Adaptive mutability of colorectal cancers in response to targeted therapies

Bioinspired nanomedicines for the management of osteosarcoma: Recent progress and perspectives

Osteosarcoma (OS) is the most prevalent malignant primary bone tumor, predominantly affecting children and young adults between the ages of 11 and 20. OS presents huge challenges in treatment because of its aggressive nature and high metastatic potential. Chemotherapeutic drugs have attracted considerable interest for the treatment of OS, but they suffer from poor targeting, low bioavailability, severe side effects, and the multi-drug resistance acquired by the tumor. Therefore, it is imperative to develop novel therapeutic tactics that can improve OS outcomes while minimizing toxicity. Bioinspired nanoparticles, designed through exploiting or simulating the biological structures and processes, provide promising strategies for the treatment of OS. In this review, we elaborate on the biological properties and biomedical applications of state-of-the-art bioinspired nanoparticles, including cell membrane-based nanoparticles, exosome-based nanoparticles, protein template-based nanoparticles, and peptide template-based nanoparticles for the management of OS.

Identifying active and inhibitor-resistant MGMT variants for gene therapy

O6-methylguanine-DNA methyltransferase (MGMT) reverses alkylating-agent-induced methylation by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) at the O6 position of guanine. MGMT is irreversibly inhibited by O6-benzylguanine (O6BG), while the Pro140Lys (P140K) variant is resistant. Combining the use of O6BG/BCNU with gene transfer of MGMT P140K into hematopoietic stem cells (HSCs) has enabled in vivo enrichment of gene-modified HSCs for therapeutic effect in preclinical studies. However, the P140K substitution cannot reliably be made using currently available gene-editing approaches. Identifying functional MGMT variants that are resistant to inhibitors and amenable to gene editing would enable in vivo enrichment of HSCs edited at both MGMT and a therapeutic locus. We used computational analyses to select putative variants and generated a library of MGMT variant-expressing plasmids (pMGMTs). For our functional screen, we treated MGMT-deficient U251 cells with O6BG and co-transfected them with pMGMT together with a plasmid cocktail including a fluorescent host cell reactivation reporter plasmid (mPlum_O6MeG) for MGMT activity. Flow cytometric analysis of MGMT activity identified active and O6BG-resistant MGMT variants. Treatment with a second MGMT inhibitor, PaTrin-2, confirmed these results. We also found MGMT variants that are detectable in the general population and tumors to be active and O6BG sensitive. Taken together, our findings establish a functional database for MGMT variants and a cell-based platform for screening DNA-repair proteins for unknown functional properties.

HR eye & MMR eye: one-day assessment of DNA repair-defective tumors eligible for targeted therapy

Homologous recombination (HR) and mismatch repair (MMR) act as guardians of the human genome, and defects in HR or MMR are causative in at least a quarter of all malignant tumors. Although these DNA repair-deficient tumors are eligible for effective targeted therapies, fully reliable diagnostic strategies based on functional assay have yet to be established, potentially limiting safe and proper application of the molecular targeted drugs. Here we show that transient transfection of artificial DNA substrates enables ultrarapid detection of HR and MMR. This finding led us to develop a diagnostic strategy that can determine the cellular HR/MMR status within one day without the need for control cells or tissues. Notably, the accuracy of this method allowed the discovery of a pathogenic RAD51D mutation, which was missed by existing companion diagnostic tests. Our methods, termed HR eye and MMR eye, are applicable to frozen tumor tissues and roughly predict the response to therapy. Overall, the findings presented here could pave the way for accurately assessing malignant tumors with functional defects in HR or MMR, a step forward in accelerating precision medicine.

PRMT5 Inhibitor Synergizes with Chemotherapy to Induce Resembling Mismatch Repair Deficiency and Enhance Anti-TIGIT Therapy in Microsatellite-Stable Colorectal Cancer

Microsatellite stable (MSS) colorectal cancer (CRC) is considered an "immune-cold" tumor, accounting for ≈85% of all CRC cases. The overall response rate to chemotherapy combined with immune checkpoint inhibitors in MSS CRC is typically less than 10%. The specific mechanism that enhances chemotherapy sensitivity and mediated immunogenicity renders MSS CRC more responsive to immunotherapy remains elusive. Experiments in this study identify a DNA damage repair-related epigenetic gene, protein arginine methyltransferase 5 (PRMT5), whose inhibition enhances Irinotecan (CPT-11) sensitivity and synergistically induces a postmeiotic segregation increased 2 (PMS2)-deficient-like state, leading to the release of cytosolic double-stranded DNA. This activates the cyclic GMP-AMP synthase (cGAS)-stimulator of the IFN gene (STING) signaling pathway, thereby enhancing anti-tumor immunotherapy through dendritic cell-T cell-dependent functions. Importantly, combining the epigenetic anti-tumor drug GSK3326595 with CPT-11 significantly upregulates the immune receptor tyrosine-based inhibitory motif (TIGIT) level on CD8+ T cells and subsequently demonstrates impressive anti-tumor efficacy in vivo when additional anti-TIGIT is included. Collectively, this study reveals the crucial role of PRMT5 blockade combined with CPT-11 in inducing a mismatch repair deficiency-like state and provides a novel triple-drug combination therapy strategy as a potential treatment for patients with MSS CRC.

Five-Gene Expression Signature Associated With Acquired FOLFIRI Resistance and Survival in Metastatic Colorectal Cancer

FOLFIRI, a combination of folinic acid, 5-fluorouracil, and irinotecan, is one of the recommended first-line chemotherapeutic treatments for metastatic colorectal cancer. Unfortunately, acquired FOLFIRI resistance represents a common obstacle in the treatment of metastatic colorectal cancer patients. Thus, we aimed to identify mechanisms, gene alterations, and gene expression signatures contributing to acquired FOLFIRI resistance by mimicking this problem in a cell culture model and subsequent translation in clinical data sets. Three FOLFIRI-resistant colorectal cancer (CRC) cell lines were established by continuous FOLFIRI treatment. Comparative mutation screening (161 genes) and transcriptomics (pathway and differential expression analyses) were performed in parental and resistant cells. Data reconciliation was performed in GSE62322, a clinical FOLFIRI responder data set (intrinsic resistance). Relapse-free survival (RFS) associations of identified differentially expressed genes and potential gene signatures were investigated in 8 clinical CRC data sets. No mutual genetic alterations were found in FOLFIRI-resistant derivatives. Resistant cell lines displayed activation of mitogen-activated protein kinase, immune response, and epithelial-mesenchymal transition pathways. Twelve differentially expressed genes, significantly differentially expressed in at least 2 of the 3 resistant cell lines, were identified. Comparison with GSE62322 and subsequent survival analyses revealed a 5-gene FOLFIRI signature comprised of CAV2, TNC, TACSTD2, SERPINE2, and PERP that was associated with RFS in multiple data sets including the cancer genome atlas CRC (hazard ratio [HR] =2.634, P = 4.53 × 10-6), in pooled samples of all data sets (all stages [N = 1981]: HR = 1.852, P = 6.44 × 10-13; stage IV [N = 260]: HR = 2.462, P = 5.22 × 10-9). A multivariate Cox regression analysis identified the 5-gene signature as an independent prognostic factor in the cancer genome atlas data set (HR = 1.89, P = .0202). Our analyses revealed a 5-gene FOLFIRI resistance signature associated with RFS that may help predict FOLFIRI resistance and thus avoid unnecessary ineffective treatment. Signature members might also represent targets to fight FOLFIRI resistance.

Gut microbiota-lncRNA/circRNA crosstalk: implications for different diseases

The gut microbiota features an abundance of diverse microorganisms and represents an important component of human physiology and metabolic homeostasis, indicating their roles in a wide array of physiological and pathological processes in the host. Maintaining balance in the gut microbiota is critical for normal functionality as microbial dysbiosis can lead to the occurrence and development of diseases through various mechanisms. Long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) are non-coding RNAs that perform important regulatory functions for many processes. Furthermore, the gut microbiota and lncRNAs/circRNAs are known to interact in a range of both physiological and pathological activities. In this article, we review existing research relevant to the interaction between the gut microbiota and lncRNAs/circRNAs and investigate the role of their crosstalk in the pathogenesis of different diseases. Studies have shown that, the gut microbiota can target lncRNAs ENO1-IT1, BFAL1, and LINC00152 to regulate colorectal cancer development via various signaling pathways. In addition, the gut microbiota can influence mental diseases and lung tumor metastasis by modulating circRNAs such as circNF1-419, circ_0001239, circHIPK2 and mmu_circ_0000730. These findings provide a theoretical basis for disease prevention and treatment and suggest that gut microbiota-lncRNA/circRNA crosstalk has high clinical value.

Antibacterial compounds against non-growing and intracellular bacteria

Slow- and non-growing bacterial populations, along with intracellular pathogens, often evade standard antibacterial treatments and are linked to persistent and recurrent infections. This necessitates the development of therapies specifically targeting nonproliferating bacteria. To identify compounds active against non-growing uropathogenic Escherichia coli (UPEC) we performed a drug-repurposing screen of 6454 approved drugs and drug candidates. Using dilution-regrowth assays, we identified 39 compounds that either kill non-growing UPEC or delay its regrowth post-treatment. The hits include fluoroquinolones, macrolides, rifamycins, biguanide disinfectants, a pleuromutilin, and anti-cancer agents. Twenty-nine of the hits have not previously been recognized as active against non-growing bacteria. The hits were further tested against non-growing Pseudomonas aeruginosa and Staphylococcus aureus. Ten compounds - solithromycin, rifabutin, mitomycin C, and seven fluoroquinolones-have strong bactericidal activity against non-growing P. aeruginosa, killing >4 log10 of bacteria at 2.5 µM. Solithromycin, valnemulin, evofosfamide, and satraplatin are unique in their ability to selectively target non-growing bacteria, exhibiting poor efficacy against growing bacteria. Finally, 31 hit compounds inhibit the growth of intracellular Shigella flexneri in a human enterocyte infection model, indicating their ability to permeate the cytoplasm of host cells. The identified compounds hold potential for treating persistent infections, warranting further comparative studies with current standard-of-care antibiotics.

Subclonal response heterogeneity to define cancer organoid therapeutic sensitivity

Tumor heterogeneity is predicted to confer inferior clinical outcomes with precision-based strategies, however, modeling heterogeneity in a manner that still represents the tumor of origin remains a formidable challenge. Sequencing technologies are limited in their ability to identify rare subclonal populations and predict response to treatments for patients. Patient-derived organotypic cultures have significantly improved the modeling of cancer biology by faithfully representing the molecular features of primary malignant tissues. Patient-derived cancer organoid (PCO) cultures contain subclonal populations with the potential to recapitulate heterogeneity, although treatment response assessments commonly ignore diversity in the molecular profile or treatment response. Here, we demonstrate the advantage of evaluating individual PCO heterogeneity to enhance the sensitivity of these assays for predicting clinical response. Additionally, organoid subcultures identify subclonal populations with altered treatment response. Finally, dose escalation studies of PCOs to targeted anti-EGFR therapy are utilized which reveal divergent pathway expression when compared to pretreatment cultures. Overall, these studies demonstrate the importance of population-based organoid response assessments, the use of PCOs to identify molecular heterogeneity not observed with bulk tumor sequencing, and PCO heterogeneity for understanding therapeutic resistance mechanisms.

Association between oxidative balance score and all-cause and cancer-specific mortality among cancer survivors

Background

The Oxidative Balance Score (OBS) represents a novel metric for assessing systemic oxidative stress, where elevated scores reflect increased antioxidant exposure. This study aims to explore the association between OBS and all-cause and cancer-specific mortality among cancer survivors.

Methods

An observational cohort study was conducted involving 4099 cancer survivors, utilizing data obtained from the National Health and Nutrition Examination Survey (NHANES) covering the years 1999 to 2018. The endpoints were established by cross-referencing data with the National Death Index (NDI). The OBS was developed based on dietary and lifestyle factors. Cox proportional hazards regression models were employed to examine the relationship between OBS and mortality risks. Restricted cubic spline was utilized to evaluate whether OBS exhibited a nonlinear association with the risk of death. Furthermore, Kaplan-Meier survival curves were generated to assess cumulative survival differences across various OBS outcomes.

Results

Over an average follow-up of 84.00 months, 1481 (26.29%) participants died, including 484 (8.9%) who died from cancer. In the fully adjusted model, multivariable Cox regression revealed that each unit increase in OBS was linked to a 1.8% decrease in all-cause mortality risk (HR 0.982, 95%CI 0.972-0.991) and a 2.6% decrease in cancer-specific mortality risk (HR 0.974, 95%CI 0.958-0.991). In the context of all-cause mortality, the risk of death was found to be significantly lower in quartiles Q2, Q3 and Q4 when compared to the OBS in quartile Q1. The hazard ratios (HRs) and 95% confidence intervals (CIs) for Q2, Q3 and Q4 were as follows: Q2 (HR 0.833, 95%CI 0.707-0.981), Q3 (HR 0.789, 95%CI 0.650-0.958) and Q4 (HR 0.699, 95%CI 0.579-0.844). Regarding cancer-specific mortality, the HRs and 95%CIs for Q2, Q3 and Q4 in comparison to Q1 were as follows: Q2 (HR 0.663, 95%CI 0.505-0.869), Q3 (HR 0.688, 95%CI 0.488-0.969) and Q4 (HR 0.595, 95%CI 0.435-0.815). Similar associations were noted when the dietary and lifestyle components of the OBS were analyzed separately.

Conclusion

The findings indicate that higher levels of OBS are associated with a decrease in all-cause and cancer-specific mortality among cancer survivors. Our findings may contribute to the refinement of lifestyle intervention recommendations for this population.

Antigenic cancer persister cells survive direct T cell attack

Drug-tolerant persister cancer cells were first reported fifteen years ago as a quiescent, reversible cell state which tolerates unattenuated cytotoxic drug stress. It remains unknown whether a similar phenomenon contributes to immune evasion. Here we report a persister state which survives weeks of direct cytotoxic T lymphocyte (CTL) attack. In contrast to previously known immune evasion mechanisms that avoid immune attack, antigenic persister cells robustly activate CTLs which deliver Granzyme B, secrete IFNγ, and induce tryptophan starvation resulting in apoptosis initiation. Instead of dying, persister cells paradoxically leverage apoptotic caspase activity to avoid inflammatory death. Furthermore, persister cells acquire mutations and epigenetic changes which enable outgrowth of CTL-resistant cells. Persister cell features are enriched in inflamed tumors which regressed during immunotherapy in vivo and in surgically resected human melanoma tissue under immune stress ex vivo. These findings reveal a persister cell state which is a barrier to immune-mediated tumor clearance.

Deep profiling of gene expression across 18 human cancers

Clinical and biological information in large datasets of gene expression across cancers could be tapped with unsupervised deep learning. However, difficulties associated with biological interpretability and methodological robustness have made this impractical. Here we describe an unsupervised deep-learning framework for the generation of low-dimensional latent spaces for gene-expression data from 50,211 transcriptomes across 18 human cancers. The framework, which we named DeepProfile, outperformed dimensionality-reduction methods with respect to biological interpretability and allowed us to unveil that genes that are universally important in defining latent spaces across cancer types control immune cell activation, whereas cancer-type-specific genes and pathways define molecular disease subtypes. By linking latent variables in DeepProfile to secondary characteristics of tumours, we discovered that mutation burden is closely associated with the expression of cell-cycle-related genes, and that the activity of biological pathways for DNA-mismatch repair and MHC class II antigen presentation are consistently associated with patient survival. We also found that tumour-associated macrophages are a source of survival-correlated MHC class II transcripts. Unsupervised learning can facilitate the discovery of biological insight from gene-expression data.

Tumour-wide RNA splicing aberrations generate actionable public neoantigens

T cell-based immunotherapies hold promise in treating cancer by leveraging the immune system's recognition of cancer-specific antigens1. However, their efficacy is limited in tumours with few somatic mutations and substantial intratumoural heterogeneity2-4. Here we introduce a previously uncharacterized class of tumour-wide public neoantigens originating from RNA splicing aberrations in diverse cancer types. We identified T cell receptor clones capable of recognizing and targeting neoantigens derived from aberrant splicing in GNAS and RPL22. In cases with multi-site biopsies, we detected the tumour-wide expression of the GNAS neojunction in glioma, mesothelioma, prostate cancer and liver cancer. These neoantigens are endogenously generated and presented by tumour cells under physiologic conditions and are sufficient to trigger cancer cell eradication by neoantigen-specific CD8+ T cells. Moreover, our study highlights a role for dysregulated splicing factor expression in specific cancer types, leading to recurrent patterns of neojunction upregulation. These findings establish a molecular basis for T cell-based immunotherapies addressing the challenges of intratumoural heterogeneity.

Spatial immune heterogeneity in a mouse tumor model after immunotherapy

Cancer immunotherapy is increasingly used in clinical practice, but its success rate is reduced by tumor escape from the immune system. This may be due to the genetic instability of tumor cells, which allows them to adapt to the immune response and leads to intratumoral immune heterogeneity. The study investigated spatial immune heterogeneity in the tumor microenvironment and its possible drivers in a mouse model of tumors induced by human papillomaviruses (HPV) following immunotherapy. Gene expression was determined by RNA sequencing and mutations by whole exome sequencing. A comparison of different tumor areas revealed heterogeneity in immune cell infiltration, gene expression, and mutation composition. While the mean numbers of mutations with every impact on gene expression or protein function were comparable in treated and control tumors, mutations with high or moderate impact were increased after immunotherapy. The genes mutated in treated tumors were significantly enriched in genes associated with ECM metabolism, degradation, and interactions, HPV infection and carcinogenesis, and immune processes such as antigen processing and presentation, Toll-like receptor signaling, and cytokine production. Gene expression analysis of DNA damage and repair factors revealed that immunotherapy upregulated Apobec1 and Apobec3 genes and downregulated genes related to homologous recombination and translesion synthesis. In conclusion, this study describes the intratumoral immune heterogeneity, that could lead to tumor immune escape, and suggests the potential mechanisms involved.

Phosphorylation of SIRT7 by ATM causes DNA mismatch repair downregulation and adaptive mutability during chemotherapy

Drug resistance significantly limits the efficacy of chemotherapy. The DNA mismatch repair (MMR) system maintains genomic stability by correcting DNA errors. During DNA-damaging treatments, cancer cells transiently increase their adaptive mutability, also known as microsatellite instability (MSI), to evade therapeutic pressure through MMR downregulation, conferring drug resistance. However, an understanding of the underlying mechanisms of MMR protein downregulation under DNA-damaging drugs remains limited. Our study reveals a negative correlation between SIRT7 protein levels and MMR core protein MSH2 levels in cervical and lung cancer tissues. SIRT7 destabilizes MSH2, promoting MSI and mutagenesis. Molecularly, DNA damage triggers ATM kinase-dependent phosphorylation and subcellular redistribution of SIRT7. Phosphorylated SIRT7 interacts with and deacetylates MSH2, impairing MMR, and inducing MSI and drug resistance. Our findings suggest that SIRT7 drives MMR downregulation under therapeutic stress and that ATM-dependent phosphorylation of SIRT7 may serve as a predictive biomarker for chemotherapeutic efficacy and a target for cancer treatment.

The homologous recombination factors BRCA2 and PALB2 interplay with mismatch repair pathways to maintain centromere stability and cell viability

Centromeres are crucial for chromosome segregation but are vulnerable to breakage and recombination due to their repetitive DNA. The mechanisms protecting centromeres from these instabilities remain incompletely understood. This study investigates the role of the homologous recombination (HR) mediators BRCA2 and PALB2 in centromere stability. We find that BRCA2, but not PALB2, is essential for maintaining a human artificial chromosome. In native chromosomes, BRCA2 ensures CENP-A occupancy and prevents DNA fragility at centromeres. Conversely, PALB2 does not affect CENP-A, whereas its depletion increases centromeric DNA breaks in non-cancerous cells only. Interestingly, depleting the mismatch repair (MMR) factor MLH1 masks centromere fragility caused by BRCA2 or PALB2 loss, suggesting that MLH1 contributes to DNA instability when BRCA2 or PALB2 is absent. However, cells deficient in both BRCA2/PALB2 and MLH1 have reduced survival. These results highlight a critical balance between HR and MMR factors in preserving centromere integrity and cell viability.

Early tolerance and late persistence as alternative drug responses in cancer

Bacteria withstand antibiotic treatment through three alternative mechanisms: resistance, persistence or tolerance. While resistance and persistence have been described, whether drug-induced tolerance exists in cancer cells remains largely unknown. Here, we show that human cancer cells elicit a tolerant response when exposed to commonly used chemotherapy regimens, propelled by the pervasive activation of autophagy, leading to the comprehensive activation of DNA damage repair pathways. After prolonged drug exposure, such tolerant responses morph into persistence, whereby the increased DNA damage repair is entirely reversed. The central regulator of mitophagy PINK1 drives this reduction in DNA repair via the cytoplasmic relocalization of the cell identity master HNF4A, thus hampering HNF4A transcriptional activation of DNA repair genes. We conclude that exposing cancer cells to relevant standard-of-care antitumour therapies induces a pervasive drug-induced tolerant response that might be broadly exploited to increase the impact of first-line, adjuvant treatments and debulking in advanced cancers.

The Selective WEE1 Inhibitor Azenosertib Shows Synergistic Antitumor Activity with KRASG12C Inhibitors in Preclinical Models

SIGNIFICANCE

Resistance to KRASG12C inhibitors is a growing clinical concern. The synergistic interaction observed between azenosertib and multiple KRASG12C inhibitors could result in deeper and more durable responses.

Digestive cancers: mechanisms, therapeutics and management

Cancers of the digestive system are major contributors to global cancer-associated morbidity and mortality, accounting for 35% of annual cases of cancer deaths. The etiologies, molecular features, and therapeutic management of these cancer entities are highly heterogeneous and complex. Over the last decade, genomic and functional studies have provided unprecedented insights into the biology of digestive cancers, identifying genetic drivers of tumor progression and key interaction points of tumor cells with the immune system. This knowledge is continuously translated into novel treatment concepts and targets, which are dynamically reshaping the therapeutic landscape of these tumors. In this review, we provide a concise overview of the etiology and molecular pathology of the six most common cancers of the digestive system, including esophageal, gastric, biliary tract, pancreatic, hepatocellular, and colorectal cancers. We comprehensively describe the current stage-dependent pharmacological management of these malignancies, including chemo-, targeted, and immunotherapy. For each cancer entity, we provide an overview of recent therapeutic advancements and research progress. Finally, we describe how novel insights into tumor heterogeneity and immune evasion deepen our understanding of therapy resistance and provide an outlook on innovative therapeutic strategies that will shape the future management of digestive cancers, including CAR-T cell therapy, novel antibody-drug conjugates and targeted therapies.

Identification of Immune Infiltration-Associated CC Motif Chemokine Ligands as Biomarkers and Targets for Colorectal Cancer Prevention and Immunotherapy

Colorectal cancer (CRC) is the third most common cancer globally, with limited effective biomarkers and sensitive therapeutic targets. An increasing number of studies have highlighted the critical role of tumor microenvironment (TME) imbalances, particularly immune escape due to impaired chemokine-mediated trafficking, in tumorigenesis and progression. Notably, CC chemokines (CCLs) have been shown to either promote or inhibit angiogenesis, metastasis, and immune responses in tumors, thereby influencing cancer development and patient outcomes. However, the diagnostic and prognostic significance of CCLs in CRC remains unclear. In this study, multiple online tools for bioinformatics analyses were utilized. The findings revealed that the mRNA expression levels of CCL3, CCL4, and CCL26 were significantly elevated in CRC tissues compared to normal tissues, whereas CCL2, CCL5, CCL11, CCL21, and CCL28 mRNA levels were markedly downregulated. Additionally, dysregulation of CCL4, CCL5, and CCL21 was strongly associated with clinical staging, and elevated levels of CCL4, CCL11, and CCL28 were linked to significantly prolonged survival in CRC patients. Functional enrichment analysis indicated that the cellular roles of CCLs were predominantly associated with the chemokine, Wnt, and Toll-like receptor signaling pathways, as well as protein kinase activity. Furthermore, transcriptional regulation of most CCLs involved RELA and NFKB1. Key downstream targets included members of the SRC family of tyrosine kinases (HCK, LYN, and LCK), serine/threonine kinases (ATR and ATM), and others such as CSNK1G2, NEK2, and CDK2. Moreover, CCLs (CCL2, CCL3, CCL4, CCL5, CCL11, CCL21, and CCL28) exhibited strong correlations with major infiltration-related immune cells, including B cells, CD8+ T cells, CD4+ T cells, macrophages, neutrophils, and dendritic cells. In conclusion, our study provides novel insights into the potential utility of CCLs as biomarkers and therapeutic targets for CRC prevention and immunotherapy.

Gefitinib Reverses PD-L1-Mediated Immunosuppression Induced by Long-term Glutamine Blockade in Bladder Cancer

Glutamine is a major energy source for tumor cells, and blocking glutamine metabolism is being investigated as a promising strategy for cancer therapy. However, the antitumor effect of glutamine blockade in bladder cancer remains unclear, necessitating further investigation. In this study, we demonstrated that glutamine metabolism was involved in the malignant progression of bladder cancer. Treatment with the glutamine antagonist 6-diazo-5-oxo-L-norleucine (DON) inhibited the growth of bladder cancer cells in vitro in several ways. In addition, we observed inhibition of tumor growth in bladder cancer-bearing mice by using JHU083, a prodrug that was designed to prevent DON-induced toxicity. However, the antitumor immune effect of T cells changed from activation to inhibition as the administrated time extended. We found that both in vitro treatment with DON and in vivo prolonged administration of JHU083 led to the upregulation of PD-L1 in bladder cancer cells. Mechanistically, glutamine blockade upregulated PD-L1 expression in bladder cancer cells by accumulating reactive oxygen species, subsequently activating the EGFR/ERK/C-Jun signaling pathway. Combination treatment of JHU083 and gefitinib reversed the upregulation of PD-L1 in bladder cancer cells induced by prolonged glutamine blockade, resulting in the alleviation of T-cell immunosuppression and a significant improvement in therapeutic outcome. These preclinical findings show promise for glutamine metabolism targeting as a viable therapeutic strategy for bladder cancer, with the potential for further enhancement through combined treatment with gefitinib.

Late-line options for patients with metastatic colorectal cancer: a review and evidence-based algorithm

Over the past few years, several novel systemic treatments have emerged for patients with treatment-refractory metastatic colorectal cancer, thus making selection of the most effective later-line therapy a challenge for medical oncologists. Over the past decade, regorafenib and trifluridine-tipiracil were the only available drugs and often provided limited clinical benefit compared to best supportive care. Results from subsequent practice-changing trials opened several novel therapeutic avenues, both for unselected patients (such as trifluridine-tipiracil plus bevacizumab or fruquintinib) and for subgroups defined by the presence of actionable alterations in their tumours (such as HER2-targeted therapies or KRASG12C inhibitors) or with no acquired mechanisms of resistance to the previously received targeted agents in circulating tumour DNA (such as retreatment with anti-EGFR antibodies). In this Review, we provide a comprehensive overview of advances in the field over the past few years and offer a practical perspective on translation of the most relevant results into the daily management of patients with metastatic colorectal cancer using an evidence-based algorithm. Finally, we discuss some of the most appealing ongoing areas of research and highlight approaches with the potential to further expand the therapeutic armamentarium.

Ongoing Clinical Trials and Future Research Scenarios of Circulating Tumor DNA for the Treatment of Metastatic Colorectal Cancer

Liquid biopsy using circulating tumor DNA (ctDNA) has emerged as a minimally invasive, timely approach to provide molecular diagnosis and monitor tumor evolution in patients with cancer. Since the molecular landscape of metastatic colorectal cancer (mCRC) is substantially heterogeneous and dynamic over space and time, ctDNA holds significant advantages as a biomarker for this disease. Numerous studies have demonstrated that ctDNA broadly recapitulates the molecular profile of the primary tumor and metastases, and have mainly focused on the genotyping of RAS and BRAF, that is propaedeutic for anti-EGFR treatment selection. However, ctDNA soon broadened its scope towards the assessment of early tumor response, as well as the identification of drug resistance biomarkers to drive potential molecular actionability. In this review article, we provide an overview of the current state-of-the-art of this methodology and its applications, focusing on ongoing clinical trials that employ ctDNA to prospectively guide treatment in patients with mCRC.

Advancing cancer drug development with mechanistic mathematical modeling: bridging the gap between theory and practice

Quantitative predictive modeling of cancer growth, progression, and individual response to therapy is a rapidly growing field. Researchers from mathematical modeling, systems biology, pharmaceutical industry, and regulatory bodies, are collaboratively working on predictive models that could be applied for drug development and, ultimately, the clinical management of cancer patients. A plethora of modeling paradigms and approaches have emerged, making it challenging to compile a comprehensive review across all subdisciplines. It is therefore critical to gauge fundamental design aspects against requirements, and weigh opportunities and limitations of the different model types. In this review, we discuss three fundamental types of cancer models: space-structured models, ecological models, and immune system focused models. For each type, it is our goal to illustrate which mechanisms contribute to variability and heterogeneity in cancer growth and response, so that the appropriate architecture and complexity of a new model becomes clearer. We present the main features addressed by each of the three exemplary modeling types through a subjective collection of literature and illustrative exercises to facilitate inspiration and exchange, with a focus on providing a didactic rather than exhaustive overview. We close by imagining a future multi-scale model design to impact critical decisions in oncology drug development.

Colorectal cancer with BRAF V600E mutation: Trends in immune checkpoint inhibitor treatment

Colorectal cancer (CRC) with BRAF V600E mutation presents a formidable scientific and clinical challenge due to its aggressive nature and poor response to standard therapeutic approaches. BRAF V600E mutation-induced conspicuous activation of the MAPK pathway contributes to the relentless tumor progression. Nevertheless, the efficacy of multi-targeted MAPK pathway inhibition remains suboptimal in clinical practice. Patients with high microsatellite instability (MSI-H) have shown favorable results with immune checkpoint inhibitors (ICIs). The combination of the MAPK pathway inhibition with ICIs has recently emerged as a promising regimen to improve clinical outcomes in the microsatellite stable (MSS) subgroup of BRAF V600E-mutant metastatic CRC patients. In this review, we elucidate the unique tumor biology of BRAF V600E-mutant CRC, with a particular focus on the immune features underlying the rationale for ICI treatments in the MSI-H and MSS subpopulations, then highlight the trends in clinical trials of the ICI therapy for BRAF V600E-mutant metastatic CRC.

Comparing baseline VAF in circulating tumor DNA and tumor tissues predicting prognosis of patients with colorectal cancer liver metastases after curative resection

INTRODUCTION

The prognostic value of baseline variant allele frequency (VAF) in circulating tumor DNA (ctDNA) of colorectal cancer liver metastases (CRLM) patients after curative resection was rarely investigated.

METHODS

A single-center prospective study was performed to investigate the prognostic impact of baseline VAF in ctDNA and matched tumor tissues of CRLM patients after curative resection between May 2019 and May 2021 by the Illumina NovoSeq 6000 platform. The relationship of the tumor burden score (TBS) and the VAF in ctDNA and matched tumor tissues was evaluated by the Pearson correlation method. The survival curves of recurrence-free survival (RFS) and overall survival (OS) were plotted. Factors associated with RFS were calculated using Cox regression analysis, and an integrated prognostic model using significant baseline variables was proposed.

RESULTS

There were 121 patients with baseline ctDNA and matched tumor tissues enrolled in the study. A total of 417 mutations spanning 20 genes were identified in baseline tumor tissues of 119/121 (98.3 %) cases. The overall mutations in tumor tissues were completely covered by ctDNA in 52 of 121(43.0 %) patients. Baseline VAF in ctDNA but not in tumor tissues was significantly correlated to TBS of CRLM (R = 0.36, p < 0.001). Significantly longer RFS but not OS was observed in patients with lower VAF in ctDNA compared to those with higher one (p < 0.001 and p = 0.33 respectively). Multivariate Cox regression analysis showed higher VAF in baseline ctDNA was an independent risk factor for RFS. An integrated prognostic model including baseline metastasis location and VAF in ctDNA outperformed the traditional CRS model in predicting RFS.

CONCLUSION

Baseline VAF in ctDNA but not in tumor tissues influenced RFS of CRLM patients after curative resection.

Characterisation of APOBEC3B-Mediated RNA editing in breast cancer cells reveals regulatory roles of NEAT1 and MALAT1 lncRNAs

RNA editing is a crucial post-transcriptional process that influences gene expression and increases the diversity of the proteome as a result of amino acid substitution. Recently, the APOBEC3 family has emerged as a significant player in this mechanism, with APOBEC3A (A3A) having prominent roles in base editing during immune and stress responses. APOBEC3B (A3B), another family member, has gained attention for its potential role in generating genomic DNA mutations in breast cancer. In this study, we coupled an inducible expression cell model with a novel methodology for identifying differential variants in RNA (DVRs) to map A3B-mediated RNA editing sites in a breast cancer cell model. Our findings indicate that A3B engages in selective RNA editing including targeting NEAT1 and MALAT1 long non-coding RNAs that are often highly expressed in tumour cells. Notably, the binding of these RNAs sequesters A3B and suppresses global A3B activity against RNA and DNA. Release of A3B from NEAT1/MALAT1 resulted in increased A3B activity at the expense of A3A activity suggesting a regulatory feedback loop between the two family members. This research substantially advances our understanding of A3B's role in RNA editing, its mechanistic underpinnings, and its potential relevance in the pathogenesis of breast cancer.

Drug tolerance and persistence in bacteria, fungi and cancer cells: Role of non-genetic heterogeneity

A common feature of bacterial, fungal and cancer cell populations upon treatment is the presence of tolerant and persistent cells able to survive, and sometimes grow, even in the presence of usually inhibitory or lethal drug concentrations, driven by non-genetic differences among individual cells in a population. Here we review and compare data obtained on drug survival in bacteria, fungi and cancer cells to unravel common characteristics and cellular pathways, and to point their singularities. This comparative work also allows to cross-fertilize ideas across fields. We particularly focus on the role of gene expression variability in the emergence of cell-cell non-genetic heterogeneity because it represents a possible common basic molecular process at the origin of most persistence phenomena and could be monitored and tuned to help improve therapeutic interventions.

Lactylation in cancer: Mechanisms in tumour biology and therapeutic potentials

Lactylation, a recently identified form of protein post-translational modification (PTM), has emerged as a key player in cancer biology. The Warburg effect, a hallmark of tumour metabolism, underscores the significance of lactylation in cancer progression. By regulating gene transcription and protein function, lactylation facilitates metabolic reprogramming, enabling tumours to adapt to nutrient limitations and sustain rapid growth. Over the past decade, extensive research has revealed the intricate regulatory network underlying lactylation in tumours. Large-scale sequencing and machine learning have confirmed the widespread occurrence of lactylation sites across the tumour proteome. Targeting lactylation enzymes or metabolic pathways has demonstrated promising anti-tumour effects, highlighting the therapeutic potential of this modification. This review comprehensively explores the mechanisms of lactylation in cancer cells and the tumour microenvironment. We expound on the application of advanced omics technologies for target identification and data modelling within the lactylation field. Additionally, we summarise existing anti-lactylation drugs and discuss their clinical implications. By providing a comprehensive overview of recent advancements, this review aims to stimulate innovative research and accelerate the translation of lactylation-based therapies into clinical practice. KEY POINTS: Lactylation significantly influences tumour metabolism and gene regulation, contributing to cancer progression. Advanced sequencing and machine learning reveal widespread lactylation sites in tumours. Targeting lactylation enzymes shows promise in enhancing anti-tumour drug efficacy and overcoming chemotherapy resistance. This review outlines the clinical implications and future research directions of lactylation in oncology.

Molecular profiling of BRAF-V600E-mutant metastatic colorectal cancer in the phase 3 BEACON CRC trial

The BEACON CRC study demonstrated that encorafenib (Enco)+cetuximab (Cetux)±binimetinib (Bini) significantly improved overall survival (OS) versus Cetux + chemotherapy in previously treated patients with BRAF-V600E-mutant mCRC, providing the basis for the approval of the Enco+Cetux regimen in the United States and the European Union. A greater understanding of biomarkers predictive of response to Enco+Cetux±Bini treatment is of clinical relevance. In this prespecified, exploratory biomarker analysis of the BEACON CRC study, we characterize genomic and transcriptomic correlates of clinical outcomes and acquired resistance mechanisms through integrated clinical and molecular analysis, including whole-exome and -transcriptome tissue sequencing and circulating tumor DNA genomic profiling. Tumors with higher immune signatures showed a trend towards increased OS benefit with Enco+Bini+Cetux. RAS, MAP2K1 and MET alterations were most commonly acquired with Enco+Cetux±Bini, and more frequent in patients with a high baseline cell-cycle gene signature; baseline TP53 mutation was associated with acquired MET amplification. Acquired mutations were subclonal and polyclonal, with evidence of increased tumor mutation rate with Enco+Cetux±Bini and mutational signatures (SBS17a/b). These findings support treatment with Enco+Cetux±Bini for patients with BRAF-V600E-mutant mCRC and provide insights into the biology of response and resistance to MAPK-pathway-targeted therapy. ClinicalTrials.gov registration: NCT02928224.

A deep profile of gene expression across 18 human cancers

Clinically and biologically valuable information may reside untapped in large cancer gene expression data sets. Deep unsupervised learning has the potential to extract this information with unprecedented efficacy but has thus far been hampered by a lack of biological interpretability and robustness. Here, we present DeepProfile, a comprehensive framework that addresses current challenges in applying unsupervised deep learning to gene expression profiles. We use DeepProfile to learn low-dimensional latent spaces for 18 human cancers from 50,211 transcriptomes. DeepProfile outperforms existing dimensionality reduction methods with respect to biological interpretability. Using DeepProfile interpretability methods, we show that genes that are universally important in defining the latent spaces across all cancer types control immune cell activation, while cancer type-specific genes and pathways define molecular disease subtypes. By linking DeepProfile latent variables to secondary tumor characteristics, we discover that tumor mutation burden is closely associated with the expression of cell cycle-related genes. DNA mismatch repair and MHC class II antigen presentation pathway expression, on the other hand, are consistently associated with patient survival. We validate these results through Kaplan-Meier analyses and nominate tumor-associated macrophages as an important source of survival-correlated MHC class II transcripts. Our results illustrate the power of unsupervised deep learning for discovery of cancer biology from existing gene expression data.

Overcoming Therapy Resistance in Colorectal Cancer: Targeting the Rac1 Signaling Pathway as a Potential Therapeutic Approach

Colorectal cancer (CRC) is the third most commonly diagnosed type of cancer worldwide and is responsible for numerous deaths. 5-fluorouracil (5-FU) is an effective chemotherapy drug commonly used in the treatment of CRC, either as monotherapy or in combination with other drugs. However, half of CRC cases are resistant to 5-FU-based therapies. To contribute to the understanding of the mechanisms underlying CRC resistance or recurrence after 5-FU-based therapies, we performed a comprehensive study integrating in silico, in vitro, and in vivo approaches. We identified differentially expressed genes and enrichment of pathways associated with recurrence after 5-FU-based therapies. Using these bioinformatics data as a starting point, we selected a group of drugs that restored 5-FU sensitivity to 5-FU resistant cells. Interestingly, treatment with the novel Rac1 inhibitor, 1A-116, reversed morphological changes associated with 5-FU resistance.. Moreover, our in vivo studies have shown that 1A-116 affected tumor growth and the development of metastasis. All our data allowed us to postulate that targeting Rac1 represents a promising avenue for the development of new treatments for patients with CRC resistant to 5-FU-based therapies.

Cancer drug-tolerant persister cells: from biological questions to clinical opportunities

The emergence of drug resistance is the most substantial challenge to the effectiveness of anticancer therapies. Orthogonal approaches have revealed that a subset of cells, known as drug-tolerant 'persister' (DTP) cells, have a prominent role in drug resistance. Although long recognized in bacterial populations which have acquired resistance to antibiotics, the presence of DTPs in various cancer types has come to light only in the past two decades, yet several aspects of their biology remain enigmatic. Here, we delve into the biological characteristics of DTPs and explore potential strategies for tracking and targeting them. Recent findings suggest that DTPs exhibit remarkable plasticity, being capable of transitioning between different cellular states, resulting in distinct DTP phenotypes within a single tumour. However, defining the biological features of DTPs has been challenging, partly due to the complex interplay between clonal dynamics and tissue-specific factors influencing their phenotype. Moreover, the interactions between DTPs and the tumour microenvironment, including their potential to evade immune surveillance, remain to be discovered. Finally, the mechanisms underlying DTP-derived drug resistance and their correlation with clinical outcomes remain poorly understood. This Roadmap aims to provide a comprehensive overview of the field of DTPs, encompassing past achievements and current endeavours in elucidating their biology. We also discuss the prospect of future advancements in technologies in helping to unveil the features of DTPs and propose novel therapeutic strategies that could lead to their eradication.

A protracted war against cancer drug resistance

Currently, even the most effective anti-cancer therapies are often limited by the development of drug resistance and tumor relapse, which is a major challenge facing current cancer research. A deep understanding of the molecular and biochemical bases of drug efficacy that can help predict the clinical drug resistance, coupled with the evolution of systematic genomic and proteomic technologies, have facilitated studies identifying and elucidating the underlying mechanisms. In this review, we focus on several important issues on cancer drug resistance and provide a framework for understanding the common ways by which cancers develop resistance to therapeutic agents. With the increasing arsenal of novel anticancer agents and techniques, there are now unprecedented opportunities to understand and overcome drug resistance. The proteolysis targeting chimera (PROTAC) technology, immunotherapy, nanomedicine, and real-time monitoring of drug response all provide effective approaches for combating drug resistance. In addition to the advancement of therapeutic technologies, the revolution of treatment concept is also of great importance. We can take advantage of the interplay between drug sensitive and resistant subclones for combating cancer. However, there remains a long way to go in the protracted war against cancer drug resistance.

A bispecific antibody targeting EGFR and AXL delays resistance to osimertinib

Activating EGFR (epidermal growth factor receptor) mutations can be inhibited by specific tyrosine kinase inhibitors (TKIs), which have changed the landscape of lung cancer therapy. However, due to secondary mutations and bypass receptors, such as AXL (AXL receptor tyrosine kinase), drug resistance eventually emerges in most patients treated with the first-, second-, or third-generation TKIs (e.g., osimertinib). To inhibit AXL and resistance to osimertinib, we compare two anti-AXL drugs, an antibody (mAb654) and a TKI (bemcentinib). While no pair of osimertinib and an anti-AXL drug is able to prevent relapses, triplets combining osimertinib, cetuximab (an anti-EGFR antibody), and either anti-AXL drug are initially effective. However, longer monitoring uncovers superiority of the mAb654-containing triplet, possibly due to induction of receptor endocytosis, activation of immune mechanisms, or disabling intrinsic mutators. Hence, we constructed a bispecific antibody that engages both AXL and EGFR. When combined with osimertinib, the bispecific antibody consistently inhibits tumor relapses, which warrants clinical trials.

Novel ERBB2 Variant Potentially Associated with Resistance against Anti-HER2 Monoclonal Antibody-Based Therapy in ERBB2-Amplified Metastatic Colorectal Cancer

PURPOSE

HER2-targeted therapies in ERBB2-amplified metastatic colorectal cancer (mCRC) are effective; however, a notable portion of patients do not respond to treatment, and secondary resistance occurs in most patients receiving these treatments. The purpose of this study was to investigate determinants of treatment efficacy and resistance in patients with ERBB2-amplified mCRC who received HER2-targeted therapy by analyzing multiomics data.

EXPERIMENTAL DESIGN

We investigated genomic data from a nationwide large cancer genomic screening project, the SCRUM-Japan project. We analyzed paired genome and transcriptome data of tissue and genomic data of ctDNA collected pre- and postprogression in patients enrolled in the related trial, TRIUMPH, in ERBB2-amplified mCRC.

RESULTS

In 155 patients with ERBB2-amplified solid tumors who received HER2-targeted therapy based on the SCRUM-Japan project, the objective response rate was 50%, 51%, and 35% in ERBB2 wild-type, variant of unknown significance, and pathogenic variant groups, respectively. In the paired genome and transcriptome data analyses in TRIUMPH, we identified the novel splicing-associated variant c.644-66_-2del in one of the 11 patients with paired whole-exome sequencing and whole-transcriptome sequencing data sets, which lacks the binding domain of pertuzumab, in progressed metastatic tumor as a variant with potential pathogenicity. The time-course ctDNA analysis detected c.644-66_-2del as an acquired variant.

CONCLUSIONS

This study highlighted the importance of ERBB2 genomic status when evaluating the efficacy of HER2-targeted therapies in ERBB2-amplified mCRC. The identification of a novel splicing-associated variant may provide insights into potential mechanisms of treatment resistance. Furthermore, we demonstrated the utility of ctDNA to follow the acquired genomic status of mCRC tumors.

Human aneuploid cells depend on the RAF/MEK/ERK pathway for overcoming increased DNA damage

Aneuploidy is a hallmark of human cancer, yet the molecular mechanisms to cope with aneuploidy-induced cellular stresses remain largely unknown. Here, we induce chromosome mis-segregation in non-transformed RPE1-hTERT cells and derive multiple stable clones with various degrees of aneuploidy. We perform a systematic genomic, transcriptomic and proteomic profiling of 6 isogenic clones, using whole-exome DNA, mRNA and miRNA sequencing, as well as proteomics. Concomitantly, we functionally interrogate their cellular vulnerabilities, using genome-wide CRISPR/Cas9 and large-scale drug screens. Aneuploid clones activate the DNA damage response and are more resistant to further DNA damage induction. Aneuploid cells also exhibit elevated RAF/MEK/ERK pathway activity and are more sensitive to clinically-relevant drugs targeting this pathway, and in particular to CRAF inhibition. Importantly, CRAF and MEK inhibition sensitize aneuploid cells to DNA damage-inducing chemotherapies and to PARP inhibitors. We validate these results in human cancer cell lines. Moreover, resistance of cancer patients to olaparib is associated with high levels of RAF/MEK/ERK signaling, specifically in highly-aneuploid tumors. Overall, our study provides a comprehensive resource for genetically-matched karyotypically-stable cells of various aneuploidy states, and reveals a therapeutically-relevant cellular dependency of aneuploid cells.

L3MBTL1, a polycomb protein, promotes Osimertinib acquired resistance through epigenetic regulation of DNA damage response in lung adenocarcinoma

Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (EGFR-TKI) approved for patients with EGFR T790M resistance mutations as first- or second-line treatment of EGFR-positive patients. Resistance to Osimertinib will inevitably develop, and the underlying mechanisms are largely unknown. In this study, we discovered that acquired resistance to Osimertinib is associated with abnormal DNA damage response (DDR) in lung adenocarcinoma cells. We discovered that the polycomb protein Lethal(3) Malignant Brain Tumor-Like Protein 1 (L3MBTL1) regulates chromatin structure, thereby contributing to DDR and Osimertinib resistance. EGFR oncogene inhibition reduced L3MBTL1 ubiquitination while stabilizing its expression in Osimertinib-resistant cells. L3MBTL1 reduction and treatment with Osimertinib significantly inhibited DDR and proliferation of Osimertinib-resistant lung cancer cells in vitro and in vivo. L3MBTL1 binds throughout the genome and plays an important role in EGFR-TKI resistance. It also competes with 53BP1 for H4K20Me2 and inhibits the development of drug resistance in Osimertinib-resistant lung cancer cells in vitro and in vivo. Our findings suggest that L3MBTL1 inhibition is a novel approach to overcoming EGFR-TKI-acquired resistance.

mTORC2-driven chromatin cGAS mediates chemoresistance through epigenetic reprogramming in colorectal cancer

Cyclic GMP-AMP synthase (cGAS), a cytosolic DNA sensor that initiates a STING-dependent innate immune response, binds tightly to chromatin, where its catalytic activity is inhibited; however, mechanisms underlying cGAS recruitment to chromatin and functions of chromatin-bound cGAS (ccGAS) remain unclear. Here we show that mTORC2-mediated phosphorylation of human cGAS serine 37 promotes its chromatin localization in colorectal cancer cells, regulating cell growth and drug resistance independently of STING. We discovered that ccGAS recruits the SWI/SNF complex at specific chromatin regions, modifying expression of genes linked to glutaminolysis and DNA replication. Although ccGAS depletion inhibited cell growth, it induced chemoresistance to fluorouracil treatment in vitro and in vivo. Moreover, blocking kidney-type glutaminase, a downstream ccGAS target, overcame chemoresistance caused by ccGAS loss. Thus, ccGAS coordinates colorectal cancer plasticity and acquired chemoresistance through epigenetic patterning. Targeting both mTORC2-ccGAS and glutaminase provides a promising strategy to eliminate quiescent resistant cancer cells.

Targeting therapy-persistent residual disease

Disease relapse driven by acquired drug resistance limits the effectiveness of most systemic anti-cancer agents. Targeting persistent cancer cells in residual disease before relapse has emerged as a potential strategy for enhancing the efficacy and the durability of current therapies. However, barriers remain to implementing persister-directed approaches in the clinic. This Perspective discusses current preclinical and clinical complexities and outlines key steps toward the development of clinical strategies that target therapy-persistent residual disease.

Drug tolerant persister cell plasticity in cancer: A revolutionary strategy for more effective anticancer therapies

Non-genetic mechanisms have recently emerged as important drivers of anticancer drug resistance. Among these, the drug tolerant persister (DTP) cell phenotype is attracting more and more attention and giving a predominant non-genetic role in cancer therapy resistance. The DTP phenotype is characterized by a quiescent or slow-cell-cycle reversible state of the cancer cell subpopulation and inert specialization to stimuli, which tolerates anticancer drug exposure to some extent through the interaction of multiple underlying mechanisms and recovering growth and proliferation after drug withdrawal, ultimately leading to treatment resistance and cancer recurrence. Therefore, targeting DTP cells is anticipated to provide new treatment opportunities for cancer patients, although our current knowledge of these DTP cells in treatment resistance remains limited. In this review, we provide a comprehensive overview of the formation characteristics and underlying drug tolerant mechanisms of DTP cells, investigate the potential drugs for DTP (including preclinical drugs, novel use for old drugs, and natural products) based on different medicine models, and discuss the necessity and feasibility of anti-DTP therapy, related application forms, and future issues that will need to be addressed to advance this emerging field towards clinical applications. Nonetheless, understanding the novel functions of DTP cells may enable us to develop new more effective anticancer therapy and improve clinical outcomes for cancer patients.

The Potential Links between lncRNAs and Drug Tolerance in Lung Adenocarcinoma

Lung cancer patients treated with targeted therapies frequently respond well but invariably relapse due to the development of drug resistance. Drug resistance is in part mediated by a subset of cancer cells termed "drug-tolerant persisters" (DTPs), which enter a dormant, slow-cycling state that enables them to survive drug exposure. DTPs also exhibit stem cell-like characteristics, broad epigenetic reprogramming, altered metabolism, and a mutagenic phenotype mediated by adaptive mutability. While several studies have characterised the transcriptional changes that lead to the altered phenotypes exhibited in DTPs, these studies have focused predominantly on protein coding changes. As long non-coding RNAs (lncRNAs) are also implicated in the phenotypes altered in DTPs, it is likely that they play a role in the biology of drug tolerance. In this review, we outline how lncRNAs may contribute to the key characteristics of DTPs, their potential roles in tolerance to targeted therapies, and the emergence of genetic resistance in lung adenocarcinoma.

Adaptive use of error-prone DNA polymerases provides flexibility in genome replication during tumorigenesis

Human cells possess many different polymerase enzymes, which collaborate in conducting DNA replication and genome maintenance to ensure faithful duplication of genetic material. Each polymerase performs a specialized role, together providing a balance of accuracy and flexibility to the replication process. Perturbed replication increases the requirement for flexibility to ensure duplication of the entire genome. Flexibility is provided via the use of error-prone polymerases, which maintain the progression of challenged DNA replication at the expense of mutagenesis, an enabling characteristic of cancer. This review describes our recent understanding of mechanisms that alter the usage of polymerases during tumorigenesis and examines the implications of this for cell survival and tumor progression. Although expression levels of polymerases are often misregulated in cancers, this does not necessarily alter polymerase usage since an additional regulatory step may govern the use of these enzymes. We therefore also examine how the regulatory mechanisms of DNA polymerases, such as Rad18-mediated PCNA ubiquitylation, may impact the functionalization of error-prone polymerases to tolerate oncogene-induced replication stress. Crucially, it is becoming increasingly evident that cancer cells utilize error-prone polymerases to sustain ongoing replication in response to oncogenic mutations which inactivate key DNA replication and repair pathways, such as BRCA deficiency. This accelerates mutagenesis and confers chemoresistance, but also presents a dependency that can potentially be exploited by therapeutics.

Transmissible cancers, the genomes that do not melt down

Evolutionary theory predicts that the accumulation of deleterious mutations in asexually reproducing organisms should lead to genomic decay. Clonally reproducing cell lines, i.e., transmissible cancers, when cells are transmitted as allografts/xenografts, break these rules and survive for centuries and millennia. The currently known 11 transmissible cancer lineages occur in dogs (canine venereal tumour disease), in Tasmanian devils (devil facial tumor diseases, DFT1 and DFT2), and in bivalves (bivalve transmissible neoplasia). Despite the mutation loads of these cell lines being much higher than observed in human cancers, they have not been eliminated in space and time. Here, we provide potential explanations for how these fascinating cell lines may have overcome the fitness decline due to the progressive accumulation of deleterious mutations and propose that the high mutation load may carry an indirect positive fitness outcome. We offer ideas on how these host-pathogen systems could be used to answer outstanding questions in evolutionary biology. The recent studies on the evolution of these clonal pathogens reveal key mechanistic insight into transmissible cancer genomes, information that is essential for future studies investigating how these contagious cancer cell lines can repeatedly evade immune recognition, evolve, and survive in the landscape of highly diverse hosts.

Homopolymer switches mediate adaptive mutability in mismatch repair-deficient colorectal cancer

Mismatch repair (MMR)-deficient cancer evolves through the stepwise erosion of coding homopolymers in target genes. Curiously, the MMR genes MutS homolog 6 (MSH6) and MutS homolog 3 (MSH3) also contain coding homopolymers, and these are frequent mutational targets in MMR-deficient cancers. The impact of incremental MMR mutations on MMR-deficient cancer evolution is unknown. Here we show that microsatellite instability modulates DNA repair by toggling hypermutable mononucleotide homopolymer runs in MSH6 and MSH3 through stochastic frameshift switching. Spontaneous mutation and reversion modulate subclonal mutation rate, mutation bias and HLA and neoantigen diversity. Patient-derived organoids corroborate these observations and show that MMR homopolymer sequences drift back into reading frame in the absence of immune selection, suggesting a fitness cost of elevated mutation rates. Combined experimental and simulation studies demonstrate that subclonal immune selection favors incremental MMR mutations. Overall, our data demonstrate that MMR-deficient colorectal cancers fuel intratumor heterogeneity by adapting subclonal mutation rate and diversity to immune selection.

REV1 coordinates a multi-faceted tolerance response to DNA alkylation damage and prevents chromosome shattering in Drosophila melanogaster

When replication forks encounter damaged DNA, cells utilize damage tolerance mechanisms to allow replication to proceed. These include translesion synthesis at the fork, postreplication gap filling, and template switching via fork reversal or homologous recombination. The extent to which these different damage tolerance mechanisms are utilized depends on cell, tissue, and developmental context-specific cues, the last two of which are poorly understood. To address this gap, we have investigated damage tolerance responses in Drosophila melanogaster. We report that tolerance of DNA alkylation damage in rapidly dividing larval tissues depends heavily on translesion synthesis. Furthermore, we show that the REV1 protein plays a multi-faceted role in damage tolerance in Drosophila. Larvae lacking REV1 are hypersensitive to methyl methanesulfonate (MMS) and have highly elevated levels of γ-H2Av (Drosophila γ-H2AX) foci and chromosome aberrations in MMS-treated tissues. Loss of the REV1 C-terminal domain (CTD), which recruits multiple translesion polymerases to damage sites, sensitizes flies to MMS. In the absence of the REV1 CTD, DNA polymerases eta and zeta become critical for MMS tolerance. In addition, flies lacking REV3, the catalytic subunit of polymerase zeta, require the deoxycytidyl transferase activity of REV1 to tolerate MMS. Together, our results demonstrate that Drosophila prioritize the use of multiple translesion polymerases to tolerate alkylation damage and highlight the critical role of REV1 in the coordination of this response to prevent genome instability.

Molecular and Clinical Determinants of Acquired Resistance and Treatment Duration for Targeted Therapies in Colorectal Cancer

PURPOSE

Targeted therapies have improved outcomes for patients with metastatic colorectal cancer, but their impact is limited by rapid emergence of resistance. We hypothesized that an understanding of the underlying genetic mechanisms and intrinsic tumor features that mediate resistance to therapy will guide new therapeutic strategies and ultimately allow the prevention of resistance.

EXPERIMENTAL DESIGN

We assembled a series of 52 patients with paired pretreatment and progression samples who received therapy targeting EGFR (n = 17), BRAF V600E (n = 17), KRAS G12C (n = 15), or amplified HER2 (n = 3) to identify molecular and clinical factors associated with time on treatment (TOT).

RESULTS

All patients stopped treatment for progression and TOT did not vary by oncogenic driver (P = 0.5). Baseline disease burden (≥3 vs. <3 sites, P = 0.02), the presence of hepatic metastases (P = 0.02), and gene amplification on baseline tissue (P = 0.03) were each associated with shorter TOT. We found evidence of chromosomal instability (CIN) at progression in patients with baseline MAPK pathway amplifications and those with acquired gene amplifications. At resistance, copy-number changes (P = 0.008) and high number (≥5) of acquired alterations (P = 0.04) were associated with shorter TOT. Patients with hepatic metastases demonstrated both higher number of emergent alterations at resistance and enrichment of mutations involving receptor tyrosine kinases.

CONCLUSIONS

Our genomic analysis suggests that high baseline CIN or effective induction of enhanced mutagenesis on targeted therapy underlies rapid progression. Longer response appears to result from a progressive acquisition of genomic or chromosomal instability in the underlying cancer or from the chance event of a new resistance alteration.

Colorectal cancer: a comprehensive review of carcinogenesis, diagnosis, and novel strategies for classified treatments

Colorectal cancer is the third most common and the second deadliest cancer worldwide. To date, colorectal cancer becomes one of the most important challenges of the health system in many countries. Since the clinical symptoms of this cancer appear in the final stages of the disease and there is a significant golden time between the formation of polyps and the onset of cancer, early diagnosis can play a significant role in reducing mortality. Today, in addition to colonoscopy, minimally invasive methods such as liquid biopsy have received much attention. The treatment of this complex disease has been mostly based on traditional treatments including surgery, radiotherapy, and chemotherapy; the high mortality rate indicates a lack of success for current treatment methods. Moreover, disease recurrence is another problem of traditional treatments. Recently, new approaches such as targeted therapy, immunotherapy, and nanomedicine have opened new doors for cancer treatment, some of which have already entered the market, and many methods have shown promising results in clinical trials. The success of immunotherapy in the treatment of refractory disease, the introduction of these methods into neoadjuvant therapy, and the successful results in tumor shrinkage without surgery have made immunotherapy a tough competitor for conventional treatments. It seems that the combination of those methods with such targeted therapies will go through promising changes in the future of colorectal cancer treatment.

Polymorphisms of DNA Repair Genes in Thyroid Cancer

The incidence of thyroid cancer, one of the most common forms of endocrine cancer, is increasing rapidly worldwide in developed and developing countries. Various risk factors can increase susceptibility to thyroid cancer, but particular emphasis is put on the role of DNA repair genes, which have a significant impact on genome stability. Polymorphisms of these genes can increase the risk of developing thyroid cancer by affecting their function. In this article, we present a concise review on the most common polymorphisms of selected DNA repair genes that may influence the risk of thyroid cancer. We point out significant differences in the frequency of these polymorphisms between various populations and their potential relationship with susceptibility to the disease. A more complete understanding of these differences may lead to the development of effective prevention strategies and targeted therapies for thyroid cancer. Simultaneously, there is a need for further research on the role of polymorphisms of previously uninvestigated DNA repair genes in the context of thyroid cancer, which may contribute to filling the knowledge gaps on this subject.