumor area and achieve the early diagnosis of hepatocellular carcinoma (HCC). The Anti-VEGF PLA-PEG-PLL-Gd NPs exhibited high T(1) relaxivity and no obvious cytotoxicity under the experimental concentrations in human hepatocellular carcinoma (HepG2) cells. The results of in vitro cell uptake experiments demonstrated that the uptake process of NPs was both concentration and time depended. Compared with non-targeted NPs, the Anti-VEGF antibody modified NPs showed much higher cell uptake in the HepG2 cells. During in vivo studies, the targeted NPs showed significantly signal intensity enhancement at the tumor site (mouse hepatocarcinoma tumor, H22) compared with non-targeted NPs and Gd-DTPA injection in tumor-bearing mice and the imaging time was significantly prolonged from less than an hour (Gd-DTPA injection group) to 12 h. These results demonstrated that this novel MRI contrast agent Anti-VEGF PLA-PEG-PLL-Gd NPs showed great potential in the early diagnosis of liver tumors.

Enhanced gene transfection efficiency in CD13-positive vascular endothelial cells with targeted poly(lactic acid)-poly(ethylene glycol) nanoparticles through caveolae-mediated endocytosis.

The efficient delivery of therapeutic gene into cells of interest is a critical challenge to broad application of non-viral vectors. The approach of introducing ligands that lead gene vectors to target caveolae-mediated endocytosis on nanoparticle surface might serve as a promising strategy for the effective gene transfection. Recently, in an attempt to enhance the possibility of caveolae-mediated endocytosis, we fabricated a peptide-targeted gene vector for highly efficient receptor-mediated intracellular delivery. Cyclic Asn-Gly-Arg (cNGR) peptide was used to target gene loaded poly(lactic acid)-poly(ethylene glycol) nanoparticles (PLA-PEG NPs) to HUVEC over-expressing CD13. Using 6-lauroxyhexyl lysinate (LHLN) as cationic surfactant, cNGR modified PLA-PEG NPs (cNGR-PEG-PLA NPs) were capable of complexing and compacting DNA into homogeneous small-sized complexes (<200nm) with positive charge (~10mV). Fortunately, the results of in vitro cellular uptake tests and mechanism studies were consistent with our original hypothesis. The cNGR peptide presented on nanoparticles' surface could specifically mediate the fast and efficient internalization of cNGR-PEG-PLA NPs into HUVEC. Moreover, free cNGR inhibited their intracellular uptake into HUVEC revealing the mechanism of receptor-mediated endocytosis. Furthermore, the inspiring results of the mechanism studies and transfection assays demonstrated that caveolae-mediated endocytosis was indeed mainly involved in the internalization of cNGR-PEG-PLA NPs into HUVEC and led to significant gene transfection efficiency in contrast with cNGR non-modified PLA-PEG NPs. Given such encouraging and favorable properties including biocompatibility, high transfer efficiency, low cytotoxicity, and fast uptake by nondestructive endocytic pathways, cNGR-PEG-PLA NPs could be a promising carrier for the intracellular delivery of therapeutic agents.

Gadolinium-conjugated PLA-PEG nanoparticles as liver targeted molecular MRI contrast agent.

A nanoparticle magnetic resonance imaging (MRI) contrast agent targeted to liver was developed by conjugation of gadolinium (Gd) chelate groups onto the biocompatible poly(l-lactide)-block-poly (ethylene glycol) (PLA-PEG) nanoparticles. PLA-PEG conjugated with diethylenetriaminopentaacetic acid (DTPA) was used to formulate PLA-PEG-DTPA nanoparticles by solvent diffusion method, and then Gd was loaded onto the nanoparticles by chelated with the unfolding DTPA on the surface of the PLA-PEG-DTPA nanoparticles. The mean size of the nanoparticles was 265.9 ± 6.7 nm. The relaxivity of the Gd-labeled nanoparticles was measured, and the distribution in vivo was evaluated in rats. Compared with conventional contrast agent (Magnevist), the Gd-labeled PLA-PEG nanoparticles showed significant enhancement both on liver targeting ability and imaging signal intensity. The T(1) and T(2) relaxivities per [Gd] of the Gd-labeled nanoparticles was 18.865 mM(-1) s(-1) and 24.863 mM(-1) s(-1) at 3 T, respectively. In addition, the signal intensity in vivo was stronger comparing with the Gd-DTPA and the T(1) weight time was lasting for 4.5 h. The liver targeting efficiency of the Gd-labeled PLA-PEG nanoparticles in rats was 14.57 comparing with Magnevist injection. Therefore, the Gd-labeled nanoparticles showed the potential as targeting molecular MRI contrast agent for further clinical utilization.