The contribution of FGFR1 to the development of SCLC is dictated by the cell-of-origin

Enhanced RAF/MEK/ERK signaling plays an obligatory role in many different types of cancer. Although genetic lesions promoting its aberrant activation are found in lung adenocarcinoma (LADC), the biological role of this pathway is not well documented in small cell lung cancer (SCLC). Here we explored the role of this pathway in SCLC and the broader class of tumors with neuroendocrine (NE) differentiation by introducing a constitutively active form of Fibroblast growth factor receptor 1 (Fgfr1) together with biallelic inactivation of Rb1 and Trp53 in mouse lung. Our data show that FGFR1 expression primarily results in LADC but also in NE tumors depending on the cell-of-origin. FGFR1 activation selectively promoted NE bronchial lesions in a novel lung cell subpopulation, whereas it impaired progression of typical central SCLC initiated from CGRP-expressing NE cells, which is believed to be the most prominent cell-of-origin of SCLC. Strikingly, FGFR1 activation was well tolerated by K14-expressing cells that were efficiently transformed into SCLC and other NE lesions. Taken together, our results indicate that FGFR1 can serve either as driver or suppressor of distinct lung cancer subtypes depending on the cell-of-origin, which should be taken into account when considering FGFR1 as a therapeutic target. Overall design: RNAseq samples were derived from 24 mice that developed SCLC. The role of the MAPK-pathway was assessed introducing a constitutively active form of Fibroblast growth factor receptor 1 (Fgfr1) together with biallelic inactivation of Rb1 and Trp53 in mouse lung. Tumors from Fgfr1 mice were compared to tumors from mycl and control mice. Furthermore, multiple adenovirus were tested (Ad5-CMV-Cre, Ad5-CGRP-Cre, Ad5-SPC-Cre). These combinations resulted in differences in histology and location of the tumors in mice.