Third-Generation Psa: Ultrasensitive or Ultraprecise Assay?

Prostate-Specific Antigen as an Ultrasensitive Biomarker for Patients with Early Recurrent Prostate Cancer: How Low Shall We Go? A Systematic Review

Serum prostate-specific antigen (PSA) needs to be monitored with ultrasensitive PSA assays (uPSAs) for oncologists to be able to start salvage radiotherapy (SRT) while PSA is <0.5 µg/L for patients with prostate cancer (PCa) relapsing after a radical prostatectomy (RP). Our systematic review (SR) aimed to summarize uPSAs for patients with localized PCa. The SR was registered as InPLASY2023110084. We searched for studies on Google Scholar, PUBMED and reference lists of reviews and studies. We only included studies on uPSAs published in English and excluded studies of women, animals, sarcoidosis and reviews. Of the 115 included studies, 39 reported PSA assay methods and 76 reported clinical findings. Of 67,479 patients, 14,965 developed PSA recurrence (PSAR) and 2663 died. Extremely low PSA nadir and early developments of PSA separated PSAR-prone from non-PSAR-prone patients (cumulative p value 3.7 × 1012). RP patients with the lowest post-surgery PSA nadir and patients who had the lowest PSA at SRT had the fewest deaths. In conclusion, PSA for patients with localized PCa in the pre-PSAR phase of PCa is strongly associated with later PSAR and survival. A rising but still exceedingly low PSA at SRT predicts a good 5-year overall survival.

Orientation of capture antibodies on gold nanoparticles to improve the sensitivity of ELISA-based medical devices

The sensitivity of ELISA-based devices strongly depends on the right orientation of antibodies on the sensor surface. The aim of this work was to increase the analytical performance of a commercial ELISA-based medical device (VIDAS®), thanks to the specific orientation of antibodies on gold nanostructured disposables. For this purpose, fPSA VIDAS® assay was used as model and the disposable providing the antigen binding surface (SPR®) was functionalized with gold nanostructures coated with monovalent half-fragment antibodies (reduced IgG, rIgG). The functionalization of polystyrene SPRs® with gold nanostructures was achieved through a one-step incubation of gold dispersions in a mixture of non-toxic solvents. Five different concentrations of gold nanoparticles (NPs) were tested with a maximum fluorescence enhancement for NPs density around 3-8 *10³ NPs/μm² (752 ± 11 RFV vs 316 ± 5 RFV of bare SPRs®). The comparison of the dose-response curve obtained with commercial and gold coated-SPRs® revealed a significant improvement (p < 0.0001) of the analytical sensitivity of the VIDAS® system using nanostructured disposables. This improved version of SPRs® allows to distinguish small variations of fPSA concentrations opening the way to the application of this biomarker to other kinds of cancer as recently described in the literature.

A novel microfluidic microplate as the next generation assay platform for enzyme linked immunoassays (ELISA)

In this work we introduce a novel microfluidic enzyme linked immunoassays (ELISA) microplate as the next generation assay platform for unparalleled assay performances. A combination of microfluidic technology with standard SBS-configured 96-well microplate architecture, in the form of microfluidic microplate technology, allows for the improvement of ELISA workflows, conservation of samples and reagents, improved reaction kinetics, and the ability to improve the sensitivity of the assay by multiple analyte loading. This paper presents the design and characterization of the microfluidic microplate, and its application in ELISA.

Regulation of prostate-specific antigen by activin A in prostate cancer LNCaP cells

Activins are multifunctional growth and differentiation factors and stimulate FSH-beta gene expression and FSH secretion by the pituitary gonadotropes. Follistatins bind activin, resulting in the neutralization of activin bioactivity. The activin/follistatin system is present in the prostate tissue. Prostate-specific antigen (PSA) plays an important role in male reproductive physiology as well as being very important as a tumor marker for prostate cancer. Thus the regulation of PSA has important clinical implications. Previous studies showed that PSA is primarily regulated by androgens. In the present study, we evaluated the direct effects of activin A on the proliferation and PSA production of prostate cancer LNCaP cells, which express functional activin receptors and androgen receptor and PSA. LNCaP cells were treated with activin A and 5alpha-dihydrotestosterone (DHT) with or without their antagonists (follistatin or the nonsteroidal anti-androgen bicalutamide). Activin A decreased cell growth of LNCaP cells in a dose-dependent manner, whereas DHT increased it in a biphasic manner. In contrast to their opposing actions on cell growth, both activin A and DHT upregulated PSA gene expression and increased PSA secretion by LNCaP cells. The effects of activin A and DHT to increase PSA production were synergistic or additive. Follistatin or bicalutamide was without effect on cell growth or PSA production. The effects of activin A on LNCaP cells were blocked by follistatin, not by bicalutamide, whereas effects of DHT were prevented by bicalutamide, not by follistatin. Activin A upregulates PSA production, and the effect is through an androgen receptor-independent pathway. The activin/follistatin system can be a physiological modulator of PSA gene transcription and secretion in the prostate tissue, and activins may cooperate with androgen to upregulate PSA in vivo.

Ultrasensitive assay of prostate-specific antigen for early detection of residual cancer after radical prostatectomy

OBJECTIVES

Perhaps the greatest value of PSA determination in the treatment of prostate cancer is in determining persistent disease after a radical prostatectomy. We investigated the ability of an ultrasensitive PSA assay to detect residual prostate cancer in men at risk for recurrence after a radical prostatectomy.

METHODS

Using the Immulite third-generation PSA assay (detection limit, less than 0.003 ng/mL), and the standard IMx PSA assay, we determined PSA levels in 205 serum samples serially obtained from 34 men after a radical prostatectomy. The average days from surgery to serum sampling was 430 (range, 63 to 1296). Patients were classified as having nonaggressive or aggressive cancers, based on clinicopathologic findings. A biochemical relapse was arbitrarily defined.

RESULTS

All 17 patients with nonaggressive cancers had PSA values of less than 0.02 ng/mL throughout the sampling period. Two of these patients (12%) had 2 or more consecutive PSA increases and were considered as a biochemical relapse. In contrast, 14 (82%) of 17 patients with aggressive cancers fit criteria of a biochemical relapse. All of the relapses were identified within 2 years after surgery. The IMx assay detected only 7 biochemical relapses during the same sampling period.

CONCLUSIONS

Using the Immulite PSA assay, relapse detection times may be shortened allowing for most serological recurrences to be detected within 2 years after a radical prostatectomy. Patients with aggressive cancers may require frequent postoperative PSA determinations with a highly sensitive PSA assay which would allow early intervention when treatments for relapse are effective.