Recurrence rate after radical prostatectomy following primary staging of high-risk prostate cancer with 68Ga-PSMA PET/CT

BACKGROUND

Accurate primary staging is one of the most important issues for initial management of prostate cancer (PCa) patients to perform an optimal selection of patients for curative intended treatment. ⁶⁸Ga-Prostate-Specific-Membrane-Antigen (PSMA) PET/CT was found superior to conventional imaging both for detection of recurrence after curative intended treatment and for primary staging. We studied the recurrence rate after radical prostatectomy in high-risk PCa patients primary staged with ⁶⁸Ga-PSMA PET/CT compared with conventional imaging.

MATERIAL AND METHODS

The study included 247 D'Amico high-risk PCa patients treated with radical prostatectomy (RP) after primary staging with ⁶⁸Ga-PSMA PET/CT and a reference group of 137 high-risk patients with RP after conventional imaging (^99mTc bone scintigraphy and CT). Recurrence rates were assessed by Cox regression and Kaplan-Meier analysis.

RESULTS

The 5-year recurrence-free survival rate was 71.1% in the ⁶⁸Ga-PSMA PET/CT cohort compared with 56.4% in the conventional imaging cohort. Primary staging by ⁶⁸Ga-PSMA PET/CT reduced biochemical recurrence (BCR) risk by 42% (HR = 0.58 (0.41-0.83), p = .004).

CONCLUSION

The present data could indicate a lower recurrence rate after RP following primary staging with ⁶⁸Ga-PSMA PET/CT compared to conventional imaging, likely due to improved selection of patients for surgery.

A genome-wide CRISPR-Cas9 knockout screen identifies novel PARP inhibitor resistance genes in prostate cancer

DNA repair gene mutations are frequent in castration-resistant prostate cancer (CRPC), suggesting eligibility for poly(ADP-ribose) polymerase inhibitor (PARPi) treatment. However, therapy resistance is a major clinical challenge and genes contributing to PARPi resistance are poorly understood. Using a genome-wide CRISPR-Cas9 knockout screen, this study aimed at identifying genes involved in PARPi resistance in CRPC. Based on the screen, we identified PARP1, and six novel candidates associated with olaparib resistance upon knockout. For validation, we generated multiple knockout populations/clones per gene in C4 and/or LNCaP CRPC cells, which confirmed that loss of PARP1, ARH3, YWHAE, or UBR5 caused olaparib resistance. PARP1 or ARH3 knockout caused cross-resistance to other PARPis (veliparib and niraparib). Furthermore, PARP1 or ARH3 knockout led to reduced autophagy, while pharmacological induction of autophagy partially reverted their PARPi resistant phenotype. Tumor RNA sequencing of 126 prostate cancer patients identified low ARH3 expression as an independent predictor of recurrence. Our results advance the understanding of PARPi response by identifying four novel genes that contribute to PARPi sensitivity in CRPC and suggest a new model of PARPi resistance through decreased autophagy.

The transcriptional landscape and biomarker potential of circular RNAs in prostate cancer

Background

Circular RNAs (circRNAs) constitute a largely unexplored source for biomarker discovery in prostate cancer (PC). Here, we characterize the biomarker potential of circRNAs in PC, where the need for novel diagnostic and prognostic tools to facilitate more personalized management is pressing.

Methods

We profiled the transcriptomic landscape of circRNAs in PC by total RNA sequencing of 31 adjacent-normal and 143 tumor samples from localized (radical prostatectomy (RP)) and metastatic PC patients (cohort 1, training). Diagnostic and prognostic potential was evaluated in cohort 1, and 39 top circRNA candidates were selected for validation in two additional PC cohorts (cohort 2, n = 111; RP cohort 3, n = 191) by NanoString-based expression analysis. Biochemical recurrence (BCR)-free survival was assessed using Kaplan-Meier, univariate, and multivariate Cox regression analyses. The circRNA candidates were further detected in extracellular vesicle (EV)-enriched plasma samples from PC patients and controls (cohort 4, n = 54).

Results

Expression of circABCC4, circFAT3, circATRNL1, and circITGA7 was highly cancer-specific (area under the curve 0.71–0.86), while low circITGA7 expression was significantly (P < 0.05) associated with BCR in univariate analysis in two RP cohorts. Moreover, we successfully trained and validated a novel 5-circRNA prognostic signature (circKMD1A/circTULP4/circZNF532/circSUMF1/circMKLN1) significantly associated with BCR beyond routine clinicopathological variables (RP cohort 1: P = 0.02, hazard ratio = 2.1; RP cohort 3: P < 0.001, hazard ratio = 2.1). Lastly, we provide proof-of-principle for detection of candidate circRNAs in EV-enriched plasma samples from PC patients.

Conclusions

circRNAs hold great biomarker potential in PC and display both high cancer specificity and association to disease progression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13073-021-01009-3.

68Ga-PSMA PET/CT for Primary Lymph Node and Distant Metastasis NM Staging of High-Risk Prostate Cancer

With the largest high-risk prostate cancer (PCa) cohort to date undergoing ⁶⁸Ga-prostate-specific membrane antigen (PSMA) PET/CT primary staging, we aimed to, first, characterize the metastatic spread of PCa in relation to tumor ⁶⁸Ga-PSMA uptake and the D'Amico classification and, second, compare ⁶⁸Ga-PSMA PET/CT findings with radical prostatectomy and pelvic lymph node dissection (PLND) histopathology findings. Methods: The study included 691 consecutive newly diagnosed, biopsy-proven, treatment-naïve, D'Amico high-risk PCa patients primary-staged by ⁶⁸Ga-PSMA PET/CT. PSMA SUV_max and metastatic findings were compared with prostate-specific antigen level, International Society of Urological Pathology (ISUP) grade, and clinical stage as traditional risk stratification parameters. Moreover, ⁶⁸Ga-PSMA PET/CT findings were compared with histology findings in radical prostatectomy patients undergoing PLND. Undetected lymph node metastases (LNMs) underwent immunohistochemical PSMA staining. Results: Advanced disease (N1/M1) was observed in 35.3% of patients (244/691) and was associated with increasing prostate-specific antigen level, ISUP grade, and clinical stage. LNMs (N1/M1a) were detected in 31.4% (217/691) and bone metastases (M1b) in 16.8% (116/691). Advanced disease frequencies in patients with ISUP grades 2 and 3 were 10.8% (11/102) and 37.1% (33/89), respectively. Risk of advanced disease for cT2a, cT2b, and cT2c tumors was almost equal (24.2%, 27.9%, and 22.4%, respectively). We observed a weak correlation between SUV_max and biopsy ISUP grade (ρ = 0.21; P < 0.001) and a modest correlation between SUV_max and postprostatectomy ISUP grade (ρ = 0.38; P < 0.001). Sensitivity, specificity, positive and negative predictive value, and accuracy for LNM detection on ⁶⁸Ga-PSMA PET/CT in the PLND cohort were 30.6%, 96.5%, 68.8%, 84.5%, and 83.1%, respectively. Undetected LNMs either were micrometastases located in the lymph node border or were without PSMA expression. Conclusion: In this high-risk PCa cohort, we identified advanced disease in about one third at diagnosis. ISUP grade was the superior predictor for advanced disease at diagnosis. We found a significant difference in frequency of advanced disease between ISUP grades 2 and 3, as supports the Gleason score 7 subdivision. Interestingly, we observed no significant differences in risk of advanced disease when comparing the different cT2 stages. The undetected LNMs were either PSMA-negative or micrometastases.

Intramuscular Botulinum toxin A injections induce central changes to axon initial segments and cholinergic boutons on spinal motoneurones in rats

Intramuscular injections of botulinum toxin block pre-synaptic cholinergic release at neuromuscular junctions producing a temporary paralysis of affected motor units. There is increasing evidence, however, that the effects are not restricted to the periphery and can alter the central excitability of the motoneurones at the spinal level. This includes increases in input resistance, decreases in rheobase currents for action potentials and prolongations of the post-spike after-hyperpolarization. The aim of our experiments was to investigate possible anatomical explanations for these changes. Unilateral injections of Botulinum toxin A mixed with a tracer were made into the gastrocnemius muscle of adult rats and contralateral tracer only injections provided controls. Immunohistochemistry for Ankyrin G and the vesicular acetylcholine transporter labelled axon initial segments and cholinergic C-boutons on traced motoneurones at 2 weeks post-injection. Soma size was not affected by the toxin; however, axon initial segments were 5.1% longer and 13.6% further from the soma which could explain reductions in rheobase. Finally, there was a reduction in surface area (18.6%) and volume (12.8%) but not frequency of C-boutons on treated motoneurones potentially explaining prolongations of the after-hyperpolarization. Botulinum Toxin A therefore affects central anatomical structures controlling or modulating motoneurone excitability explaining previously observed excitability changes.