Mutant IDH inhibitors induce lineage differentiation in IDH-mutant oligodendroglioma

A subset of patients with IDH-mutant glioma respond to inhibitors of mutant IDH (IDHi), yet the molecular underpinnings of such responses are not understood. Here, we profiled by single-cell or single-nucleus RNA-sequencing three IDH-mutant oligodendrogliomas from patients who derived clinical benefit from IDHi. Importantly, the tissues were sampled on-drug, four weeks from treatment initiation. We further integrate our findings with analysis of single-cell and bulk transcriptomes from independent cohorts and experimental models. We find that IDHi treatment induces a robust differentiation toward the astrocytic lineage, accompanied by a depletion of stem-like cells and a reduction of cell proliferation. Furthermore, mutations in NOTCH1 are associated with decreased astrocytic differentiation and may limit the response to IDHi. Our study highlights the differentiating potential of IDHi on the cellular hierarchies that drive oligodendrogliomas and suggests a genetic modifier that may improve patient stratification.

EGCG Disrupts the LIN28B/Let-7 Interaction and Reduces Neuroblastoma Aggressiveness

Neuroblastoma (NB) is the most commonly diagnosed extracranial solid tumor in children, accounting for 15% of all childhood cancer deaths. Although the 5-year survival rate of patients with a high-risk disease has increased in recent decades, NB remains a challenge in pediatric oncology, and the identification of novel potential therapeutic targets and agents is an urgent clinical need. The RNA-binding protein LIN28B has been identified as an oncogene in NB and is associated with a poor prognosis. Given that LIN28B acts by negatively regulating the biogenesis of the tumor suppressor let-7 miRNAs, we reasoned that selective interference with the LIN28B/let-7 miRNA interaction would increase let-7 miRNA levels, ultimately leading to reduced NB aggressiveness. Here, we selected (-)-epigallocatechin 3-gallate (EGCG) out of 4959 molecules screened as the molecule with the best inhibitory activity on LIN28B/let-7 miRNA interaction and showed that treatment with PLC/PLGA-PEG nanoparticles containing EGCG (EGCG-NPs) led to an increase in mature let-7 miRNAs and a consequent inhibition of NB cell growth. In addition, EGCG-NP pretreatment reduced the tumorigenic potential of NB cells in vivo. These experiments suggest that the LIN28B/let-7 miRNA axis is a good therapeutic target in NB and that EGCG, which can interfere with this interaction, deserves further preclinical evaluation.

Prostate cancer research: tools, cell types, and molecular targets

Multiple cancer cell types are found in prostate tumors. They are either luminal-like adenocarcinoma or less luminal-like and more stem-like non-adenocarcinoma and small cell carcinoma. These types are lineage related through differentiation. Loss of cancer differentiation from luminal-like to stem-like is mediated by the activation of stem cell transcription factors (scTF) such as LIN28A, NANOG, POU5F1 and SOX2. scTF expression leads to down-regulation of β2-microglobulin (B2M). Thus, cancer cells can change from the scT F ˜ B 2 M hi phenotype of differentiated to that of scT F ˙ B 2 M lo of dedifferentiated in the disease course. In development, epithelial cell differentiation is induced by stromal signaling and cell contact. One of the stromal factors specific to prostate encodes proenkephalin (PENK). PENK can down-regulate scTF and up-regulate B2M in stem-like small cell carcinoma LuCaP 145.1 cells indicative of exit from the stem state and differentiation. In fact, prostate cancer cells can be made to undergo dedifferentiation or reprogramming by scTF transfection and then to differentiate by PENK transfection. Therapies need to be designed for treating the different cancer cell types. Extracellular anterior gradient 2 (eAGR2) is an adenocarcinoma antigen associated with cancer differentiation that can be targeted by antibodies to lyse tumor cells with immune system components. eAGR2 is specific to cancer as normal cells express only the intracellular form (iAGR2). For AGR2-negative stem-like cancer cells, factors like PENK that can target scTF could be effective in differentiation therapy.

Inhibition of Enhancer of Zeste Homolog 2 Induces Blast Differentiation, Impairs Engraftment and Prolongs Survival in Murine Models of Acute Myeloid Leukemia

BACKGROUND

Acute myeloid leukemia (AML) is the malignant proliferation of immature myeloid cells characterized by a block in differentiation. As such, novel therapeutic strategies to promote the differentiation of immature myeloid cells have been successful in AML, although these agents are targeted to a specific mutation that is only present in a subset of AML patients. In the current study, we show that targeting the epigenetic modifier enhancer of zeste homolog 2 (EZH2) can induce the differentiation of immature blast cells into a more mature myeloid phenotype and promote survival in AML murine models.

METHODS

The EZH2 inhibitor EPZ011989 (EPZ) was studied in AML cell lines, primary in AML cells and normal CD34+ stem cells. A pharmacodynamic assessment of H3K27me3; studies of differentiation, cell growth, and colony formation; and in vivo therapeutic studies including the influence on primary AML cell engraftment were also conducted.

RESULTS

EPZ inhibited H3K27me3 in AML cell lines and primary AML samples in vitro. EZH2 inhibition reduced colony formation in multiple AML cell lines and primary AML samples, while exhibiting no effect on colony formation in normal CD34+ stem cells. In AML cells, EPZ promoted phenotypic evidence of differentiation. Finally, the pretreatment of primary AML cells with EPZ significantly delayed engraftment and prolonged the overall survival when engrafted into immunodeficient mice.

CONCLUSIONS

Despite evidence that EZH2 silencing in MDS/MPN can promote AML pathogenesis, our data demonstrate that the therapeutic inhibition of EZH2 in established AML has the potential to improve survival.

Identification of CDKN3 as a Key Gene that Regulates Neuroblastoma Cell Differentiation

We conducted a high-content screening (HCS) in neuroblastoma BE(2)-C cells to identify cell cycle regulators that control cell differentiation using a library of siRNAs against cell cycle-regulatory genes. We discovered that knocking down expression of cyclin dependent kinase inhibitor 3 (CDKN3) showed the most potent effect in inducing neurite outgrowth, the morphological cell differentiation marker of neuroblastoma cells. We then demonstrated that CDKN3 knockdown increased expression of neuroblastoma molecular differentiation markers, neuron specific enolase (NSE), βIII-tubulin and growth associated protein 43 (GAP43). We further showed that CDKN3 knockdown reduced expression of cell proliferation markers Ki67 and proliferating cell nuclear antigen (PCNA), and reduced colony formation of neuroblastoma cells. More importantly, we observed a correlation of high tumor CDKN3 mRNA levels with poor patient survival in the investigation of public neuroblastoma patient datasets. In exploring the mechanisms that regulate CDKN3 expression, we found that multiple strong differentiation-inducing molecules, including miR-506-3p and retinoic acid, down-regulated CDKN3 expression. In addition, we found that N-Myc promoted CDKN3 expression at the transcriptional level by directly binding to the CDKN3 promoter. Furthermore, we found that CDKN3 and two additional differentiation-regulating cell cycle proteins identified in our HCS, CDC6 and CDK4, form an interactive network to promote expression of each other. In summary, we for the first time discovered the function of CDKN3 in regulating neuroblastoma cell differentiation and characterized the transcriptional regulation of CDKN3 expression by N-Myc in neuroblastoma cells. Our findings support that CDKN3 plays a role in modulating neuroblastoma cell differentiation and that overexpression of CDKN3 may contribute to neuroblastoma progression.

The transcription factor HIF2α partakes in the differentiation block of acute myeloid leukemia

One of the defining features of acute myeloid leukemia (AML) is an arrest of myeloid differentiation whose molecular determinants are still poorly defined. Pharmacological removal of the differentiation block contributes to the cure of acute promyelocytic leukemia (APL) in the absence of cytotoxic chemotherapy, but this approach has not yet been translated to non-APL AMLs. Here, by investigating the function of hypoxia-inducible transcription factors HIF1α and HIF2α, we found that both genes exert oncogenic functions in AML and that HIF2α is a novel regulator of the AML differentiation block. Mechanistically, we found that HIF2α promotes the expression of transcriptional repressors that have been implicated in suppressing AML myeloid differentiation programs. Importantly, we positioned HIF2α under direct transcriptional control by the prodifferentiation agent all-trans retinoic acid (ATRA) and demonstrated that HIF2α blockade cooperates with ATRA to trigger AML cell differentiation. In conclusion, we propose that HIF2α inhibition may open new therapeutic avenues for AML treatment by licensing blasts maturation and leukemia debulking.

Amplified Ferroptosis and Apoptosis Facilitated by Differentiation Therapy Efficiently Suppress the Progression of Osteosarcoma

Osteosarcoma (OS) is the most frequent osseous neoplasm among young people aged 10-20. Currently, the leading treatment for osteosarcoma is a combination of surgery and chemotherapy. However, the mortality remains high due to chemoresistance, metastasis, and recurrence, attributing to the existence of cancer stem cells (CSCs) as reported. To target CSCs, differentiation therapy attracts increasing attention, inducing CSCs to bulk tumor cells with elevated reactive oxygen species (ROS) levels and less chemoresistance. Moreover, increasing studies have implied that ferroptosis is a promising approach to eliminating cancer cells through eliciting oxidative damage and subsequent apoptosis, effectively bypassing chemoresistance. Here, a cancer-cell-membrane-decorated biocompatible formulation (GA-Fe@CMRALi liposome) is constructed to combat OS efficiently by combining distinct differentiation and ferroptosis therapies through magnified ROS-triggered ferroptosis and apoptosis with homologous target capability to tumor sites. The combinational approach exhibited favorable therapeutic efficacy against OS in vitro and in vivo. Impressively, the potential mechanisms are revealed by mRNA sequencing. This study provides a tactical design and typical paradigm of the synergized differentiation and ferroptosis therapies to combat heterogeneous OS.

Colorectal Cancer Is Borrowing Blueprints from Intestinal Ontogenesis

Colorectal tumors are heterogenous cellular systems harboring small populations of self-renewing and highly tumorigenic cancer stem cells (CSCs). Understanding the mechanisms fundamental to the emergence of CSCs and colorectal tumor initiation is crucial for developing effective therapeutic strategies. Two recent studies have highlighted the importance of developmental gene expression programs as potential therapeutic targets to suppress pro-oncogenic stem cell populations in the colonic epithelium. Specifically, a subset of aberrant stem cells was identified in preneoplastic intestinal lesions sharing significant transcriptional similarities with fetal gut development. In such aberrant stem cells, Sox9 was shown as a cornerstone for altered cell plasticity, the maintenance of premalignant stemness, and subsequent colorectal tumor initiation. Independently, chemical genomics was used to identify FDA-approved drugs capable of suppressing neoplastic self-renewal based on the ontogenetic root of a target tumor and transcriptional programs embedded in pluripotency. Here, we discuss the joint conclusions from these two approaches, underscoring the importance of developmental networks in CSCs as a novel paradigm for identifying therapeutics targeting colorectal cancer stemness.

Cancer Stem-Like Cells-Oriented Surface Self-Assembly to Conquer Radioresistance

Cancer stem-like cells (CSCs), capable of indefinite self-renewal and differentiation, are considered to be the root cause of tumor radiotherapy (RT) resistance. However, the CSCs-targeted therapy still remains to be a great challenge because they are commonly located in the deep tumor making drugs hard to approach, and their hypoxic and acidic niche can further aggravate radioresistance. Herein, based on the finding that hypoxic CSCs highly express carbonic anhydrase IX (CAIX) on the cell membrane, a CAIX-targeted induced in situ self-assembly system on the surface of CSC is reported to overcome hypoxic CSC-mediated radioresistance. Via the sequential processes of "monomer release-target accumulation-surface self-assembly", the constructed peptide-based drug delivery system (CA-Pt) exhibits the advantages of deep penetration, amplified CAIX inhibition, and enhanced cellular uptake, which greatly relieves the hypoxic and acidic microenvironment to promote the hypoxic CSC differentiation and combines with platinum to boost the RT-inducing DNA damage. In both lung cancer tumor mouse and zebrafish embryo models, CA-Pt treatment can effectively assist RT in suppressing tumor growth and preventing tumor invasion and metastasis. This study uses a surface-induced self-assembly strategy to differentiate hypoxic CSCs, which may provide a universal treatment strategy for overcoming tumor radioresistance.

Multi-Target Neural Differentiation (MTND) Therapeutic Cocktail to Suppress Brain Tumor

Brain tumors have been proved challenging to treat. Here we established a Multi-Target Neural Differentiation (MTND) therapeutic cocktail to achieve effective and safe treatment of brain malignancies by targeting the important hallmarks in brain cancers: poor cell differentiation and compromised cell cycle. In-vitro and in-vivo experiments confirmed the significant therapeutic effect of our MTND therapy. Significantly improved therapeutic effects over current first-line chemo-drugs have been identified in clinical cells, with great inhibition of the growth and migration of tumor cells. Further in-vivo experiments confirmed that sustained MTND treatment showed a 73% reduction of the tumor area. MTND also induced strong expression of phenotypes associated with cell cycle exit/arrest and rapid neural reprograming from clinical glioma cells to glutamatergic and GABAergic expressing cells, which are two key neuronal types involved in many human brain functions, including learning and memory. Collectively, MTND induced multi-targeted genotypic expression changes to achieve direct neural conversion of glioma cells and controlled the cell cycle/tumorigenesis development, helping control tumor cells' malignant proliferation and making it possible to treat brain malignant tumors effectively and safely. These encouraging results open avenues to developing new therapies for brain malignancies beyond cytotoxic agents, providing more effective medication recommendations with reduced toxicity.

The Promise of Retinoids in the Treatment of Cancer: Neither Burnt Out Nor Fading Away

Since the introduction of all-trans retinoic acid (ATRA), acute promyelocytic leukemia (APL) has become a highly curable malignancy, especially in combination with arsenic trioxide (ATO). ATRA's success has deepened our understanding of the role of the RARα pathway in normal hematopoiesis and leukemogenesis, and it has influenced a generation of cancer drug development. Retinoids have also demonstrated some efficacy in a handful of other disease entities, including as a maintenance therapy for neuroblastoma and in the treatment of cutaneous T-cell lymphomas; nevertheless, the promise of retinoids as a differentiating therapy in acute myeloid leukemia (AML) more broadly, and as a cancer preventative, have largely gone unfulfilled. Recent research into the mechanisms of ATRA resistance and the biomarkers of RARα pathway dysregulation in AML have reinvigorated efforts to successfully deploy retinoid therapy in a broader subset of myeloid malignancies. Recent studies have demonstrated that the bone marrow environment is highly protected from exogenous ATRA via local homeostasis controlled by stromal cells expressing CYP26, a key enzyme responsible for ATRA inactivation. Synthetic CYP26-resistant retinoids such as tamibarotene bypass this stromal protection and have shown superior anti-leukemic effects. Furthermore, recent super-enhancer (SE) analysis has identified a novel AML subgroup characterized by high expression of RARα through strong SE levels in the gene locus and increased sensitivity to tamibarotene. Combined with a hypomethylating agent, synthetic retinoids have shown synergistic anti-leukemic effects in non-APL AML preclinical models and are now being studied in phase II and III clinical trials.

A Brief Review on Chemoresistance; Targeting Cancer Stem Cells as an Alternative Approach

The acquisition of resistance to traditional chemotherapy and the chemoresistant metastatic relapse of minimal residual disease both play a key role in the treatment failure and poor prognosis of cancer. Understanding how cancer cells overcome chemotherapy-induced cell death is critical to improve patient survival rate. Here, we briefly describe the technical approach directed at obtaining chemoresistant cell lines and we will focus on the main defense mechanisms against common chemotherapy triggers by tumor cells. Such as, the alteration of drug influx/efflux, the enhancement of drug metabolic neutralization, the improvement of DNA-repair mechanisms, the inhibition of apoptosis-related cell death, and the role of p53 and reactive oxygen species (ROS) levels in chemoresistance. Furthermore, we will focus on cancer stem cells (CSCs), the cell population that subsists after chemotherapy, increasing drug resistance by different processes such as epithelial-mesenchymal transition (EMT), an enhanced DNA repair machinery, and the capacity to avoid apoptosis mediated by BCL2 family proteins, such as BCL-XL, and the flexibility of their metabolism. Finally, we will review the latest approaches aimed at decreasing CSCs. Nevertheless, the development of long-term therapies to manage and control CSCs populations within the tumors is still necessary.

The Rationality of Implementation of Dimethyl Sulfoxide as Differentiation-inducing Agent in Cancer Therapy

One of the major hallmarks of many cancer cells is dedifferentiated cells (immature cells) with little or no resemblance to normal cells. Besides the poor differentiation, malignant cells also have important features such as aggressiveness and resistance to different therapeutics. Differentiation potentiators hold great promise for cancer treatment. Dimethyl sulfoxide (DMSO) is a well-characterized pharmaceutical solvent. It is used as a component of numerous cancer therapeutic approaches, including cancer treatment and several approved cancer immune therapeutics such as Car-T cell therapy and the FDA-approved drug Mekinist (trametinib DMSO) for melanoma treatment. It is also biologically recognized as a pharmaceutical solvent and cryoprotectant. In the current literature, there are no mentions of DMSO's possible ability to potentiate therapeutic activity as a component of these cancer treatments. This review aimed to summarize scientific evidence and substantiate the concept that DMSO can contribute positively to the overall efficacy of cancer treatment as an adjuvant that is safe, inexpensive, and an effective differentiation-inducing therapeutic agent.

Inhibition of O-GlcNAcase Inhibits Hematopoietic and Leukemic Stem Cell Self-Renewal and Drives Dendritic Cell Differentiation via STAT3/5 Signaling

Myeloid differentiation blockage at immature and self-renewing stages is a common hallmark across all subtypes of acute myeloid leukemia (AML), despite their genetic heterogeneity. Metabolic state is an important regulator of hematopoietic stem cell (HSC) self-renewal and lineage-specific differentiation as well as several aggressive cancers. However, how O-GlcNAcylation, a nutrient-sensitive posttranslational modification of proteins, contributes to both normal myelopoiesis and AML pathogenesis remains largely unknown. Using small molecule inhibitors and the CRISPR/Cas9 system, we reveal for the first time that inhibition of either OGA or OGT, which subsequently caused an increase or decrease in cellular O-GlcNAcylation, inhibits the self-renewal and maintenance of CD34+ hematopoietic stem/progenitor cells (HSPCs) and leukemic stem/progenitor cells and drives normal and malignant myeloid differentiation. We further unveiled the distinct roles of OGA and OGT inhibition in lineage-specific differentiation. While OGT inhibition induces macrophage differentiation, OGA inhibition promotes the differentiation of both CD34+ HSPCs and AML cells into dendritic cells (DCs), in agreement with an upregulation of a multitude of genes involved in DC development and function and their ability to induce T-cell proliferation, via STAT3/5 signaling. Our novel findings provide significant basic knowledge that could be important in understanding AML pathogenesis and overcoming differentiation blockage-agnostic to the genetic background of AML. Additionally, the parallel findings in normal HSPCs may lay the groundwork for future cellular therapy as a means to improve the ex vivo differentiation of normal DCs and macrophages.

Acquired semi-squamatization during chemotherapy suggests differentiation as a therapeutic strategy for bladder cancer

Cisplatin-based chemotherapy remains the primary treatment for unresectable and metastatic muscle-invasive bladder cancers (MIBCs). However, tumors frequently develop chemoresistance. Here, we established a primary and orthotopic MIBC mouse model with gene-edited organoids to recapitulate the full course of chemotherapy in patients. We found that partial squamous differentiation, called semi-squamatization, is associated with acquired chemoresistance in both mice and human MIBCs. Multi-omics analyses showed that cathepsin H (CTSH) is correlated with chemoresistance and semi-squamatization. Cathepsin inhibition by E64 treatment induces full squamous differentiation and pyroptosis, and thus specifically restrains chemoresistant MIBCs. Mechanistically, E64 treatment activates the tumor necrosis factor pathway, which is required for the terminal differentiation and pyroptosis of chemoresistant MIBC cells. Our study revealed that semi-squamatization is a type of lineage plasticity associated with chemoresistance, suggesting that differentiation via targeting of CTSH is a potential therapeutic strategy for the treatment of chemoresistant MIBCs.

The Histone Deacetylase Inhibitor I1 Induces Differentiation of Acute Leukemia Cells With MLL Gene Rearrangements via Epigenetic Modification

Acute leukemia (AL) is characterized by excessive proliferation and impaired differentiation of leukemic cells. AL includes acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). Previous studies have demonstrated that about 10% of AML and 22% of ALL are mixed lineage leukemia gene rearrangements (MLLr) leukemia. The prognosis of MLLr leukemia is poor and new therapeutics are urgently needed. Differentiation therapy with all-trans-retinoic acid (ATRA) has prolonged the 5-years disease-free survival rate in acute promyelocytic leukemia (APL), a subtype of AML. However, the differentiation therapy has not been effective in other acute leukemia. Here, we aim to explore the cell differentiation effect of the potent HDACs inhibitor, I1, and the possible mechanism on the MLLr-AML and MLLr-ALL cells (MOLM-13, THP-1, MV4-11 and SEM). It is shown that I1 can significantly inhibit the proliferation and the colony-forming ability of MOLM-13, THP-1, MV4-11 and SEM cells by promoting cell differentiation coupled with cell cycle block at G0/G1 phase. We show that the anti-proliferative effect of I1 attributed to cell differentiation is most likely associated with the HDAC inhibition activity, as assessed by the acetylation of histone H3 and H4, which may dictates the activation of hematopoietic cell lineage pathway in both MOLM-13 and THP-1 cell lines. Moreover, the activity of HDAC inhibition of I1 is stronger than that of SAHA in MOLM-13 and THP-1 cells. Our findings suggest that I1, as a chromatin-remodeling agent, could be a potent epigenetic drug to overcome differentiation block in MLLr-AL patients and would be promising for the treatment of AL.

The Histone Deacetylase Inhibitor I13 Induces Differentiation of M2, M3 and M5 Subtypes of Acute Myeloid Leukemia Cells and Leukemic Stem-Like Cells

Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy characterized by reduced differentiation of myeloid cells and uncontrolled cell proliferation. AML is prone to drug resistance and has a high recurrence rate during treatment with cytarabine-based chemotherapy. Our study aims to explore the cell differentiation effect of a potent histone deacetylase inhibitor (HDACi), I13, and its possible mechanism on AML cell lines (Kasumi-1, KG-1, MOLM-13 and NB4). It has been shown that I13 can significantly inhibit proliferation and colony formation of these AML cells by inducing cell differentiation coupled with cell-cycle exit at G0/G1. Mechanically, I13 presented the property of HDAC inhibition, as assessed by the acetylation of histone H3, which led to the differentiation of Kasumi-1 cells. In addition, the HDAC inhibition of I13 likely dictated the activation of the antigen processing and presentation pathway, which maybe has the potential to promote immune cells to recognize leukemic cells and respond directly against leukemic cells. These results indicated that I13 could induce differentiation of M3 and M5 subtypes of AML cells, M2 subtype AML cells with t(8;21) translocation and leukemic stem-like cells. Therefore, I13 could be an alternative compound which is able to overcome differentiation blocks in AML.

Small Molecule-Induced Differentiation As a Potential Therapy for Liver Cancer

Despite the efficacy demonstrated by immunotherapy recently, liver cancer still remains one of the deadliest cancers, mainly due to heterogeneity of this disease. Continuous exploration of new therapeutics is therefore necessary. Chemical-induced cell differentiation can serve as a promising approach, with its ability to consistently remodel gene expression profile and alter cell fate. Inspired by advances in stem cell and reprogramming field, here it is reported that a small molecule cocktail (SMC) consisted of: SB431542 (TGFβ inhibitor), CHIR99021 (GSK3β inhibitor), BIX01294 (H3K9 methyltransferase/G9a inhibitor), and all-trans retinoic acid (ATRA), can induce differentiation of liver cancer cells including cell lines, primary cancer cells, cancer stem cells, and drug resistant cells. Treated cells lose malignant characteristics and regain hepatocyte phenotype instead. When applied in vivo, SMC induces wide range of tissue necrosis or fibrosis within the tumors, while remaining tissues begin to express hepatic nuclear factor 4α (HNF4α), the hepatic nuclear marker. SMC also leads to tumor abrogation in orthotopic xenograft models and life span extension of animals. The powerful differentiation induction of SMC is exerted through modulation of Akt/mTOR/HIF1α signaling and metabolic reprogramming, as well as suppressing Snail and enhancing HNF4α expression. Together, these results highlight that chemical-induced differentiation has the potential to effectively treat liver cancer disregard of heterogeneity.

Inhibiting ALK2/ALK3 Signaling to Differentiate and Chemo-Sensitize Medulloblastoma

Simple Summary

Many cancers re-emerge after treatment, despite the sensitivity of the bulk of tumor cells to treatments. This observation has led to the ‘cancer stem cell’ (CSCs) hypothesis, stating that a subpopulation of cancer cells survive therapy and lead to tumor relapse. However, the lack of universal markers to target CSCs is the main constraint to fully eradicate the CSC pool. Differentiation therapy (DT) might in principle suppress tumorigenesis through conversion of undifferentiated cancer cells of high malignancy into differentiated cells of low tumorigenic potential. Here, we provide evidence that CSCs of medulloblastoma can be forced to resume their differentiation potential by inhibiting the BMP4–ALK2/3 axis, providing a new entry point for medulloblastoma treatment.

Abstract

Background: Medulloblastoma (MB) is a malignant pediatric brain tumor, and it represents the leading cause of death related to cancer in childhood. New perspectives for therapeutic development have emerged with the identification of cancer stem cells (CSCs) displaying tumor initiating capability and chemoresistance. However, the mechanisms responsible for CSCs maintenance are poorly understood. The lack of a universal marker signature represents the main constraints to identify and isolate CSCs within the tumor. Methods: To identify signaling pathways promoting CSC maintenance in MB, we combined tumorsphere assays with targeted neurogenesis PCR pathway arrays. Results: We showed a consistent induction of signaling pathways regulating pluripotency of CSCs in all the screened MB cells. BMP4 signaling was consistently enriched in all tumorsphere(s) independently of their specific stem-cell marker profile. The octamer-binding transcription factor 4 (OCT4), an important regulator of embryonic pluripotency, enhanced CSC maintenance in MBs by inducing the BMP4 signaling pathway. Consistently, inhibition of BMP4 signaling with LDN-193189 reduced stem-cell traits and promoted cell differentiation. Conclusions: Our work suggests that interfering with the BMP4 signaling pathway impaired the maintenance of the CSC pool by promoting cell differentiation. Hence, differentiation therapy might represent an innovative therapeutic to improve the current standard of care in MB patients.

Hepatocellular Carcinoma Differentiation: Research Progress in Mechanism and Treatment

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver. Although progress has been made in diagnosis and treatment, morbidity and mortality continue to rise. Chronic liver disease and liver cirrhosis are still the most important risk factors for liver cancer. Although there are many treatments, it can only be cured by orthotopic liver transplantation (OLT) or surgical resection. And the worse the degree of differentiation, the worse the prognosis of patients with liver cancer. Then it can be considered that restoring a better state of differentiation may improve the prognosis. The differentiation treatment of liver cancer is to reverse the dedifferentiation process of hepatocytes to liver cancer cells by means of drugs, improve the differentiation state of the tumor, and restore the normal liver characteristics, so as to improve the prognosis. Understanding the mechanism of dedifferentiation of liver cancer can provide ideas for drug design. Liver enrichment of transcription factors, imbalance of signal pathway and changes of tumor microenvironment can promote the occurrence and development of liver cancer, and restoring its normal level can inhibit the malignant behavior of tumor. At present, some drugs have been proved to be effective, but more clinical data are needed to support the effectiveness and reliability of drugs. The differentiation treatment of liver cancer is expected to become an important part of the treatment of liver cancer in the future.

NeuroD1 Dictates Tumor Cell Differentiation in Medulloblastoma

Tumor cells are characterized by unlimited proliferation and perturbed differentiation. Using single-cell RNA sequencing, we demonstrate that tumor cells in medulloblastoma (MB) retain their capacity to differentiate in a similar way as their normal originating cells, cerebellar granule neuron precursors. Once they differentiate, MB cells permanently lose their proliferative capacity and tumorigenic potential. Differentiated MB cells highly express NeuroD1, a helix-loop-helix transcription factor, and forced expression of NeuroD1 promotes the differentiation of MB cells. The expression of NeuroD1 in bulk MB cells is repressed by trimethylation of histone 3 lysine-27 (H3K27me3). Inhibition of the histone lysine methyltransferase EZH2 prevents H3K27 trimethylation, resulting in increased NeuroD1 expression and enhanced differentiation in MB cells, which consequently reduces tumor growth. These studies reveal the mechanisms underlying MB cell differentiation and provide rationales to treat MB (potentially other malignancies) by stimulating tumor cell differentiation.

Cheng et al. demonstrate that medulloblastoma cells retain the capacity to undergo differentiation. The differentiation of tumor cells is regulated by NeuroD1 expression, which is repressed by H3K27me3 in tumor cells. EZH2 inhibitors suppress medulloblastoma growth by stimulating tumor cell differentiation.

Targeting Cancer Stem Cells with Differentiation Agents as an Alternative to Genotoxic Chemotherapy for the Treatment of Malignant Testicular Germ Cell Tumors

Testicular germ cell tumors (TGCTs) are exceptionally sensitive to genotoxic chemotherapy, resulting in a high cure rate for the young men presenting with these malignancies. However, this treatment is associated with significant toxicity, and a subset of malignant TGCTs demonstrate chemoresistance. Mixed nonseminomas often contain pluripotent embryonal carcinoma (EC) cells, the cancer stem cells (CSCs) of these tumors. We hypothesized that differentiation therapy, a treatment strategy which aims to induce differentiation of tumor-propagating CSCs to slow tumor growth, could effectively treat mixed nonseminomas without significant toxicity. The FDA-approved antipsychotic thioridazine and the agricultural antibiotic salinomycin are two drugs previously found to selectively target CSCs, and here we report that these agents differentiate EC cells in vitro and greatly reduce their tumorigenic potential in vivo. Using a novel transformed induced pluripotent stem cell allograft model and a human xenograft model, we show that thioridazine extends the survival of tumor-bearing mice and can reduce the number of pluripotent EC cells within tumors. These results suggest that thioridazine could be repurposed as an alternative TGCT treatment that avoids the toxicity of conventional chemotherapeutics.

p53 Protein Isoform Profiles in AML: Correlation with Distinct Differentiation Stages and Response to Epigenetic Differentiation Therapy

p53 protein isoform expression has been found to correlate with prognosis and chemotherapy response in acute myeloid leukemia (AML). We aimed to investigate how p53 protein isoforms are modulated during epigenetic differentiation therapy in AML, and if p53 isoform expression could be a potential biomarker for predicting a response to this treatment. p53 full-length (FL), p53β and p53γ protein isoforms were analyzed by 1D and 2D gel immunoblots in AML cell lines, primary AML cells from untreated patients and AML cells from patients before and after treatment with valproic acid (VPA), all-trans retinoic acid (ATRA) and theophylline. Furthermore, global gene expression profiling analysis was performed on samples from the clinical protocol. Correlation analyses were performed between p53 protein isoform expression and in vitro VPA sensitivity and FAB (French–American–British) class in primary AML cells. The results show downregulation of p53β/γ and upregulation of p53FL in AML cell lines treated with VPA, and in some of the patients treated with differentiation therapy. p53FL positively correlated with in vitro VPA sensitivity and the FAB class of AML, while p53β/γ isoforms negatively correlated with the same. Our results indicate that p53 protein isoforms are modulated by and may predict sensitivity to differentiation therapy in AML.

High-content, targeted RNA-seq screening in organoids for drug discovery in colorectal cancer

Organoids allow the recapitulation of intestinal homeostasis and cancerogenesis in vitro; however, RNA sequencing (RNA-seq)-based methods for drug screens are missing. We develop targeted organoid sequencing (TORNADO-seq), a high-throughput, high-content drug discovery platform that uses targeted RNA-seq to monitor the expression of large gene signatures for the detailed evaluation of cellular phenotypes in organoids. TORNADO-seq is a fast, highly reproducible time- and cost-effective ($5 per sample) method that can probe cell mixtures and their differentiation state in the intestinal system. We apply this method to isolate drugs that enrich for differentiated cell phenotypes and show that these drugs are highly efficacious against cancer compared to wild-type organoids. Furthermore, TORNADO-seq facilitates in-depth insight into the mode of action of these drugs. Our technology can easily be adapted to many other systems and will allow for more systematic, large-scale, and quantitative approaches to study the biology of complex cellular systems.

Jiyuan Oridonin A Overcomes Differentiation Blockade in Acute Myeloid Leukemia Cells With MLL Rearrangements via Multiple Signaling Pathways

Differentiation therapy with all-trans-retinoic acid (ATRA) in acute promyelocytic leukemia (APL), a subtype of acute myeloid leukemia (AML), has been extremely successful in inducing clinical remission in APL patients. However, the differentiation therapy of ATRA-based treatment has not been effective in other subtypes of AML. In this study, we evaluated a small molecule of ent-kaurene diterpenoid, Jiyuan oridonin A (JOA), on the differentiation blockade in AML cells with the mixed lineage leukemia (MLL) gene rearrangements (MLLr) in MV4-11, MOLM-13 and THP-1 cells. We found that JOA could significantly inhibit the proliferation of MOLM-13, MV4-11 and THP-1 cells. Moreover, JOA promoted cell differentiation coupled with cell-cycle exit at G0/G1 and inhibited the colony- forming capacity of these cells. We showed that the anti-proliferative effect of JOA attributed to cell differentiation is most likely through the martens tretinoin response up pathway in the MOLM-13 cell line, and the hematopoietic cell lineage pathway by the inhibition of c-KIT expression and cell adhesion pathway in the THP-1 cell line. Our findings suggest that JOA could be a novel therapeutic agent against human MLLr acute myeloid leukemia.

OGP46 Induces Differentiation of Acute Myeloid Leukemia Cells via Different Optimal Signaling Pathways

Acute myelogenous leukemia (AML) is characterized by blockage of cell differentiation leading to the accumulation of immature cells, which is the most prevalent form of acute leukemia in adults. It is well known that all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) are the preferred drugs for acute promyelocytic leukemia (APL). However, they can lead to irreversible resistance which may be responsible for clinical failure after complete remission (CR). Moreover, the differentiation therapy of ATRA-based treatment has not been effective against AML with t(8;21) translocation. Here we aimed to identify the differentiation effect of OGP46 on AML cell lines (HL-60, NB4, and Kasumi-1) and explore its possible mechanisms. We found that OGP46 has significant inhibitory activity against these cells by triggering cell differentiation with cell-cycle exit at G1/G0 and inhibited the colony-formation capacity of the AML cells. It was shown that OGP46 induced the differentiation of NB4 cells via the transcriptional misregulation in cancer signaling pathway by PML-RARα depletion, while it was attributed to the hematopoietic cell lineage and phagosome pathway in Kasumi-1 cells, which are all critical pathways in cell differentiation. These results highlight that OGP46 is an active agent not only in the APL cell line NB4 but also in AML-M2 cell lines, especially Kasumi-1 with t(8;21) translocation. Therefore, OGP46 may be a potential compound for surmounting the differentiation blockage in AML.

Ribociclib enhances infigratinib-induced cancer cell differentiation and delays resistance in FGFR-driven hepatocellular carcinoma

BACKGROUND & AIMS

Infigratinib is a pan-FGFR (fibroblast growth factor receptor) inhibitor that has shown encouraging activity in FGFR-dependent hepatocellular carcinoma (HCC) models. However, long-term treatment results in the emergence of resistant colonies. We sought to understand the mechanisms behind infigratinib-induced tumour cell differentiation and resistance and to explore the potential of adding the CDK4/6 inhibitor ribociclib to prolong cell differentiation.

METHODS

Nine high and three low FGFR1-3-expressing HCC patient-derived xenograft (PDX) tumours were subcutaneously implanted into SCID mice and subsequently treated with either infigratinib alone or in combination with ribociclib. Tumour tissues were then subjected to immunohistochemistry to assess cell differentiation, as indicated by the cytoplasmic-to-nuclear ratio and markers such as CYP3A4, HNF4α and albumin. Western blot analyses were performed to investigate the signalling pathways involved.

RESULTS

Infigratinib induced cell differentiation in FGFR1-3-dependent HCC PDX models, as indicated by an increase in the cytoplasmic/nuclear ratio and an increase in CYP3A4, HNF4α and albumin. Resistant colonies emerged in long-term treatment, characterised by a reversal of differentiated cell morphology, a reduction in the cytoplasmic-to-nuclear ratio and a loss of differentiation markers. Western blot analyses identified an increase in the CDK4/Cdc2/Rb pathway. The addition of ribociclib effectively blocked this pathway and reversed resistance to infigratinib, resulting in prolonged cell differentiation and growth inhibition.

CONCLUSIONS

Our findings demonstrate that the combined inhibition of FGFR/CDK4/6 pathways is highly effective in providing long-lasting tumour growth inhibition and cell differentiation and reducing drug resistance. Therefore, further clinical investigations in patients with FGFR1-3-dependant HCC are warranted.

Evolving Chemotherapy Free Regimens for Acute Promyelocytic Leukemia

With the treatment advances over the last three decades, acute promyelocytic leukemia (APL) has evolved from being the most malignant form of acute leukemia to a leukemia with excellent long term survival rates. In the present review, we have summarized data leading to the development of the currently used treatment regimens for APL, which incorporate either none or minimal chemotherapeutic drugs. We have discussed the historical aspects of APL treatment along with the challenges associated with chemotherapy-based approaches and our experience with the use of single agent arsenic trioxide (ATO) which was one of the first successful, non-chemotherapy approaches used for APL. Subsequently, we have reviewed the data from major clinical trials in low-intermediate risk APL and high risk APL which guide the current clinical practice in APL management. With accumulating data on oral ATO, we postulate that the treatment for low-intermediate risk APL will be a completely oral ATO + ATRA regimen in the future. While for high-risk APL, we believe that minimal anthracycline use with ATO + ATRA might become the standard of care soon. A number of promising non-chemotherapy drugs with pre-clinical data would merit clinical testing in the high risk and relapsed setting, with potential to translate to a complete oral chemotherapy free combination regimen in combination with ATO and ATRA.

Non-genetic heterogeneity, altered cell fate and differentiation therapy

Altered capacity for self‐renewal and differentiation is a hallmark of cancer, and many tumors are composed of cells with a developmentally immature phenotype. Among the malignancies where processes that govern cell fate decisions have been studied most extensively is acute myeloid leukemia (AML), a disease characterized by the presence of large numbers of “blasts” that resemble myeloid progenitors. Classically, the defining properties of AML cells were said to be aberrant self‐renewal and a block of differentiation, and the term “differentiation therapy” was coined to describe drugs that promote the maturation of leukemic blasts. Notionally however, the simplistic view that such agents “unblock” differentiation is at odds with the cancer stem cell (CSC) hypothesis that posits that tumors are hierarchically organized and that CSCs, which underpin cancer growth, retain the capacity to progress to a developmentally more mature state. Herein, we will review recent developments that are providing unprecedented insights into non‐genetic heterogeneity both at steady state and in response to treatment, and propose a new conceptual framework for therapies that aim to alter cell fate decisions in cancer.

Arsenic trioxide induces differentiation of cancer stem cells in hepatocellular carcinoma through inhibition of LIF/JAK1/STAT3 and NF-kB signaling pathways synergistically

OBJECTIVE

Differentiation-inducing therapy for tumors is a strategy that aims to induce the differentiation and maturation of cancer stem cells (CSCs). The differentiation-inducing capacity of arsenic trioxide (ATO) in hepatocellular carcinoma (HCC) and the underlying mechanism were previously unknown.

METHODS

In the present study, we explored the ATO-induced differentiation of CSCs in HCC by detecting the expression of CSC-related markers and tumorigenicity variation in vivo and in vitro. We developed a combined chemotherapeutic approach to HCC by characterizing the effects of combinatorial treatment with 5-fluorouracil (5-FU)/cisplatin and ATO in vitro and in patient-derived xenograft models. Changes in gene expression patterns were investigated by gene microarray analysis.

RESULTS

ATO effectively induced differentiation of CSCs by downregulation of CSC-related genes and suppression of tumorigenicity capability. Combinatorial treatment with ATO and 5-FU/cisplatin significantly enhanced therapeutic effects in HCC cells compared with the treatment with 5-FU/cisplatin alone. Synergistic inhibition of the LIF/JAK1/STAT3 and NF-kB signaling pathways by ATO and 5-FU/cisplatin is a potential molecular mechanism underlying the differentiation effect.

CONCLUSIONS

ATO induced the differentiation of HCC CSCs and potentiated the cytotoxic effects of 5-FU/cisplatin through synergistic inhibition of the LIF/JAK1/STAT3 and NF-kB signaling pathways. These results offer new insights for the clinical treatment of HCC.

Influence of HLDF Differentiation Factor on Nonspecific Invasive Breast Carcinoma in vitro

The study was carried out on samples of invasive breast carcinoma of no special type from 36 patients aged 48.0 to 62.8 years. The effect of HLDF on nonspecific invasive breast carcinoma was a decrease in the relative content of low-differentiated cells and an increase in the relative content of highly differentiated cells. HLDF did not have a cytotoxic effect leading to the death of low-differentiated cells but promoted promotes the acquisition of a higher degree of differentiation by them. A more pronounced effect of HLDF was observed in more aggressive metastasizing forms of neoplasia, which allows us to consider this differentiation factor as a candidate for use in the differentiation therapy of malignant neoplasms.

Differentiation of Cancer Stem Cells through Nanoparticle Surface Engineering

Cancer stem cells (CSCs) are a crucial therapeutic target because of their role in resistance to chemo- and radiation therapy, metastasis, and tumor recurrence. Differentiation therapy presents a potential strategy for "defanging" CSCs. To date, only a limited number of small-molecule and nanomaterial-based differentiating agents have been identified. We report here the integrated use of nanoparticle engineering and hypothesis-free sensing to identify nanoparticles capable of efficient differentiation of CSCs into non-CSC phenotypes. Using this strategy, we identified a nanoparticle that induces CSC differentiation by increasing intracellular reactive oxygen species levels. Importantly, this unreported phenotype is more susceptible to drug treatment than either CSCs or non-CSCs, demonstrating a potentially powerful strategy for anticancer therapeutics.

Differentiation of Tumorigenic C6 Glioma Cells Induced by Enhanced IL-6 Signaling

Background and objectives: Cancer stem cells (CSCs) are obstacles to cancer therapy due to their therapeutic resistance, ability to initiate neoplasia, and roles in tumor relapse and metastasis. Efforts have been made to cure CSCs, such as the use of differentiation therapy, which induces cancer stem-like cells to undergo differentiation and decrease their tumorigenicity. Interleukin 6 (IL-6) upregulates the expression of glial fibrillary acidic protein (GFAP) in C6 glioma cells, indicating that it is able to induce the differentiation of these cells. The C6 glioma cell line forms a high percentage of cancer stem-like cells, leading us to speculate whether IL-6 signaling could modulate the differentiation of tumorigenic C6 glioma cells. However, we observed that IL-6 alone could not efficiently induce the differentiation of these cells. Therefore, different IL-6 signaling elicitors, including IL-6 alone, a combination of IL-6 and soluble IL-6 receptor (IL-6/sIL-6R), and tumor necrosis factor-α (TNF-α) plus IL-6/sIL-6R (TNF-α/IL-6/sIL-6R), were evaluated for their potential use in differentiation therapy. Materials and Methods: The potential of IL-6 signaling elicitors in differentiation therapy were examined by assessing changes in biomarker levels, the rate of cell proliferation, and tumorigenicity, respectively. Results: Enhanced IL-6 signaling could effectively induce C6 glioma cell differentiation, as determined by observed variations in the expression of differentiation, cell cycle, and stem cell biomarkers. Additionally, the total cell population and the tumorigenicity of glioma cells were all considerably reduced after TNF-α/IL-6/sIL-6R treatment. Conclusions: Our findings provide evidence that enhanced IL-6 signaling can efficiently promote tumorigenic C6 glioma cells to undergo differentiation.

A Phase 1 Study of IRX195183, a RARα-Selective CYP26 Resistant Retinoid, in Patients With Relapsed or Refractory AML

Subsets of non-acute promyelocytic leukemia (APL) acute myelogenous leukemia (AML) exhibit aberrant retinoid signaling and demonstrate sensitivity to retinoids in vitro. We present the results of a phase 1 dose-escalation study that evaluated the safety, pharmacodynamics, and efficacy of IRX195183, a novel retinoic acid receptor α agonist, in patients with relapsed or refractory myelodysplastic syndrome (MDS) or AML. In this single center, single arm study, eleven patients with relapsed or refractory MDS/AML were enrolled and treated. Oral IRX195183 was administered at two dose levels: 50 mg daily or 75 mg daily for a total of two 28-day cycles. Patients with stable disease or better were allowed to continue on the drug for four additional 28-day cycles. Common adverse events included hypertriglyceridemia, fatigue, dyspnea, and edema. Three patients at the first dose level developed asymptomatic Grade 3 hypertriglyceridemia. The maximally tolerated dose was not reached. Four of the eleven patients had (36%) stable disease or better. One had a morphological complete remission with incomplete hematologic recovery while on the study drug. Two patients had evidence of in vivo leukemic blast maturation, as reflected by increased CD38 expression. In a pharmacodynamics study, plasma samples from four patients treated at the lowest dose level demonstrated the capacity to differentiate leukemic cells from the NB4 cell line in vitro. These results suggest that IRX195183 is safe, achieves biologically meaningful plasma concentrations and may be efficacious in a subset of patients with MDS/AML. Clinical Trial Registration: clinicaltrials.gov, identifier NCT02749708.

Suppression of MKL1 promotes adipocytic differentiation and reduces the proliferation of myxoid liposarcoma cells

Myxoid liposarcoma (MLS) is thought to occur due to defective adipocytic differentiation in mesenchymal stem cells. A promising strategy for MLS treatment is the prevention of sarcomagenesis by promoting the terminal differentiation of MLS cells into adipocytes. Previous studies have reported that the suppression of megakaryoblastic leukemia 1 (MKL1) expression induces adipocytic differentiation in preadipocyte cell lines. The present study aimed to investigate the effects of MKL1 suppression on MLS cells. In the present study, MKL1 knockdown was demonstrated to promote the adipocytic differentiation of an MLS-derived cell line, designated 1955/91, under adipogenic conditions. This suggests that therapeutic targeting of the MKL1-associated molecular pathway has potential as a promising method of MLS treatment. However, the induction of adipogenesis by MKL knockdown was incomplete, and Oil Red O staining indicated that intracellular lipid droplets were only sporadically generated. Conversely, MKL1 knockdown reduced the growth of the MLS cells. As adipocytic differentiation in vitro requires cellular confluence, the decreased growth rate of the MLS cells following MKL1 knockdown could be attributed to the incomplete induction of adipogenesis. Translocated in liposarcoma-CCAAT/enhancer-binding protein homologous protein (TLS-CHOP) is an MLS-specific oncoprotein that is thought to play key roles in sarcomagenesis and the suppression of adipocytic differentiation. However, the results of western blotting analyses suggest that TLS-CHOP has limited effects on MKL1 expression in MLS cells and that MKL1 knockdown hardly affects TLS-CHOP expression. Thus, it is postulated that the inhibitory effect of TLS-CHOP on adipogenesis is not associated with MKL1 expression. However, MKL1 and the molecular pathway involving MKL1 appear to be attractive targets for the differentiation therapy of MLS.

Interconversion between Tumorigenic and Differentiated States in Acute Myeloid Leukemia

Tumors are composed of phenotypically heterogeneous cancer cells that often resemble various differentiation states of their lineage of origin. Within this hierarchy, it is thought that an immature subpopulation of tumor-propagating cancer stem cells (CSCs) differentiates into non-tumorigenic progeny, providing a rationale for therapeutic strategies that specifically eradicate CSCs or induce their differentiation. The clinical success of these approaches depends on CSC differentiation being unidirectional rather than reversible, yet this question remains unresolved even in prototypically hierarchical malignancies, such as acute myeloid leukemia (AML). Here, we show in murine and human models of AML that, upon perturbation of endogenous expression of the lineage-determining transcription factor PU.1 or withdrawal of established differentiation therapies, some mature leukemia cells can de-differentiate and reacquire clonogenic and leukemogenic properties. Our results reveal plasticity of CSC maturation in AML, highlighting the need to therapeutically eradicate cancer cells across a range of differentiation states.

Dedifferentiation of hepatocellular carcinoma: molecular mechanisms and therapeutic implications

Hepatocellular carcinoma (HCC) is a common cancer with high morbidity and mortality. Poorer differentiation status indicates worse prognosis of HCC patients. Regain of better differentiation status may improve the prognosis. Differentiation therapy for HCC is based on the fact that agents may reverse the dedifferentiation process from hepatocytes to HCC cells and thus improve tumor differentiation status. Reversal of progenitor-like property and restoration of hepatic characteristics are main objectives of HCC differentiation therapy. Comprehending the mechanisms of HCC dedifferentiation provides ideas for drug design. Diverse dysregulated molecules and signalings cooperatively cause HCC dedifferentiation. Dysregulation of liver enriched transcription factors, especially hepatocyte nuclear factor 4α, was a critical determinant of HCC dedifferentiation. Aberrant pivotal signaling molecules such as transforming factor-β, β-catenin and Yes-associated protein caused disordered signalings, which promoted HCC dedifferentiation. Loss of epithelial morphology during epithelial-mesenchymal transition (EMT) concurred with HCC dedifferentiation. Some EMT-related molecules exerted double-sided role in concurrently inducing EMT and HCC dedifferentiation. Besides, microRNAs (e.g. miR-122 and miR-148a) as well as some impressive proteins (i.e. KLF4, gankyrin and CHD1L) functioned in manipulating HCC differentiation status. Restoring normal expression levels of these molecules could induce HCC differentiation and inhibited malignant tumor behaviors. Based on the knowledge above, some agents have been found effective in lab, but need more data to support their reliability. Additionally, peretinoin as a potential drug is in progress of several phase III clinical trials. It's promising that differentiation therapy for HCC may be a part of options in future HCC treatment.

Nobiletin Promotes Megakaryocytic Differentiation through the MAPK/ERK-Dependent EGR1 Expression and Exerts Anti-Leukemic Effects in Human Chronic Myeloid Leukemia (CML) K562 Cells

Differentiation therapy is an alternative strategy used to induce the differentiation of blast cells toward mature cells and to inhibit tumor cell proliferation for cancer treatment. Nobiletin (NOB), a polymethoxyflavone phytochemical, is present abundantly in citrus peels and has been reported to possess anti-cancer activity. In this study, we investigated the anti-leukemic effects of NOB on cell differentiation and its underlying mechanisms in human chronic myeloid leukemia (CML) K562 cells. NOB (100 μM) treatment for 24 and 48 h significantly decreased viability of K562 cells to 54.4 ± 5.3% and 46.2 ± 9.9%, respectively. NOB (10–100 μM) significantly inhibited cell growth in K562 cells. Flow cytometry analysis and immunoblotting data showed that NOB (40 and 80 μM) could modulate the cell cycle regulators including p21, p27, and cyclin D2, and induce G1 phase arrest. NOB also increased the messenger RNA (mRNA) and protein expression of megakaryocytic differentiation markers, such as CD61, CD41, and CD42 as well as the formation of large cells with multi-lobulated nuclei in K562 cells. These results suggested that NOB facilitated K562 cells toward megakaryocytic differentiation. Furthermore, microarray analysis showed that expression of EGR1, a gene associated with promotion of megakaryocytic differentiation, was markedly elevated in NOB-treated K562 cells. The knockdown of EGR1 expression by small interference RNA (siRNA) could significantly attenuate NOB-mediated cell differentiation. We further elucidated that NOB induced EGR1 expression and CD61 expression through increases in MAPK/ERK phosphorylation in K562 cells. These results indicate that NOB promotes megakaryocytic differentiation through the MAPK/ERK pathway-dependent EGR1 expression in human CML cells. In addition, NOB when combined with imatinib could synergistically reduce the viability of K562 cells. Our findings suggest that NOB may serve as a beneficial anti-leukemic agent for differentiation therapy.

Combined tazemetostat and MAPKi enhances differentiation of papillary thyroid cancer cells harbouring BRAFV600E by synergistically decreasing global trimethylation of H3K27

Clinical efficacy of differentiation therapy with mitogen-activated protein kinase inhibitors (MAPKi) for lethal radioiodine-refractory papillary thyroid cancer (RR-PTC) urgently needs to be improved and the aberrant trimethylation of histone H3 lysine 27 (H3K27) plays a vital role in BRAF^V600E -MAPK-induced cancer dedifferentiation and drug resistance. Therefore, dual inhibition of MAPK and histone methyltransferase (EZH2) may produce more favourable treatment effects. In this study, BRAF^V600E -mutant (BCPAP and K1) and BRAF-wild-type (TPC-1) PTC cells were treated with MAPKi (dabrafenib or selumetinib) or EZH2 inhibitor (tazemetostat), or in combination, and the expression of iodine-metabolizing genes, radioiodine uptake, and toxicity were tested. We found that tazemetostat alone slightly increased iodine-metabolizing gene expression and promoted radioiodine uptake and toxicity, irrespective of the BRAF status. However, MAPKi induced these effects preferentially in BRAF^V600E mutant cells, which was robustly strengthened by tazemetostat incorporation. Mechanically, MAPKi-induced decrease of trimethylation of H3K27 was evidently intensified by tazemetostat in BRAF^V600E -mutant cells. In conclusion, tazemetostat combined with MAPKi enhances differentiation of PTC cells harbouring BRAF^V600E through synergistically decreasing global trimethylation of H3K27, representing a novel differentiation strategy.

Suppressing the metastatic properties of the breast cancer cells using STAT3 decoy oligodeoxynucleotides: A promising approach for eradication of cancer cells by differentiation therapy

Due to the presence of cancer stem cells (CSCs), breast cancer often relapsed after conventional therapies. Strategies that induce differentiation of CSCs will be helpful in eradication of tumor cells, so we designed an oligodeoxynucleotide (ODNs) for targeting of signal transducer and activator of transcription 3 (STAT3) transcription factor which is involved in stemness, and constitutively activated in triple-negative breast cancer. Molecular docking and electrophoretic mobility shift assay analysis showed that decoy ODN bound specifically to the DNA binding site of STAT3 protein. The prevalent uptake of Cy3-labeled ODNs is in the cytoplasm and the nucleus of MDA-MB-231 treated cells. STAT3 decoy ODNs treatment showed cell growth inhibition by decreasing cell viability (17%), increasing the percentage of arrested cells in G0/G1 phases (18%), and triggering apoptosis (29%). Migration and invasion potential decreased from 10.77 to 6.76 µm/hr, by wound closure rate, and migrated/invaded percentage by 26.4% and 15.4% in the transwell assays, respectively. CD44 protein expression level on the cell surface also decreased, while CD24 increased. Mammosphere formation efficiency reduced in terms of tumorsphere size by 47%, while the required time increased. Cells morphology was changed, and lipid droplets were accumulated in the cytoplasm compared to the control and scrambled groups, in all assays (repeated triplicate). Furthermore, the gene expression of all downstream targets significantly decreased owing to suppressing the STAT3 transcription factor. Overall, the results confirmed the antitumor effects of STAT3 decoy in MDA-MB-231 cells. Thus, it seems that STAT3 decoy ODNs might be considered as an auxiliary tool for breast cancer eradicating by the differentiation therapy approach.

Re-programing Chromatin with a Bifunctional LSD1/HDAC Inhibitor Induces Therapeutic Differentiation in DIPG

H3K27M mutations resulting in epigenetic dysfunction are frequently observed in diffuse intrinsic pontine glioma (DIPGs), an incurable pediatric cancer. We conduct a CRISPR screen revealing that knockout of KDM1A encoding lysine-specific demethylase 1 (LSD1) sensitizes DIPG cells to histone deacetylase (HDAC) inhibitors. Consistently, Corin, a bifunctional inhibitor of HDACs and LSD1, potently inhibits DIPG growth in vitro and in xenografts. Mechanistically, Corin increases H3K27me3 levels suppressed by H3K27M histones, and simultaneously increases HDAC-targeted H3K27ac and LSD1-targeted H3K4me1 at differentiation-associated genes. Corin treatment induces cell death, cell-cycle arrest, and a cellular differentiation phenotype and drives transcriptional changes correlating with increased survival time in DIPG patients. These data suggest a strategy for treating DIPG by simultaneously inhibiting LSD1 and HDACs.

Comparison of survivor scores for differentiation therapy of cancer to those for checkpoint inhibition: Half full or half empty

Differentiation therapy is directed to the self-renewing cancer stem cells, as well as their progeny transit amplifying cells, to force them to mature to terminal differentiation. Differentiation therapy is effective in treatment of neuroblastomas and myeloid leukemias. Checkpoint inhibition therapy removes blocks to cancer reactive T-killer cells and allows them to react to malignant cells and limit the growth of cancer. The percentage of patients with a given cancer that responds to either therapy is less than hoped for, and the duration of response is variable. Multiplying the response rate (percentage of patients responding to therapy) by the duration of response may be used to derive a survival score for patients treated with differentiation therapy or checkpoint inhibition. By this criterion, differentiation therapy gives better survival scores than checkpoint inhibition. Yet, checkpoint inhibition is considered a great success, mostly because it may be applied to many different types of cancer, and differentiation therapy is considered relatively ineffective because it is limited to a few specific cancers. On the other hand, the cost of checkpoint inhibition treatment is 10-20 times more per patient than that of differentiation therapy. Hopefully, future combined treatments and advances in both approaches will increase the effectiveness of these cancer treatments.

Myc Decoy Oligodeoxynucleotide Inhibits Growth and Modulates Differentiation of Mouse Embryonic Stem Cells as a Model of Cancer Stem Cells

BACKGROUND

Myc (c-Myc) alone activates the embryonic stem cell-like transcriptional module in both normal and transformed cells. Its dysregulation might lead to increased cancer stem cells (CSCs) population in some tumor cells.

OBJECTIVE

In order to investigate the potential of Myc decoy oligodeoxynucleotides for differentiation therapy, mouse embryonic stem cells (mESCs) were used in this study as a model of CSCs. To our best of knowledge this is the first report outlining the application of Myc decoy in transcription factor decoy "TFD" strategy for inducing differentiation in mESCs.

METHODS

A 20-mer double-stranded Myc transcription factor decoy and scrambled oligodeoxynucleotides (ODNs) were designed, analyzed by electrophoretic mobility shift (EMSA) assay and transfected into the mESCs under 2 inhibitors (2i) condition. Further investigations were carried out using fluorescence and confocal microscopy, cell proliferation and apoptosis analysis, alkaline phosphatase and embryoid body formation assay, real-time PCR and western blotting.

RESULTS

EMSA data showed that Myc decoy ODNs bound specifically to c-Myc protein. They were found to be localized in both cytoplasm and nucleus of mESCs. Our results revealed the potential capability of Myc decoy ODNs to decrease cell viability by (16.1±2%), to increase the number of cells arrested in G0/G1 phases and apoptosis by (14.2±3.1%) and (12.1±3.2%), respectively regarding the controls. Myc decoy could also modulate differentiation in mESCs despite the presence of 2i/LIF in our medium the presence of 2i/LIF in our medium.

CONCLUSION

The optimized Myc decoy ODNs approach might be considered as a promising alternative strategy for differentiation therapy investigations.

Negative regulation of miR-1275 by H3K27me3 is critical for glial induction of glioblastoma cells

Activation of the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway induces glial differentiation of glioblastoma (GBM) cells, but the mechanism by which microRNA (miRNA) regulate this process remains poorly understood. In this study, by performing miRNA genomics and loss- and gain-of-function assays in dibutyryl-cAMP-treated GBM cells, we identified a critical negative regulator, hsa-miR-1275, that modulates a set of genes involved in cancer progression, stem cell maintenance, and cell maturation and differentiation. Additionally, we confirmed that miR-1275 directly and negatively regulates the protein expression of glial fibrillary acidic protein (GFAP), a marker of mature astrocytes. Of note, tri-methyl-histone H3 (Lys27) (H3K27me3), downstream of the PKA/polycomb repressive complex 2 (PRC2) pathway, accounts for the downregulation of miR-1275. Furthermore, decreased miR-1275 expression and induction of GFAP expression were also observed in dibutyryl-cAMP-treated primary cultured GBM cells. In a patient-derived glioma stem cell tumor model, a cAMP elevator and an inhibitor of H3K27me3 methyltransferase inhibited tumor growth, induced differentiation, and reduced expression of miR-1275. In summary, our study shows that epigenetic inhibition of miR-1275 by the cAMP/PKA/PRC2/H3K27me3 pathway mediates glial induction of GBM cells, providing a new mechanism and novel targets for differentiation-inducing therapy.

Dual Delivery of HNF4α and Cisplatin by Mesoporous Silica Nanoparticles Inhibits Cancer Pluripotency and Tumorigenicity in Hepatoma-Derived CD133-Expressing Stem Cells

Hepatocellular carcinoma (HCC) is one of the most prevalent and deadly malignancies characterized by high rate of recurrence. Tumor recurrence is often attributed to the presence of a subpopulation of cells with stem cell properties, referred to as cancer stem cells (CSCs). Traditionally, cancer therapies target the entire bulk of tumor cells; however, they are poorly effective against CSCs, characterized by higher drug resistance. Therefore, approaches targeting CSCs may be required in addition to conventional chemotherapy to prevent tumor recurrence. In this study, we investigated an approach to target HCC by combining the conventional chemotherapeutic drug, cisplatin, to target the bulk of tumor cells, and differentiation therapy by delivering the gene encoding HNF4α, an important regulator of hepatocyte differentiation, to target CSCs. We used the Huh7 cell line as an in vitro model of HCC, which is characterized by a high proportion of CD133-expressing CSCs. By using flow cytometry, we separated CD133⁺ and CD133^- Huh7 cell subpopulations and have shown that the former has highly pronounced in vivo tumorigenic capacity in contrast to the latter, which could not generate tumors in vivo. For the dual delivery of HNF4α-encoding plasmid and cisplatin, we used polyethyleneimine-modified mesoporous silica nanoparticles (PMSNs) as the nanocarriers. Here, we show that the treatment of CD133-expressing Huh7 cells with HNF4α-loaded PMSNs can suppress their proliferation rate, decrease the proportion of CSCs, downregulate stemness-associated genes, and increase the expression of mature hepatocyte-associated genes. At the same time, the treatment of Huh7 with PMSNs loaded with both HNF4α-encoding plasmid and cisplatin could block them in the S-phase of the cell cycle and cause apoptosis. In addition, dually loaded PMSNs were the most efficient formulation in suppressing tumor growth in vivo. To summarize, in this study, we tested the nanoparticle-based delivery system as both chemotherapy and gene-based therapy agents, which has great potential for development of effective treatment of HCC.

Combining peptide TNIIIA2 with all-trans retinoic acid accelerates N-Myc protein degradation and neuronal differentiation in MYCN-amplified neuroblastoma cells

Neuroblastoma is one of the common solid tumors of childhood. Nearly half of neuroblastoma patients are classified into the high-risk group, and their 5-year event-free survival (EFS) rates remain unsatisfactory in the range of 30-40%. High-risk neuroblastoma is characterized by amplification of the MYCN gene and excessive expression of its protein product, N-Myc. Because N-Myc is a transcription factor for various pro-proliferative proteins, the excessive expression causes aberrant or blocked neuronal differentiation during development of sympathetic nervous system, which is a central aspect of neuroblastoma genesis. The current main treatment for high-risk neuroblastoma is intensive chemotherapy using anti-cancer drugs that induce apoptosis in tumor cells, but intensive chemotherapy has another serious risk of long-lasting side effects, so-called "late effects", that occur many years after chemotherapy has ended. As a solution for such situation, differentiation therapy has been expected as a mild chemotherapy with a low risk of late effects, and an application of retinoic acid (RA) and its derivatives as treatment for high-risk neuroblastoma has long been attempted. However, the clinical outcome has not been sufficient with the use of retinoids, including all-trans retinoic acid (ATRA), mainly because of the inhibition of differentiation caused by N-Myc. In the present study, we succeeded in synergistically accelerating the ATRA-induced neuronal differentiation of MYCN-amplified neuroblastoma cells by combining a peptide derived from tenascin-C, termed TNIIIA2, which has a potent ability to activate β1-integrins. Accelerated differentiation was caused by a decrease in N-Myc protein level in neuroblastoma cells after the combined treatment of TNIIIA2 with ATRA. That is, combination treatment using ATRA with TNIIIA2 induced proteasomal degradation in the N-Myc oncoprotein of neuroblastoma cells with MYCN gene amplification, and this caused acceleration of neuronal differentiation and attenuation of malignant properties. Furthermore, an in vivo experiment using a xenograft mouse model showed a therapeutic potential of the combination administration of ATRA and TNIIIA2 for high-risk neuroblastoma. These results provide a new insight into differentiation therapy for high-risk neuroblastoma based on N-Myc protein degradation.

Gain Fat-Lose Metastasis: Converting Invasive Breast Cancer Cells into Adipocytes Inhibits Cancer Metastasis

Cancer cell plasticity facilitates the development of therapy resistance and malignant progression. De-differentiation processes, such as an epithelial-mesenchymal transition (EMT), are known to enhance cellular plasticity. Here, we demonstrate that cancer cell plasticity can be exploited therapeutically by forcing the trans-differentiation of EMT-derived breast cancer cells into post-mitotic and functional adipocytes. Delineation of the molecular pathways underlying such trans-differentiation has motivated a combination therapy with MEK inhibitors and the anti-diabetic drug Rosiglitazone in various mouse models of murine and human breast cancer in vivo. This combination therapy provokes the conversion of invasive and disseminating cancer cells into post-mitotic adipocytes leading to the repression of primary tumor invasion and metastasis formation.

Efficiency of All-Trans Retinoic Acid on Gastric Cancer: A Narrative Literature Review

Gastric cancer (GC) is the third leading cause of cancer-related death worldwide with a five-year survival rate of around 25%, and 4% when diagnosed at a metastatic stage. Cancer stem cells (CSC) have recently been characterized as being responsible for resistance to radio/chemotherapies and metastasis formation, opening up perspectives for new targeted therapies. Those CSCs express biomarkers such as cluster of differentiation 44 (CD44) and display high aldehyde dehydrogenase activity that converts vitamin A-derived retinal into retinoic acids. All-trans retinoic acid (ATRA), which has pro-differentiating properties, has revolutionized the prognosis of acute promyelotic leukemia by increasing its remission rate from 15% to 85%. Recent studies have started to show that ATRA also has an anti-tumoral role on solid cancers such as GC. The purpose of this review is therefore to summarize the work that evaluated the effects of ATRA in GC and to evaluate whether its anti-cancerous action involves gastric CSCs targeting. It has been demonstrated that ATRA can block the cell cycle, enhance apoptosis, and decrease gastric CSCs properties in GC cell lines, tumorspheres, and patient-derived xenograft mice models. Therefore, retinoids and new synthetic retinoids seem to be a promising step forward in targeted therapy of gastric CSC in combination with existing chemotherapies. Future studies should probably focus on these points.

NUT Carcinoma: Clinicopathologic features, pathogenesis, and treatment

NUT carcinoma (NC) is a rare, aggressive subtype of squamous cell carcinoma defined by rearrangement of the NUTM1 (aka NUT) gene. NC is driven by NUT-fusion oncoproteins resulting from chromosomal translocation, most commonly BRD4-NUT. This is a nearly uniformly lethal cancer affecting patients of all ages, but predominantly teens and young adults. The cell of origin is unknown, but NC most commonly arises within the thorax and head and neck. NC typically consists of sheets of monomorphic primitive round cells that can exhibit focal abrupt squamous differentiation. Diagnosis of NC is easy, and can be established by positive NUT nuclear immunohistochemical staining. Though characterization of the NUTM1-fusion gene is desirable by molecular analysis, it is not required for the diagnosis. The increasingly widespread availability of the NUT diagnostic test is leading to increasing diagnoses of this vastly underdiagnosed disease. The NUT midline carcinoma registry (www.NMCRegistry.org) serves as a central repository that has provided the main source of clinical and outcomes data for NC. Currently there is no effective therapy for NC, however small molecules directly targeting the BRD4 portion of BRD4-NUT, termed BET bromodomain inhibitors, have shown activity.

Identification and differentiation therapy strategy of pterygium in vitro

Pterygium is an invasive hyperplasia, resulting from the hyper-proliferation of epithelial cells in cornea. The aim of our present study is to identify stem cells derived from pterygiums and detect differentiation strategy of the pterygium stem cells in vitro. Fundamental properties of the cultured pterygium stem cells were mainly studied using immunofluorescence staining. While clone formation and MTT assay were utilized to evaluate the cell viability. Pterygium stem cells could be cultivated easily, expanded efficiently, but expressed multilineage stem cell markers, which could be differentiated into neuron, osteocytes and adipocytes in vitro. Pterygium-derived spheres expressed stem cell markers and the epithelial-mesenchymal transition markers after treating with the inducing assays. Proliferation and viability of pterygium stem cells could be inhibited after inducing differentiation indicating that differentiation strategy will be a promising strategy in future therapies of pterygium. Cells derived from pterygiums express multilineage stem cell markers and could be induced differentiation. Differentiation therapy strategy could inhibit pterygium stem cell in vitro.