Side Chain Investigation of Imidazopyridazine as a Hinge Binder for Targeting Actionable Mutations of RET Kinase

Actionable mutations of RET kinase have been identified as oncogenic drivers of solid tumors, including thyroid cancer, metastatic colorectal cancer, and nonsmall cell lung cancer. Although multikinase inhibitors and RET selective inhibitors are used to treat patients with RET alterations, there is insufficient research addressing certain issues: which actionable mutations arise from these therapies, how to improve the clinical response rate to RET inhibitors, and how to design new inhibitors to overcome drug resistance. Therefore, the development of sophisticated tool compounds is required to investigate the molecular mechanisms of actionable mutations and to develop breakthrough therapeutics for different RET alterations. Herein, we present our investigation into the side chains of imidazopyridazine hinge binders that are capable of inducing protein-ligand interaction patterns from the gatekeeper to the waterfront regions. Extending the substituents at the second and sixth positions enhanced the IC50 up to < 0.5 nM for diverse RET alterations.

Evaluation of the gene fusion landscape in early onset sporadic rectal cancer reveals association with chromatin architecture and genome stability

Gene fusions represent a distinct class of structural variants identified frequently in cancer genomes across cancer types. Several gene fusions exhibit gain of oncogenic function and thus have been the focus of development of efficient targeted therapies. However, investigation of fusion landscape in early-onset sporadic rectal cancer, a poorly studied colorectal cancer subtype prevalent in developing countries, has not been performed. Here, we present a comprehensive landscape of gene fusions in EOSRC and CRC using patient derived tumor samples and data from The Cancer Genome Atlas, respectively. Gene Ontology analysis revealed enrichment of unique biological process terms associated with 5'- and 3'- fusion partner genes. Extensive network analysis highlighted genes exhibiting significant promiscuity in fusion formation and their association with chromosome fragile sites. Investigation of fusion formation in the context of global chromatin architecture unraveled a novel mode of gene activation that arose from fusion between genes located in orthogonal chromatin compartments. The study provides novel evidence linking fusions to genome stability and architecture and unearthed a hitherto unidentified mode of gene activation in cancer.

Pathologic Evaluation of Therapeutic Biomarkers in Colorectal Adenocarcinoma

Molecular testing is an essential component of the pathologic evaluation of colorectal carcinoma providing diagnostic, prognostic, and predictive therapeutic information. Mismatch repair status evaluation is required for all tumors. Advanced and metastatic tumors also require determination of tumor mutational burden, KRAS, NRAS, and BRAF mutation status, ERBB2 amplification status, and NTRK and RET gene rearrangement status to guide therapy. Multiple assays, including immunohistochemistry, microsatellite instability testing, MLH1 promoter methylation, and next-generation sequencing, are typically needed. Pathologists must be aware of these requirements to optimally triage tissue. Advances in colorectal cancer molecular diagnostics will continue to drive refinements in colorectal cancer personalized therapy.

A Metastatic Pulmonary Sarcomatoid Carcinoma Patient Harboring KIF5B-RET Fusion Responds to First-Line Pralsetinib Treatment: A Case Report

Pulmonary sarcomatoid carcinoma (PSC) is a rare subtype of non-small cell lung cancer (NSCLC), accounting for about 1% of cases. These tumors are characterized by their high malignancy and frequent resistance to chemotherapy, resulting in a worse prognosis compared to other NSCLC subtypes. Currently, there is no established therapeutic strategy for PSC. Recent advancements in targeted therapies have led to the development of ret proto-oncogene (RET) inhibitors, such as selpercatinib and pralsetinib, which have been approved for the treatment of RET fusion-positive NSCLC patients. Despite their effectiveness in RET fusion-positive NSCLC is observed, the efficacy of these inhibitors in PSC remains unclear. In this context, we present a case of metastatic PSC harboring de novo KIF5B-RET fusion. The patient responded to first-line trametinib treatment. These findings suggest that RET inhibitors could be a potential treatment option for metastatic PSC patients with RET fusion-positive tumors.

Update on Emerging Therapies for Advanced Colorectal Cancer

Colorectal cancer (CRC) is the third most common malignancy worldwide. It is projected to increase by 3.2 million new cases and account for 1.6 million deaths by 2040. Mortality is largely due to limited treatment options for patients who present with advanced disease. Thus, the development of effective and tolerable therapies is crucial. Chemotherapy has been the backbone of systemic treatment of advanced CRC, but utility has been limited because of invariable resistance to therapy, narrow mechanisms of action, and unfavorable toxicity profile. Tumors that are mismatch repair-deficient have demonstrated remarkable response to immune checkpoint inhibitor therapy. However, most CRC tumors are mismatch repair-proficient and represent an unmet medical need. Although ERBB2 amplification occurs only in a few cases, it is associated with left-sided tumors and a higher incidence of brain metastasis. Numerous combinations of HER2 inhibitors have demonstrated efficacy, and antibody-drug conjugates against HER2 represent innovative strategies in this area. The KRAS protein has been classically considered undruggable. Fortunately, new agents targeting KRAS G12C mutation represent a paradigm shift in the management of affected patients and could lead the advancement in drug development for the more common KRAS mutations. Furthermore, aberrant DNA damage response is present in 15%-20% of CRCs, and emerging innovative combinations with poly (ADP-ribose) polymerase (PARP) inhibitors could improve the current therapeutic landscape. Multiple novel biomarker-driven approaches in the management of patients with advanced CRC tumors are reviewed in this article.

RET Proto-Oncogene-Not Such an Obvious Starting Point in Cancer Therapy

Mutations and fusions of RET (rearranged during transfection) gene are detected in a few common types of tumors including thyroid or non-small cells lung cancers. Multiple kinase inhibitors (MKIs) do not show spectacular effectiveness in patients with RET-altered tumors. Hence, recently, two novel RET-specific inhibitors were registered in the US and in Europe. Selpercatinib and pralsetinib showed high efficacy in clinical trials, with fewer adverse effects, in comparison to previously used MKIs. However, the effectiveness of these new drugs may be reduced by the emergence of resistance mutations in RET gene and activation of different activating signaling pathways. This review presents the function of the normal RET receptor, types of molecular disturbances of the RET gene in patients with various cancers, methods of detecting these abnormalities, and the effectiveness of modern anticancer therapies (ranging from immunotherapies, through MKIs, to RET-specific inhibitors).

Cullin-9/p53 mediates HNRNPC degradation to inhibit erastin-induced ferroptosis and is blocked by MDM2 inhibition in colorectal cancer

Colorectal cancer (CRC) is the leading cause of cancer associated death worldwide. Ferroptosis is a newly defined form of regulated cell death characterized by the accumulation of lipid hydroperoxides and exerts an increased attention for cancer treatment. However, little is known about ferroptosis in CRC. In this study, through whole genome sequencing and external differential differentiated expression analysis, we identify CUL9 as a novel important modulator for ferroptosis in CRC. Here we demonstrated that CUL9 can binds p53 to ubiquitylate heterogeneous nuclear ribonucleoprotein C for degradation. Overexpression of CUL9 increases resistance to erastin-induced ferroptosis. Then, we discovered this resistance was mediated by CUL9-HNRNPC-MATE1 negative loop, which can provide us with a novel target to overcome drug resistance to ferroptosis activators. Finally, we found that targeting MDM2 was developed as an effective strategy to destroy precious drug-resistant CRC cells.

Genomic profiles of Indonesian colorectal cancer patients

Background: Colorectal cancer (CRC) is one of the most commonly diagnosed cancers worldwide and genetic mutation plays a vital role in CRC development. A previous study has suggested that genetic alterations among Indonesian patients with CRC might differ from those known in developed countries. This study aimed to describe the genomic profiles of Indonesian patients with CRC. Methods: A total of 13 patients were recruited for this study from May to July 2019. Tissue samples were collected, and genomic DNA was extracted from the samples. AmpliSeq for Illumina Cancer HotSpot Panel v2 Next-generation sequencing was used for DNA sequencing and a genome analysis toolkit was used for local realignment around the discovered variants. Results: A total of 45 genes comprising 391 single nucleotide variants (SNVs) with a depth >10 were observed. The genes with the most variants were STK11, SMAD4, EGFR, and ERBB4 and the genes with the most non-synonymous variants were SMAD4, TP53, FGFR3, CDKN2A, and STK11. Genes and SNVs in at least 90% of all samples consisted of 43 genes comprising 286 variants. Genes with the most non-synonymous SNVs were EGFR, SMO, FGFR3, TP53, STK11, CDKN2A. Genes related to the chromosomal instability pathway, such as TP53, SMAD4, KRAS, and APC, are also found in the analysis. Conclusions: Our findings showed that all patients with CRC in this study had genetic mutations in the chromosomal instability pathway. Analysis of genetic mutation of Indonesian patients with CRC might be crucial for advanced targeted therapy and for better clinical outcomes.

Genomic profiles of Indonesian colorectal cancer patients

Background: Colorectal cancer (CRC) is one of the most commonly diagnosed cancers worldwide and genetic mutation plays a vital role in CRC development. A previous study has suggested that genetic alterations among Indonesian patients with CRC might differ from those known in developed countries. This study aimed to describe the genomic profiles of Indonesian patients with CRC. Methods: A total of 13 patients were recruited for this study from May to July 2019. Tissue samples were collected, and genomic DNA was extracted from the samples. AmpliSeq for Illumina Cancer HotSpot Panel v2 Next-generation sequencing was used for DNA sequencing and a genome analysis toolkit was used for local realignment around the discovered variants. Results: A total of 45 genes comprising 391 single nucleotide variants (SNVs) with a depth >10 were observed. The genes with the most variants were STK11, SMAD4, EGFR, and ERBB4 and the genes with the most non-synonymous variants were SMAD4, TP53, FGFR3, CDKN2A, and STK11. Genes and SNVs in at least 90% of all samples consisted of 43 genes comprising 286 variants. Genes with the most non-synonymous SNVs were EGFR, SMO, FGFR3, TP53, STK11, CDKN2A. Genes related to the chromosomal instability pathway, such as TP53, SMAD4, KRAS, and APC, are also found in the analysis. Conclusions: Our findings showed that all patients with CRC in this study had genetic mutations in the chromosomal instability pathway. Analysis of genetic mutation of Indonesian patients with CRC might be crucial for advanced targeted therapy and for better clinical outcomes.

Investigating natural compounds against oncogenic RET tyrosine kinase using pharmacoinformatic approaches for cancer therapeutics

Rearranged during transfection (RET) tyrosine kinase is a transmembrane receptor tyrosine kinase regulating vital aspects of cellular proliferation, differentiation, and survival. An outstanding challenge in designing protein kinase inhibitors is due to the development of drug resistance. The “gain of function” mutations in the RET gate-keeper residue, Val804, confers resistance to the majority of known RET inhibitors, including vandetanib. To curtail this resistance, researchers developed selpercatinib (LOXO-292) against the RET gate-keeper mutant forms – V804M and V804L. In the present in silico investigation, a receptor–ligand pharmacophore model was generated to identify small molecule inhibitors effective for wild-type (WT) as well as mutant RET kinase variants. The generated model was employed to screen 144 766 natural products (NPs) available in the ZINC database and the retrieved NPs were filtered for their drug-likeness. The resulting 2696 drug-like NPs were subjected to molecular docking with the RET WT kinase domain and a total of 27 molecules displayed better dock scores than the reference inhibitors – vandetanib and selpercatinib. From 27 NPs, an aggregate of 12 compounds demonstrated better binding free energy (BFE) scores than the reference inhibitors, towards RET. Thus, the 12 NPs were also subjected to docking, simulation, and BFE estimation towards the constructed gate-keeper RET mutant structures. The BFE calculations revealed 3 hits with better BFE scores than the reference inhibitors towards WT, V804M, and V804L RET variants. Thus, the scaffolds of hit compounds presented in this study could act as potent RET inhibitors and further provide insights for drug optimization targeting aberrant activation of RET signaling, specifically the mutation of gate-keeper residue – Val804.

Identification of natural product inhibitors against rearranged during transfection (RET) tyrosine kinase as cancer therapeutics using combination of in silico techniques.

Pharmacotherapy for unresectable metastatic colorectal cancer

INTRODUCTION

Unresectable metastatic colorectal cancer (mCRC) has a poor prognosis. Emerging treatment paradigms have improved outcomes in selected unresectable mCRC cases. Recent therapeutic advancements are due in part to a shift in trial designs. By examining CRC as a heterogeneous group of various tumor subtypes, researchers have identified molecular distinctions that have led to promising targets.

AREAS COVERED

Nineteen antineoplastic agents are included in the National Comprehensive Cancer Network guidelines for the palliative management of mCRC. However, not all patients will be candidates for each agent. New therapies for rare mCRC subtypes have emerged. Herein, the authors review these rare mCRC subtypes: microsatellite instability-high/deficient mismatch repair, BRAFV600E-mutant, and human epidermal growth factor receptor 2-positive tumors. Additionally, they provide an overview of unresectable mCRC management and future directions.

EXPERT OPINION

Treatment in the majority of mCRC patients (RAS wild-type or RAS-mutant, microsatellite instability-stable or -low/mismatch repair-proficient, BRAFV600E wild-type, or HER2-negative) needs further advancement and remains an unmet need. The authors believe that the key to identifying more breakthroughs in these mCRC patients is to continue to differentiate their tumors molecularly and clinically.

Landscape of Current Targeted Therapies for Advanced Colorectal Cancer

Colorectal cancer (CRC) is one of the most frequent and lethal cancer types worldwide. While surgery with chemotherapy and radiotherapy remains the only curative approach for localized CRC, for metastatic disease the therapeutic landscape has significantly evolved over the last years. Development and approval of novel targeted therapies, such as monoclonal antibodies against EGFR and VEGF, have significantly increased the median survival of patients with metastatic disease, with some trials reporting a benefit over 40 months. Increasing accessibility of high throughput sequencing has unraveled several new therapeutic targets. Actionable alterations, such as HER2 overexpression, BRAF mutations, and NTRK fusions, are currently available in metastatic disease, providing significant therapeutic opportunities for these patients, while new emerging agents, as immune checkpoint inhibitors, promise better treatment options in the near future. In this chapter, an overview of established and future CRC targeted therapies in the clinical setting is provided, as well as their mechanism of action, limitations, and future applicability.

Therapeutic Advances in the Management of Patients with Advanced RET Fusion-Positive Non-Small Cell Lung Cancer

OPINION STATEMENT

Screening for activating driver gene alterations at the time of diagnosis is the standard of care for advanced non-small cell lung cancer (NSCLC). Activating RET fusions are identified in approximately 1-2% of NSCLCs and have emerged as a targetable driver alteration. Selpercatinib and pralsetinib are RET-selective tyrosine kinase inhibitors (TKIs) with encouraging efficacy, intracranial activity, and tolerability that we recommend as first-line therapy. As with use of TKIs in other oncogene-addicted NSCLCs, development of acquired resistance is pervasive and should be specifically delineated through use of repeat tissue biopsy with genetic profiling at the time of disease progression. If an actionable resistance mechanism emerges for which there is a candidate targeted therapy, combination inhibition should be considered. Alternatively, or in the absence of such findings, platinum doublet chemotherapy or particularly platinum-pemetrexed therapy with or without bevacizumab demonstrates a moderate effect.We would not recommend the routine use of nonselective multi-targeted TKIs such as cabozantinib and vandetanib, which have modest activity but limited tolerability due to predictable off-target effects. Single-agent immunotherapy has minimal activity in RET fusion-positive NSCLC. The role of combination chemotherapy and immunotherapy requires further study but may be considered, particularly in the presence of an activating KRAS alteration. While further development of novel RET-selective TKIs may address common RET-specific resistance mutations, they will not have activity against off-target, RET-independent resistance mechanisms. This again highlights the importance of serial biopsy and next-generation sequencing for the rational choice of sequential therapy in RET fusion-positive NSCLC.

Comprehensive NGS Panel Validation for the Identification of Actionable Alterations in Adult Solid Tumors

The increasing identification of driver oncogenic alterations and progress of targeted therapies addresses the need of comprehensive alternatives to standard molecular methods. The translation into clinical practice of next-generation sequencing (NGS) panels is actually challenged by the compliance of high quality standards for clinical accreditation. Herein, we present the analytical and clinical feasibility study of a hybridization capture-based NGS panel (Action OncoKitDx) for the analysis of somatic mutations, copy number variants (CNVs), fusions, pharmacogenetic SNPs and Microsatellite Instability (MSI) determination in formalin-fixed paraffin-embedded (FFPE) tumor samples. A total of 64 samples were submitted to extensive analytical validation for the identification of previously known variants. An additional set of 166 tumor and patient-matched normal samples were sequenced to assess the clinical utility of the assay across different tumor types. The panel demonstrated good specificity, sensitivity, reproducibility, and repeatability for the identification of all biomarkers analyzed and the 5% limit of detection set was validated. Among the clinical cohorts, the assay revealed pathogenic genomic alterations in 97% of patient cases, and in 82.7%, at least one clinically relevant variant was detected. The validation of accuracy and robustness of this assay supports the Action OncoKitDx's utility in adult solid tumors.

Chasing the Target: New Phenomena of Resistance to Novel Selective RET Inhibitors in Lung Cancer. Updated Evidence and Future Perspectives

Simple Summary

REarranged during Transfection (RET) is an emerging target for several types of cancer, including non-small cell lung cancer (NSCLC). The recent U.S. FDA approval of pralsetinib and selpercatinib raises issues regarding the emergence of secondary mutations and amplifications involved in parallel signaling pathways and receptors, liable for resistance mechanisms. The aim of this review is to explore recent knowledge on RET resistance in NSCLC in pre-clinic and in clinical settings and accordingly, the state-of-the-art in new drugs or combination of drugs development.

Abstract

The potent, RET-selective tyrosine kinase inhibitors (TKIs) pralsetinib and selpercatinib, are effective against the RET V804L/M gatekeeper mutants, however, adaptive mutations that cause resistance at the solvent front RET G810 residue have been found, pointing to the need for the development of the next-generation of RET-specific TKIs. Also, as seen in EGFR- and ALK-driven NSCLC, the rising of the co-occurring amplifications of KRAS and MET could represent other escaping mechanisms from direct inhibition. In this review, we summarize actual knowledge on RET fusions, focusing on those involved in NSCLC, the results of main clinical trials of approved RET-inhibition drugs, with particular attention on recent published results of selective TKIs, and finally, pre-clinical evidence regarding resistance mechanisms and suggestion on hypothetical and feasible drugs combinations and strategies viable in the near future.

Multi-Omics Characterization of Inflammatory Bowel Disease-Induced Hyperplasia/Dysplasia in the Rag2-/-/Il10-/- Mouse Model

Epigenetic dysregulation is hypothesized to play a role in the observed association between inflammatory bowel disease (IBD) and colon tumor development. In the present work, DNA methylome, hydroxymethylome, and transcriptome analyses were conducted in proximal colon tissues harvested from the Helicobacter hepaticus (H. hepaticus)-infected murine model of IBD. Reduced representation bisulfite sequencing (RRBS) and oxidative RRBS (oxRRBS) analyses identified 1606 differentially methylated regions (DMR) and 3011 differentially hydroxymethylated regions (DhMR). These DMR/DhMR overlapped with genes that are associated with gastrointestinal disease, inflammatory disease, and cancer. RNA-seq revealed pronounced expression changes of a number of genes associated with inflammation and cancer. Several genes including Duox2, Tgm2, Cdhr5, and Hk2 exhibited changes in both DNA methylation/hydroxymethylation and gene expression levels. Overall, our results suggest that chronic inflammation triggers changes in methylation and hydroxymethylation patterns in the genome, altering the expression of key tumorigenesis genes and potentially contributing to the initiation of colorectal cancer.

Biomarker-guided therapy for colorectal cancer: strength in complexity

The number of molecularly stratified treatment options available to patients with colorectal cancer (CRC) is increasing, with a parallel rise in the use of biomarkers to guide prognostication and treatment decision-making. The increase in both the number of biomarkers and their use has resulted in a progressively complex situation, evident both from the extensive interactions between biomarkers and from their sometimes complex associations with patient prognosis and treatment benefit. Current and emerging biomarkers also reflect the genomic complexity of CRC, and include a wide range of aberrations such as point mutations, amplifications, fusions and hypermutator phenotypes, in addition to global gene expression subtypes. In this Review, we provide an overview of current and emerging clinically relevant biomarkers and their role in the management of patients with CRC, illustrating the intricacies of biomarker interactions and the growing treatment opportunities created by the availability of comprehensive molecular profiling.