Nitrosative stress in rotated three-dimensional colorectal carcinoma cell cultures induces microtubule depolymerization and apoptosis.

Malignant cells undergo anoikis as they encounter fluid shear stress during transit to a metastatic site. We postulated that intracellular nitric oxide (NO) contributes to this cell death by comparing the growth of human colorectal carcinoma cells in low fluid shear stress rotated three-dimensional (Rotated 3-D) cultures with growth in static three-dimensional (Static 3-D) cultures on nonadherent surfaces and with two-dimensional monolayer (Monolayer 2-D) cultures. NO, loss of microtubules, and apoptosis increased significantly in Rotated 3-D cultures within 10 min and persisted at 24 h, whereas inhibition of NO synthase decreased apoptosis and intracellular NO and prevented tubulin degradation. Thus, fluid shear stress and three-dimensional growth increases NO synthase and NO to cause tubulin breakdown and induce anoikis. Intracellular NO in malignant cells entering the circulation may be a novel target for metastasis by colorectal carcinoma.