99mTc(CO)3-labeled 1-(2-Pyridyl)piperazine derivatives as radioligands for 5-HT7 receptors.

BACKGROUND: The 5-hydroxytryptamine receptor (5-HTR) family includes seven classes of receptors. The 5-HT7R is the newest member of this family and contributes to different physiological and pathological processes. As a pathology, glioblastoma multiform (GBM) overexpresses 5-HT7R; hence, this study aims to develop radiolabeled aryl piperazine derivatives as 5-HT7R imaging agents.  METHODS: Compounds 6 and 7 as 1-(3-nitropyridin-2-yl)piperazine derivatives were radiolabeled with fac-[99mTc(CO)3(H2O)3]+ and 99mTc(CO)3-[6] and 99mTc(CO)3-[7] were obtained with high radiochemical purity (RCP > 94%). The stability of the radiotracers was evaluated in both saline and mouse serum. Specific binding on different cell lines including U-87 MG, MCF-7, SKBR3, and HT-29 was performed. The biodistribution of these radiotracers was evaluated in normal and U-87 MG Xenografted models. Finally, 99mTc(CO)3-[6] and 99mTc(CO)3-[7] were applied for in vivo imaging in U-87 MG Xenografted models. RESULTS: Specific binding study indicates that 99mTc(CO)3-[6] and 99mTc(CO)3-[7] can recognize 5-HT7R of U87-MG cell line. The biodistribution study in normal mice indicates that the brain uptake of 99mTc(CO)3-[6] and 99mTc(CO)3-[7] is the highest at 30 min post-injection (0.8 ± 0.25 and 0.64 ± 0.18%ID/g, respectively). The data of the biodistribution study in the U87-MG xenograft model revealed that these radiotracers could accumulate in the tumor site, and the highest tumor uptake was observed at 60 min post-injection (3.38 ± 0.65 and 3.27 ± 0.5%ID/g, respectively). The injection of pimozide can block the tumor's radiotracer uptake, indicating the binding of these radiotracers to the 5-HT7R. The imaging study in the xenograft model also confirms the biodistribution data. The acquired images clearly show the tumor site, and the tumor-to-muscle ratio for 99mTc(CO)3-[6] and 99mTc(CO)3-[7] at 60 min was 3.33 and 3.88, respectively.  CONCLUSIONS: 99mTc(CO)3-[6] and 99mTc(CO)3-[7] can visualize tumor in the U87-MG xenograft model  due to their affinity toward 5-HT7R.

Evaluation of myocardial viability by a secondary delayed 99mTc-MIBI nuclear scanning in ST-elevation myocardial infarction patients with delay in referral and nonviable myocardium in the first scintigraphy: a preliminary cohort study.

OBJECTIVE: In the management of ST-segment elevation myocardial infarction (STEMI), if the treatment has not been initiated within the first 24 h and the patient no longer exhibits any symptoms, the decision to begin revascularization therapy is based on myocardial viability. If the tissue is nonviable, current guidelines advise against further revascularization therapy; however, collateral vessels represent an alternative source of blood supply and may help the damaged tissue to resume function; though at first, this tissue may not be considered viable. Thus, in patients whose first myocardial perfusion scintigraphy (MPS) revealed nonviable myocardium, a secondary MPS to assess viability may be beneficial and alter the course of treatment strategies. METHODS: This prospective cohort study was conducted on 30 STEMI patients referred to Mazandaran Heart Center. If no myocardial viability was found using 99mTc-MIBI MPS, the patient was referred for a secondary MPS after 3 months. RESULTS: In total, out of 30 patients, 3 became viable. There was no significant relationship between the viability of different Rentrop classes. Comparison of viability between patients with different numbers of occluded vessels showed no significant relationship. Three patients (17%) among 17 patients with Rentrop class nonzero became viable in the second MPS. Also, among four patients (13.3%) with Rentrop class three, one patient (25%) became viable and among seven patients (23.3%) with Rentrop class one, two patients (28.6%) became viable. CONCLUSION: Considering the results of this study, although nonsignificant, this subject requires further investigation to reach a definite conclusion.

The preclinical study of 177Lu-DOTA-LTVSPWY as a potential therapeutic agent against HER2 overexpressed cancer.

BACKGROUND: Peptide receptor radionuclide therapy (PRRT) has evolved in cancer therapy and diagnosis. LTVSPWY, as a peptide, can target HER2 receptor; on the other hand, 177Lu emits ß- which is helpful for cancer therapy. The radiolabeling of LTVSPWY with 177Lu results in a therapeutic agent (177Lu-DOTA-LTVSPWY) capable of cancer treatment. METHODS: 177Lu-DOTA-LTVSPWY was prepared with high radiochemical purity (RCP). The stability was investigated in saline and human serum. The radiotracer affinity toward the SKOV-3 cell line with overexpression of the HER2 receptor was evaluated. Then the impact of the radiotracer on the colony formation of the SKOV-3 cell line was investigated with colony assay. Moreover, the biodistribution of this radiotracer in SKOV-3 xenograft tumor-bearing nude mice were also studied to determine the radiotracer accumulation in the tumor site. The mice were treated with 177Lu-DOTA-LTVSPWY and subjected to histopathological evaluation. RESULTS: The RCP of 177Lu-DOTA-LTVSPWY after radiolabeling and stability tests was more than 97.7%. The radiotracer displayed high affinity toward the SKOV-3 cell line (KD = 6.6 ± 3.2 nM). Treatment of the SKOV-3 cell line with the radiotracer reduces the SKOV-3 colony survival to less than 3% for 5 MBq of the radiotracer. Tumor-to-muscle (T/M) ratio is the highest at 48 h and 1 h post-injection (2.3 and 4.75, respectively). The histopathological study also confirms the cellular damage to the tumor tissue. CONCLUSIONS: 177Lu-DOTA-LTVSPWY can recognize HER2 receptors in vivo and in vitro; hence, it can serve as a therapeutic agent.

Comparison of early surgical and conservative therapy in children with ureteropelvic junction obstruction.

BACKGROUND: Ureteropelvic junction obstruction is a relatively common urologic problem in children. Most cases present with pelvicaliceal dilatation in antenatal period. Historically most UPJO cases were treated with surgical procedures, but recently many of these children have been treated by nonsurgical observational plans. We compared the outcome of children with UPJO treated in surgical and observational ways. METHODS: In a retrospective study, we assessed the medical history of patients diagnosed as UPJO, march 2011 to march 2021. The case definition was based on grade 3-4 hydronephrosis and obstructive pattern in dynamic renal isotopes can. Patients were put into two groups; Group 1 children were treated with a surgical procedure, and group 2 patients without any surgical procedure for at least a six months' period after diagnosis. We assessed long-term events and improvement of obstruction. RESULTS: Seventy-eight children (mean age 7.32mo., 80% male) enrolled in the study, 55 patients in group one and 23 as group 2. Severe hydronephrosis was the problem of 96% of all patients significantly led to 20% in group 1 and 9% in group 2 (P < 0.001). Severe kidney involvement was observed at 91% in group 1 and 83% in group 2, decreased to 15% and 6%, respectively (P < 0.001). There were no significant differences in sonographic and functional improvement between the two intervention groups. Long-term prognostic issues; growth, functional impairment, and hypertension were not different between the two groups, but group 1 children experienced more recurrence of UTI than group 2 patients. CONCLUSION: Conservative management is as effective as early surgical treatment in the management of infants with severe UPJO.

Molecular Imaging of HER2 Expression in Breast Cancer patients Using the [99mTc] Tc-Labeled Small Peptide.

PURPOSE: The accurate determination of human epidermal growth factor receptor 2 (HER2) status can predict response to treatment with HER2-targeted therapy for HER2-positive breast cancer patients. [99mTc]Tc-HYNIC-(Ser)3-LTVPWY ([99mTc]Tc-HYNIC-LY) is a small synthetic peptide molecule targeting of the HER2 receptor. This clinical study evaluated the pharmacokinetic, dosimetry, and efficacy of [99mTc]Tc-HYNIC-LY for determining the HER2 status in primary breast cancer patients. MATERIALS AND METHODS: In total, 24 women with suspected primary breast cancer received an intravenous injection of approximately 20 µg (∼740 MBq) of [99mTc]Tc-HYNIC-LY. In the first 3 patients, blood levels of radioactivity were analyzed for pharmacokinetic evaluation and planar gamma camera imaging was conducted at 30 min and 1, 2, 4, and 24 hour after injection for dosimetry assessment. In the last 21 patients, planar imaging was performed at the baseline, as well as 1, 2, 3, and 4 hour, followed by single-photon emission computed tomography (SPECT) imaging after 4 hour to evaluate the tumor-targeting potential in primary lesions. RESULTS: Injection of [99mTc]Tc-HYNIC-LY was safe and well tolerated. Fast blood clearance provided high-contrast HER2 imaging within 1 to 4 hour. The highest absorbed radiation dose was found for kidneys (6.78E-03 ± 2.62E-04 mSv/MBq), followed by the heart (3.73E-03 ± 1.98E-04 mSv/MBq). The [99mTc]Tc-HYNIC-LY peptide was able to detect HER2 status in primary tumors at an acceptable level. CONCLUSION: The findings of this study indicated that [99mTc]Tc-HYNIC-LY SPECT is safe and feasible for the identification of HER2-positive lesions in primary breast cancer patients, and may provide an accurate and non-invasive modality for guiding HER2 targeted therapy.

Melissa Officinalis L. aqueous extract pretreatment decreases methotrexate-induced hepatotoxicity at lower dose and increases 99mTc-phytate liver uptake, as a probe of liver toxicity assessment, in rats.

OBJECTIVE: Hepatotoxicity remains amongst the restricting factors of Methotrexate (MTX)-associated cancer therapy, especially in high doses of chemo-drugs or prolonged treatment. Due to the known protective effects of Melissa officinalis (M. officinalis), the aqueous extract of this plant was evaluated to ameliorate MTX-associated hepatotoxicity in rats. METHODS: Adult female Wistar rats were received or not M. officinalis aqueous extract at doses of 100 mg/kg (for 14 and 24 consecutive days) and 2 g/kg (for 14 consecutive days) by gavage technique. MTX (20 mg/kg) was intraperitoneally injected on the 10th- and 20th-day post-M. officinalis treatment. 24 h after the last day of treatment, 99mTc-phytate was intravenously injected through the tail of rats. Animals were killed at 20 min after radiocolloid injection, and vital tissues including the liver and spleen were isolated, weighed, and their radioactivity was counted. As well, 99mTc-phytate scintigraphy and histopathology of the liver were performed for higher accuracy. RESULT: A significant increase in liver radioactivity was detected in M. officinalis+MTX receiving groups compared with the MTX rats which were more robust at a dose of 100 mg/kg for 14 days. Also, a significant reduction in liver radioactivity was evident with M. officinalis extract at a dose of 2 g/kg for 14 days in comparison with the control group, this reduction was not significant at the lower dose of 100 mg/kg. Gamma scintigraphy and histopathological examinations confirmed the hepatoprotective effect of M. officinalis vs MTX-induced liver injury in rats. CONCLUSION: In conclusion, we highlighted the liver uptake of 99mTc-phytate as a valuable method for assessment of liver toxicity and addressed that M. officinalis pretreatment (100 mg/kg for 14 days) ameliorates the MTX-associated hepatotoxicity in rats; however, M. officinalis itself induces liver toxicity at higher doses.

[99mTc]-labeling and evaluation of a new linear peptide for imaging of glioblastoma as a αvß3-positive tumor.

PURPOSE: In this study, we designed a new linear 6-Hydrazinonicotinamide (HYNIC)-conjugated peptide (HYNIC-KRWrNM) (M-6) and labeled with technetium-99m for gamma imaging of glioblastoma as a αvß3-positive tumor. We evaluated tumor targeting ability of this radio-peptide and compared with previous 99mTc-labeled HYNIC-conjugated RGD analogue peptides. PROCEDURES: One new linear peptide (HYNIC-KRWrNM) (M-6) was designed and labeled with technetium-99m in the presence of 2-[[1,3-dihydroxy-2-(hydroxymethyl) propan-2-yl] amino] acetic acid (Tricine)/Ethylenediamine-N,N'-diacetic acid (EDDA) as co-ligand system. Then, this 99mTc-labeled peptide ([99mTc]Tc-M-7) was evaluated for in vitro stability in saline and serum, specific binding assay, internalization, and binding affinity (Kd). In addition, we performed biodistribution study and planar imaging on nude mice bearing U87-MG xenograft as a αvß3-positive tumor. RESULTS: The radiochemical yield of [99mTc]Tc-M-7 was obtained ˃95%. This 99mTc-labeled peptide remained stable and intact in saline solution after 24 h incubation. In addition, metabolic stability of this 99mTc-labeled peptide was obtained ˃60% after 4 h incubation in serum. The Kd value for [99mTc]Tc-M-7 was obtained 5.2 ± 1.0 nM. Based on biodistribution results in nude mice bearing U87-MG xenograft, tumor/muscle activity ratio was 6.22 and decreased to 1.89 in blocking group at the same time point (4 h p.i.). The blocking experiment results also indicated that tumor uptake and kidney uptake were αvß3-mediated. In comparison with previous HYNIC-conjugated RGD analogue peptides, kidneys had the highest uptake of this 99mTc-labeled peptide (52.29 ± 11.48 at 1.5 h p.i. and 27.04 ± 0.66%ID/g at 4 h p.i.). Finally, similar to previous 99mTc-labeled HYNIC-conjugated RGD analogue peptides, [99mTc]Tc-M-7 showed acceptable tumor uptake after 4 h post-injection (based on ROI technique, target-to-background activity ratio = 3.80). CONCLUSIONS: This small linear 99mTc-labeled peptide, with high affinity to αvß3 integrin, desirable water solubility, and cost efficient, demonstrates a potent tumor targeting ability as well as previous HYNIC-conjugated RGD analogue peptides. Hence, [99mTc]Tc-M-7 can be of service to as a new candidate for early detection of αvß3-positive tumors.

Homodimer 99mTc-HYNIC-E(SSSLTVPWY)2 peptide improved HER2-overexpressed tumor targeting and imaging.

We hypothesized that a novel design of the LTVPWY (LY) peptide might exhibit a great potential for improving binding affinity and targeting HER2-overexpressed tumors. Hence, new dimer construction of 99mTc-labeled LY [99mTc-HYNIC-E(SSSLTVPWY)2] (99mTc-DLY) was introduced. Afterward, a head-to-head comparison of in vitro and in vivo experiments was performed between 99mTc-DLY and 99mTc-HYNIC-SSSLTVPWY as the monomer analog. The blocking dosage of trastuzumab reduced the uptake of the dimer about 20% more efficiently than the monomer in the SKOV-3 cell line. A twofold increase in competitive binding affinity and biological half-life was observed for 99mTc-DLY. The ovarian-tumor-bearing mice were detected with high contrast where the tumor-to-muscle ratio of 99mTc-DLY was notably increased about 40% using a gamma camera. The biodistribution experiment revealed an approximately 10% enhancement in tumor/blood, tumor/muscle, and tumor/bone ratios for the dimer. More rapid blood clearance was another achievement of the homodimer design. Overall, 99mTc-DLY successfully affected the pharmacokinetics and consequently the visualization of HER2-overexpressing tumors.

The Potential Usefulness of 99mTc-HYNIC-(Ser)3-LTVPWY Peptide for Predicting HER2 Status Alteration After Chemotherapy in Ovarian Tumor-Bearing Mice.

Purpose: The assessment of HER2 expression has a significant impact on optimizing cancer treatment protocol in patients. The aim of this study was to evaluate the potential usefulness of 99mTc-HYNIC-(Ser)3-LTVPWY peptide for detecting HER2 alteration after paclitaxel therapy of ovarian tumor xenografts in nude mice. Materials and Methods: Mice bearing SKOV-3 tumors were treated with paclitaxel and saline. The antitumor efficacy of paclitaxel was compared with the control group in tumor size and histopathological examinations. In biodistribution and imaging studies, the tumor uptakes of radiolabeled peptide were evaluated in mice-bearing ovarian tumors in both groups. The HER2 expressions in transplanted tumors were analyzed by immunohistochemistry (IHC). Results: Tumor size gradually increased in all mice during the treatment, whereas tumors had considerably faster growth in the saline group compared to those in the paclitaxel-treated mice. Paclitaxel could suppress ovarian tumor growth and prevent vascular and cell proliferation in the tumoral mass. Biodistribution and imaging results demonstrated nonsignificant radionuclide accumulations in transplanted tumors in the paclitaxel- and saline-treated groups. IHC staining confirmed the HER2 status that was similar in both groups. Conclusions: The response of HER2 status to paclitaxel in mice bearing HER2-expression tumors was profitably monitored by HER2 targeted 99mTc-HYNIC-(Ser)3-LTVPWY peptide that was agreement with IHC. The utilization of this radiolabeled peptide may be a valuable probe in evaluating HER2 status after chemotherapy.

Protecting High-Risk Oncology Patients During the COVID-19 Pandemic by Creating an Isolated Outpatient Clinic.

PURPOSE: Delivering care for immunocompromised, high-risk patients with cancer during a pandemic has proven challenging. Patients with cancer on chemotherapy have a high risk of mortality if contracted COVID-19. If a patient goes directly to the emergency room, multiple contact points with other individuals can lead to unnecessary exposures from any airborne virus, such as COVID-19. Our cancer center has implemented an isolated clinic with personal protective equipment and direct access to a COVID-19 rule-out floor to manage those with febrile neutropenia (FN). METHODS: We implemented an outpatient, isolated, extended-hour clinic with access to personal protective equipment, laboratories, and antibiotics for patients with FN as a pilot project from April 1 to December 31, 2020, with the aim to decrease emergency department (ED) visits for FN by 50%. RESULTS: Since the implementation of our clinic, we have screened 74 unique patients during 102 visits, of which 76 led to a discharge and 26 led to a direct admit, thus avoiding the ED. Thirty-nine of these visits were for patients with recent travel or a known COVID-19 exposure. Bringing these patients to our isolated clinic ensured safety of the approximately 200 patients undergoing active treatment in our infusion center daily. CONCLUSION: Implementing this clinic has thus far successfully decreased the social footprint of our highest-risk patients with cancer in the ED considerably. Our efforts and hopes of decreasing the possible exposure of our immunocompromised patients to COVID-19 as well as the unnecessary exposure of the infusion center patients and personnel have thus far been effective.

The PI3K/AKT/mTOR signaling pathway inhibitors enhance radiosensitivity in cancer cell lines.

INTRODUCTION: Radiotherapy is one of the most common types of cancer treatment modalities. Radiation can affect both cancer and normal tissues, which limits the whole delivered dose. It is well documented that radiation activates phosphatidylinositol 3-kinase (PI3K) and AKT signaling pathway; hence, the inhibition of this pathway enhances the radiosensitivity of tumor cells. The mammalian target of rapamycin (mTOR) is a regulator that is involved in autophagy, cell growth, proliferation, and survival. CONCLUSION: The inhibition of mTOR as a downstream mediator of the PI3K/AKT signaling pathway represents a vital option for more effective cancer treatments. The combination of PI3K/AKT/mTOR inhibitors with radiation can increase the radiosensitivity of malignant cells to radiation by autophagy activation. Therefore, this review aims to discuss the impact of such inhibitors on the cell response to radiation.

Added diagnostic value of SPECT to evaluate bone metastases in breast cancer patients with normal whole body bone scan.

BACKGROUND: In this research, we aimed to survey the added value of single photon emission computed tomography (SPECT) in comparison with planar whole body bone scan to visualize bone metastatic lesions in patients with breast cancer. METHODS: A total of 80 patients with breast cancer (invasive ductal carcinoma) were examined with planar whole body bone scan and SPECT imaging using 99mTc-labelled methylene diphosphonate (99mTc-MDP). The patients with abnormal uptakes in SPECT imaging were also investigated with magnetic resonance imaging (MRI). RESULTS: Among these 80 patients with normal whole body bone SPECT scan, 19 (23.25%) of them revealed abnormal 99mTc-MDP uptake in skeleton. Furthermore, these 19 patients were subjected to MRI and 3 (3.75%) of them were confirmed with metastatic bone lesion. CONCLUSION: The obtained data suggest that SPECT possess the added diagnostic over planar whole body bone scan.

Synthesis and Biological Evaluation of 99mTc-Labeled Phenylpiperazine Derivatives as Selective Serotonin-7 Receptor Ligands for Brain Tumor Imaging.

With a poor prognosis, glioblastoma multiforme is the most aggressive tumor of the central nervous system in humans. The aim of this study was to develop novel tracers for the tumor targeting and imaging of overexpressed serotonin-7 receptors (5-HT7Rs) in U-87 MG glioma xenografted nude mice. Two phenylpiperazine derivatives named as PHH and MPHH were designed, and the corresponding radiotracers 99mTc-PHH and 99mTc-MPHH were synthesized in high radiochemical purity (>95%). 99mTc-MPHH showed a higher affinity to 5-HT7Rs on U-87 MG cells compared to 99mTc-PHH. In biodistribution studies, the radiocomplexes showed good brain uptake at 15 min combined with good radioactivity retention in the brain for 240 min. Regional rabbit brain studies indicated a higher radioactivity concentration in the hippocampus and diencephalon than in the cerebellum. Compared to 99mTc-MPHH, the 99mTc-PHH exhibited a significantly increased tumor uptake at 15 and 60 min, but the rapid blood clearance of 99mTc-MPHH led to enhanced tumor-to-muscle ratios at 240 min. A significant reduction in tumor uptake 60 min after an injection of pimozide (5-HT7 receptor antagonist) confirms the tumor uptake was receptor-mediated specifically. The tumor-to-contralateral muscle tissue ratio of 99mTc-PHH and 99mTc-MPHH in nude mice with U-87 MG xenograft was measured (5.25 and 4.65) at 60 min as well as (6.25 and 6.76) at 240 min, respectively.

The effects of pharmacological interventions, exercise, and dietary supplements on extra-cardiac radioactivity in myocardial perfusion single-photon emission computed tomography imaging.

Myocardial perfusion imaging (MPI) as an imaging modality plays a key role in the monitoring of patients with cardiovascular disease. MPI enables the assessment of cardiovascular disease, the effectiveness of therapy, and viable myocardial tissue. However, MPI suffers from some downfalls and limitations, which can influence its clinical applications. These limitations can arise from the patient's condition, equipment, or the actions of the technologist. In this review, we mainly focused on the different effective parameters on radioactivity uptake of organs including liver, intestines, stomach, and gall bladder and how they affect the quality of the acquired images in nuclear medicine. More importantly, we cover how different suggested medicines, foods and exercise alleviative this problem.

Febuxostat therapy in outpatients with suspected COVID-19: A clinical trial.

BACKGROUND: The aim of this clinical trial was to evaluate the effects of febuxostat (FBX) in comparison with hydroxychloroquine (HCQ) on clinical symptoms, laboratory tests and chest CT findings in outpatients with moderate symptoms of COVID-19 infection. METHODS: We conducted a clinical trial involving adult outpatients with the moderate respiratory illness following COVID-19 infection. Patients were randomly assigned to receive either FBX or HCQ for 5 days. The measured variables were needs to hospitalisation, clinical and laboratory data including fever, cough, breathing rate, C-Reactive Protein level, lymphocytes count at onset of admission and was well as at 5 days of treatments. In addition, CT findings were evaluated on admission and 14 days after initiation of treatment. RESULTS: Sixty subjects were enrolled in the study with a 1 to 1 ratio in FBX and HCQ groups. On admission, fever (66.7%), cough (87%), tachypnoea (44.4%), dyspnoea (35%), elevated CRP value (94.4%) and lung involvement according to chest CT (100%) were documented in enrolled patients with insignificant difference between FBX and HCQ groups. Fever, cough and tachypnoea were significantly mitigated in both groups after five days of treatments without any significant differences between groups. The mean percentages of lung involvement were significantly reduced to 7.3% and 8% after 14 days of treatment with FBX and HCQ, respectively. In adult outpatients with moderate COVID-19 infection, the effectiveness of FBX and HCQ was not different in terms of resolution of clinical manifestations, laboratory tests and lung CT findings. CONCLUSION: This trial suggests that FBX is as an alternative treatment to HCQ for COVID-19 infection and may be considered in patients with a contraindication or precaution to HCQ.

Evaluation of a New 99mTc-labeled GnRH Analogue as a Possible Imaging Agent for Prostate Cancer Detection.

INTRODUCTION: Prostate cancer is a serious threat to men's health so it is necessary to develop technics for early detection of this malignancy. The purpose of this research was the evaluation of a new99mTc-labeled GnRH analogue as an imaging probe for tumor targeting of prostate cancer. METHODS: 99mTc-labeled-DLys6-GnRH analogue was prepared based on HYNIC as a chelating agent and tricine/ EDDA as coligands for labeling with 99mTc. HYNIC was coupled to epsilon amino group of DLys6 through aminobutyric acid (GABA) as a linker. Radiochemical purity and stability in normal saline and serum, were determined by TLC and HPLC methods. Furthermore, calculation of protein-binding and partition coefficient constant were carried out for 99mTc labeled peptide. The cellular experiments including receptor binding specificity and affinity were studied using three prostate cancer cell lines LN-CaP, DU-145 and PC-3. Finally, the animal assessment and SPECT imaging of radiolabeled GnRH analogue were evaluated on normal mice and nude mice bearing LN-CaP tumor. RESULTS: The GnRH conjugate was labeled with high radiochemical purity (~97%). The radiolabeled peptide showed efficient stability in the presence of normal saline and human serum. The in vitro cellular assays on three prostate cancer cell lines indicated that the radiotracer was bound to LN-CaP cells with higher affinity compared to DU-145 and PC-3 cells. The Kd values of 99mTc- HYNIC (tricine/ EDDA)-Gaba-D-Lys6GnRH were 89.39±26.71, 93.57±30.49 and107.3±18.82 in LN-CaP, PC-3 and DU-145 cells respectively. The biodistribution studies in normal mice and LN-CaP tumor-bearing nude mice showed similar results including rapid blood clearance and low radioactivity accumulation in non-target organs. High kidney uptake proved that the main excretion route of radiopeptide was through the urinary system. The tumor uptake was 1.72±0.45 %ID/g at 1h p.i. decreasing to 0.70±0.06%ID/g at 4h p.i. for 99mTc-HYNIC-Gaba-D-Lys6GnRH. The maximum tumor/ muscle ratio was 2.30 at 1h p.i. Pre-saturation of receptor using an excess of unlabeled peptide revealed that the tumor uptake was receptor mediated. The results of the SPECT image of LN-CaP tumor were in agreement with the biodistribution data. CONCLUSION: Based on this study, we suggest LN-CaP as a favorable cell line for in vivo studies on GnRH analogues. Moreover, this report shows that 99mTc-HYNIC (tricine/EDDA)-Gaba-D-Lys6GnRH may be a suitable candidate for further evaluation of prostate cancer.

99m Tc-(EDDA/tricine)-HYNIC-GnRH analogue as a potential imaging probe for diagnosis of prostate cancer.

Prostate cancer is a serious threat to men's health, so it is necessary to develop the techniques for early detection of this malignancy. Radiolabeled peptides are the useful tools for diagnosis of prostate cancer. In this research, we designed a new HYNIC-conjugated GnRH analogue and labeled it by 99m Tc with tricine/EDDA as coligands. We used aminohexanoic acid (Ahx) as a hydrocarbon linker to generate 99m Tc-(tricine/EDDA)-HYNIC-Ahx-[DLys6 ]GnRH. The radiopeptide exhibited high radiochemical purity and stability in solution and serum. Two human prostate cancer cell lines LN-CaP and DU-145 were used for cellular experiments. The binding specificity and affinity of radiopeptide for LN-CaP were superior to DU-145 cells. The Kd values for LN-CaP and DU-145 cells were 41.91 ± 7.03 nM and 55.96 ± 10.56 nM, respectively. High kidney uptake proved that the main excretion route of radiopeptide was through the urinary system. The tumor/muscle ratio of 99m Tc-HYNIC-Ahx-[DLys6 ]GnRH was 4.14 at 1 hr p.i. that decreased to 2.41 at 4 hr p.i. in LN-CaP tumor-xenografted nude mice. The blocking experiment revealed that the tumor uptake was receptor-mediated. The lesion was visualized clearly using 99m Tc-[DLys6 ]GnRH at 1 hr p.i. Accordingly, this research highlights the capability of 99m Tc-(tricine/EDDA)-HYNIC-Ahx-[DLys6 ]GnRH peptide as a promising agent for GnRHR-expressing tumor imaging.

99mTc-radiolabeled HER2 targeted exosome for tumor imaging.

Exosomes represent unique features including nontoxicity, non-immunogenicity, biodegradability, and targeting ability that make them suitable candidates for clinical applications. Therefore, in this study, 99mTc-radiolabel HER2 targeted exosomes (99mTc-exosomes) were provided for tumor imaging. These exomes are obtained from genetically engineered cells and possessed DARPin G3 as a ligand for HER2 receptors. These exosomes were radiolabeled using fac-[99mTc(CO)3(H2O)3]+ synthon. The quality control showed high radiochemical purity (RCP) for 99mTc-exosomes (>96%). 99mTc-exosomes displayed a higher affinity toward SKOV-3 cells (higher HER2 expression) in comparison with MCF-7, HT29, U87-MG, A549 cell lines at different levels of HER2 expression. Trastuzumab (an antibody with a high affinity toward HER2) inhibited the binding of 99mTc-exosomes to SKOV-3 cells up to 40%. Biodistribution study in SKOV-3 tumor bearing nude mice confirmed the ability of 99mTc-exosomes for accumulation in the tumor. 99mTc-exosomes can visualize tumor in SKOV-3 tumor-bearing nude mouse. The blockage of HER2 receptors using trastuzumab (excessive amount) suggests the 99mTc-exosomes binding to the receptors and reduced the accumulation of 99mTc-exosomes in the tumor site. This suggest that 99mTc-exosomes interact with HER2 receptors and act through specific targeting.

Evaluation of 99mTc-HYNIC-(ser)3-LTVPWY peptide for glioblastoma imaging.

Purpose: Early and accurate imaging of glioblastoma is of great value in staging, metastatic detection, treatment management and prognosis. The human epidermal growth factor receptor 2 (HER2) plays an essential role in the tumorigenesis and tumor progression in cancer. The aim of this study was to develop HER2-targeted peptide for glioma tumor imaging.Material and methods: HYNIC-(Ser)3-LTVPWY peptide was labeled with technetium-99m in presence of EDDA/tricine mixture as co-ligands. 99mTc-HYNIC-(Ser)3-LTVPWY peptide was assessed for cellular specific binding and receptor-binding affinity. The biodistribution study and tumor imaging were conducted in nude mice bearing U-87 MG glioma xenografts.Results: The in vitro blocking study demonstrated specific binding of 99mTc-HYNIC-(Ser)3-LTVPWY in cultured U-87 MG cells with a KD of 9.7 ± 2.0 nM. Biodistribution study revealed tumor to blood and tumor to muscle ratios were about 5.55 and 6.65 respectively after 1 h injection of radiolabeled peptide. Blocking study with non-labeled counterpart indicated a significant reduction (68%) in tumor uptake of 99mTc-HYNIC-(Ser)3-LTVPWY that is indicated the tumor specificity of the radiolabeled peptide on glioblastoma. Gamma planar imaging revealed that the U-87 MG tumor was clearly visualized at 1 h.Conclusion: The results of this study showed that the 99mTc-HYNIC-(Ser)3-LTVPWY peptide specifically accumulates in glioma and is, therefore, a promising probe for the diagnosis of glioma.