RAS-targeted therapies: is the undruggable drugged?

Isomer-sourced structure iteration methods for in silico development of inhibitors: Inducing GTP-bound NRAS-Q61 oncogenic mutations to an "off-like" state

The NRAS-mutant subset of melanoma represent some of the most aggressive and deadliest types associated with poor overall survival. Unfortunately, for more than 40 years, no therapeutic agent directly targeting NRAS mutations has been clinically approved. In this work, based on microsecond scale molecular dynamics simulations, the effect of Q61 mutations on NRAS conformational characteristics is revealed at the atomic level. The GTP-bound NRAS-Q61R and Q61K mutations show a specific targetable pocket between Switch-II and α-helix 3 whereas the NRAS-Q61L non-polar mutation category shows a different targetable pocket. Moreover, a new isomer-sourced structure iteration method has been developed for the in silico design of potential inhibitor prototypes for oncogenes. We show the possibility of a designed prototype HM-387 to target activated NRAS-Q61R and that it can gradually induce the transition from the activated NRAS-Q61R to an "off-like" state.

LSP1 promotes the progression of acute myelogenous leukemia by regulating KSR/ERK signaling pathway and cell migration

We aimed to investigate the role and mechanism of LSP1 in the progression of acute myelogenous leukemia. In this study, we established shLSP1 cell line to analyze the function of LSP1 in AML. We observed high expression of LSP1 in AML patients, whereas it showed no expression in normal adults. Furthermore, we found that LSP1 expression was associated with disease prognosis. Our results indicate that LSP1 plays a crucial role in mediating proliferation and survival of leukemia cells through the KSR/ERK signaling pathway. Additionally, LSP1 promotes cell chemotaxis and homing by enhancing cell adhesion and migration. We also discovered that LSP1 confers chemotactic ability to leukemia cells in vivo. Finally, our study identified 12 genes related to LSP1 in AML, which indicated poor survival outcome in AML patients and were enriched in Ras and cell adhesion signaling pathways. Our results revealed that the overexpression of LSP1 is related to the activation of the KSR/ERK signaling pathway, as well as cell adhesion and migration in AML patients. Reducing LSP1 expression impair AML progression, suggesting that LSP1 may serve as a potential drug therapy target for more effective treatment of AML.

Mechanisms of Resistance to Oncogenic KRAS Inhibition in Pancreatic Cancer

KRAS inhibitors demonstrate clinical efficacy in pancreatic ductal adenocarcinoma (PDAC); however, resistance is common. Among patients with KRASG12C-mutant PDAC treated with adagrasib or sotorasib, mutations in PIK3CA and KRAS, and amplifications of KRASG12C, MYC, MET, EGFR, and CDK6 emerged at acquired resistance. In PDAC cell lines and organoid models treated with the KRASG12D inhibitor MRTX1133, epithelial-to-mesenchymal transition and PI3K-AKT-mTOR signaling associate with resistance to therapy. MRTX1133 treatment of the KrasLSL-G12D/+; Trp53LSL-R172H/+; p48-Cre (KPC) mouse model yielded deep tumor regressions, but drug resistance ultimately emerged, accompanied by amplifications of Kras, Yap1, Myc, Cdk6, and Abcb1a/b, and co-evolution of drug-resistant transcriptional programs. Moreover, in KPC and PDX models, mesenchymal and basal-like cell states displayed increased response to KRAS inhibition compared to the classical state. Combination treatment with KRASG12D inhibition and chemotherapy significantly improved tumor control in PDAC mouse models. Collectively, these data elucidate co-evolving resistance mechanisms to KRAS inhibition and support multiple combination therapy strategies. Significance: Acquired resistance may limit the impact of KRAS inhibition in patients with PDAC. Using clinical samples and multiple preclinical models, we define heterogeneous genetic and non-genetic mechanisms of resistance to KRAS inhibition that may guide combination therapy approaches to improve the efficacy and durability of these promising therapies for patients. See related commentary by Marasco and Misale, p. 2018.

Treatment of a mutant KRAS lung cancer cell line with polyisoprenylated cysteinyl amide inhibitors activates the MAPK pathway, inhibits cell migration and induces apoptosis

KRAS mutations are the most common oncogenic mutations in lung adenocarcinoma in Black Americans. Polyisoprenylated Cysteinyl amide Inhibitors (PCAIs) constitute a group of potential cancer therapy agents that we designed to specifically disrupt and suppress hyperactive G-protein signaling, such as that caused by mutated RAS proteins. Here we determine the effects of PCAIs on the viability, G-protein levels, downstream mediators, and apoptosis-related proteins on the KRAS-mutated, Black American-derived lung adenocarcinoma cell line, NCI-H23. Of the 17 PCAIs tested, compounds NSL-YHJ-2-27 and NSL-YHJ-2-46 showed the most potency with EC50 values of 2.7 and 3.3 μM, respectively. Western blotting was used to determine the effect of the PCAIs on the phosphorylation levels of MAPK pathway enzymes. After 48 h exposure to 5 μM of the PCAIs, NSL-YHJ-2-46, the MAPK proteins BRAF, MEK1/2, ERK1/2, and p90RSK were activated through phosphorylation by 90, 190, 150 and 120%, respectively. However, CRAF/RAF1 phosphorylation decreased by 40%, suggesting significant changes in the KRAS/MAPK signaling patterns. Furthermore, 5 μM of NSL-YHJ-2-27 depleted the singly polyisoprenylated monomeric G-proteins RAC 1/2/3 and CDC42 by 77 and 76%, respectively. The depletion of these key cytoskeletal proteins may account for the observed inhibition of cell migration and invasion, and spheroid invasion observed on exposure to NSL-YHJ-2-27 and NSL-YHJ-2-46. Treatment with 5 μM of NSL-YHJ-2-27 suppressed full-length inactive caspase 3 and 7 levels by 72 and 91%, respectively. An analysis of cells treated with the fluorescently labeled active caspase 3/7 irreversible inhibitor, CaspaTagTM Caspase-3/7 in situ reagent revealed a 124% increase in active caspase at 3 μM over controls. These findings clearly show the direct effects of the PCAIs on the RAS signaling pathway. Given the profound increases observed in RPS6KA1/p90RSK phosphorylation, future work will involve a determination whether the proapoptotic isoforms of RPS6KA1/p90RSK are phosphorylated due to the PCAIs treatments. These results support the potential use of the PCAIs as targeted therapies against cancers with KRAS mutations.

Recent breakthroughs in innovative elements, multidimensional enhancements, derived technologies, and novel applications of PROTACs

Proteolysis Targeting Chimera (PROTAC) is an emerging and evolving technology based on targeted protein degradation (TPD). Small molecule PROTACs have shown great efficacy in degrading disease-specific proteins in preclinical and clinical studies, but also showed various limitations. In recent years, new technologies and advances in TPD have provided additional optimized strategies based on conventional PROTACs that can overcome the shortcomings of conventional PROTACs in terms of undruggable targets, bioavailability, tissue-specificity, spatiotemporal control, and degradation scope. In addition, some designs of special targeting chimeras and applications based on multidisciplinary science have shed light on novel therapeutic modalities and drug design. However, each improvement has its own advantages, disadvantages and application conditions. In this review, we summarize the exploration of PROTAC elements, depict a landscape of improvements and derived concepts of PROTACs, and expect to provide perspectives for technological innovations, combinations and applications in future targeting chimera design.

Beyond KRAS(G12C): Biochemical and Computational Characterization of Sotorasib and Adagrasib Binding Specificity and the Critical Role of H95 and Y96

Mutated KRAS proteins are frequently expressed in some of the most lethal human cancers and thus have been a target of intensive drug discovery efforts for decades. Lately, KRAS(G12C) switch-II pocket (SII-P)-targeting covalent small molecule inhibitors have finally reached clinical practice. Sotorasib (AMG-510) was the first FDA-approved covalent inhibitor to treat KRAS(G12C)-positive nonsmall cell lung cancer (NSCLC), followed soon by adagrasib (MRTX849). Both drugs target the GDP-bound state of KRAS(G12C), exploiting the strong nucleophilicity of acquired cysteine. Here, we evaluate the similarities and differences between sotorasib and adagrasib in their RAS SII-P binding by applying biochemical, cellular, and computational methods. Exact knowledge of SII-P engagement can enable targeting this site by reversible inhibitors for KRAS mutants beyond G12C. We show that adagrasib is strictly KRAS- but not KRAS(G12C)-specific due to its strong and unreplaceable interaction with H95. Unlike adagrasib, sotorasib is less dependent on H95 for its binding, making it a RAS isoform-agnostic compound, having a similar functionality also with NRAS and HRAS G12C mutants. Our results emphasize the accessibility of SII-P beyond oncogenic G12C and aid in understanding the molecular mechanism behind the clinically observed drug resistance, associated especially with secondary mutations on KRAS H95 and Y96.

Semaphorin 3D promotes pancreatic ductal adenocarcinoma progression and metastasis through macrophage reprogramming

Axon guidance molecules are frequently altered in pancreatic ductal adenocarcinoma (PDA) and influence PDA progression. However, the molecular mechanism remained unclear. Using genetically engineered mouse models to examine semaphorin 3D (SEMA3D), we identified a dual role for tumor- and nerve-derived SEMA3D in the malignant transformation of pancreatic epithelial cells and invasive PDA development. Pancreatic-specific knockout of the SEMA3D gene from the KRASG12D and TP53R172H mutation knock-in, PDX1-Cre(KPC) mouse model demonstrated delayed tumor initiation, prolonged survival, absence of metastasis, and reduced M2 macrophage expression. Mechanistically, tumor- and nerve-derived SEMA3D indirectly reprograms macrophages through KRASMUT-dependent ARF6 signaling in PDA cells, resulting in increased lactate production, which is sensed by GPCR132 on macrophages to stimulate protumorigenic M2 polarization. Multiplex immunohistochemistry demonstrated increased M2-polarized macrophages proximal to nerves in SEMA3D-expressing human PDA tissue. This study suggests that altered SEMA3D expression leads to an acquisition of cancer-promoting functions, and nerve-derived SEMA3D is "hijacked" by PDA cells to support growth and metastasis in a KRASMUT-dependent manner.

Going Rogue: Mechanisms, Regulation, and Roles of Mutationally Activated Gα in Human Cancer

G protein-coupled receptors (GPCRs) couple to heterotrimeric G proteins, comprised of α and βγ subunits, to convert extracellular signals into activation of intracellular signaling pathways. Canonically, GPCR-mediated activation results in the exchange of GDP for GTP on G protein α subunits (Gα) and the dissociation of Gα-GTP and G protein βγ subunits (Gβγ), both of which can regulate a variety of signaling pathways. Hydrolysis of bound GTP by Gα returns the protein to Gα-GDP and allows reassociation with Gβγ to reform the inactive heterotrimer. Naturally occurring mutations in Gα have been found at conserved glutamine and arginine amino acids that disrupt the canonical G protein cycle by inhibiting GTP hydrolysis, rendering these mutants constitutively active. Interestingly, these dysregulated Gα mutants are found in many different cancers due to their ability to sustain aberrant signaling without a need for activation by GPCRs. This review will highlight an increased recognition of the prevalence of such constitutively activating Gα mutations in cancers and the signaling pathways activated. In addition, we will discuss new knowledge regarding how these constitutively active Gα are regulated, how different mutations are biochemically distinct, and how mutationally activated Gα are unique compared with GPCR-activated Gα Lastly, we will discuss recent progress in developing inhibitors directly targeting constitutively active Gα mutants. SIGNIFICANCE STATEMENT: Constitutively activating mutations in G protein α subunits (Gα) widely occur in and contribute to the development of many human cancers. To develop ways to inhibit dysregulated, oncogenic signaling by these mutant Gα, it is crucial to better understand mechanisms that lead to constitutive Gα activation and unique mechanisms that regulate mutationally activated Gα in cells. The prevalence of activating mutations in Gα in various cancers makes Gα proteins compelling targets for the development of therapeutics.

TRIM21 induces selective autophagic degradation of c-Myc and sensitizes regorafenib therapy in colorectal cancer

Kirsten rat sarcoma virus (KRAS) mutation is associated with malignant tumor transformation and drug resistance. However, the development of clinically effective targeted therapies for KRAS-mutant cancer has proven to be a formidable challenge. Here, we report that tripartite motif-containing protein 21 (TRIM21) functions as a target of extracellular signal-regulated kinase 2 (ERK2) in KRAS-mutant colorectal cancer (CRC), contributing to regorafenib therapy resistance. Mechanistically, TRIM21 directly interacts with and ubiquitinates v-myc avian myelocytomatosis viral oncogene homolog (c-Myc) at lysine 148 (K148) via K63-linkage, enabling c-Myc to be targeted to the autophagy machinery for degradation, ultimately resulting in the downregulation of enolase 2 expression and inhibition of glycolysis. However, mutant KRAS (KRAS/MT)-driven mitogen-activated protein kinase (MAPK) signaling leads to the phosphorylation of TRIM21 (p-TRIM21) at Threonine 396 (T396) by ERK2, disrupting the interaction between TRIM21 and c-Myc and thereby preventing c-Myc from targeting autophagy for degradation. This enhances glycolysis and contributes to regorafenib resistance. Clinically, high p-TRIM21 (T396) is associated with an unfavorable prognosis. Targeting TRIM21 to disrupt KRAS/MT-driven phosphorylation using the antidepressant vilazodone shows potential for enhancing the efficacy of regorafenib in treating KRAS-mutant CRC in preclinical models. These findings are instrumental for KRAS-mutant CRC treatment aiming at activating TRIM21-mediated selective autophagic degradation of c-Myc.

KRAS, a New Target for Precision Medicine in Colorectal Cancer?

Colorectal cancer (CRC) remains a leading cause of cancer-related mortality globally, with significant public health concerns. This review examines the landscape of KRAS inhibition in colorectal cancer (CRC), focusing on recent advances in therapeutic strategies targeting this oncogene. Historically deemed undruggable due to its complex structure and essential role in tumorigenesis, KRAS mutations are prevalent in CRC and are associated with poor prognosis. However, breakthroughs in drug development have led to the emergence of KRAS inhibitors as promising treatment options. This review discusses various classes of KRAS inhibitors, including covalent and non-covalent inhibitors, as well as combination therapies aimed at enhancing efficacy and overcoming resistance mechanisms. It highlights recent clinical trials evaluating the efficacy of KRAS inhibitors either as monotherapy or in combination with other agents, such as anti-EGFR antibodies. Despite challenges such as resistance mechanisms and tumor heterogeneity, the development of KRAS inhibitors represents a significant advance in CRC treatment and holds promise for improving patient outcomes in the future.

Inhibition and degradation of NRAS with a pan-NRAS monobody

The RAS family GTPases are the most frequently mutated oncogene family in human cancers. Activating mutations in either of the three RAS isoforms (HRAS, KRAS, or NRAS) are found in nearly 20% of all human tumors with NRAS mutated in ~25% of melanomas. Despite remarkable advancements in therapies targeted against mutant KRAS, NRAS-specific pharmacologics are lacking. Thus, development of inhibitors of NRAS would address a critical unmet need to treating primary tumors harboring NRAS mutations as well as BRAF-mutant melanomas, which frequently develop resistance to clinically approved BRAF inhibitors through NRAS mutation. Building upon our previous studies with the monobody NS1 that recognizes HRAS and KRAS but not NRAS, here we report the development of a monobody that specifically binds to both GDP and GTP-bound states of NRAS and inhibits NRAS-mediated signaling in a mutation-agnostic manner. Further, this monobody can be formatted into a genetically encoded NRAS-specific degrader. Our study highlights the feasibility of developing NRAS selective inhibitors for therapeutic efforts.

Sustained Response to Anti-PD-1 Therapy in Combination with Nab-Paclitaxel in Metastatic Testicular Germ Cell Tumor Harboring the KRAS-G12V Mutation: A Case Report

INTRODUCTION

Cisplatin-based standardized therapy has been established for metastatic testicular germ cell tumors (TGCTs). However, the patient prognosis is considerably less favorable if the disease recurs following failure of first-line therapies. There is a need for novel treatment options for patients with recurrent or metastatic TGCTs, notably for those that are not sensitive to first-line chemotherapy. With the development of next-generation sequencing technologies, an increasing number of gene mutations has been identified in TGCTs. Previously published research studies have established a link between KRAS mutations and chemotherapy resistance, and have demonstrated that KRAS mutations are associated with inflammatory tumor microenvironment and tumor immunogenicity, leading to an improved response to inhibition of programmed death (PD-1) protein expression. Previous studies have reported that the tumor immune microenvironment of TGCT influences therapeutic efficacy.

CASE PRESENTATION

A 65-year-old metastatic patient with TGCT and a KRAS-12 valine-for-glycine gene mutation was described. This patient initially underwent inguinal orchiectomy and received two prior chemotherapeutic regimens. Following the rapid progression of the disease, the patient was treated with anti-PD-1 therapy and nab-paclitaxel chemotherapy, and his condition was successfully controlled by this combination treatment.

CONCLUSION

To the best of our knowledge, this is the first successful case of KRAS-mutation patient with TGCT who achieved partially and sustained disease remission by combining immune checkpoint inhibitors with chemotherapy. This case provides an excellent example for personalized treatment of metastatic TGCTs.

Recent advances in the design of small molecular drugs with acrylamides covalent warheads

In the development of covalent inhibitors, acrylamides warhead is one of the most popular classes of covalent warheads. In recent years, researchers have made different structural modifications to acrylamides warheads, resulting in the creation of fluorinated acrylamide warheads and cyano acrylamide warheads. These new warheads exhibit superior selectivity, intracellular accumulation, and pharmacokinetic properties. Additionally, although ketoamide warheads have been applied in the design of covalent inhibitors for viral proteins, it has not received sufficient attention. Combined with the studies in kinase inhibitors and antiviral drugs, this review presents the structural features and the progression of acrylamides warheads, offering a perspective on future research and development in this field.

Targeting KRAS Oncogene for Patients With Colorectal Cancer: A New Step Toward Precision Medicine

KRAS mutations are common driver oncogenes associated with the development of several solid tumors. KRAS oncogene has been considered a highly challenging target for drug development because of structural features, including the lack of deep groove on its catalytic unit. However, by leveraging cysteine residues, covalent KRAS inhibitors irreversibly trap KRAS G12C mutants in their inactive GDP-bound state. These agents have resulted in significant clinical responses among patients with KRAS G12C-mutant solid tumors, including patients with colorectal cancer (CRC). Other allele-specific inhibitors of KRAS oncogene and panKRAS and panRAS inhibitors are also currently being investigated in clinical trials. This review article overviews recent clinical progress on KRAS G12C targeting for the management of patients with KRAS G12C-mutant CRC and provides an update on other RAS targeting approaches. We also discuss the unique biological features of RAS-mutant CRC, which require the combination of KRAS inhibitors and anti-epidermal growth factor receptor therapy, and elaborate on resistance mechanisms and novel therapeutic avenues that may define future treatment paradigms of patients with RAS-mutant CRC.

BOC targets SMO to regulate the Hedgehog pathway and promote proliferation, migration, and invasion of glioma cells

The purpose of this study was to investigate the effects of BOC on glioblastoma cells and its underlying mechanisms. In vitro, BOC-knockdown was performed in glioma cell lines. CCK-8 and Transwell were used to assess the impact of BOC on the viability, invasion, and migration of gliobma cells. RNA-seq technology was employed to analyze the differential gene expression between BOC-knockdown glioma cells and the control group, and qRT-PCR was used to validate the expression of downstream differential genes. SMO-overexpression was performed to investigate the effects of SMO on glioma cells. A BOC-knockdown mouse subcutaneous tumor model was to verify the effects of BOC on mouse tumors. Tissue microarray technology was used to detect the expression of BOC and SMO in samples of normal human brain tissue and glioma tissue. In vitro, BOC-knockdown inhibited the viability, invasion, and migration of glioma cells, as well as downregulated the expression of downstream differential genes SMO, EGFR, HRAS, and MRAS. Conversely, SMO-overexpression upregulated the viability, invasion, and migration abilities of BOC-knockdown cells. In vivo, BOC-knockdown suppressed tumor growth in mice and downregulated the expression of downstream differential genes SMO, EGFR, HRAS, and MRAS. Tissue microarray results showed that both BOC and SMO were highly expressed in glioma tissues. BOC is aberrantly overexpressed in glioma patients and promotes glioma development. Mechanistically, BOC activates the Hedgehog (Hh) and RAS signaling pathways by upregulating the expression of SMO, EGFR, HRAS, and MRAS, thereby facilitating the Proliferation, invasion and migration of glioma cells.

Positive feedback in Ras activation by full-length SOS arises from autoinhibition release mechanism

Signaling through the Ras-MAPK pathway can exhibit switch-like activation, which has been attributed to the underlying positive feedback and bimodality in the activation of RasGDP to RasGTP by SOS. SOS contains both catalytic and allosteric Ras binding sites, and a common assumption is that allosteric activation selectively by RasGTP provides the mechanism of positive feedback. However, recent single-molecule studies have revealed that SOS catalytic rates are independent of the nucleotide state of Ras in the allosteric binding site, raising doubt about this as a positive feedback mechanism. Here, we perform detailed kinetic analyses of receptor-mediated recruitment of full-length SOS to the membrane while simultaneously monitoring its catalytic activation of Ras. These results, along with kinetic modeling, expose the autoinhibition release step in SOS, rather than either recruitment or allosteric activation, as the underlying mechanism giving rise to positive feedback in Ras activation.

The molecular mechanism underlying KRAS regulation on STK31 expression in pancreatic ductal adenocarcinoma

KRAS gene mutations are common in pancreatic ductal adenocarcinoma (PDAC), but targeting mutant KRAS is still challenging. Here, an endoribonuclease-prepared small interfering RNA (esiRNA) library was used to screen new kinases that play critical roles in PDAC driven by KRAS gene mutations, and serine/threonine kinase 31 (STK31) was identified and characterized as a potential therapeutic target for KRAS-mutant PDAC. Our results showed that STK31 was upregulated in KRAS-mutant PDAC patients with poor survival and highly expressed in PDAC cell lines with KRASG12D mutation. Inhibition of STK31 in KRAS-mutant cell lines significantly reduced PDAC cell growth in vitro and hindered tumor growth in vivo. Gain and loss of function experiments revealed that STK31 is a downstream target of KRAS in PDAC. A pharmacological inhibition assay showed MAPK/ERK signaling involved in STK31 regulation. The further mechanistic study validated that c-Jun, regulated by KRAS/MAPK signaling, directly modulates the transcription level of STK31 by binding to its promoter region. Through RNA sequencing, we found that the cell cycle regulators CCNB1 and CDC25C are downstream targets of STK31. Taken together, our results indicate that STK31, which is the downstream target of the KRAS/MAPK/ERK/c-Jun signaling pathway in KRAS-mutant PDAC, promotes PDAC cell growth by modulating the expression of the cell cycle regulators CCNB1 and CDC25C.

The SOS1 Inhibitor MRTX0902 Blocks KRAS Activation and Demonstrates Antitumor Activity in Cancers Dependent on KRAS Nucleotide Loading

KRAS is the most frequently mutated oncogene in human cancer and facilitates uncontrolled growth through hyperactivation of the receptor tyrosine kinase (RTK)/mitogen-activated protein kinase (MAPK) pathway. The Son of Sevenless homolog 1 (SOS1) protein functions as a guanine nucleotide exchange factor (GEF) for the RAS subfamily of small GTPases and represents a druggable target in the pathway. Using a structure-based drug discovery approach, MRTX0902 was identified as a selective and potent SOS1 inhibitor that disrupts the KRAS:SOS1 protein-protein interaction to prevent SOS1-mediated nucleotide exchange on KRAS and translates into an anti-proliferative effect in cancer cell lines with genetic alterations of the KRAS-MAPK pathway. MRTX0902 augmented the antitumor activity of the KRAS G12C inhibitor adagrasib when dosed in combination in eight out of 12 KRAS G12C-mutant human non-small cell lung cancer and colorectal cancer xenograft models. Pharmacogenomic profiling in preclinical models identified cell cycle genes and the SOS2 homolog as genetic co-dependencies and implicated tumor suppressor genes (NF1 and PTEN) in resistance following combination treatment. Lastly, combined vertical inhibition of RTK/MAPK pathway signaling by MRTX0902 with inhibitors of EGFR or RAF/MEK led to greater downregulation of pathway signaling and improved antitumor responses in KRAS-MAPK pathway-mutant models. These studies demonstrate the potential clinical application of dual inhibition of SOS1 and KRAS G12C and additional SOS1 combination strategies that will aide in the understanding of SOS1 and RTK/MAPK biology in targeted cancer therapy.

Study of the mass balance, biotransformation, and safety of [ 14C]IBI351 in healthy Chinese subjects

IBI351, a synthetic compound, exerts its anti-tumor effects by specifically, covalently, and irreversibly modifying the 12th cysteine residue of KRAS G12C. However, the pharmacokinetic characteristics of IBI351 in the human body have not been reported. The current study aimed to investigate the pharmacokinetics and safety of IBI351 in healthy Chinese male subjects. A single oral dose of 600 mg/150 μCi [ 14C]IBI351 was administered to six healthy male subjects. Blood, urine, and fecal samples were collected at continuous time points to analyze the levels of IBI351 parent drug and its metabolites. We found that IBI351 showed favorable pharmacokinetic characteristics, and was well tolerated in all the six participants. In addition, 17 major metabolites of IBI351 were analyzed and identified in the blood, urine, and feces. The main metabolic pathways included oxidation, hydrogenation, sulfonate conjugation, glucuronide conjugation, and cysteine conjugation. IBI351 and its metabolites were primarily excreted through feces. Taken together, this is the first study on the metabolism and safety of IBI351 in Chinese subjects, and these findings may guide future clinical development of IBI351 as a novel anti-tumor drug.

Mediating kinase activity in Ras-mutant cancer: potential for an individualised approach?

It is widely acknowledged that there is a considerable number of oncogenic mutations within the Ras superfamily of small GTPases which are the driving force behind a multitude of cancers. Ras proteins mediate a plethora of kinase pathways, including the MAPK, PI3K, and Ral pathways. Since Ras was considered undruggable until recently, pharmacological targeting of pathways downstream of Ras has been attempted to varying success, though drug resistance has often proven an issue. Nuances between kinase pathway activation in the presence of various Ras mutants are thought to contribute to the resistance, however, the reasoning behind activation of different pathways in different Ras mutational contexts is yet to be fully elucidated. Indeed, such disparities often depend on cancer type and disease progression. However, we are in a revolutionary age of Ras mutant targeted therapy, with direct-targeting KRAS-G12C inhibitors revolutionising the field and achieving FDA-approval in recent years. However, these are only beneficial in a subset of patients. Approximately 90% of Ras-mutant cancers are not KRAS-G12C mutant, and therefore raises the question as to whether other distinct amino acid substitutions within Ras may one day be targetable in a similar manner, and indeed whether better understanding of the downstream pathways these various mutants activate could further improve therapy. Here, we discuss the favouring of kinase pathways across an array of Ras-mutant oncogenic contexts and assess recent advances in pharmacological targeting of various Ras mutants. Ultimately, we will examine the utility of individualised pharmacological approaches to Ras-mediated cancer.

Identification and Characterization of Novel Small-Molecule Enhancers of the CUL3LZTR1 E3 Ligase KRAS Complex

The RAS family of GTPases is among the most frequently mutated proteins in human cancer, creating a high clinical demand for therapies that counteract their signaling activity. An important layer of regulation that could be therapeutically exploited is the proteostatic regulation of the main RAS GTPases KRAS, NRAS, and HRAS, as well as the closely related members, MRAS and RIT1, by the leucine zipper-like transcriptional regulator 1 cullin 3 RING E3 ubiquitin ligase complex (CUL3LZTR1). Genetic inactivation of LZTR1, as observed in different cancer entities and Noonan syndrome leads to enhanced RAS GTPase abundance and altered MAPK pathway activation state. Novel therapeutic approaches to interfere with hyperactive RAS signaling, thereby complementing existing treatments, are highly sought after. Motivated by the growing arsenal of molecular glue degraders, we report the identification of novel chemical fragments that enhance the protein-protein interaction (PPI) of the KRAS-LZTR1 complex. We established a split-luciferase-based reporter assay that monitors the RAS GTPase-LZTR1 interaction in a scalable format, capable of capturing chemical, as well as mutational perturbations. Using this screening system, in combination with a small fragment library, we identified two fragments, C53 and Z86, that enhance the interaction of the KRAS-LZTR1 complex in a dose-dependent manner. Further orthogonal validation experiments using proximity biotinylation (BioID), thermal shift assays, and NMR spectroscopy demonstrated fragment-dependent enhanced recruitment of endogenous LZTR1 and physical engagement of KRAS. The two fragments, which potentiate the KRAS-LZTR1 interaction, serve as starting points for fragment-based drug discovery. Additionally, the assay we introduced is amenable to high-throughput screening to further explore the pharmacological modulation of the CUL3LZTR1-RAS GTPase complex.

Targeting the RAS upstream and downstream signaling pathway for cancer treatment

Cancer often involves the overactivation of RAS/RAF/MEK/ERK (MAPK) and PI3K-Akt-mTOR pathways due to mutations in genes like RAS, RAF, PTEN, and PIK3CA. Various strategies are employed to address the overactivation of these pathways, among which targeted therapy emerges as a promising approach. Directly targeting specific proteins, leads to encouraging results in cancer treatment. For instance, RTK inhibitors such as imatinib and afatinib selectively target these receptors, hindering ligand binding and reducing signaling initiation. These inhibitors have shown potent efficacy against Non-Small Cell Lung Cancer. Other inhibitors, like lonafarnib targeting Farnesyltransferase and GGTI 2418 targeting geranylgeranyl Transferase, disrupt post-translational modifications of proteins. Additionally, inhibition of proteins like SOS, SH2 domain, and Ras demonstrate promising anti-tumor activity both in vivo and in vitro. Targeting downstream components with RAF inhibitors such as vemurafenib, dabrafenib, and sorafenib, along with MEK inhibitors like trametinib and binimetinib, has shown promising outcomes in treating cancers with BRAF-V600E mutations, including myeloma, colorectal, and thyroid cancers. Furthermore, inhibitors of PI3K (e.g., apitolisib, copanlisib), AKT (e.g., ipatasertib, perifosine), and mTOR (e.g., sirolimus, temsirolimus) exhibit promising efficacy against various cancers such as Invasive Breast Cancer, Lymphoma, Neoplasms, and Hematological malignancies. This review offers an overview of small molecule inhibitors targeting specific proteins within the RAS upstream and downstream signaling pathways in cancer.

Synergistic anti-tumor activity, reduced pERK, and immuno-stimulatory cytokine profiles with 5-FU or ONC212 plus KRAS G12D inhibitor MRTX1133 in CRC and pancreatic cancer cells independent of G12D mutation

KRAS mutations occur in ~40-50% of mCRC and are associated with aggressive disease that is refractory to anti-EGFR therapies. Pancreatic cancer harbors ~90% KRAS driver gene mutation frequency. Small molecules targeting KRAS G12C gained FDA approval for KRAS G12C-mutated NSCLC. ONC212, a fluorinated imipridone with nM anti-cancer activity has preclinical efficacy against pancreatic cancer and other malignancies. MRTX1133, identified as a noncovalent selective KRAS G12D inhibitor that suppresses G12D signaling by binding to the switch II pocket thereby inhibiting protein-protein interactions. We investigated cell viability, drug synergies, pERK suppression and cytokine, chemokine or growth factor alterations following treatment with 5-Fluorouracil (5-FU) or ONC212 plus MRTX1133 in 6 human CRC and 4 human pancreatic cancer cell lines. IC50 sensitivities ranged from 7 to 12 µM for 5-FU, 0.2-0.8 µM for ONC212, and > 100 nM to > 5,000 nM for MRTX1133 (G12D N = 4: LS513 > 100, HPAF-II > 1,000, SNUC2B > 5,000, PANC-1 > 5,000). For non-G12D, the range of IC50 for MRTX1133 was > 1,000 to > 5,000 nM for CRC lines with G12V, G13D, or WT KRAS (N = 7). Synergies between MRTX1133 plus 5-FU or ONC212 were observed regardless of KRAS G12D mutation with combination indices of < 0.5 indicating strong synergy. Observed synergies were greater with MRTX1133 plus ONC212 compared to MRTX1133 plus 5-FU. pERK was suppressed with mutant but not wild-type KRAS at nM MRTX1133 doses. Immunostimulatory profiles included reduction in IL8/CXCL8, MICA, Angiopoietin 2, VEGF and TNF-alpha and increase in IL-18/IL-1F4 with MRTX treatments and combinations. Our studies reveal preclinical activity of MRTX1133 alone or synergies when combined with 5-FU or ONC212 against mCRC and pancreatic cancer cells regardless of KRAS G12D mutation. The results suggest that KRAS G12V and KRAS G13D should be further considered in clinical trials including combination therapies involving MRTX1133 and 5-FU or ONC212.

Towards Targeting Endothelial Rap1B to Overcome Vascular Immunosuppression in Cancer

The vascular endothelium, a specialized monolayer of endothelial cells (ECs), is crucial for maintaining vascular homeostasis by controlling the passage of substances and cells. In the tumor microenvironment, Vascular Endothelial Growth Factor A (VEGF-A) drives tumor angiogenesis, leading to endothelial anergy and vascular immunosuppression-a state where ECs resist cytotoxic CD8+ T cell infiltration, hindering immune surveillance. Immunotherapies have shown clinical promise. However, their effectiveness is significantly reduced by tumor EC anergy. Anti-angiogenic treatments aim to normalize tumor vessels and improve immune cell infiltration. Despite their potential, these therapies often cause significant systemic toxicities, necessitating new treatments. The small GTPase Rap1B emerges as a critical regulator of Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) signaling in ECs. Our studies using EC-specific Rap1B knockout mice show that the absence of Rap1B impairs tumor growth, alters vessel morphology, and increases CD8+ T cell infiltration and activation. This indicates that Rap1B mediates VEGF-A's immunosuppressive effects, making it a promising target for overcoming vascular immunosuppression in cancer. Rap1B shares structural and functional similarities with RAS oncogenes. We propose that targeting Rap1B could enhance therapies' efficacy while minimizing adverse effects by reversing endothelial anergy. We briefly discuss strategies successfully developed for targeting RAS as a model for developing anti-Rap1 therapies.

Molecular characterization of gliomas and glioneuronal tumors amid Noonan syndrome: cancer predisposition examined

Introduction

In the setting of pediatric and adolescent young adult cancer, increased access to genomic profiling has enhanced the detection of genetic variation associated with cancer predisposition, including germline syndromic conditions. Noonan syndrome (NS) is associated with the germline RAS pathway activating alterations and increased risk of cancer. Herein, we describe our comprehensive molecular profiling approach, the association of NS with glioma and glioneuronal tumors, and the clinical and histopathologic characteristics associated with the disease.

Methods

Within an institutional pediatric cancer cohort (n = 314), molecular profiling comprised of paired somatic disease-germline comparator exome analysis, RNA sequencing, and tumor classification by DNA methylation analysis was performed.

Results

Through the implementation of paired analysis, this study identified 4 of 314 (1.3%) individuals who harbored a germline PTPN11 variant associated with NS, of which 3 individuals were diagnosed with a glioma or glioneuronal tumor. Furthermore, we extend this study through collaboration with a peer institution to identify two additional individuals with NS and a glioma or glioneuronal tumor. Notably, in three of five (60%) individuals, paired genomic profiling led to a previously unrecognized diagnosis of Noonan syndrome despite an average age of cancer diagnosis of 16.8 years. The study of the disease-involved tissue identified signaling pathway dysregulation through somatic alteration of genes involved in cellular proliferation, survival, and differentiation.

Discussion

Comparative pathologic findings are presented to enable an in-depth examination of disease characteristics. This comprehensive analysis highlights the association of gliomas and glioneuronal tumors with RASopathies and the potential therapeutic challenges and importantly demonstrates the utility of genomic profiling for the identification of germline cancer predisposition.

Photonanozyme-Kras-ribosome combination treatment of non-small cell lung cancer after COVID-19

With the outbreak of the coronavirus disease 2019 (COVID-19), reductions in T-cell function and exhaustion have been observed in patients post-infection of COVID-19. T cells are key mediators of anti-infection and antitumor, and their exhaustion increases the risk of compromised immune function and elevated susceptibility to cancer. Non-small cell lung cancer (NSCLC) is the most common subtype of lung cancer with high incidence and mortality. Although the survival rate after standard treatment such as surgical treatment and chemotherapy has improved, the therapeutic effect is still limited due to drug resistance, side effects, and recurrence. Recent advances in molecular biology and immunology enable the development of highly targeted therapy and immunotherapy for cancer, which has driven cancer therapies into individualized treatments and gradually entered clinicians' views for treating NSCLC. Currently, with the development of photosensitizer materials, phototherapy has been gradually applied to the treatment of NSCLC. This review provides an overview of recent advancements and limitations in different treatment strategies for NSCLC under the background of COVID-19. We discuss the latest advances in phototherapy as a promising treatment method for NSCLC. After critically examining the successes, challenges, and prospects associated with these treatment modalities, their profound prospects were portrayed.

Potent antitumor activity of a bispecific T-cell engager antibody targeting the intracellular antigen KRAS G12V

Kirsten Rat Sarcoma viral oncogene homolog (KRAS) is one of the most frequent oncogenes. However, there are limited treatment options due to its intracellular expression. To address this, we developed a novel bispecific T-cell engager (BiTE) antibody targeting HLA-A2/KRAS G12V complex and CD3 (HLA-G12V/CD3 BiTE). We examined its specific binding to tumor cells and T cells, as well as its anti-tumor effects in vivo. HLA-G12V/CD3 BiTE was expressed in Escherichia coli and its binding affinities to CD3 and HLA-A2/KRAS G12V were measured by flow cytometry, along with T-cell activation. In a xenograft pancreatic tumor model, the HLA-G12V/CD3 BiTE's anti-tumor effects were assessed through tumor growth, survival time, and safety. Our results demonstrated specific binding of HLA-G12V/CD3 BiTE to tumor cells with an HLA-A2/KRAS G12V mutation and T cells. The HLA-G12V/CD3 BiTE also activated T-cells in the presence of tumor cells in vitro. HLA-G12V/CD3 BiTE in vivo testing showed delayed tumor growth without severe toxicity to major organs and prolonged mouse survival. This study highlights the potential of constructing BiTEs recognizing an HLA-peptide complex and providing a novel therapy for cancer treatment targeting the intracellular tumor antigen.

Circulating Tumor DNA Dynamics Reveal KRAS G12C Mutation Heterogeneity and Response to Treatment with the KRAS G12C Inhibitor Divarasib in Solid Tumors

PURPOSE

To inform prognosis, treatment response, disease biology, and KRAS G12C mutation heterogeneity, we conducted exploratory circulating tumor DNA (ctDNA) profiling on 134 patients with solid tumors harboring a KRAS G12C mutation treated with single-agent divarasib (GDC-6036) in a phase 1 study.

EXPERIMENTAL DESIGN

Plasma samples were collected for serial ctDNA profiling at baseline (cycle 1 day 1 prior to treatment) and multiple on-treatment time points (cycle 1 day 15 and cycle 3 day 1).

RESULTS

KRAS G12C ctDNA was detectable from plasma samples in 72.9% (43/59) and 92.6% (50/54) of patients with non-small cell lung cancer and colorectal cancer, respectively, the majority of whom were eligible for study participation based on a local test detecting the KRAS G12C mutation in tumor tissue. Baseline ctDNA tumor fraction was associated with tumor type, disease burden, and metastatic sites. A decline in ctDNA level was observed as early as cycle 1 day 15. Serial assessment showed a decline in ctDNA tumor fraction associated with response and progression-free survival. Except for a few cases of KRAS G12C sub-clonality, on-treatment changes in KRAS G12C variant allele frequency mirrored changes in the overall ctDNA tumor fraction.

CONCLUSIONS

Across tumor types, the KRAS G12C mutation likely represents a truncal mutation in the majority of patients. Rapid and deep decline in ctDNA tumor fraction was observed in patients responding to divarasib treatment. Early on-treatment dynamics of ctDNA were associated with patient outcomes and tumor response to divarasib treatment.

Signaling proteins in HSC fate determination are unequally segregated during asymmetric cell division

Hematopoietic stem cells (HSCs) continuously replenish mature blood cells with limited lifespans. To maintain the HSC compartment while ensuring output of differentiated cells, HSCs undergo asymmetric cell division (ACD), generating two daughter cells with different fates: one will proliferate and give rise to the differentiated cells' progeny, and one will return to quiescence to maintain the HSC compartment. A balance between MEK/ERK and mTORC1 pathways is needed to ensure HSC homeostasis. Here, we show that activation of these pathways is spatially segregated in premitotic HSCs and unequally inherited during ACD. A combination of genetic and chemical perturbations shows that an ERK-dependent mechanism determines the balance between pathways affecting polarity, proliferation, and metabolism, and thus determines the frequency of asymmetrically dividing HSCs. Our data identify druggable targets that modulate HSC fate determination at the level of asymmetric division.

Potent therapeutic strategy in gastric cancer with microsatellite instability-high and/or deficient mismatch repair

Gastric cancer (GC) is a common malignancy that presents challenges in patient care worldwide. The mismatch repair (MMR) system is a highly conserved DNA repair mechanism that protects genome integrity during replication. Deficient MMR (dMMR) results in an increased accumulation of genetic errors in microsatellite sequences, leading to the development of a microsatellite instability-high (MSI-H) phenotype. Most MSI-H/dMMR GCs arise sporadically, mainly due to MutL homolog 1 (MLH1) epigenetic silencing. Unlike microsatellite-stable (MSS)/proficient MMR (pMMR) GCs, MSI-H/dMMR GCs are relatively rare and represent a distinct subtype with genomic instability, a high somatic mutational burden, favorable immunogenicity, different responses to treatment, and prognosis. dMMR/MSI-H status is a robust predictive biomarker for treatment with immune checkpoint inhibitors (ICIs) due to high neoantigen load, prominent tumor-infiltrating lymphocytes, and programmed cell death ligand 1 (PD-L1) overexpression. However, a subset of MSI-H/dMMR GC patients does not benefit from immunotherapy, highlighting the need for further research into predictive biomarkers and resistance mechanisms. This review provides a comprehensive overview of the clinical, molecular, immunogenic, and therapeutic aspects of MSI-H/dMMR GC, with a focus on the impact of ICIs in immunotherapy and their potential as neoadjuvant therapies. Understanding the complexity and diversity of the molecular and immunological profiles of MSI-H/dMMR GC will drive the development of more effective therapeutic strategies and molecular targets for future precision medicine.

Cooperative genomic lesions in HRAS-mutant cancers predict resistance to farnesyltransferase inhibitors

In the clinical development of farnesyltransferase inhibitors (FTIs) for HRAS-mutant tumors, responses varied by cancer type. Co-occurring mutations may affect responses. We aimed to uncover cooperative genetic events specific to HRAS-mutant tumors and to study their effect on sensitivity to FTIs. Using targeted sequencing data from the MSK-IMPACT and Dana-Farber Cancer Institute Genomic Evidence Neoplasia Information Exchange databases, we identified comutations that were observed predominantly in HRAS-mutant versus KRAS-mutant or NRAS-mutant cancers. HRAS-mutant cancers had a higher frequency of coaltered mutations (48.8%) in the MAPK, PI3K, or RTK pathway genes, compared with KRAS-mutant (41.4%) and NRAS-mutant (38.4%) cancers (p < 0.05). Class 3 BRAF, NF1, PTEN, and PIK3CA mutations were more prevalent in HRAS-mutant lineages. To study the effects of comutations on sensitivity to FTIs, HrasG13R was transfected into "RASless" (Kraslox/lox/Hras-/-/Nras-/-/RERTert/ert) mouse embryonic fibroblasts (MEFs), which sensitized nontransfected MEFs to tipifarnib. Comutation in the form of Pten or Nf1 deletion and Pik3caH1047R transduction led to resistance to tipifarnib in HrasG13R-transfected MEFs in the presence or absence of KrasWT, whereas BrafG466E transduction led to resistance to tipifarnib only in the presence of KrasWT. Combined treatment with tipifarnib and MEK inhibition sensitized cells to tipifarnib in all settings, including in MEFs with PI3K pathway comutations. HRAS-mutant tumors demonstrate lineage-dependent MAPK or PI3K pathway alterations, which confer resistance to tipifarnib. The combined use of FTIs and MEK inhibition is a promising strategy for HRAS-mutant tumors.

Preclinical evidence for employing MEK inhibition in NRAS mutated pediatric gastroenteropancreatic neuroendocrine-like tumors

BACKGROUND

Pediatric gastroenteropancreatic neuroendocrine tumors are exceedingly rare, resulting in most pediatric treatment recommendations being based on data derived from adults. Trametinib is a kinase inhibitor that targets MEK1/2 and has been employed in the treatment of cancers harboring mutations in the Ras pathway.

METHODS

We utilized an established human pediatric gastroenteropancreatic neuroendocrine-like tumor patient-derived xenograft (PDX) with a known NRAS mutation to study the effects of MEK inhibition. We evaluated the effects of trametinib on proliferation, motility, and tumor growth in vivo. We created an intraperitoneal metastatic model of this PDX, characterized both the phenotype and the genotype of the metastatic PDX and again, investigated the effects of MEK inhibition.

RESULTS

We found target engagement with decreased ERK1/2 phosphorylation with trametinib treatment. Trametinib led to decreased in vitro cell growth and motility, and decreased tumor growth and increased animal survival in a murine flank tumor model. Finally, we demonstrated that trametinib was able to significantly decrease gastroenteropancreatic neuroendocrine intraperitoneal tumor metastasis.

CONCLUSIONS

The results of these studies support the further investigation of MEK inhibition in pediatric NRAS mutated solid tumors.

Co-targeting SOS1 enhances the antitumor effects of KRASG12C inhibitors by addressing intrinsic and acquired resistance

Combination approaches are needed to strengthen and extend the clinical response to KRASG12C inhibitors (KRASG12Ci). Here, we assessed the antitumor responses of KRASG12C mutant lung and colorectal cancer models to combination treatment with a SOS1 inhibitor (SOS1i), BI-3406, plus the KRASG12C inhibitor, adagrasib. We found that responses to BI-3406 plus adagrasib were stronger than to adagrasib alone, comparable to adagrasib with SHP2 (SHP2i) or EGFR inhibitors and correlated with stronger suppression of RAS-MAPK signaling. BI-3406 plus adagrasib treatment also delayed the emergence of acquired resistance and elicited antitumor responses from adagrasib-resistant models. Resistance to KRASG12Ci seemed to be driven by upregulation of MRAS activity, which both SOS1i and SHP2i were found to potently inhibit. Knockdown of SHOC2, a MRAS complex partner, partially restored response to KRASG12Ci treatment. These results suggest KRASG12C plus SOS1i to be a promising strategy for treating both KRASG12Ci naive and relapsed KRASG12C-mutant tumors.

Immune status and combined immunotherapy progression in Kirsten rat sarcoma viral oncogene homolog (KRAS)-mutant tumors

Kirsten rat sarcoma viral oncogene homolog (KRAS) is the most frequently mutated oncogene, occurring in various tumor types. Despite extensive efforts over the past 40 years to develop inhibitors targeting KRAS mutations, resistance to these inhibitors has eventually emerged. A more precise understanding of KRAS mutations and the mechanism of resistance development is essential for creating novel inhibitors that target specifically KRAS mutations and can delay or overcome resistance. Immunotherapy has developed rapidly in recent years, and in-depth dissection of the tumor immune microenvironment has led researchers to shift their focus to patients with KRAS mutations, finding that immune factors play an essential role in KRAS-mutant (KRAS-Mut) tumor therapy and targeted drug resistance. Breakthroughs and transitions from targeted therapy to immunotherapy have provided new hope for treating refractory patients. Here, we reviewed KRAS mutation-targeted treatment strategies and resistance issues, focusing on our in-depth exploration of the specific immune status of patients with KRAS mutations and the impact of body immunity following KRAS inhibition. We aimed to guide innovative approaches combining RAS inhibition with immunotherapy, review advances in preclinical and clinical stages, and discuss challenges and future directions.

Novel druggable space in human KRAS G13D discovered using structural bioinformatics and a P-loop targeting monoclonal antibody

KRAS belongs to a family of small GTPases that act as binary switches upstream of several signalling cascades, controlling proliferation and survival of cells. Mutations in KRAS drive oncogenesis, especially in pancreatic, lung, and colorectal cancers (CRC). Although historic attempts at targeting mutant KRAS with small molecule inhibitors have proven challenging, there are recent successes with the G12C, and G12D mutations. However, clinically important RAS mutations such as G12V, G13D, Q61L, and A146T, remain elusive drug targets, and insights to their structural landscape is of critical importance to develop novel, and effective therapeutic concepts. We present a fully open, P-loop exposing conformer of KRAS G13D by X-ray crystallography at 1.4-2.4 Å resolution in Mg2+-free phosphate and malonate buffers. The G13D conformer has the switch-I region displaced in an upright position leaving the catalytic core fully exposed. To prove that this state is druggable, we developed a P-loop-targeting monoclonal antibody (mAb). The mAb displayed high-affinity binding to G13D and was shown using high resolution fluorescence microscopy to be spontaneously taken up by G13D-mutated HCT 116 cells (human CRC derived) by macropinocytosis. The mAb inhibited KRAS signalling in phosphoproteomic and genomic studies. Taken together, the data propose novel druggable space of G13D that is reachable in the cellular context. It is our hope that these findings will stimulate attempts to drug this fully open state G13D conformer using mAbs or other modalities.

Capturing RAS oligomerization on a membrane

RAS GTPases associate with the biological membrane where they function as molecular switches to regulate cell growth. Recent studies indicate that RAS proteins oligomerize on membranes, and disrupting these assemblies represents an alternative therapeutic strategy. However, conflicting reports on RAS assemblies, ranging in size from dimers to nanoclusters, have brought to the fore key questions regarding the stoichiometry and parameters that influence oligomerization. Here, we probe three isoforms of RAS [Kirsten Rat Sarcoma viral oncogene (KRAS), Harvey Rat Sarcoma viral oncogene (HRAS), and Neuroblastoma oncogene (NRAS)] directly from membranes using mass spectrometry. We show that KRAS on membranes in the inactive state (GDP-bound) is monomeric but forms dimers in the active state (GTP-bound). We demonstrate that the small molecule BI2852 can induce dimerization of KRAS, whereas the binding of effector proteins disrupts dimerization. We also show that RAS dimerization is dependent on lipid composition and reveal that oligomerization of NRAS is regulated by palmitoylation. By monitoring the intrinsic GTPase activity of RAS, we capture the emergence of a dimer containing either mixed nucleotides or GDP on membranes. We find that the interaction of RAS with the catalytic domain of Son of Sevenless (SOScat) is influenced by membrane composition. We also capture the activation and monomer to dimer conversion of KRAS by SOScat. These results not only reveal the stoichiometry of RAS assemblies on membranes but also uncover the impact of critical factors on oligomerization, encompassing regulation by nucleotides, lipids, and palmitoylation.

Strategies to enhance the therapeutic efficacy of anti-PD-1 antibody, anti-PD-L1 antibody and anti-CTLA-4 antibody in cancer therapy

Although immune checkpoint inhibitors (anti-PD-1 antibody, anti-PD-L1 antibody, and anti-CTLA-4 antibody) have displayed considerable success in the treatment of malignant tumors, the therapeutic effect is still unsatisfactory for a portion of patients. Therefore, it is imperative to develop strategies to enhance the effect of these ICIs. Increasing evidence strongly suggests that the key to this issue is to transform the tumor immune microenvironment from a state of no or low immune infiltration to a state of high immune infiltration and enhance the tumor cell-killing effect of T cells. Therefore, some combination strategies have been proposed and this review appraise a summary of 39 strategies aiming at enhancing the effectiveness of ICIs, which comprise combining 10 clinical approaches and 29 foundational research strategies. Moreover, this review improves the comprehensive understanding of combination therapy with ICIs and inspires novel ideas for tumor immunotherapy.

Functional and structural insights into RAS effector proteins

RAS proteins are conserved guanosine triphosphate (GTP) hydrolases (GTPases) that act as molecular binary switches and play vital roles in numerous cellular processes. Upon GTP binding, RAS GTPases adopt an active conformation and interact with specific proteins termed RAS effectors that contain a conserved ubiquitin-like domain, thereby facilitating downstream signaling. Over 50 effector proteins have been identified in the human proteome, and many have been studied as potential mediators of RAS-dependent signaling pathways. Biochemical and structural analyses have provided mechanistic insights into these effectors, and studies using model organisms have complemented our understanding of their role in physiology and disease. Yet, many critical aspects regarding the dynamics and biological function of RAS-effector complexes remain to be elucidated. In this review, we discuss the mechanisms and functions of known RAS effector proteins, provide structural perspectives on RAS-effector interactions, evaluate their significance in RAS-mediated signaling, and explore their potential as therapeutic targets.

Structure-activity relationships of middle-size cyclic peptides, KRAS inhibitors derived from an mRNA display

Cyclic peptides are attracting attention as therapeutic agents due to their potential for oral absorption and easy access to tough intracellular targets. LUNA18, a clinical KRAS inhibitor, was transformed-without scaffold hopping-from the initial hit by using an mRNA display library that met our criteria for drug-likeness. In drug discovery using mRNA display libraries, hit compounds always possess a site linked to an mRNA tag. Here, we describe our examination of the Structure-Activity Relationship (SAR) using X-ray structures for chemical optimization near the site linked to the mRNA tag, equivalent to the C-terminus. Structural modifications near the C-terminus demonstrated a relatively wide range of tolerance for side chains. Furthermore, we show that a single atom modification is enough to change the pharmacokinetic (PK) profile. Since there are four positions where side chain modification is permissible in terms of activity, it is possible to flexibly adjust the pharmacokinetic profile by structurally optimizing the side chain. The side chain transformation findings demonstrated here may be generally applicable to hits obtained from mRNA display libraries.

TRIM24 Cooperates with Ras Mutation to Drive Glioma Progression through snoRNA Recruitment of PHAX and DNA-PKcs

The factors driving glioma progression remain poorly understood. Here, the epigenetic regulator TRIM24 is identified as a driver of glioma progression, where TRIM24 overexpression promotes HRasV12 anaplastic astrocytoma (AA) progression into epithelioid GBM (Ep-GBM)-like tumors. Co-transfection of TRIM24 with HRasV12 also induces Ep-GBM-like transformation of human neural stem cells (hNSCs) with tumor protein p53 gene (TP53) knockdown. Furthermore, TRIM24 is highly expressed in clinical Ep-GBM specimens. Using single-cell RNA-sequencing (scRNA-Seq), the authors show that TRIM24 overexpression impacts both intratumoral heterogeneity and the tumor microenvironment. Mechanically, HRasV12 activates phosphorylated adaptor for RNA export (PHAX) and upregulates U3 small nucleolar RNAs (U3 snoRNAs) to recruit Ku-dependent DNA-dependent protein kinase catalytic subunit (DNA-PKcs). Overexpressed TRIM24 is also recruited by PHAX to U3 snoRNAs, thereby facilitating DNA-PKcs phosphorylation of TRIM24 at S767/768 residues. Phosphorylated TRIM24 induces epigenome and transcription factor network reprogramming and promotes Ep-GBM-like transformation. Targeting DNA-PKcs with the small molecule inhibitor NU7441 synergizes with temozolomide to reduce Ep-GBM tumorigenicity and prolong animal survival. These findings provide new insights into the epigenetic regulation of Ep-GBM-like transformation and suggest a potential therapeutic strategy for patients with Ep-GBM.

Pathways and mechanism of MRTX1133 binding to KRAS G12D elucidated by molecular dynamics simulations and Markov state models

KRAS G12D is the most common oncogenic mutation identified in several types of cancer. Therefore, design of inhibitors targeting KRAS G12D represents a promising strategy for anticancer therapy. MRTX1133 is a highly potent inhibitor (approximate experiment Kd ≈ 0.0002 nM) of KRAS G12D and is currently in Phase 1/2 study, however, pathways of the compound binding to KRAS G12D has remained unknown, and the mechanism underlying the complicated dynamic process are challenging to capture experimentally, which hinder the structure-based anti-cancer drug design. Here, using MRTX1133 as a probe, unbiased molecular dynamics (MD) was used to simulate the process of MRTX1133 spontaneously binding to KRAS G12D. In six of 42 independent MD simulation (a total of 99 μs), MRTX1133 was observed to successfully associate with KRAS G12D. The kinetically metastable states refer to the potential pathways of MRTX1133 binding to KRAS G12D were revealed by Markov state models (MSM) analysis. Additionally, 8 key residues that are essential for MRTX1133 recognition and tight binding at the preferred low energy states were identified by MM/GBSA analysis. In sum, this study provides a new perspective on understanding the pathways and mechanism of MRTX1133 binding to KRAS G12D.

Plasma ctDNA enhances the tissue-based detection of oncodriver mutations in colorectal cancer

PURPOSE

The advent of circulating tumor DNA (ctDNA) technology has provided a convenient and noninvasive means to continuously monitor cancer genomic data, facilitating personalized cancer treatment. This study aimed to evaluate the supplementary benefits of plasma ctDNA alongside traditional tissue-based next-generation sequencing (NGS) in identifying targetable mutations and tumor mutational burden (TMB) in colorectal cancers (CRC).

METHODS

Our study involved 76 CRC patients, collecting both tissue and plasma samples for NGS. We assessed the concordance of gene mutational status between ctDNA and tissue, focusing on actionable genes such as KRAS, NRAS, PIK3CA, BRAF, and ERBB2. Logistic regression analysis was used to explore variables associated with discordance and positive mutation rates.

RESULTS

In total, 26 cancer-related genes were identified. The most common variants in tumor tissues and plasma samples were in APC (57.9% vs 19.7%), TP53 (55.3% vs 22.4%) and KRAS (47.4% vs 43.4%). Tissue and ctDNA showed an overall concordance of 73.53% in detecting actionable gene mutations. Notably, plasma ctDNA improved detection for certain genes and gene pools. Variables significantly associated with discordance included gender and peritoneal metastases. TMB analysis revealed a higher detection rate in tissues compared to plasma, but combining both increased detection.

CONCLUSIONS

Our study highlights the importance of analyzing both tissue and plasma for detecting actionable mutations in CRC, with plasma ctDNA offering added value. Discordance is associated with gender and peritoneal metastases, and TMB analysis can benefit from a combination of tissue and plasma data. This approach provides valuable insights for personalized CRC treatment.

Targeting guanine nucleotide exchange factors for novel cancer drug discovery

INTRODUCTION

Guanine nucleotide exchange factors (GEFs) regulate the activation of small GTPases (G proteins) of the Ras superfamily proteins controlling cellular functions. Ras superfamily proteins act as 'molecular switches' that are turned 'ON' by guanine exchange. There are five major groups of Ras family GTPases: Ras, Ran, Rho, Rab and Arf, with a variety of different GEFs regulating their GTP loading. GEFs have been implicated in various diseases including cancer. This makes GEFs attractive targets to modulate signaling networks controlled by small GTPases.

AREAS COVERED

In this review, the roles and mechanisms of GEFs in malignancy are outlined. The mechanism of guanine exchange activity by GEFs on a small GTPase is illustrated. Then, some examples of GEFs that are significant in cancer are presented with a discussion on recent progress in therapeutic targeting efforts using a variety of approaches.

EXPERT OPINION

Recently, GEFs have emerged as potential therapeutic targets for novel cancer drug development. Targeting small GTPases is challenging; thus, targeting their activation by GEFs is a promising strategy. Most GEF-targeted drugs are still in preclinical development. A deeper biological understanding of the underlying mechanisms of GEF activity and utilizing advanced technology are necessary to enhance drug discovery for GEFs in cancer.

Mapping protein binding sites by photoreactive fragment pharmacophores

Fragment screening is a popular strategy of generating viable chemical starting points especially for challenging targets. Although fragments provide a better coverage of chemical space and they have typically higher chance of binding, their weak affinity necessitates highly sensitive biophysical assays. Here, we introduce a screening concept that combines evolutionary optimized fragment pharmacophores with the use of a photoaffinity handle that enables high hit rates by LC-MS-based detection. The sensitivity of our screening protocol was further improved by a target-conjugated photocatalyst. We have designed, synthesized, and screened 100 diazirine-tagged fragments against three benchmark and three therapeutically relevant protein targets of different tractability. Our therapeutic targets included a conventional enzyme, the first bromodomain of BRD4, a protein-protein interaction represented by the oncogenic KRasG12D protein, and the yet unliganded N-terminal domain of the STAT5B transcription factor. We have discovered several fragment hits against all three targets and identified their binding sites via enzymatic digestion, structural studies and modeling. Our results revealed that this protocol outperforms screening traditional fully functionalized and photoaffinity fragments in better exploration of the available binding sites and higher hit rates observed for even difficult targets.

The systematic role of pancreatic cancer exosomes: distant communication, liquid biopsy and future therapy

Pancreatic cancer remains one of the most lethal diseases worldwide. Cancer-derived exosomes, benefiting from the protective role of the lipid membrane, exhibit remarkable stability in the circulatory system. These exosomes, released by tumor microenvironment, contain various biomolecules such as proteins, RNAs, and lipids that plays a pivotal role in mediating distant communication between the local pancreatic tumor and other organs or tissues. They facilitate the transfer of oncogenic factors to distant sites, contributing to the compromised body immune system, distant metastasis, diabetes, cachexia, and promoting a microenvironment conducive to tumor growth and metastasis in pancreatic cancer patients. Beyond their intrinsic roles, circulating exosomes in peripheral blood can be detected to facilitate accurate liquid biopsy. This approach offers a novel and promising method for the diagnosis and management of pancreatic cancer. Consequently, circulating exosomes are not only crucial mediators of systemic cell-cell communication during pancreatic cancer progression but also hold great potential as precise tools for pancreatic cancer management and treatment. Exosome-based liquid biopsy and therapy represent promising advancements in the diagnosis and treatment of pancreatic cancer. Exosomes can serve as drug delivery vehicles, enhancing the targeting and efficacy of anticancer treatments, modulating the immune system, and facilitating gene editing to suppress tumor growth. Ongoing research focuses on biomarker identification, drug delivery systems, and clinical trials to validate the safety and efficacy of exosome-based therapies, offering new possibilities for early diagnosis and precision treatment in pancreatic cancer. Leveraging the therapeutic potential of exosomes, including their ability to deliver targeted drugs and modulate immune responses, opens new avenues for innovative treatment strategies.

Allosteric nanobodies to study the interactions between SOS1 and RAS

Protein-protein interactions (PPIs) are central in cell metabolism but research tools for the structural and functional characterization of these PPIs are often missing. Here we introduce broadly applicable immunization (Cross-link PPIs and immunize llamas, ChILL) and selection strategies (Display and co-selection, DisCO) for the discovery of diverse nanobodies that either stabilize or disrupt PPIs in a single experiment. We apply ChILL and DisCO to identify competitive, connective, or fully allosteric nanobodies that inhibit or facilitate the formation of the SOS1•RAS complex and modulate the nucleotide exchange rate on this pivotal GTPase in vitro as well as RAS signalling in cellulo. One of these connective nanobodies fills a cavity that was previously identified as the binding pocket for a series of therapeutic lead compounds. The long complementarity-determining region (CDR3) that penetrates this binding pocket serves as pharmacophore for extending the repertoire of potential leads.

Targeting Smurf1 to block PDK1-Akt signaling in KRAS-mutated colorectal cancer

The phosphoinositide 3-kinase (PI3K)-Akt axis is one of the most frequently activated pathways and is demonstrated as a therapeutic target in Kirsten rat sarcoma viral oncogene homolog (KRAS)-mutated colorectal cancer (CRC). Targeting the PI3K-Akt pathway has been a challenging undertaking through the decades. Here we unveiled an essential role of E3 ligase SMAD ubiquitylation regulatory factor 1 (Smurf1)-mediated phosphoinositide-dependent protein kinase 1 (PDK1) neddylation in PI3K-Akt signaling and tumorigenesis. Upon growth factor stimulation, Smurf1 immediately triggers PDK1 neddylation and the poly-neural precursor cell expressed developmentally downregulated protein 8 (poly-Nedd8) chains recruit methyltransferase SET domain bifurcated histone lysine methyltransferase 1 (SETDB1). The cytoplasmic complex of PDK1 assembled with Smurf1 and SETDB1 (cCOMPASS) consisting of PDK1, Smurf1 and SETDB1 directs Akt membrane attachment and T308 phosphorylation. Smurf1 deficiency dramatically reduces CRC tumorigenesis in a genetic mouse model. Furthermore, we developed a highly selective Smurf1 degrader, Smurf1-antagonizing repressor of tumor 1, which exhibits efficient PDK1-Akt blockade and potent tumor suppression alone or combined with PDK1 inhibitor in KRAS-mutated CRC. The findings presented here unveil previously unrecognized roles of PDK1 neddylation and offer a potential strategy for targeting the PI3K-Akt pathway and KRAS mutant cancer therapy.

Fibroblasts Promote Resistance to KRAS Silencing in Colorectal Cancer Cells

Colorectal cancer (CRC) responses to KRAS-targeted inhibition have been limited due to low response rates, the mechanisms of which remain unknown. Herein, we explored the cancer-associated fibroblasts (CAFs) secretome as a mediator of resistance to KRAS silencing. CRC cell lines HCT15, HCT116, and SW480 were cultured either in recommended media or in conditioned media from a normal colon fibroblast cell line (CCD-18Co) activated with rhTGF-β1 to induce a CAF-like phenotype. The expression of membrane stem cell markers was analyzed by flow cytometry. Stem cell potential was evaluated by a sphere formation assay. RNAseq was performed in KRAS-silenced HCT116 colonospheres treated with either control media or conditioned media from CAFs. Our results demonstrated that KRAS-silencing up-regulated CD24 and down-regulated CD49f and CD104 in the three cell lines, leading to a reduction in sphere-forming efficiency. However, CAF-secreted factors restored stem cell marker expression and increased stemness. RNA sequencing showed that CAF-secreted factors up-regulated genes associated with pro-tumorigenic pathways in KRAS-silenced cells, including KRAS, TGFβ, NOTCH, WNT, MYC, cell cycle progression and exit from quiescence, epithelial-mesenchymal transition, and immune regulation. Overall, our results suggest that resistance to KRAS-targeted inhibition might derive not only from cell-intrinsic causes but also from external elements, such as fibroblast-secreted factors.

KRAS Mutation Subtypes and Their Association with Other Driver Mutations in Oncogenic Pathways

The KRAS mutation stands out as one of the most influential oncogenic mutations, which directly regulates the hallmark features of cancer and interacts with other cancer-causing driver mutations. However, there remains a lack of precise information on their cooccurrence with mutated variants of KRAS and any correlations between KRAS and other driver mutations. To enquire about this issue, we delved into cBioPortal, TCGA, UALCAN, and Uniport studies. We aimed to unravel the complexity of KRAS and its relationships with other driver mutations. We noticed that G12D and G12V are the prevalent mutated variants of KRAS and coexist with the TP53 mutation in PAAD and CRAD, while G12C and G12V coexist with LUAD. We also noticed similar observations in the case of PIK3CA and APC mutations in CRAD. At the transcript level, a positive correlation exists between KRAS and PIK3CA and between APC and KRAS in CRAD. The existence of the co-mutation of KRAS and other driver mutations could influence the signaling pathway in the neoplastic transformation. Moreover, it has immense prognostic and predictive implications, which could help in better therapeutic management to treat cancer.

Clinical application of FIGO 2023 staging system of endometrial cancer in a Chinese cohort

OBJECTIVE

The International Federation of Gynecology and Obstetrics (FIGO) 2023 staging system for endometrial cancer (EC) was released with incorporating histology, lympho-vascular space invasion, and molecular classification together. Our objective is to further explore the clinical utility and prognostic significance of the 2023 FIGO staging system in China.

METHODS

A retrospective analysis was conducted for patients who received standard surgeries and underwent genetic testing using multigene next-generation sequencing (NGS) panels between December 2018 and December 2023 at Fudan University Shanghai Cancer Center, Shanghai, China. The genomic and clinical data of all patients were analyzed, and stages were determined by both the 2009 and 2023 FIGO staging systems. Kaplan-Meier estimators and Cox proportional hazards models were used for survival analysis.

RESULTS

A total of 547 patients were enrolled in the study. After the restaged by the FIGO 2023 staging system, stage shifts occurred in 147/547 (26.9%) patients. In patients with early stages in FIGO 2009 (stage I-II), 63 cases were rearranged to IAmPOLEmut and 53 cases to IICmp53abn due to the molecular classification of POLEmut and p53abn. Altogether 345 cases were in stage I, 107 cases in stage II, 69 cases in stage III, and 26 cases in stage IV according to the FIGO 2023 staging criteria. For stage I diseases, the 3-year PFS rate was 92.7% and 95.3% in 2009 and 2023 FIGO staging systems, respectively. The 3-year PFS of stage II in 2023 FIGO was lower than that of FIGO 2009 (3-year PFS: 85.0% versus 90.9%), especially in substage IIC and IICmp53abn. Three cases (12%) of stage IIIA in FIGO 2009 were shifted to stage IA3 FIGO 2023, with 3-year PFS rates of 90.9% versus 100%, respectively. In NGS analysis, the most prevalent gene alterations were observed in PTEN and PIK3CA.

CONCLUSION

The FIGO 2023 staging system was proved to be a good predictor of survival for EC patients with enhanced precision compared to FIGO 2009. Predominant stage shifts were observed in early-stage diseases. Distinct gene alterations of different subtypes may help to explore more accurate target therapies.