To minimize artefacts that may arise from long-term culture of SCLC cell lines we employed low-passage (passage 510), primary murine SCLC (mSCLC) cell lines, established from mSCLC tumors isolated from the GEM model of SCLC consisting of theRbL/L;p53L/L(RP) allelic genotype (Meuwissen et al

To minimize artefacts that may arise from long-term culture of SCLC cell lines we employed low-passage (passage 510), primary murine SCLC (mSCLC) cell lines, established from mSCLC tumors isolated from the GEM model of SCLC consisting of theRbL/L;p53L/L(RP) allelic genotype (Meuwissen et al., 2003) (Figure 1A). to the lack of advancement in SCLC therapeutics (Sato et al., 2007;William and Glisson, 2011). In contrast to non-small cell lung cancer (NSCLC) where therapeutics designed to target known oncogenic drivers such as EGFR and ALK have been extremely effective; the poor understanding of SCLC disease etiology has precluded the identification of therapeutic targets and effective treatments (William and Glisson, 2011). Recent efforts to collect and sequence SCLC tissues have revealed that these tumors display a strikingly high rate of protein-changing DBPR108 mutations (Peifer et al., 2012;Rudin et al., 2012); however, paradoxically, no targetable mutations have been identified to guide therapeutic decisions for SCLC, and efficient treatment paradigms are urgently needed. SCLC is defined by the near ubiquitous inactivation of bothP53andRB(Peifer et al., DBPR108 2012;Rudin et al., 2012;Sato et al., 2007); however, recent reports indicate that the cell of origin is equally important for the development of SCLC disease. Conditional inactivation ofP53andRBin the adult mouse lung, using a genetically-engineered mouse (GEM) model, is sufficient to develop murine SCLC resembling human disease (Meuwissen et al., 2003). Importantly though, SCLC is only firmly established if P53 and RB is inactivated in the small population of pulmonary neuroendocrine cells (PNEC) (Sutherland et al., 2011). In contrast, P53 and RB loss confined to the abundant non-neuroendocrine cell population in the murine lungs cause low penetrance of SCLC and a significant increase in disease latency (Park et al., 2011;Sutherland et al., 2011). Thus, the PNEC is the major cell of origin of SCLC, suggesting that neuroendocrine pathways collaborate with P53 and RB loss to initiate and drive SCLC tumorigenesis. SCLC cells (as well as PNECs) exhibit high, sustained expression of many neuroendocrine genes, in particular transcription factors that regulate neuroendocrine development and differentiation in various tissues (Pedersen et al., 2003;Reynolds et al., 2000;Travis, 2009). Achaete-scute homolog 1 (ASCL1) which is a master regulator of neuroendocrine differentiation in lung development (Borges et al., 1997;Ito et al., 2000) and has been shown to regulate tumor-initiating capacity and survival pathways in SCLC (Jiang et Rabbit polyclonal to LGALS13 al., 2009;Osada et al., 2005), hence underscoring the interplay between neuroendocrine signaling and SCLC pathogenesis. Furthermore, the lineage-specific transcription factor NEUROD1, has been reported to govern survival pathways in SCLC cells (Osborne et al., 2013). Further, SCLC cells exhibit various chromosomal and focal amplifications leading to increased target gene expression and possible gain-of-function. Fifty to eighty DBPR108 percent of SCLC tumors exhibit mutually exclusive amplification of the proto-oncogenesMYC,MYCN, orMYCL(Brennan et al., 1991;Huijbers et al., 2014;Johnson et al., 1987;Kim et al., 2006;Peifer et al., 2012;Rudin et al., 2012;Voortman et al., 2010).MYCis misregulated in the majority of human cancers leading to uncontrolled proliferation possible through augmentation of existing gene expression programs (Lin et al., 2012). In contrast toMYC,MYCNandMYCLmisregulation occurs only in high-risk cancers of neuroendocrine origin such as SCLC (Huijbers et al., 2014;Johnson et al., 1987;McFadden et al., 2014), neuroblastoma (MYCN) (Huang and Weiss, 2013), and medulloblastoma (MYCN,MYCL) (Northcott et al., 2012). Moreover, many SCLC tumors have focal amplifications or increased expression of SOX-family genes (Voortman et al., 2010), includingSOX2, which is DBPR108 critical for lung development and self-renewal.SOX2amplification and increased expression levels in tumors correlates with accelerated disease stage and silencing of SOX2 inhibits DBPR108 growth of SCLC cells (Rudin et al., 2012). Thus, misregulated and amplified lineage-specific and proto-oncogenic transcription factors appear to govern SCLC initiation and disease evolution and downregulation of such factors could.