ALDH1A3 and neoplasm: In contrast, the ALDH1A3 CSC marker is markedly elevated in both the 3D spheroid core (24-fold; p < 0.001) and 3D spheroid periphery (11-fold; p < 0.001), as shown in Fig. 3d, suggesting that the 3D architecture and resultant cell-cell interactions that occur within tumor spheroids also translates to an increase in CSC content and presumably increased chemotherapeutic resistance.