Review Article An Overview of Current Alternative Models for Use in the Context of Prostate Cancer Research Elisabete Nascimento-Gonc ¸alves 1,2,3 , Rita Ferreira 3 , Paula A. Oliveira 1,2 and Bruno Jorge Antunes Colac ¸o 2,4 Abstract Prostate cancer is one of the most commonly diagnosed cancers worldwide, particularly in elderly populations. To mitigate the expected increase in prostate cancer-related morbidity and mortality as a result of an expanding aged population, safer and more effective therapeutics are required. To this end, plenty of research is focusing on the mechanisms underlying cancer initiation and development, the metastatic process and on the discovery of new therapies. While animal models are used (mainly rats and mice) for the study of prostate cancer, alternative models and methods are increasingly being considered to replace, or at least reduce, the number of animals used in this particular field of research. In this review, we cover some of the alternative models that are currently available for use in the study of prostate cancer, including: mathematical models; 2-D and 3-D cell cultures; microfluidic devices; the chicken egg chorioallantoic membrane-based model; and zebrafish embryo-based models. The main advantages and limitations, as well as some examples of applications, are given for each type of model. According to our analysis, immortalised cell lines are still the most commonly used models in the field of prostate cancer research. However, the use of alternative models for prostate cancer research will likely become more prevalent in the coming years partly because of the increasing societal pressure to reduce the numbers of laboratory animals. In this context, the development and dissemination of effective non-animal alternative models assumes particular relevance and will be instrumental in leveraging their success. Taking these per- spectives into account, we believe that technological advances will lead to more effective cell culture systems, namely 3-D cultures or organ-on-a-chip devices, which can be used to replace animal-based models in prostate cancer research. Keywords alternative methods, alternative models, animal experimentation, cancer, cancer models, prostate, Three Rs Introduction In 1959, Russell and Burch published the book, The Prin- ciples of Humane Experimental Technique, in which they formulated the Three Rs (Replacement, Reduction and Refinement) to serve as guiding principles for animal experimentation. 1 Since then, many organisations have contributed to disseminate the Three Rs and ensure that they are adhered to whenever animal experiments are per- formed. For example, the UK’s National Centre for the Replacement, Refinement & Reduction of Animals in Research built on those principles to provide contemporary scientific standards and to promote more ethical procedures on laboratory animals. 2 In this context, the use of less sen- tient in vivo models (such as invertebrates, nematode worms or immature forms of vertebrates) was proposed, in order to avoid the use of large animal models, particu- larly mammals. 3 In the European Union (EU), animal research is regu- lated under Directive 2010/63/EU, which came into force 1 Department of Veterinary Sciences, University of Tr´ as-os-Montes and Alto Douro (UTAD), Vila Real, Portugal 2 Center for the Research and Technology of Agro-Environmental and Biological Sciences, University of Tr´ as-os-Montes and Alto Douro, Vila Real, Portugal 3 Organic Chemistry, Natural Products and Foodstuffs (QOPNA/LAQV), Department of Chemistry, University of Aveiro, Aveiro, Portugal 4 Department of Zootechnics, University of Tr´ as-os-Montes and Alto Douro (UTAD), Vila Real, Portugal Corresponding author: Bruno Jorge Antunes Colac ¸o, Center for the Research and Technology of Agro-Environmental and Biological Sciences, Department of Zootechnics, University of Tr´ as-os-Montes and Alto Douro, 5001-911 Vila Real, Portugal. Email: bcolaco@utad.pt Alternatives to Laboratory Animals 1–12 ª The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0261192920929701 journals.sagepub.com/home/atl