Can levels of cathepsin X predict response to chemotherapy?

The study evaluated whether levels of cathepsin X can be used to predict if colorectal cancer patients would benefit from chemotherapy.

Colorectal cancer is the second leading cause of cancer-related death in Europe and the US. The availability of biomarkers (measurable indicators of a biologic state or condition; usually proteins) for selection of chemotherapy and prediction of treatment effectiveness may increase patient survival.

Cathepsin X is normally expressed in various cells of the immune system and regulates important processes such as growth, maturation and movement of immune cells. However, there is increasing evidence that cathepsin X is also involved in cancer. Higher-than-usual levels of cathepsin X are found in tumor and immune cells in some cancers, including prostate and gastric cancer. Therefore, cathepsin X may serve as a biomarker to predict the disease status and risk of death for colorectal cancer patients.

This study included 264 patients with primary rectal (39.4% of patients) or colon (36.7% patients with left-sided, 23.9% patients with right-sided) cancer and 77 healthy participants. Blood samples were collected from healthy participants and from cancer patients just before preoperative endoscopy (a flexible tube is inserted into the back passage to examine the intestine before surgery).

The average cathepsin X levels in colorectal cancer patients (23.4 ng/ml) did not significantly differ from levels in the healthy patients (18.8 ng/ml). However, in patients with stage I-III cancer who had high levels of cathepsin X and did not receive chemotherapy, there was a 3.13 fold increase in risk of mortality compared to those with low cathepsin X.

Total cathepsin X could be useful as a blood-based tumor marker that may allow prediction of patients who could benefit from chemotherapy.