New perspectives on metabolic imaging in the management of prostate cancer in 2022: A focus on radiolabeled PSMA­PET/CT (Review).

Nuclear medicine is an essential part of prostate cancer management concerning initial staging, patient follow-up and even therapy. Prostate-specific membrane antigen (PSMA) is a glutamate carboxypeptidase II transmembrane glycoprotein expressed by 80% of prostatic cells. The interest in this protein is due to its specificity for prostatic tissue. The use of 68GaPSMA PET/CT in the context of disease staging is thus well-established and recommended, especially for high-risk disease with metastases and lymph node involvement. However, the risk of false positives raises questions regarding its place in the management of patients with prostate cancer. The present study aimed to determine the use of PET-PSMA in the care of patients with prostate cancer but also to assess its limits of use.

Impairment of lysosomal function by Clostridioides difficile TcdB.

TcdB is a potent cytotoxin produced by pathogenic Clostridioides difficile that inhibits Rho GTPases by mono-glucosylation. TcdB enters cells via receptor-mediated endocytosis. The pathogenic glucosyltransferase domain (GTD) egresses endosomes by pH-mediated conformational changes, and is subsequently released in an autoproteolytic manner. We here investigated the uptake, localization and degradation of TcdB. TcdB colocalized with lysosomal marker protein LAMP1, verifying the endosomal-lysosomal route of the toxin. In pulse assays endocytosed TcdB declined to a limit of detection within 2 hr, whereas the released GTD accumulated for up to 8 hr. We observed that autoproteolytic deficient TcdB NXN C698S was degraded significantly faster than wildtype TcdB, suggesting interference of TcdB with lysosomal degradation process. In fact, TcdB reduced lysosomal degradation of endosome cargo as tested with DQ-Green BSA. Lysosomal dysfunction was accompanied by perinuclear accumulation of LAMP1 and a weaker detection in immunoblots. Galectin-8 or galectin-3 was not recruited to lysosomes speaking against lysosome membrane damage. Changes in the autophagosomal marker LC3B suggested additional indirect effect of lysosomal dysfunction on the autophagic flux. In contrast to necrotic signaling induced in by TcdB, lysosomal dysfunction was not abolished by calcium channel blocker nifedipin, indicating separate cytopathogenic effects induced by TcdB during endo-lysosomal trafficking.

Receptor Binding Domains of TcdB from Clostridioides difficile for Chondroitin Sulfate Proteoglycan-4 and Frizzled Proteins Are Functionally Independent and Additive.

Toxin B (TcdB) produced by Clostridioides difficile is a main pathogenicity factor that affects a variety of different cell types within the colonic mucosa. TcdB is known to utilize frizzled-1,2,7 and chondroitin sulfate proteoglycan-4 (CSPG4) as protein receptors. By using human cervical cancer cell line HeLa CSPG4 knockout (CSPG4-/-) cells as well as TcdB mutants which do not bind to either CSPG4 or frizzled-1,2,7, or both, we evaluated the impact of the individual receptors for cytopathic and cytotoxic effects of TcdB. We compared TcdB from the reference strain VPI10463 (TcdBVPI) and the endemic strain R20291 (TcdBR20) which does not interact with frizzled-1,2,7. TcdBVPI devoid of CSPG4 binding (TcdBVPI ΔCROP) shows identical cytopathic potency as full-length TcdB in HeLa CSPG4-/- cells, indicating that interaction with frizzled proteins is not affected in the presence of the C-terminal CROP domain. We validated CSPG4 as cellular receptor for both TcdB toxinotypes in HeLa and HEp-2 cells. By exchange of a single phenylalanine residue, 1597 with serine, we generated a mutated TcdBVPI variant (TcdBVPI F1597S) that in accordance with TcdBR20 lacks binding to frizzled-1,2,7 and showed identical potency as TcdBR20 on HeLa cells. This enabled us to estimate the respective share of CSPG4 and frizzled-1,2,7 in the cytotoxic and cytopathic effect induced by TcdB. Our data reveal that binding to frizzled-1,2,7 and to CSPG4 occurs independently and in an additive manner.

Activating human epidermal growth factor receptor 2 (HER2) gene mutation in bone metastases from breast cancer.

In addition to amplification, point mutations of the human epidermal growth factor receptor 2 (HER2) gene (ERBB2) have been shown to activate the corresponding signaling pathway in breast cancer. The prevalence of ERBB2/HER2 mutation in bone metastasis of breast cancer and the associated phenotype are not known. In this study, bone metastases from breast cancer patients (n = 231) were analyzed for ERBB2/HER2 mutation. In 7 patients (3%; median age 70 years, range 50-83 years), gain-of-function mutations of ERBB2/HER2 were detected. The most frequent mutation was p.L755S (71%). In 29% of mutated cases, p.V777L was found. Lobular breast cancer was present in 71% of mutated cases (n = 5) and in 49% of all samples (n = 231; p = 0.275). Mutation frequency was 4.4% in the lobular subgroup and 17.4% in the pleomorphic subtype of lobular cancer (n = 23), respectively. All but one mutated lobular cancers were of the pleomorphic subtype (p = 0.006). Mutated cancers belonged either to the luminal (n = 4) or to the triple-negative types (n = 3). With regard to protein expression and gene amplification, HER2 was negative in all mutated cases. Among the 14% of metastatic luminal cancers with estrogen receptor gene (ESR1) mutation, conveying resistance against aromatase inhibitors, no concomitant ERBB2/HER2 mutation occurred. We conclude that activating HER2 mutation is present in about 3% of bone metastases from breast cancers, with significantly higher rates in the pleomorphic subtype of lobular cancer. Since mutated cases appear to be HER2-negative by conventional testing, the opportunity for specific anti-HER2 therapy may be missed.