ABSTRACT
The landscape of advanced non-small lung cancer (NSCLC) therapies has rapidly been evolving beyond chemotherapy over the last few years. The discovery of oncogenic driver mutations has led to new ways in classifying NSCLC as well as offered novel therapeutic targets for anticancer therapy. Targets such as epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) gene rearrangements have successfully been targeted with appropriate tyrosine kinase inhibitors (TKIs). Other driver mutations such as ROS, MET, RET, BRAF have also been investigated with targeted agents with some success in the early phase clinical setting. Novel strategies in the field of immune-oncology have also led to the development of inhibitors of cytotoxic T lymphocyte antigen-4 (CTLA-4) and programmed death-1 receptor (PD-1), which are important pathways in allowing cancer cells to escape detection by the immune system. These inhibitors have been successfully tried in NSCLC and also now bring the exciting possibility of long term responses in advanced NSCLC. In this review recent data on novel targets and therapeutic strategies and their future prospects are discussed.
ABSTRACT
BACKGROUND: Desmoplastic small round cell tumor (DSRCT) is characterized by the presence of a fusion protein EWS/WT1, arising from the t (11;22) (p13;q12) translocation. Here we examine the oncogenic properties of two splice variants of EWS/WT1, EWS/WT1-KTS and EWS/WT1 + KTS. METHODS: We over-expressed both EWS/WT1 variants in murine embryonic fibroblasts (MEFs) of wild-type, p53+/- and p53-/- backgrounds and measured effects on cell-proliferation, anchorage-independent growth, clonogenicity after serum withdrawal, and sensitivity to cytotoxic drugs and gamma irradiation in comparison to control cells. We examined gene expression profiles in cells expressing EWS/WT1. Finally we validated our key findings in a small series of DSRCT. RESULTS: Neither isoform of EWS/WT1 was sufficient to transform wild-type MEFs however the oncogenic potential of both was unmasked by p53 loss. Expression of EWS/WT1 in MEFs lacking at least one allele of p53 enhanced cell-proliferation, clonogenic survival and anchorage-independent growth. EWS/WT1 expression in wild-type MEFs conferred resistance to cell-cycle arrest after irradiation and daunorubicin induced apoptosis. We show DSRCT commonly have nuclear localization of p53, and copy-number amplification of MDM2/MDMX. Expression of either isoform of EWS/WT1 induced characteristic mRNA expression profiles. Gene-set enrichment analysis demonstrated enrichment of WNT pathway signatures in MEFs expressing EWS/WT1 + KTS. Wnt-activation was validated in cell lines with over-expression of EWS/WT1 and in DSRCT. CONCLUSION: In conclusion, we show both isoforms of EWS/WT1 have oncogenic potential in MEFs with loss of p53. In addition we provide the first link between EWS/WT1 and Wnt-pathway signaling. These data provide novel insights into the function of the EWS/WT1 fusion protein which characterize DSRCT.
Subject(s)
Desmoplastic Small Round Cell Tumor/metabolism , Fibroblasts/metabolism , Oncogene Proteins, Fusion/physiology , Tumor Suppressor Protein p53/genetics , Animals , Apoptosis , Cell Cycle Checkpoints , Cell Cycle Proteins , Cell Proliferation , Cell Survival/drug effects , Cells, Cultured , DNA Copy Number Variations , Daunorubicin/pharmacology , Drug Resistance, Neoplasm , Humans , Mice , Mice, Transgenic , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins/metabolism , Proto-Oncogene Proteins c-mdm2/genetics , Proto-Oncogene Proteins c-mdm2/metabolism , Radiation Tolerance , Transcriptome , Tumor Suppressor Protein p53/deficiency , Wnt Signaling PathwayABSTRACT
The basic helix-loop-helix transcription factor achaete-scute complex homologue 1 (ASCL1) is essential for the development of normal lung neuroendocrine cells as well as other endocrine and neural tissues. Small cell lung cancer (SCLC) and non-SCLC with neuroendocrine features express ASCL1, where the factor may play a role in the virulence and primitive neuroendocrine phenotype of these tumors. In this study, RNA interference knockdown of ASCL1 in cultured SCLC resulted in inhibition of soft agar clonogenic capacity and induction of apoptosis. cDNA microarray analyses bolstered by expression studies, flow cytometry, and chromatin immunoprecipitation identified two candidate stem cell marker genes, CD133 and aldehyde dehydrogenase 1A1 (ALDH1A1), to be directly regulated by ASCL1 in SCLC. In SCLC direct xenograft tumors, we detected a relatively abundant CD133(high)-ASCL1(high)-ALDH1(high) subpopulation with markedly enhanced tumorigenicity compared with cells with weak CD133 expression. Tumorigenicity in the CD133(high) subpopulation depended on continued ASCL1 expression. Whereas CD133(high) cells readily reconstituted the range of CD133 expression seen in the original xenograft tumor, CD133(low) cells could not. Our findings suggest that a broad range of SCLC cells has tumorigenic capacity rather than a small discrete population. Intrinsic tumor cell heterogeneity, including variation in key regulatory factors such as ASCL1, can modulate tumorigenicity in SCLC.
