As a small actin-binding protein upregulated in highly metastatic prostate cancer cells, thymosin β15 (Tβ15) has shown promise as a diagnostic marker for human prostate cancer. In some tissue-based assays, Tβ15 has been suggested to be applied in increasing the accuracy of diagnosis and identifying patients at risk of recurrence. If Tβ15 which is sensitive to potential aggressiveness of the tumour can be used clinically to improve both the sensitivity and speciﬁcity of prostate cancer diagnosis, a surgery can be operated before metastases are established, offering patient with organ-confined disease an excellent chance for cure .
Previous studies have demonstrated that Tβ15 is expressed in highly motile, highly metastatic variants, but not in poorly motile, weakly metastatic variants. As a member of the thymosin β family, Tβ15 belongs to a highly conserved multigene family of 5 kDa proteins that can bind to monomeric G-actin in a 1:1 complex. Like thymosin β4 and β10, Tβ15 affect actin polymerization and influence cell motility, a critical component of the metastatic process. It also appears to regulate cell motility as transfection of antisense Tβ15 into rat prostatic carcinoma cells can signiﬁcantly reduce stimulated cell migration. Used in situ hybridization and immunostaining, Tβ15 has been shown expressed in advanced human prostate cancer specimens but not in normal human prostate, which suggests Tβ15 can be used as a potential marker for prostate carcinoma progression.
The most dangerous property of cancer is its ability to metastasize, since most cancer mortality results from this process. When the tumor extravasation out of its original location occurred, it can grow at sites distant from the original tumor. Tβ15 used to have utility as a marker that can predict outcomes among patients with mid-grade prostate cancer from biopsy samples taken at the time of diagnosis. But this technique may underestimate the amount and grade of tumor, because biopsies capture only a small sample of the total prostate tissue. Therefore, our considerable efforts have been made to increase the value of Tβ15 as a prostate cancer biomarker by developing a quantitative assay and attempting to detect this protein in body fluids that can be easily and noninvasively collected and analyzed.
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