Fig. 1.

Interplay between signaling and metabolic pathways in small cell lung carcinoma. The PI3K/Akt/mTOR pathway is frequently affected in SCLC. The mTOR kinase forms the catalytic subunit of two distinct multiprotein complexes, mTORC1 and mTORC2. The mTOR complexes regulate metabolic processes: mTORC1 promotes protein and nucleotide synthesis, whereas lipid metabolism can be influenced by both mTORC1 and mTORC2 [16]. Besides the mTOR pathway, MYC alterations can also affect bioenergetic processes, such as glycolysis, nucleotide synthesis, and glutamine metabolism [26]. In contrast, metabolic changes can influence the activity of signaling pathways. mTORC1 is inhibited under energetic stress or hypoxia; additionally, its activity is regulated by the availability of certain amino acids, such as leucine and arginine [27]