Background: Townes and Berkeley mouse models of sickle cell disease (SCD) are commonly used to study SCD pathophysiology and to develop novel therapies. Although the pathophysiology in these models ...is similar to the human disease, there are distinct differences. For example, Townes SS mice have higher ATP and lower 2,3-diphosphyglycerate (2,3-DPG) levels compared to Townes AA mice. This contrasts with SCD patients, who show lower ATP and higher 2,3-DPG levels, suggesting potential differences between human and murine red blood cell (RBC) metabolism. Pyruvate kinase (PK), a key ATP-generating enzyme in glycolysis, is a target for novel SCD therapies. While PK activators have been shown to increase hemoglobin in clinical trials, such treatments do not consistently lead to the same hematological change in mouse models, further indicating that PK properties may differ between SCD mouse models and human patients. A detailed comparative characterization of PK and glycolytic metabolites in murine SCD models and SCD patients is therefore important. Aim: To study PK properties in murine and human SCD RBCs. Methods: Wild-type (C57BL/6J), Townes (AA and SS) and Berkeley mice (non-sickling and sickling) were used. Human blood was obtained from healthy controls (HbAA) and untreated SCD patients (HbSS). Hematological parameters were measured using the Sysmex hematology analyzer. PK (Vmax, 5mM substrate) and hexokinase (HK) activity, and PK thermostability (53°C) were measured in purified RBCs. Levels of ATP, 2,3-DPG, as well as reduced glutathione (GSH) were measured by targeted LC-MS/MS and spectrophotometry, respectively. P50 (oxygen tension at which 50% of hemoglobin is saturated with oxygen) was measured with the Hemox analyzer (TCS). Statistical analysis was performed in Graphpad Prism 9.4.1. by Welch's t-test. Results: Samples from 17 wild-type mice, 21 Townes mice (10 AA, 11 SS), 15 Berkeley mice (7 non-sickling, 8 sickling) and 12 human subjects (6 HbAA, 6 HbSS) were included. Both Townes and Berkeley SCD mice showed increased PK activity (Table 1; p<0.0001). This may be attributed to their high reticulocyte counts (Townes SS vs. AA: 43% vs. 4%; Berkeley sickling vs. non-sickling: 30% vs. 6%), because when normalizing PK activity to that of HK, another RBC age-dependent enzyme, no genotype differences were found in these mouse models. This lack of PK/HK difference was in sharp contrast with our finding in human controls vs. SCD patients (Table 1). Notably, both Berkeley sickling and non-sickling mice had lower PK/HK ratio than their Townes counterparts (p<0.0001). Mouse PK thermostability was markedly reduced compared to that of human, and PK from the two sickling mice was less stable than their non-sickling controls (Fig. 1). Moreover, both sickling mice showed higher ATP/2,3-DPG ratio (Table 1; p<0.01). This was again in direct contrast with our observation using human blood, where SCD patients had lower ATP/2,3-DPG ratio than healthy controls (p<0.05). Even though there was no difference in ATP/2,3-DPG ratio between the two SCD models, Townes SS mice had significantly lower 2,3-DPG and higher ATP levels than Townes AA mice, whereas Berkeley sickling mice only had significantly higher ATP level compared to their controls. Furthermore, sickling mice had lower P50 value compared to non-sickling mice, reflecting a higher oxygen affinity. This also contrasted with human SCD patients, who had higher P50 value than healthy controls (Table 1). GSH levels were increased in both SCD patients and sickling mice, although the elevation was more pronounced in sickling mice (Table 1). Conclusions: This study reveals important distinctions between mouse models and humans: no differences in PK/HK ratio between sickling and non-sickling mice, and an overall lower PK thermostability in mice. Furthermore, this study shows significant changes in 2,3-DPG content (important for oxygen affinity), energy level (ATP), oxygen affinity (P50) and antioxidant level (GSH) when comparing sickling to non-sickling mice. Sickling mice also have higher ATP/2,3-DPG ratio, which contrasts with SCD patients. These differences should be considered when studying PK activators in SCD mouse models and extrapolating results from SCD mouse models to humans.
To determine if there is added value to oncology studies performed with a dedicated in-line positron emission tomography (PET)/computed tomography (CT) scanner as compared with PET read side by side ...with diagnostic CT (DCT).
Forty-one consecutive oncology patients referred for PET/CT who had contemporary DCT scans for review were enrolled. Body regions assessed on a DCT scan were assessed on PET/CT and by side-by-side reading of PET and DCT (SBS PET/DCT). Lesions identified on DCT, the CT portion of PET/CT, SBS PET/DCT, and the reading of fused PET/CT images were scored as benign or malignant. The PET portion of the PET/CT study was read by 2 teams: the first read the SBS PET/DCT scan and the other read the complete fused PET/CT scan. For discordant lesions, the final diagnosis was determined by pathologic findings (n = 6) or imaging follow-up (n = 21).
Twenty-seven (16.1%) of the 168 lesions were discordant when comparing analysis of fused PET/CT and SBS PET/DCT. Sixteen (9.5%) were fundamentally discordant, and 11(6.6%) were discordant in degree of confidence. For all discordant lesions only, the sensitivity, specificity, negative predictive value, positive predictive value, and accuracy for PET/CT were 100%, 33%, 100%, 94%, and 78%, respectively, and for SBS PET/DCT, they were 38%, 50%, 19%, 73%, and 30%, respectively (P < 0.001 for sensitivity, P = not specific for specificity). The 2 main causes for misclassification on SBS PET/DCT were incorrect localization (n = 12) and changes occurring in the time gap between DCT and PET/CT (n = 4).
In-line PET/CT offers better lesion localization in comparison to the visual fusion of PET and CT, especially for small lymph nodes, lesions adjacent to mobile organs, or lesions adjacent to the chest or abdominal wall.
Purpose
The aim of the study was to elaborate the incidence and type of skeletal involvement in a large cohort of patients with newly diagnosed prostate cancer (PCa) referred for Ga-68 PSMA-11 PET/CT ...staging in a single center.
Methods
Study cohort included 963 consecutive patients with newly diagnosed PCa referred for Ga-68 PSMA-11 PET/CT study for staging. The incidence of bone involvement, type of bone metastases, and extent of disease were determined and correlated with the ISUP Grade Group (GG) criteria and PSA levels.
Results
Bone metastases were found in 188 (19.5%) of 963 patients. Bone metastases were found in 10.7% of patients with PSA < 10 ng/dL and in 27.4% of patients with PSA > 10 ng/dL and in 6.1% of patients with GG ≤ 2/3 and in 8.9% of patients with GG 4/5. In 7.6% of the patients, skeletal involvement was extensive, while 11.9% of patients had oligometastatic disease. Osteoblastic type metastases were the most common type of bone metastases presented in 133 of the patients with malignant bone involvement (70.7%). More than half of them had only osteoblastic lesions (72 patients (38.3%)), while the other (61 patients (32.5%)) had also intramedullary and/or osteolytic type lesions. Intramedullary metastases were found in 97 patients (51.6%), while 41 (21.8%) of them were only intramedullary lesions. Osteolytic metastases were detected in 36 patients (19.2%), of which 8 were only osteolytic lesions.
Conclusion
Although traditionally bone metastases of PCa are considered osteoblastic, osteolytic and intramedullary metastases are common, as identified on PET with labeled PSMA. Skeletal spread may be present also in patients with GG ≤ 2/3 and PSA < 10 ng/dL.
68Ga-labeled prostate-specific membrane antigen (PSMA), a PET tracer that was recently introduced for the imaging of prostate cancer, may accumulate in other solid tumors, including hepatocellular ...carcinoma (HCC). The aim of this study was to assess the potential role of 68Ga-PSMA PET/CT in the imaging of HCC. Methods: Included in this prospective pilot study were 7 patients who had HCC with 41 liver lesions: 37 suspected malignant lesions (tumor lesions) and 4 regenerative nodules. For each liver lesion, the uptake of 68Ga-PSMA and the uptake of 18F-FDG were measured (as SUV and lesion-to-liver background ratios TBR-SUV) and correlated with dynamic characteristics (Hounsfield units HU and TBR TBR-HU) obtained from contrast-enhanced CT data. Immunohistochemical staining of PSMA in the tumor tissue was analyzed in samples obtained from 5 patients with HCC and compared with that of control samples obtained from 3 patients with prostate cancer. Results: Thirty-six of the 37 tumor lesions and none of the regenerative nodules showed increased 68Ga-PSMA uptake, and only 10 lesions were 18F-FDG–avid. On the basis of contrast enhancement, tumor lesions were categorized as 27 homogeneously enhancing lesions, 9 lesions with “mosaic” enhancement (composed of enhancing and nonenhancing regions in the same lesion), and a single nonenhancing lesion (the only non–68Ga-PSMA–avid lesion). The Mann–Whitney test revealed that 68Ga-PSMA uptake was significantly higher in enhancing tumor areas than in nonenhancing areas and, in contrast, that 18F-FDG uptake was higher in nonenhancing areas (P < 0.001 for both). 68Ga-PSMA uptake (TBR-SUVmax) was found to correlate with vascularity (TBR-HU) (Spearman r, 0.866; P < 0.001). Immunohistochemistry showed intense intratumoral microvessel staining for PSMA in HCC; in contrast, cytoplasmic and membranous staining, mainly in the luminal border, was seen in prostate cancer samples. In 2 of the study patients, 68Ga-PSMA PET/CT identified unexpected extrahepatic metastases. The 4 regenerative liver nodules showed no increased uptake of either PET tracer. Conclusion: 68Ga-PSMA PET/CT was superior to 18F-FDG PET/CT for imaging patients with HCC. HCC lesions are more commonly hypervascular, taking up 68Ga-PSMA in tumoral microvessels. 68Ga-PSMA PET/CT is a potential novel modality for imaging patients with HCC.
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