Tumor xenograft and metastasis experiments

Twelve nude mice (male, 4 weeks, weight 16 ± 2 g) were randomly divided into two groups of six animals each. The 22Rv1 cells were suspended in PBS at a density of 1 × 10⁷/ml. Matrigel (Corning) was added to the cell suspension at a 1:1 ratio, and 150 μL of this mixture was subcutaneously injected into the axillae to induce tumor growth. Every 7 days, the tumors were measured with a caliper. Tumor volumes were calculated as follows: V_tumor = 0.5 × L × W², where L = length and W = width. After 4 weeks, the mice were sacrificed and their tumor sizes and weights were measured. In a separate experiment, equal numbers of luciferase-expressing 22Rv1 cells (2 × 10⁶/mL) and control or SIRT7-depleted 22Rv1 cells were injected into mouse tail veins. After 21 days, tumor metastasis was visualized with a bioluminescence-based IVIS (in vivo imaging system) (Caliper Life Sciences, Waltham, MA, USA).