The Fanconi anemia pathway has a dual function in Dickkopf-1 transcriptional repression

Inhibition of WNT signaling by conjugated microRNA nano-carriers: A new therapeutic approach for treating triple-negative breast cancer a perspective review

Triple-Negative Breast Cancer is the most aggressive form and accounts the 15%-25% of all breast cancer. Receptors are absent in triple-negative breast cancer, which makes them unresponsive to the current hormonal therapies. The patients with TNBC are left with the option of cytotoxic chemotherapy. The Wnt pathways are connected to cancer, and when activated, they result in mammary hyperplasia and tumors. The tumor suppressor microRNAs can block tumor cell proliferation, invasion, and migration, lead to cancer cell death, and are also known to down-regulate the WNT signaling. Nanoparticles with microRNA have been seen to be more effective when compared with their single release. In this review, we have tried to understand how Wnt signaling plays a crucial role in TNBC, EMT, metastasis, anti-drug resistance, and regulation of Wnt by microRNA. The role of nano-carriers in delivering micro-RNA. The clinical biomarkers, including the present state-of-the-art, involve novel pathways of Wnt.

Fanconi anemia pathway as a prospective target for cancer intervention

Fanconi anemia (FA) is a recessive genetic disorder caused by biallelic mutations in at least one of 22 FA genes. Beyond its pathological presentation of bone marrow failure and congenital abnormalities, FA is associated with chromosomal abnormality and genomic instability, and thus represents a genetic vulnerability for cancer predisposition. The cancer relevance of the FA pathway is further established with the pervasive occurrence of FA gene alterations in somatic cancers and observations of FA pathway activation-associated chemotherapy resistance. In this article we describe the role of the FA pathway in canonical interstrand crosslink (ICL) repair and possible contributions of FA gene alterations to cancer development. We also discuss the perspectives and potential of targeting the FA pathway for cancer intervention.

Comparative genomics provides new insights into the remarkable adaptations of the African wild dog (Lycaon pictus)

Within the Canidae, the African wild dog (Lycaon pictus) is the most specialized with regards to cursorial adaptations (specialized for running), having only four digits on their forefeet. In addition, this species is one of the few canids considered to be an obligate meat-eater, possessing a robust dentition for taking down large prey, and displays one of the most variable coat colorations amongst mammals. Here, we used comparative genomic analysis to investigate the evolutionary history and genetic basis for adaptations associated with cursoriality, hypercanivory, and coat color variation in African wild dogs. Genome-wide scans revealed unique amino acid deletions that suggest a mode of evolutionary digit loss through expanded apoptosis in the developing first digit. African wild dog-specific signals of positive selection also uncovered a putative mechanism of molar cusp modification through changes in genes associated with the sonic hedgehog (SHH) signaling pathway, required for spatial patterning of teeth, and three genes associated with pigmentation. Divergence time analyses suggest the suite of genomic changes we identified evolved ~1.7 Mya, coinciding with the diversification of large-bodied ungulates. Our results show that comparative genomics is a powerful tool for identifying the genetic basis of evolutionary changes in Canidae.

Fanconi anemia complementation group C protection against oxidative stress‑induced β‑cell apoptosis

Diabetes mellitus (DM) and other glucose metabolism abnormalities are commonly observed in individuals with Fanconi anemia (FA). FA causes an impaired response to DNA damage due to genetic defects in a cluster of genes encoded proteins involved in DNA repair. However, the mechanism by which FA is associated with DM has not been clearly elucidated. Fanconi anemia complementation group C (FANCC) is a component of FA nuclear clusters. Evidence suggests that cytoplasmic FANCC has a role in protection against oxidative stress‑induced apoptosis. As oxidative stress‑mediated β‑cell dysfunction is one of the contributors to DM pathogenesis, the present study aimed to investigate the role of FANCC in pancreatic β‑cell response to oxidative stress. Small interfering RNA‑mediated FANCC suppression caused a loss of protection against oxidative stress‑induced apoptosis, and that overexpression of FANCC reduced this effect in the human 1.1B4 β‑cell line. These findings were confirmed by Annexin V‑FITC/PI staining, caspase 3/7 activity assay, and expression levels of anti‑apoptotic and pro‑apoptotic genes. Insulin and glucokinase mRNA expression were also decreased in FANCC‑depleted 1.1B4 cells. The present study demonstrated the role of FANCC in protection against oxidative stress‑induced β‑cell apoptosis and established another mechanism that associates FANCC deficiency with β‑cell dysfunction. The finding that FANCC overexpression reduced β‑cell apoptosis advances the potential for an alternative approach to the treatment of DM caused by FANCC defects.

Lipidomic Profiling Links the Fanconi Anemia Pathway to Glycosphingolipid Metabolism in Head and Neck Cancer Cells

Purpose: Mutations in Fanconi anemia (FA) genes are common in sporadic squamous cell carcinoma of the head and neck (HNSCC), and we have previously demonstrated that FA pathway depletion in HNSCC cell lines stimulates invasion. The goal of our studies was to use a systems approach in order to define FA pathway-dependent lipid metabolism and to extract lipid-based signatures and effectors of invasion in FA-deficient cells.Experimental Design: We subjected FA-isogenic HNSCC keratinocyte cell lines to untargeted and targeted lipidomics analyses to discover novel biomarkers and candidate therapeutic targets in FA-deficient cells. Cellular invasion assays were carried out in the presence and absence of N-butyldeoxynojirimycin (NB-DNJ), a biosynthetic inhibitor of the newly identified class of gangliosides, to investigate the requirement of ganglioside upregulation in FA-deficient HNSCC cells.Results: The most notable element of the lipid profiling results was a consistent elevation of glycosphingolipids, and particularly the accumulation of gangliosides. Conversely, repression of this same class of lipids was observed upon genetic correction of FA patient-derived HNSCC cells. Functional studies demonstrate that ganglioside upregulation is required for HNSCC cell invasion driven by FA pathway loss. The motility of nontransformed keratinocytes in response to FA loss displayed a similar dependence, thus supporting early and late roles for the FA pathway in controlling keratinocyte invasion through lipid regulation.Conclusions: Elevation of glycosphingolipids including the ganglioside GM3 in response to FA loss stimulates invasive characteristics of immortalized and transformed keratinocytes. An inhibitor of glycosphingolipid biosynthesis NB-DNJ attenuates invasive characteristics of FA-deficient HNSCC cells. Clin Cancer Res; 24(11); 2700-9. ©2018 AACR.

Genomic analysis of synchronous intracranial meningiomas with different histological grades

Although meningioma is the most common primary tumor of the central nervous system, the mechanism of progression from benign to atypical or anaplastic grade remains elusive. The present case reports the genomic evaluation of two synchronous meningiomas with different histological grades (benign and atypical) in the same patient. Under the assumption that the atypical tumor may have progressed from the benign tumor, the clonal origin of the lesions was investigated to identify genomic events responsible for the oncogenic process of evolution to higher grades in meningioma. A 59 year-old female patient was diagnosed with two synchronous meningiomas with different histological grades, benign and atypical. Whole-exome sequencing (WES) and RNA sequencing (RNA-seq) analysis of both tumors were done. WES analysis showed that each meningioma harbored distinct mutation profiles, and RNA-seq analysis revealed distinct gene expression profiles between the two tumors. The only apparent common genetic abnormality found in both tumors was the loss of heterozygosity of chromosome 22, raising the possibility that this event is the initial step in tumor formation, after which distinct subsequent mutations lead to the evolvement of two separate tumors of different grades. The result provides additional evidence on previous reports suggesting separate, independent mechanism of progression into higher grades in meningioma.

Recent advances in understanding hematopoiesis in Fanconi Anemia

Fanconi anemia is an inherited disease characterized by genomic instability, hypersensitivity to DNA cross-linking agents, bone marrow failure, short stature, skeletal abnormalities, and a high relative risk of myeloid leukemia and epithelial malignancies. The 21 Fanconi anemia genes encode proteins involved in multiple nuclear biochemical pathways that effect DNA interstrand crosslink repair. In the past, bone marrow failure was attributed solely to the failure of stem cells to repair DNA. Recently, non-canonical functions of many of the Fanconi anemia proteins have been described, including modulating responses to oxidative stress, viral infection, and inflammation as well as facilitating mitophagic responses and enhancing signals that promote stem cell function and survival. Some of these functions take place in non-nuclear sites and do not depend on the DNA damage response functions of the proteins. Dysfunctions of the canonical and non-canonical pathways that drive stem cell exhaustion and neoplastic clonal selection are reviewed, and the potential therapeutic importance of fully investigating the scope and interdependences of the canonical and non-canonical pathways is emphasized.

Hematopoietic development: a gap in our understanding of inherited bone marrow failure

Inherited bone marrow failure syndromes (IBMFS) represent a heterogeneous group of multisystem disorders that typically present with cytopenia in early childhood. Efforts to understand the underlying hematopoietic stem cell (HSC) losses have generally focused on postnatal hematopoiesis. However, reflecting the role of many of the involved genes in core cellular functions and the diverse nonhematologic abnormalities seen in patients at birth, studies have begun to explore IBMFS manifestations during fetal development. Here, I consider the current evidence for fetal deficits in the HSC pool and highlight emerging concepts regarding the origins and unique pathophysiology of hematopoietic failure in IBMFS.

The mTOR Complex Controls HIV Latency

A population of CD4 T lymphocytes harboring latent HIV genomes can persist in patients on antiretroviral therapy, posing a barrier to HIV eradication. To examine cellular complexes controlling HIV latency, we conducted a genome-wide screen with a pooled ultracomplex shRNA library and in vitro system modeling HIV latency and identified the mTOR complex as a modulator of HIV latency. Knockdown of mTOR complex subunits or pharmacological inhibition of mTOR activity suppresses reversal of latency in various HIV-1 latency models and HIV-infected patient cells. mTOR inhibitors suppress HIV transcription both through the viral transactivator Tat and via Tat-independent mechanisms. This inhibition occurs at least in part via blocking the phosphorylation of CDK9, a p-TEFb complex member that serves as a cofactor for Tat-mediated transcription. The control of HIV latency by mTOR signaling identifies a pathway that may have significant therapeutic opportunities.

Wnt signaling in triple-negative breast cancer

Wnt signaling regulates a variety of cellular processes, including cell fate, differentiation, proliferation and stem cell pluripotency. Aberrant Wnt signaling is a hallmark of many cancers. An aggressive subtype of breast cancer, known as triple-negative breast cancer (TNBC), demonstrates dysregulation in canonical and non-canonical Wnt signaling. In this review, we summarize regulators of canonical and non-canonical Wnt signaling, as well as Wnt signaling dysfunction that mediates the progression of TNBC. We review the complex molecular nature of TNBC and the emerging therapies that are currently under investigation for the treatment of this disease.

Modulating Dickkopf-1: A Strategy to Monitor or Treat Cancer?

Dickkopf-1 (DKK1) is a secreted Wnt/β-catenin pathway antagonist involved in embryogenesis. It was first described 25 years ago for its function in head induction and limb morphogenesis. Since then, this protein has been widely studied in the context of active Wnt/β-catenin signalling during cellular differentiation and development. Dysregulation of DKK1 has been associated with bone pathologies and has now emerged as a potential biomarker of cancer progression and prognosis for several types of malignancies. Reducing the amount of circulating DKK1 may reveal a simple and efficient strategy to limit or reverse cancer growth. This review will provide an overview of the role of Dickkopf-1 in cancer and explore its potential use as a biomarker and therapeutic target.

Leukemic survival factor SALL4 contributes to defective DNA damage repair

SALL4 is aberrantly expressed in human myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). We have generated a SALL4 transgenic (SALL4B Tg) mouse model with pre-leukemic MDS-like symptoms that transform to AML over time. This makes our mouse model applicable for studying human MDS/AML diseases. Characterization of the leukemic initiation population in this model leads to the discovery that Fancl (Fanconi anemia, complementation group L) is downregulated in SALL4B Tg leukemic and pre-leukemic cells. Similar to the reported Fanconi anemia (FA) mouse model, chromosomal instability with radial changes can be detected in pre-leukemic SALL4B Tg bone marrow (BM) cells after DNA damage challenge. Results from additional studies using DNA damage repair reporter assays support a role of SALL4 in inhibiting the homologous recombination pathway. Intriguingly, unlike the FA mouse model, after DNA damage challenge, SALL4B Tg BM cells can survive and generate hematopoietic colonies. We further elucidated that the mechanism by which SALL4 promotes cell survival is through Bcl2 activation. Overall, our studies demonstrate for the first time that SALL4 has a negative impact in DNA damage repair, and support the model of dual functional properties of SALL4 in leukemogenesis through inhibiting DNA damage repair and promoting cell survival.

Loss of Fancc Impairs Antibody-Secreting Cell Differentiation in Mice through Deregulating the Wnt Signaling Pathway

Fanconi anemia (FA) is characterized by a progressive bone marrow failure and an increased incidence of cancer. FA patients have high susceptibility to immune-related complications such as infection and posttransplant graft-versus-host disease. In this study, we investigated the effect of FA deficiency in B cell function using the Fancc mouse model. Fancc(-/-) B cells show a specific defect in IgG2a switch and impaired Ab-secreting cell (ASC) differentiation. Global transcriptome analysis of naive B cells by mRNA sequencing demonstrates that FA deficiency deregulates a network of genes involved in immune function. Significantly, many genes implicated in Wnt signaling were aberrantly expressed in Fancc(-/-) B cells. Consistently, Fancc(-/-) B cells accumulate high levels of β-catenin under both resting and stimulated conditions, suggesting hyperactive Wnt signaling. Using an in vivo Wnt GFP reporter assay, we verified the upregulation of Wnt signaling as a potential mechanism responsible for the impaired Fancc(-/-) B cell differentiation. Furthermore, we showed that Wnt signaling inhibits ASC differentiation possibly through repression of Blimp1 and that Fancc(-/-) B cells are hypersensitive to Wnt activation during ASC differentiation. Our findings identify Wnt signaling as a physiological regulator of ASC differentiation and establish a role for the Wnt pathway in normal B cell function and FA immune deficiency.

The Fanconi Anemia C Protein Binds to and Regulates Stathmin-1 Phosphorylation

The Fanconi anemia (FA) proteins are involved in a signaling network that assures the safeguard of chromosomes. To understand the function of FA proteins in cellular division events, we investigated the interaction between Stathmin-1 (STMN1) and the FA group C (FANCC) protein. STMN1 is a ubiquitous cytosolic protein that regulates microtubule dynamics. STMN1 activities are regulated through phosphorylation-dephosphorylation mechanisms that control assembly of the mitotic spindle, and dysregulation of STMN1 phosphorylation is associated with mitotic aberrancies leading to chromosome instability and cancer progression. Using different biochemical approaches, we showed that FANCC interacts and co-localizes with STMN1 at centrosomes during mitosis. We also showed that FANCC is required for STMN1 phosphorylation, as mutations in FANCC reduced serine 16- and 38-phosphorylated forms of STMN1. Phosphorylation of STMN1 at serine 16 is likely an event dependent on a functional FA pathway, as it is reduced in FANCA- and FANCD2-mutant cells. Furthermore, FA-mutant cells exhibited mitotic spindle anomalies such as supernumerary centrosomes and shorter mitotic spindles. These results suggest that FA proteins participate in the regulation of cellular division via the microtubule-associated protein STMN1.

Fanconi anemia signaling and Mus81 cooperate to safeguard development and crosslink repair

Individuals with Fanconi anemia (FA) are susceptible to bone marrow failure, congenital abnormalities, cancer predisposition and exhibit defective DNA crosslink repair. The relationship of this repair defect to disease traits remains unclear, given that crosslink sensitivity is recapitulated in FA mouse models without most of the other disease-related features. Mice deficient in Mus81 are also defective in crosslink repair, yet MUS81 mutations have not been linked to FA. Using mice deficient in both Mus81 and the FA pathway protein FancC, we show both proteins cooperate in parallel pathways, as concomitant loss of FancC and Mus81 triggered cell-type-specific proliferation arrest, apoptosis and DNA damage accumulation in utero. Mice deficient in both FancC and Mus81 that survived to birth exhibited growth defects and an increased incidence of congenital abnormalities. This cooperativity of FancC and Mus81 in developmental outcome was also mirrored in response to crosslink damage and chromosomal integrity. Thus, our findings reveal that both pathways safeguard against DNA damage from exceeding a critical threshold that triggers proliferation arrest and apoptosis, leading to compromised in utero development.