# Distance-Dependent Distribution of Biomarkers in Colorectal Cancer Tissues: In Vivo Study

## TL;DR

This study shows how certain biomarkers are distributed differently in colorectal cancer tissues compared to surrounding healthy tissue, suggesting their role in cancer progression.

## Contribution

The study reveals spatial heterogeneity in biomarker expression in CRC tissues, particularly for cathepsin B and actin dynamics.

## Key findings

- Cathepsin B activity is significantly higher at the tumor center and decreases with distance.
- F-actin and T-actin levels are elevated near the tumor core.
- Actin polymerization states shift significantly based on proximity to the tumor.

## Abstract

Colorectal cancer (CRC) is among the most prevalent and deadly malignancies worldwide. Despite advancements in screening and treatment, its aggressive progression and tendency to metastasize remain major challenges. Biomarkers such as cathepsins B and D, actin isoforms, and cysteine protease inhibitors may influence tumor invasion and metastasis. However, little is known about their spatial distribution in tumor versus surrounding tissue. This study aimed to evaluate the location-dependent expression of selected biomarkers in CRC tissue to better understand their role in cancer progression. Tissue samples were obtained intraoperatively from 37 CRC patients at three locations: the tumor center, and 2 cm and 5 cm from the tumor margin. The activity and concentrations of cathepsins B and D, anti-papain activity, and actin fractions (globular [G-], filamentous [F-], and total actin [T-actin]) were measured using biochemical and spectrophotometric assays. Statistical analyses included ANOVA, MANOVA, and non-parametric tests, with significance set at p < 0.05. Cathepsin B activity was significantly elevated at the tumor center and decreased with distance from the tumor (p < 0.001). F-actin and T-actin levels followed a similar pattern, with significantly higher values near the tumor core (p < 0.05). Differences in G-actin were less pronounced. No significant spatial variation was found for cathepsin D, or anti-papain activity. The G-actin/T-actin and F-actin/G-actin ratios revealed significant shifts in actin polymerization states depending on the distance from the tumor. This study demonstrates spatial heterogeneity in the expression of key biomarkers in CRC tissues. Elevated levels of cathepsin B and altered actin dynamics in tumor regions suggest their involvement in local invasion and progression.