RESUMO
BACKGROUND: According to pathologico-clinical features, patients diagnosed with localized prostate cancer (PCa) are stratified into distinct risk groups (low-risk, intermediate-risk or high-risk). Data have demonstrated that 68Gallium-prostate-specific membrane antigen positron emission tomography (68Ga-PSMA PET/CT) is superior to conventional radiological exams (CT or MRI and bone scintigraphy) in the primary staging of high-risk localized PCa. However, it is still unknown if in a population of high-risk PCa, there would be a subgroup of patients with a higher probability of identifying metastatic disease by the 68Ga-PSMA PET/CT. MATERIALS AND METHODS: Data from patients with localized PCa who underwent 68GA-PSMA PET/CT for primary staging from four institutions were retrospectively collected. We selected patients with at least one D'Amico classification risk factor (International Society of Urological Pathology ≥ IV and/or prostate-specific antigen > 20 ng/ml). To detect an association between extent of disease and number of risk factors as well as International Society of Urological Pathology prostate cancer grade, contingency tables were used, and Fisher Exact Test was performed. RESULTS: Between 2016 and 2020, 60 patients underwent a 68GA-PSMA PET/CT for primary staging of high-risk localized PCa. Regarding the number of risk factors, 37 patients (62%) had one risk factor, and 23 (38%) had two risk factors. In the subgroup of patients with metastatic disease (n = 22), those with two risk factors had higher incidence of metastatic disease, and it was statistically significant (p = 0.011). CONCLUSION: This retrospective analysis demonstrated that 68GA-PSMA PET/CT was able to identify advanced disease in more than one-third of patients with high-risk disease especially those with two adverse risk factors.
RESUMO
Approximately half of poor prognosis neuroblastomas (NBs) are characterized by pathognomonic MYCN gene amplification and MYCN over-expression. Here we present data showing that short-interfering RNA mediated depletion of the protein arginine methyltransferase 5 (PRMT5) in cell-lines representative of NBs with MYCN gene amplification leads to greatly impaired growth and apoptosis. Growth suppression is not apparent in the MYCN-negative SH-SY5Y NB cell-line, or in two immortalized human fibroblast cell-lines. Immunoblotting of NB cell-lines shows that high PRMT5 expression is strongly associated with MYCN-amplification (P < 0.004, Mann-Whitney U-test) and immunohistochemical analysis of primary NBs reveals that whilst PRMT5 protein is ubiquitously expressed in the cytoplasm of most cells, MYCN-amplified tumours exhibit pronounced nuclear PRMT5 staining. PRMT5 knockdown in MYCN-overexpressing cells, including the SHEP-21N cell-line with inducible MYCN expression leads to a dramatic decrease in MYCN protein and MYCN-associated cell-death in SHEP-21N cells. Quantitative gene expression analysis and cycloheximide chase experiments suggest that PRMT5 regulates MYCN at a post-transcriptional level. Reciprocal co-immunoprecipitation experiments demonstrated that endogenous PRMT5 and MYCN interact in both SK-N-BE(2)C and NGP cell lines. By using liquid chromatography - tandem mass spectrometry (LC-MS/MS) analysis of immunoprecipitated MYCN protein, we identified several potential sites of arginine dimethylation on the MYCN protein. Together our studies implicate PRMT5 in a novel mode of MYCN post-translational regulation and suggest PRMT5 plays a major role in NB tumorigenesis. Small-molecule inhibitors of PRMT5 may therefore represent a novel therapeutic strategy for neuroblastoma and other cancers driven by the MYCN oncogene.
