Figure 6.

Cells derived from tumor spheroids are more migratory than monolayer cells. (A) MDA-MB-231 spheroid stained against the hypoxia marker pimonidazole. Bar is 100 μm, original magnification is 200 x. (B) mRNA expression of PERK, ATF4 and LAMP3 in MDA-MB-231 monolayers compared to cells grown as spheroids. Migration of monolayer cells compared to cell initially grown as a spheroid in a transwell assay (C) during 24 hours and a gap closure assay (D) during 16 hours in standard cell culture medium. Spheroids were disintegrated into a single-cell suspension prior to the start of the assay. Results are from two representative experiments with three replicates each. ATF4, activating transcription factor 4; LAMP3, lysosomal-associated membrane protein 3; PERK, PKR-like endoplasmic reticulum kinase.