TP53 and small cell lung carcinoma: A parallel study indicated that the excessive expression of Fgfr1K656E, which represents a constitutively active form of FGFR1, in NE cells that express CGRPPOS (calcitonin gene-related peptide-positive; cells of the origin of SCLC) and lack functional Rb/TP53 signaling, leads to the suppression of tumor initiation.