Figure 3. The investigated key mediators of apoptosis and cell cycle regulation are shown graphically.

Carcinoids use the CDK4/6 complex in combination with CCND1 to drive cell cycle progression. Instead, carcinomas showed a downregulation of these cell cycle mediators and additionally, the inhibitor of this section, CDKN2A, was increased in carcinomas. Carcinomas showed higher expression of CDK2 and CCNE1 indicating that cell cycle progression is driven by this complex. Furthermore, carcinomas showed elevated expression of BCL2, an antagonist of apoptosis, which increased over BAX expression leading to insensitivity to apoptosis.