Cellular mechanisms of tumour suppression by the retinoblastoma gene

DAF-18/PTEN protects LIN-35/Rb from CLP-1/CAPN-mediated cleavage to promote starvation resistance

Starvation resistance is a fundamental trait with profound influence on fitness and disease risk. DAF-18, the Caenorhabditis elegans ortholog of the tumor suppressor PTEN, promotes starvation resistance. PTEN is a dual phosphatase, and DAF-18 promotes starvation resistance as a lipid phosphatase by antagonizing insulin/IGF and PI3K signaling, activating the tumor suppressor DAF-16/FoxO. However, if or how DAF-18/PTEN protein-phosphatase activity promotes starvation resistance is unknown. Using genetic, genomic, bioinformatic, and biochemical approaches, we identified the C. elegans retinoblastoma/RB protein homolog, LIN-35/Rb, as a critical mediator of the effect of DAF-18/PTEN on starvation resistance. We show that DAF-18/PTEN protects LIN-35/Rb from cleavage by the μ-Calpain homolog CLP-1/CAPN, and that LIN-35/Rb together with the repressive DREAM complex promotes starvation resistance. We conclude that the tumor suppressors DAF-18/PTEN and LIN-35/Rb function in a linear pathway, with LIN-35/Rb and the rest of the DREAM complex functioning as a transcriptional effector of DAF-18/PTEN protein-phosphatase activity resulting in repression of germline gene expression. This work is significant for revealing a network of tumor suppressors that promote survival during cellular and developmental quiescence.

A unique spontaneously immortalised cell line from pig with enhanced adipogenic capacity

Cultivated meat promises to address some of the pressing challenges associated with large-scale production of animals for food. An important limitation to realising such promise is the lack of readily available cell lines that can be expanded robustly for scale-up culture while maintaining the capacity to differentiate into tissues of interest, namely fat and muscle. Here, we report a porcine mesenchymal stem cell line (FaTTy) which, uniquely, upon spontaneously immortalisation acquired enhanced adipogenic efficiency, close to 100%, that has now been maintained for over 200 population doublings. FaTTy is able to differentiate with high efficiency in both 2D and 3D contexts and produces mature adipocytes upon prolonged differentiation. Moreover, FaTTy adipocytes display fatty acid profiles largely similar to native pig fat but with higher monounsaturated-to-saturated ratios. FaTTy displays minor aneuploidy, characterised by lack of Y chromosome, and lacks typical genetic or functional properties of tumorigenic cells. These highly distinctive characteristics, together with its non-genetically modified nature, make FaTTy a very attractive, potentially game-changing resource for food manufacturing, and particularly cultivated meat.

Loss of VHL-mediated pRb regulation promotes clear cell renal cell carcinoma

The von Hippel-Lindau (VHL) tumor suppressor is a substrate-defining component of E3 ubiquitin ligase complexes that target cellular substrates for proteasome-mediated degradation. VHL inactivation by mutation or transcriptional silencing is observed in most sporadic cases of clear cell renal cell carcinoma (ccRCC). VHL loss in ccRCC leads to constitutive stabilization of E3 ligase substrates, including hypoxia inducible factor α (HIFα). HIFα stabilization upon VHL loss is known to contribute to ccRCC development through transactivation of hypoxia-responsive genes. HIF-independent VHL targets have been implicated in oncogenesis, although those mechanisms are less well-defined than for HIFα. Using proximity labeling to identify proteasomal-sensitive VHL interactors, we identified retinoblastoma protein (pRb) as a novel substrate of VHL. Mechanistically, VHL interacts with pRb in a proteasomal-sensitive manner, promoting its ubiquitin-mediated degradation. Concordantly, VHL-inactivation results in pRb hyperstabilization. Functionally, loss of pRb in ccRCC led to increased cell death, transcriptional changes, and loss of oncogenic properties in vitro and in vivo. We also show that downstream transcriptional changes induced by pRb hyperstabilization may contribute to ccRCC tumor development. Together, our findings reveal a novel VHL-related pathway which can be therapeutically targeted to inhibit ccRCC tumor development.

Current Trends in Messenger RNA Technology for Cancer Therapeutics

Messenger RNA (mRNA)-based therapy has revolutionized cancer research by enabling versatile delivery systems for therapeutic applications. The future of mRNA-based cancer therapies shows promise amidst challenges such as delivery efficiency, immunogenicity, and tumor heterogeneity. Recent progress has adapted various strategies such as design flexibility, scalable production, and targeted delivery capabilities to enhance the potential in personalized cancer therapy. Further research to optimize delivery for enhanced outcomes and efficacy in solid tumors is warranted. Therefore, we aim to explore the current landscape and future prospects of mRNA technology across various therapeutic platforms.

Stem Cells in Cancer: From Mechanisms to Therapeutic Strategies

Stem cells have emerged as a pivotal area of research in the field of oncology, offering new insights into the mechanisms of cancer initiation, progression, and resistance to therapy. This review provides a comprehensive overview of the role of stem cells in cancer, focusing on cancer stem cells (CSCs), their characteristics, and their implications for cancer therapy. We discuss the origin and identification of CSCs, their role in tumorigenesis, metastasis, and drug resistance, and the potential therapeutic strategies targeting CSCs. Additionally, we explore the use of normal stem cells in cancer therapy, focusing on their role in tissue regeneration and their use as delivery vehicles for anticancer agents. Finally, we highlight the challenges and future directions in stem cell research in cancer.

Proteogenomic discovery of RB1-defective phenocopy in cancer predicts disease outcome, response to treatment, and therapeutic targets

Genomic defects caused by truncating mutations or deletions in the Retinoblastoma tumor suppressor gene (RB1) are frequently observed in many cancer types leading to dysregulation of the RB pathway. Here, we propose an integrative proteogenomic approach that predicts cancers with dysregulation in the RB pathway. A subset of these cancers, which we term as "RBness," lack RB1 genomic defects and yet phenocopy the transcriptional profile of RB1-defective cancers. We report RBness as a pan-cancer phenomenon, associated with patient outcome and chemotherapy response in multiple cancer types, and predictive of CDK4/6 inhibitor response in estrogen-positive breast cancer. Using RNA interference and a CRISPR-Cas9 screen in isogenic models, we find that RBness cancers also phenocopy synthetic lethal vulnerabilities of cells with RB1 genomic defects. In summary, our findings suggest that dysregulation of the RB pathway in cancers lacking RB1 genomic defects provides a molecular rationale for how these cancers could be treated.

Exploring the Genetic Orchestra of Cancer: The Interplay Between Oncogenes and Tumor-Suppressor Genes

Cancer is complex because of the critical imbalance in genetic regulation as characterized by both the overexpression of oncogenes (OGs), mainly through mutations, amplifications, and translocations, and the inactivation of tumor-suppressor genes (TSGs), which entail the preservation of genomic integrity by inducing apoptosis to counter the malignant growth. Reviewing the intricate molecular interplay between OGs and TSGs draws attention to their cell cycle, apoptosis, and cancer metabolism regulation. In the present review, we discuss seminal discoveries, such as Knudson's two-hit hypothesis, which framed the field's understanding of cancer genetics, leading to the next breakthroughs with next-generation sequencing and epigenetic profiling, revealing novel insights into OG and TSG dysregulation with opportunities for targeted therapy. The key pathways, such as MAPK/ERK, PI3K/AKT/mTOR, and Wnt/β-catenin, are presented in the context of tumor progression. Importantly, we further highlighted the advances in therapeutic strategies, including inhibitors of KRAS and MYC and restoration of TSG function, despite which mechanisms of resistance and tumor heterogeneity pose daunting challenges. A high-level understanding of interactions between OG-TSGs forms the basis for effective, personalized cancer treatment-something to strive for in better clinical outcomes. This synthesis should integrate foundational biology with translation and, in this case, contribute to the ongoing effort against cancer.

Molecular Mechanisms in the Transformation from Indolent to Aggressive B Cell Malignancies

Histological transformation (HT) into aggressive lymphoma is a turning point in a significant fraction of patients affected by indolent lymphoproliferative neoplasms, namely, chronic lymphocytic leukemia (CLL), follicular lymphoma (FL), marginal zone lymphomas (MZLs), and lymphoplasmacytic lymphoma (LPL) [...].

Structural and functional analysis of cancer-associated missense variants in the retinoblastoma protein pocket domain

The retinoblastoma tumor suppressor (Rb) is a multifunctional protein that primarily regulates the cell cycle but also has roles in cellular differentiation, DNA damage response, and apoptosis. The loss of Rb is a key event in the development or progression of many cancers. Essential functions of Rb occur through its pocket domain, which is necessary for regulating binding interactions with E2F transcription factors and transcription repressors that bind via an LxCxE motif. The pocket domain is the most highly conserved region of the multidomain protein, as well as the most frequent site of mutations. To understand what effects cancer missense mutations have on Rb's pocket domain, we used fluorescence polarization and differential scanning fluorimetry to quantify changes caused by 75 cancer-associated missense variants to E2F transactivation domain (E2FTD) binding, LxCxE binding, and the thermostability of the pocket domain. We find that 43% of the missense variants tested reduce Rb-E2FTD binding. Many of these variants are not located at the E2FTD-binding site, yet they destabilize the fold of the protein and show temperature-sensitive binding effects. We also find that 21% of tested mutations reduce LxCxE binding, and several mutations selectively disrupt either E2FTD or LxCxE binding. Protein X-ray crystallography of four missense variants reveals how mutations destabilize the protein fold and inhibit E2FTD or LxCxE binding. Taken together, this work provides the first understanding of the multiple ways through which stability, structure, and function of Rb's pocket domain are altered by common missense mutations seen in cancer.

Unleashing the power of peptides in prostate cancer immunotherapy: mechanism, facts and perspectives

Prostate cancer, the second most common cancer in men, often progresses to castration-resistant prostate cancer despite androgen deprivation therapy. Immunotherapy, revolutionary in cancer treatment, has limited efficacy in prostate cancer due to its "cold tumor" nature. Peptides, with unique advantages, offer new hope. This review explores how peptide-based tumor immunotherapy can transform prostate cancer from a "cold" to a "hot" state. It modulates the immunosuppressive tumor microenvironment by regulating non-immune cells (such as cancer-associated fibroblasts, endothelial cells, and adipose stromal cells), repolarizing tumor-associated macrophages, activating NK cells, and tuning cytokines. Additionally, peptides can induce immunogenic cell death (ICD) in prostate cancer cells through ferroptosis, pyroptosis, and autophagy modulation. The review also revisits existing prostate cancer immunotherapies, including immune checkpoint blockade, CAR T cell therapy, and dendritic cell vaccines, highlighting how peptides can enhance their effectiveness and safety. Finally, two peptide-based immunotherapy strategies in the development stage, peptide-integrated Proteolysis-Targeting Chimera therapy and peptide-involved epigenomic therapy, are introduced, showing great potential for future prostate cancer treatment.

Cyclin-Dependent Kinase Inhibition in Prostate Cancer: Past, Present, and Future

BACKGROUND

Despite significant progress, prostate cancer remains a leading cause of death. Cyclin-dependent kinase (CDK) 4/6 inhibitors, which are already approved for the treatment of hormone receptor-positive breast cancer, are undergoing extensive testing as monotherapy and in various combinations as a potentially valuable treatment modality in prostate cancer patients. Thus far, a limited number of these studies have published results, which have been largely disappointing.

AREAS COVERED

In this review, we describe the biologic rationale for the use of CDK4/6 inhibitors in prostate cancer, the existing clinical data describing their use in prostate cancer, and ongoing clinical trials of CDK4/6 inhibitors as monotherapy and in combination for the treatment of prostate cancer. In particular, we focus on possible resistance mechanisms that may be particularly relevant in prostate cancer patients, leading to de novo and acquired resistance, and we highlight novel strategies that can overcome this resistance.

CONCLUSIONS

Current clinical trials are actively working to (1) refine the role of CDK4/6 inhibitors in prostate cancer patients; (2) develop new inhibitors of other cell-cycle targets, such as CDK2 and CDK7; and (3) explore novel combination therapies with inhibitors of other relevant pathways, such as PI3K or MAPK. Further genomic subtyping of advanced prostate cancer will likely shed light on the subsets of patients most likely to benefit from cell-cycle-targeted agents.

DAF-18/PTEN protects LIN-35/Rb from CLP-1/CAPN-mediated cleavage to promote starvation resistance

Starvation resistance is a fundamental trait with profound influence on fitness and disease risk. DAF-18, the C. elegans ortholog of the tumor suppressor PTEN, promotes starvation resistance. PTEN is a dual phosphatase, and DAF-18 promotes starvation resistance as a lipid phosphatase by antagonizing insulin/IGF and PI3K signaling, activating the tumor suppressor DAF-16/FoxO. However, if or how DAF-18/PTEN protein-phosphatase activity promotes starvation resistance is unknown. Using genetic, genomic, bioinformatic, and biochemical approaches, we identified the C. elegans retinoblastoma/RB protein homolog, LIN-35/Rb, as a critical mediator of the effect of DAF-18/PTEN on starvation resistance. We show that DAF-18/PTEN protects LIN-35/Rb from cleavage by the μ-Calpain homolog CLP-1/CAPN, and that LIN-35/Rb together with the repressive DREAM complex promote starvation resistance. We conclude that the tumor suppressors DAF-18/PTEN and LIN-35/Rb function in a linear pathway, with LIN-35/Rb and the rest of the DREAM complex functioning as a transcriptional effector of DAF-18/PTEN protein-phosphatase activity resulting in repression of germline gene expression. This work is significant for revealing a network of tumor suppressors that promote survival during cellular and developmental quiescence.

Aggressive Serous Carcinomas of the Female Reproductive Tract: Cancer-Prone Cell States and Genetic Drivers

In 2025, gynecological cancers are projected to account for approximately 10% of cancer-related deaths in women. High-grade serous ovarian carcinoma (HGSC) and serous endometrial carcinoma (SEC) are the most lethal gynecological cancer subtypes. Both malignancies commonly have TP53 mutations, alterations of the RB1 pathway, and numerous secondary mutations. Both carcinoma types consist of poorly differentiated and highly heterogeneous cell populations at the time of detection. Latent development and rapid progression of HGSC and SEC impede the identification of definitive cells of origin and genetic drivers. Here, we review our current knowledge about cancer-prone cell states and genetic drivers. We also discuss how emerging transcriptomic and genetic tools applied to contemporary model systems may facilitate the identification of novel targets for timely detection and therapeutic intervention.

Targeting CDK4/6 in breast cancer

Dysregulation of the cell cycle machinery, particularly the overactivation of cyclin-dependent kinases 4 and 6 (CDK4/6), is a hallmark of breast cancer pathogenesis. The introduction of CDK4/6 inhibitors has transformed the treatment landscape for hormone receptor-positive breast cancer by effectively targeting abnormal cell cycle progression. However, despite their initial clinical success, drug resistance remains a significant challenge, with no reliable biomarkers available to predict treatment response or guide strategies for managing resistant populations. Consequently, numerous studies have sought to investigate the mechanisms driving resistance to optimize the therapeutic use of CDK4/6 inhibitors and improve patient outcomes. Here we examine the molecular mechanisms regulating the cell cycle, current clinical applications of CDK4/6 inhibitors in breast cancer, and key mechanisms contributing to drug resistance. Furthermore, we discuss emerging predictive biomarkers and highlight potential directions for overcoming resistance and enhancing therapeutic efficacy.

Anti‑proliferative effects of Drynaria fortunei in a model for triple negative breast cancer

Triple negative breast cancer (TNBC) is characterized by the absence of hormones and growth factor receptors. It is typically responsive to anthracycline/taxol-based conventional chemotherapy. However, major therapeutic limitations include systemic toxicity and acquired resistance to chemotherapeutics. To combat this, nutritional herbs from traditional Chinese medicine (TCM) with limited reported toxicity may represent treatment alternatives for TNBC. Such herbs can effectively target multiple signaling pathways in numerous breast cancer models. The efficacy of various nutritional herbs in a cellular model of TNBC is associated with the downregulation of retinoblastoma (RB) signaling through the cyclin D-CDK4/6-RB axis. Therefore, the present study was designed to examine the effects of Drynaria fortunei (DF) in the same cellular model of TNBC to identify potential mechanistic leads for its efficacy. DF is a nutritional herb that represents a common component of herbal formulations used in TCM. The estrogen receptor-negative, progesterone receptor-negative and human epidermal growth factor receptor-2-negative MDA-MB-231 human breast carcinoma-derived cell line was used as the cellular model for TNBC in the present study. Non-fractionated aqueous extract from the bark of DF represented the test agent. Quantitative end-point biomarkers for the efficacy of DF assessed in the present study included cell cycle progression, RB signaling and caspase 3/7 activity. Treatment with DF at cytostatic concentration induced S phase cell cycle arrest and inhibited RB signaling as evidenced by the downregulated expression of cyclin E, CDK2, E2F1 and RB phosphorylation. DF treatment increased pro-apoptotic caspase 3/7 activity which was inhibited by the pan-caspase inhibitor Z-VAD-FMK. DF treatment also exhibited increased expression of cleaved ADP-ribose) polymerase-1. These data identify potential mechanistic leads for anti-proliferative and pro-apoptotic effects of DF in the present TNBC model. The present experiments validated a mechanism-driven experimental approach to identify efficacious nutritional herbs and/or their bioactive constituents as treatment alternatives for TNBC.

RB functions as a key regulator of senescence and tumor suppression

The Retinoblastoma (RB) protein is crucial for regulating gene transcription and chromatin remodeling, impacting cell cycle progression, cellular senescence, and tumorigenesis. Cellular senescence, characterized by irreversible growth arrest and phenotypic alterations, serves as a vital barrier against tumor progression and age-related diseases. RB is crucial in mediating senescence and tumor suppression by modulating the RB-E2F pathway and cross talking with other key senescence effectors such as p53 and p16INK4a. The interplay between RB-mediated cell cycle arrest and cellular senescence offers critical insights into tumorigenesis and potential therapeutic strategies. Leveraging RB-mediated senescence presents promising opportunities for cancer therapy, including novel approaches in tumor immunotherapy designed to enhance treatment efficacy. This review highlights recent advancements in the RB signaling pathway, focusing on its roles in cellular senescence and tumor suppression, and discusses its potential to improve tumor management and clinical outcomes.

Genomic biomarkers of survival in patients with metastatic hormone-sensitive prostate cancer undergoing intensified androgen deprivation therapy

INTRODUCTION

Androgen deprivation therapy intensification (ADTi) with androgen receptor pathway inhibitors (ARPI), docetaxel or both has been shown to improve survival outcomes in patients with metastatic hormone-sensitive prostate cancer (mHSPC). Currently, baseline tumor genomic markers have no role in clinical decision-making in patients with mHSPC.

METHODS

In this IRB-approved retrospective study, patients diagnosed with mHSPC who underwent comprehensive genomic profiling from primary tissue or metastatic sites and treated with ADTi were included. Genomic alterations with an incidence ≥5% were included in the analysis.

RESULTS

A total of 276 patients were eligible and included in the study. In the multivariable analysis, TP53 (HR 1.71, 95% CI 1.17-2.49, p = 0.006), RB1 (HR 2.32, 95% CI 1.28-4.18, p = 0.006), PTEN (HR 1.74, 95% CI 1.12-2.7, p = 0.014), and BRCA2 (HR 2.64, 95% CI 1.42-4.92, p = 0.003) were associated with significantly shorter PFS, while TP53 (HR 1.63, 95% CI 1.00-2.64, p = 0.049), RB1 (HR 4.5, 95% CI 2.32-8.70, p < 0.001), and PTEN (HR 2.4, 95% CI 1.38-4.2, p = 0.003) were associated with significantly worse OS.

CONCLUSIONS

This is one of the largest studies to show the association of baseline tumor genomic markers with survival in patients with mHSPC treated with ADTi. Upon external validation, these results may aid in developing a clinical-genomic risk stratification model, patient counseling, and prognostication.

Clinical implications of DNA ploidy, stroma, and nucleotyping in predicting peritoneal metastasis risk for gastric cancer

BACKGROUND

Gastric cancer peritoneal metastasis lacks effective predictive indices. This article retrospectively explored predictive values of DNA ploidy, stroma, and nucleotyping in gastric cancer peritoneal metastasis.

METHODS

A comprehensive analysis was conducted on specimens obtained from 80 gastric cancer patients who underwent gastric resection at the Department of Gastrointestinal Surgery of Wuhan University Renmin Hospital. Tumor tissues were sectioned and stained. DNA ploidy, stroma, and nucleotyping were quantified using microscopy and digital analysis software. Data analysis was employed by Pearson Chi-square, continuous correction Chi-square, and binary logistic regression.

RESULTS

Using both univariate and multivariate analysis, pathological T stage and nucleotyping exhibited a positive correlation with peritoneal metastasis. DNA ploidy and stroma showed a positive correlation in univariate analysis. Chi-square tests demonstrated a positive correlation of DNA ploidy, stroma, and nucleotyping with peritoneal metastasis. The combined application of these three indicators displayed heightened predictive value for peritoneal metastasis. Non-diploid status, high stroma, and chromosomal heterogeneity emerged as positive factors for peritoneal metastasis in gastric cancer.

CONCLUSIONS

DNA ploidy, stroma, and nucleotyping prove to be predictive factors for peritoneal metastasis, with enhanced predictive efficacy when combined in pairs.

Early Detection of the Pathogenetic Variants of Homologous Recombination Repair Genes in Prostate Cancer: Critical Analysis and Experimental Design

It has been shown that the pathogenic variants (PVs) of the DNA Damage Response (DDR) genes, whether of a germinal or somatic nature, represent a predictive biomarker of high sensitivity to treatment with inhibitors of the enzyme poly-ADP-ribose polymerase (PARP) in patients with hormone-resistant metastatic prostate cancer (HRPCa). Moreover, the detection of PVs of the Homologous Recombination Repair (HRR) genes in PCa patients can help to define the patient's prognosis and the choice of the therapeutic procedure. Among men with metastatic PCa, the frequency of PVs in HRR genes ranges from 11% to 33%, which is a significantly higher rate compared to non-metastatic PCa, where the incidence is between 5% and 10%. Next-Generation Sequencing (NGS) results were more commonly obtained from newly acquired somatic samples compared to archived samples (prostate biopsy or prostatectomy). We developed an experimental multidisciplinary prospective study in patients with a new diagnosis of high-risk PCa at biopsy. The aim was to evaluate the presence of PVs of different HRR genes in patients with the first diagnosis of PCa in relation to a metastatic or non-metastatic stage, tumor aggressiveness, and early risk of progression. Among 43 initial tumor samples from 22 patients, 25 samples from 12 patients were selected for library preparation based on their DNA concentration and quality. After the NGS, 14 different DNA variants were prioritized. Oncogenetic and likely oncogenetic variants were found in the ATM, BRCA1, PTEN, KMT2D, and CDH1 genes. Moreover, variants of uncertain significance were found in ATM, DDR2, FANCA, FOXA1, PLCB4, PTCH1, and RB1.

Tumor-intrinsic regulators of the immune-cold microenvironment of prostate cancer

Prostate cancer (PC) is a notoriously immune-cold tumor in that it often lacks substantial infiltration by antitumor immune cells, and in advanced diseases such as neuroendocrine PC, it could be devoid of immune cells. A majority of PC patients thus have, unfortunately, been unable to benefit from recent advances in immunotherapies. What causes this immunosuppressive microenvironment around PC? In this review, we discuss various genetic and epigenetic regulators intrinsic to prostate tumor cells that could have profound effects on the tumor microenvironment, thus contributing to this immune-cold status. It will be essential to target the cancer cells themselves in order to change the tumor microenvironment to harness existing and developing immunotherapies that had great success in other tumors.

Structure activity relationship for anticancer activities of spirooxindole derivatives: A comprehensive review

Cancer remains one of the leading causes of mortality worldwide, necessitating the continuous search for novel therapeutic agents. Spirooxindole derivatives have recently emerged as a class of compounds with significant potential for cancer treatment owing to their diverse pharmacological activities and unique structural features. The structural diversity of spirooxindole derivatives enables a wide range of modifications, facilitating optimization of their pharmacokinetic and pharmacodynamic properties. Moreover, their ability to interact with multiple molecular targets involved in cancer progression, including kinases, receptors, and enzymes, makes them attractive candidates for multi-targeted therapy. In preclinical studies, numerous spirooxindole derivatives have demonstrated promising antiproliferative activity against various cancer cell lines, including breast, lung, colon, and prostate cancers. Mechanistic investigations have revealed their ability to induce cell cycle arrest and apoptosis and inhibit angiogenesis and metastasis, underscoring their potential as effective anticancer agents. However, challenges such as off-target effects, drug resistance, and limited bioavailability need to be addressed to maximize the therapeutic potential of these compounds. Continued research efforts to elucidate their molecular mechanisms, optimize their pharmacological properties, and conduct rigorous clinical evaluations are warranted to harness their full therapeutic benefits for cancer treatment. This review provides a comprehensive overview of recent advancements in developing spirooxindole derivatives as anticancer agents with structure-activity relationships.

Prognostic Value of Retinoblastoma in Small Intestinal Adenocarcinoma: A Multicenter Retrospective Study

BACKGROUND

The retinoblastoma (RB) protein which is encoded by RB gene selectively provides a cell type-specific function in malignancies. In colorectal carcinoma, RB has been highly expressed and related cyclin/cyclin-dependent kinase 4/6 inhibitors have shown improved therapeutic effects in some patients. However, little is known about RB in small intestinal adenocarcinoma (SIAC).

METHODS

Here, we conducted a multi-institutional study of RB expression in 229 surgically resected SIACs to explore the clinicopathologic and prognostic implications and the relationship with microsatellite instability (MSI) status and KRAS mutations.

RESULTS

High RB expression (RBHigh) was more commonly observed in SIACs (76/229, 33%) than in normal small intestinal mucosa (27/188, 14%; P < 0.001). RBHigh was associated with nodular growth patterns (P = 0.028), the absence of lymphovascular (P = 0.001) and perineural invasion (P = 0.048), and a lower T category (P = 0.042) and indicated better overall survival (P = 0.003). In multivariate analysis, RBHigh (P = 0.049) was an independent prognostic predictor of better prognosis, along with younger patient age (P = 0.049), the absence of retroperitoneal seeding (P = 0.004), lower tumor stage (P < 0.001), and MSI (P = 0.005). The prognostic impact of RB expression was consistently observed regardless of MSI status and specifically persistent in SIACs with lower stages (stages I and II).

CONCLUSION

RBHigh was related to favorable clinicopathologic SIAC characteristics and indicated better patient prognosis. The prognostic predictability of RB was found in SIACs with lower stages, independent of MSI status. RB expression is a reliable and potent prognostic indicator for SIAC and may aid in selecting chemotherapy for patients.

Inhibition of glutaminase elicits senolysis in therapy-induced senescent melanoma cells

The cyclin D1-Cyclin-Dependent Kinases 4 and 6 (CDK4/6) complex is crucial for the development of melanoma. We previously demonstrated that targeting CDK4/6 using small molecule inhibitors (CDK4/6i) suppresses BrafV600E melanoma growth in vitro and in vivo through induction of cellular senescence. However, clinical trials investigating CDK4/6i in melanoma have not yielded successful outcomes, underscoring the necessity to enhance the therapeutic efficacy of CDK4/6i. Accumulated research has shown that while senescence initially suppresses cell proliferation, a prolonged state of senescence eventually leads to tumor relapse by altering the tumor microenvironment, suggesting that removal of those senescent cells (in a process referred to as senolysis) is of clinical necessity to facilitate clinical response. We demonstrate that glutaminase 1 (GLS1) expression is specifically upregulated in CDK4/6i-induced senescent BrafV600E melanoma cells. Upregulated GLS1 expression renders BrafV600E melanoma senescent cells vulnerable to GLS1 inhibitor (GLS1i). Furthermore, we demonstrate that this senolytic approach targeting upregulated GLS1 expression is applicable even though those cells developed resistance to the BrafV600E inhibitor vemurafenib, a frequently encountered substantial clinical challenge to treating patients. Thus, this novel senolytic approach may revolutionize current CDK4/6i mediated melanoma treatment if melanoma cells undergo senescence prior to developing resistance to CDK4/6i. Given that we demonstrate that a low dose of vemurafenib induced senescence, which renders BrafV600E melanoma cells susceptible to GLS1i and recent accumulated research shows many cancer cells undergo senescence in response to chemotherapy, radiation, and immunotherapy, this senolytic therapy approach may prove applicable to a wide range of cancer types once senescence and GLS1 expression are induced.

RRM2 inhibition alters cell cycle through ATM/Rb/E2F1 pathway in atypical teratoid rhabdoid tumor

BACKGROUND

Atypical teratoid rhabdoid tumor (ATRT) is an aggressive brain tumor that mainly affects young children. Our recent study reported a promising therapeutic strategy to trigger DNA damage, impede homologous recombination repair, and induce apoptosis in ATRT cells by targeting ribonucleotide reductase regulatory subunit M2 (RRM2). COH29, an inhibitor of RRM2, effectively reduced tumor growth and prolonged survival in vivo. Herein, we explored the underlying mechanisms controlling these functions to improve the clinical applicability of COH29 in ATRT.

METHODS

Molecular profiling of ATRT patients and COH29-treated cells was analyzed to identify the specific signaling pathways, followed by validation using a knockdown system, flow cytometry, q-PCR, and western blot.

RESULTS

Elevated E2F1 and its signaling pathway were correlated with poor prognosis. RRM2 inhibition induced DNA damage and activated ATM, which reduced Rb phosphorylation to promote Rb-E2F1 interaction and hindered E2F1 functions. E2F1 activity suppression led to decreased E2F1-dependent target expressions, causing cell cycle arrest in the G1 phase, decreased S phase cells, and blocked DNA damage repair.

CONCLUSION

Our study highlights the role of ATM/Rb/E2F1 pathway in controlling cell cycle arrest and apoptosis in response to RRM2 inhibition-induced DNA damage. This provides insight into the therapeutic benefits of COH29 and suggests targeting this pathway as a potential treatment for ATRT.

Cellular senescence and its pathogenic and therapeutic implications in autoimmune hepatitis

INTRODUCTION

Senescent cells are characterized by replicative arrest and phenotypes that produce diverse pro-inflammatory and pro-oxidant mediators. The senescence of diverse hepatic cell types could constitute an unrecognized pathogenic mechanism and prognostic determinant in autoimmune hepatitis. The impact of cellular senescence in autoimmune hepatitis is unknown, and it may suggest adjunctive management strategies.

AREAS COVERED

This review describes the molecular mechanisms of cellular senescence, indicates its diagnostic features, suggests its consequences, presents possible therapeutic interventions, and encourages investigations of its pathogenic role and management in autoimmune hepatitis. Treatment prospects include elimination or reversal of senescent cells, generation of ectopic telomerase, reactivation of dormant telomerase, neutralization of specific pro-inflammatory secretory products, and mitigation of the effects of mitochondrial dysfunction.

EXPERT OPINION

The occurrence, nature, and consequences of cellular senescence in autoimmune hepatitis must be determined. The senescence of diverse hepatic cell types could affect the outcome of autoimmune hepatitis by impairing hepatic regeneration, intensifying liver inflammation, and worsening hepatic fibrosis. Cellular senescence could contribute to suboptimal responses during conventional glucocorticoid-based therapy. Interventions that target specific pro-inflammatory products of the senescent phenotype or selectively promote apoptosis of senescent cells may be preferred adjunctive treatments for autoimmune hepatitis depending on the cancer risk.

Epstein-Barr virus replication within differentiated epithelia requires pRb sequestration of activator E2F transcription factors

Epstein-Barr virus (EBV) co-infections with human papillomavirus (HPV) have been observed in oropharyngeal squamous cell carcinoma. Modeling EBV/HPV co-infection in organotypic epithelial raft cultures revealed that HPV16 E7 inhibited EBV productive replication through the facilitated degradation of the retinoblastoma protein pRb/p105. To further understand how pRb is required for EBV productive replication, we generated CRISPR-Cas9 pRb knockout (KO) normal oral keratinocytes (NOKs) in the context of wild-type and mutant K120E p53. EBV replication was examined in organotypic rafts as a physiological correlate for epithelial differentiation. In pRb KO rafts, EBV DNA copy number was statistically decreased compared to vector controls, regardless of p53 context. Loss of pRb did not affect EBV binding or internalization of calcium-treated NOKs or early infection of rafts. Rather, the block in EBV replication correlated with impaired immediate early gene expression. An EBV infection time course in rafts with mutant p53 demonstrated that pRb-positive basal cells were initially infected with delayed replication occurring in differentiated layers. Loss of pRb showed increased S-phase progression makers and elevated activator E2F activity in raft tissues. Complementation with a panel of pRb/E2F binding mutants showed that wild type or pRb∆685 mutant capable of E2F binding reduced S-phase marker gene expression, rescued EBV DNA replication, and restored BZLF1 expression in pRb KO rafts. However, pRb KO complemented with pRb661W mutant, unable to bind E2Fs, failed to rescue EBV replication in raft culture. These findings suggest that EBV productive replication in differentiated epithelium requires pRb inhibition of activator E2Fs to restrict S-phase progression.IMPORTANCEA subset of human papillomavirus (HPV)-positive oropharyngeal squamous cell carcinoma is co-positive for Epstein-Barr virus (EBV). Potential oncogenic viral interactions revealed that HPV16 E7 inhibited productive EBV replication within the differentiated epithelium. As E7 mediates the degradation of pRb, we aimed to establish how pRb is involved in EBV replication. In the context of differentiated epithelium using organotypic raft culture, we evaluated how the loss of pRb affects EBV lytic replication to better comprehend EBV contributions to carcinogenesis. In this study, ablation of pRb interfered with EBV replication at the level of immediate early gene expression. Loss of pRb increased activator E2Fs and associated S-phase gene expression throughout the differentiated epithelium. Complementation studies showed that wild type and pRb mutant capable of binding to E2F rescued EBV replication, while pRb mutant lacking E2F binding did not. Altogether, these studies support that in differentiated tissues, HPV16 E7-mediated degradation of pRb inhibits EBV replication through unregulated E2F activity.

A role for Retinoblastoma 1 in hindbrain morphogenesis by regulating GBX family

The hindbrain, which develops from the anterior end of the neural tube expansion, can differentiate into the metencephalon and myelencephalon, with varying sizes and functions. The midbrain-hindbrain boundary (MHB) and hindbrain myelencephalon/ventral midline (HMVM) are known to be the source of the progenitors for the anterior hindbrain and myelencephalon, respectively. However, the molecular networks regulating hindbrain morphogenesis in these structures remain unclear. In this study, we show that retinoblastoma 1 (rb1) is highly expressed at the MHB and HMVM in zebrafish. Knocking out rb1 in mice and zebrafish results in an enlarged hindbrain due to hindbrain neuronal hyperproliferation. Further study reveals that Rb1 controls the hindbrain morphogenesis by suppressing the expression of Gbx1/Gbx2, essential transcription factors for hindbrain development, through its binding to E2f3/Hdac1, respectively. Interestingly, we find that Gbx1 and Gbx2 are expressed in different types of hindbrain neurons, suggesting distinct roles in hindbrain morphogenesis. In summary, our study clarifies the specific role of RB1 in hindbrain neural cell proliferation and morphogenesis by regulating the E2f3-Gbx1 axis and the Hdac1-Gbx2 axis. These findings provide a research paradigm for exploring the differential proliferation of neurons in various brain regions.

Concurrent RB1 Loss and BRCA Deficiency Predicts Enhanced Immunologic Response and Long-term Survival in Tubo-ovarian High-grade Serous Carcinoma

PURPOSE

The purpose of this study was to evaluate RB1 expression and survival across ovarian carcinoma histotypes and how co-occurrence of BRCA1 or BRCA2 (BRCA) alterations and RB1 loss influences survival in tubo-ovarian high-grade serous carcinoma (HGSC).

EXPERIMENTAL DESIGN

RB1 protein expression was classified by immunohistochemistry in ovarian carcinomas of 7,436 patients from the Ovarian Tumor Tissue Analysis consortium. We examined RB1 expression and germline BRCA status in a subset of 1,134 HGSC, and related genotype to overall survival (OS), tumor-infiltrating CD8+ lymphocytes, and transcriptomic subtypes. Using CRISPR-Cas9, we deleted RB1 in HGSC cells with and without BRCA1 alterations to model co-loss with treatment response. We performed whole-genome and transcriptome data analyses on 126 patients with primary HGSC to characterize tumors with concurrent BRCA deficiency and RB1 loss.

RESULTS

RB1 loss was associated with longer OS in HGSC but with poorer prognosis in endometrioid ovarian carcinoma. Patients with HGSC harboring both RB1 loss and pathogenic germline BRCA variants had superior OS compared with patients with either alteration alone, and their median OS was three times longer than those without pathogenic BRCA variants and retained RB1 expression (9.3 vs. 3.1 years). Enhanced sensitivity to cisplatin and paclitaxel was seen in BRCA1-altered cells with RB1 knockout. Combined RB1 loss and BRCA deficiency correlated with transcriptional markers of enhanced IFN response, cell-cycle deregulation, and reduced epithelial-mesenchymal transition. CD8+ lymphocytes were most prevalent in BRCA-deficient HGSC with co-loss of RB1.

CONCLUSIONS

Co-occurrence of RB1 loss and BRCA deficiency was associated with exceptionally long survival in patients with HGSC, potentially due to better treatment response and immune stimulation.

Cyclin A/B RxL Macrocyclic Inhibitors to Treat Cancers with High E2F Activity

Cancer cell proliferation requires precise control of E2F1 activity; excess activity promotes apoptosis. Here, we developed cell-permeable and bioavailable macrocycles that selectively kill small cell lung cancer (SCLC) cells with inherent high E2F1 activity by blocking RxL-mediated interactions of cyclin A and cyclin B with select substrates. Genome-wide CRISPR/Cas9 knockout and random mutagenesis screens found that cyclin A/B RxL macrocyclic inhibitors (cyclin A/Bi) induced apoptosis paradoxically by cyclin B- and Cdk2-dependent spindle assembly checkpoint activation (SAC). Mechanistically, cyclin A/Bi hyperactivate E2F1 and cyclin B by blocking their RxL-interactions with cyclin A and Myt1, respectively, ultimately leading to SAC activation and mitotic cell death. Base editor screens identified cyclin B variants that confer cyclin A/Bi resistance including several variants that disrupted cyclin B:Cdk interactions. Unexpectedly but consistent with our base editor and knockout screens, cyclin A/Bi induced the formation of neo-morphic Cdk2-cyclin B complexes that promote SAC activation and apoptosis. Finally, orally-bioavailable cyclin A/Bi robustly inhibited tumor growth in chemotherapy-resistant patient-derived xenograft models of SCLC. This work uncovers gain-of-function mechanisms by which cyclin A/Bi induce apoptosis in cancers with high E2F activity, and suggests cyclin A/Bi as a therapeutic strategy for SCLC and other cancers driven by high E2F activity.

APC/C prevents a noncanonical order of cyclin/CDK activity to maintain CDK4/6 inhibitor-induced arrest

Regulated cell cycle progression ensures homeostasis and prevents cancer. In proliferating cells, premature S phase entry is avoided by the E3 ubiquitin ligase anaphasepromoting complex/cyclosome (APC/C), although the APC/C substrates whose degradation restrains G1-S progression are not fully known. The APC/C is also active in arrested cells that exited the cell cycle, but it is not clear whether APC/C maintains all types of arrest. Here, by expressing the APC/C inhibitor, EMI1, we show that APC/C activity is essential to prevent S phase entry in cells arrested by pharmacological cyclin-dependent kinases 4 and 6 (CDK4/6) inhibition (Palbociclib). Thus, active protein degradation is required for arrest alongside repressed cell cycle gene expression. The mechanism of rapid and robust arrest bypass from inhibiting APC/C involves CDKs acting in an atypical order to inactivate retinoblastoma-mediated E2F repression. Inactivating APC/C first causes mitotic cyclin B accumulation which then promotes cyclin A expression. We propose that cyclin A is the key substrate for maintaining arrest because APC/C-resistant cyclin A, but not cyclin B, is sufficient to induce S phase entry. Cells bypassing arrest from CDK4/6 inhibition initiate DNA replication with severely reduced origin licensing. The simultaneous accumulation of S phase licensing inhibitors, such as cyclin A and geminin, with G1 licensing activators disrupts the normal order of G1-S progression. As a result, DNA synthesis and cell proliferation are profoundly impaired. Our findings predict that cancers with elevated EMI1 expression will tend to escape CDK4/6 inhibition into a premature, underlicensed S phase and suffer enhanced genome instability.

In-depth analysis of the interplay between oncogenic mutations and NK cell-mediated cancer surveillance in solid tumors

Natural killer (NK) cells play a crucial role in antitumoral and antiviral responses. Yet, cancer cells can alter themselves or the microenvironment through the secretion of cytokines or other factors, hindering NK cell activation and promoting a less cytotoxic phenotype. These resistance mechanisms, often referred to as the "hallmarks of cancer" are significantly influenced by the activation of oncogenes, impacting most, if not all, of the described hallmarks. Along with oncogenes, other types of genes, the tumor suppressor genes are frequently mutated or modified during cancer. Traditionally, these genes have been associated with uncontrollable tumor growth and apoptosis resistance. Recent evidence suggests oncogenic mutations extend beyond modulating cell death/proliferation programs, influencing cancer immunosurveillance. While T cells have been more studied, the results obtained highlight NK cells as emerging key protagonists for enhancing tumor cell elimination by modulating oncogenic activity. A few recent studies highlight the crucial role of oncogenic mutations in NK cell-mediated cancer recognition, impacting angiogenesis, stress ligands, and signaling balance within the tumor microenvironment. This review will critically examine recent discoveries correlating oncogenic mutations to NK cell-mediated cancer immunosurveillance, a relatively underexplored area, particularly in the era dominated by immune checkpoint inhibitors and CAR-T cells. Building on these insights, we will explore opportunities to improve NK cell-based immunotherapies, which are increasingly recognized as promising alternatives for treating low-antigenic tumors, offering significant advantages in terms of safety and manufacturing suitability.

Senescence and senolysis in cancer: The latest findings

Aging is a life phenomenon that occurs in most living organisms and is a major risk factor for many diseases, including cancer. Cellular senescence is a cellular trait induced by various genomic and epigenetic stresses. Senescent cells are characterized by irreversible cell growth arrest and excessive secretion of inflammatory cytokines (senescence-associated secretory phenotypes, SASP). Chronic tissue microinflammation induced by SASP contributes to the pathogenesis of a variety of age-related diseases, including cancer. Senolysis is a promising new strategy to selectively eliminate senescent cells in order to suppress chronic inflammation, suggesting its potential use as an anticancer therapy. This review summarizes recent findings on the molecular basis of senescence in cancer cells and senolysis.

p53 Genetics and Biology in Lung Carcinomas: Insights, Implications and Clinical Applications

The TP53 gene is renowned as a tumor suppressor, playing a pivotal role in overseeing the cell cycle, apoptosis, and maintaining genomic stability. Dysregulation of p53 often contributes to the initiation and progression of various cancers, including lung cancer (LC) subtypes. The review explores the intricate relationship between p53 and its role in the development and progression of LC. p53, a crucial tumor suppressor protein, exists in various isoforms, and understanding their distinct functions in LC is essential for advancing our knowledge of this deadly disease. This review aims to provide a comprehensive literature overview of p53, its relevance to LC, and potential clinical applications.

Landscape of driver mutations and their clinical effects on Down syndrome-related myeloid neoplasms

ABSTRACT

Transient abnormal myelopoiesis (TAM) is a common complication in newborns with Down syndrome (DS). It commonly progresses to myeloid leukemia (ML-DS) after spontaneous regression. In contrast to the favorable prognosis of primary ML-DS, patients with refractory/relapsed ML-DS have poor outcomes. However, the molecular basis for refractoriness and relapse and the full spectrum of driver mutations in ML-DS remain largely unknown. We conducted a genomic profiling study of 143 TAM, 204 ML-DS, and 34 non-DS acute megakaryoblastic leukemia cases, including 39 ML-DS cases analyzed by exome sequencing. Sixteen novel mutational targets were identified in ML-DS samples. Of these, inactivations of IRX1 (16.2%) and ZBTB7A (13.2%) were commonly implicated in the upregulation of the MYC pathway and were potential targets for ML-DS treatment with bromodomain-containing protein 4 inhibitors. Partial tandem duplications of RUNX1 on chromosome 21 were also found, specifically in ML-DS samples (13.7%), presenting its essential role in DS leukemia progression. Finally, in 177 patients with ML-DS treated following the same ML-DS protocol (the Japanese Pediatric Leukemia and Lymphoma Study Group acute myeloid leukemia -D05/D11), CDKN2A, TP53, ZBTB7A, and JAK2 alterations were associated with a poor prognosis. Patients with CDKN2A deletions (n = 7) or TP53 mutations (n = 4) had substantially lower 3-year event-free survival (28.6% vs 90.5%; P < .001; 25.0% vs 89.5%; P < .001) than those without these mutations. These findings considerably change the mutational landscape of ML-DS, provide new insights into the mechanisms of progression from TAM to ML-DS, and help identify new therapeutic targets and strategies for ML-DS.

The Traces of Dysregulated lncRNAs-Associated ceRNA Axes in Retinoblastoma: A Systematic Scope Review

PURPOSE

Long non-coding RNAs are an essential component of competing endogenous RNA regulatory axes and play their role by sponging microRNAs and interfering with the regulation of gene expression. Because of the broadness of competing endogenous RNA interaction networks, they may help investigate treatment targets in complicated disorders.

METHODS

This study performed a systematic scoping review to assess verified loops of competing endogenous RNAs in retinoblastoma, emphasizing the competing endogenous RNAs axis related to long non-coding RNAs. We used a six-stage approach framework and the PRISMA guidelines. A systematic search of seven databases was done to locate suitable papers published before February 2022. Two reviewers worked independently to screen articles and collect data.

RESULTS

Out of 363 records, fifty-one articles met the inclusion criteria, and sixty-three axes were identified in desired articles. The majority of the research reported several long non-coding RNAs that were experimentally verified to act as competing endogenous RNAs in retinoblastoma: XIST/NEAT1/MALAT1/SNHG16/KCNQ1OT1, respectively. At the same time, around half of the studies investigated unique long non-coding RNAs.

CONCLUSIONS

Understanding the many features of this regulatory system may aid in elucidating the unknown etiology of Retinoblastoma and providing novel molecular targets for therapeutic and clinical applications.

A synthetic lethal dependency on casein kinase 2 in response to replication-perturbing therapeutics in RB1-deficient cancer cells

Resistance to therapy commonly develops in patients with high-grade serous ovarian carcinoma (HGSC) and triple-negative breast cancer (TNBC), urging the search for improved therapeutic combinations and their predictive biomarkers. Starting from a CRISPR knockout screen, we identified that loss of RB1 in TNBC or HGSC cells generates a synthetic lethal dependency on casein kinase 2 (CK2) for surviving the treatment with replication-perturbing therapeutics such as carboplatin, gemcitabine, or PARP inhibitors. CK2 inhibition in RB1-deficient cells resulted in the degradation of another RB family cell cycle regulator, p130, which led to S phase accumulation, micronuclei formation, and accelerated PARP inhibition-induced aneuploidy and mitotic cell death. CK2 inhibition was also effective in primary patient-derived cells. It selectively prevented the regrowth of RB1-deficient patient HGSC organoids after treatment with carboplatin or niraparib. As about 25% of HGSCs and 40% of TNBCs have lost RB1 expression, CK2 inhibition is a promising approach to overcome resistance to standard therapeutics in large strata of patients.

Tumor biomarkers for diagnosis, prognosis and targeted therapy

Tumor biomarkers, the substances which are produced by tumors or the body's responses to tumors during tumorigenesis and progression, have been demonstrated to possess critical and encouraging value in screening and early diagnosis, prognosis prediction, recurrence detection, and therapeutic efficacy monitoring of cancers. Over the past decades, continuous progress has been made in exploring and discovering novel, sensitive, specific, and accurate tumor biomarkers, which has significantly promoted personalized medicine and improved the outcomes of cancer patients, especially advances in molecular biology technologies developed for the detection of tumor biomarkers. Herein, we summarize the discovery and development of tumor biomarkers, including the history of tumor biomarkers, the conventional and innovative technologies used for biomarker discovery and detection, the classification of tumor biomarkers based on tissue origins, and the application of tumor biomarkers in clinical cancer management. In particular, we highlight the recent advancements in biomarker-based anticancer-targeted therapies which are emerging as breakthroughs and promising cancer therapeutic strategies. We also discuss limitations and challenges that need to be addressed and provide insights and perspectives to turn challenges into opportunities in this field. Collectively, the discovery and application of multiple tumor biomarkers emphasized in this review may provide guidance on improved precision medicine, broaden horizons in future research directions, and expedite the clinical classification of cancer patients according to their molecular biomarkers rather than organs of origin.

Dual-Capped Helical Interface Mimics

Disruption of protein-protein interactions is medicinally important. Interface helices may be mimicked in helical probes featuring enhanced rigidities, binding to protein targets, stabilities in serum, and cell uptake. This form of mimicry is dominated by stapling between side chains of helical residues: there has been less progress on helical N-caps, and there were no generalizable C-caps. Conversely, in natural proteins, helicities are stabilized and terminated by C- and N-caps but not staples. Bicyclic caps previously introduced by us enable interface helical mimicry featuring rigid synthetic caps at both termini in this work. An unambiguously helical dual-capped system proved to be conformationally stable, binding cyclins A and E, and showed impressive cellular uptake. In addition, the dual-capped mimic was completely resistant to proteolysis in serum over an extended period when compared with "gold standard" hydrocarbon-stapled controls. Dual-capped peptidomimetics are a new, generalizable paradigm for helical interface probe design.

Patterns in the tapestry of chromatin-bound RB

The retinoblastoma protein (RB)-mediated regulation of E2F is a component of a highly conserved cell cycle machine. However, RB's tumor suppressor activity, like RB's requirement in animal development, is tissue-specific, context-specific, and sometimes appears uncoupled from cell proliferation. Detailed new information about RB's genomic distribution provides a new perspective on the complexity of RB function, suggesting that some of its functional specificity results from context-specific RB association with chromatin. Here we summarize recent evidence showing that RB targets different types of chromatin regulatory elements at different cell cycle stages. RB controls traditional RB/E2F targets prior to S-phase, but, when cells proliferate, RB redistributes to cell type-specific chromatin loci. We discuss the broad implications of the new data for RB research.

Canalizing cell fate by transcriptional repression

Precision in the establishment and maintenance of cellular identities is crucial for the development of multicellular organisms and requires tight regulation of gene expression. While extensive research has focused on understanding cell type-specific gene activation, the complex mechanisms underlying the transcriptional repression of alternative fates are not fully understood. Here, we provide an overview of the repressive mechanisms involved in cell fate regulation. We discuss the molecular machinery responsible for suppressing alternative fates and highlight the crucial role of sequence-specific transcription factors (TFs) in this process. Depletion of these TFs can result in unwanted gene expression and increased cellular plasticity. We suggest that these TFs recruit cell type-specific repressive complexes to their cis-regulatory elements, enabling them to modulate chromatin accessibility in a context-dependent manner. This modulation effectively suppresses master regulators of alternative fate programs and their downstream targets. The modularity and dynamic behavior of these repressive complexes enables a limited number of repressors to canalize and maintain major and minor cell fate decisions at different stages of development.

Analysis of E2F1 single-nucleotide polymorphisms reveals deleterious non-synonymous substitutions that disrupt E2F1-RB protein interaction in cancer

Cancer is a medical condition that is caused by the abnormal growth and division of cells, leading to the formation of tumors. The E2F1 and RB pathways are critical in regulating cell cycle, and their dysregulation can contribute to the development of cancer. In this study, we analyzed experimentally reported SNPs in E2F1 and assessed their effects on the binding affinity with RB. Out of 46, nine mutations were predicted as deleterious, and further analysis revealed four highly destabilizing mutations (L206W, R232C, I254T, A267T) that significantly altered the protein structure. Molecular docking of wild-type and mutant E2F1 with RB revealed a docking score of -242 kcal/mol for wild-type, while the mutant complexes had scores ranging from -217 to -220 kcal/mol. Molecular simulation analysis revealed variations in the dynamics features of both mutant and wild-type complexes due to the acquired mutations. Furthermore, the total binding free energy for the wild-type E2F1-RB complex was -64.89 kcal/mol, while those of the L206W, R232C, I254T, and A267T E2F1-RB mutants were -45.90 kcal/mol, -53.52 kcal/mol, -55.67 kcal/mol, and -61.22 kcal/mol, respectively. Our study is the first to extensively analyze E2F1 gene mutations and identifies candidate mutations for further validation and potential targeting for cancer therapeutics.

MYC induces CDK4/6 inhibitors resistance by promoting pRB1 degradation

CDK4/6 inhibitors (CDK4/6i) show anticancer activity in certain human malignancies, such as breast cancer. However, their application to other tumor types and intrinsic resistance mechanisms are still unclear. Here, we demonstrate that MYC amplification confers resistance to CDK4/6i in bladder, prostate and breast cancer cells. Mechanistically, MYC binds to the promoter of the E3 ubiquitin ligase KLHL42 and enhances its transcription, leading to RB1 deficiency by inducing both phosphorylated and total pRB1 ubiquitination and degradation. We identify a compound that degrades MYC, A80.2HCl, which induces MYC degradation at nanomolar concentrations, restores pRB1 protein levels and re-establish sensitivity of MYC high-expressing cancer cells to CDK4/6i. The combination of CDK4/6i and A80.2HCl result in marked regression in tumor growth in vivo. Altogether, these results reveal the molecular mechanisms underlying MYC-induced resistance to CDK4/6i and suggest the utilization of the MYC degrading molecule A80.2HCl to potentiate the therapeutic efficacy of CDK4/6i.

Selective Occupation by E2F and RB of Loci Expressed by RNA Polymerase III

In all cases tested, TFIIIB is responsible for recruiting pol III to its genetic templates. In mammalian cells, RB binds TFIIIB and prevents its interactions with both promoter DNA and pol III, thereby suppressing transcription. As TFIIIB is not recruited to its target genes when bound by RB, the mechanism predicts that pol III-dependent templates will not be occupied by RB; this contrasts with the situation at most genes controlled by RB, where it can be tethered by promoter-bound sequence-specific DNA-binding factors such as E2F. Contrary to this prediction, however, ChIP-seq data reveal the presence of RB in multiple cell types and the related protein p130 at many loci that rely on pol III for their expression, including RMRP, RN7SL, and a variety of tRNA genes. The sets of genes targeted varies according to cell type and growth state. In such cases, recruitment of RB and p130 can be explained by binding of E2F1, E2F4 and/or E2F5. Genes transcribed by pol III had not previously been identified as common targets of E2F family members. The data provide evidence that E2F may allow for the selective regulation of specific non-coding RNAs by RB, in addition to its influence on overall pol III output through its interaction with TFIIIB.

Exploring the Potential Role of Phytopharmaceuticals in Alleviating Toxicities of Chemotherapeutic Agents

BACKGROUND

Chemotherapy is the mainstay of cancer treatment, bringing patients optimism about recurrence and survival. However, the clinical effectiveness of chemotherapeutic drugs is frequently jeopardized by their intrinsic toxicity, resulting in side effects affecting the quality of life of cancer patients. This analysis explores the ethnopharmacological impact of phytopharmaceuticals, highlighting their traditional use in many cultures. The present study, which takes its cues from indigenous knowledge, aims to close the knowledge gap between traditional medicine and modern medicine in reducing the toxicities of chemotherapy treatments.

AIM

The present in-depth study aims to highlight the current research and upcoming developments in phytopharmaceuticals for reducing the toxicity of chemotherapeutic drugs. Further, we address the mechanisms through which phytopharmaceuticals may reduce chemotherapy-induced side effects that include nausea, vomiting, myelosuppression, nephropathy, neuropathy, and cardiotoxicity using data from a variety of preclinical and clinical investigations.

MATERIALS AND METHODS

The literature search was carried out by employing search engines such as PubMed and Google Scholar with keywords such as cancer, chemotherapy, CNS toxicity, hematopoietic toxicity, renal toxicity, GI toxicity, CNS toxicity, and phytopharmaceuticals.

RESULTS

Bioactive chemicals found in plants, such as fruits, vegetables, herbs, and spices, are being studied for their capacity to improve the safety and acceptability of chemotherapy regimens. The current review also dives into the investigation of phytopharmaceuticals as adjuvant medicines in cancer treatment, which is a viable path for addressing the pressing need to lessen chemotherapy-induced toxicities.

CONCLUSION

The present review revealed that the potential of phytopharmaceuticals in alleviating chemotherapeutic drug toxicities would pave the way for better cancer treatment and patient outcomes, harmonizing with the larger trend towards personalized and holistic approaches to chemotherapy.

JHD205, A Novel Abemaciclib Derivative, Exerts Antitumor Effects on Breast Cancer by CDK4/6

BACKGROUND

Efficient targeted molecular therapeutics are needed for the treatment of triple-negative breast cancer (TNBC), a highly invasive and difficult-to-treat form of breast cancer associated with a poor prognosis.

OBJECTIVES

This study aims to evaluate the potential of selective CDK4/6 inhibitors as a therapeutic option for TNBC by impairing the cell cycle G1 phase through the inhibition of retinoblastoma protein (Rb) phosphorylation.

METHODS

In this study, we synthesized a compound called JHD205, derived from the chemical structure of Abemaciclib, and examined its inhibitory effects on the malignant characteristics of TNBC cells.

RESULTS

Our results demonstrated that JHD205 exhibited superior tumor growth inhibition compared to Abemaciclib in breast cancer xenograft chicken embryo models. Western blot analysis revealed that JHD205 could dosedependently degrade CDK4 and CDK6 while also causing abnormal changes in other proteins associated with CDK4/6, such as p-Rb, Rb, and E2F1. Moreover, JHD205 induced apoptosis and DNA damage and inhibited DNA repair by upregulating Caspase3 and p-H2AX protein levels.

CONCLUSION

Collectively, our findings suggest that JHD205 holds promise as a potential treatment for breast carcinoma.

Serum Metabolomics of Retinoblastoma: Assessing the Differential Serum Metabolic Signatures of Unilateral and Bilateral Patients

Retinoblastoma (Rb) is the most common pediatric eye cancer. To identify the biomarkers for early diagnosis and monitoring the progression of Rb in patients, mapping of the alterations in their metabolic profiles is essential. The present study aims at exploring the metabolic disparity in serum from Rb patients and controls using NMR-based metabolomics. A total of 72 metabolites, including carbohydrates, amino acids, and organic acids, were quantified in serum samples from 24 Rb patients and 26 controls. Distinct clusters of Rb patients and controls were obtained using the partial least-squares discriminant analysis (PLS-DA) model. Further, univariate and multivariate analyses of unilateral and bilateral Rb patients with respect to their age-matched controls depicted their distinct metabolic fingerprints. Metabolites including 2-phosphoglycerate, 4-aminobutyrate, proline, O-phosphocholine, O-phosphoethanolamine, and Sn-glycero-3-phosphocholine (Sn-GPC) showed significant perturbation in both unilateral and bilateral Rb patients. However, metabolic differences among the bilateral Rb cases were more pronounced than those in unilateral Rb cases with respect to controls. In addition to major discriminatory metabolites for Rb, unilateral and bilateral Rb cases showed specific metabolic changes, which might be the result of their differential genetic/somatic mutational backgrounds. This further suggests that the aberrant metabolic perturbation in bilateral patients signifies the severity of the disease in Rb patients. The present study demonstrated that identified serum metabolites have potential to serve as a noninvasive method for detection of Rb, discriminate bilateral from unilateral Rb patients, and aid in better understanding of the RB tumor biology.

RB1 5́UTR contains an IRES related to cell cycle control and cancer progression

Retinoblastoma gene1 (RB1) is the first tumor suppressor gene that stands as the guardian of the gate of the G1 period and plays a central role in proliferation and differentiation. However, no reports focused on the possible internal ribosome entry site (IRES) function of the RB1 gene flanking sequence. In this study, we constructed a bicistronic reporter with the RB1 5'untranslated region (5́UTR) inserted between two reporter coding regions. We found RB1 5'UTR harbors an IRES and has higher activity in cancer cell lines than normal cells. Besides, RB1 IRES acquired the highest activity in the G0/G1 phase of the cell cycle, and the RB1 5'UTR mutation collected from retinoblastoma decreased IRES activity compared with RB1 5'UTR wild-type. These data indicated that RB1 IRES is a mechanism of stress regulation and is related to cell cycle control and cancer progression.

RB loss sensitizes cells to replication-associated DNA damage after PARP inhibition by trapping

The retinoblastoma tumor suppressor protein (RB) interacts physically and functionally with a number of epigenetic modifying enzymes to control transcriptional regulation, respond to replication stress, promote DNA damage response and repair, and regulate genome stability. To better understand how disruption of RB function impacts epigenetic regulation of genome stability and determine whether such changes represent exploitable weaknesses of RB-deficient cancer cells, we performed an imaging-based screen to identify epigenetic inhibitors that promote DNA damage and compromise the viability of RB-deficient cells. We found that loss of RB alone leads to high levels of replication-dependent poly-ADP ribosylation (PARylation) and that preventing PARylation by trapping PARP enzymes on chromatin enables RB-deficient cells to progress to mitosis with unresolved replication stress. These defects contribute to high levels of DNA damage and compromised cell viability. We demonstrate this sensitivity is conserved across a panel of drugs that target both PARP1 and PARP2 and can be suppressed by reexpression of the RB protein. Together, these data indicate that drugs that target PARP1 and PARP2 may be clinically relevant for RB-deficient cancers.

Concurrent RB1 loss and BRCA-deficiency predicts enhanced immunological response and long-term survival in tubo-ovarian high-grade serous carcinoma

Background

Somatic loss of the tumour suppressor RB1 is a common event in tubo-ovarian high-grade serous carcinoma (HGSC), which frequently co-occurs with alterations in homologous recombination DNA repair genes including BRCA1 and BRCA2 (BRCA). We examined whether tumour expression of RB1 was associated with survival across ovarian cancer histotypes (HGSC, endometrioid (ENOC), clear cell (CCOC), mucinous (MOC), low-grade serous carcinoma (LGSC)), and how co-occurrence of germline BRCA pathogenic variants and RB1 loss influences long-term survival in a large series of HGSC.

Patients and methods

RB1 protein expression patterns were classified by immunohistochemistry in epithelial ovarian carcinomas of 7436 patients from 20 studies participating in the Ovarian Tumor Tissue Analysis consortium and assessed for associations with overall survival (OS), accounting for patient age at diagnosis and FIGO stage. We examined RB1 expression and germline BRCA status in a subset of 1134 HGSC, and related genotype to survival, tumour infiltrating CD8+ lymphocyte counts and transcriptomic subtypes. Using CRISPR-Cas9, we deleted RB1 in HGSC cell lines with and without BRCA1 mutations to model co-loss with treatment response. We also performed genomic analyses on 126 primary HGSC to explore the molecular characteristics of concurrent homologous recombination deficiency and RB1 loss.

Results

RB1 protein loss was most frequent in HGSC (16.4%) and was highly correlated with RB1 mRNA expression. RB1 loss was associated with longer OS in HGSC (hazard ratio [HR] 0.74, 95% confidence interval [CI] 0.66-0.83, P = 6.8 ×10-7), but with poorer prognosis in ENOC (HR 2.17, 95% CI 1.17-4.03, P = 0.0140). Germline BRCA mutations and RB1 loss co-occurred in HGSC (P < 0.0001). Patients with both RB1 loss and germline BRCA mutations had a superior OS (HR 0.38, 95% CI 0.25-0.58, P = 5.2 ×10-6) compared to patients with either alteration alone, and their median OS was three times longer than non-carriers whose tumours retained RB1 expression (9.3 years vs. 3.1 years). Enhanced sensitivity to cisplatin (P < 0.01) and paclitaxel (P < 0.05) was seen in BRCA1 mutated cell lines with RB1 knockout. Among 126 patients with whole-genome and transcriptome sequence data, combined RB1 loss and genomic evidence of homologous recombination deficiency was correlated with transcriptional markers of enhanced interferon response, cell cycle deregulation, and reduced epithelial-mesenchymal transition in primary HGSC. CD8+ lymphocytes were most prevalent in BRCA-deficient HGSC with co-loss of RB1.

Conclusions

Co-occurrence of RB1 loss and BRCA mutation was associated with exceptionally long survival in patients with HGSC, potentially due to better treatment response and immune stimulation.

APC/C prevents non-canonical order of cyclin/CDK activity to maintain CDK4/6 inhibitor-induced arrest

Regulated cell cycle progression ensures homeostasis and prevents cancer. In proliferating cells, premature S phase entry is avoided by the E3 ubiquitin ligase APC/C (anaphase promoting complex/cyclosome), although the APC/C substrates whose degradation restrains G1-S progression are not fully known. The APC/C is also active in arrested cells that exited the cell cycle, but it is not clear if APC/C maintains all types of arrest. Here by expressing the APC/C inhibitor, EMI1, we show that APC/C activity is essential to prevent S phase entry in cells arrested by pharmacological CDK4/6 inhibition (Palbociclib). Thus, active protein degradation is required for arrest alongside repressed cell cycle gene expression. The mechanism of rapid and robust arrest bypass from inhibiting APC/C involves cyclin-dependent kinases acting in an atypical order to inactivate RB-mediated E2F repression. Inactivating APC/C first causes mitotic cyclin B accumulation which then promotes cyclin A expression. We propose that cyclin A is the key substrate for maintaining arrest because APC/C-resistant cyclin A, but not cyclin B, is sufficient to induce S phase entry. Cells bypassing arrest from CDK4/6 inhibition initiate DNA replication with severely reduced origin licensing. The simultaneous accumulation of S phase licensing inhibitors, such as cyclin A and geminin, with G1 licensing activators disrupts the normal order of G1-S progression. As a result, DNA synthesis and cell proliferation are profoundly impaired. Our findings predict that cancers with elevated EMI1 expression will tend to escape CDK4/6 inhibition into a premature, underlicensed S phase and suffer enhanced genome instability.