MEK Inhibitor Research Articles

MYC Overexpression Enhances Sensitivity to MEK Inhibition in Head and Neck Squamous Cell Carcinoma.

MEK inhibitors, such as trametinib, have shown therapeutic potential in head and neck squamous cell carcinoma (HNSCC). However, the factors influencing cancer cell sensitivity and resistance to MEK inhibition remain poorly understood. In our study, we observed that MEK inhibition significantly reduced the expression of MYC, a transcription factor critical for the therapeutic response. MYC overexpression markedly enhanced the sensitivity of HNSCC cells to trametinib, as evidenced by delayed wound healing and reduced colony formation. Cell cycle analysis revealed that trametinib induced a G1 phase arrest, whereas MYC overexpression accelerated cell cycle progression, with a reduced induction of p27 and p21 and diminished decreases in E2F1 and phospho-Ser2/5 levels. Flow cytometry and protein analyses demonstrated that MYC overexpression amplified trametinib-induced apoptosis and DNA damage, as evidenced by elevated levels of pro-apoptotic markers (p53, cleaved PARP, and BIM) and γH2AX. In vivo xenograft models confirmed these findings, showing increased sensitivity to trametinib in MYC-overexpressing tumors. Moreover, MEK inhibition increased autophagy in HNSCC cells, a factor critical for therapeutic resistance. Inhibiting trametinib-induced autophagy further enhanced apoptotic cell death. These findings suggest that MYC expression and autophagy play crucial roles in HNSCC's response to MEK inhibition. Combining trametinib with autophagy inhibition may improve therapeutic outcomes in HNSCC.

Establishment and characterization of a new mouse gastric carcinoma cell line, MCC

BackgroundThe aim of this study was to establish a primary mouse gastric carcinoma cell line.MethodsGastric adenocarcinoma in the body region was induced in immunocompetent BALB/c mice using N-Methyl-N-nitrosourea and a 2% NaCl solution. Fresh gastric cancer tissue samples were cultured in 1640 medium supplemented with 10% fetal bovine serum for primary culture and subculture. Cellular morphology was assessed via light microscopy, and a cell growth curve was established. Genomic and proteomic analyses were conducted to characterize the molecular features of the cell lines. This cell line demonstrated a 100% success rate in forming subcutaneous tumors in BALB/c mice. By integrating proteomic profiles from clinical gastric cancer patients and the murine subcutaneous tumor model, several molecular targets suitable for preclinical investigation were identified. Trametinib, a MEK inhibitor, was employed as a model compound in our preclinical study.ResultsA novel gastric carcinoma cell line, designated MCC, was established from BALB/c mice. This cell line exhibited a doubling time of approximately 33 h. Genomic and proteomic analyses identified mutations frequently observed in clinical gastric cancer patients, such as Kras, Egfr, and Ccnd3. Additionally, MCC overexpresses proteins, including SLC1A5, MCM6, and ITGA2, which are significantly upregulated in gastric cancer tissues compared to adjacent non-cancerous tissues. The MCC cell line demonstrated stable tumorigenicity in immunocompetent BALB/c mice, forming subcutaneous tumors that closely resemble the proteomic profile of clinical gastric cancer samples. This high concordance facilitated the identification of several potential therapeutic targets for gastric cancer. Preclinical studies with trametinib revealed that treatment effectively inhibited gastric cancer growth, likely mediated through the activation of immune cells, particularly neutrophils and T cells.ConclusionsThe MCC cell line serves as an indispensable model for gastric cancer research, offering a robust platform for investigating tumor development and progression. Its exceptional tumorigenic capacity and strong concordance with clinical proteomic profiles underscore its significance in translational research, facilitating the discovery of novel therapeutic targets and elucidation of molecular pathways critical for developing effective treatment strategies.

BRAF and MEK inhibitors rechallenge after an adverse drug reaction in patients with cancer: A pharmacovigilance cohort study.

The safety profile of a rechallenge with BRAF inhibitors (BRAFi) or a combination of BRAF and MEK inhibitors (MEKi) following an adverse drug reaction (ADR) remains largely unexplored. To identify the reported recurrence rate of the same ADR after a BRAFi±MEKi targeted therapy (TT) rechallenge in patients with cancer and to identify factors associated with recurrence. In this observational, pharmacovigilance study, ADR reports were sourced from VigiBase, the World Health Organization database. The inclusion criteria encompassed all BRAFi cases (with or without MEKi) through September 01, 2023, irrespective of the primary cancer diagnosis. The primary outcome was the reported recurrence rate of the same initial ADR following TT rechallenge. Secondary outcomes measures included were identification of variables associated with recurrence among informative rechallenges, defined as those with known recurrence status. Out of 21,339 ADR cases linked to TT, 4771 (22.4%) reported a rechallenge, with 563 yielding informative data (11.8%). Recurrence of the initial ADR was reported in 223 cases, resulting in a reported recurrence rate of 39.6% (95% CI: 35.7-43.7). The highest recurrence rates in a rechallenge were observed for pyrexia (47%, 95% CI: 39-55), renal failure (46%, 95% CI: 32-60), and musculoskeletal disorders (44%, 95%CI: 33-56). There was no significant influence of factors such as TT regimen (either BRAFi monotherapy or any TT combination), age, sex, or the type of cancer on reported recurrence rate. In real-world settings, approximately two-fifths of cases with notified TT rechallenges led to a reporting of recurrence of the same initial ADR. The primary determinant of reported recurrence seems to be the nature of the initial ADR rather than the TT regimen, or any other baseline patient characteristic.

SILAC-based quantification reveals modulation of the immunopeptidome in BRAF and MEK inhibitor sensitive and resistant melanoma cells.

The immunopeptidome is constantly monitored by T cells to detect foreign or aberrant HLA peptides. It is highly dynamic and reflects the current cellular state, enabling the immune system to recognize abnormal cellular conditions, such as those present in cancer cells. To precisely determine how changes in cellular processes, such as those induced by drug treatment, affect the immunopeptidome, quantitative immunopeptidomics approaches are essential. To meet this need, we developed a pulsed SILAC-based method for quantitative immunopeptidomics. Metabolic labeling with lysine, arginine, and leucine enabled isotopic labeling of nearly all HLA peptides across all allotypes (> 90% on average). We established a data analysis workflow that integrates the de novo sequencing-based tool Peptide-PRISM for comprehensive HLA peptide identification with MaxQuant for accurate quantification. We employed this strategy to explore the modulation of the immunopeptidome upon MAPK pathway inhibition (MAPKi) and to investigate alterations associated with early cellular responses to inhibitor treatment and acquired resistance to MAPKi. Our analyses demonstrated significant changes in the immunopeptidome early during MAPKi treatment and in the resistant state. Moreover, we identified putative tumor-specific cryptic HLA peptides linked to these processes that might represent exploitable targets for cancer immunotherapy. We have developed a new mass spectrometric approach that allowed us to investigate the effects of common MAPK inhibitors on the immunopeptidome of melanoma cells. This finally led to the discovery of new potential targets for cancer immunotherapy.

Life-threatening Lymphatic Malformation With Somatic Activating NRAS Mutation Successfully Treated With Trametinib: A Case Study.

Kaposiform lymphangiomatosis (KLA) is a rare and aggressive subtype of complex lymphatic anomalies (CLA), characterized by abnormal lymphatic proliferation leading to distinct clinical manifestations. Despite the complexity of this condition, there is no established standard therapy, and treatment options such as sclerotherapy, laser therapy, and surgery remain variably effective and are limited to symptom management rather than curative. Sirolimus, an mTOR pathway inhibitor, has shown promise as a primary therapy, particularly in patients without a driver mutation. However, in some instances, the genetic landscape of KLA has revealed somatic mutations in the RAS-MAPK pathway, most notably the NRAS variant (c.182A>G, p.Q61R), representing a potential therapeutic target. We present a case of a 4-year-old male who presented with pericardial and pleural effusions without notable coagulopathy found to harbor an NRAS p.Gln61Arg gene mutation, diagnosed through next-generation sequencing (NGS) analysis. Initial therapy with sirolimus failed to provide optimal benefit with persistent pleural effusion. Subsequent treatment with the MEK inhibitor trametinib led to significant clinical improvement, evidenced by the resolution of effusions and removal of the chest tube. In the short term, no significant adverse effect was reported. Our findings underscore the value of genomic profiling in guiding personalized treatment strategies for rare and complex diseases presenting like KLA. This case highlights the potential of targeted therapies, such as trametinib, in improving clinical outcomes for patients with disease with activating NRAS variants, emphasizing the importance of ongoing research to validate and expand these therapeutic approaches in the management of vascular anomalies.

Identification of the Determinants of Plexiform Neurofibroma Morbidity in Pediatric and Young Adult Neurofibromatosis Type 1 Patients: A Pilot Multivariate Approach.

Plexiform neurofibromas (PNs) are histologically benign peripheral nerve sheath tumors associated with neurofibromatosis type 1 (NF1) and often lead to significant morbidity due to growth. Management includes watchful waiting, surgery for partial debulking, and, since recently, systemic treatment with MEK inhibitors. However, due to the scarcity of natural history studies, our understanding of the natural progression of PNs to guide clinicians in deciding in whom and when to intervene is scarce. This study aims to describe the characteristics of NF1 patients with PNs and compare those at high risk for PN progression or experiencing significant morbidity from PN (complex PN) with NF1 patients with PNs of lower complexity. In this retrospective cohort study using clinical data from hospital records of NF1 patients with PNs seen at the Sophia Children's Hospital in the Netherlands between 2012 and 2023, we assessed determinants of clinical phenotypes and PN characteristics predictive of outcomes, including PN complexity and the timing of intervention for PN. We assessed the outcomes using logistic regression analysis and Cox regression. Ninety patients with a median age at last evaluation of 15.7 years and a median follow-up duration of 9.8 years were included. Out of 90 individuals with a benign PN, 37 developed plexiform neurofibroma morbidity during follow-up. Older age was (corrected for pathogenic NF1 variant and PN location) significantly associated with plexiform neurofibroma morbidity. Cox regression revealed that craniofacial and trunk PNs were associated with a higher intervention hazard compared to limb PNs. Our pilot multivariate approach identified older age and the location of the PN to be mostly associated with a higher chance of plexiform neurofibroma morbidity and higher intervention hazard. This may contribute to decisions regarding in whom and when to initiate treatment in NF1 patients with PNs.

MEK inhibitors and DA-Raf, a dominant-negative antagonist of the Ras-ERK pathway, prevent the migration and invasion of KRAS-mutant cancer cells.

The Ras-induced ERK pathway (Raf-MEK-ERK signaling cascade) regulates a variety of cellular responses including cell proliferation, survival, and migration. Activating mutations in RAS genes, particularly in the KRAS gene, constitutively activate the ERK pathway, resulting in tumorigenesis, cancer cell invasion, and metastasis. DA-Raf1 (DA-Raf) is a splicing isoform of A-Raf and contains the Ras-binding domain but lacks the kinase domain. Consequently, DA-Raf antagonizes the Ras-ERK pathway in a dominant-negative manner and can serve as a tumor suppressor that targets mutant Ras protein-induced tumorigenesis. We show here that MEK inhibitors and DA-Raf interfere with the in vitro collective cell migration and invasion of human KRAS-mutant carcinoma cell lines, the lung adenocarcinoma A549, colorectal carcinoma HCT116, and pancreatic carcinoma MIA PaCa-2 cells. DA-Raf expression was silenced in these cancer cell lines. All these cell lines had high collective migration abilities and invasion properties in Matrigel, compared with nontumor cells. Their migration and invasion abilities were impaired by suppressing the ERK pathway with the MEK inhibitors U0126 and trametinib, an approved anticancer drug. Expression of DA-Raf in MIA PaCa-2 cells reduced the ERK activity and hindered the migration and invasion abilities. Therefore, DA-Raf may function as an invasion suppressor protein in the KRAS-mutant cancer cells by blocking the Ras-ERK pathway when DA-Raf expression is induced in invasive cancer cells.

The positive feedback loop between SP1 and MAP2K2 significantly drives resistance to VEGFR inhibitors in clear cell renal cell carcinoma.

Clear cell renal cell carcinoma (ccRCC) is one of the most common and aggressive malignancies of the urinary system. Despite being the first-line treatment for advanced ccRCC, vascular endothelial growth factor receptor inhibitors (VEGFRis) face significant limitations due to both initial and acquired resistance, which impede complete tumor eradication. Using a CRISPR/Cas9 library screening approach, MAP2K2 was identified as a resistance-associated gene for three prevalent VEGFRis (Sunitinib, Axitinib, and Sorafenib). A strong positive correlation was observed between MAP2K2 expression and resistance to these VEGFRis. Drug-resistant cell lines established through dose-escalation consistently exhibited elevated MAP2K2 expression and activation of the MEK/ERK signaling pathway. Notably, combining MEK inhibitors (MEKis) with VEGFRis significantly enhanced the sensitivity of these resistant cells, leading to pronounced cell death. Additionally, a positive feedback regulatory mechanism was discovered between SP1 and MAP2K2, wherein SP1 and MAP2K2 could enhance mutual expression, thereby maintaining MEK/ERK pathway activation. This study reveals that MEKis can effectively re-sensitize VEGFRi-resistant cells, offering a promising therapeutic strategy for overcoming VEGFRi resistance in ccRCC.

Mechanistic insights into Rho/MRTF inhibition-induced apoptotic events and prevention of drug resistance in melanoma: implications for the involvement of pirin.

Overcoming therapy resistance is critical for effective melanoma control. Upregulation of Rho/MRTF signaling in human and mouse melanomas causes resistance to targeted therapies. Inhibition of this pathway by MRTFi, CCG-257081 resensitized resistant melanomas to BRAF and MEK inhibitors. It also prevented the development of resistance to vemurafenib (Vem). Here, we investigate the role of apoptosis and the protein pirin in CCG-257081-mediated suppression of drug resistance. Using naïve and resistant mouse YUMMER melanoma cells, we studied the effect of the BRAF inhibitor Vem with or without CCG-257081 on real-time growth and apoptosis (activation of caspase, Propidium iodide (PI) staining, and PARP cleavage). The effects of CCG-257081 on proliferation (Ki67) and caspase-3 activation were assessed in resistant YUMMER_R tumors in vivo. Finally, two CCG-257081 enantiomers were tested for pirin binding, inhibition of the Rho/MRTF-mediated activation of ACTA2 gene expression in fibroblasts, and the prevention of Vem resistance development by YUMMER_P cells. Vem reduced growth of parental but not resistant cells, while CCG-257081 inhibited both. The combination was more effective than Vem alone. CCG-257081, but not Vem, induced activation of caspase-3 and -7 in resistant cells and increased PARP cleavage and PI staining. CCG-257081 reduced proliferation and activated caspase-3 in YUMMER_R melanoma tumors. Both CCG-257081 enantiomers robustly suppressed development of Vem-resistant colonies with the S isomer being more potent (1μM IC50). CCG-257081 appears to target pre-resistant cells and Vem-induced resistant cells through enhanced apoptosis. Inhibition of pirin or the Rho/MRTF pathway can be employed to prevent melanoma resistance.

Global trends and emerging insights in BRAF and MEK inhibitor resistance in melanoma: a bibliometric analysis.

This study aims to perform a comprehensive bibliometric analysis of global research on BRAF and MEK inhibitor resistance in melanoma, identifying key research trends, influential contributors, and emerging themes from 2003 to 2024. A systematic search was conducted in the Web of Science Core Collection (WoSCC) database to retrieve publications related to BRAF and MEK inhibitor resistance from 1 January 2003, to 1 September 2024. Bibliometric analyses, including publication trends, citation networks, and keyword co-occurrence patterns, were performed using VOSviewer and CiteSpace. Collaborative networks, co-cited references, and keyword burst analyses were mapped to uncover shifts in research focus and global cooperation. A total of 3,503 documents, including 2,781 research articles and 722 review papers, were analyzed, highlighting significant growth in this field. The United States, China, and Italy led in publication volume and citation impact, with Harvard University and the University of California System among the top contributing institutions. Research output showed three phases of growth, peaking in 2020. Keyword and co-citation analyses revealed a transition from early focus on BRAF mutations and MAPK pathway activation to recent emphasis on immunotherapy, combination therapies, and non-apoptotic cell death mechanisms like ferroptosis and pyroptosis. These trends reflect the evolving priorities and innovative approaches shaping the field of resistance to BRAF and MEK inhibitors in melanoma. Research on BRAF and MEK inhibitor resistance has evolved significantly. This analysis provides a strategic framework for future investigations, guiding the development of innovative, multi-modal approaches to improve treatment outcomes for melanoma patients.

Synergistic two-step inhibition approach using a combination of trametinib and onvansertib in KRAS and TP53-mutated colorectal adenocarcinoma.

Colorectal malignancies associated with KRAS and TP53 mutations led us to investigate the effects of combination therapy targeting KRAS, MEK1, or PLK1 in colorectal cancer. MEK1 is downstream of RAS in the MAPK pathway, whereas PLK1 is a mitotic kinase of the cell cycle activated by MAPK and regulated by p53. Bioinformatics analysis revealed that patients with colorectal cancer had a high expression of MAP2K1 and PLK1. Furthermore, PLK1 and MEK1 activity in human colorectal adenocarcinoma (COAD) tissues was found to be highly upregulated compared to healthy tissues. To determine the sensitivity of KRAS or/and TP53-mutated cancer to KRAS, MEK1, or PLK1-targeted therapy, the inhibitors salirasib, trametinib, volasertib, and onvansertib were used in COAD cells with different KRAS and TP53 status. The results showed that combinations with trametinib and PLK1 inhibitors were more potent than combinations with salirasib. A combination of MEK1 and PLK1 inhibitors exhibited significant therapeutic effects on KRAS or/and TP53-mutated COAD cells. Notably, the combination of trametinib and onvansertib effectively suppressed tumor growth in a xenograft mouse model of KRAS and TP53-mutated COAD. This treatment induced G1 and G2/M arrest, respectively, and showed the strongest synergistic effect in KRAS and TP53-mutated SW48 cells expressing mutant KRASG13D and transduced with TP53 shRNA, ultimately leading to apoptotic cell death. These effects are attributed to two-step inhibition mechanism that blocks the MAPK signaling pathway and disrupts mitosis in KRAS and TP53-mutated COAD cells.

A comparison of real-world data on adjuvant treatment in patients with stage III BRAF V600 mutated melanoma - Results of systematic literature research.

Over the past decade, PD-1-based immune checkpoint inhibitors (ICI) and targeted therapies (TT) with BRAF and MEK inhibitors transformed melanoma treatment. Both are widely used in the adjuvant setting. However, for patients with a BRAF V600 mutation, the optimal adjuvant therapy remains unclear due to the lack of head-to-head comparison studies. We conducted a systematic review of real-world data on adjuvant therapy in stage III melanoma to determine the best option for patients with BRAF V600 mutations. Kaplan-Meier curves were generated for TT and ICI using Digitizelt software. Nine publications with 3625 patients were included. TT showed better relapse-free survival (RFS) at 6, 12, 24, and 36 months than ICI. A similar trend was observed for distant metastasis-free survival (DMFS), with no apparent difference in overall survival. Real-world data suggest that adjuvant TT may be associated with better RFS and DMFS in stage III BRAF V600-mutated melanoma compared to ICI.

Selumetinib in adults with NF1 and inoperable plexiform neurofibroma: a phase 2 trial.

The MEK inhibitor selumetinib induces objective responses and provides clinical benefit in children with neurofibromatosis type 1 (NF1) and inoperable plexiform neurofibromas (PNs). To evaluate whether similar outcomes were possible in adult patients, in whom PN growth is generally slower than in pediatric patients, we conducted an open-label phase 2 study of selumetinib in adults with NF1 PNs. The study was designed to evaluate objective response rate (primary objective), tumor volumetric responses, patient-reported outcomes and pharmacodynamic effects in PN biopsies. The objective response rate was 63.6% (21/33 participants). Median maximal PN volume decrease was 23.6% (range: -48.1% to 5.5%). No disease progression relative to baseline PN volumes occurred before data cutoff, with a median of 28 cycles completed (range: 1-78, 28 d per cycle). Participants experienced decreased tumor pain intensity and pain interference. Adverse events (AEs) were similar to those of the pediatric trial; acneiform rash was the most prevalent AE. Phosphorylation ratios of ERK1/2 decreased significantly (ERK1 median change: -64.6% (range: -99.5% to 90.7%), ERK2 median change: -57.3% (range: -99.9% to 84.4%)) in paired PN biopsies (P ≤ 0.001 for both isoforms) without compensatory phosphorylation of AKT1/2/3. The sustained PN volume decreases, associated improvement in pain and manageable AE profile indicate that selumetinib provides benefit to adults with NF1 and inoperable PNs. ClinicalTrials.gov identifier: NCT02407405 .

Trametinib and M17, a novel small molecule inhibitor of AKT, display a synergistic antitumor effect in triple negative breast cancer cells through the AKT/mTOR and MEK/ERK pathways.

Triple negative breast cancer (TNBC) is associated with a poor prognosis and limited response to traditional chemotherapy, necessitating the exploration of novel treatment approaches. Recent researches have highlighted the interconnected roles of the PI3K/AKT pathway and MAPK pathway in TNBC cells, contributing to the efficacy of treatments. Therefore, the concurrent inhibition of both pathways presents a potential new therapeutic strategy for TNBC patients. This study aimed to evaluate the antitumor efficacy of M17, an AKT allosteric inhibitor and a new synthesized shikonin derivative, both alone and in combination with the MEK inhibitor trametinib. We applied various cellular assays and a subcutaneous 4T1 tumor bearing BALB/c mice model were utilized to assess the in vitro and in vivo antitumor effects. Computational docking and Bio-Layer Interferometry (BLI) were employed to investigate the binding of M17 with AKT. Additionally, flow cytometry, transwell assays, western blotting, and tumor xenograft assays were conducted to explore the potential synergistic mechanisms of the combined therapy. The results demonstrated that M17 exhibited moderate antitumor activity against TNBC cells, but significantly enhanced the apoptotic effects and inhibited proliferation and migration when combined with trametinib. Furthermore, the combination of M17 and trametinib showed even more pronounced antitumor activity in vivo. Mechanistically, the dual therapy synergistically suppressed TNBC by targeting the AKT/mTOR and MEK/ERK signaling pathways and inhibiting epithelial-mesenchymal transition. In conclusion, the findings suggested that the combination of M17 and trametinib holds promise as a synergistic treatment option for TNBC patients.

Variations in the Management of Low-Grade Serous Carcinoma of the Ovary: A Global Survey

ObjectiveLow-grade serous carcinoma (LGSOC) constituting < 15% of ovarian or peritoneal serous carcinomas differs distinctly from high-grade serous ovarian carcinoma (HGSOC). This global survey investigates the variations in managing LGSOC, acknowledging its unique characteristics and the absence of a consensus on optimal management.MethodsA voluntary non-incentivized global survey gathered responses from 203 practitioners across 50 countries and 7 continents. Approved by the Institutional Ethics Committee, it encompassed 21 questions focusing on demographics, diagnosis, and management practices. Descriptive statistics and Fisher’s exact test analyzed the data.ResultsDemographically diverse responses were obtained with the majority from India (39.9%) and Colombia (5.4%). Gynecologic oncologists predominated (73.10%), with varied practice settings. Most practitioners considered LGSOC distinct (95.57%). Diagnosis criteria showed institutional variations. In managing apparent inoperable stage III C LGSOC approaches varied: neoadjuvant chemotherapy (54.78%), upfront surgery (35.69%), and neoadjuvant hormone therapy (8.54%). Adjuvant management demonstrated heterogeneity. Notably, there was no significant association between the continent and the offered adjuvant treatment for optimally cytoreduced stage III C LGSOC (p = 0.556; Fisher’s exact test). For recurrent disease, hormonal therapy (30.54%) and chemotherapy (27.59%) were common choices. MEK inhibitors were infrequently used. Fertility preservation was favored (71%), and HIPEC was not widely considered (81.28%). Genetic testing opinions varied: routine testing (28.7%), no recommendation (45.32%), and testing in recurrent settings (16.75%).ConclusionThis survey exposes global disparities in LGSOC management, highlighting the need for standardized guidelines to address challenges in diagnosis and management. International collaboration is advocated to enhance uniformity in healthcare practices for LGSOC.

Hydroxychloroquine prevents resistance and potentiates the antitumor effect of SHP2 inhibition in NF1-associated malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas and the primary cause of mortality in patients with neurofibromatosis type 1 (NF1). These malignancies develop within preexisting benign lesions called plexiform neurofibromas (PNs). PNs are solely driven by biallelic NF1 loss eliciting RAS pathway activation, and they respond favorably to MEK inhibitor therapy. MPNSTs harbor additional mutations and respond poorly to MEK inhibition. Our analysis of genetically engineered and orthotopic patient-derived xenograft MPNST models indicates that MEK inhibition has poor antitumor efficacy. By contrast, upstream inhibition of RAS through the protein-tyrosine phosphatase SHP2 reduced downstream signaling and suppressed NF1 MPNST growth, although resistance eventually emerged. To investigate possible mechanisms of acquired resistance, kinomic analyses of resistant tumors were performed, and data analysis identified enrichment of activated autophagy pathway protein kinases. Combining SHP2 inhibition with hydroxychloroquine (HQ) resulted in durable responses in NF1 MPNSTs in both genetic and orthotopic xenograft mouse models. Our studies could be rapidly translated into a clinical trial to evaluate SHP2 inhibition in conjunction with HQ as a unique treatment approach for NF1 MPNSTs.

Triple Combination of MEK, BET, and CDK Inhibitors Significantly Reduces Human Malignant Peripheral Nerve Sheath Tumors in Mouse Models.

Malignant peripheral nerve sheath tumor (MPNST) is an aggressive soft tissue sarcoma that develops sporadically or in Neurofibromatosis type 1 patients. Its development is marked by the inactivation of specific tumor suppressor genes (TSGs): NF1, CDKN2A and SUZ12EED (Polycomb Repressor Complex 2). Each TSG loss can be targeted by particular drug inhibitors and we aimed to systematically combine these inhibitors, guided by TSG inactivation status, to test their precision medicine potential for MPNSTs. We performed a high-throughput screening in three MPNST cell lines testing 14 MEK (MEKi), 11 CDK4/6 (CDKi) and 3 bromodomain (BETi) inhibitors as single agents and 147 pair-wise co-treatments. Best combinations were validated in 9 MPNST cell lines and three were tested in one sporadic and one NF1-associated patient-derived orthotopic xenograft (PDOX) MPNST mouse models. A final combination of the three inhibitor classes was tested in the same PDOX models. A high degree of redundancy was observed in the effect of compounds of the same inhibitory class, individually or in combination, and responses matched with TSG inactivation status. The MEKi-BETi (Arry-162+I-BET151) co-treatment triggered reduction of half of the NF1-related MPNST-PDOXs, and all the sporadic tumors, reaching 65% reduction in tumor volume in the latter. Remarkably, this reduction was further increased in both models combining the three inhibitor classes, reaching 85% shrinkage on average in the sporadic MPNST. Our results strongly support precision therapies for MPNSTs guided by TSG inactivation status. MEKi-BETi-CDKi triple treatment elicits a significant reduction of human MPNST PDOX.

EPLIN, a prospective oncogenic molecule with contribution to growth, migration and drug resistance in pancreatic cancer

Most pancreatic cancer patients are diagnosed at advanced stages, with poor survival rates and drug resistance making pancreatic cancer one of the highest causes of cancer death in the UK. Understanding the underlying mechanism behind its carcinogenesis, metastasis and drug resistance has become an essential task for researchers. We have discovered that a well-established tumour suppressor, EPLIN, has an oncogenic rather than suppressive role in pancreatic cancer. Notably, upregulation of EPLIN was observed in pancreatic cancer samples compared to normal samples at RNA and protein levels. Moreover, the presence of EPLIN resulted in poor clinical outcomes in patients. We also report that inhibition of EPLIN led to reduced cellular growth and migration in pancreatic cancer cells. EPLIN regulates expression and phosphorylation levels of several key players in MAPK and PIK3CA-AKT signalling pathways, as well as key contributors of EMT. Furthermore, EPLIN mediates the inhibitory ability PIK3 kinases, MEK and ERK inhibitors have on cell migration. EPLIN was also found to have an impact on pancreatic cancer cells response to chemotherapeutic and EGFR/HER2 targeted therapeutic agents, namely gemcitabine, fluorouracil (5FU) and neratinib (Nerlynx).

Quantitative Live Imaging Reveals Phase Dependency of PDAC Patient-Derived Organoids on ERK and AMPK Activity.

Patient-derived organoids represent a novel platform to recapitulate the cancer cells in the patient tissue. While cancer heterogeneity has been extensively studied by a number of omics approaches, little is known about the spatiotemporal kinase activity dynamics. Here we applied a live imaging approach to organoids derived from 10 pancreatic ductal adenocarcinoma (PDAC) patients to comprehensively understand their heterogeneous growth potential and drug responses. By automated wide-area image acquisitions and analyses, the PDAC cells were non-selectively observed to evaluate their heterogeneous growth patterns. We monitored single-cell ERK and AMPK activities to relate cellular dynamics to molecular dynamics. Furthermore, we evaluated two anti-cancer drugs, a MEK inhibitor, PD0325901, and an autophagy inhibitor, hydroxychloroquine (HCQ), by our analysis platform. Our analyses revealed a phase-dependent regulation of PDAC organoid growth, where ERK activity is necessary for the early phase and AMPK activity is necessary for the late stage of organoid growth. Consistently, we found PD0325901 and HCQ target distinct organoid populations, revealing their combination is widely effective to the heterogeneous cancer cell population in a range of PDAC patient-derived organoid lines. Together, our live imaging quantitatively characterized the growth and drug sensitivity of human PDAC organoids at multiple levels: in single cells, single organoids, and individual patients. This study will pave the way for understanding the cancer heterogeneity and promote the development of new drugs that eradicate intractable cancer.

Impact of BRAF and MEK Inhibitors on Gingival Hyperplasia in Melanoma Patients—A Case Report

Background: Although BRAF inhibitors, such as vemurafenib, produce a marked response in patients with advanced melanoma with a BRAF V600 mutation, they eventually develop resistance to this treatment. To address this issue, vemurafenib is increasingly combined with the MEK inhibitor cobimetinib, leading to improved response rates and enhanced survival. However, this treatment modality is associated with numerous side effects. We present a case of gingival hyperplasia in a patient treated with vemurafenib, along with the strategy adopted for the management of this condition, and the impact of subsequent cobimetinib administration on its severity. Methods: The 59-year-old male patient in the focus of this report presented at the Department of Periodontology at the Medical Faculty, University of Novi Sad, in 2019, complaining of gingival overgrowth and bleeding. The patient reported persistent gum swelling during the preceding six months, which he ascribed to the use of vemurafenib, 960 mg twice daily, since 2018, when this medication was prescribed as a part of malignant melanoma treatment. Detailed clinical examination revealed significant gingival overgrowth around all present teeth, affecting the vestibular as well as the oral sides. The patient underwent thorough scaling and root planing, followed by the surgical removal of hyperplastic gingiva. After gingivectomy, the patient was scheduled for follow-up visits at one-month intervals. Six months after gingivectomy, vemurafenib dose was reduced to 720 mg twice daily, and cobimetinib was introduced at 60 mg per day. Results: The treatment protocol adopted in this study, combined with cobimetinib administration, stabilized the gingiva condition in this patient. However, due to his overall poor oral hygiene, gingiva remained inflamed and edematous, but was no longer hyperplastic and hyperkeratotic in appearance. Conclusions: This case underscores the importance of recognizing and adequately addressing this complication, as its adverse effect on a patient’s quality of life can potentially compromise treatment protocol adherence.