Today, lung cancer is the leading cause of death in both men and women in industrialized countries, accounting for an estimated 28% of all cancer deaths in the United States. Non-small cell lung cancers (NSCLC) represent the majority of lung cancers and carry a poor prognosis with a median survival of less than 12 months. Most patients present with unresectable disease and current treatment options of chemotherapy and radiation are palliative at best. Therefore, new strategies are needed in the treatment of NSCLC in order to impact this disease. In this study, we are focusing on NSCLC models for examining distal signaling mechanisms that modulate the chemotherapy sensitivity, generation, and maintenance of NSCLC cells/tumors. Specifically, this grant application focuses on the survival/oncogenic signaling pathways activated by caspase 9b. The expression of caspase 9b is regulated by alternative splicing via the inclusion or exclusion of a four exon cassette (exons 3, 4, 5, and 6). Inclusion of this exon cassette into the mature transcript produces the pro- apoptotic caspase 9 (caspase 9a) while the exclusion produces the anti-apoptotic and survival signaling factor, caspase 9b. Studies from our laboratory have demonstrated that NSCLC tumors present with a dysregulated (e.g. low) ratio of caspase 9/caspase 9b analogous to an anti-apoptotic/chemotherapy resistance phenotype. Subsequent studies by our laboratory demonstrated that the alternative splicing of caspase 9 had important functions in the anchorage-independent growth (AIG) of NSCLC cells, AIG induced by oncogenic mutation in non-transformed human bronchial epithelial cells, and chemotherapy sensitivity (e.g. cisplatinum and paclitaxel). Mechanistically, our laboratory identified an exonic splicing silencer (C9/E3-ESS) in exon 3 that regulates the inclusion of the exon 3, 4, 5, and 6 cassette of caspase 9 pre-mRNA. hnRNP L was shown to associate with this RNA cis-element, repress the inclusion of the exon cassette, and induce caspase 9b expression. Importantly, phosphorylation of hnRNP L on ser52 (observed only in transformed cells) was required for repression of the exon 3,4,5,6 cassette. Lastly, ser52 phosphorylation of hnRNP L was shown as a required mediator of the tumorigenic capacity of NSCLC cells via the alternative splicing of caspase 9. These key mechanisms are specific to transformed cells, translatable to >70% of NSCLCs, and at an extreme distal point in oncogenic pathways. Therefore, these distal mechanisms are plausible and highly desired targets for the development of new anti-cancer therapeutics. The proposed studies will determine the mechanisms and cell signaling pathways regulated by the survival product of caspase 9 RNA splicing, caspase 9b. These studies will also examine naturally occurring tumor suppression pathways (e.g. sphingolipid pathways) that block the production of caspase 9b, and thereby inhibit the growth of NSCLC tumors. Furthermore, we are proposing pre-clinical studies to determine whether the specific targeting of caspase 9b is effective for treating NSCLC by enhancing the effectiveness of current chemotherapeutic agents used in the clinic (e.g. cisplatinum and paclitaxel).
Cancer is the second leading cause of death among US veterans, and lung cancer is associated with the greatest mortality in these patients. Non-small cell lung cancers (NSCLC) represent the majority of lung cancers and carry a poor prognosis with a median survival of less than 12 months. Most patients present with unresectable disease, and current treatment options of chemotherapy and radiation are palliative at best. Our laboratory has identified key mechanisms specific to cancer cells and translatable to >70% of NSCLCs, which are plausible and highly desired targets for the development of new anti-cancer therapeutics. This grant application explores these cellular mechanisms in depth with the goal of developing new therapeutics to combat NSCLC, and thereby, aid US Veterans.
|Qi, Hui; Priyadarsini, Shrestha; Nicholas, Sarah E et al. (2017) Analysis of sphingolipids in human corneal fibroblasts from normal and keratoconus patients. J Lipid Res 58:636-648|
|Stephenson, Daniel J; Hoeferlin, L Alexis; Chalfant, Charles E (2017) Lipidomics in translational research and the clinical significance of lipid-based biomarkers. Transl Res 189:13-29|
|Contaifer Jr, Daniel; Carl, Daniel E; Warncke, Urszula Osinska et al. (2017) Unsupervised analysis of combined lipid and coagulation data reveals coagulopathy subtypes among dialysis patients. J Lipid Res 58:586-599|
|DeLigio, James T; Lin, Grace; Chalfant, Charles E et al. (2017) Splice variants of cytosolic polyadenylation element-binding protein 2 (CPEB2) differentially regulate pathways linked to cancer metastasis. J Biol Chem 292:17909-17918|
|Stiles, Megan; Qi, Hui; Sun, Eleanor et al. (2016) Sphingolipid profile alters in retinal dystrophic P23H-1 rats and systemic FTY720 can delay retinal degeneration. J Lipid Res 57:818-31|
|Shapiro, Brian A; Vu, Ngoc T; Shultz, Michael D et al. (2016) Melanoma Differentiation-associated Gene 7/IL-24 Exerts Cytotoxic Effects by Altering the Alternative Splicing of Bcl-x Pre-mRNA via the SRC/PKC? Signaling Axis. J Biol Chem 291:21669-21681|
|Priyadarsini, Shrestha; McKay, Tina B; Sarker-Nag, Akhee et al. (2016) Complete metabolome and lipidome analysis reveals novel biomarkers in the human diabetic corneal stroma. Exp Eye Res 153:90-100|
|Vu, Ngoc T; Park, Margaret A; Shultz, Michael D et al. (2016) Caspase-9b Interacts Directly with cIAP1 to Drive Agonist-Independent Activation of NF-?B and Lung Tumorigenesis. Cancer Res 76:2977-89|
|Barbour, Suzanne E; Nguyen, Phuong T; Park, Margaret et al. (2015) Group VIA Phospholipase A2 (iPLA2?) Modulates Bcl-x 5'-Splice Site Selection and Suppresses Anti-apoptotic Bcl-x(L) in ?-Cells. J Biol Chem 290:11021-31|
|Al-Husseini, Aysar; Wijesinghe, Dayanjan S; Farkas, Laszlo et al. (2015) Increased eicosanoid levels in the Sugen/chronic hypoxia model of severe pulmonary hypertension. PLoS One 10:e0120157|
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