Control Of Cell Proliferation Research Articles

Effects of ERK1/2 Inhibitors on the Growth of Acute Leukemia Cells.

Extracellular signal-regulated kinases (ERK)1/2 are important regulatory proteins that control cell proliferation and survival, playing a significant role in cancer progression, metastasis, and chemoresistance. This study investigated the effects of ERK1/2 inhibitors on the in vitro growth of acute leukemia cell lines. Three ERK1/2 inhibitors were used: SCH772984, temuterkib (LY3214996), and ulixertinib (BVD-523). Four acute myeloid leukemia cell lines (OCI/AML3, HL-60, THP-1, and U-937) and two T-lymphoblastic leukemia cell lines (Jurakt and KOPT-K1) were treated with these inhibitors. Cell growth was assessed using a colorimetric assay, and cell-cycle progression and apoptosis were analyzed using flow cytometry. The expression of intracellular signaling proteins was evaluated via immunoblotting. The effects of small interfering RNA (siRNA)-mediated ERK1/2 knockdown were also evaluated. The inhibitors suppressed the growth of three leukemia cell lines (OCI/AML3, HL-60, and THP-1) harboring neuroblastoma rat sarcoma virus (NRAS) mutations. Growth suppression occurred through G0/G1 arrest in all three cell lines and through apoptosis in OCI/AML3 cells. Immunoblotting demonstrated that these inhibitors suppressed the expression of MYC proto-oncogene, bHLH transcription factor (MYC), in the three cell lines. The additional molecular mechanisms of growth suppression varied depending on the specific inhibitor and cell line. The inhibitors had milder suppressive effects on normal lymphocytes compared to the leukemia cell lines. ERK1/2 inhibitors may serve as novel molecular-targeted drugs for treating leukemia with NRAS mutations.

YAP/TAZ Signalling Controls Epidermal Keratinocyte Fate

The paralogues Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) control cell proliferation and cell fate determination from embryogenesis to ageing. In the skin epidermis, these proteins are involved in both homeostatic cell renewal and injury-induced regeneration and also drive carcinogenesis and other pathologies. YAP and TAZ are usually considered downstream of the Hippo pathway. However, they are the central integrating link for the signalling microenvironment since they are involved in the interplay with signalling cascades induced by growth factors, cytokines, and physical parameters of the extracellular matrix. In this review, we summarise the evidence on how YAP and TAZ are activated in epidermal keratinocytes; how YAP/TAZ-mediated signalling cooperates with other signalling molecules at the plasma membrane, cytoplasmic, and nuclear levels; and how YAP/TAZ ultimately controls transcription programmes, defining epidermal cell fate.

Abstract PR012: A first-in-class EGFR-directed KRAS G12V selective inhibitor

Abstract The KRAS proto-oncogene encodes a small GTPase that is crucial for the activation of intracellular signaling pathways that control cell proliferation, survival and differentiation. KRAS is frequently mutated in cancer resulting in its constitutive activation and dysregulation of downstream signaling pathways that drive oncogenic transformation. KRAS G12V is the second most common KRAS mutation in cancer, and occurs frequently in lung, colon and pancreatic cancers. However, while significant advancements have been made in developing KRAS G12C, G12D and pan-KRAS inhibitors, there remain no direct KRAS G12V inhibitors in the clinic. Due to challenges targeting oncogenes with traditional small molecule approaches, RNA interference (RNAi) has become an attractive therapeutic approach for many oncogenes. RNAi has faced many obstacles as an effective cancer therapeutics, including the lack of cancer- specific tissue targeting, rapid oligonucleotide nuclease degradation and clearance from circulation, the need for endosomal escape, and unwanted immune stimulation. However, recently, the use of targetable ligands conjugated to chemically modified siRNAs have shown promise in circumventing these barriers. Here, we describe the development of EFTX-G12V, a fully-modified, mutant-selective siRNA conjugated to an EGFR ligand that shows improved tumor delivery and significant anti-tumor activity in lung and colon cancer models. We used a structure-activity relationship screening approach to identify a highly mutant-selective fully chemically modified siRNA that inhibits KRAS G12V expression at both the mRNA and protein level while completely sparing KRAS WT. Furthermore, this siRNA inhibited cancer cell growth in vitro and showed no off-target effects. To address the issue of tumor-specific delivery, we conjugated a non-mitogenic EGFR ligand to the siRNA and found enhanced delivery to tumors with varying levels of EGFR expression. EFTX-G12V significantly inhibited KRAS G12V mRNA and protein in vivo and showed significant anti-tumor activity in lung and colon xenograft models. Importantly, EFTX-G12V showed no off-target effects on WT KRAS in somatic tissues including kidney, skin and bladder. Unexpectedly, we found that mutant-selective targeting showed improved efficacy in comparison to a pan-KRAS siRNA. EFTX-G12V significantly inhibited tumor angiogenesis while pan-KRAS targeting had inconsistent effects suggesting that mutant-selective targeting has advantages within the tumor microenvironment. Together our findings represent a technologic advance in ligand-directed, mutant-selective oncogene targeting using RNAi and reveal new biologic insights in KRAS targeting that may have broader implications with regards to safety and efficacy. Citation Format: Lyla Stanland, Hayden Huggins, Alessandro Porrello, Yogitha Chareddy, Salma Azam, Jillian Perry, Pradeep Pallan, Kristina Whately, Lincy Edatt, Matthew Fleming, Jonah Im, Christina Gutierrez-Ford, Imani Simmons, Vandanaa Jayaprakash, Rani Sellers, Gabriela de la Cruz, Albert Wielgus, Martin Egli, Albert Bowers, Chad Pecot. A first-in-class EGFR-directed KRAS G12V selective inhibitor [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr PR012.

Colorectal carcinoma progression is not influenced by the pseudokinase PEAK1

The scaffold protein PEAK1 acts downstream of integrin adhesion complexes and the epidermal growth factor receptor, orchestrating signaling events that control cell proliferation and cytoskeletal remodeling. In this study we investigated the role of PEAK1 in colorectal carcinoma (CRC) progression using various in vitro and in vivo models to replicate the stepwise pathogenesis of CRC. While we observed a cell-type specific role for PEAK1 in the proliferation and in human CRC cell lines in vitro, our in vivo experiments using different CRC mouse models driven by loss of Apc, with or without oncogenic Kras or Pten loss suggest that PEAK1 does not significantly contribute to tumor formation in vivo. However, the survival time of Peak1−/− mice in the Apcfl/+ model appeared to be slightly increased. Furthermore, PEAK1 promotes EGF-induced Caco-2 cell proliferation and regulates spheroid polarization and lumenization. Given that the Caco-2 cells harbor mutations in the tumor suppressors APC and β-CATENIN, but not in other tumor suppressors or in proto-oncogenes, we conclude that the PEAK1’s impact on colon carcinogenesis is limited, potentially playing a role in the initial stage of the adenoma to carcinoma progression.

Nuclear-Targeting Peptides for Cancer Therapy.

Nucleus is the central regulator of cells that controls cell proliferation, metabolism, and cell cycle, and is considered the most important organelle in cells. The precision medicine that can achieve nuclear targeting has achieved good therapeutic effects in anti-tumor therapy. However, the presence of biological barriers such as cell membranes and nuclear membranes in cells limit the delivery of therapeutic agents to the nucleus. Therefore, developing effective nuclear-targeting drug delivery strategies is particularly important. Nuclear-targeting peptides are a class of functional peptides that can penetrate cell membranes and target the nucleus. They mainly recognize and bind to the nuclear transport molecules (such as Importin-α/β) and transport the therapeutic agents to the nucleus through nuclear pore complexes (NPC). This review summarizes the most recent developments of strategies for anti-tumor therapy utilizing nuclear-targeting peptides, which will ultimately contribute to the development of more effective nuclear-targeting strategies to achieve better anti-tumor outcomes.

Signaling roles of sphingolipids in the ischemic brain and their potential utility as therapeutic targets

Sphingolipids comprise a class of lipids, which are composed of a sphingoid base backbone and are essential structural components of cell membranes. Beyond their role in maintaining cellular integrity, several sphingolipids are pivotally involved in signaling pathways controlling cell proliferation, differentiation, and death. The brain exhibits a particularly high concentration of sphingolipids and dysregulation of the sphingolipid metabolism due to ischemic injury is implicated in consecutive pathological events. Experimental stroke studies revealed that the stress sphingolipid ceramide accumulates in the ischemic brain post-stroke. Specifically, counteracting ceramide accumulation protects against ischemic damage and promotes brain remodeling, which translates into improved behavioral outcome. Sphingomyelin substantially influences cell membrane fluidity and thereby controls the release of extracellular vesicles, which are important vehicles in cellular communication. By modulating sphingomyelin content, these vesicles were shown to contribute to behavioral recovery in experimental stroke studies. Another important sphingolipid that influences stroke pathology is sphingosine-1-phosphate, which has been attributed a pro-angiogenic function, that is presumably mediated by its effect on endothelial function and/or immune cell trafficking. In experimental and clinical studies, sphingosine-1-phosphate receptor modulators allowed to modify clinically significant stroke recovery. Due to their pivotal roles in cell signaling, pharmacological compounds modulating sphingolipids, their enzymes or receptors hold promise as therapeutics in human stroke patients.

Neurodevelopmental functions and activities of the KAT3 class of lysine acetyltransferases.

The human lysine acetyltransferases KAT3A (CREBBP) and KAT3B (EP300) are essential enzymes in gene regulation in the nucleus. Their ubiquitous expression in metazoan cell types controls cell proliferation and differentiation during development. This comprehensive review delves into the biological roles of KAT3A and KAT3B in neurodevelopment, shedding light on how alterations in their regulation or activity can potentially contribute to a spectrum of neurodegenerative diseases (e.g., Huntington's and Alzheimer's). We explore the pathophysiological implications of KAT3 function loss in these disorders, considering their conserved protein domains and biochemical functions in chromatin regulation. The discussion also underscores the crucial role of KAT3 proteins and their substrates in supporting the integration of key cell signaling pathways. Furthermore, the narrative highlights the interdependence of KAT3-mediated lysine acetylation with lysine methylation and arginine methylation. From a cellular perspective, KAT3-dependent signal integration at subnuclear domains is mediated by liquid-liquid phase separation in response to KAT3-mediated lysine acetylation. The disruption of these finely tuned regulatory processes underscores their pathological roles in neurodegeneration. This review also points to the exciting potential for future research in this field, inspiring further investigation and discovery in the area of neurodevelopment and neurodegenerative diseases.

MiR-927 regulates insect wing development by targeting the Hippo pathway.

How organ size is determined is a fundamental question in life sciences. Recent studies have highlighted the importance of the Hippo pathway in regulating organ size. This pathway controls cell proliferation and cell death to maintain the proper number of cells. The activity of the Hippo pathway is tightly fine-tuned through various post-translational modifications, such as phosphorylation and ubiquitination. Here, we discover that miR-927 is a novel regulator of wing size. Overexpression of miR-927 decreases wing size, which can be rescued by co-expressing miR-927-sponge. Next, we show that miR-927 stimulates apoptosis and suppresses the expression of Drosophila inhibitor of apoptosis protein 1, a well-known target gene of the Hippo pathway. Genetic epistatic analyses position miR-927 upstream of Yorkie (Yki) to modulate the Hippo pathway. In addition, there is a matching miR-927 seed site in the yki 3' untranslated region (3'-UTR), and we demonstrate that yki 3'-UTR is the direct target of miR-927. Ultimately, our study reveals that the targeting of yki by miR-927 to regulate the Hippo pathway is conserved in Helicoverpa armigera. Administration of miR-927 via star polycation (SPc) nanocarrier effectively inhibits wing development in H. armigera. Taken together, our findings uncover a novel mechanism by which Yki is silenced at the post-transcriptional level by miR-927, and provide a new perspective on pest management.

Suppression of ferroptosis by vitamin A or radical-trapping antioxidants is essential for neuronal development

The development of functional neurons is a complex orchestration of multiple signaling pathways controlling cell proliferation and differentiation. Because the balance of antioxidants is important for neuronal survival and development, we hypothesized that ferroptosis must be suppressed to gain neurons. We find that removal of antioxidants diminishes neuronal development and laminar organization of cortical organoids, which is fully restored when ferroptosis is inhibited by ferrostatin-1 or when neuronal differentiation occurs in the presence of vitamin A. Furthermore, iron-overload-induced developmental growth defects in C. elegans are ameliorated by vitamin E and A. We determine that all-trans retinoic acid activates the Retinoic Acid Receptor, which orchestrates the expression of anti-ferroptotic genes. In contrast, retinal and retinol show radical-trapping antioxidant activity. Together, our study reveals an unexpected function of vitamin A in coordinating the expression of essential cellular gatekeepers of ferroptosis, and demonstrates that suppression of ferroptosis by radical-trapping antioxidants or by vitamin A is required to obtain mature neurons and proper laminar organization in cortical organoids.

Herbal medicine exhibiting cell cycle arrest: A short review

Cancer treatment often involves the use of chemotherapy, which can have significant side effects. Herbal medicines have been used for centuries and have shown potential as sources of new therapeutic agents. This review explores the role of specific herbal medicines, such as ginseng, curcumin, berberine, epigallocatechin gallate (EGCG), and quercetin, in inducing cell cycle arrest, a mechanism that controls cell proliferation. The review discusses the molecular mechanisms underlying these effects, their potential in combination with chemotherapy, and their implications for clinical application in cancer therapy. The combination of herbal medicines with conventional chemotherapeutic agents can result in synergistic effects that enhance therapeutic efficacy. However, there are challenges in terms of standardization, safety evaluation, and the need for more research to understand the molecular mechanisms and optimize treatment protocols. With further investigation and clinical validation, herbal-drug combination therapies could have a significant impact on cancer treatment.

Development and tissue specific expression of RAPGEF1 (C3G) transcripts having exons encoding disordered segments with predicted regulatory function.

The ubiquitously expressed Guanine nucleotide exchange factor, RAPGEF1 (C3G), is essential for early development of mouse embryos. It functions to regulate gene expression and cytoskeletal reorganization, thereby controlling cell proliferation and differentiation. While multiple transcripts have been predicted, their expression in mouse tissues has not been investigated in detail. Full length RAPGEF1 isoforms primarily arise due to splicing at two hotspots, one involving exon-3, and the other involving exons 12-14 incorporating amino acids immediately following the Crk binding region of the protein. These isoforms vary in expression across embryonic and adult organs. We detected the presence of unannotated, and unpredicted transcripts with incorporation of cassette exons in various combinations, specifically in the heart, brain, testis and skeletal muscle. Isoform switching was detected as myocytes in culture and mouse embryonic stem cells were differentiated to form myotubes, and embryoid bodies respectively. The cassette exons encode a serine-rich polypeptide chain, which is intrinsically disordered, and undergoes phosphorylation. In silico structural analysis using AlphaFold indicated that the presence of cassette exons alters intra-molecular interactions, important for regulating catalytic activity. LZerD based docking studies predicted that the isoforms with one or more cassette exons differ in interaction with their target GTPase, RAP1A. Our results demonstrate the expression of novel RAPGEF1 isoforms, and predict cassette exon inclusion as an additional means of regulating RAPGEF1 activity in various tissues and during differentiation.

The signature genes of cuproptosis associates with tumor immune microenvironment and predicts prognosis in kidney renal clear cell carcinoma.

Cuproptosis is a new form of cell death, which has great potential to be developed in tumors treatment. Our study aimed to explore the predictive value of cuproptosis-related genes (CRGs) in various cancers, with a focus on kidney renal clear cell carcinoma (KIRC). A total of 9502 pan-cancer patients from TCGA cohort were enrolled. The relationships between CRGs and overall survival (OS) or disease-free survival (DFS) were analyzed. Gene Set Variation Analysis (GSVA) enrichment analysis was performed to explore the expression differences of CRGs. Multivariate Cox regression analysis was used to evaluate the association between GSVA scores and patient survival. KEGG and GO analyses were employed to identify the biological functions and pathways. The expression and prognostic characteristics of FDX1 were examined to evaluate the correlation between FDX1 and KIRC. Cell experiments were conducted to verify whether FDX1 was involved in cuproptosis of Caki-1 cells induced by Elesclomol. Positive cuproptosis signature genes(pos.cu.sig) exhibited the correlation with prognosis in KIRC, and all of these genes showed differential expression between KIRC and normal tissues. The GSVA score of pos.cu.sig was associated with excellent survival (HR=0.61, P<0.05), which can also serve as an independent prognostic factor for KIRC. There was a close correlation between pos.cu.sig and the tumor immune microenvironment in KIRC by KEGG and GO analysis. FDX1 expression was correlated with KIRC grade and positively associated with prognosis in KIRC patients. Compared with the control group, cell proliferation and migration were significantly inhibited, FDX1 expression was up-regulated, and Fe-S cluster protein content was decreased of Caki-1 cells after Elesclomol treatment. This study provides compelling evidence that cuproptosis is closely linked to the prognosis of KIRC. FDX1 holds promise as a viable biomarker and therapeutic target for assessing the effectiveness of tumor immunotherapy in KIRC.

Cladosporols and PPARγ: Same Gun, Same Bullet, More Targets.

Several natural compounds have been found to act as PPARγ agonists, thus regulating numerous biological processes, including the metabolism of carbohydrates and lipids, cell proliferation and differentiation, angiogenesis, and inflammation. Recently, Cladosporols, secondary metabolites purified from the fungus Cladosporium tenuissimum, have been demonstrated to display an efficient ability to control cell proliferation in human colorectal and prostate cancer cells through a PPARγ-mediated modulation of gene expression. In addition, Cladosporols exhibited a strong anti-adipogenetic activity in 3T3-L1 murine preadipocytes, preventing their in vitro differentiation into mature adipocytes. These data interestingly point out that the interaction between Cladosporols and PPARγ, in the milieu of different cells or tissues, might generate a wide range of beneficial effects for the entire organism affected by diabetes, obesity, inflammation, and cancer. This review explores the molecular mechanisms by which the Cladosporol/PPARγ complex may simultaneously interfere with a dysregulated lipid metabolism and cancer promotion and progression, highlighting the potential therapeutic benefits of Cladosporols for human health.

Positive regulation of Hedgehog signaling via phosphorylation of GLI2/GLI3 by DYRK2 kinase

Hedgehog (Hh) signaling, an evolutionarily conserved pathway, plays an essential role in development and tumorigenesis, making it a promising drug target. Multiple negative regulators are known to govern Hh signaling; however, how activated Smoothened (SMO) participates in the activation of downstream GLI2 and GLI3 remains unclear. Herein, we identified the ciliary kinase DYRK2 as a positive regulator of the GLI2 and GLI3 transcription factors for Hh signaling. Transcriptome and interactome analyses demonstrated that DYRK2 phosphorylates GLI2 and GLI3 on evolutionarily conserved serine residues at the ciliary base, in response to activation of the Hh pathway. This phosphorylation induces the dissociation of GLI2/GLI3 from suppressor, SUFU, and their translocation into the nucleus. Loss of Dyrk2 in mice causes skeletal malformation, but neural tube development remains normal. Notably, DYRK2-mediated phosphorylation orchestrates limb development by controlling cell proliferation. Taken together, the ciliary kinase DYRK2 governs the activation of Hh signaling through the regulation of two processes: phosphorylation of GLI2 and GLI3 downstream of SMO and cilia formation. Thus, our findings of a unique regulatory mechanism of Hh signaling expand understanding of the control of Hh-associated diseases.

New solutions of time-fractional cancer tumor models using modified He-Laplace algorithm

Cancer develops through cells when mutations build up in different genes that control cell proliferation. To treat these abnormal cells and minimize their growth, various cancer tumor samples have been modeled and analyzed in literature. The current study is focused on the investigation of more generalized cancer tumor model in fractional environment, where net killing rate is taken into account in different domains. Three types of killing rates are considered in the current study including time and position dependent killing rates, and concentration of cells based killing rate. A hybrid mechanism is proposed in which different homotopies are used with perturbation technique and Laplace transform. This leads to a convenient algorithm to tackle all types of fractional derivatives efficiently. The convergence and error bounds of the proposed scheme are computed theoretically by proving related theorems. In the next phase, convergence and validity is analyzed numerically by calculating residual errors round the fractional domain. It is observed that computed errors are very less in the entire fractional domain. Moreover, comparative analysis of Caputo, Caputo-Fabrizio (CF), and Atangana–Baleanu (AB) fractional derivatives is also performed graphically to discern the effect of different fractional approaches on the solution profile. Analysis asserts the reliability of proposed methodology in the matter of intricate fractional tumor models, and hence can be used to other complex physical phenomena.

Unlocking epigenetics for precision treatment of Ewing's sarcoma.

Ewing's sarcoma (EWS) is a highly aggressive malignant bone tumor primarily affecting adolescents and young adults. Despite the efficacy of chemoradiotherapy in some cases, the cure rate for patients with metastatic and recurrent disease remains low. Therefore, there is an urgent need for innovative therapeutic approaches to address the challenges associated with EWS treatment. Epigenetic regulation, a crucial factor in physiological processes, plays a significant role in controlling cell proliferation, maintaining gene integrity, and regulating transcription. Recent studies highlight the importance of abnormal epigenetic regulation in the initiation and progression of EWS. A comprehensive understanding of the intricate interactions between EWS and aberrant epigenetic regulation is essential for advancing clinical drug development. This review aims to provide a comprehensive overview of both epigenetic targets implicated in EWS, integrating various therapeutic modalities to offer innovative perspectives for the clinical diagnosis and treatment of EWS.

Higher YAP1 Levels Are Associated With Shorter Survival of Patients With Low Grade Astrocytoma.

Glioblastoma multiforme (GBM) is one of the most lethal types of brain cancer with a median survival of only 12 months due to its aggressiveness and lack of effective treatment options. Astrocytomas and oligodendrogliomas are classified as low-grade gliomas (LGG) and have the potential to progress into secondary GBM. YAP1 and TAZ are transcriptional co-activators of the hippo pathway and play an important role in tumorigenesis by controlling cell proliferation and differentiation. The aim of this study was to analyze whether YAP1 and TAZ influence the survival in patients with astrocytoma and oligodendroglioma. A total of 22 patient samples of astrocytoma and 11 samples of oligodendroglioma were analyzed using real-time PCR. We utilized open-access data from The Cancer Genome Atlas (TCGA) focusing on "brain lower grade glioma". mRNA expression rates were used to validate our findings on survival analysis. Expression of YAP1 was twice as high in astrocytoma than in oligodendroglioma, whereas there was no difference in TAZ. In oligodendrogliomas, the expression of TAZ was higher in relapsed than in primary tumors. Patients with astrocytoma having a high YAP1 expression had a significantly shorter overall survival than patients with lower expression (median survival 161 vs. 86 months, p=0.0248). These findings were validated with survival analysis of TCGA data. High YAP1 expression shows a high correlation with poorer overall survival in LGG. YAP1 has higher levels of expression in astrocytomas than in oligodendrogliomas.

New Mechanisms Underlying Oncogenesis in Dbl Family Rho Guanine Nucleotide Exchange Factors.

Transmembrane signaling is a critical process by which changes in the extracellular environment are relayed to intracellular systems that induce changes in homeostasis. One family of intracellular systems are the guanine nucleotide exchange factors (GEFs), which catalyze the exchange of GTP for GDP bound to inactive guanine nucleotide binding proteins (G proteins). The resulting active G proteins then interact with downstream targets that control cell proliferation, growth, shape, migration, adhesion, and transcription. Dysregulation of any of these processes is a hallmark of cancer. The Dbl family of GEFs activates Rho family G proteins, which, in turn, alter the actin cytoskeleton and promote gene transcription. Although they have a common catalytic mechanism exercised by their highly conserved Dbl homology (DH) domains, Dbl GEFs are regulated in diverse ways, often involving the release of autoinhibition imposed by accessory domains. Among these domains, the pleckstrin homology (PH) domain is the most commonly observed and found immediately C-terminal to the DH domain. The domain has been associated with both positive and negative regulation. Recently, some atomic structures of Dbl GEFs have been determined that reemphasize the complex and central role that the PH domain can play in orchestrating regulation of the DH domain. Here, we discuss these newer structures, put them into context by cataloging the various ways that PH domains are known to contribute to signaling across the Dbl family, and discuss how the PH domain might be exploited to achieve selective inhibition of Dbl family RhoGEFs by small-molecule therapeutics. SIGNIFICANCE STATEMENT: Dysregulation via overexpression or mutation of Dbl family Rho guanine nucleotide exchange factors (GEFs) contributes to cancer and neurodegeneration. Targeting the Dbl homology catalytic domain by small-molecule therapeutics has been challenging due to its high conservation and the lack of a discrete binding pocket. By evaluating some new autoinhibitory mechanisms in the Dbl family, we demonstrate the great diversity of roles played by the regulatory domains, in particular the PH domain, and how this holds tremendous potential for the development of selective therapeutics that modulate GEF activity.

From Intractable to Treatable: Milestones and Horizons in the Management of HER2+ Breast Cancer

The human epidermal growth factor receptor 2 (HER2) is a member of the epidermal growth factor receptor (EGFR) family that initiates various signalling pathways that control cell proliferation and tumourigenesis. Historically, approximately 15% of breast cancers have been characterized by overexpression or amplification of HER2, known as “HER2+” breast cancers. This subtype has been associated with an adverse prognosis, along with a high risk of recurrence and worse survival outcomes. However, with the discovery and subsequent development of HER2‑targeted therapies, the clinical course of HER2+ breast cancers has fundamentally changed. Optimizing therapeutic strategies using existing and emerging HER2-targeted therapies to build upon these advances remains a major priority for clinical development and treatment delivery. In 1998, the American Food and Drug Administration (FDA) and Health Canada approved trastuzumab, the first HER2-targeted therapy. Trastuzumab, a monoclonal antibody that binds to the HER2 receptor, has demonstrated clinical activity and improved outcomes in patients with metastatic HER2+ breast cancer when combined with chemotherapy. Following soon after, the first trial of adjuvant trastuzumab (HERA) demonstrated improvements in outcomes when combined with chemotherapy for early HER2+ breast cancer. More than 25 years after its first approval, trastuzumab retains a central role in the treatment of both early and advanced HER2+ breast cancer and has provided a backbone for both new therapeutic combinations (eg. with small molecule inhibitors of HER2) and new classes of therapeutic agents (antibody drug conjugates [ADC]). These successors of trastuzumab are currently redefining the HER2+ treatment landscape in both advanced and early breast cancer.

Thymidylate synthase disruption to limit cell proliferation in cell therapies

Stem and progenitor cells hold great promise for regenerative medicine and gene therapy approaches. However, transplantations of living cells entail a fundamental risk of unwanted growth, potentially exacerbated by CRISPR-Cas9 or other genetic manipulations. Here, we describe a safety system to control cell proliferation while allowing robust and efficient cell manufacture, without any added genetic elements. Inactivating TYMS, a key nucleotide metabolism enzyme, in several cell lines resulted in cells that proliferate only when supplemented with exogenous thymidine. Under supplementation, TYMS-/--pluripotent stem cells proliferate, produce teratomas and successfully differentiate into potentially therapeutic cell types such as pancreatic beta-cells. Our results suggest that supplementation with exogenous thymidine affects stem cell proliferation, but not the function of stem cell-derived cells. After differentiation, postmitotic cells do not require thymidine in vitro or in vivo, as shown by the production of functional human insulin in mice up to 5 months after implantation of stem-cell derived pancreatic tissue.