Prostate cancer (PCa) is one of the most common types of cancer and the fifth leading cause of death among men worldwide. The tools for diagnosing PCa have limited value, and to improve correct diagnosis there is a need for markers that can contribute to a more precise diagnosis, which would lead to proper treatment of only those patients who need it. Micro RNA (miRNA) plays a key role in the development of cancer and is therefore a potential marker for PCa. Next-generation sequencing was used to discover differences in miRNA expression between serum samples from PCa patients and healthy controls, and the results were validated by quantitative real-time polymerase chain reaction. Detection of the miRNA of interest was attempted in prostate tissue by in situ hybridization. All samples were collected in collaboration with Biobank1 . By miRNA sequencing of serum samples, significant expression of some miRNAs in patients with PCa and healthy controls was detected. This study showed that miR-148a-3p is upregulated in men with PCa, and the miRNA is differentially expressed in PCa patients compared to healthy controls. The results also showed that miR-148a-3p is located in prostate tissue.

Sampling of prostate tissue (n = 97) was performed in conjunction with planned radical prostatectomies, in collaboration with Biobank1 Ò. The tissue used in this study was collected during the period 2003-2016, quickly frozen, and kept at-80°C until assayed in 2018. RNA extraction was performed with two different protocols (miRNeasy and mirVanaÔ), and RNA quality was determined by measuring the RNA Integrity Number (RIN). The level of isoprostanes is widely recognized as a specific indicator of lipid peroxidation both in vitro and in vivo. The level of 8-isoprostane was measured because it is the main oxidation product of arachidonic acid, the most abundant phospholipid fatty acid. The level of 8-isoprostane was measured using enzyme immunoassay. There was no statistically significant difference in yield between the samples isolated with the mirVana protocol compared to the miRNeasy protocol. Average RIN was 2.8 units higher with the mirVana extraction protocol compared to the miRNeasy protocol (p < 0.001). For miRNeasy extractions, RINs were 7.1 for prostatectomies in 2005-2007 and 6.2 for those in 2018 (p < 0.001). For mirVana extractions, the difference in RIN score between the two groups regarding years of collection was not statistically significant. There was no significant increase in the levels of 8-isoprostane between the 2005-2007 samples and the 2018. The conclusion is that there is no oxidation of phospholipids with increasing storage time up to 15 years.