Quantifying Mucin 2 in LS174T Cells

The content of mucin 2 in the intracellular and cell supernatants was measured using the periodic acid-Schiff (PAS) assay. The PAS assay in LS174T cells used a previously reported method.^{28 (link)} In brief, LS174T cells (∼2 × 10⁶ cells) were disrupted in PBS using sonication (VCX105; Sonics, Newtown, CT, USA) to obtain soluble proteins. Protein concentration was determined using a BCA protein assay kit. Cellular soluble fractions and culture medium were incubated with 0.1% periodic acid (Sigma-Aldrich) for 2 h at 37°C. Next, the Schiff reagent (Sigma-Aldrich) was added and incubated for 30 min at 37°C. The OD of the resulting solution at 550 nm wavelength was taken as a measure of the amount of PAS-positive product present. The PAS OD value was expressed as the fold change relative to the mean value of the control sample.