**2. Materials and methods**

#### **2.1 Collection of samples**

Blood samples of 80 colon cancer patients (aged 40–80 years) who attend the Teaching Oncology Hospital at the City of Medicine and the National Center for Oncology, Baghdad for the period (18-2-2018 to 28-2-2019), were obtained.

A total of 50 blood samples were collected from apparently healthy individuals as a control group (aged 40–80 years). The samples were collected by drawing blood from the vein (5 mL) using a syringe and placing the blood in a gel tube.

The tubes were placed in the centrifuge at 1252 g for 10 minutes to obtain serum. The serum was kept by Eppendorf tube in deep-freeze at 20°C until testing.

#### **2.2 Measuring the LOX activity in blood serum**

The method of measuring the activity of the LOX enzyme [24] is based on stimulating the oxygen reaction with the unsaturated fatty acids containing (cis, cis 1.4-pentadiene). It consists of a sequential system of double bonds that increase absorption at a wavelength of 234 nm where the absorption intensity is directly proportional to the concentration of the enzyme [25]. The unit of enzyme is defined as the amount of enzyme that changes in absorbance by 0.001 / sec at wavelength 234 nm under ideal conditions.

#### **2.3 Estimation protein concentration**

The biuret method was used to estimate the concentration of the protein in the samples [26].

#### **2.4 Separation and purification of LOX from serum patients of colon cancer**

LOX is purified using the following steps:
