# Increased levels of thymidine kinase 1 in malignant cell-derived extracellular vesicles

## TL;DR

This study shows that thymidine kinase 1 (TK1) levels are higher in extracellular vesicles from prostate cancer cells compared to normal cells, suggesting its potential as a biomarker for cancer aggressiveness.

## Contribution

The study demonstrates that TK1 activity in extracellular vesicles is elevated in malignant prostate cancer cells, offering a new potential diagnostic tool.

## Key findings

- TK1 enzyme activity is higher in EVs from prostate cancer cell lines compared to normal cells.
- The highest TK1 activity was observed in EVs from the most aggressive cancer cell line.
- Measuring TK1 in EVs may help assess prostate cancer aggressiveness.

## Abstract

Extracellular vesicles (EVs), whose main subtypes are exosomes, microparticles, and apoptotic bodies, are secreted by all cells and harbor biomolecules such as DNA, RNA, and proteins. They function as intercellular messengers and, depending on their cargo, may have multiple roles in cancer development. Thymidine kinase 1 (TK1) is a cell cycle-dependent enzyme used as a biomarker for cell proliferation. TK1 is usually elevated in cancer patients' serum, making the enzyme a valuable tumor proliferation biomarker that strongly correlates with cancer stage and metastatic capabilities. Here, we investigated the presence of TK1 in EVs derived from three prostate cancer cell lines with various p53 mutation statuses (LNCaP, PC3, and DU145), EVs from the normal prostate epithelial cell line RWPE-1 and EVs isolated from human seminal fluid (prostasomes). We measured the TK1 activity by a real-time assay for these EVs. We demonstrated that the TK1 enzyme activity is higher in EVs derived from the malignant cell lines, with the highest activity from cells deriving from the most aggressive cancer, compared to the prostasomes and RWPE-1 EVs. The measurement of TK1 activity in EVs may be essential in future prostate cancer studies.

•Thymidine kinase 1 (TK1) serves as a significant biomarker for cell proliferation and cancer progression, with elevated levels associated with higher metastasis level.•TK1 enzyme activity is higher in small extracellular vesicles (sEV) derived from prostate cancer cell lines compared to the normal prostate epithelial cell line and prostasome.•Measuring TK1 enzyme activity in sEV holds a potential as a diagnostic routine for evaluating prostate cancer aggressiveness.

Thymidine kinase 1 (TK1) serves as a significant biomarker for cell proliferation and cancer progression, with elevated levels associated with higher metastasis level.

TK1 enzyme activity is higher in small extracellular vesicles (sEV) derived from prostate cancer cell lines compared to the normal prostate epithelial cell line and prostasome.

Measuring TK1 enzyme activity in sEV holds a potential as a diagnostic routine for evaluating prostate cancer aggressiveness.