Targeting the degradation of cyclin D1 will help to eliminate oncogene addiction

CDK4/6 Inhibitor Resistance in Hormone Receptor-Positive Metastatic Breast Cancer: Translational Research, Clinical Trials, and Future Directions

The emergence of CDK4/6 inhibitors, such as palbociclib, ribociclib, and abemaciclib, has revolutionized the treatment landscape for hormone receptor-positive breast cancer. These agents have demonstrated significant clinical benefits in terms of both progression-free survival and overall survival. However, resistance to CDK4/6 inhibitors remains a challenge, limiting their long-term efficacy. Understanding the complex mechanisms driving resistance is crucial for the development of novel therapeutic strategies and the improvement of patient outcomes. Translational research efforts, such as preclinical models and biomarker studies, offer valuable insight into resistance mechanisms and may guide the identification of novel combination therapies. This review paper aims to outline the reported mechanisms underlying CDK4/6 inhibitor resistance, drawing insights from both clinical data and translational research in order to help direct the future of treatment for hormone receptor-positive metastatic breast cancer.

Ribonucleotide reductase holoenzyme inhibitor COH29 interacts with deubiquitinase ubiquitin-specific protease 2 and downregulates its substrate protein cyclin D1

USP2 contributes to the quality control of multiple oncogenic proteins including cyclin D1, Mdm2, Aurora-A, etc., and it is a potential target for anti-cancer drug development. However, currently only a few inhibitors with moderate inhibition activities against USP2 have been discovered. USP2-targeted active compounds with either new scaffolds or enhanced activities are in need. Here in this study, Ub-AMC hydrolysis assay-based screening against ~4000 commercially available drugs and drug candidates was performed to identify USP2-targeted inhibitors. COH29, which was originally developed as an anti-cancer agent by blocking the function of human ribonucleotide reductase (RNR, IC₅₀  = 16 µM), was found to exhibit an inhibition activity against USP2 with the IC₅₀ value at 2.02 ± 0.16 µM. The following conducted biophysical and biochemical experiments demonstrated that COH29 could specifically interact with USP2 and inhibit its enzymatic activity in a noncompetitive inhibition mode (K_i  = 1.73 ± 0.14 µM). Since COH29 shows similar inhibitory potencies against RNR (RRM2) and USP2, USP2 inhibition-dependent cellular consequences of COH29 are expected. The results of cellular assays confirmed that the application of COH29 could downregulate the level of cyclin D1 by enhancing its degradation via ubiquitin-proteasome system (UPS), and the modulation effect of COH29 on cyclin D1 is independent of RRM2. Since cyclin D1 acts as an oncogenic driver in human cancer, our findings suggest that USP2 might be a promising therapeutic target for cyclin D1-addicted cancers, and COH29 could serve as a starting compound for high selectivity inhibitor development against USP2.

The Involvement of Ubiquitination Machinery in Cell Cycle Regulation and Cancer Progression

The cell cycle is a collection of events by which cellular components such as genetic materials and cytoplasmic components are accurately divided into two daughter cells. The cell cycle transition is primarily driven by the activation of cyclin-dependent kinases (CDKs), which activities are regulated by the ubiquitin-mediated proteolysis of key regulators such as cyclins, CDK inhibitors (CKIs), other kinases and phosphatases. Thus, the ubiquitin-proteasome system (UPS) plays a pivotal role in the regulation of the cell cycle progression via recognition, interaction, and ubiquitination or deubiquitination of key proteins. The illegitimate degradation of tumor suppressor or abnormally high accumulation of oncoproteins often results in deregulation of cell proliferation, genomic instability, and cancer occurrence. In this review, we demonstrate the diversity and complexity of the regulation of UPS machinery of the cell cycle. A profound understanding of the ubiquitination machinery will provide new insights into the regulation of the cell cycle transition, cancer treatment, and the development of anti-cancer drugs.

Adiponectin and Thyroid Cancer: Insight into the Association between Adiponectin and Obesity

In recent decades, the incidence and diagnosis of thyroid cancer have risen dramatically, and thyroid cancer has now become the most common endocrine cancer in the world. The onset of thyroid cancer is insidious, and its progression is slow and difficult to detect. Therefore, early prevention and treatment have important strategic significance. Moreover, an in-depth exploration of the pathogenesis of thyroid cancer is key to early prevention and treatment. Substantial evidence supports obesity as an independent risk factor for thyroid cancer. Adipose tissue dysfunction in the obese state is accompanied by dysregulation of a variety of adipocytokines. Adiponectin (APN) is one of the most pivotal adipocytokines, and its connection with obesity and obesity-related disease has gradually become a hot topic in research. Recently, the association between APN and thyroid cancer has received increasing attention. The purpose of this review is to systematically review previous studies, give prominence to APN, focus on the relationship between APN, obesity and thyroid cancer, and uncover the underlying pathogenic mechanisms.

Benzethonium chloride suppresses lung cancer tumorigenesis through inducing p38-mediated cyclin D1 degradation

Lung cancer is the leading cause of cancer-related deaths worldwide, but effective therapeutics is limited. This study aims to identify novel anticancer strategy from a Food and Drug Administration (FDA)-approved drug library consisting of 528 compounds. Benzethonium Chloride (BZN), a FDA-approved drug for anti-infective, was found to markedly induce apoptosis and inhibit proliferation and colony formation ability of lung cancer cells in dose- and time-dependent manners. BZN also enhanced the sensitivity of lung cancer cells to gefitinib, the first-line treatment strategy for selected lung cancer patients. Furthermore, BZN significantly delayed the growth of tumor xenografts in nude mice by increasing apoptosis and decreasing Ki-67 proliferation index, without obvious toxic effects to the vital organs of animals. Mechanistically, quantitative proteomics coupled with bioinformatics analyses and a series of functional assays demonstrated that BZN induced cell cycle arrest at G1 phase, and this was associated with an increase in p38-mediated phosphorylation at threonine 286 (T286) and accelerated degradation of cyclin D1. Our findings provide the first evidence that BZN could be a promising therapeutic agent in lung cancer treatment.

Ubiquitin specific protease 2 acts as a key modulator for the regulation of cell cycle by adiponectin and leptin in cancer cells

Adiponectin and leptin, both produced from adipose tissue, cause cell cycle arrest and progression, respectively in cancer cells. Ubiquitin specific protease-2 (USP-2), a deubiquitinating enzyme, is known to impair proteasome-induced degradation of cyclin D1, a critical cell cycle regulator. Herein, we investigated the effects of these adipokines on USP-2 expression and its potential role in the modulation of cell cycle. Treatment with globular adiponectin (gAcrp) decreased, whereas leptin increased USP-2 expression both in human hepatoma and breast cancer cells. In addition, overexpression or gene silencing of USP-2 affected cyclin D1 expression and cell cycle progression/arrest by adipokines. Adiponectin and leptin also modulated in vitro proteasomal activity, which was partially dependent on USP-2 expression. Taken together, our results reveal that modulation of USP-2 expression plays a crucial role in cell cycle regulation by adipokines. Thus, USP-2 would be a promising therapeutic target for the modulation of cancer cell growth by adipokines.

Mutations and deregulation of Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades which alter therapy response

The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in upstream signaling molecules such as receptor tyrosine kinases (RTK). Certain components of these pathways, RAS, NF1, BRAF, MEK1, DUSP5, PP2A, PIK3CA, PIK3R1, PIK3R4, PIK3R5, IRS4, AKT, NFKB1, MTOR, PTEN, TSC1, and TSC2 may also be activated/inactivated by mutations or epigenetic silencing. Upstream mutations in one signaling pathway or even in downstream components of the same pathway can alter the sensitivity of the cells to certain small molecule inhibitors. These pathways have profound effects on proliferative, apoptotic and differentiation pathways. Dysregulation of components of these cascades can contribute to: resistance to other pathway inhibitors, chemotherapeutic drug resistance, premature aging as well as other diseases. This review will first describe these pathways and discuss how genetic mutations and epigenetic alterations can result in resistance to various inhibitors.

NCI's provocative questions on cancer: some answers to ignite discussion

National Cancer Institute has announced 24 provocative questions on cancer. Here I try to answer some of them by linking the dots of existing knowledge.

Therapeutic strategies for targeting ras proteins

Ras genes are frequently activated in cancer. Attempts to develop drugs that target mutant Ras proteins have, so far, been unsuccessful. Tumors bearing these mutations, therefore, remain among the most difficult to treat. Most efforts to block activated Ras have focused on pathways downstream. Drugs that inhibit Raf kinase have shown clinical benefit in the treatment of malignant melanoma. However, these drugs have failed to show clinical benefit in Ras mutant tumors. It remains unclear to what extent Ras depends on Raf kinase for transforming activity, even though Raf proteins bind directly to Ras and are certainly major effectors of Ras action in normal cells and in development. Furthermore, Raf kinase inhibitors can lead to paradoxical activation of the MAPK pathway. MEK inhibitors block the Ras-MAPK pathway, but often activate the PI3'-kinase, and have shown little clinical benefit as single agents. This activation is mediated by EGF-R and other receptor tyrosine kinases through relief of a negative feedback loop from ERK. Drug combinations that target multiple points within the Ras signaling network are likely to be necessary to achieve substantial clinical benefit. Other effectors may also contribute to Ras signaling and provide a source of targets. In addition, unbiased screens for genes necessary for Ras transformation have revealed new potential targets and have added to our understanding of Ras cancer biology.

Oncogene addiction in gliomas: implications for molecular targeted therapy

Oncogene addiction is a phenomenon that the survival of cancer cells depends on an activated oncogene or inactivation of tumor suppressor gene, and is regarded as the 'Achilles heel' of the successful molecular targeted therapies in cancer. However, the role of oncogene addiction in gliomas has not been elucidated systematically. In this review, we summarize the current experimental and clinical evidence for the concept of oncogene addiction and describe the mechanisms explaining oncogene addiction in gliomas. And the clinical implications for oncogene addiction in molecular targeted therapy are further emphasized. In addition, we discuss future direction for defining complex "oncogene addiction network" through the integrated analysis of multiple platforms in the flow of genetic information in gliomagenesis.

Oncogenic role of EAPII in lung cancer development and its activation of the MAPK-ERK pathway

Cancer progression involves multiple complex and interdependent steps, including progressive proliferation, angiogenesis and metastases. The complexity of these processes requires a comprehensive elucidation of the integrated signaling networks for better understanding. EAPII interacts with multiple cancer-related proteins, but its biological significance in cancer development remains unknown. In this report we identified the elevated level of EAPII protein in non-small-cell lung carcinoma (NSCLC) patients and NSCLC cell lines in culture. The oncogenic role of EAPII in lung cancer development was demonstrated using NSCLC cells with genetic manipulations that influence EAPII expression: EAPII overexpression increases proliferation of NSCLC cells with an accelerated transition of cell cycle and facilitates xenograft tumor growth in vivo; EAPII knockdown results in apoptosis of NSCLC cells and reduces xenograft tumor formation. To further explore the mechanism of EAPII's oncogenic role in lung cancer development and to elucidate the potential signaling pathway(s) that EAPII may impact, we employed antibody array to investigate the alternation of the major signaling pathways in NSCLC cells with altered EAPII level. We found that EAPII overexpression significantly activated Raf1 and ERK1/2, but not c-Jun N-terminal kinase and p38 pathways. Consistently, the protein and mRNA levels of MYC and cyclin D1, which are targets of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK–ERK) pathway, are significantly increased by EAPII overexpression. Taken together, we demonstrated that EAPII is an oncogenic factor and the activation of MAPK–ERK signaling pathway by EAPII may contribute to lung cancer development.