Expression differences of genes in the PI3K/AKT, WNT/b-catenin, SHH, NOTCH and MAPK signaling pathways in CD34+ hematopoietic cells obtained from chronic phase patients with chronic myeloid leukemia and from healthy controls

FOLR1-stabilized β-catenin promotes laryngeal carcinoma progression through EGFR/AKT/GSK-3β pathway

Folate receptor 1 (FOLR1) is overexpressed in numerous epithelial malignancies; however, its role in laryngeal squamous cell carcinoma (LSCC) remains unclear. In the present study, we demonstrated that FOLR1 messenger RNA and protein expression levels were higher in LSCC tissues than in the adjacent normal tissues. Additionally, FOLR1 promoted the proliferation and migration of LSCC cells, whereas small interfering RNA-mediated knockdown of β-catenin abolished these effects. Moreover, FOLR1 stabilizes β-catenin by inhibiting its ubiquitination and degradation. Furthermore, blocking the interaction between epidermal growth factor receptor (EGFR) and the EGFR/AKT/glycogen synthase (GSK)3β signaling axis both abolished FOLR1's effects on the expression and nuclear aggregation of β-catenin. In summary, our work reveals a novel mode in which FOLR1 promotes the proliferation and migration of LSCC by enhancing the stability and nuclear translocation of β-catenin through the EGFR/AKT/GSK3β axis.

Hedgehog signaling in tissue homeostasis, cancers, and targeted therapies

The past decade has seen significant advances in our understanding of Hedgehog (HH) signaling pathway in various biological events. HH signaling pathway exerts its biological effects through a complex signaling cascade involved with primary cilium. HH signaling pathway has important functions in embryonic development and tissue homeostasis. It plays a central role in the regulation of the proliferation and differentiation of adult stem cells. Importantly, it has become increasingly clear that HH signaling pathway is associated with increased cancer prevalence, malignant progression, poor prognosis and even increased mortality. Understanding the integrative nature of HH signaling pathway has opened up the potential for new therapeutic targets for cancer. A variety of drugs have been developed, including small molecule inhibitors, natural compounds, and long non-coding RNA (LncRNA), some of which are approved for clinical use. This review outlines recent discoveries of HH signaling in tissue homeostasis and cancer and discusses how these advances are paving the way for the development of new biologically based therapies for cancer. Furthermore, we address status quo and limitations of targeted therapies of HH signaling pathway. Insights from this review will help readers understand the function of HH signaling in homeostasis and cancer, as well as opportunities and challenges of therapeutic targets for cancer.

Management of Chronic Myeloid Leukemia in Children and Young Adults

Purpose of Review

Due to lack of pediatric-specific data, the management of chronic myeloid leukemia (CML) in pediatric, adolescents, and young adults is guided by adult CML evidence-based recommendations. Pediatric CML presents differently than adult CML and is often a more aggressive disease with different biological and host factors, yet there is sparse literature on how to address those differences.

Recent Findings

Over the past two decades, tyrosine kinase inhibitors (TKIs) have changed the way CML is treated. There are currently three FDA-approved TKIs (imatinib, dasatinib, and nilotinib) for pediatric patients. When choosing which TKI to begin treatment with, there are many factors that should be considered on a case-to-case basis to obtain optimal outcomes. The safety profiles for long-term TKI use in pediatrics require further study. Unlike adults, children are still actively growing during TKI use, and the effect on development can be detrimental. TKI therapy is not recommended during pregnancy with variable but significant risk of fetal abnormalities and miscarriage, warranting counseling for young female patients prior to beginning TKIs. Attempts for treatment-free remission (TFR) by planned TKI cessation in eligible adult patients in deep and sustained molecular remission are now done as a standard of practice. However, data is sparse in the pediatric population. There is currently an ongoing Children’s Oncology Group (COG) study to determine the feasibility of TFR as a treatment goal.

Summary

Further research and additional pediatric trials are needed to characterize the unique aspects of CML in children and adolescents and optimize outcomes.

Comparative Gene Expression Analysis Reveals Similarities and Differences of Chronic Myeloid Leukemia Phases

Chronic myeloid leukemia (CML) is a slowly progressing blood cancer that primarily affects elderly people. Without successful treatment, CML progressively develops from the chronic phase through the accelerated phase to the blast crisis, and ultimately to death. Nowadays, the availability of targeted tyrosine kinase inhibitor (TKI) therapies has led to long-term disease control for the vast majority of patients. Nevertheless, there are still patients that do not respond well enough to TKI therapies and available targeted therapies are also less efficient for patients in accelerated phase or blast crises. Thus, a more detailed characterization of molecular alterations that distinguish the different CML phases is still very important. We performed an in-depth bioinformatics analysis of publicly available gene expression profiles of the three CML phases. Pairwise comparisons revealed many differentially expressed genes that formed a characteristic gene expression signature, which clearly distinguished the three CML phases. Signaling pathway expression patterns were very similar between the three phases but differed strongly in the number of affected genes, which increased with the phase. Still, significant alterations of MAPK, VEGF, PI3K-Akt, adherens junction and cytokine receptor interaction signaling distinguished specific phases. Our study also suggests that one can consider the phase-wise CML development as a three rather than a two-step process. This is in accordance with the phase-specific expression behavior of 24 potential major regulators that we predicted by a network-based approach. Several of these genes are known to be involved in the accumulation of additional mutations, alterations of immune responses, deregulation of signaling pathways or may have an impact on treatment response and survival. Importantly, some of these genes have already been reported in relation to CML (e.g., AURKB, AZU1, HLA-B, HLA-DMB, PF4) and others have been found to play important roles in different leukemias (e.g., CDCA3, RPL18A, PRG3, TLX3). In addition, increased expression of BCL2 in the accelerated and blast phase indicates that venetoclax could be a potential treatment option. Moreover, a characteristic signaling pathway signature with increased expression of cytokine and ECM receptor interaction pathway genes distinguished imatinib-resistant patients from each individual CML phase. Overall, our comparative analysis contributes to an in-depth molecular characterization of similarities and differences of the CML phases and provides hints for the identification of patients that may not profit from an imatinib therapy, which could support the development of additional treatment strategies.

Targeting HSPA8 inhibits proliferation via downregulating BCR-ABL and enhances chemosensitivity in imatinib-resistant chronic myeloid leukemia cells

The resistance to tyrosine kinase inhibitors is currently a major problem for chronic myeloid leukemia (CML) treatment and HSPA8 is highly expressed and a hallmark of poor prognosis in several human cancers. However, its role in imatinib-resistant CML (IR-CML) cells remains undetermined. Here, we determined HSPA8 was overexpressed in IR-CML cells and associated with imatinib resistance. HSPA8 ablation could downregulate BCR-ABL/STAT5 and BCR-ABL/AKT signaling pathways, dramatically induce proliferation inhibition, autophagy, G0/G1 phase cell cycle arrest but not apoptosis in IR-CML cells. Significantly, HSPA8 ablation enhanced the antitumor activity of imatinib via promoting apoptosis in vitro and vivo. These findings unraveled that HSPA8 ablation inhibits proliferation via downregulating BCR-ABL and enhances chemosensitivity of imatinib in IR-CML cells, which investigate the role and molecular mechanism of HSPA8 in IR-CML cells and suggest that HSPA8 may be a potential target for IR-CML treatment.

Chronic Myelogenous Leukemia in Childhood

PURPOSE OF REVIEW

Chronic myelogenous leukemia (CML) is rare in children, requiring extrapolation from treatment of adults. In this review, we explore similarities and differences between adult and pediatric CML with a focus on therapeutic advances and emerging clinical questions.

RECENT FINDINGS

Pediatric CML is effectively treated with long-term targeted therapy using tyrosine kinase inhibitors (TKIs). Newly diagnosed pediatric patients in chronic phase can now be treated with imatinib, dasatinib, or nilotinib without allogeneic hematopoietic stem cell transplantation. While treatment-free remission is possible in adults in chronic phase with optimal response to therapy, data are currently insufficient to support stopping TKI in pediatrics outside of a clinical trial. Knowledge gaps remain regarding long-term and late effects of TKIs in pediatric CML. Targeted therapy has markedly improved outcomes for pediatric CML, while raising a number of clinical questions, including the possibility of treatment-free remission and long-term health implications of prolonged TKI exposure at a young age.

Expression of lipid transport-associated genes in lipid-deprived cancer cells

Cancer cells are known to significantly alter their lipid profiles in response to changes in extracellular lipid availability. Recent studies have shown that in response to lipid deprivation, cancer cells display significant changes in their cellular lipid homeostasis. These changes have been linked to the modulation of de novo lipid synthesis pathways that are markedly altered under lipid-deprived growth conditions. However, the effects of such environment on intracellular lipid trafficking-that could also affect cellular lipid homeostasis-have not been widely investigated. The presented work studies the effect of lipid deprivation on expression of genes for lipid transport proteins (LTPs) in cancer cell lines.

The emerging roles of OSBP-related proteins in cancer: Impacts through phosphoinositide metabolism and protein-protein interactions

Oxysterol-binding protein -related proteins (ORPs) form a large family of intracellular lipid binding/transfer proteins. A number of ORPs are implicated in inter-organelle lipid transfer over membrane contacts sites, their mode of action involving in several cases the transfer of two lipids in opposite directions, termed countercurrent lipid transfer. A unifying feature appears to be the capacity to bind phosphatidylinositol polyphosphates (PIPs). These lipids are in some cases transported by ORPs from one organelle to another to drive the transfer of another lipid against its concentration gradient, while they in other cases may act as allosteric regulators of ORPs, or an ORP may introduce a PIP to an enzyme for catalysis. Dysregulation of several ORP family members is implicated in cancers, ORP3, -4, -5 and -8 being thus far the most studied examples. The most likely mechanisms underlying their associations with malignant growth are (i) impacts on PIP-mediated signaling events resulting in altered Ca²⁺ homeostasis, bioenergetics, cell survival, proliferation, and migration, (ii) protein-protein interactions affecting the activity of signaling factors, and (iii) modification of cellular lipid transport in a way that facilitates the proliferation of malignant cells. In this review I discuss the existing functional evidence for the involvement of ORPs in cancerous growth, discuss the findings in the light of the putative mechanisms outlined above and the possibility of employing ORPs as targets of anti-cancer therapy.

Cancer Stem Cells-Origins and Biomarkers: Perspectives for Targeted Personalized Therapies

The use of biomarkers in diagnosis, therapy and prognosis has gained increasing interest over the last decades. In particular, the analysis of biomarkers in cancer patients within the pre- and post-therapeutic period is required to identify several types of cells, which carry a risk for a disease progression and subsequent post-therapeutic relapse. Cancer stem cells (CSCs) are a subpopulation of tumor cells that can drive tumor initiation and can cause relapses. At the time point of tumor initiation, CSCs originate from either differentiated cells or adult tissue resident stem cells. Due to their importance, several biomarkers that characterize CSCs have been identified and correlated to diagnosis, therapy and prognosis. However, CSCs have been shown to display a high plasticity, which changes their phenotypic and functional appearance. Such changes are induced by chemo- and radiotherapeutics as well as senescent tumor cells, which cause alterations in the tumor microenvironment. Induction of senescence causes tumor shrinkage by modulating an anti-tumorigenic environment in which tumor cells undergo growth arrest and immune cells are attracted. Besides these positive effects after therapy, senescence can also have negative effects displayed post-therapeutically. These unfavorable effects can directly promote cancer stemness by increasing CSC plasticity phenotypes, by activating stemness pathways in non-CSCs, as well as by promoting senescence escape and subsequent activation of stemness pathways. At the end, all these effects can lead to tumor relapse and metastasis. This review provides an overview of the most frequently used CSC markers and their implementation as biomarkers by focussing on deadliest solid (lung, stomach, liver, breast and colorectal cancers) and hematological (acute myeloid leukemia, chronic myeloid leukemia) cancers. Furthermore, it gives examples on how the CSC markers might be influenced by therapeutics, such as chemo- and radiotherapy, and the tumor microenvironment. It points out, that it is crucial to identify and monitor residual CSCs, senescent tumor cells, and the pro-tumorigenic senescence-associated secretory phenotype in a therapy follow-up using specific biomarkers. As a future perspective, a targeted immune-mediated strategy using chimeric antigen receptor based approaches for the removal of remaining chemotherapy-resistant cells as well as CSCs in a personalized therapeutic approach are discussed.

The chromatin remodeler Brg1 is required for formation and maintenance of hematopoietic stem cells

Hematopoietic stem and progenitor cells (HSPCs) have the ability to self-renew and differentiate into various blood cells, thus playing an important role in maintenance of lifelong hematopoiesis. Brahma-related gene 1 (BRG1), which acts as the ATP subunit of mammalian SWI-SNF-related chromatin remodeling complexes, is involved in human acute myeloid leukemia and highly expresses in short-term HSPCs. But its role and regulatory mechanism for HSPC development have not yet been well established. Here, we generated a brg1 knockout zebrafish model using TALEN technology. We found that in brg1^-/- embryo, the primitive hematopoiesis remained well, while definitive hematopoiesis formation was significantly impaired. The number of hemogenic endothelial cells was decreased, further affecting definitive hematopoiesis with reduced myeloid and lymphoid cells. During embryogenesis, the nitric oxide (NO) microenvironment in brg1^-/- embryo was seriously damaged and the reduction of HSPCs could be partially rescued by a NO donor. Chromatin immunoprecipitation (ChIP) assays showed that BRG1 could bind to the promoter of KLF2 and trigger its transcriptional activity of NO synthase. Our findings show that Brg1 promotes klf2a expression in hemogenic endothelium and highlight a novel mechanism for HSPC formation and maintenance.

Inhibition of p90RSK activation sensitizes triple-negative breast cancer cells to cisplatin by inhibiting proliferation, migration and EMT

Cisplatin (Cis-DDP) is one of the most widely used anti-cancer drugs. It is applicable to many types of cancer, including lung, bladder, and breast cancer. However, its use is now limited because of drug resistance. p90 ribosomal S6 kinase (p90RSK) is one of the downstream effectors in the extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) pathway and high expression of p90RSK is observed in human breast cancer tissues. Therefore, we investigated the role of p90RSK in the Cis-DDP resistance-related signaling pathway and epithelial-mesenchymal transition (EMT) in breast cancer cells. First, we discovered that MDA-MB-231 cells exhibited more Cis-DDP resistance than other breast cancer cells, including MCF-7 and BT549 cells. Cis-DDP increased p90RSK activation, whereas the inactivation of p90RSK using a small interfering RNA (siRNA) or dominant-negative kinase mutant plasmid overexpression significantly reduced Cis-DDP-induced cell proliferation and migration via the inhibition of matrix metallopeptidase (MMP)2 and MMP9 in MDA-MB-231 cells. In addition, p90RSK activation was involved in EMT via the upregulation of mRNA expression, including that of Snail, Twist, ZEB1, N-cadherin, and vimentin. We also investigated NF-κB, the upstream regulator of EMT markers, and discovered that Cis-DDP treatment led to NF-κB translocation in the nucleus as well as its promoter activity. Our results suggest that targeting p90RSK would be a good strategy to increase Cis-DDP sensitivity in triple-negative breast cancers.

MiR-15/16 mediate crosstalk between the MAPK and Wnt/β-catenin pathways during hepatocyte differentiation from amniotic epithelial cells

MiR-15/16 play an important role in liver development and hepatocyte differentiation, but the mechanisms by which these miRNAs regulate their targets and downstream genes to influence cell fate are poorly understood. In this study, we showed up-regulation of miR-15/16 during HGF- and FGF4-induced hepatocyte differentiation from amniotic epithelial cells (AECs). To elucidate the role of miR-15/16 and their targets in hepatocyte differentiation, we investigated the roles of miR-15/16 in both the MAPK and Wnt/β-catenin pathways, which were predicted to be involved in miR-15/16 signaling. Our results demonstrated that the transcription of miR-15/16 was enhanced by c-Fos, c-Jun, and CREB, important elements of the MAPK pathway, and miR-15/16 in turn directly targeted adenomatous polyposis coli (APC) protein, a major member of the β-catenin degradation complex. MiR-15/16 destroyed these degradation complexes to activate β-catenin, and the activated β-catenin combined with LEF/TCF7L1 to form a transcriptional complex that enhanced transcription of hepatocyte nuclear factor 4 alpha (HNF4α). HNF4α also bound the promoter region of miR-15/16 and promoted its transcription, thereby forming a regulatory circuit to promote the differentiation of AECs into hepatocytes. Endogenous miRNAs are, therefore, involved in hepatocyte differentiation from AECs and should be considered during the development of an effective hepatocyte transplant therapy for liver damage.