A review and perspective paper: Ras oncogene gets modest, from kingpin to mere henchman.

The concomitant activation of both the YAP1 co-transcription factor and RAS GTPases is a hallmark of several aggressive cancers, though the intricacies of their relationship and implications for oncogenesis are still poorly understood. This review has presented a cooperative model where YAP1 and RAS are not independently acting oncogenes but rather interdependently acting ones, with each fulfilling an essential role within the oncogenic process. YAP1 is responsible for initiating the expression of key proteins that contribute to various cancer traits. However, these proteins must often be transported into the cytoplasm to exert their effects. We suggest that oncogenic RAS actually facilitates this transport, enabling the phosphorylation and subsequent activation of the nuclear transporter XPO1 (aka Exportin1). This mechanism is particularly crucial for anti-apoptotic proteins. Instead of being sequestered within the nucleus in an ineffective state, these proteins are rather shuttled into the cytoplasm. Within the cytoplasm, they can effectively inhibit apoptosis, undermining by these means the efficacy of chemotherapeutic agents designed to induce cell death in cancer cells. Therefore, a clearer understanding of the oncogenic partnership between RAS and YAP1 will likely provide new insights into the molecular underpinnings of cancer and highlight as well potential targets for therapeutic interventions designed to disrupt this pernicious interaction.

Identification and Functional Analysis of Ras-Related Associated with Diabetes Gene (rrad) in Edwardsiella piscicida-Resistant Individuals of Japanese Flounder (Paralichthys olivaceus).

Ras-related associated with diabetes (RRAD) is a member of the Ras GTPase superfamily that plays a role in several cellular functions, such as cell proliferation and differentiation. In particular, the superfamily acts as an NF-κB signaling pathway inhibitor and calcium regulator to participate in the immune response pathway. A recent transcriptome study revealed that rrad was expressed in the spleen of disease-resistant Japanese flounder (Paralichthys olivaceus) individuals compared with disease-susceptible individuals, and the results were also verified by qPCR. Thus, the present study aimed to explore how rrad regulates antimicrobial immunity via the NF-κB pathway. First, the coding sequence of P. olivaceus rrad was identified. The sequence was 1092 bp in length, encoding 364 amino acids. Based on phylogenetic and structural relationship analyses, P. olivaceus rrad appeared to be more closely related to teleosts. Next, rrad expression differences between disease-resistant and disease-susceptible individuals in immune-related tissues were evaluated, and the results revealed that rrad was expressed preferentially in the spleen of disease-resistant individuals. In response to Edwardsiella piscicida infection, rrad expression in the spleen changed. In vitro, co-culture was carried out to assess the hypo-methylated levels of the rrad promoter in the disease-resistant spleen, which was consistent with the high mRNA expression. The siRNA-mediated knockdown of rrad performed with the gill cell line of P. olivaceus affected many rrad-network-related genes, i.e., dcp1b, amagt, rus1, rapgef1, ralbp1, plce1, rasal1, nckipsd, prkab2, cytbc-1, sh3, and others, as well as some inflammation-related genes, such as bal2 and Il-1ß. In addition, flow cytometry analysis showed that rrad overexpression was more likely to induce cell apoptosis, with establishing a link between rrad's function and its potential roles in regulating the NF-κB pathway. Thus,. the current study provided some clarity in terms of understanding the immune response about rrad gene differences between disease-resistant and disease-susceptible P. olivaceus individuals. This study provides a molecular basis for fish rrad gene functional analysis and may serve as a reference for in-depth of bacterial disease resistance of teleost.

MicroRNA-503 Suppresses Oral Mucosal Fibroblast Differentiation by Regulating RAS/RAF/MEK/ERK Signaling Pathway.

The abnormal proliferation and differentiation of oral mucosal fibroblasts (FBs) is the key to the progression of oral submucosal fibrosis. To clarify the mechanism of platelet-derived growth factor (PDGF-BB)-induced FBs fibrosis in oral mucosa, real-time quantitative polymerase chain reaction and Western blot were used in this study to detect the expression of miR-503 and the expression of p-MEK, p-ERK, miR-503, RAF, smooth actin and type I collagen under different time and concentration stimulation of PDGF-BB. The effects of overexpression of miR-503 or RAF on the proliferation and migration of FBs were detected by cell counting kit 8 and cell scratch assay, respectively. A dual luciferase reporter gene assay was used to verify the targeting effect of miR-503 on RAF. The results showed that miR-503 was downregulated in a dose- and time-dependent manner in PDGF-BB-induced FBs. In addition, RAF is a direct target of miR-503 and can be negatively regulated. Overexpression of RAF can promote FB proliferation, migration, differentiation, collagen synthesis, and activation of downstream molecules (MEK/ERK), while overexpression of miR-503 can partially reverse the effects of RAF. Therefore, miR-503 regulates the biological behavior of PDGF-BB-induced oral mucosal FBs by influencing the activation of the RAS/RAF/MEK/ERK signaling pathway.

Rabex-5 E3 and Rab5 GEF domains differ in their regulation of Ras, Notch, and PI3K signaling in Drosophila wing development.

Rabex-5 (also called RabGEF1), a protein originally characterized for its Rab5 GEF function, also has an A20-like E3 ubiquitin ligase domain. We and others reported that Rabex-5 E3 activity promotes Ras mono- and di-ubiquitination to inhibit Ras signaling in Drosophila and mammals. Subsequently, we reported that Rabex-5 inhibits Notch signaling in the Drosophila hematopoietic system. Here we report genetic interactions using Rabex-5 transgenes encoding domain-specific mutations that show that Rabex-5 requires an intact E3 domain to inhibit Notch signaling in the epithelial tissue of the developing wing. Surprisingly, we discovered that Rabex-5 with an impaired E3 domain but active Rab5 GEF domain suppresses Notch loss-of-function phenotypes and enhances both Notch duplication phenotypes and activated Ras phenotypes consistent with a model that the Rab5 GEF activity of Rabex-5 might positively regulate Ras and Notch. Positive and negative regulation of developmental signaling by its different catalytic domains could allow Rabex-5 to precisely coordinate developmental signaling to fine-tune patterning. Finally, we report that Rabex-5 also inhibits the overgrowth due to loss of PTEN or activation of PI3K but not activation of AKT. Inhibition of Ras, Notch, and PI3K signaling may explain why Rabex-5 is deleted in some cancers. Paradoxically, Rabex-5 is reported to be an oncogene in other cancers. We propose that Rabex-5 acts as a tumor suppressor via its E3 activity to inhibit Ras, Notch, and PI3K signaling and as an oncogene via its Rab5 GEF activity to enhance Ras and Notch signaling.

EMP1 knockdown mitigated high glucose-induced pyroptosis and oxidative stress in rat H9c2 cardiomyocytes by inhibiting the RAS/RAF/MAPK signaling pathway.

The purpose of this study was to investigate the mechanism of EMP1 action in high glucose (HG)-induced H9c2 cardiac cell pyroptosis and oxidative injury. Rat cardiomyocytes H9c2 were exposed to 33 mM glucose for 24, 48, or 72 h to induce cytotoxicity. EMP1-siRNA, NLRP3 agonist Nigericin, and pcNDA-RAS were used to treat H9c2 cells under HG conditions. Cell Counting Kit (CCK)-8 assay showed that cell proliferation was decreased following HG induction, which was rescued by EMP1 knockdown. Our results also suggested that EMP1 siRNA transfection significantly decreased the apoptosis and pyroptosis of HG-induced cells, as indicated by the reduction of NLRP3 IL-1ß, ASC, GSDMD, cleaved-caspase1 and cleaved-caspase3 levels in HG-induced H9c2 cells. In addition, EMP1 knockdown alleviated HG-induced mitochondrial damage and oxidative stress in H9c2 cells. NLRP3 activation reversed the inhibitory effects of EMP1 knockdown on pyroptosis and oxidative stress in HG-induced H9c2 cells. Mechanistically, we found that EMP1 knockdown suppressed the RAS/RAF/MAPK signaling pathway in HG-induced H9c2 cells. RAS overexpression blocked the protective effect of EMP1 knockdown on HG-induced H9c2 cell apoptosis, pyroptosis, and oxidative injury. Our findings suggest that EMP1 knockdown treatment might provide a novel therapy for diabetic cardiomyopathy.

Germline mutations in a G protein identify signaling cross-talk in T cells.

Humans with monogenic inborn errors responsible for extreme disease phenotypes can reveal essential physiological pathways. We investigated germline mutations in GNAI2, which encodes Gαi2, a key component in heterotrimeric G protein signal transduction usually thought to regulate adenylyl cyclase-mediated cyclic adenosine monophosphate (cAMP) production. Patients with activating Gαi2 mutations had clinical presentations that included impaired immunity. Mutant Gαi2 impaired cell migration and augmented responses to T cell receptor (TCR) stimulation. We found that mutant Gαi2 influenced TCR signaling by sequestering the guanosine triphosphatase (GTPase)-activating protein RASA2, thereby promoting RAS activation and increasing downstream extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)-AKT S6 signaling to drive cellular growth and proliferation.

GAD1 ameliorates glioma progression through regulating cuproptosis via RAS/MAPK pathway.

Glioma represents a primary malignant tumor occurring in the central nervous system. Glutamate decarboxylase (GAD1) plays a significant role in tumor development; however, its function of GAD1 and underlying mechanisms in glioma progression remain unclear. Differentially expressed genes (DEGs) obtained from the GSE12657 and GSE15209 datasets that intersected with cuproptosis-related genes and pivot genes were identified using comprehensive bioinformatics methods. The elesclomol (ES) treatment was used to induce cuproptosis in U251 cells, which was validated by detecting intracellular copper levels and cuproptosis marker expression. Lentivirus-mediated gene overexpression was performed to explore the effects of GAD1 using functional assays in vitro and in a mouse xenograft model. The RAS agonist ML098 was used to verify the effect of GAD1 on the RAS/MAPK pathway in glioma cells. A total of 87 cuproptosis-related DEGs and seven hub genes were obtained, with five genes upregulated and two were downregulated in gliomas. Overexpression of GAD1 inhibited proliferation, invasion, and migration, promoted apoptosis of glioma cells, and suppressed tumorigenesis in vivo. In addition, GAD1 overexpression enhanced the sensitivity of glioma cells to cuproptosis. Additionally, ML098 treatment attenuated the inhibitory effect of GAD1 overexpression on the malignant phenotype of ES-treated cells. GAD1 plays an anti-oncogenic role in glioma by regulating apoptosis via inhibition of the RAS/MAPK pathway.

Interferon-Induced Transmembrane Protein 1 (IFITM1) Is Downregulated in Neurofibromatosis Type 1-Associated Malignant Peripheral Nerve Sheath Tumors.

Neurofibromatosis type 1 (NF1), an autosomal dominant genetic disorder, is caused by mutations in the NF1 gene, which encodes the GTPase-activating protein neurofibromin. The pathogenesis of the tumor progression of benign plexiform neurofibromas (PNs) and malignant peripheral nerve sheath tumors (MPNSTs) remain unclear. Here, we found that interferon-induced transmembrane protein 1 (IFITM1) was downregulated in MPNST tissues compared to those in PN tissues from patients with NF1. Overexpression of IFITM1 in NF1-associated MPNST cells resulted in a significant decrease in Ras activation (GTP-Ras) and downstream extracellular regulatory kinase 1/2 (ERK1/2) phosphorylation, whereas downregulation of IFITM1 via treatment with small interfering RNA in normal Schwann cells had the opposite result, indicating that expression levels of IFITM1 are closely associated with tumor progression in NF1. Treatment of MPNST cells with interferon-gamma (IFN-γ) significantly augmented the expression of IFITM1, thereby leading to a decrease in Ras and ERK1/2 activation. Despite the small number of patient samples, these findings may potentially provide a new target for chemotherapy in patients with NF1-associated MPNSTs. In xenograft mice injected with MPNST cells, IFN-γ treatment successfully suppressed tumor progression with increased IFITM1 expression and decreased Ras and ERK1/2 activation in tumor tissues. Collectively, these results suggest that IFITM1 is closely involved in MPNST pathogenesis and that IFN-γ is a good candidate for the therapeutic treatment of MPNSTs in NF1.

The ER-Resident Ras Inhibitor 1 (Eri1) of Candida albicans Inhibits Hyphal Morphogenesis via the Ras-Independent cAMP-PKA Pathway.

Ras signaling and glycosylphosphatidylinositol (GPI) biosynthesis are mutually inhibitory in S. cerevisiae (Sc). The inhibition is mediated via an interaction of yeast Ras2 with the Eri1 subunit of its GPI-N-acetylglucosaminyl transferase (GPI-GnT), the enzyme catalyzing the very first GPI biosynthetic step. In contrast, Ras signaling and GPI biosynthesis in C. albicans (Ca) are mutually activated and together control the virulence traits of the human fungal pathogen. What might be the role of Eri1 in this pathogen? The present manuscript addresses this question while simultaneously characterizing the cellular role of CaEri1. It is either nonessential or required at very low levels for cell viability in C. albicans. Severe depletion of CaEri1 results in reduced GPI biosynthesis and cell wall defects. It also produces hyperfilamentation phenotypes in Spider medium as well as in bicarbonate medium containing 5% CO2, suggesting that both the Ras-dependent and Ras-independent cAMP-PKA pathways for hyphal morphogenesis are activated in these cells. Pull-down and acceptor-photobleaching FRET experiments suggest that CaEri1 does not directly interact with CaRas1 but does so through CaGpi2, another GPI-GnT subunit. We showed previously that CaGpi2 is downstream of CaEri1 in cross talk with CaRas1 and for Ras-dependent hyphal morphogenesis. Here we show that CaEri1 is downstream of all GPI-GnT subunits in inhibiting Ras-independent filamentation. CaERI1 also participates in intersubunit transcriptional cross talk within the GPI-GnT, a feature unique to C. albicans. Virulence studies using G. mellonella larvae show that a heterozygous strain of CaERI1 is better cleared by the host and is attenuated in virulence.

5-Aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase promotes pulmonary arterial smooth muscle cell proliferation via the Ras signaling pathway.

Pulmonary arterial hypertension (PAH) is a debilitating vascular disorder characterized by abnormal pulmonary artery smooth muscle cell (PASMC) proliferation and collagen synthesis, contributing to vascular remodeling and elevated pulmonary vascular resistance. This study investigated the critical role of 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/inosine monophosphate cyclohydrolase (ATIC) in cell proliferation and collagen synthesis in PASMCs in PAH. Here we show that ATIC levels are significantly increased in the lungs of monocrotaline (MCT)-induced PAH rat model, hypoxia-induced PAH mouse model, and platelet-derived growth factor (PDGF)-stimulated PASMCs. Inhibition of ATIC attenuated PDGF-induced cell proliferation and collagen I synthesis in PASMCs. Conversely, overexpression or knockdown of ATIC causes a significant promotion or inhibition of Ras and ERK activation, cell proliferation, and collagen synthesis in PASMCs. Moreover, ATIC deficiency attenuated Ras activation in the lungs of hypoxia-induced PAH mice. Furthermore, Ras inhibition attenuates ATIC overexpression- and PDGF-induced collagen synthesis and PASMC proliferation. Notably, we identified that transcription factors MYC, early growth response protein 1 (EGR1), and specificity protein 1 (SP1) directly binds to promoters of Atic gene and regulate ATIC expression. These results provide the first evidence that ATIC promotes PASMC proliferation in pulmonary vascular remodeling through the Ras signaling pathway.NEW & NOTEWORTHY Our findings highlight the important role of ATIC in the PASMC proliferation of pulmonary vascular remodeling through its modulation of the Ras signaling pathway and its regulation by transcription factors MYC, EGR1, and SP1. ATIC's modulation of Ras signal pathway represents a novel mechanism contributing to PAH development.

Crystal structure of the GDP-bound human M-RAS protein in two crystal forms.

M-RAS plays a crucial role in the RAF-MEK signaling pathway. When activated by GTP, M-RAS forms a complex with SHOC2 and PP1C, initiating downstream RAF-MEK signal transduction. In this study, the crystal structure of the GDP-bound human M-RAS protein is presented with two forms of crystal packing. Both the full-length and truncated human M-RAS structures aligned well with the high-confidence section of the AlphaFold2-predicted structure with low r.m.s.d., except for the Switch regions. Despite high sequence similarity to the available mouse M-RAS structure, the full-length human M-RAS structure exhibits unique crystal packing. This inactive human M-RAS structure could offer novel insights for the design of selective compounds targeting M-RAS.

Xmas-2 Protein, the Core Protein of the TREX-2 mRNA Export Complex, Does not Determine the Specificity of ras2 mRNA Binding by the Complex.

The TREX-2 complex of eukaryotes is responsible for the export of a wide range of mRNAs from the nucleus to the cytoplasm. Previously, we showed that a subunit of the D. melanogaster TREX-2 complex, the PCID2 protein, has a domain that specifically interacts with RNA. However, it remains unknown whether other components of the complex are involved in interaction with and recognition of the target mRNA. In the present study, we determined the role of Xmas-2, the core structural subunit of the complex, in the specific recognition of ras2 mRNA fragments. In this work, we showed that Xmas-2 interacts with ras2 mRNA independently of other subunits of the complex. We showed that RNA-binding domains are located in both the N-terminal domain and the C-terminal domain of Xmas-2. However, the interaction of the protein with ras2 mRNA fragments is independent of RNA sequence and structure and is nonspecific. Thus, the Xmas-2 subunit is not involved in the recognition of specific RNA sequences by the complex.

Biomarker Landscape in RASopathies.

RASopathies are a group of related genetic disorders caused by mutations in genes within the RAS/MAPK signaling pathway. This pathway is crucial for cell division, growth, and differentiation, and its disruption can lead to a variety of developmental and health issues. RASopathies present diverse clinical features and pose significant diagnostic and therapeutic challenges. Studying the landscape of biomarkers in RASopathies has the potential to improve both clinical practices and the understanding of these disorders. This review provides an overview of recent discoveries in RASopathy molecular profiling, which extend beyond traditional gene mutation analysis. mRNAs, non-coding RNAs, protein expression patterns, and post-translational modifications characteristic of RASopathy patients within pivotal signaling pathways such as the RAS/MAPK, PI3K/AKT/mTOR, and Rho/ROCK/LIMK2/cofilin pathways are summarized. Additionally, the field of metabolomics holds potential for uncovering metabolic signatures associated with specific RASopathies, which are crucial for developing precision medicine. Beyond molecular markers, we also examine the role of histological characteristics and non-invasive physiological assessments in identifying potential biomarkers, as they provide evidence of the disease's effects on various systems. Here, we synthesize key findings and illuminate promising avenues for future research in RASopathy biomarker discovery, underscoring rigorous validation and clinical translation.

Cardiac Phenotype and Gene Mutations in RASopathies.

Cardiac involvement is a major feature of RASopathies, a group of phenotypically overlapping syndromes caused by germline mutations in genes encoding components of the RAS/MAPK (mitogen-activated protein kinase) signaling pathway. In particular, Noonan syndrome (NS) is associated with a wide spectrum of cardiac pathologies ranging from congenital heart disease (CHD), present in approximately 80% of patients, to hypertrophic cardiomyopathy (HCM), observed in approximately 20% of patients. Genotype-cardiac phenotype correlations are frequently described, and they are useful indicators in predicting the prognosis concerning cardiac disease over the lifetime. The aim of this review is to clarify the molecular mechanisms underlying the development of cardiac diseases associated particularly with NS, and to discuss the main morphological and clinical characteristics of the two most frequent cardiac disorders, namely pulmonary valve stenosis (PVS) and HCM. We will also report the genotype-phenotype correlation and its implications for prognosis and treatment. Knowing the molecular mechanisms responsible for the genotype-phenotype correlation is key to developing possible targeted therapies. We will briefly address the first experiences of targeted HCM treatment using RAS/MAPK pathway inhibitors.

CLDN6 inhibits breast cancer growth and metastasis through SREBP1-mediated RAS palmitoylation.

BACKGROUND: Breast cancer (BC) ranks as the third most fatal malignant tumor worldwide, with a strong reliance on fatty acid metabolism. CLDN6, a candidate BC suppressor gene, was previously identified as a regulator of fatty acid biosynthesis; however, the underlying mechanism remains elusive. In this research, we aim to clarify the specific mechanism through which CLDN6 modulates fatty acid anabolism and its impact on BC growth and metastasis. METHODS: Cell function assays, tumor xenograft mouse models, and lung metastasis mouse models were conducted to evaluate BC growth and metastasis. Human palmitic acid assay, triglyceride assay, Nile red staining, and oil red O staining were employed to investigate fatty acid anabolism. Reverse transcription polymerase chain reaction (RT-PCR), western blot, immunohistochemistry (IHC) assay, nuclear fractionation, immunofluorescence (IF), immunoprecipitation and acyl-biotin exchange (IP-ABE), chromatin immunoprecipitation (ChIP), dual luciferase reporter assay, and co-immunoprecipitation (Co-IP) were applied to elucidate the underlying molecular mechanism. Moreover, tissue microarrays of BC were analyzed to explore the clinical implications. RESULTS: We identified that CLDN6 inhibited BC growth and metastasis by impeding RAS palmitoylation both in vitro and in vivo. We proposed a unique theory suggesting that CLDN6 suppressed RAS palmitoylation through SREBP1-modulated de novo palmitic acid synthesis. Mechanistically, CLDN6 interacted with MAGI2 to prevent KLF5 from entering the nucleus, thereby restraining SREBF1 transcription. The downregulation of SREBP1 reduced de novo palmitic acid synthesis, hindering RAS palmitoylation and subsequent endosomal sorting complex required for transport (ESCRT)-mediated plasma membrane localization required for RAS oncogenic activation. Besides, targeting inhibition of RAS palmitoylation synergized with CLDN6 to repress BC progression. CONCLUSIONS: Our findings provide compelling evidence that CLDN6 suppresses the palmitic acid-induced RAS palmitoylation through the MAGI2/KLF5/SREBP1 axis, thereby impeding BC malignant progression. These results propose a new insight that monitoring CLDN6 expression alongside targeting inhibition of palmitic acid-mediated palmitoylation could be a viable strategy for treating oncogenic RAS-driven BC.

Update on Pediatric Cancer Surveillance Recommendations for Patients with Neurofibromatosis Type 1, Noonan Syndrome, CBL Syndrome, Costello Syndrome, and Related RASopathies.

Neurofibromatosis type 1 (NF1), Noonan syndrome, and related syndromes, grouped as RASopathies, result from dysregulation of the RAS-MAPK pathway and demonstrate varied multisystemic clinical phenotypes. Together, RASopathies are among the more prevalent genetic cancer predisposition syndromes and require nuanced clinical management. When compared with the general population, children with RASopathies are at significantly increased risk of benign and malignant neoplasms. In the past decade, clinical trials have shown that targeted therapies can improve outcomes for low-grade and benign neoplastic lesions but have their own challenges, highlighting the multidisciplinary care needed for such individuals, specifically those with NF1. This perspective, which originated from the 2023 American Association for Cancer Research Childhood Cancer Predisposition Workshop, serves to update pediatric oncologists, neurologists, geneticists, counselors, and other health care professionals on revised diagnostic criteria, review previously published surveillance guidelines, and harmonize updated surveillance recommendations for patients with NF1 or RASopathies.

Peptidomic analysis reveals novel peptide PDLC promotes cell proliferation in hepatocellular carcinoma via Ras/Raf/MEK/ERK pathway.

Hepatocellular carcinoma (HCC) still presents poor prognosis with low overall survival rates and limited therapeutic options available. Recently, attention has been drawn to peptidomic analysis, an emerging field of proteomics for the exploration of new potential peptide drugs for the treatment of various diseases. However, research on the potential function of HCC peptides is lacking. Here, we analyzed the peptide spectrum in HCC tissues using peptidomic techniques and explored the potentially beneficial peptides involved in HCC. Changes in peptide profiles in HCC were examined using liquid chromatography-mass spectrometry (LC-MS/MS). Analyze the physicochemical properties and function of differently expressed peptides using bioinformatics. The effect of candidate functional peptides on HCC cell growth and migration was evaluated using the CCK-8, colony formation, and transwell assays. Transcriptome sequencing analysis and western blot were employed to delve into the mode of action of potential peptide on HCC. Peptidomic analysis of HCC tissue yielded a total of 8683 peptides, of which 452 exhibited up-regulation and 362 showed down-regulation. The peptides that were differentially expressed, according to bioinformatic analysis, were closely linked to carbon metabolism and the mitochondrial inner membrane. The peptide functional validation identified a novel peptide, PDLC (peptide derived from liver cancer), which was found to dramatically boost HCC cell proliferation through the Ras/Raf/MEK/ERK signaling cascade. Our research defined the peptide's properties and pattern of expression in HCC and identified a novel peptide, PDLC, with a function in encouraging HCC progression, offering an entirely new potential therapeutic target the disease.

The metastasis-promoting P1597L mutation in PlexinB1 enhances Ras activity.

BACKGROUND: Metastatic prostate cancer is a leading cause of cancer-related morbidity and mortality in men, yet the underlying molecular mechanisms are poorly understood. Plexins are transmembrane receptors for semaphorins with divergent roles in many forms of cancer. We recently found that a single clinically relevant specific amino acid change (Proline1597Leucine, (P1597L)), found in metastatic deposits of prostate cancer patients, converts PlexinB1 from a metastasis suppressor to a gene that drives prostate cancer metastasis in vivo. However, the mechanism by which PlexinB1(P1597L) promotes metastasis is not known. METHODS: Pull down assays using GST-RalGDS or -GSTRaf1-RBD were used to reveal the effect of mutant or wild-type PlexinB1 expression on Rap and Ras activity respectively. Protein-protein interactions were assessed in GST pulldown assays, Akt/ERK phosphorylation by immunoblotting and protein stability by treatment with cycloheximide. Rho/ROCK activity was monitored by measuring MLC2 phosphorylation and actin stress fiber formation. PlexinB1 function was measured using cell-collapse assays. RESULTS: We show here that the single clinically relevant P1597L amino acid change converts PlexinB1 from a repressor of Ras to a Ras activator. The PlexinB1(P1597L) mutation inhibits the RapGAP activity of PlexinB1, promoting a significant increase in Ras activity. The P1597L mutation also blocks PlexinB1-mediated reduction in Rho/ROCK activity, restraining the decrease in MLC2 phosphorylation and actin stress fiber formation induced by overexpression of wild-type PlexinB1. PlexinB1(P1597L) has little effect on the interaction of PlexinB1 with small GTPases or receptor tyrosine kinases and does not inhibit PlexinB1-stimulated Akt or ERK phosphorylation. These results indicate that the mutation affects Rho signalling via the Rap/Ras pathway. The PlexinB1(P1597L) mutation inhibits morphological cell collapse induced by wild-type PlexinB1 expression, suggesting that the mutation induces a loss of an inhibitory tumour suppressor function. CONCLUSION: These results suggest that the clinically relevant P1597L mutation in PlexinB1 may transform PlexinB1 from a suppressor to a driver of metastasis in mouse models of prostate cancer by reducing the RapGAP activity of PlexinB1, leading to Ras activation. These findings highlight the PlexinB1-Rap-Ras pathway for therapeutic intervention in prostate cancer.

Tislelizumab plus cetuximab and irinotecan in refractory microsatellite stable and RAS wild-type metastatic colorectal cancer: a single-arm phase 2 study.

Immunotherapy confers little to no benefit in the treatment of microsatellite stable (MSS) metastatic colorectal cancer (mCRC). Mechanistic insights suggested that epidermal growth factor receptor (EGFR) antibody plus irinotecan might augment the tumor immune response in mCRC. Therefore, we conducted a proof-of-concept, single-arm, phase 2 study (ChiCTR identifier: ChiCTR2000035642) of a combination treatment regimen including tislelizumab (anti-PD-1), cetuximab (anti-EGFR) and irinotecan in 33 patients with MSS and RAS wild-type (WT) mCRC who were previously treated with ≥2 lines of therapy. The primary endpoint was met, with a confirmed objective response rate of 33%. As secondary endpoints, the disease control rate was 79%, and the median progression-free survival and overall survival were 7.3 and 17.4 months respectively. Among the 33 patients, 32 (97.0%) had treatment-related adverse events (AEs). Three (9.1%) reported grade ≥ 3 AEs, including rash (n = 1), neutropenia (n = 2). The post-hoc evaluation of dynamic circulating tumor DNA using next generation sequencing and the analysis of peripheral immune proteomics landscape using Olink revealed that lower variant allele frequency (VAF) at baseline, greater reduction in VAF on treatment, and a hot peripheral macroenvironment were associated with the treatment response independently. Our study showed the antitumor activity of tislelizumab, cetuximab, and irinotecan combination with a tolerable safety profile in previously treated MSS and RAS WT mCRC.