Association between phosphodiesterase type 5 inhibitors and prostate cancer: A systematic review

2022 Update on Prostate Cancer Epidemiology and Risk Factors-A Systematic Review

CONTEXT

Prostate cancer (PCa) is one of the most common cancers worldwide. Understanding the epidemiology and risk factors of the disease is paramount to improve primary and secondary prevention strategies.

OBJECTIVE

To systematically review and summarize the current evidence on the descriptive epidemiology, large screening studies, diagnostic techniques, and risk factors of PCa.

EVIDENCE ACQUISITION

PCa incidence and mortality rates for 2020 were obtained from the GLOBOCAN database of the International Agency for Research on Cancer. A systematic search was performed in July 2022 using PubMed/MEDLINE and EMBASE biomedical databases. The review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines and was registered in PROSPERO (CRD42022359728).

EVIDENCE SYNTHESIS

Globally, PCa is the second most common cancer, with the highest incidence in North and South America, Europe, Australia, and the Caribbean. Risk factors include age, family history, and genetic predisposition. Additional factors may include smoking, diet, physical activity, specific medications, and occupational factors. As PCa screening has become more accepted, newer approaches such as magnetic resonance imaging (MRI) and biomarkers have been implemented to identify patients who are likely to harbor significant tumors. Limitations of this review include the evidence being derived from meta-analyses of mostly retrospective studies.

CONCLUSIONS

PCa remains the second most common cancer among men worldwide. PCa screening is gaining acceptance and will likely reduce PCa mortality at the cost of overdiagnosis and overtreatment. Increasing use of MRI and biomarkers for the detection of PCa may mitigate some of the negative consequences of screening.

PATIENT SUMMARY

Prostate cancer (PCa) remains the second most common cancer among men, and screening for PCa is likely to increase in the future. Improved diagnostic techniques can help reduce the number of men who need to be diagnosed and treated to save one life. Avoidable risk factors for PCa may include factors such as smoking, diet, physical activity, specific medications, and certain occupations.

How do phosphodiesterase-5 inhibitors affect cancer? A focus on glioblastoma multiforme

Since the discovery of phosphodiesterase-5 (PDE5) enzyme overexpression in the central nervous system (CNS) malignancies, investigations have explored the potential capacity of current PDE5 inhibitor drugs for repositioning in the treatment of brain tumors, notably glioblastoma multiforme (GBM). It has now been recognized that these drugs increase brain tumors permeability and enhance standard chemotherapeutics effectiveness. More importantly, studies have highlighted the promising antitumor functions of PDE5 inhibitors, e.g., triggering apoptosis, suppressing tumor cell growth and invasion, and reversing tumor microenvironment (TME) immunosuppression in the brain. However, contradictory reports have suggested a pro-oncogenic role for neuronal cyclic guanosine monophosphate (cGMP), indicating the beneficial function of PDE5 in the brain of GBM patients. Unfortunately, due to the inconsistent preclinical findings, only a few clinical trials are evaluating the therapeutic value of PDE5 inhibitors in GBM treatment. Accordingly, additional studies should be conducted to shed light on the precise effect of PDE5 inhibitors in GBM biology regarding the existing molecular heterogeneities among individuals. Here, we highlighted and discussed the previously investigated mechanisms underlying the impacts of PDE5 inhibitors in cancers, focusing on GBM to provide an overview of current knowledge necessary for future studies.

Phosphodiesterase type 5 inhibitors use and risk of colorectal cancer: a systematic review and meta-analysis

BACKGROUND

Experimental evidence has revealed that phosphodiesterase five inhibitors (PDE5is) increase epithelial barrier function and suppress intestinal carcinogenesis. Few epidemiological studies have investigated the role of PDE5i in increasing the risk of colorectal cancer (CRC); however, these studies have proffered varying conclusions. We therefore aimed to perform a comprehensive review and meta-analysis to investigate whether PDE5i use is associated with the incidence of CRC.

METHODS

Databases, namely, PubMed, Scopus, Embase, and Web of Science, were used for literature search. Observational studies (published until January 31, 2021) that assessed the association of PDE5i use with CRC incidence were considered. Pooled relative risk (RR) estimates and corresponding 95% confidence intervals (CIs) were calculated using the DerSimonian-Laird random-effects model.

RESULTS

We identified four retrospective studies that involved 965,044 participants and 3,518 CRC cases detected during a mean follow-up of 12.7 years. Pooled results indicated a significantly reduced CRC risk among all PDE5i users (RR, 0.85; 95% CI, 0.76-0.95; P = 0.004, I² = 63%). Moreover, continuous use of PDE5i was associated with a significantly reduced risk of CRC (RR, 0.63; 95% CI, 0.59-0.68; P < 0.001, I² = 0.0%). However, the type of PDE5i exhibited no association with the risk of CRC (RR, 1.00; 95% CI, 0.98-1.02; I² = 84.7%).

CONCLUSION

Our findings suggest that continuous use of PDE5i was associated with a significantly reduced risk of CRC development. Future studies with a longitudinal design and adequate control of confounding factors are required to clarify whether a longer duration of PDE5i use alters the risk of CRC.

Therapeutic targeting of 3',5'-cyclic nucleotide phosphodiesterases: inhibition and beyond

Phosphodiesterases (PDEs), enzymes that degrade 3',5'-cyclic nucleotides, are being pursued as therapeutic targets for several diseases, including those affecting the nervous system, the cardiovascular system, fertility, immunity, cancer and metabolism. Clinical development programmes have focused exclusively on catalytic inhibition, which continues to be a strong focus of ongoing drug discovery efforts. However, emerging evidence supports novel strategies to therapeutically target PDE function, including enhancing catalytic activity, normalizing altered compartmentalization and modulating post-translational modifications, as well as the potential use of PDEs as disease biomarkers. Importantly, a more refined appreciation of the intramolecular mechanisms regulating PDE function and trafficking is emerging, making these pioneering drug discovery efforts tractable.