Prevalence of KRAS amplification in patients with metastatic cancer: Real-world next-generation sequencing analysis.

BACKGROUND: The Kirsten rat sarcoma virus (KRAS) is a prominent proto-oncogene. Several treatments for KRAS mutations have been developed. However, KRAS amplification, a KRAS alteration, is poorly understood, and there is currently no appropriate treatment other than conventional chemotherapy. This study aimed to elucidate the role of KRAS amplification in different types of cancers. METHODS: From October 2019 to June 2023, we performed next-generation sequencing using Trusight Oncology 500 on 3895 patients with 37 different cancer types at the Samsung Medical Center. We analyzed the distribution of KRAS amplification according to cancer type and its correlation with tumor mutation burden (TMB). Concomitant KRAS mutations were also identified. RESULTS: Of the total 3895 patients, 99 (2.5 %) had KRAS amplification. The highest frequency of KRAS amplification was detected in 2 % (27/1350) of patients with colorectal cancer, followed by 3.48 % (32/920) of patients with gastric cancer and 3.88 % (9/232) patients with of pancreatic cancer. MSI-High was not detected in patients with KRAS amplification. There was no correlation between KRAS copy number variation and TMB status. Among patients with KRAS amplification, 27.3 % (27/99) had a concomitant KRAS mutation. More than 50 % of patients had G12D or G12V mutations. In gastric cancer, patients with both KRAS amplification and mutation were extremely rare at 3.1 % (1/32); however, in colorectal cancer, more than half of the patients had KRAS amplification and mutation (51.9 %, 14/27). KRAS amplification and mutations are associated with mutations in tumor suppressor genes TP53, BRCA2, ARID1B, and PTCH1. CONCLUSIONS: Of the 3895 patients with metastatic solid tumors, 99 (2.5 %) had KRAS amplification, and next-generation sequencing analysis provided a deeper understanding of KRAS amplification.

CHNet: A multi-task global-local Collaborative Hybrid Network for KRAS mutation status prediction in colorectal cancer.

Accurate prediction of Kirsten rat sarcoma (KRAS) mutation status is crucial for personalized treatment of advanced colorectal cancer patients. However, despite the excellent performance of deep learning models in certain aspects, they often overlook the synergistic promotion among multiple tasks and the consideration of both global and local information, which can significantly reduce prediction accuracy. To address these issues, this paper proposes an innovative method called the Multi-task Global-Local Collaborative Hybrid Network (CHNet) aimed at more accurately predicting patients' KRAS mutation status. CHNet consists of two branches that can extract global and local features from segmentation and classification tasks, respectively, and exchange complementary information to collaborate in executing these tasks. Within the two branches, we have designed a Channel-wise Hybrid Transformer (CHT) and a Spatial-wise Hybrid Transformer (SHT). These transformers integrate the advantages of both Transformer and CNN, employing cascaded hybrid attention and convolution to capture global and local information from the two tasks. Additionally, we have created an Adaptive Collaborative Attention (ACA) module to facilitate the collaborative fusion of segmentation and classification features through guidance. Furthermore, we introduce a novel Class Activation Map (CAM) loss to encourage CHNet to learn complementary information between the two tasks. We evaluate CHNet on the T2-weighted MRI dataset, and achieve an accuracy of 88.93% in KRAS mutation status prediction, which outperforms the performance of representative KRAS mutation status prediction methods. The results suggest that our CHNet can more accurately predict KRAS mutation status in patients via a multi-task collaborative facilitation and considering global-local information way, which can assist doctors in formulating more personalized treatment strategies for patients.

Driver mutation subtypes involve with differentiated immunophenotypes influencing pancreatic cancer outcomes.

Despite many studies focusing on the prognostic biomarkers in pancreatic adenocarcinomas (PAADs), there is ill-informed about the relationships between their genomic features and immune characteristics. Herein, we deeply investigated the involvement of major driver mutation subtypes with immunophenotypes impacting PAAD outcomes. Based on public data analyses of RNA expression-based immune subtypes in PAAD, in contrast to KRAS G12D & TP53 co-mutant patients with poor outcomes, the best immune subtype C3 (inflammatory) characterized by high Th1/Th2 ratio was relatively enriched in KRASnon-G12DTP53wt patients with better survival, whereas the inferior subtype C2 (IFN-γ dominant) with low Th1/Th2 ratio was more common in the former than in the latter. Moreover, contrary to the highly immunosuppressive microenvironment (high Treg, high ratio of Treg to tumor-specific CD4+ T cell) in KRASG12DTP53mut patients, KRASG12VTP53wt individuals exhibited an inflamed context profiled by multiplex immunohistochemistry. It could be responsible for their outstanding survival advantage over others in postsurgical PAAD patients receiving adjuvant chemotherapy as shown by our cohort. Together, KRASG12VTP53wt may be a promising biomarker for prognostic evaluation and screening certain candidates with PAAD to get desirable survival benefit from adjuvant chemotherapy.

Beyond tobacco: genomic disparities in lung cancer between smokers and never-smokers.

BACKGROUND: Tobacco use is one of the main risk factors for Lung Cancer (LC) development. However, about 10-20% of those diagnosed with the disease are never-smokers. For Non-Small Cell Lung Cancer (NSCLC) there are clear differences in both the clinical presentation and the tumor genomic profiles between smokers and never-smokers. For example, the Lung Adenocarcinoma (LUAD) histological subtype in never-smokers is predominately found in young women of European, North American, and Asian descent. While the clinical presentation and tumor genomic profiles of smokers have been widely examined, never-smokers are usually underrepresented, especially those of a Latin American (LA) background. In this work, we characterize, for the first time, the difference in the genomic profiles between smokers and never-smokers LC patients from Chile. METHODS: We conduct a comparison by smoking status in the frequencies of genomic alterations (GAs) including somatic mutations and structural variants (fusions) in a total of 10 clinically relevant genes, including the eight most common actionable genes for LC (EGFR, KRAS, ALK, MET, BRAF, RET, ERBB2, and ROS1) and two established driver genes for malignancies other than LC (PIK3CA and MAP2K1). Study participants were grouped as either smokers (current and former, n = 473) or never-smokers (n = 200) according to self-report tobacco use at enrollment. RESULTS: Our findings indicate a higher overall GA frequency for never-smokers compared to smokers (58 vs. 45.7, p-value < 0.01) with the genes EGFR, KRAS, and PIK3CA displaying the highest prevalence while ERBB2, RET, and ROS1 the lowest. Never-smokers present higher frequencies in seven out of the 10 genes; however, smokers harbor a more complex genomic profile. The clearest differences between groups are seen for EGFR (15.6 vs. 21.5, p-value: < 0.01), PIK3CA (6.8 vs 9.5) and ALK (3.2 vs 7.5) in favor of never-smokers, and KRAS (16.3 vs. 11.5) and MAP2K1 (6.6 vs. 3.5) in favor of smokers. Alterations in these genes are comprised almost exclusively by somatic mutations in EGFR and mainly by fusions in ALK, and only by mutations in PIK3CA, KRAS and MAP2K1. CONCLUSIONS: We found clear differences in the genomic landscape by smoking status in LUAD patients from Chile, with potential implications for clinical management in these limited-resource settings.

Efficacy of first-line immune checkpoint inhibitor and anti-angiogenic agent combination therapy for Kirsten rat sarcoma viral antigen-mutant advanced non-small-cell lung cancer: a systematic review and network meta-analysis.

BACKGROUND: Recent advancements in advanced non-small-cell lung cancer (NSCLC) treatment have significantly improved primary therapy outcomes owing to the emergence of various molecular targeted therapies and immune checkpoint inhibitors (ICIs). However, for Kirsten rat sarcoma viral antigen (KRAS) mutations, molecular targeted drugs, such as sotorasib, are not applicable as first-line treatments, and the optimal primary treatment remains unclear. Therefore, we aimed to investigate the efficacy of ICI combination therapy as first-line treatment for KRAS-mutant NSCLC. METHODS: We conducted a systematic search for phase 3 randomized controlled trials (RCTs) that presented data on KRAS mutation status in advanced NSCLC. The primary endpoints were progression-free survival (PFS) and overall survival (OS). A random-effects network meta-analysis was conducted to perform direct and indirect comparisons among treatment groups. RESULTS: Six RCTs were eligible for inclusion. In the network meta-analysis for KRAS-mutant NSCLC, Chemo + bevacizumab (Bev) + ICI was associated with improved PFS (hazard ratio [HR] 0.38, 95% confidence interval [CI] 0.22-0.64), followed by Chemo + ICI + ICI (HR 0.66, 95% CI 0.47-0.93) and Chemo + ICI (HR 0.67, 95% CI 0.49-0.91). The most beneficial effect on OS was observed with Chemo + Bev + ICI (HR 0.50, 95% CI 0.34-0.73), followed by Chemo + ICI + ICI (HR 0.64, 95% CI 0.48-0.87) and Chemo + ICI (HR 0.72, 95% CI 0.56-0.92). Regarding OS in wild-type KRAS, ICI + ICI (HR 0.73, 95% CI 0.50-1.07) produced the most favorable effects, followed by Chemo + ICI (HR 0.79, 95% CI 0.63-0.99). CONCLUSION: The efficacy of Chemo + Bev + ICI is potentially high for improving PFS and OS in KRAS-mutant NSCLC. In advanced NSCLC, the presence or absence of KRAS mutations may need to be considered when administering first-line treatment.

Molecular testing for personalized therapy is underutilized in patients with borderline resectable and locally advanced pancreatic cancer - real world data from the NORPACT-2 study.

Background: International guidelines currently recommend the use of molecular testing in patients with advanced pancreatic cancer. The rate of actionable molecular alterations is low. The utility of molecular testing in patients with borderline resectable (BRPC) or locally advanced (LAPC) pancreatic cancer in real world clinical practice is unclear.Methods: 188 consecutive patients included in a prospective, population-based study (NORPACT-2) in patients with BRPC and LAPC (2018-2020) were reviewed. Molecular testing was performed at the discretion of the treating oncologist and was not recommended as a routine investigation by the national guidelines. All patients were considered fit to undergo primary chemotherapy and potential surgical resection. The frequency and the results of molecular testing (microsatellite instability (MSI) and/or KRAS status) were assessed.Results: Thirty patients (16%) underwent molecular testing. MSI tumour was detected in one (3.6%) of 28 tested patients. The patient received immunotherapy and subsequently underwent surgical resection. Histological assessment of the resected specimen revealed a complete response. KRAS wild type was detected in one (14.3%) of seven tested patient. Patients who initiated FOLFIRINOX as the primary chemotherapy regimen (p = 0.022), or were being treated at one of the eight hospital trusts (p = 0.001) were more likely to undergo molecular testing.Conclusions: Molecular testing was rarely performed in patients with BRPC or LAPC. Routine molecular testing for all patients with BRPC and LAPC should be considered to increase identification of targetable mutations and improve outcomes.

BRAF-mutant microsatellite-stable rectal cancer with acquired KRAS mutation leading to drug resistance in liver metastasis.

BRAF-mutant microsatellite-stable colorectal cancer (CRC), metastasized to distant sites, is associated with a poor prognosis. However, the BEACON CRC regimen, comprising a BRAF inhibitor, MEK inhibitor, and anti-EGFR antibody, offered a prolonged prognosis. Nonetheless, resistance to this regimen may occur, as observed in our reported case of CRC, where a KRAS mutation was identified in addition to the BRAF V600E mutation. Here, we present a case of 74-year-old woman with rectal cancer (pT4bN1bM0 Stage IIIc) harboring the BRAF V600E mutation. After resection of the primary tumor and during adjuvant chemotherapy using CAPOX (capecitabine and oxaliplatin), liver and lung metastases became apparent, and a companion diagnosis test revealed the presence of a BRAF V600E mutation. The new lesions were deemed resistant to the CAPOX regimen, and we decided to introduce encorafenib and cetuximab. After resection of liver metastases, encorafenib and cetuximab were reintroduced, but a new lesion appeared in hepatic S7, indicating resistance to the encorafenib and cetuximab regimen. The resistant liver metastasis was subsequently resected. To elucidate the resistance mechanism, we conducted a comprehensive analysis using the FoundationOne CDx cancer gene panel test, revealing the presence of a KRAS Q61H mutation alongside the BRAF V600E mutation. Subsequent liquid biopsy after liver recurrence confirmed the persistence of the KRAS Q61H mutation. Our results highlight the significance of cancer genome profiling tests (CGP tests) and liquid biopsies in guiding treatment strategies for BRAF-mutant colorectal cancer. Therefore, CGP testing offers valuable information for treatment, even if it does not lead to new drug administrations.

A case report of high-grade fetal lung adenocarcinoma with KRAS mutation.

Fetal lung adenocarcinoma (FLAC) is a rare malignant tumor with a relatively good prognosis, and the probability of mutation with KRAS is very low. We report a middle-aged female patient with FLAC with KRAS mutation. The primary lesion was implanted with radioactive iodine 125 particles, and the lesion was smaller than before. However, the metastatic lesions progressed rapidly. After chemotherapy with pemetrexed disodium and cisplatin combined with bevacizumab to prevent angiogenesis, the primary lesions continued to shrink, and the metastatic lesions were significantly smaller than before. The patient has been followed up for 5 months and is generally in good condition. We report a case of H-FLAC with KRAS mutation, and its development and prognosis seem to be significantly abnormal from that of ordinary H-FLAC. It also provides a possible effective treatment for unresectable H-FLAC, but further research is needed.

Role of molecular biology in the management of pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) presents significant challenges in patient management due to a dismal prognosis, increasing incidence, and limited treatment options. In this regard, precision medicine, which personalizes treatments based on tumour molecular characteristics, has gained great interest. However, its widespread implementation is not fully endorsed in current recommendations. This review explores key molecular alterations in PDAC, while emphasizing differences between KRAS-mutated and KRAS-wild-type tumours. It assesses the practical application of precision medicine in clinical settings and outlines potential future directions with respect to PDAC. Actionable molecular targets are examined with the aim of enhancing our understanding of PDAC molecular biology. Insights from this analysis may contribute to a more refined and personalized approach to pancreatic cancer treatment, ultimately improving patient outcomes.

The value of protein allostery in rational anticancer drug design: an update.

INTRODUCTION: Allosteric drugs are advantageous. However, they still face hurdles, including identification of allosteric sites that will effectively alter the active site. Current strategies largely focus on identifying pockets away from the active sites into which the allosteric ligand will dock and do not account for exactly how the active site is altered. Favorable allosteric inhibitors dock into sites that are nearby the active sites and follow nature, mimicking diverse allosteric regulation strategies. AREAS COVERED: The following article underscores the immense significance of allostery in drug design, describes current allosteric strategies, and especially offers a direction going forward. The article concludes with the authors' expert perspectives on the subject. EXPERT OPINION: To select a productive venue in allosteric inhibitor development, we should learn from nature. Currently, useful strategies follow this route. Consider, for example, the mechanisms exploited in relieving autoinhibition and in harnessing allosteric degraders. Mimicking compensatory, or rescue mutations may also fall into such a thesis, as can molecular glues that capture features of scaffolding proteins. Capturing nature and creatively tailoring its mimicry can continue to innovate allosteric drug discovery.

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-ß1 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, TGFß, 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.

Pathogenesis of Endometriosis and Endometriosis-Associated Cancers.

Endometriosis is a hormone-dependent, chronic inflammatory condition that affects 5-10% of reproductive-aged women. It is a complex disorder characterized by the growth of endometrial-like tissue outside the uterus, which can cause chronic pelvic pain and infertility. Despite its prevalence, the underlying molecular mechanisms of this disease remain poorly understood. Current treatment options are limited and focus mainly on suppressing lesion activity rather than eliminating it entirely. Although endometriosis is generally considered a benign condition, substantial evidence suggests that it increases the risk of developing specific subtypes of ovarian cancer. The discovery of cancer driver mutations in endometriotic lesions indicates that endometriosis may share molecular pathways with cancer. Moreover, the application of single-cell and spatial genomics, along with the development of organoid models, has started to illuminate the molecular mechanisms underlying disease etiology. This review aims to summarize the key genetic mutations and alterations that drive the development and progression of endometriosis to malignancy. We also review the significant recent advances in the understanding of the molecular basis of the disorder, as well as novel approaches and in vitro models that offer new avenues for improving our understanding of disease pathology and for developing new targeted therapies.

A Critical Review of the Impact of SMARCA4 Mutations on Survival Outcomes in Non-Small Cell Lung Cancer.

This critical review investigates the impact of SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily A, member 4 (SMARCA4) mutations on survival outcomes in non-small cell lung cancer (NSCLC) through an analysis of 21 peer-reviewed articles. Survival analyses across this review demonstrated consistently worse outcomes for SMARCA4-mutated vs. SMARCA4 wild-type NSCLC patients, specifically emphasizing class 1 truncating mutations as an independent factor for poor overall survival. In addition, this review explores the clinicopathologic characteristics of SMARCA4 mutations and their impact on various treatment modalities, including immune checkpoint inhibitors (ICIs) both with and without Kirsten rat sarcoma viral oncogene homolog (KRAS) co-mutations. The potential ineffectiveness of ICI treatment in NSCLC is explored through the impact of SMARCA4/KRAS co-mutations on the tumor microenvironment. Moreover, this NSCLC review consistently reported statistically worse overall survival outcomes for SMARCA4/KRAS co-mutations than SMARCA4 wild-type/KRAS-mutated cohorts, extending across ICIs, chemo-immunotherapy (CIT), and KRAS G12C inhibitors. Designing prospective clinical SMARCA4-mutated or SMARCA4/KRAS co-mutated NSCLC trials to evaluate targeted therapies and immunotherapy may lead to a better understanding of how to improve cancer patients' outcomes and survival rates.

Dynamics of RAS Mutations in Liquid Biopsies in Metastatic Colorectal Cancer Patients-Case Series and Literature Review.

Liquid biopsies can accurately identify molecular alterations in patients with colorectal cancer with high concordance with tissue analysis and shorter turnaround times. Circulating tumor (ct) DNA analysis can be used for diagnosing and monitoring tumor evolution in patients with metastatic colorectal cancer who are treated with EGFR inhibitors. In this article, we reported three clinical cases to illustrate the relevance of RAS mutations identified in ctDNA samples of patients with wild-type metastatic colorectal cancer who received an EGFR inhibitor plus chemotherapy as first-line treatment. The identification of RAS mutations in these patients is one of the most frequently identified mechanisms of acquired resistance. However, detecting a KRAS mutation via liquid biopsy can be caused by inter-tumor heterogeneity or it can be a false positive due to clonal hematopoiesis. More research is needed to determine whether ctDNA monitoring may help guide therapy options in metastatic colorectal cancer patients. We performed a literature review to assess the technologies that are used for analysis of RAS mutations on ctDNA, the degree of agreement between tissue and plasma and the importance of tissue/plasma discordant cases.

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.

MCT1-dependent lactate recycling is a metabolic vulnerability in colorectal cancer cells upon acquired resistance to anti-EGFR targeted therapy.

Despite the implementation of personalized medicine, patients with metastatic CRC (mCRC) still have a dismal overall survival due to the frequent occurrence of acquired resistance mechanisms thereby leading to clinical relapse. Understanding molecular mechanisms that support acquired resistance to anti-EGFR targeted therapy in mCRC is therefore clinically relevant and key to improving patient outcomes. Here, we observe distinct metabolic changes between cetuximab-resistant CRC cell populations, with in particular an increased glycolytic activity in KRAS-mutant cetuximab-resistant CRC cells (LIM1215 and OXCO2) but not in KRAS-amplified resistant DiFi cells. We show that cetuximab-resistant LIM1215 and OXCO2 cells have the capacity to recycle glycolysis-derived lactate to sustain their growth capacity. This is associated with an upregulation of the lactate importer MCT1 at both transcript and protein levels. Pharmacological inhibition of MCT1, with AR-C155858, reduces the uptake and oxidation of lactate and impairs growth capacity in cetuximab-resistant LIM1215 cells both in vitro and in vivo. This study identifies MCT1-dependent lactate utilization as a clinically actionable, metabolic vulnerability to overcome KRAS-mutant-mediated acquired resistance to anti-EGFR therapy in CRC.

Assessment of KRASG12C inhibitors for colorectal cancer.

Colorectal cancer (CRC) is a highly prevalent and lethal cancer worldwide. Approximately 45% of CRC patients harbor a gain-in-function mutation in KRAS. KRAS is the most frequently mutated oncogene accounting for approximately 25% of all human cancers. Gene mutations in KRAS cause constitutive activation of the KRAS protein and MAPK/AKT signaling, resulting in unregulated proliferation and survival of cancer cells and other aspects of malignant transformation, progression, and metastasis. While KRAS has long been considered undruggable, the FDA recently approved two direct acting KRAS inhibitors, Sotorasib and Adagrasib, that covalently bind and inactivate KRASG12C. Both drugs showed efficacy for patients with non-small cell lung cancer (NSCLC) diagnosed with a KRASG12C mutation, but for reasons not well understood, were considerably less efficacious for CRC patients diagnosed with the same mutation. Thus, it is imperative to understand the basis for resistance to KRASG12C inhibitors, which will likely be the same limitations for other mutant specific KRAS inhibitors in development. This review provides an update on clinical trials involving CRC patients treated with KRASG12C inhibitors as a monotherapy or combined with other drugs. Mechanisms that contribute to resistance to KRASG12C inhibitors and the development of novel RAS inhibitors with potential to escape such mechanisms of resistance are also discussed.

Dual inhibition of SUMOylation and MEK conquers MYC-expressing KRAS-mutant cancers by accumulating DNA damage.

BACKGROUND: KRAS mutations frequently occur in cancers, particularly pancreatic ductal adenocarcinoma, colorectal cancer, and non-small cell lung cancer. Although KRASG12C inhibitors have recently been approved, effective precision therapies have not yet been established for all KRAS-mutant cancers. Many treatments for KRAS-mutant cancers, including epigenome-targeted drugs, are currently under investigation. Small ubiquitin-like modifier (SUMO) proteins are a family of small proteins covalently attached to and detached from other proteins in cells via the processes called SUMOylation and de-SUMOylation. We assessed whether SUMOylation inhibition was effective in KRAS-mutant cancer cells. METHODS: The efficacy of the first-in-class SUMO-activating enzyme E inhibitor TAK-981 (subasumstat) was assessed in multiple human and mouse KRAS-mutated cancer cell lines. A gene expression assay using a TaqMan array was used to identify biomarkers of TAK-981 efficacy. The biological roles of SUMOylation inhibition and subsequent regulatory mechanisms were investigated using immunoblot analysis, immunofluorescence assays, and mouse models. RESULTS: We discovered that TAK-981 downregulated the expression of the currently undruggable MYC and effectively suppressed the growth of MYC-expressing KRAS-mutant cancers across different tissue types. Moreover, TAK-981-resistant cells were sensitized to SUMOylation inhibition via MYC-overexpression. TAK-981 induced proteasomal degradation of MYC by altering the balance between SUMOylation and ubiquitination and promoting the binding of MYC and Fbxw7, a key factor in the ubiquitin-proteasome system. The efficacy of TAK-981 monotherapy in immunocompetent and immunodeficient mouse models using a mouse-derived CMT167 cell line was significant but modest. Since MAPK inhibition of the KRAS downstream pathway is crucial in KRAS-mutant cancer, we expected that co-inhibition of SUMOylation and MEK might be a good option. Surprisingly, combination treatment with TAK-981 and trametinib dramatically induced apoptosis in multiple cell lines and gene-engineered mouse-derived organoids. Moreover, combination therapy resulted in long-term tumor regression in mouse models using cell lines of different tissue types. Finally, we revealed that combination therapy complementally inhibited Rad51 and BRCA1 and accumulated DNA damage. CONCLUSIONS: We found that MYC downregulation occurred via SUMOylation inhibition in KRAS-mutant cancer cells. Our findings indicate that dual inhibition of SUMOylation and MEK may be a promising treatment for MYC-expressing KRAS-mutant cancers by enhancing DNA damage accumulation.

Tunneling nanotubes mediate KRas transport: Inducing tumor heterogeneity and altering cellular membrane mechanical properties.

Mutation in oncogene KRas plays a crucial role in the occurrence and progression of numerous malignant tumors. Malignancy involves changes in cell mechanics for extensive cellular deformation during metastatic dissemination. We hypothesize that oncogene KRas mutations are intrinsic to alterations in cellular mechanics that promote malignant tumor generation and progression. Here, we demonstrate the use of optical tweezers coupled with a confocal fluorescence imaging system and gene interference technique to reveal that the mutant KRas protein can be transported between homogeneous and heterogeneous tumor cells by tunneling nanotubes (TNTs), resulting in a significant reduction of membrane tension and acceleration of membrane phospholipid flow in the recipient cells. Simultaneously, the changes in membrane mechanical properties of the tumor cells also enhance the metastatic and invasive ability of the tumors, which further contribute to the deterioration of the tumors. This finding helps to clarify the association between oncogene mutations and changes in the mechanical properties of tumor cells, which provides a theoretical basis for the development of cancer treatment strategies. STATEMENT OF SIGNIFICANCE: Here, we present a laser confocal fluorescence system integrated with optical tweezers to observe the transfer of mutant KRasG12D protein from mutant cells to wild-type cells through TNTs. Malignancy involves changes in cell mechanics for extensive cellular deformation during metastatic dissemination. Our results demonstrate a significant decrease in membrane tension and an increase in membrane phospholipid flow in recipient cells. These alterations in mechanical properties augment the migration and invasive capabilities of tumor cells, contributing to tumor malignancy. Our findings propose that cellular mechanical properties could serve as new markers for tumor development, and targeting membrane tension may hold potential as a therapeutic strategy.