Namely, initial papers on the potential of THBS1 and CTSD signature in prostate cancer were published in 2017 [460], 2019 [461], and 2020 [462] and were based on the earlier analyses of the serum proteome in metastatic castration-resistant prostate cancer patients and the PTEN conditional knockout mouse model [463,464]. Here, CTSD is linked to prostate cancer.