AMPK Knockout Impairs the Formation of Three-Dimensional Spheroids.

AMP-activated protein kinase (AMPK) is an important regulator of cellular energy homeostasis, and AMPK contributes to cell growth, apoptosis, and autophagy. Although most cell studies have been performed using two-dimensional (2D) cell culture, recent studies have demonstrated that the three-dimensional (3D) spheroid technique is helpful in various cell research fields, such as tumor biology, due to its resemblance to the 3D tissue structure. However, the role of AMPK in 3D spheroid formation has not been characterized clearly. This study used the AMPK knockout cell line to examine the role of AMPK in 3D spheroid formation and is the first report describing the generation of 3D spheroids using AMPK knockout cells. While control cells produced round spheroids with a similar length-to-width ratio, AMPK knockout produced an oval shape with a more significant length-to-width ratio. We demonstrate that AMPK knockout spheroids contain significantly more prominent lysosomes in each cell, indicating that autophagic flux is impaired in 3D spheroids. Finally, flow cytometry analysis showed that AMPK knockout spheroids contain more apoptotic cells than control cells. These results indicate that AMPK is required for efficient 3D spheroid formation.