Pharmacological targeting of CBP/p300 drives a redox/autophagy axis leading to senescence-induced growth arrest in non-small cell lung cancer cells

The important role of the histone acetyltransferases p300/CBP in cancer and the promising anticancer effects of p300/CBP inhibitors

Histone acetyltransferases p300 (E1A-associated protein p300) and CBP (CREB binding protein), collectively known as p300/CBP due to shared sequence and functional synergy, catalyze histone H3K27 acetylation and consequently induce gene transcription. p300/CBP over-expression or over-activity activates the transcription of oncogenes, leading to cancer cell growth, resistance to apoptosis, tumor initiation and development. The discovery of small molecule inhibitors targeting p300/CBP histone acetyltransferase activity, bromodomains, dual inhibitors of p300/CBP and BRD4 bromodomains, as well as proteolysis-targeted-chimaera p300/CBP protein degraders, marks significant progress in cancer therapeutics. These inhibitors and degraders induce histone H3K27 deacetylation, reduce oncogene expression and cancer cell proliferation, promote cancer cell death, and decrease tumor progression in mice. Furthermore, p300/CBP inhibitors and protein degraders have been demonstrated to exert synergy when in combination with conventional radiotherapy, chemotherapy and BRD4 inhibitors in vitro as well as in mice. Importantly, two p300/CBP bromodomain inhibitors, CCS1477 and FT-7051, as well as the dual p300/CBP and BRD4 bromodomain inhibitor NEO2734 have entered Phase I and IIa clinical trials in patients with advanced and refractory hematological malignancies or solid tumors. Taken together, the identification of p300/CBP as critical drivers of tumorigenesis and the development of p300/CBP inhibitors and proteolysis-targeted-chimaera protein degraders represent promising avenues for clinical translation of novel cancer therapeutics.

Genetic dysregulation of EP300 in cancers in light of cancer epigenome control - targeting of p300-proficient and -deficient cancers

Some cancer types including bladder, cervical, and uterine cancers are characterized by frequent mutations in EP300 that encode histone acetyltransferase p300. This enzyme can act both as a tumor suppressor and oncogene. In this review, we describe the role of p300 in cancer initiation and progression regarding EP300 aberrations that have been identified in TGCA Pan-Cancer Atlas studies and we also discuss possible anticancer strategies that target EP300 mutated cancers. Copy number alterations, truncating mutations, and abnormal EP300 transcriptions that affect p300 abundance and activity are associated with several pathological features such as tumor grading, metastases, and patient survival. Elevated EP300 correlates with a higher mRNA level of other epigenetic factors and chromatin remodeling enzymes that co-operate with p300 in creating permissive conditions for malignant transformation, tumor growth and metastases. The status of EP300 expression can be considered as a prognostic marker for anticancer immunotherapy efficacy, as EP300 mutations are followed by an increased expression of PDL-1.HAT activators such as CTB or YF2 can be applied for p300-deficient patients, whereas the natural and synthetic inhibitors of p300 activity, as well as dual HAT/bromodomain inhibitors and the PROTAC degradation of p300, may serve as strategies in the fight against p300-fueled cancers.

Pharmacological targeting of P300/CBP reveals EWS::FLI1-mediated senescence evasion in Ewing sarcoma

Ewing sarcoma (ES) poses a significant therapeutic challenge due to the difficulty in targeting its main oncodriver, EWS::FLI1. We show that pharmacological targeting of the EWS::FLI1 transcriptional complex via inhibition of P300/CBP drives a global transcriptional outcome similar to direct knockdown of EWS::FLI1, and furthermore yields prognostic risk factors for ES patient outcome. We find that EWS::FLI1 upregulates LMNB1 via repetitive GGAA motif recognition and acetylation codes in ES cells and EWS::FLI1-permissive mesenchymal stem cells, which when reversed by P300 inhibition leads to senescence of ES cells. P300-inhibited senescent ES cells can then be eliminated by senolytics targeting the PI3K signaling pathway. The vulnerability of ES cells to this combination therapy suggests an appealing synergistic strategy for future therapeutic exploration.

AR coactivators, CBP/p300, are critical mediators of DNA repair in prostate cancer

Castration resistant prostate cancer (CRPC) remains an incurable disease stage with ineffective treatments options. Here, the androgen receptor (AR) coactivators CBP/p300, which are histone acetyltransferases, were identified as critical mediators of DNA damage repair (DDR) to potentially enhance therapeutic targeting of CRPC. Key findings demonstrate that CBP/p300 expression increases with disease progression and selects for poor prognosis in metastatic disease. CBP/p300 bromodomain inhibition enhances response to standard of care therapeutics. Functional studies, CBP/p300 cistrome mapping, and transcriptome in CRPC revealed that CBP/p300 regulates DDR. Further mechanistic investigation showed that CBP/p300 attenuation via therapeutic targeting and genomic knockdown decreases homologous recombination (HR) factors in vitro, in vivo, and in human prostate cancer (PCa) tumors ex vivo. Similarly, CBP/p300 expression in human prostate tissue correlates with HR factors. Lastly, targeting CBP/p300 impacts HR-mediate repair and patient outcome. Collectively, these studies identify CBP/p300 as drivers of PCa tumorigenesis and lay the groundwork to optimize therapeutic strategies for advanced PCa via CBP/p300 inhibition, potentially in combination with AR-directed and DDR therapies.

AR coactivators, CBP/p300, are critical mediators of DNA repair in prostate cancer

Castration resistant prostate cancer (CRPC) remains an incurable disease stage with ineffective treatments options. Here, the androgen receptor (AR) coactivators CBP/p300, which are histone acetyltransferases, were identified as critical mediators of DNA damage repair (DDR) to potentially enhance therapeutic targeting of CRPC. Key findings demonstrate that CBP/p300 expression increases with disease progression and selects for poor prognosis in metastatic disease. CBP/p300 bromodomain inhibition enhances response to standard of care therapeutics. Functional studies, CBP/p300 cistrome mapping, and transcriptome in CRPC revealed that CBP/p300 regulates DDR. Further mechanistic investigation showed that CBP/p300 attenuation via therapeutic targeting and genomic knockdown decreases homologous recombination (HR) factors in vitro, in vivo, and in human prostate cancer (PCa) tumors ex vivo. Similarly, CBP/p300 expression in human prostate tissue correlates with HR factors. Lastly, targeting CBP/p300 impacts HR-mediate repair and patient outcome. Collectively, these studies identify CBP/p300 as drivers of PCa tumorigenesis and lay the groundwork to optimize therapeutic strategies for advanced PCa via CBP/p300 inhibition, potentially in combination with AR-directed and DDR therapies.

Targeting SMAD-Dependent Signaling: Considerations in Epithelial and Mesenchymal Solid Tumors

SMADs are the canonical intracellular effector proteins of the TGF-β (transforming growth factor-β). SMADs translocate from plasma membrane receptors to the nucleus regulated by many SMAD-interacting proteins through phosphorylation and other post-translational modifications that govern their nucleocytoplasmic shuttling and subsequent transcriptional activity. The signaling pathway of TGF-β/SMAD exhibits both tumor-suppressing and tumor-promoting phenotypes in epithelial-derived solid tumors. Collectively, the pleiotropic nature of TGF-β/SMAD signaling presents significant challenges for the development of effective cancer therapies. Here, we review preclinical studies that evaluate the efficacy of inhibitors targeting major SMAD-regulating and/or -interacting proteins, particularly enzymes that may play important roles in epithelial or mesenchymal compartments within solid tumors.

FOXO1, a tiny protein with intricate interactions: Promising therapeutic candidate in lung cancer

Nowadays, lung cancer is the most common cause of cancer-related deaths in both men and women globally. Despite the development of extremely efficient targeted agents, lung cancer progression and drug resistance remain serious clinical issues. Increasing knowledge of the molecular mechanisms underlying progression and drug resistance will enable the development of novel therapeutic methods. It has been revealed that transcription factors (TF) dysregulation, which results in considerable expression modifications of genes, is a generally prevalent phenomenon regarding human malignancies. The forkhead box O1 (FOXO1), a member of the forkhead transcription factor family with crucial roles in cell fate decisions, is suggested to play a pivotal role as a tumor suppressor in a variety of malignancies, especially in lung cancer. FOXO1 is involved in diverse cellular processes and also has clinical significance consisting of cell cycle arrest, apoptosis, DNA repair, oxidative stress, cancer prevention, treatment, and chemo/radioresistance. Based on the critical role of FOXO1, this transcription factor appears to be an appropriate target for future drug discovery in lung cancers. This review focused on the signaling pathways, and molecular mechanisms involved in FOXO1 regulation in lung cancer. We also discuss pharmacological compounds that are currently being administered for lung cancer treatment by affecting FOXO1 and also point out the essential role of FOXO1 in drug resistance. Future preclinical research should assess combination drug strategies to stimulate FOXO1 and its upstream regulators as potential strategies to treat resistant or advanced lung cancers.

Transcriptional co-activators: emerging roles in signaling pathways and potential therapeutic targets for diseases

Specific cell states in metazoans are established by the symphony of gene expression programs that necessitate intricate synergic interactions between transcription factors and the co-activators. Deregulation of these regulatory molecules is associated with cell state transitions, which in turn is accountable for diverse maladies, including developmental disorders, metabolic disorders, and most significantly, cancer. A decade back most transcription factors, the key enablers of disease development, were historically viewed as 'undruggable'; however, in the intervening years, a wealth of literature validated that they can be targeted indirectly through transcriptional co-activators, their confederates in various physiological and molecular processes. These co-activators, along with transcription factors, have the ability to initiate and modulate transcription of diverse genes necessary for normal physiological functions, whereby, deregulation of such interactions may foster tissue-specific disease phenotype. Hence, it is essential to analyze how these co-activators modulate specific multilateral processes in coordination with other factors. The proposed review attempts to elaborate an in-depth account of the transcription co-activators, their involvement in transcription regulation, and context-specific contributions to pathophysiological conditions. This review also addresses an issue that has not been dealt with in a comprehensive manner and hopes to direct attention towards future research that will encompass patient-friendly therapeutic strategies, where drugs targeting co-activators will have enhanced benefits and reduced side effects. Additional insights into currently available therapeutic interventions and the associated constraints will eventually reveal multitudes of advanced therapeutic targets aiming for disease amelioration and good patient prognosis.

In silico screening and identification of potential drug against p300 acetyltransferase activity in breast cancer via drug repurposing approach

Emerging evidence portray the involvement of epigenomic reprogramming in the onset and progression of several malignancies, including breast cancer. Histone acetyltransferase (HAT) p300 is a critical epigenetic regulator that acts as a transcription co-activator and regulates various cellular processes. p300 is overexpressed in breast cancer and promotes cellular invasion and survival, making it a promising druggable target. In this study, the relevance of p300 in different cancer pathways was established. Virtual screening of the FDA-approved drug library was carried out using molecular docking, and the top 10 potential repurposed drugs were identified. Further, recalculation of binding free energy of drug-p300 complexes was carried out using molecular mechanics Poisson-Boltzmann and surface area (MM-PBSA) method after molecular dynamic simulation. Based on molecular dynamic simulation parameters and binding free energy analysis, two drugs, namely Netarsudil (-305.068 kJ/mol) and Imatinib (-260.457 kJ/mol), were identified as potential repurposed drugs to inhibit the activity of p300. In conclusion, these findings suggest, Netarsudil and Imatinib might be a potential repurposed drug to combat breast cancer via p300 inhibition.Communicated by Ramaswamy H. Sarma.

Targeting epigenetic regulators to overcome drug resistance in cancers

Drug resistance is mainly responsible for cancer recurrence and poor prognosis. Epigenetic regulation is a heritable change in gene expressions independent of nucleotide sequence changes. As the common epigenetic regulation mechanisms, DNA methylation, histone modification, and non-coding RNA regulation have been well studied. Increasing evidence has shown that aberrant epigenetic regulations contribute to tumor resistance. Therefore, targeting epigenetic regulators represents an effective strategy to reverse drug resistance. In this review, we mainly summarize the roles of epigenetic regulation in tumor resistance. In addition, as the essential factors for epigenetic modifications, histone demethylases mediate the histone or genomic DNA modifications. Herein, we comprehensively describe the functions of the histone demethylase family including the lysine-specific demethylase family, the Jumonji C-domain-containing demethylase family, and the histone arginine demethylase family, and fully discuss their regulatory mechanisms related to cancer drug resistance. In addition, therapeutic strategies, including small-molecule inhibitors and small interfering RNA targeting histone demethylases to overcome drug resistance, are also described.