A single extra copy of Dscr1 improves survival of mice developing spontaneous lung tumors through suppression of tumor angiogenesis

S6K1 deficiency in tumor stroma impairs lung metastasis of melanoma in mice

Accumulating data suggest that ribosomal protein S6 kinase 1 (S6K1), an effector in the mammalian target of rapamycin (mTOR) pathway, plays pleiotropic roles in tumor progression. However, to date, while the tumorigenic function of S6K1 in tumor cells has been well elucidated, its role in the tumor stroma remains poorly understood. We recently showed that S6K1 mediates vascular endothelial growth factor A (VEGF-A) production in macrophages, thereby supporting tumor angiogenesis and growth. As macrophage-derived VEGF-A is crucial for both tumor cell intravasation and extravasation across the vascular endothelium, our previous findings suggest that stromal S6K1 signaling is required for tumor metastatic spread. Therefore, we aimed to determine the impact of host S6K1 depletion on tumor metastasis using a murine model of pulmonary metastasis (S6k1-/- mice implanted with B16F10 melanoma). The ablation of S6K1 in the host microenvironment significantly reduced the metastasized B16F10 melanoma cells on the lung surface in both spontaneous and intravenous lung metastasis mouse models without affecting the incidence of metastasis to distant lymph nodes. In addition, stromal S6K1 loss decreased the number of tumor cells circulating in the peripheral blood of mice bearing B16F10 xenografts without affecting the vascular leakage induced by VEGF-A in vivo. These observations demonstrate that S6K1 signaling in host cells other than endothelial cells is required to modulate the host microenvironment to facilitate the metastatic spread of tumors via blood circulation, thus revealing its novel role in the tumor stroma during tumor progression.

Insights from the protein interaction Universe of the multifunctional "Goldilocks" kinase DYRK1A

Human Dual specificity tyrosine (Y)-Regulated Kinase 1A (DYRK1A) is encoded by a dosage-dependent gene located in the Down syndrome critical region of human chromosome 21. The known substrates of DYRK1A include proteins involved in transcription, cell cycle control, DNA repair and other processes. However, the function and regulation of this kinase is not fully understood, and the current knowledge does not fully explain the dosage-dependent function of this kinase. Several recent proteomic studies identified DYRK1A interacting proteins in several human cell lines. Interestingly, several of known protein substrates of DYRK1A were undetectable in these studies, likely due to a transient nature of the kinase-substrate interaction. It is possible that the stronger-binding DYRK1A interacting proteins, many of which are poorly characterized, are involved in regulatory functions by recruiting DYRK1A to the specific subcellular compartments or distinct signaling pathways. Better understanding of these DYRK1A-interacting proteins could help to decode the cellular processes regulated by this important protein kinase during embryonic development and in the adult organism. Here, we review the current knowledge of the biochemical and functional characterization of the DYRK1A protein-protein interaction network and discuss its involvement in human disease.

Inverse Comorbidity between Down Syndrome and Solid Tumors: Insights from In Silico Analyses of Down Syndrome Critical Region Genes

An inverse comorbidity has been observed between Down syndrome (DS) and solid tumors such as breast and lung cancers, and it is posited that the overexpression of genes within the Down Syndrome Critical Region (DSCR) of human chromosome 21 may account for this phenomenon. By analyzing publicly available DS mouse model transcriptomics data, we aimed to identify DSCR genes that may protect against human breast and lung cancers. Gene expression analyses with GEPIA2 and UALCAN showed that DSCR genes ETS2 and RCAN1 are significantly downregulated in breast and lung cancers, and their expression levels are higher in triple-negative compared to luminal and HER2-positive breast cancers. KM Plotter showed that low levels of ETS2 and RCAN1 are associated with poor survival outcomes in breast and lung cancers. Correlation analyses using OncoDB revealed that both genes are positively correlated in breast and lung cancers, suggesting that they are co-expressed and perhaps have complementary functions. Functional enrichment analyses using LinkedOmics also demonstrated that ETS2 and RCAN1 expression correlates with T-cell receptor signaling, regulation of immunological synapses, TGF-β signaling, EGFR signaling, IFN-γ signaling, TNF signaling, angiogenesis, and the p53 pathway. Altogether, ETS2 and RCAN1 may be essential for the development of breast and lung cancers. Experimental validation of their biological functions may further unravel their roles in DS and breast and lung cancers.

RCAN1-mediated calcineurin inhibition as a target for cancer therapy

Cancer is the leading cause of mortality worldwide. Regulator of calcineurin 1 (RCAN1), as a patent endogenous inhibitor of calcineurin, plays crucial roles in the pathogenesis of cancers. Except for hypopharyngeal and laryngopharynx cancer, high expression of RCAN1 inhibits tumor progression. Molecular antitumor functions of RCAN1 are largely dependent on calcineurin. In this review, we highlight current research on RCAN1 characteristics, and the interaction between RCAN1 and calcineurin. Moreover, the dysregulation of RCAN1 in various cancers is reviewed, and the potential of targeting RCAN1 as a new therapeutic approach is discussed.

The Paradox of Myeloid Leukemia Associated with Down Syndrome

Children with Down syndrome constitute a distinct genetic population who has a greater risk of developing acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) compared to their non-Down syndrome counterparts. The risk for developing solid tumors is also distinct from the non-Down syndrome population. In the case of myeloid leukemias, the process of leukemogenesis in Trisomy 21 begins in early fetal life where genetic drivers including GATA1 mutations lead to the development of the preleukemic condition, transient abnormal myelopoiesis (TAM). Various other mutations in genes encoding cohesin, epigenetic regulators and RAS pathway can result in subsequent progression to Myeloid Leukemia associated with Down Syndrome (ML-DS). The striking paradoxical feature in the Down syndrome population is that even though there is a higher predisposition to developing AML, they are also very sensitive to chemotherapy agents, particularly cytarabine, thus accounting for the very high cure rates for ML-DS compared to AML in children without Down syndrome. Current clinical trials for ML-DS attempt to balance effective curative therapies while trying to reduce treatment-associated toxicities including infections by de-intensifying chemotherapy doses, if possible. The small proportion of patients with relapsed ML-DS have an extremely poor prognosis and require the development of new therapies.

Aneuploidy as a promoter and suppressor of malignant growth

Aneuploidy has been recognized as a hallmark of tumorigenesis for more than 100 years, but the connection between chromosomal errors and malignant growth has remained obscure. New evidence emerging from both basic and clinical research has illuminated a complicated relationship: despite its frequency in human tumours, aneuploidy is not a universal driver of cancer development and instead can exert substantial tumour-suppressive effects. The specific consequences of aneuploidy are highly context dependent and are influenced by a cell's genetic and environmental milieu. In this Review, we discuss the diverse facets of cancer biology that are shaped by aneuploidy, including metastasis, drug resistance and immune recognition, and we highlight aneuploidy's distinct roles as both a tumour promoter and an anticancer vulnerability.

Loss of S6K1 But Not S6K2 in the Tumor Microenvironment Suppresses Tumor Growth by Attenuating Tumor Angiogenesis

Two isoforms of the 70-kDa ribosomal protein S6 kinase, S6K1 and S6K2, have been identified and are considered key downstream effectors of the mTOR signaling pathway, which is involved in tumor growth and progression. However, their biological roles in the tumor microenvironment are poorly understood. In this study, utilizing tumor xenograft models in S6k1^−/− and S6k2^−/− mice, we show that loss of S6K1 but not S6K2 in the tumor stroma suppresses tumor growth, accompanied by attenuated tumor angiogenesis. We found that while S6K1 depletion had no effect on the proangiogenic phenotype of endothelial cells, the growth and angiogenesis of tumor xenografts were significantly reduced in wild-type mice upon reconstitution with S6K1-deficient bone marrow cells. Furthermore, upon S6K1 loss, induction of both mRNA and protein levels of Hif-1α and those of the downstream target, Vegf, was compromised in bone marrow–derived macrophages stimulated with lactate. These findings indicate that S6K1 but not S6K2 contributes to establishing a microenvironment that favors tumor growth through mediating angiogenesis, and suggest that attenuated tumor angiogenesis upon loss of S6K1 in the tumor stroma is, at least in part, attributable to impaired upregulation of Vegf in tumor-associated macrophages.

Multiple Molecular Targets Associated with Genomic Instability in Lung Cancer

Lung cancer (LC) is the first cause of cancer-related deaths worldwide. Elucidating the pathogenesis of LC will give information on key elements of tumor initiation and development while helping to design novel targeted therapies. LC is an heterogeneous disease that has the second highest mutation rate surpassed only by melanoma, since 90% of LC occurs in tobacco smokers. However, only a small percent of smokers develops LC, indicating an inherent genomic instability. Additionally, LC in never smokers suggests other molecular mechanisms not causally linked to tobacco carcinogens. This review presents a current outlook of the connection between LC and genomic instability at the molecular and clinical level summarizing its implications for diagnosis, therapy, and prognosis. The genomic landscape of LC shows widespread alterations such as DNA methylation, point mutations, copy number variation, chromosomal translocations, and aneuploidy. Genome maintenance mechanisms including cell cycle control, DNA repair, and mitotic checkpoints open a window to translational research for finding novel diagnostic biomarkers and targeted therapies in LC.

Arsenic Trioxide Inhibits the Metastasis of Small Cell Lung Cancer by Blocking Calcineurin-Nuclear Factor of Activated T Cells (NFAT) Signaling

BACKGROUND The inhibitory effect of arsenic trioxide (As₂O₃) on lung cancer has been reported in some preclinical studies. However, its effect on small cell lung cancer (SCLC) has been poorly explored. Calcineurin and its substrate, nuclear factor of activated T cells (NFAT), mediate the downstream signaling of VEGF, and is critical in the process endothelium activation and tumor metastasis. In this study, we aimed to evaluate whether As₂O₃ had inhibitory effects on endothelial cells activation and the metastasis of SCLC, and to explore the possible mechanisms. MATERIAL AND METHODS In vitro, human umbilical vein endothelial cells (HUVECs) were used. Cell Counting Kit-8 assay and cell migration assay were performed to determine the effect of As₂O₃ on HUVECs proliferation and migration. The level of calcineurin, NFAT, downstream factors for Down syndrome candidate region 1 (DSCR1), and the endogenous inhibitor of calcineurin, were evaluated by quantitative PCR and western blotting. In vivo, SCLC metastasis models were established by injecting NCI-H446 cells into tail veins of nude mice. Tumor-bearing mice were treated with As₂O₃ or calcineurin inhibitor for 10 days, after which tumor metastasis in target organs was evaluated. RESULTS As₂O₃ significantly inhibited the proliferation and migration of endothelial cells. Also, As₂O₃ inhibited the expression levels of calcineurin, NFAT, and the downstream target genes CXCR7 and RND1, while it upregulated the level of DSCR1. Both As₂O₃ and calcineurin inhibitor exhibited notable inhibitory effect on the metastasis of SCLC, without obvious side effects. CONCLUSIONS These findings suggested that As₂O₃ had remarkable inhibitory effects on the endothelial cell activation and SCLC metastasis, and the mechanism might be related to the blocking of calcineurin-NFAT signaling by upregulating DSCR1.

The regulator of calcineurin 1 (RCAN1) inhibits nuclear factor kappaB signaling pathway and suppresses human malignant glioma cells growth

Nuclear factor-kappaB (NF-κB) has a vital role in cell survival and inhibition of NF-κB had proven to be an efficient therapeutic pathway for various cancers though little is known about the underlying mechanism. Previously we identified regulator of calcineurin 1 (RCAN1) as an endogenous inhibitor of NF-κB signaling pathway in lymphoma. In the present study, we have solid data to show that RCAN1 can inhibit the nuclear translocation of NF-κB protein then affect the activity of NF-κB signaling pathway in glioma cells. Overexpression of RCAN1 markedly reduced glioma cells viability. We further found that the suppressing glioma cell growth was closely related to the pro-apoptosis effect, not by inhibiting proliferation by the arrest of cell cycle. Our study implicated a novel therapeutic approach for glioma by RCAN1 through inhibition of NF-κB signaling.

Epidermal growth factor receptor-mutant lung cancer in Down syndrome: a case presentation and review of the literature

BACKGROUND

Solid tumors have a markedly decreased incidence in individuals with Down syndrome (DS), including lung cancers.

METHODS

The clinical presentation of epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer (NSCLC) in DS was reported and literature on the subject reviewed.

RESULTS

In individuals with DS, the risk of lung cancer appears markedly lower. EGFR mutation and EGFR tyrosine kinase inhibitors (EGFR-TKIs) resistance also exist in DS with lung cancer.

CONCLUSIONS

Clinicians should consider EGFR mutation and EGFR-TKIs resistance in lung cancer patients with DS.

The RCAN1 inhibits NF-κB and suppresses lymphoma growth in mice

Nuclear factor-κB (NF-κB) has a vital role in cell survival. Inhibition of NF-κB has been proven to be an efficient therapeutic pathway for various cancers. Activation of NF-κB is mainly through serine residues' phosphorylation of inhibitor of κBα (IκBα) by IKK complex. Phosphorylation at tyrosine 42 is an alternative pathway in regulation of IκBα and NF-κB signaling, though little is known about the underlying mechanism. Here we identified regulator of calcineurin 1 (RCAN1) as a novel endogenous inhibitor of NF-κB signaling pathway. RCAN1 can interact with IκBα and affect the phosphorylation of IκBα at tyrosine 42. Overexpression of RCAN1 by adenovirus reduced cell viability in lymphoma Raji cells and restrained the growth of lymphoma transplants in mice. We further found that N terminus 1–103aa of RCAN1 is sufficient to inhibit NF-κB and reduce cell viability of lymphoma cells. Our study implicated a novel therapeutic approach for lymphoma by RCAN1 through inhibition of NF-κB signaling.

Aneuploidy and chromosomal instability in cancer: a jackpot to chaos

Genomic instability (GIN) is a hallmark of cancer cells that facilitates the acquisition of mutations conferring aggressive or drug-resistant phenotypes during cancer evolution. Chromosomal instability (CIN) is a form of GIN that involves frequent cytogenetic changes leading to changes in chromosome copy number (aneuploidy). While both CIN and aneuploidy are common characteristics of cancer cells, their roles in tumor initiation and progression are unclear. On the one hand, CIN and aneuploidy are known to provide genetic variation to allow cells to adapt in changing environments such as nutrient fluctuations and hypoxia. Patients with constitutive aneuploidies are more susceptible to certain types of cancers, suggesting that changes in chromosome copy number could positively contribute to cancer evolution. On the other hand, chromosomal imbalances have been observed to have detrimental effects on cellular fitness and might trigger cell cycle arrest or apoptosis. Furthermore, mouse models for CIN have led to conflicting results. Taken together these findings suggest that the relationship between CIN, aneuploidy and cancer is more complex than what was previously anticipated. Here we review what is known about this complex ménage à trois, discuss recent evidence suggesting that aneuploidy, CIN and GIN together promote a vicious cycle of genome chaos. Lastly, we propose a working hypothesis to reconcile the conflicting observations regarding the role of aneuploidy and CIN in tumorigenesis.

A genomic approach to study down syndrome and cancer inverse comorbidity: untangling the chromosome 21

Down syndrome (DS), one of the most common birth defects and the most widespread genetic cause of intellectual disabilities, is caused by extra genetic material on chromosome 21 (HSA21). The increased genomic dosage of trisomy 21 is thought to be responsible for the distinct DS phenotypes, including an increased risk of developing some types of childhood leukemia and germ cell tumors. Patients with DS, however, have a strikingly lower incidence of many other solid tumors. We hypothesized that the third copy of genes located in HSA21 may have an important role on the protective effect that DS patients show against most types of solid tumors. Focusing on Copy Number Variation (CNV) array data, we have generated frequencies of deleted regions in HSA21 in four different tumor types from which DS patients have been reported to be protected. We describe three different regions of deletion pointing to a set of candidate genes that could explain the inverse comorbidity phenomenon between DS and solid tumors. In particular we found RCAN1 gene in Wilms tumors and a miRNA cluster containing miR-99A, miR-125B2 and miR-LET7C in lung, breast, and melanoma tumors as the main candidates for explaining the inverse comorbidity observed between solid tumors and DS.

CDO, an Hh-coreceptor, mediates lung cancer cell proliferation and tumorigenicity through Hedgehog signaling

Hedgehog (Hh) signaling plays essential roles in various developmental processes, and its aberrant regulation results in genetic disorders or malignancies in various tissues. Hyperactivation of Hh signaling is associated with lung cancer development, and there have been extensive efforts to investigate how to control Hh signaling pathway and regulate cancer cell proliferation. In this study we investigated a role of CDO, an Hh co-receptor, in non-small cell lung cancer (NSCLC). Inhibition of Hh signaling by SANT-1 or siCDO in lung cancer cells reduced proliferation and tumorigenicity, along with the decrease in the expression of the Hh components. Histological analysis with NSCLC mouse tissue demonstrated that CDO was expressed in advanced grade of the cancer, and precisely co-localized with GLI1. These data suggest that CDO is required for proliferation and survival of lung cancer cells via Hh signaling.

Cyclosporin A promotes tumor angiogenesis in a calcineurin-independent manner by increasing mitochondrial reactive oxygen species

The widely used immunosuppressant cyclosporin A, a potent calcineurin inhibitor, significantly increases the incidence of cancer in organ transplant patients. Calcineurin signaling is an important mediator of VEGF signaling in endothelial cells. Negative regulation of calcineurin by its endogenous inhibitor, Down Syndrome Candidate Region-1 (DSCR1), suppresses tumor growth and angiogenesis, in contrast to the effect observed after long-term cyclosporin A treatment. Despite the significance of calcineurin signaling in endothelial cells, the consequences of cyclosporin A on tumor angiogenesis have not been investigated. Using an in vivo model of skin carcinogenesis, prolonged treatment with cyclosporin A promoted tumor growth and angiogenesis. The addition of cyclosporin A to endothelial cells in vitro increased proliferation and migration in a calcineurin-independent manner and is associated with increased mitochondrial reactive oxygen species (ROS). Co-treatment with antioxidants significantly abrogated cyclosporin A-induced endothelial cell activation. Furthermore, mice treated with antioxidants were protected against cyclosporin A-mediated tumor progression. Taken together, these findings suggest that cyclosporin A affects endothelial cells in a calcineurin-independent manner to potentiate tumor growth by promoting tumor angiogenesis through increasing mitochondrial ROS production. This work identifies a previously undescribed mechanism underlying a significantly adverse off-target effect of cyclosporin A and suggests that co-treatment with antioxidants would inhibit the tumor-promoting effects of cyclosporin A.

IMPLICATIONS

Targeting the proangiogenic effects of cyclosporin A may be useful in the management of transplant-associated cancers.