Lung cancer is the leading cause of cancer-related death worldwide. Here we demonstrate that elevated expression of dopamine and cyclic adenosine monophosphate-regulated phosphoprotein, Mr 32000 (DARPP-32), and its truncated splice variant t-DARPP promote lung tumor growth, while abrogation of DARPP-32 expression in human non-small-cell lung cancer (NSCLC) cells reduces tumor growth in orthotopic mouse models. We observe a physical interaction between DARPP-32 and inhibitory kappa B kinase-α (IKKα) that promotes NSCLC cell migration through non-canonical nuclear factor kappa-light-chain-enhancer of activated B cells 2 (NF-κB2) signaling. Bioinformatics analysis of 513 lung adenocarcinoma patients reveals that elevated t-DARPP isoform expression is associated with poor overall survival. Histopathological investigation of 62 human lung adenocarcinoma tissues also shows that t-DARPP expression is elevated with increasing tumor (T) stage. Our data suggest that DARPP-32 isoforms serve as a negative prognostic marker associated with increasing stages of NSCLC and may represent a novel therapeutic target.

Significance CHARGE syndrome is a complex developmental disorder caused by mutations in CHD7 (chromodomain helicase DNA-binding protein-7). We identified Caenorhabditis elegans chd-7 in a screen for suppressors of dauer formation, an alternative larval stage that develops under harsh environmental conditions. We found chd-7 regulates tumor growth factor-β (TGF-β) signaling pathways both for dauer diapause and for development of the cuticle, a specialized extracellular matrix. In frog embryos, Chd7 promotes Col2a1 expression, which is necessary and sufficient to prevent CHARGE features. These studies establish a conserved role for Chd7 from worms to vertebrates in regulating the TGF-β signaling pathway. Genetic dissection of chd-7 ’s role in C. elegans may help to define the molecular and cellular events that contribute to CHARGE syndrome.

CHARGE syndrome is a complex developmental disorder caused by mutations in the chromodomain helicase DNA-binding protein7 (CHD7) and characterized by retarded growth and malformations in the heart and nervous system. However, despite the public health relevance of this disorder, relevant targets of CHD7 that relate to disease pathology are still poorly understood. Here we report that chd-7, the nematode ortholog of CHD7, is required for dauer morphogenesis, lifespan determination, and stress response. Genetic epistasis placed chd-7 in the TGF-β pathway. Consistent with our discoveries, we found chd-7 to be allelic to scd-3, a previously identified dauer suppressor from the TGF-β pathway. Interestingly, DAF-12 transcriptionally upregulated chd-7, which is necessary to repress daf-9 for execution of the dauer program. Transcriptomic analysis comparing chd-7 defective and normal dauers showed enrichment of collagen genes, consistent with a conserved role for the TGF-β pathway in expression of the extracellular matrix. To validate a conserved function for chd-7 in vertebrates, we used Xenopus laevis embryos, an established model to study craniofacial development. Morpholino mediated knockdown of Chd7 led to embryonic lethality, a reduction in col2a1 mRNA levels and craniofacial defects in tadpoles. Both lethality and malformations were partially rescued in Chd7-depleted embryos by over-expression of col2a1. We suggest that pathogenic features of CHARGE syndrome caused by Chd7 mutations, such as craniofacial malformations, result from the reduction of collagen levels. These studies establish C. elegans as an amenable animal model to study the etiology of the developmental defects associated with pathogenic Chd7.

We were pleased to see the three reports (1-3) and Research News article by Jean Marx (p. 963) in the 17 February issue that highlight the induction of the protein p21(WAF1) cyclin-dependent kinase (Cdk) inhibitor in myogenesis (1) and the high level of expression of p21(WAF1) in terminally differentiated tissues (2). These findings elegantly extend the findings published last fall in our papers "Induction of p21 (WAF1/CIP1) during differentiation" (4) and "Induction of differentiation in human promyelocytic HL-60 leukemia cells activates p21, WAF1/CIP1, expression in the absence of p53" (5). We had reported that multiple differentiation inducers caused immediate-early and sustained upregulation of p21 in many cell types through a p53-independent pathway. The report by Skapek et al. (3) demonstrating p21(WAF1) reversal of a cyclin DI-mediated differentiation block in muscle raises the hope that in some settings p21 (WAF1 )inducing agents may be anti-oncogenic. We would caution, however, that this strategy would be ineffective in settings in which p21(WAF1) induction is uncoupled from growth arrest. An example is our demonstration that deregulated c-myc expression is capable of uncoupling p21(WAF1) induction both from growth arrest and from differentiation (4).

Lung cancer is the leading cause of cancer-related death worldwide. In this study, we demonstrate that elevated expression of dopamine and cyclic adenosine monophosphate-regulated phosphoprotein, Mr 32000 (DARPP-32) and its truncated splice variant t-DARPP promotes lung tumor growth, while abrogation of DARPP-32 expression in human non-small cell lung cancer (NSCLC) cells reduces tumor growth in orthotopic mouse models. We observe a novel physical interaction between DARPP-32 and inhibitory kappa B kinase-α (IKKα) that promotes NSCLC cell migration through non-canonical nuclear factor kappa-light-chain-enhancer of activated B cells 2 (NF-κB2) signaling. Bioinformatics analysis of 513 lung adenocarcinoma patients reveals elevated t-DARPP isoform expression is associated with poor overall survival. Histopathological investigation of 62 human lung adenocarcinoma tissues also showed that t-DARPP expression is elevated with increasing tumor (T) stage. Our data suggest that DARPP-32 is a negative prognostic marker associated with increasing stages of NSCLC and may represent a novel therapeutic target. Citation Format: Sk. Kayum Alam, Matteo Astone, Ping Liu, Stephanie R. Hall, Abbygail M. Coyle, Erin N. Dankert, Dane K. Hoffman, Wei Zhang, Rui Kuang, Anja C. Roden, Aaron S. Mansfield, Luke H. Hoeppner. DARPP-32 and t-DARPP promote non-small cell lung cancer growth through regulation of IKKα-dependent cell migration and Akt/Erk-mediated cell survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5161.

Lung cancer is the deadliest and most frequently diagnosed type of tumor worldwide, with 1.6 million deaths reported annually. Non-small cell lung cancer (NSCLC) represents 85% of all lung cancer cases and carries a poor 5-year survival rate below 15%. Prognoses remain dismal due to the large number of patients diagnosed with advanced stage disease and the development of resistance to current therapies. A better understanding of acquired drug resistance will help to circumvent the progression of lung cancer and make significant strides in improving NSCLC patient treatment. Our recent work demonstrates that dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32) and its amino-terminally truncated splice variant (t-DARPP) promote lung tumor growth in orthotopic mouse models. IHC staining of 62 human lung adenocarcinoma tissues showed that t-DARPP expression is elevated with increasing tumor (T) staging score, which represents the size of the primary tumor and whether it has grown into nearby areas, as a metric of tumor progression and growth. Correspondingly, a computational biology analysis of 513 lung adenocarcinoma patients revealed upregulation of t-DARPP isoform expression correlates with advanced T stage and is associated with poor overall survival. We identified a novel physical interaction between DARPP-32 and inhibitory kappa B kinase-α (IKKα) that promotes NSCLC cell migration through activation of non-canonical NF-κB2 signaling. It has been shown that DARPP-32 overexpression inhibits gefitinib-induced apoptosis in gastric cancer and t-DARPP contributes to the trastuzumab resistance phenotype in breast cancer. Our recent findings suggest DARPP-32 and t-DARPP overexpression in NSCLC promotes resistance to specific molecular targeted inhibitors by enabling tumor cells to evade apoptosis via Akt- and Erk-dependent cell survival mechanisms. Current ongoing studies are focused on manipulating expression of DARPP-32 isoforms in lung tumor cells to prevent resistance to targeted therapies in NSCLC patients. Citation Format: SK Kayum Alam, Matteo Astone, Ping Liu, Li Wang, Abbygail M. Coyle, Erin N. Dankert, Dane K. Hoffman, Stephanie R. Hall, Wei Zhang, Rui Kuang, Anja C. Roden, Aaron S. Mansfield, Luke H. Hoeppner. Molecular mechanisms of non-small cell lung cancer growth and drug resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 873.

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