The RAS-Binding Domain of Human BRAF Protein Serine/Threonine Kinase Exhibits Allosteric Conformational Changes upon Binding HRAS

A comprehensive review of targeting RAF kinase in cancer

RAF kinases, particularly the BRAF isoform, play a crucial role in the MAPK/ERK signaling pathway, regulating key cellular processes such as proliferation, differentiation, and survival. Dysregulation of this pathway often caused by mutations in the BRAF gene or alterations in upstream regulators like Ras and receptor tyrosine kinases contributes significantly to cancer development. Mutations, such as BRAF-V600E, are present in a variety of malignancies, with the highest prevalence in melanoma. Targeted therapies against RAF kinases have achieved substantial success, especially in BRAF-V600E-mutant melanomas, where inhibitors like vemurafenib and dabrafenib have demonstrated remarkable efficacy, leading to improved patient outcomes. These inhibitors have also shown clinical benefits in cancers such as thyroid and colorectal carcinoma, although to a lesser extent. Despite these successes, therapeutic resistance remains a major hurdle. Resistance mechanisms, including RAF dimerization, feedback reactivation of the MAPK pathway, and paradoxical activation of ERK signaling, often lead to diminished efficacy over time, resulting in disease progression or even secondary malignancies. In response, current research is focusing on novel therapeutic strategies, including combination therapies that target multiple components of the pathway simultaneously, such as MEK inhibitors used in tandem with RAF inhibitors. Additionally, next-generation RAF inhibitors are being developed to address resistance and enhance therapeutic specificity. This review discusses the clinical advancements in RAF-targeted therapies, with a focus on ongoing efforts to overcome therapeutic resistance and enhance outcomes for cancer patients. It also underscores the persistent challenges in effectively targeting RAF kinase in oncology.

Conformational changes in Protein Kinase A along its activation cycle are rooted in the folding energetics of cyclic-nucleotide binding domains

Cyclic-nucleotide binding (CNB) domains are structurally and evolutionarily conserved signaling modules that regulate proteins with diverse folds and functions. Despite a wealth of structural information, the mechanisms by which CNB domains couple cyclic-nucleotide binding to conformational changes involved in signal transduction remain unknown. Here we combined single-molecule and computational approaches to investigate the conformation and folding energetics of the two CNB domains of the regulatory subunit of protein kinase A (PKA). We found that the CNB domains exhibit different conformational and folding signatures in the apo state, when bound to cAMP, or when bound to the PKA catalytic subunit, underscoring their ability to adapt to different binding partners. Moreover, we show while the two CNB domains have near-identical structures, their thermodynamic coupling signatures are divergent, leading to distinct cAMP responses and differential mutational effects. Specifically, we demonstrate the mutation W260A exerts local and allosteric effects that impact multiple steps of the PKA activation cycle. Taken together, these results highlight the complex interplay between folding energetics, conformational dynamics, and thermodynamic signatures that underlies structurally conserved signaling modules in response to ligand binding and mutational effects.

An update on genomic aberrations in Spitz naevi and tumours

Spitz neoplasms continue to be a diagnostic challenge for dermatopathologists and are defined by distinctive morphological and genetic features. With the recent advancements in genomic sequencing, the classification, diagnosis, and prognostication of these tumours have greatly improved. Several subtypes of Spitz neoplasms have been identified based on their specific genomic aberrations, which often correlate with distinctive morphologies and biological behaviour. These genetic driver events can be classified into four major groups, including: (1) mutations [HRAS mutations (with or without 11p amplification) and 6q23 deletions]; (2) tyrosine kinase fusions (ROS1, ALK, NTRK1-3, MET and RET); (3) serine/threonine kinase fusions and mutations (BRAF, MAP3K8, and MAP2K1); and (4) other rare genomic aberrations. These driver genomic events are hypothesised to enable the initial proliferation of melanocytes and are often accompanied by additional genomic aberrations that affect biological behaviour. The discovery of theses genomic fusions has allowed for a more objective definition of a Spitz neoplasm. Further studies have shown that the majority of morphologically Spitzoid appearing melanocytic neoplasms with aggressive behaviour are in fact BRAF or NRAS mutated tumours mimicking Spitz. Truly malignant fusion driven Spitz neoplasms may occur but are relatively uncommon, and biomarkers such as homozygous 9p21 (CDKN2A) deletions or TERT-p mutations can have some prognostic value in such cases. In this review, we discuss the importance and various methods of identifying Spitz associated genomic fusions to help provide more definitive classification. We also discuss characteristic features of the various fusion subtypes as well as prognostic biomarkers.

Characterisation of a cyclic peptide that binds to the RAS binding domain of phosphoinositide 3-kinase p110α

P110α is a member of the phosphoinositide 3-kinase (PI3K) enzyme family that functions downstream of RAS. RAS proteins contribute to the activation of p110α by interacting directly with its RAS binding domain (RBD), resulting in the promotion of many cellular functions such as cell growth, proliferation and survival. Previous work from our lab has highlighted the importance of the p110α/RAS interaction in tumour initiation and growth. Here we report the discovery and characterisation of a cyclic peptide inhibitor (cyclo-CRVLIR) that interacts with the p110α-RBD and blocks its interaction with KRAS. cyclo-CRVLIR was discovered by screening a "split-intein cyclisation of peptides and proteins" (SICLOPPS) cyclic peptide library. The primary cyclic peptide hit from the screen initially showed a weak affinity for the p110α-RBD (Kd about 360 µM). However, two rounds of amino acid substitution led to cyclo-CRVLIR, with an improved affinity for p110α-RBD in the low µM (Kd 3 µM). We show that cyclo-CRVLIR binds selectively to the p110α-RBD but not to KRAS or the structurally-related RAF-RBD. Further, using biophysical, biochemical and cellular assays, we show that cyclo-CRVLIR effectively blocks the p110α/KRAS interaction in a dose dependent manner and reduces phospho-AKT levels in several oncogenic KRAS cell lines.

The Morpho-Molecular Landscape of Spitz Neoplasms

Spitz neoplasms are a heterogeneous group of melanocytic proliferations with a great variability in the histological characteristics and in the biological behavior. Thanks to recent discoveries, the morpho-molecular landscape of Spitz lineage is becoming clearer, with the identification of subtypes with recurrent features thus providing the basis for a more solid and precise tumor classification. Indeed, specific mutually exclusive driver molecular events, namely HRAS or MAP2K1 mutations, copy number gains of 11p, and fusions involving ALK, ROS, NTRK1, NTRK2, NTRK3, MET, RET, MAP3K8, and BRAF genes, correlate with distinctive histological features. The accumulation of further molecular aberrations, instead, promotes the increasing malignant transformation of Spitz neoplasms. Thus, the detection of a driver genetic alteration can be achieved using the appropriate diagnostic tests chosen according to the histological characteristics of the lesion. This allows the recognition of subtypes with aggressive behavior requiring further molecular investigations. This review provides an update on the morpho-molecular correlations in Spitz neoplasms.

Concurrent Identification and Characterization of Protein Structure and Continuous Internal Dynamics with REDCRAFT

Internal dynamics of proteins can play a critical role in the biological function of some proteins. Several well documented instances have been reported such as MBP, DHFR, hTS, DGCR8, and NSP1 of the SARS-CoV family of viruses. Despite the importance of internal dynamics of proteins, there currently are very few approaches that allow for meaningful separation of internal dynamics from structural aspects using experimental data. Here we present a computational approach named REDCRAFT that allows for concurrent characterization of protein structure and dynamics. Here, we have subjected DHFR (PDB-ID 1RX2), a 159-residue protein, to a fictitious, mixed mode model of internal dynamics. In this simulation, DHFR was segmented into 7 regions where 4 of the fragments were fixed with respect to each other, two regions underwent rigid-body dynamics, and one region experienced uncorrelated and melting event. The two dynamical and rigid-body segments experienced an average orientational modification of 7° and 12° respectively. Observable RDC data for backbone C′-N, N-HN, and C′-HN were generated from 102 uniformly sampled frames that described the molecular trajectory. The structure calculation of DHFR with REDCRAFT by using traditional Ramachandran restraint produced a structure with 29 Å of structural difference measured over the backbone atoms (bb-rmsd) over the entire length of the protein and an average bb-rmsd of more than 4.7 Å over each of the dynamical fragments. The same exercise repeated with context-specific dihedral restraints generated by PDBMine produced a structure with bb-rmsd of 21 Å over the entire length of the protein but with bb-rmsd of less than 3 Å over each of the fragments. Finally, utilization of the Dynamic Profile generated by REDCRAFT allowed for the identification of different dynamical regions of the protein and the recovery of individual fragments with bb-rmsd of less than 1 Å. Following the recovery of the fragments, our assembly procedure of domains (larger segments consisting of multiple fragments with a common dynamical profile) correctly assembled the four fragments that are rigid with respect to each other, categorized the two domains that underwent rigid-body dynamics, and identified one dynamical region for which no conserved structure could be defined. In conclusion, our approach was successful in identifying the dynamical domains, recovery of structure where it is meaningful, and relative assembly of the domains when possible.

The Q61H mutation decouples KRAS from upstream regulation and renders cancer cells resistant to SHP2 inhibitors

Cancer cells bearing distinct KRAS mutations exhibit variable sensitivity to SHP2 inhibitors (SHP2i). Here we show that cells harboring KRAS Q61H are uniquely resistant to SHP2i, and investigate the underlying mechanisms using biophysics, molecular dynamics, and cell-based approaches. Q61H mutation impairs intrinsic and GAP-mediated GTP hydrolysis, and impedes activation by SOS1, but does not alter tyrosyl phosphorylation. Wild-type and Q61H-mutant KRAS are both phosphorylated by Src on Tyr32 and Tyr64 and dephosphorylated by SHP2, however, SHP2i does not reduce ERK phosphorylation in KRAS Q61H cells. Phosphorylation of wild-type and Gly12-mutant KRAS, which are associated with sensitivity to SHP2i, confers resistance to regulation by GAP and GEF activities and impairs binding to RAF, whereas the near-complete GAP/GEF-resistance of KRAS Q61H remains unaltered, and high-affinity RAF interaction is retained. SHP2 can stimulate KRAS signaling by modulating GEF/GAP activities and dephosphorylating KRAS, processes that fail to regulate signaling of the Q61H mutant.

SHP2 promotes RAS-driven MAPK signalling, but it is unclear why cancer cells with distinct KRAS mutations exhibit differential sensitivity to SHP2 inhibition. Here the authors show that KRAS Q61H is decoupled from SHP2- mediated upstream regulation, thus Q61H pancreatic cancer cells maintain MAPK signalling and are refractory to SHP2 inhibitors.

BRAF Gene and Melanoma: Back to the Future

As widely acknowledged, 40-50% of all melanoma patients harbour an activating BRAF mutation (mostly BRAF V600E). The identification of the RAS-RAF-MEK-ERK (MAP kinase) signalling pathway and its targeting has represented a valuable milestone for the advanced and, more recently, for the completely resected stage III and IV melanoma therapy management. However, despite progress in BRAF-mutant melanoma treatment, the two different approaches approved so far for metastatic disease, immunotherapy and BRAF+MEK inhibitors, allow a 5-year survival of no more than 60%, and most patients relapse during treatment due to acquired mechanisms of resistance. Deep insight into BRAF gene biology is fundamental to describe the acquired resistance mechanisms (primary and secondary) and to understand the molecular pathways that are now being investigated in preclinical and clinical studies with the aim of improving outcomes in BRAF-mutant patients.

Raf promotes dimerization of the Ras G-domain with increased allosteric connections

Ras dimerization is critical for Raf activation. Here we show that the Ras binding domain of Raf (Raf-RBD) induces robust Ras dimerization at low surface densities on supported lipid bilayers and, to a lesser extent, in solution as observed by size exclusion chromatography and confirmed by SAXS. Community network analysis based on molecular dynamics simulations shows robust allosteric connections linking the two Raf-RBD D113 residues located in the Galectin scaffold protein binding site of each Raf-RBD molecule and 85 Å apart on opposite ends of the dimer complex. Our results suggest that Raf-RBD binding and Ras dimerization are concerted events that lead to a high-affinity signaling complex at the membrane that we propose is an essential unit in the macromolecular assembly of higher order Ras/Raf/Galectin complexes important for signaling through the Ras/Raf/MEK/ERK pathway.

Weakening of interaction networks with aging in tip-link protein induces hearing loss

Age-related hearing loss (ARHL) is a common condition in humans marking the gradual decrease in hearing with age. Perturbations in the tip-link protein cadherin-23 that absorbs the mechanical tension from sound and maintains the integrity of hearing is associated with ARHL. Here, in search of molecular origins for ARHL, we dissect the conformational behavior of cadherin-23 along with the mutant S47P that progresses the hearing loss drastically. Using an array of experimental and computational approaches, we highlight a lower thermodynamic stability, significant weakening in the hydrogen-bond network and inter-residue correlations among β-strands, due to the S47P mutation. The loss in correlated motions translates to not only a remarkable two orders of magnitude slower folding in the mutant but also to a proportionately complex unfolding mechanism. We thus propose that loss in correlated motions within cadherin-23 with aging may trigger ARHL, a molecular feature that likely holds true for other disease-mutations in β-strand-rich proteins.

Emerging BRAF Mutations in Cancer Progression and Their Possible Effects on Transcriptional Networks

Gene mutations can induce cellular alteration and malignant transformation. Development of many types of cancer is associated with mutations in the B-raf proto-oncogene (BRAF) gene. The encoded protein is a component of the mitogen-activated protein kinases/extracellular signal-regulated kinases (MAPK/ERK) signaling pathway, transmitting information from the outside to the cell nucleus. The main function of the MAPK/ERK pathway is to regulate cell growth, migration, and proliferation. The most common mutations in the BRAF gene encode the V600E mutant (class I), which causes continuous activation and signal transduction, regardless of external stimulus. Consequently, cell proliferation and invasion are enhanced in cancer patients with such mutations. The V600E mutation has been linked to melanoma, colorectal cancer, multiple myeloma, and other types of cancers. Importantly, emerging evidence has recently indicated that new types of mutations (classes II and III) also play a paramount role in the development of cancer. In this minireview, we discuss the influence of various BRAF mutations in cancer, including aberrant transcriptional gene regulation in the affected tissues.

Making NSCLC Crystal Clear: How Kinase Structures Revolutionized Lung Cancer Treatment

The parallel advances of different scientific fields provide a contemporary scenario where collaboration is not a differential, but actually a requirement. In this context, crystallography has had a major contribution on the medical sciences, providing a “face” for targets of diseases that previously were known solely by name or sequence. Worldwide, cancer still leads the number of annual deaths, with 9.6 million associated deaths, with a major contribution from lung cancer and its 1.7 million deaths. Since the relationship between cancer and kinases was unraveled, these proteins have been extensively explored and became associated with drugs that later attained blockbuster status. Crystallographic structures of kinases related to lung cancer and their developed and marketed drugs provided insight on their conformation in the absence or presence of small molecules. Notwithstanding, these structures were also of service once the initially highly successful drugs started to lose their effectiveness in the emergence of mutations. This review focuses on a subclassification of lung cancer, non-small cell lung cancer (NSCLC), and major oncogenic driver mutations in kinases, and how crystallographic structures can be used, not only to provide awareness of the function and inhibition of these mutations, but also how these structures can be used in further computational studies aiming at addressing these novel mutations in the field of personalized medicine.

The Plasma Membrane as a Competitive Inhibitor and Positive Allosteric Modulator of KRas4B Signaling

Mutant Ras proteins are important drivers of human cancers, yet no approved drugs act directly on this difficult target. Over the last decade, the idea has emerged that oncogenic signaling can be diminished by molecules that drive Ras into orientations in which effector-binding interfaces are occluded by the cell membrane. To support this approach to drug discovery, we characterize the orientational preferences of membrane-bound K-Ras4B in 1.45-ms aggregate time of atomistic molecular dynamics simulations. Individual simulations probe active or inactive states of Ras on membranes with or without anionic lipids. We find that the membrane orientation of Ras is relatively insensitive to its bound guanine nucleotide and activation state but depends strongly on interactions with anionic phosphatidylserine lipids. These lipids slow Ras' translational and orientational diffusion and promote a discrete population in which small changes in orientation control Ras' competence to bind multiple regulator and effector proteins. Our results suggest that compound-directed conversion of constitutively active mutant Ras into functionally inactive forms may be accessible via subtle perturbations of Ras' orientational preferences at the membrane surface.

Evolution of a dynamic molecular switch

Eukaryotic protein kinases (EPKs) regulate almost every biological process and have evolved to be dynamic molecular switches; this is in stark contrast to metabolic enzymes, which have evolved to be efficient catalysts. In particular, the highly conserved active site of every EPK is dynamically and transiently assembled by a process that is highly regulated and unique for every protein kinase. We review here the essential features of the kinase core, focusing on the conserved motifs and residues that are embedded in every kinase. We explore, in particular, how the hydrophobic core architecture specifically drives the dynamic assembly of the regulatory spine and consequently the organization of the active site where the γ-phosphate of ATP is positioned by a convergence of conserved motifs including a conserved regulatory triad for transfer to a protein substrate. In conclusion, we show how the flanking N- and C-terminal tails often classified as intrinsically disordered regions, as well as flanking domains, contribute in a highly kinase-specific manner to the regulation of the conserved kinase core. Understanding this process as well as how one kinase activates another remains as two of the big challenges for the kinase signaling community. © 2019 IUBMB Life, 71(6):672-684, 2019.

Acquired JHDM1D-BRAF Fusion Confers Resistance to FGFR Inhibition in FGFR2-Amplified Gastric Cancer

FGFR2 gene is frequently amplified in gastric cancer. Recently, targeting FGFR2 has drawn attention as a form of gastric cancer therapy, and FGFR-selective inhibitors have shown promising efficacy in clinical studies. Because overcoming acquired resistance is a common problem with molecular targeting drugs, we investigated a resistant mechanism of FGFR inhibitors using the gastric cancer cell line SNU-16, which harbors FGFR2 amplification. We established single-cell clones of FGFR inhibitor-resistant SNU-16 (AZD-R) by continuous exposure to AZD4547, a selective FGFR inhibitor. To screen the genetic alterations acquired in AZD-R, we ran a comparative genomic hybridization assay and found an amplification of Chr7q34 region. The chromosomal breakpoints were located between the 12th and the 13th exon of jumonji C domain containing histone demethylase 1 homolog D (JHDM1D) and between the 3rd and the 4th exon of BRAF We sequenced cDNA of the AZD-R clones and found fusion kinase JHDM1D-BRAF, which has previously been identified in primary ovarian cancer. Because JHDM1D-BRAF fusion lacks a RAS-binding domain, the dimerization of JHDM1D-BRAF was enhanced. A cell growth inhibition assay using MEK inhibitors and RAF-dimer inhibitors indicated the dependence of AZD-R clones for growth on the MAPK pathway. Our data provide a clinical rationale for using a MEK or RAF dimer inhibitor to treat FGFR2-amplified gastric cancer patients who have acquired resistance through the JHDN1D-BRAF fusion. Mol Cancer Ther; 17(10); 2217-25. ©2018 AACR.

The Molecular Origin of Enthalpy/Entropy Compensation in Biomolecular Recognition

Biomolecular recognition can be stubborn; changes in the structures of associating molecules, or the environments in which they associate, often yield compensating changes in enthalpies and entropies of binding and no net change in affinities. This phenomenon—termed enthalpy/entropy (H/S) compensation—hinders efforts in biomolecular design, and its incidence—often a surprise to experimentalists—makes interactions between biomolecules difficult to predict. Although characterizing H/S compensation requires experimental care, it is unquestionably a real phenomenon that has, from an engineering perspective, useful physical origins. Studying H/S compensation can help illuminate the still-murky roles of water and dynamics in biomolecular recognition and self-assembly. This review summarizes known sources of H/ S compensation (real and perceived) and lays out a conceptual framework for understanding and dissecting—and, perhaps, avoiding or exploiting—this phenomenon in biophysical systems.

Raf-1 Cysteine-Rich Domain Increases the Affinity of K-Ras/Raf at the Membrane, Promoting MAPK Signaling

K-Ras4B preferentially activates Raf-1. The high-affinity interaction of Ras-binding domain (RBD) of Raf with Ras was solved, but the relative position of Raf's cysteine-rich domain (CRD) in the Ras/Raf complex at the membrane and key question of exactly how it affects Raf signaling are daunting. We show that CRD stably binds anionic membranes inserting a positively charged loop into the amphipathic interface. Importantly, when in complex with Ras/RBD, covalently connected CRD presents the same membrane interaction mechanism, with CRD locating at the space between the RBD and membrane. To date, CRD's role was viewed in terms of stabilizing Raf-membrane interaction. Our observations argue for a key role in reducing Ras/RBD fluctuations at the membrane, thereby increasing Ras/RBD affinity. Even without K-Ras, via CRD, Raf-1 can recruit to the membrane; however, by reducing the Ras/RBD fluctuations and enhancing Ras/RBD affinity at the membrane, CRD promotes Raf's activation and MAPK signaling over other pathways.

Small change, big effect: Taking RAS by the tail through suppression of post-prenylation carboxylmethylation

Mutant RAS isoforms are the most common oncogenes affecting human cancers. After decades of effort in developing drugs targeting oncogenic RAS-driven cancers, we are still charting an unclear path. Despite recent developments exemplified by KRAS (G12C) inhibitors, direct targeting of mutant RAS remains a difficult endeavor. Inhibiting RAS function by targeting its post-translational prenylation processing has remained an important approach, especially with recent progress on the study of isoprenylcysteine carboxylmethyltransferase (ICMT), the unique enzyme for the last step of prenylation processing of RAS isoforms and other substrates. Inhibition of ICMT has shown efficacy both in vitro and in vivo in RAS-mutant cancer models. We will discuss the roles of RAS family of proteins in human cancers and the impact of post-prenylation carboxylmethylation on RAS driven tumorigenesis. In addition, we will review what is known of the molecular and cellular impact of ICMT inhibition on cancer cells that underlie its anti-proliferative and pro-apoptosis efficacy.

Water-Restructuring Mutations Can Reverse the Thermodynamic Signature of Ligand Binding to Human Carbonic Anhydrase

This study uses mutants of human carbonic anhydrase (HCAII) to examine how changes in the organization of water within a binding pocket can alter the thermodynamics of protein-ligand association. Results from calorimetric, crystallographic, and theoretical analyses suggest that most mutations strengthen networks of water-mediated hydrogen bonds and reduce binding affinity by increasing the enthalpic cost and, to a lesser extent, the entropic benefit of rearranging those networks during binding. The organization of water within a binding pocket can thus determine whether the hydrophobic interactions in which it engages are enthalpy-driven or entropy-driven. Our findings highlight a possible asymmetry in protein-ligand association by suggesting that, within the confines of the binding pocket of HCAII, binding events associated with enthalpically favorable rearrangements of water are stronger than those associated with entropically favorable ones.

Drugging Ras GTPase: a comprehensive mechanistic and signaling structural view

Ras proteins are small GTPases, cycling between inactive GDP-bound and active GTP-bound states. Through these switches they regulate signaling that controls cell growth and proliferation. Activating Ras mutations are associated with approximately 30% of human cancers, which are frequently resistant to standard therapies. Over the past few years, structural biology and in silico drug design, coupled with improved screening technology, led to a handful of promising inhibitors, raising the possibility of drugging Ras proteins. At the same time, the invariable emergence of drug resistance argues for the critical importance of additionally honing in on signaling pathways which are likely to be involved. Here we overview current advances in Ras structural knowledge, including the conformational dynamic of full-length Ras in solution and at the membrane, therapeutic inhibition of Ras activity by targeting its active site, allosteric sites, and Ras-effector protein-protein interfaces, Ras dimers, the K-Ras4B/calmodulin/PI3Kα trimer, and targeting Ras with siRNA. To mitigate drug resistance, we propose signaling pathways that can be co-targeted along with Ras and explain why. These include pathways leading to the expression (or activation) of YAP1 and c-Myc. We postulate that these and Ras signaling pathways, MAPK/ERK and PI3K/Akt/mTOR, act independently and in corresponding ways in cell cycle control. The structural data are instrumental in the discovery and development of Ras inhibitors for treating RAS-driven cancers. Together with the signaling blueprints through which drug resistance can evolve, this review provides a comprehensive and innovative master plan for tackling mutant Ras proteins.

Neurofibromatosis type 1: Fundamental insights into cell signalling and cancer

Neurofibromatosis type 1 (NF1) is an autosomal dominant tumour predisposition syndrome that is caused through loss of function mutations of a tumour suppressor gene called Neurofibromin 1. Therapeutic options are currently limited for NF1-associated tumours, where treatment is often restricted to complete surgical resection with clear margins. Herein, we discuss the multifunctional tumour suppressive role of neurofibromin, which is classically known as a GTPase activating protein (GAP) towards the RAS small GTPase. While neurofibromin inhibits proliferative growth through blockade of RAS-mediated signal transduction, neurofibromin should also be considered as a modulator of cell motility and cell adhesion. Through interfacing with the cytoskeleton and membrane structures, neurofibromin acts as a negative regulator of RHO/ROCK signalling pathways involved in cytoskeletal dynamics that are instrumental in proper neuronal development. In the context of cancer, the loss of normal function of neurofibromin via genetic mutation results in heightened cell proliferation and migration, predisposing NF1 patients to cancer. Malignant Peripheral Nerve Sheath Tumours (MPNSTs) can develop from benign neurofibromas and are the main cause of death amongst NF1 patients. Through recent research on MPNSTs, we have gained insight into the key molecular events that drive their malignancy. Advances regarding malignant drivers involved in cell migration, cell invasion and angiogenic signalling are discussed in this review, where these findings will likely influence future therapies for both NF1 and related sporadic cancers.