Similarly, both the SPC-IGFIR and SPC-IGFIR-Akt2−/− lung tumors expressed high levels of genes that were highly expressed in normal human lung tissue and adenocarcinomas (gene cluster 1) and not genes highly expressed by small cell and carcinoid tumors (cluster 2) or squamous cell tumors (cluster 3) suggesting that murine tumors are adenocarcinomas (Figure 4 and [50]). Here, SFTPC is linked to carcinoid tumor.