Temporal dynamics of RAS mutations in circulating tumor DNA in metastatic colorectal cancer: clinical significance of mutation loss during treatment.

PURPOSE: In metastatic colorectal cancer (mCRC), RAS mutation loss may occur during the standard-of-care regimen. In this study, we aimed to investigate the temporal dynamics of the RAS gene and its clinical significance. METHODS: This was a retrospective, single-center study that included 82 patients with tissue RAS-mutant (RAS-MT) mCRC who underwent circulating tumor DNA (ctDNA) RAS monitoring between January, 2013-April, 2023. Patients were analyzed for the rate of change over time to acquired RAS mutation loss (aRAS-ML) and clinicopathological factors. The prognostic relevance of mutation loss was assessed. RESULTS: aRAS-ML was detected in 33 (40.2%) patients, 32 of whom had a mutation loss in the first ctDNA RAS assay. Patients with a RAS mutation detected in the first assay had a median time of 8 months until the second ctDNA RAS assay, with 4.5% cases newly converted to aRAS-ML; no new conversions were detected at the third assay. The aRAS-ML group exhibited more single-organ metastases in the target organ during ctDNA measurement (aRAS-ML: 84.8% vs. RAS-MT: 59.2%, p = 0.02). Of the 33 patients with aRAS-ML, seven (21.2%) received anti-epidermal growth factor receptor (EGFR) therapy, with a median progression-free survival of 8 months. Multivariate analysis revealed that persistent ctDNA RAS mutation was an independent prognostic factor for overall survival (hazard ratio: 2.7, 95% confidence interval: 1.1-6.3, p = 0.02). CONCLUSION: The rate of ctDNA mutation loss in patients with RAS-MT mCRC decreases over time. Therefore, using a ctDNA RAS assay early in treatment will assist in challenging the use of EGFR regimens.

Discriminating Interpatient Variabilities of RAS Gene Variants for Precision Detection of Thyroid Cancer.

Importance: Interpatient variabilities in genomic variants may reflect differences in tumor statuses among individuals. Objectives: To delineate interpatient variabilities in RAS variants in thyroid tumors based on the fifth World Health Organization classification of thyroid neoplasms and assess their diagnostic significance in cancer detection among patients with thyroid nodules. Design, Setting, and Participants: This prospective diagnostic study analyzed surgically resected thyroid tumors obtained from February 2016 to April 2022 and residual thyroid fine-needle aspiration (FNA) biopsies obtained from January 2020 to March 2021, at Mount Sinai Hospital, Toronto, Ontario, Canada. Data were analyzed from June 20, 2022, to October 15, 2023. Exposures: Quantitative detection of interpatient disparities of RAS variants (ie, NRAS, HRAS, and KRAS) was performed along with assessment of BRAF V600E and TERT promoter variants (C228T and C250T) by detecting their variant allele fractions (VAFs) using digital polymerase chain reaction assays. Main Outcomes and Measures: Interpatient differences in RAS, BRAF V600E, and TERT promoter variants were analyzed and compared with surgical histopathologic diagnoses. Malignancy rates, sensitivity, specificity, positive predictive values, and negative predictive values were calculated. Results: A total of 438 surgically resected thyroid tumor tissues and 249 thyroid nodule FNA biopsies were obtained from 620 patients (470 [75.8%] female; mean [SD] age, 50.7 [15.9] years). Median (IQR) follow-up for patients who underwent FNA biopsy analysis and subsequent resection was 88 (50-156) days. Of 438 tumors, 89 (20.3%) were identified with the presence of RAS variants, including 51 (11.6%) with NRAS, 29 (6.6%) with HRAS, and 9 (2.1%) with KRAS. The interpatient differences in these variants were discriminated at VAF levels ranging from 0.15% to 51.53%. The mean (SD) VAF of RAS variants exhibited no significant differences among benign nodules (39.2% [11.2%]), noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTPs) (25.4% [14.3%]), and malignant neoplasms (33.4% [13.8%]) (P = .28), although their distribution was found in 41.7% of NIFTPs and 50.7% of invasive encapsulated follicular variant papillary thyroid carcinomas (P < .001). RAS variants alone, regardless of a low or high VAF, were significantly associated with neoplasms at low risk of tumor recurrence (60.7% of RAS variants vs 26.9% of samples negative for RAS variants; P < .001). Compared with the sensitivity of 54.2% (95% CI, 48.8%-59.4%) and specificity of 100% (95% CI, 94.8%-100%) for BRAF V600E and TERT promoter variant assays, the inclusion of RAS variants into BRAF and TERT promoter variant assays improved sensitivity to 70.5% (95% CI, 65.4%-75.2%), albeit with a reduction in specificity to 88.8% (95% CI, 79.8%-94.1%) in distinguishing malignant neoplasms from benign and NIFTP tumors. Furthermore, interpatient differences in 5 gene variants (NRAS, HRAS, KRAS, BRAF, and TERT) were discriminated in 54 of 126 indeterminate FNAs (42.9%) and 18 of 76 nondiagnostic FNAs (23.7%), and all tumors with follow-up surgical pathology confirmed malignancy. Conclusions and Relevance: This diagnostic study delineated interpatient differences in RAS variants present in thyroid tumors with a variety of histopathological diagnoses. Discrimination of interpatient variabilities in RAS in combination with BRAF V600E and TERT promoter variants could facilitate cytology examinations in preoperative precision malignancy diagnosis among patients with thyroid nodules.

The RAS oncogene in brain tumors and the involvement of let-7 microRNA.

RAS oncogenes are master regulator genes in many cancers. In general, RAS-driven cancers have an oncogenic RAS mutation that promotes disease progression (colon, lung, pancreas). In contrast, brain tumors are not necessarily RAS-driven cancers because RAS mutations are rarely observed. In particular, glioblastomas (the most lethal brain tumor) do not appear to have dominant genetic mutations that are suitable for targeted therapy. Standard treatment for most brain tumors continues to focus on maximal surgical resection, radiotherapy and chemotherapy. Yet the convergence of genomic aberrations such as EGFR, PDGFR and NF1 (some of which are clinically effective) with activation of the RAS/MAPK cascade is still considered a key point in gliomagenesis, and KRAS is undoubtedly a driving gene in gliomagenesis in mice. In cancer, microRNAs (miRNA) are small, non-coding RNAs that regulate carcinogenesis. However, the functional consequences of aberrant miRNA expression in cancer are still poorly understood. let-7 encodes an intergenic miRNA that is classified as a tumour suppressor, at least in lung cancer. Let-7 suppresses a plethora of oncogenes such as RAS, HMGA, c-Myc, cyclin-D and thus suppresses cancer development, differentiation and progression. let-7 family members are direct regulators of certain RAS family genes by binding to the sequences in their 3'untranslated region (3'UTR). let-7 miRNA is involved in the malignant behaviour in vitro-proliferation, migration and invasion-of gliomas and stem-like glioma cells as well as in vivo models of glioblastoma multiforme (GBM) via KRAS inhibition. It also increases resistance to certain chemotherapeutic agents and radiotherapy in GBM. Although let-7 therapy is not yet established, this review updates the current state of knowledge on the contribution of miRNA let-7 in interaction with KRAS to the oncogenesis of brain tumours.

A Facile Method to Append a Bio-ID Tag to Endogenous Mutant Kras Alleles.

KRAS mutations occur in approximately ~50% of colorectal cancers (CRCs) and are associated with poor prognosis and resistance to therapy. While these most common mutations found at amino acids G12, G13, Q61, and A146 have long been considered oncogenic drivers of CRC, emerging clinical data suggest that each mutation may possess different biological functions, resulting in varying consequences in oncogenesis. Currently, the mechanistic underpinnings associated with each allelic variation remain unclear. Elucidating the unique effectors of each KRAS mutant could both increase the understanding of KRAS biology and provide a basis for allele-specific therapeutic opportunities. Biotinylation identification (BioID) is a method to label and identify proteins located in proximity of a protein of interest. These proteins are captured through the strong interaction between the biotin label and streptavidin bead and subsequently identified by mass spectrometry. Here, we developed a protocol using CRISPR-mediated gene editing to generate endogenous BioID2-tagged KrasG12D and KrasG12V isogenic murine colon epithelial cell lines to identify unique protein proximity partners by BioID.

The Abundance of KRAS and RAS Gene Mutations in Cancer.

Mutant forms of the RAS genes KRAS, NRAS, and HRAS are important and common drivers of cancer. Recently, two independent teams that integrated cancer genomics with cancer epidemiology estimated that approximately 15-20% of all human cancers harbor a mutation in one of these three RAS genes. These groups also estimate KRAS mutations occur in 11-14% of all human cancers. Although these estimates are lower than many commonly encountered values, these estimates continue to rank KRAS and the ensemble of RAS oncogenes among the most common genetic drivers of cancer across all forms of malignancy.

Cytogenetic abnormalities and TP53 and RAS gene profiles of childhood acute lymphoblastic leukemia in Morocco.

BACKGROUND: Recurrent genetic abnormalities affecting pivotal signaling pathways are the hallmark of childhood acute lymphoblastic leukemia (ALL). The identification of these aberrations remains clinically important. Therefore, we sought to determine the cytogenetic profile and the mutational status of TP53 and RAS genes among Moroccan childhood cases of ALL. METHODS: In total, 35 patients with childhood ALL were enrolled in the study. The diagnosis and treatment were established in the Pediatric Hematology and Oncology Center at the Children's Hospital of Rabat. Chromosome banding analysis and fluorescence in situ hybridization were used to detect genetic aberrations. Blood samples were screened for TP53 and RAS mutations using Sanger sequencing. RESULTS: Of the 35 cases, 30 were B-lineage ALL (85.7 %). Moreover, a male predominance was observed. Cytogenetic analysis revealed chromosomal anomalies in 27 cases (77.1 %). The most frequent aberrations were high hyperdiploidy and BCR/ABL rearrangement. Interestingly, we found the rare t(15;16) and the t(8;14), which are uncommon translocations in pediatric B-ALL. The mutational analysis revealed Pro72Arg (rs1042522:C > G) and Arg213Arg (rs1800372:A > G) in TP53. In correlation with cytogenetic data, rs1042522:C > G showed a significant association with the occurrence of chromosomal translocations (p = 0.04). However, no variant was detected in NRAS and KRAS genes. CONCLUSION: Our findings emphasize the significance of detecting chromosomal abnormalities as relevant prognostic markers. We also suggest a low occurrence of genetic variants among Moroccan children with ALL.

It took a long, long time: Ras and the race to cure cancer.

Discoveries of the roles of RAS oncogenes in cancer development four decades ago opened the door to proving that tumor development is driven by somatic mutations' altering the genomes of cancer cells. These discoveries led to illusions about the simplicity of cancer pathogenesis and how cancer could be cured.

Cooperative pro-tumorigenic adaptation to oncogenic RAS through epithelial-to-mesenchymal plasticity.

In breast cancers, aberrant activation of the RAS/MAPK pathway is strongly associated with mesenchymal features and stemness traits, suggesting an interplay between this mitogenic signaling pathway and epithelial-to-mesenchymal plasticity (EMP). By using inducible models of human mammary epithelial cells, we demonstrate herein that the oncogenic activation of RAS promotes ZEB1-dependent EMP, which is necessary for malignant transformation. Notably, EMP is triggered by the secretion of pro-inflammatory cytokines from neighboring RAS-activated senescent cells, with a prominent role for IL-6 and IL-1α. Our data contrast with the common view of cellular senescence as a tumor-suppressive mechanism and EMP as a process promoting late stages of tumor progression in response to signals from the tumor microenvironment. We highlighted here a pro-tumorigenic cooperation of RAS-activated mammary epithelial cells, which leverages on oncogene-induced senescence and EMP to trigger cellular reprogramming and malignant transformation.

Adeno-to-squamous transition drives resistance to KRAS inhibition in LKB1 mutant lung cancer.

KRASG12C inhibitors (adagrasib and sotorasib) have shown clinical promise in targeting KRASG12C-mutated lung cancers; however, most patients eventually develop resistance. In lung patients with adenocarcinoma with KRASG12C and STK11/LKB1 co-mutations, we find an enrichment of the squamous cell carcinoma gene signature in pre-treatment biopsies correlates with a poor response to adagrasib. Studies of Lkb1-deficient KRASG12C and KrasG12D lung cancer mouse models and organoids treated with KRAS inhibitors reveal tumors invoke a lineage plasticity program, adeno-to-squamous transition (AST), that enables resistance to KRAS inhibition. Transcriptomic and epigenomic analyses reveal ΔNp63 drives AST and modulates response to KRAS inhibition. We identify an intermediate high-plastic cell state marked by expression of an AST plasticity signature and Krt6a. Notably, expression of the AST plasticity signature and KRT6A at baseline correlates with poor adagrasib responses. These data indicate the role of AST in KRAS inhibitor resistance and provide predictive biomarkers for KRAS-targeted therapies in lung cancer.

KRAS allelic imbalance drives tumour initiation yet suppresses metastasis in colorectal cancer in vivo.

Oncogenic KRAS mutations are well-described functionally and are known to drive tumorigenesis. Recent reports describe a significant prevalence of KRAS allelic imbalances or gene dosage changes in human cancers, including loss of the wild-type allele in KRAS mutant cancers. However, the role of wild-type KRAS in tumorigenesis and therapeutic response remains elusive. We report an in vivo murine model of colorectal cancer featuring deletion of wild-type Kras in the context of oncogenic Kras. Deletion of wild-type Kras exacerbates oncogenic KRAS signalling through MAPK and thus drives tumour initiation. Absence of wild-type Kras potentiates the oncogenic effect of KRASG12D, while incidentally inducing sensitivity to inhibition of MEK1/2. Importantly, loss of the wild-type allele in aggressive models of KRASG12D-driven CRC significantly alters tumour progression, and suppresses metastasis through modulation of the immune microenvironment. This study highlights the critical role for wild-type Kras upon tumour initiation, progression and therapeutic response in Kras mutant CRC.

KRAS Pathways: A Potential Gateway for Cancer Therapeutics and Diagnostics.

One of the major disturbing pathways within cancer is "The Kirsten rat sarcoma viral oncogene homolog (KRAS) pathway", and it has recently been demonstrated to be the most crucial in therapies and diagnostics. KRAS pathway includes numerous genes. This multi-component signaling system promotes cell growth, division, survival, and death by transferring signals from outside the cell to its interior. KRAS regulates the activation of a variety of signaling molecules. The KRAS oncogene is a key player in advancing a wide range of malignancies, and the mutation rank of this gene is a key feature of several tumors. For some malignancies, the mutation type of the gene may offer information about prognostic, clinical, and predictive. KRAS belongs to the RAS oncogene family, which consists of a compilation of minor GTP-binding proteins that assimilate environmental inputs and trigger internal signaling pathways that control survival, cell differentiation, and proliferation. This review aims to examine the recent and fascinating breakthroughs in the identification of new therapies that target KRAS, including the ever-expanding experimental approaches for reducing KRAS activity and signaling as well as direct targeting of KRAS. A literature survey was performed. All the relevant articles and patents related to the KRAS pathway, the mutation in the KRAS gene, cancer treatment, and diagnostics were found on PubMed and Google Patents. One of the most prevalent causes of cancer in humans is a mutation in the K-RAS protein. It is extremely difficult to decipher KRAS-mediated signaling. It allows transducing signals to go from the cell's outer surface to its nucleus, having an influence on a variety of crucial cellular functions including cell chemotaxis, division, dissemination, and cell death. Other involved signaling pathways are RAF, and the phosphatidylinositol 3 kinase also known as AKT. The EGFR pathway is incomplete without KRAS. The activation of PI3K significantly contributes to acquiring resistance to a mixture of MEK inhibitors and anti-EGFR in colorectal cancer cell lines which are mutated by KRAS. A series of recent patent studies towards cancer diagnostics and therapeutics reveals the paramount importance of mutated protein KRAS as an extensive driver in human tumors. For the prognosis, diagnosis, and treatment of colorectal cancer, KRAS plays a critical role. This review concludes the latest and vowing developments in the discovery of novel techniques for diagnosis and drugs that target KRAS, the advancements in experimental techniques for signaling and inhibiting KRAS function, and the direct targeting of KRAS for cancer therapeutics.

K-ras gene mutation analysis to diagnosis pancreatic adenocarcinoma from endoscopic ultrasound-guided tissue acquisition; a systematic review and meta-analysis.

BACKGROUND: Endoscopic ultrasound-guided tissue acquisition (EUS-TA) has high sensitivity for the pathological diagnosis of pancreatic masses, but also a high false-negative rate. K-ras gene mutations occur in over 75 % of pancreatic ductal adenocarcinomas (PDAC), and this meta-analysis evaluated the utility of detecting K-ras gene mutations from EUS-TA specimens for the diagnosis of PDAC. METHODS: Relevant studies in PubMed, the Cochrane Library, and Web of Science were systematically searched. Meta-analysis was performed on data from the selected studies using a bivariate model to provide pooled values of sensitivity, specificity, and their 95 % confidence intervals (CIs). RESULTS: This meta-analysis included 1521 patients (from 10 eligible studies) who underwent EUS-TA with K-ras gene mutation analysis for diagnosis of pancreatic solid masses. The pooled estimates of sensitivity and specificity were 76.6 % (95 % CI, 70.9-81.5 %) and 97.0 % (95 % CI, 94.0-98.5 %), respectively, for pathological diagnosis, 75.9 % (95 % CI 69.5-81.4 %) and 95.3 % (95 % CI, 92.3-97.2 %) for K-ras gene mutation analysis, and 88.7 % (95 % CI 87.1-91.7 %) and 94.9 % (95 % CI, 91.5-97.0 %) for pathological diagnosis in combination with K-ras gene mutation analysis. The sensitivity for diagnosis of PDAC was significantly higher for pathological diagnosis in combination with K-ras gene mutation analysis than for pathological diagnosis or K-ras gene mutation analysis alone (both, p < 0.001). There was no difference in specificity between pathological diagnosis in combination with K-ras gene mutation analysis and both either (p = 0.234, 0.945, respectively). CONCLUSIONS: K-ras gene mutation analysis in combination with to pathological diagnosis of EUS-TA increases the accuracy of differential diagnosis of PDAC.

Conditional Overall Survival After Diagnosis of Non-Metastatic Colon Cancer: Impact of Laterality, MSI, and KRAS Status.

BACKGROUND: The prognostic relevance of laterality, microsatellite instability (MSI), and KRAS status in colon cancer has been established. However, their effect on conditional overall survival (COS) remains unknown. METHODS: COS is the probability of surviving additional years after a time from diagnosis. The National Cancer Database (2010-2017) was queried for adults with non-metastatic colon cancer and known mutation status undergoing curative resection. COS was investigated at 2 years. RESULTS: Of 4838 patients, 3716 survived at least 2 years: 15% had stage I, 38% stage II, and 46% stage III disease. Fifty-nine percent had a right-sided tumor, 16% were MSI-high, and 37% were mutated KRAS (mKRAS). The proportion of patients alive at 2 years was higher for stage I compared with stage II and III (65 vs. 61 vs. 54%). The 5-year overall survival for stage I-III was 80, 76, and 67% for the initial cohort, and 90, 88, and 86% for those alive at 2 years. After adjustment, higher pathologic T and N stage, tumor deposits, and no chemotherapy were associated with worse COS (p < 0.01). While laterality and MSI status were not associated with COS, mKRAS was independently associated with decreased COS (HR 1.35, 95% CI 1.12-1.62). CONCLUSION: Patients with mKRAS had worse COS, suggesting that these mutations confer an aggressive biologic behavior, with patients remaining at higher risk of death 2 years after diagnosis. Routine evaluation of KRAS status should be considered in patients with non-metastatic disease for prognostication and to identify those who might benefit from modified surveillance protocols.

Structural insights into the complex of oncogenic KRas4BG12V and Rgl2, a RalA/B activator.

About a quarter of total human cancers carry mutations in Ras isoforms. Accumulating evidence suggests that small GTPases, RalA, and RalB, and their activators, Ral guanine nucleotide exchange factors (RalGEFs), play an essential role in oncogenic Ras-induced signalling. We studied the interaction between human KRas4B and the Ras association (RA) domain of Rgl2 (Rgl2RA), one of the RA-containing RalGEFs. We show that the G12V oncogenic KRas4B mutation changes the interaction kinetics with Rgl2RA The crystal structure of the KRas4BG12V: Rgl2RA complex shows a 2:2 heterotetramer where the switch I and switch II regions of each KRasG12V interact with both Rgl2RA molecules. This structural arrangement is highly similar to the HRasE31K:RALGDSRA crystal structure and is distinct from the well-characterised Ras:Raf complex. Interestingly, the G12V mutation was found at the dimer interface of KRas4BG12V with its partner. Our study reveals a potentially distinct mode of Ras:effector complex formation by RalGEFs and offers a possible mechanistic explanation for how the oncogenic KRas4BG12V hyperactivates the RalA/B pathway.

The diagnosis and treatment for primary cardiac angiosarcoma with N-ras gene mutation and MSI-L: A case report and review of the literature.

RATIONALE: Primary cardiac angiosarcomas (PCA) is a rare malignancy with a poor prognosis. Currently, there is no standard treatment protocol for the PCA. We report a case of PCA in a 51-year-old woman. PATIENT CONCERNS: A 51-year-old woman initially presented with unexplained palpitations and chest tightness accompanied by nausea and vomiting, which worsened after activity and improved after rest. After symptomatic treatment, the symptoms improved, and the above symptoms recurred 8 months later. DIAGNOSES: Positron emission tomography-computed tomography revealed multiple lung nodules of varying sizes, some of which exhibited increased glucose metabolism. Furthermore, a soft tissue mass protruding into the pericardial cavity and involving the adjacent right atrium was observed in the right pericardium. The mass exhibited increased glucose metabolism, suggestive of a pericardial tumor with multiple lung metastases. Finally, histopathologic diagnosis of metastatic angiosarcoma was done by computed tomography-guided percutaneous lung and mediastinal biopsy. INTERVENTIONS: The patient was treated with palliative chemotherapy for the primary cardiac angiosarcomas and hematogenous lung metastasis. One cycle later, the result of Next-Generation Sequencing showed that the microsatellite instability status was determined to be low-level. Based on this result, tislelizumab was added to the original chemotherapy regimen. OUTCOMES: Unfortunately, the patient with PCA passed away after only 2 cycles of chemotherapy, and the cause of death remained unknown. LESSONS: This case report well demonstrates typical imaging findings of a rare cardiac angiosarcomas and emphasizes importance of early investigation for accurate diagnosis and proper management of the cardiac angiosarcomas.

A pan-cancer analysis implicates human NKIRAS1 as a tumor-suppressor gene.

The NF-κB family of transcription factors and the Ras family of small GTPases are important mediators of proproliferative signaling that drives tumorigenesis and carcinogenesis. The κB-Ras proteins were previously shown to inhibit both NF-κB and Ras activation through independent mechanisms, implicating them as tumor suppressors with potentially broad relevance to human cancers. In this study, we have used two mouse models to establish the relevance of the κB-Ras proteins for tumorigenesis. Additionally, we have utilized a pan-cancer bioinformatics analysis to explore the role of the κB-Ras proteins in human cancers. Surprisingly, we find that the genes encoding κB-Ras 1 (NKIRAS1) and κB-Ras 2 (NKIRAS2) are rarely down-regulated in tumor samples with oncogenic Ras mutations. Reduced expression of human NKIRAS1 alone is associated with worse prognosis in at least four cancer types and linked to a network of genes implicated in tumorigenesis. Our findings provide direct evidence that loss of NKIRAS1 in human tumors that do not carry oncogenic RAS mutations is associated with worse clinical outcomes.

Runx3 Restoration Regresses K-Ras-Activated Mouse Lung Cancers and Inhibits Recurrence.

Oncogenic K-RAS mutations occur in approximately 25% of human lung cancers and are most frequently found in codon 12 (G12C, G12V, and G12D). Mutated K-RAS inhibitors have shown beneficial results in many patients; however, the inhibitors specifically target K-RASG12C and acquired resistance is a common occurrence. Therefore, new treatments targeting all kinds of oncogenic K-RAS mutations with a durable response are needed. RUNX3 acts as a pioneer factor of the restriction (R)-point, which is critical for the life and death of cells. RUNX3 is inactivated in most K-RAS-activated mouse and human lung cancers. Deletion of mouse lung Runx3 induces adenomas (ADs) and facilitates the development of K-Ras-activated adenocarcinomas (ADCs). In this study, conditional restoration of Runx3 in an established K-Ras-activated mouse lung cancer model regressed both ADs and ADCs and suppressed cancer recurrence, markedly increasing mouse survival. Runx3 restoration suppressed K-Ras-activated lung cancer mainly through Arf-p53 pathway-mediated apoptosis and partly through p53-independent inhibition of proliferation. This study provides in vivo evidence supporting RUNX3 as a therapeutic tool for the treatment of K-RAS-activated lung cancers with a durable response.

Mechanism-Based Redesign of GAP to Activate Oncogenic Ras.

Ras GTPases play a crucial role in cell signaling pathways. Mutations of the Ras gene occur in about one third of cancerous cell lines and are often associated with detrimental clinical prognosis. Hot spot residues Gly12, Gly13, and Gln61 cover 97% of oncogenic mutations, which impair the enzymatic activity in Ras. Using QM/MM free energy calculations, we present a two-step mechanism for the GTP hydrolysis catalyzed by the wild-type Ras.GAP complex. We found that the deprotonation of the catalytic water takes place via the Gln61 as a transient Brønsted base. We also determined the reaction profiles for key oncogenic Ras mutants G12D and G12C using QM/MM minimizations, matching the experimentally observed loss of catalytic activity, thereby validating our reaction mechanism. Using the optimized reaction paths, we devised a fast and accurate procedure to design GAP mutants that activate G12D Ras. We replaced GAP residues near the active site and determined the activation barrier for 190 single mutants. We furthermore built a machine learning for ultrafast screening, by fast prediction of the barrier heights, tested both on the single and double mutations. This work demonstrates that fast and accurate screening can be accomplished via QM/MM reaction path optimizations to design protein sequences with increased catalytic activity. Several GAP mutations are predicted to re-enable catalysis in oncogenic G12D, offering a promising avenue to overcome aberrant Ras-driven signal transduction by activating enzymatic activity instead of inhibition. The outlined computational screening protocol is readily applicable for designing ligands and cofactors analogously.

KRASG12D inhibition in pancreatic cancer: Fas expression facilitates immune clearance.

In an article in this issue of Developmental Cell and in a second paper in Cancer Cell, Mahadevan et al. demonstrate that KrasG12D suppression remodels the immunosuppressive microenvironment of KrasG12D pancreatic cancers, recruits activated CD8+ cytotoxic T cells, and epigenetically upregulates Fas expression in cancer cells, leading to tumor clearance via Fas/FasL-mediated apoptosis.

CRISPR-mediated reversion of oncogenic KRAS mutation results in increased proliferation and reveals independent roles of Ras and mTORC2 in the migration of A549 lung cancer cells.

Although the RAS oncogene has been extensively studied, new aspects concerning its role and regulation in normal biology and cancer continue to be discovered. Recently, others and we have shown that the mechanistic Target of Rapamycin Complex 2 (mTORC2) is a Ras effector in Dictyostelium and mammalian cells. mTORC2 plays evolutionarily conserved roles in cell survival and migration and has been linked to tumorigenesis. Because RAS is often mutated in lung cancer, we investigated whether a Ras-mTORC2 pathway contributes to enhancing the migration of lung cancer cells expressing oncogenic Ras. We used A549 cells and CRISPR/Cas9 to revert the cells' KRAS G12S mutation to wild-type and establish A549 revertant (REV) cell lines, which we then used to evaluate the Ras-mediated regulation of mTORC2 and cell migration. Interestingly, our results suggest that K-Ras and mTORC2 promote A549 cell migration but as part of different pathways and independently of Ras's mutational status. Moreover, further characterization of the A549REV cells revealed that loss of mutant K-Ras expression for the wild-type protein leads to an increase in cell growth and proliferation, suggesting that the A549 cells have low KRAS-mutant dependency and that recovering expression of wild-type K-Ras protein increases these cells tumorigenic potential.