Targeting RAS Mutant Colorectal Cancer with Dual Inhibition of MEK and CDK4/6

PDP1 promotes KRAS mutant colorectal cancer progression by serving as a scaffold for BRAF and MEK1

The oncogenic role of KRAS in colorectal cancer (CRC) progression is well-established. Despite this, identifying effective therapeutic targets for KRAS-mutated CRC remains a significant challenge. This study identifies pyruvate dehydrogenase phosphatase catalytic subunit 1 (PDP1) as a previously unrecognized yet crucial regulator in the progression of KRAS mutant CRC. A substantial upregulation of PDP1 expression is observed in KRAS mutant CRC cells and tissues compared to wild-type KRAS samples, which correlates with poorer prognosis. Functional experiments elucidate that PDP1 accelerates the malignance of KRAS mutant CRC cells, both in vitro and in vivo. Mechanistically, PDP1 acts as a scaffold, enhancing BRAF and MEK1 interaction and activating the MAPK signaling, thereby promoting CRC progression. Additionally, transcription factor KLF5 is identified as the key regulator for PDP1 upregulation in KRAS mutant CRC. Crucially, targeting PDP1 combined with MAPK inhibitors exhibits an obvious inhibitory effect on KRAS mutant CRC. Overall, PDP1 is underscored as a vital oncogenic driver and promising therapeutic target for KRAS mutant CRC.

EGFR and PI3K Signalling Pathways as Promising Targets on Circulating Tumour Cells from Patients with Metastatic Gastric Adenocarcinoma

The prognosis for metastatic gastric adenocarcinoma (mGAC) remains poor. Gene alterations in receptor tyrosine kinases (RTKs) such as epidermal growth factor receptor (EGFR) and their downstream effectors including catalytic subunit alpha of the phosphatidylinositol 3-kinase (PIK3CA) are common in mGAC. Targeted RTK and phosphatidylinositol-3-kinase (PI3K) treatments have demonstrated clinical benefits in other solid tumours and are key potential targets for clinical development against mGAC given the presence of recurrent alterations in these pathways. Furthermore, combination RTK/PI3K treatments may overcome compensatory mechanisms that arise using monotherapies, leading to improved patient outcomes. Herein, we investigated RTK/PI3K single and combination drug responses against our unique human mGAC-derived PIK3CA gain-of-function mutant, human epidermal growth factor receptor 2 (HER2)-negative, EGFR-expressing circulating tumour cell line, UWG02CTC, under two- and three-dimensional culture conditions to model different stages of metastasis. UWG02CTCs were highly responsive to the PI3K p110α-subunit targeted drugs PIK-75 (IC50 = 37.0 ± 11.1 nM) or alpelisib (7.05 ± 3.7 µM). Drug sensitivities were significantly increased in 3D conditions. Compensatory MAPK/ERK pathway upregulation by PI3K/Akt suppression was overcome by combination treatment with the EGFR inhibitor gefitinib, which was strongly synergistic. PIK-75 plus gefitinib significantly impaired UWG02CTC invasion in an organotypic assay. In conclusion, UWG02CTCs are a powerful ex vivo mGAC drug responsiveness model revealing EGFR/PI3K-targeted drugs as a promising combination treatment option for HER2-negative, RAS wild-type mGAC patients.

Synergistic induction of autophagy in gastric cancer by targeting CDK4/6 and MEK through AMPK/mTOR pathway

KRAS is a commonly mutated oncogene in human gastric cancer and is often associated with drug resistance and poor prognosis. Co-clinical trial of combined MEK-CDK4/6 inhibition in KRAS mutated cancers demonstrated therapeutic efficacy in patient-derived xenografts and safety in patients. Here, present research focuses on targeting CDK4/6 and MEK synergistically block the proliferation of KRAS-mutated gastric cancer cells in vitro and in vivo and induced autophagy through the AMPK/mTOR pathway. Furthermore, autophagy inhibitor combined with targeting CDK4/6 and MEK therapy had significant antitumor effects on KRAS mutant gastric cancer cells. Clinical trials are needed to determine the mechanism behind this finding and its clinical utility. In conclusion, our results demonstrate autophagy inhibitor combined targeting MEK and CDK4/6 that concurrently block multiple metabolic processes may be an effective therapeutic approach for gastric cancer.

Combinatorial strategies to target RAS-driven cancers

Although RAS was formerly considered undruggable, various agents that inhibit RAS or specific RAS oncoproteins have now been developed. Indeed, the importance of directly targeting RAS has recently been illustrated by the clinical success of mutant-selective KRAS inhibitors. Nevertheless, responses to these agents are typically incomplete and restricted to a subset of patients, highlighting the need to develop more effective treatments, which will likely require a combinatorial approach. Vertical strategies that target multiple nodes within the RAS pathway to achieve deeper suppression are being investigated and have precedence in other contexts. However, alternative strategies that co-target RAS and other therapeutic vulnerabilities have been identified, which may mitigate the requirement for profound pathway suppression. Regardless, the efficacy of any given approach will likely be dictated by genetic, epigenetic and tumour-specific variables. Here we discuss various combinatorial strategies to treat KRAS-driven cancers, highlighting mechanistic concepts that may extend to tumours harbouring other RAS mutations. Although many promising combinations have been identified, clinical responses will ultimately depend on whether a therapeutic window can be achieved and our ability to prospectively select responsive patients. Therefore, we must continue to develop and understand biologically diverse strategies to maximize our likelihood of success.

Binimetinib in combination with nivolumab or nivolumab and ipilimumab in patients with previously treated microsatellite-stable metastatic colorectal cancer with RAS mutations in an open-label phase 1b/2 study

BACKGROUND

In patients with previously treated RAS-mutated microsatellite-stable (MSS) metastatic colorectal cancer (mCRC), a multicenter open-label phase 1b/2 trial was conducted to define the safety and efficacy of the MEK1/MEK2 inhibitor binimetinib in combination with the immune checkpoint inhibitor (ICI) nivolumab (anti-PD-1) or nivolumab and another ICI, ipilimumab (anti-CTLA4).

METHODS

In phase 1b, participants were randomly assigned to Arm 1A (binimetinib 45 mg twice daily [BID] plus nivolumab 480 mg once every 4 weeks [Q4W]) or Arm 1B (binimetinib 45 mg BID plus nivolumab 480 mg Q4W and ipilimumab 1 mg/kg once every 8 weeks [Q8W]) to determine the maximum tolerable dose (MTD) and recommended phase 2 dose (RP2D) of binimetinib. The MTD/RP2D was defined as the highest dosage combination that did not cause medically unacceptable dose-limiting toxicities in more than 35% of treated participants in Cycle 1. During phase 2, participants were randomly assigned to Arm 2A (binimetinib MTD/RP2D plus nivolumab) or Arm 2B (binimetinib MTD/RP2D plus nivolumab and ipilimumab) to assess the safety and clinical activity of these combinations.

RESULTS

In phase 1b, 21 participants were randomized to Arm 1A or Arm 1B; during phase 2, 54 participants were randomized to Arm 2A or Arm 2B. The binimetinib MTD/RP2D was determined to be 45 mg BID. In phase 2, no participants receiving binimetinib plus nivolumab achieved a response. Of the 27 participants receiving binimetinib, nivolumab, and ipilimumab, the overall response rate was 7.4% (90% CI: 1.3, 21.5). Out of 75 participants overall, 74 (98.7%) reported treatment-related adverse events (AEs), of whom 17 (22.7%) reported treatment-related serious AEs.

CONCLUSIONS

The RP2D binimetinib regimen had a safety profile similar to previous binimetinib studies or nivolumab and ipilimumab combination studies. There was a lack of clinical benefit with either drug combination. Therefore, these data do not support further development of binimetinib in combination with nivolumab or nivolumab and ipilimumab in RAS-mutated MSS mCRC.

TRIAL REGISTRATION

NCT03271047 (09/01/2017).

Domperidone inhibits cell proliferation via targeting MEK and CDK4 in esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is one of the leading causes of digestive system tumor related death in the world. Unfortunately, effective chemopreventive agent is lack for patients with ESCC in clinical practice, which leads to the extremely high mortality rate.

METHODS

A library of prescribed drugs was screened for finding critical anti-tumor properties in ESCC cells. The phosphoproteomics, kinase array, pulldown assay and drug affinity responsive target stabilization assay (DARTS) were applied to explore mechanisms and searched for synergistic targets. Established models of PDX in mice were used to determine the therapeutic effect of domperidone.

RESULTS

After screening a library of prescribed drugs, we discovered that domperidone has anti-tumor properties. Domperidone, acting as a gastroprokinetic agent, has been widely used in clinic for gastrointestinal motility disorders. Despite limited research, there are indications that domperidone may have anti-tumor properties. In this study, we determined that domperidone significantly inhibited ESCC proliferation in vitro and in vivo. We employed phosphoproteomics to reveal p-ERK, and p-SMAD3 down-regulation upon domperidone treatment. Then, the results of kinase assay and pulldown assay further validated that domperidone directly combined with MEK1/2 and CDK4, leading to the inhibition of their kinase activity. Furthermore, our results revealed that MEK/ERK and CDK4/SMAD3 signal pathway were major pathways in domperidone against ESCC.

CONCLUSION

Collectively, these findings suggest that domperidone serves as an effective "multi-target" inhibitor of MEK1/2 and CDK4, offering potential benefits for the chemoprevention of ESCC.

Consistency between Primary Uterine Corpus Malignancies and Their Corresponding Patient-Derived Xenograft Models

Patient-derived xenograft (PDX) models retain the characteristics of tumors and are useful tools for personalized therapy and translational research. In this study, we aimed to establish PDX models for uterine corpus malignancies (UC-PDX) and analyze their similarities. Tissue fragments obtained from 92 patients with uterine corpus malignancies were transplanted subcutaneously into immunodeficient mice. Histological and immunohistochemical analyses were performed to compare tumors of patients with PDX tumors. DNA and RNA sequencing were performed to validate the genetic profile. Furthermore, the RNA in extracellular vesicles (EVs) extracted from primary and PDX tumors was analyzed. Among the 92 cases, 52 UC-PDX models were established, with a success rate of 56.5%. The success rate depended on tumor histology and staging. The pathological and immunohistochemical features of primary and PDX tumors were similar. DNA sequencing revealed similarities in gene mutations between the primary and PDX tumors. RNA sequencing showed similarities in gene expressions between primary and PDX tumors. Furthermore, the RNA profiles of the EVs obtained from primary and PDX tumors were similar. As UC-PDX retained the pathological and immunohistochemical features and gene profiles of primary tumors, they may provide a platform for developing personalized medicine and translational research.

Protective effects of palbociclib on colitis-associated colorectal cancer

Background

Chronic or recurrent inflammatory injury to the intestinal mucosa is closely related to inflammation-related colorectal cancer (CRC). This study aimed to examine the protective effects of palbociclib, a stimulator of interferon genes (STING) antagonist, on colitis-related colorectal carcinogenesis.

Methods

Bioinformatic analyses, including Gene Ontology (GO) enrichment, gene set enrichment analysis (GSEA), and network analysis, were conducted. Male C57BL/6 mice were administered azoxymethane (AOM) and dextran sulfate sodium (DSS), followed by treatment with palbociclib for 6 weeks. The general conditions of mice were observed and recorded. The colon histopathology was assessed based on hematoxylin and eosin (H&E) staining results. Relative messenger RNA (mRNA) expression levels of interferon b1 (Ifnb1), interleukin 6 (Il6), and interleukin 1b (Il1b) in colon were estimated based on quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) analysis.

Results

The STING signaling pathway was significantly upregulated in stages III and IV of CRC in The Cancer Genome Atlas (TCGA)-CRC cohort. After treatment with AOM/DSS, the weight of mice decreased significantly, whereas administration of palbociclib partially reversed this trend. The mouse colon treated with AOM/DSS showed significant pathological damages, disorderly epithelial cell structure, atypical hyperplasia, and infiltration of several inflammatory cell types; however, the colon damage was remarkably reduced upon treatment with palbociclib. It was also found that palbociclib almost abolished the increase in the downstream effectors of STING-mediated transcription in the colon tissue treated with AOM/DSS, as evidenced by the transcription levels of Ifnb1, Il6, and Il1b.

Conclusions

These findings indicate that the STING pathway is closely associated with CRC. Palbociclib significantly alleviates tumor development in AOM/DSS-induced colitis-associated CRC.

Allosteric SHP2 inhibition increases apoptotic dependency on BCL2 and synergizes with venetoclax in FLT3- and KIT-mutant AML

Mutations in the receptor tyrosine kinases (RTKs) FLT3 and KIT are frequent and associated with poor outcomes in acute myeloid leukemia (AML). Although selective FLT3 inhibitors (FLT3i) are clinically effective, remissions are short-lived due to secondary resistance characterized by acquired mutations constitutively activating the RAS/MAPK pathway. Hereby, we report the pre-clinical efficacy of co-targeting SHP2, a critical node in MAPK signaling, and BCL2 in RTK-driven AML. The allosteric SHP2 inhibitor RMC-4550 suppresses proliferation of AML cell lines with FLT3 and KIT mutations, including cell lines with acquired resistance to FLT3i. We demonstrate that pharmacologic SHP2 inhibition unveils an Achilles' heel of RTK-driven AML, increasing apoptotic dependency on BCL2 via MAPK-dependent mechanisms, including upregulation of BMF and downregulation of MCL1. Consequently, RMC-4550 and venetoclax are synergistically lethal in AML cell lines and in clinically relevant xenograft models. Our results provide mechanistic rationale and pre-clinical evidence for co-targeting SHP2 and BCL2 in RTK-driven AML.

Targeted splicing therapy: new strategies for colorectal cancer

RNA splicing is the process of forming mature mRNA, which is an essential phase necessary for gene expression and controls many aspects of cell proliferation, survival, and differentiation. Abnormal gene-splicing events are closely related to the development of tumors, and the generation of oncogenic isoform in splicing can promote tumor progression. As a main process of tumor-specific splicing variants, alternative splicing (AS) can promote tumor progression by increasing the production of oncogenic splicing isoforms and/or reducing the production of normal splicing isoforms. This is the focus of current research on the regulation of aberrant tumor splicing. So far, AS has been found to be associated with various aspects of tumor biology, including cell proliferation and invasion, resistance to apoptosis, and sensitivity to different chemotherapeutic drugs. This article will review the abnormal splicing events in colorectal cancer (CRC), especially the tumor-associated splicing variants arising from AS, aiming to offer an insight into CRC-targeted splicing therapy.

Targeting KRAS in Colorectal Cancer: A Bench to Bedside Review

Colorectal cancer (CRC) is a heterogeneous disease with a myriad of alterations at the cellular and molecular levels. Kristen rat sarcoma (KRAS) mutations occur in up to 40% of CRCs and serve as both a prognostic and predictive biomarker. Oncogenic mutations in the KRAS protein affect cellular proliferation and survival, leading to tumorigenesis through RAS/MAPK pathways. Until recently, only indirect targeting of the pathway had been investigated. There are now several KRAS allele-specific inhibitors in late-phase clinical trials, and many newer agents and targeting strategies undergoing preclinical and early-phase clinical testing. The adequate treatment of KRAS-mutated CRC will inevitably involve combination therapies due to the existence of robust adaptive resistance mechanisms in these tumors. In this article, we review the most recent understanding and findings related to targeting KRAS mutations in CRC, mechanisms of resistance to KRAS inhibitors, as well as evolving treatment strategies for KRAS-mutated CRC patients.

The Nanotechnology-Based Approaches against Kirsten Rat Sarcoma-Mutated Cancers

Kirsten rat sarcoma (KRAS) is a small GTPase which acts as a molecular switch to regulate several cell biological processes including cell survival, proliferation, and differentiation. Alterations in KRAS have been found in 25% of all human cancers, with pancreatic cancer (90%), colorectal cancer (45%), and lung cancer (35%) being the types of cancer with the highest mutation rates. KRAS oncogenic mutations are not only responsible for malignant cell transformation and tumor development but also related to poor prognosis, low survival rate, and resistance to chemotherapy. Although different strategies have been developed to specifically target this oncoprotein over the last few decades, almost all of them have failed, relying on the current therapeutic solutions to target proteins involved in the KRAS pathway using chemical or gene therapy. Nanomedicine can certainly bring a solution for the lack of specificity and effectiveness of anti-KRAS therapy. Therefore, nanoparticles of different natures are being developed to improve the therapeutic index of drugs, genetic material, and/or biomolecules and to allow their delivery specifically into the cells of interest. The present work aims to summarize the most recent advances related to the use of nanotechnology for the development of new therapeutic strategies against KRAS-mutated cancers.

Modeling the Tumor Microenvironment and Cancer Immunotherapy in Next-Generation Humanized Mice

Cancer immunotherapy has brought significant clinical benefits to numerous patients with malignant disease. However, only a fraction of patients experiences complete and durable responses to currently available immunotherapies. This highlights the need for more effective immunotherapies, combination treatments and predictive biomarkers. The molecular properties of a tumor, intratumor heterogeneity and the tumor immune microenvironment decisively shape tumor evolution, metastasis and therapy resistance and are therefore key targets for precision cancer medicine. Humanized mice that support the engraftment of patient-derived tumors and recapitulate the human tumor immune microenvironment of patients represent a promising preclinical model to address fundamental questions in precision immuno-oncology and cancer immunotherapy. In this review, we provide an overview of next-generation humanized mouse models suitable for the establishment and study of patient-derived tumors. Furthermore, we discuss the opportunities and challenges of modeling the tumor immune microenvironment and testing a variety of immunotherapeutic approaches using human immune system mouse models.

Feedback activation of EGFR/wild-type RAS signaling axis limits KRASG12D inhibitor efficacy in KRASG12D-mutated colorectal cancer

Colorectal cancer (CRC), which shows a high degree of heterogeneity, is the third most deadly cancer worldwide. Mutational activation of KRAS^G12D occurs in approximately 10-12% of CRC cases, but the susceptibility of KRAS^G12D-mutated CRC to the recently discovered KRAS^G12D inhibitor MRTX1133 has not been fully defined. Here, we report that MRTX1133 treatment caused reversible growth arrest in KRAS^G12D-mutated CRC cells, accompanied by partial reactivation of RAS effector signaling. Through a drug-anchored synthetic lethality screen, we discovered that epidermal growth factor receptor (EGFR) inhibition was synthetic lethal with MRTX1133. Mechanistically, MRTX1133 treatment downregulated the expression of ERBB receptor feedback inhibitor 1 (ERRFI1), a crucial negative regulator of EGFR, thereby causing EGFR feedback activation. Notably, wild-type isoforms of RAS, including H-RAS and N-RAS, but not oncogenic K-RAS, mediated signaling downstream of activated EGFR, leading to RAS effector signaling rebound and reduced MRTX1133 efficacy. Blockade of activated EGFR with clinically used antibodies or kinase inhibitors suppressed the EGFR/wild-type RAS signaling axis, sensitized MRTX1133 monotherapy, and caused the regression of KRAS^G12D-mutant CRC organoids and cell line-derived xenografts. Overall, this study uncovers feedback activation of EGFR as a prominent molecular event that restricts KRAS^G12D inhibitor efficacy and establishes a potential combination therapy consisting of KRAS^G12D and EGFR inhibitors for patients with KRAS^G12D-mutated CRC.

Insights on the Biomarker Potential of Exosomal Non-Coding RNAs in Colorectal Cancer: An In Silico Characterization of Related Exosomal lncRNA/circRNA–miRNA–Target Axis

Colorectal cancer (CRC) is one of the most common cancer types, ranking third after lung and breast cancers. As such, it demands special attention for better characterization, which may eventually result in the development of early detection strategies and preventive measures. Currently, components of bodily fluids, which may reflect various disease states, are being increasingly researched for their biomarker potential. One of these components is the circulating extracellular vesicles, namely, exosomes, which are demonstrated to carry various cargo. Of importance, the non-coding RNA cargo of circulating exosomes, especially long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and micro RNAs (miRNAs), may potentially serve as significant diagnostic and prognostic/predictive biomarkers. In this review, we present existing evidence on the diagnostic and prognostic/predictive biomarker value of exosomal non-coding RNAs in CRC. In addition, taking advantage of the miRNA sponging functionality of lncRNAs and circRNAs, we demonstrate an experimentally validated CRC exosomal non-coding RNA-regulated target gene axis benefiting from published miRNA sponging studies in CRC. Hence, we present a set of target genes and pathways downstream of the lncRNA/circRNA–miRNA–target axis along with associated significant Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, which may collectively serve to better characterize CRC and shed light on the significance of exosomal non-coding RNAs in CRC diagnosis and prognosis/prediction.

Targeting KRASG12C in colorectal cancer: the beginning of a new era

RAS mutation is considered one of the most relevant oncogenic drivers in human cancers. Unfortunately, for more than three decades, RAS has been considered an undruggable target. Recently, the discovery of selective and potent KRAS^G12C inhibitors represented a light at the end of the tunnel. Indeed, sotorasib and adagrasib proved clinical activity in patients with refractory metastatic colorectal cancer harboring KRAS^G12C mutation; however, responses are lower than expected, suggesting the presence of intrinsic resistance. Consequently, novel combinatory strategies to disrupt the RAS signaling pathways are under clinical investigation. This review aims to discuss the current knowledge and novel routes of KRAS^G12C inhibition in metastatic colorectal cancer.

Minor structural changes, major functional impacts: posttranslational modifications and drug targets

Posttranslational modifications (PTMs) are essential mechanisms that provide chemical diversity to proteins. The additional functional and structural elements can be introduced to exceed the primary amino acid composition. PTMs impact key biological and physiological processes including cell signaling, metabolism, protein degradation and influences interactions with other macromolecules. However, characterization of the structural and functional signatures of modified proteins has been historically limited. Since defects in PTMs are linked to numerous disorders and diseases, PTMs and their modifying enzymes are considered as potential drug targets. This has fueled new initiatives to determine how PTMs affect protein structure and function. In this review, I summarize some of the major, well-studied protein PTMs and related drug targets. Since PTMs are widely used for therapeutic targets or disease markers, highlighting structural changes after PTM provides new frontiers in understanding the detailed mechanism and related drug developments.