Results suggest that MDM2 3’UTR elongation may trigger a non-canonical regulatory mechanism that bypasses the traditional MDM2-p53 interaction, and suggests that APA-mediated gene modulation can induce unforeseen compensatory survival pathways in cancer cells, necessitating further investigation into the broader functional landscape of elongated 3'UTRs.
Abstract
This study proposes a novel therapeutic strategy to suppress cancer growth by modulating the MDM2-p53 axis via Alternative Polyadenylation (APA). MDM2 normally promotes tumorigenesis by ubiquitinating and degrading the tumor suppressor p53. In cancer cells, preferential use of proximal polyadenylation signals (PAS) results in shortened 3’UTRs, allowing oncogenic transcripts like MDM2 to evade nuclear sequestration mediated by Inverted Alu (IRAlu) double-stranded RNA structures. We hypothesized that forcing distal PAS usage would elongate the MDM2 mRNA, promoting its nuclear retention and reducing protein translation, thereby restoring p53 activity. Using CRISPR-Cas9, we targeted and deleted the most frequent proximal PAS in the MDM2 3’UTR of A549 cells. Successful genome editing was confirmed via PCR. As expected, Western blot analysis showed a significant reduction in MDM2 expression in PAS-edited cells. However, experimental outcomes contradicted our initial hypothesis: edited cells exhibited higher viability under doxorubicin treatment compared to wild-type cells. Furthermore, despite decreased MDM2 levels, a concurrent reduction in phosphorylated p53 (p-p53) was observed. These unexpected results suggest that MDM2 3’UTR elongation may trigger a non-canonical regulatory mechanism that bypasses the traditional MDM2-p53 interaction. This study highlights the complexity of post-transcriptional regulation and suggests that APA-mediated gene modulation can induce unforeseen compensatory survival pathways in cancer cells, necessitating further investigation into the broader functional landscape of elongated 3’UTRs.
MDM2 is an oncogenic E3 ubiquitin ligase best known for targeting the tumor suppressor p53 and is frequently amplified in human cancers, including dedifferentiated liposarcoma (DDLPS). We show that supraphysiological MDM2 expression can be exploited to reprogram its ligase activity toward selective degradation of oncogenic transcriptional machinery. Using a substrate substitution strategy, we developed an MDM2-recruiting degrader dCDK9-010 that targets positive transcription elongation factor b, inducing its proteasomal degradation while simultaneously stabilizing p53. This dual action disrupts RNA polymerase II abundance and elongation, preferentially impairing enhancer-driven transcriptional programs that sustain tumor growth. In DDLPS models, this approach produces potent antitumor activity with favorable pharmacokinetic and safety profiles, triggers apoptosis, and enhances macrophage-mediated tumor cell clearance. These findings establish substrate substitution-based reprogramming of MDM2 as a generalizable targeted protein degradation strategy and identify
MDM2
amplification as a predictive biomarker for therapeutic response across cancer types, with particular relevance to liposarcoma.
Ye Chen, Long Xie, Xian Guan et al.· Cell Death & Disease· 0 citations
BACKGROUND
Tumors that retain wild-type TP53 and rely on MDM2 overexpression to dampen the p53 response were considered prime candidates for therapies based on MDM2 inhibitors (MDM2i). However, clinical trials to date have been disappointing, with limited improvements in progression-free survival, pointing to the existence of intrinsic resistance mechanisms. Building on our previous work demonstrating that TWIST1 attenuates the p53 response in sarcomas, we hypothesized that TWIST1 plays a role in modulating MDM2i efficacy.
METHODS
RNA-sequencing data were integrated with cytotoxicity measurements across a large panel of TP53 wild-type sarcoma cell models. Perturbation experiments were performed using shRNA or CRISPR/Cas9-mediated inhibition, as well as ectopic TWIST1 expression. Cell viability, pathway activation, and transcriptional profile following MDM2i treatment were evaluated in TWIST1-proficient and -deficient models. Co-precipitations, TurboID, molecular docking experiments, and in vitro and in vivo functional assays were employed to characterize the interplay between TWIST1, p53, and MDM2.
RESULTS
TWIST1 expression correlated with reduced sensitivity to multiple MDM2i. TWIST1 inhibition enhanced p53 pathway activation and cell death in response to MDM2i, while TWIST1 overexpression conferred resistance. Mechanistically, we found that TWIST1 directly binds both p53 and MDM2, forming a trimeric complex that facilitates p53:MDM2 interaction, thereby promoting p53 degradation and limiting MDM2i efficacy. Notably, harmine, a compound that promotes TWIST1 degradation, phenocopied the effects of TWIST1 genetic inhibition in augmenting MDM2i sensitivity.
CONCLUSION
TWIST1 confers resistance to MDM2i in TP53 wild-type sarcomas. Targeting TWIST1 restores p53 pathway activation and sensitizes sarcoma cells to MDM2 blockade, establishing TWIST1 as a promising predictive biomarker and therapeutic vulnerability for improving MDM2i efficacy.
S. Piccinin, Bernadetta Szaboova, Flavia Pivetta et al.· Journal of experimental & cl...· 0 citations
BYSL gene encodes the bystin-like (BYSL) protein, a nucleolar protein involved in eukaryotic ribosome biogenesis and essential for 40S ribosomal subunit synthesis. Although BYSL upregulation has been implicated in hepatocellular carcinoma, its mechanistic contribution to tumor progression remains undefined. We observed that BYSL is consistently upregulated across multiple cancer types and is associated with adverse clinicopathological features and poor prognosis, with the strongest clinical relevance observed in hepatocellular carcinoma through the integrative transcriptomic and proteomic analyses. BYSL-knockout suppresses malignant phenotypes, including proliferation, migration, and invasion, and induced G1/S arrest and apoptosis. Mechanistically, loss of BYSL disrupts nucleolar homeostasis and reduces global protein synthesis, thereby activating the RPL5/RPL11-MDM2-p53 axis, leading to p53 stabilization and tumor suppression. Importantly, MYC directly bound to the BYSL promoter and transcriptionally activated its expression, whereas co-targeting BYSL and MYC produced more synergistic antitumor effects than either intervention alone. Collectively, our study reveals that BYSL acts as a pivotal downstream mediator of MYC-regulated ribosome biogenesis and promotes hepatocellular carcinoma progression. Our findings suggest that BYSL may represent a potential therapeutic target for hepatocellular carcinoma; nevertheless, additional in vivo preclinical studies are warranted to validate its translational prospects.
Heyuan Zhao, Huiying Liu, Xia Liu et al.· Cellular Signalling· 0 citations
The tumor suppressor p53 plays a crucial role in preventing cancer development, and its dysfunction is frequently observed in various cancers. This study identifies a novel regulatory interaction between p53 and ITM2A. We found that p53 upregulates ITM2A expression, while ITM2A in turn inhibits p53 function, suggesting a negative feedback loop. ITM2A mRNA levels were reduced across multiple tumor types, particularly in those harboring mutant p53, and low ITM2A expression correlated with poor patient survival. Mechanistically, ITM2A physically interacts with p53, selectively modulates its phosphorylation (reducing Ser392 while enhancing Ser37), and promotes cytoplasmic accumulation of p53. These modifications collectively suppress p53-dependent transcription, an effect consistently observed across multiple cell lines under both basal conditions and upon physiological p53 activation by genotoxic stress. Conversely, ITM2A depletion enhances p53 nuclear accumulation and transcriptional activity. These findings reveal a novel autoregulatory circuit wherein p53 induces ITM2A expression, which then attenuates p53 activity, suggesting ITM2A as a potential prognostic marker and therapeutic target for cancers with dysregulated p53 signaling.
Sim Namkoong, Minsu Jang, Jeong‐In Lee et al.· Cell Cycle· 0 citations
BACKGROUND
Acute myeloid leukemia (AML) has a poor prognosis due to high chemoresistance and recurrence. TRIM24, an E3 ubiquitin ligase, is oncogenic in solid tumors, but its role in AML and regulation of the oncoprotein p110 CUX1 remain unclear.
METHODS
We performed bioinformatic analysis to assess TRIM24 expression, prognosis, and protein-protein interactions. Functional studies used genetic manipulation and pharmacological inhibition in AML cells. Protein interactions were examined by Co-IP, IP-MS, and immunofluorescence. The stability and ubiquitination of p110 CUX1 were examined via CHX chase assays and ubiquitination profiling. The biological and therapeutic significance of the identified axis was validated using cell proliferation, apoptosis assays, drug sensitivity tests, and a CDX mouse model.
RESULTS
TRIM24 is overexpressed in AML and predicts poor prognosis. TRIM24 promotes proliferation and inhibits apoptosis. Mechanistically, TRIM24 functions as a scaffold-like adaptor to recruit USP10 to deubiquitinate and stabilize p110 CUX1 via K48-linked ubiquitin chain cleavage. The TRIM24/USP10/p110 CUX1 axis activates the MAPK signaling pathway, with CUX1 regulating ERK transcription. TRIM24 overexpression enriches DNA repair pathways, conferring cytarabine resistance. Targeting TRIM24 genetically or with dTRIM24 sensitizes AML cells to cytarabine in vitro and in vivo.
CONCLUSION
Our study reveals a novel non-canonical role of TRIM24 as a stabilizer of the p110 CUX1 oncoprotein by recruiting USP10. This TRIM24/USP10/p110 CUX1 axis is critical for AML progression, clinical prognosis, and chemoresistance, presenting a promising therapeutic target for AML treatment.
Zhiyin Ke, Jie Li, L. Zhong et al.· Journal of Translational Med...· 0 citations
Exportin 1 (XPO1) is a key nuclear export receptor that mediates the nuclear export of tumor suppressor proteins and growth-regulatory mRNAs from the nucleus to the cytoplasm. In several types of cancer, XPO1 is overexpressed or hyperactivated, leading to aberrant cytoplasmic sequestration of key tumor suppressors such as p53, p21, p73, FOXO and Rb. This mislocalization abrogates their nuclear transcriptional functions, disrupting cell cycle arrest, apoptosis and DNA repair, thereby promoting uncontrolled proliferation, survival and therapy resistance. Targeting XPO1 with selective inhibitors of nuclear export (SINE) has emerged as a promising anticancer strategy. The present review systematically examines the molecular mechanisms of XPO1-driven tumorigenesis and its rationale as a therapeutic target. The present review focuses on the clinical translation of SINE drugs, especially selinexor (KPT-330), in hematologic and solid tumors, critically assesses the limitations of monotherapy and explores the mechanistic basis for synergistic combination strategies. Ongoing clinical trials and future directions to optimize therapeutic efficacy are also highlighted. Collectively, the present review aims to provide a comprehensive foundation for advancing basic and clinical research on XPO1-targeted therapies.
