CDK4/6 inhibitors in breast cancer therapy: Current practice and future opportunities

Systematic annotation of orphan RNAs reveals blood-accessible molecular barcodes of cancer identity and cancer-emergent oncogenic drivers

From extrachromosomal DNA to neo-peptides, the broad reprogramming of the cancer genome leads to the emergence of molecules that are specific to the cancer state. We recently described orphan non-coding RNAs (oncRNAs) as a class of cancer-specific small RNAs with the potential to play functional roles in breast cancer progression1. Here, we report a systematic and comprehensive search to identify, annotate, and characterize cancer-emergent oncRNAs across 32 tumor types. We also leverage large-scale in vivo genetic screens in xenografted mice to functionally identify driver oncRNAs in multiple tumor types. We have not only discovered a large repertoire of oncRNAs, but also found that their presence and absence represent a digital molecular barcode that faithfully captures the types and subtypes of cancer. Importantly, we discovered that this molecular barcode is partially accessible from the cell-free space as some oncRNAs are secreted by cancer cells. In a large retrospective study across 192 breast cancer patients, we showed that oncRNAs can be reliably detected in the blood and that changes in the cell-free oncRNA burden captures both short-term and long-term clinical outcomes upon completion of a neoadjuvant chemotherapy regimen. Together, our findings establish oncRNAs as an emergent class of cancer-specific non-coding RNAs with potential roles in tumor progression and clinical utility in liquid biopsies and disease monitoring.

The anticancer potential of chemical constituents of Moringa oleifera targeting CDK-2 inhibition in estrogen receptor positive breast cancer using in-silico and in vitro approches

Most of the breast cancers are estrogen receptor-positive recurring with a steady rate of up to 20 years dysregulating the normal cell cycle. Dinaciclib is still in clinical trials and considered as a research drug against such cancers targeting CDK2.The major goal of this study was to identify the potential inhibitors of CDK-2 present in Moringa oleifera for treating hormonal receptor positive breast cancers. For this purpose, in silico techniques; molecular docking, MM-GBSA and molecular dynamics simulations were employed to screen Moringa oleifera compounds and their anticancer potential was determined against CDK-2 protein targets. Among 36 compounds of Moringa oleifera reported in literature, chlorogenic acid (1), quercetin (2), ellagic acid (3), niazirin (4), and kaempferol (5) showed good affinity with the target. The interaction of the compounds was visualized using PYMOL software. The profiles of absorption, distribution, metabolism, excretion (ADME) and toxicity were determined using SWISS and ProTox II webservers. The MTT assay was performed in-vitro using MCF-7 cancer cell lines to validate the anticancer potential of Moringa oleifera leaf extract.MTT assay results revealed no significant change in proliferation of Mcf-7 cells following 24 h treatment with fraction A (petroleum ether). However, significant antiproliferative effect was observed at 200 µg/mL dose of fraction B (ethyl acetate) and cell viability was reduced to 40%.In conclusion, the data suggested that all the compounds with highest negative docking score than the reference could be the potential candidates for cyclin dependent kinase-2 (CDK-2) inhibition while ellagic acid, chlorogenic acid and quercetin being the most stable and potent inhibitors to treat estrogen receptor positive breast cancer targeting CDK-2. Moreover, the data suggested that further investigation is required to determine the optimum dose for significant antiproliferative effects using in-vivo models to validate our findings of in-silico analysis.

Cyclin-dependent kinases: Masters of the eukaryotic universe

A family of structurally related cyclin-dependent protein kinases (CDKs) drives many aspects of eukaryotic cell function. Much of the literature in this area has considered individual members of this family to act primarily either as regulators of the cell cycle, the context in which CDKs were first discovered, or as regulators of transcription. Until recently, CDK7 was the only clear example of a CDK that functions in both processes. However, new data points to several "cell-cycle" CDKs having important roles in transcription and some "transcriptional" CDKs having cell cycle-related targets. For example, novel functions in transcription have been demonstrated for the archetypal cell cycle regulator CDK1. The increasing evidence of the overlap between these two CDK types suggests that they might play a critical role in coordinating the two processes. Here we review the canonical functions of cell-cycle and transcriptional CDKs, and provide an update on how these kinases collaborate to perform important cellular functions. We also provide a brief overview of how dysregulation of CDKs contributes to carcinogenesis, and possible treatment avenues. This article is categorized under: RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes RNA Processing > 3' End Processing RNA Processing > Splicing Regulation/Alternative Splicing.

Modeling breast cancer proliferation, drug synergies, and alternating therapies

Estrogen receptor positive (ER+) breast cancer is responsive to a number of targeted therapies used clinically. Unfortunately, the continuous application of targeted therapy often results in resistance, driving the consideration of combination and alternating therapies. Toward this end, we developed a mathematical model that can simulate various mono, combination, and alternating therapies for ER + breast cancer cells at different doses over long time scales. The model is used to look for optimal drug combinations and predicts a significant synergism between Cdk4/6 inhibitors in combination with the anti-estrogen fulvestrant, which may help explain the clinical success of adding Cdk4/6 inhibitors to anti-estrogen therapy. Furthermore, the model is used to optimize an alternating treatment protocol so it works as well as monotherapy while using less total drug dose.

CDK4/6 Inhibitors in Pancreatobiliary Cancers: Opportunities and Challenges

Existing treatment strategies for pancreatobiliary malignancies are limited. Nowadays, surgery is the only path to cure these types of cancer, but only a small number of patients present with resectable tumors at the time of diagnosis. The notoriously poor prognosis, lack of diverse treatment options associated with pancreaticobiliary cancers, and their resistance to current therapies reflect the urge for the development of novel therapeutic targets. Cyclin-dependent kinase 4/6 (CDK4/6) inhibitors have emerged as an attractive therapeutic strategy in a number of cancers since their approval for treatment in patients with ER+/HER- breast cancer in combination with antiestrogens. In this article, we discuss the therapeutic potential of CDK4/6 inhibitors in pancreatobiliary cancers, notably cholangiocarcinoma and pancreatic ductal adenocarcinoma.

Deregulated E2F Activity as a Cancer-Cell Specific Therapeutic Tool

The transcription factor E2F, the principal target of the tumor suppressor pRB, plays crucial roles in cell proliferation and tumor suppression. In almost all cancers, pRB function is disabled, and E2F activity is enhanced. To specifically target cancer cells, trials have been undertaken to suppress enhanced E2F activity to restrain cell proliferation or selectively kill cancer cells, utilizing enhanced E2F activity. However, these approaches may also impact normal growing cells, since growth stimulation also inactivates pRB and enhances E2F activity. E2F activated upon the loss of pRB control (deregulated E2F) activates tumor suppressor genes, which are not activated by E2F induced by growth stimulation, inducing cellular senescence or apoptosis to protect cells from tumorigenesis. Deregulated E2F activity is tolerated in cancer cells due to inactivation of the ARF-p53 pathway, thus representing a feature unique to cancer cells. Deregulated E2F activity, which activates tumor suppressor genes, is distinct from enhanced E2F activity, which activates growth-related genes, in that deregulated E2F activity does not depend on the heterodimeric partner DP. Indeed, the ARF promoter, which is specifically activated by deregulated E2F, showed higher cancer-cell specific activity, compared to the E2F1 promoter, which is also activated by E2F induced by growth stimulation. Thus, deregulated E2F activity is an attractive potential therapeutic tool to specifically target cancer cells.

Immunotherapy: Review of the Existing Evidence and Challenges in Breast Cancer

Breast cancer (BC) is a representative malignant tumor that affects women across the world, and it is the main cause of cancer-related deaths in women. Although a large number of treatment methods have been developed for BC in recent years, the results are sometimes unsatisfying. In recent years, treatments of BC have been expanded with immunotherapy. In our article, we list some tumor markers related to immunotherapy for BC. Moreover, we introduce the existing relatively mature immunotherapy and the markers' pathogenesis are involved. The combination of immunotherapy and other therapies for BC are introduced in detail, including the combination of immunotherapy and chemotherapy, the combined use of immunosuppressants and chemotherapy drugs, immunotherapy and molecular targeted therapy. We summarize the clinical effects of these methods. In addition, this paper also makes a preliminary exploration of the combination of immunotherapy, radiotherapy, and nanotechnology for BC.

Clinical Efficacy and Whole-Exome Sequencing of Liquid Biopsies in a Phase IB/II Study of Bazedoxifene and Palbociclib in Advanced Hormone Receptor-Positive Breast Cancer

PURPOSE

Sensitivity to endocrine therapy (ET) is critical for the clinical benefit from the combination of palbociclib plus ET in hormone receptor-positive/HER2-negative (HR+/HER2-) advanced breast cancer. Bazedoxifene is a third-generation selective estrogen receptor (ER) modulator and selective ER degrader with activity in preclinical models of endocrine-resistant breast cancer, including models harboring ESR1 mutations. Clinical trials in healthy women showed that bazedoxifene is well tolerated.

PATIENTS AND METHODS

We conducted a phase Ib/II study of bazedoxifene plus palbociclib in patients with HR+/HER2- advanced breast cancer who progressed on prior ET (N = 36; NCT02448771).

RESULTS

The study met its primary endpoint, with a clinical benefit rate of 33.3%, and the safety profile was consistent with what has previously been seen with palbociclib monotherapy. The median progression-free survival (PFS) was 3.6 months [95% confidence interval (CI), 2.0-7.2]. An activating PIK3CA mutation at baseline was associated with a shorter PFS (HR = 4.4; 95% CI, 1.5-13; P = 0.0026), but activating ESR1 mutations did not impact the PFS. Longitudinal plasma circulating tumor DNA whole-exome sequencing (WES; N = 68 plasma samples) provided an overview of the tumor heterogeneity and the subclonal genetic evolution, and identified actionable mutations acquired during treatment.

CONCLUSIONS

The combination of palbociclib and bazedoxifene has clinical efficacy and an acceptable safety profile in a heavily pretreated patient population with advanced HR+/HER2- breast cancer. These results merit continued investigation of bazedoxifene in breast cancer.

Targeting the Retinoblastoma/E2F repressive complex by CDK4/6 inhibitors amplifies oncolytic potency of an oncolytic adenovirus

CDK4/6 inhibitors (CDK4/6i) and oncolytic viruses are promising therapeutic agents for the treatment of various cancers. As single agents, CDK4/6 inhibitors that are approved for the treatment of breast cancer in combination with endocrine therapy cause G1 cell cycle arrest, whereas adenoviruses induce progression into S-phase in infected cells as an integral part of the their life cycle. Both CDK4/6 inhibitors and adenovirus replication target the Retinoblastoma protein albeit for different purposes. Here we show that in combination CDK4/6 inhibitors potentiate the anti-tumor effect of the oncolytic adenovirus XVir-N-31 in bladder cancer and murine Ewing sarcoma xenograft models. This increase in oncolytic potency correlates with an increase in virus-producing cancer cells, enhanced viral genome replication, particle formation and consequently cancer cell killing. The molecular mechanism that regulates this response is fundamentally based on the reduction of Retinoblastoma protein expression levels by CDK4/6 inhibitors.

Neither CDK4/6 inhibitors nor oncolytic adenoviruses show high efficiency as monotherapy in the treatment of cancer. Authors show here that when combined, CDK4/6 inhibitors deplete Retinoblastoma protein levels, which leads to more efficient virus replication and an increase in oncolytic virus-producing cancer cells and thus to efficient anti-tumor response in mouse xenograft sarcoma models.

Molecular perspective on targeted therapy in breast cancer: a review of current status

Breast cancer is categorized at the molecular level according to the status of certain hormone and growth factor receptors, and this classification forms the basis of current diagnosis and treatment. The development of resistance to treatment and recurrence of the disease have led researchers to develop new therapies. In recent years, most of the research in the field of oncology has focused on the development of targeted therapies, which are treatment methods developed directly against molecular abnormalities. Promising advances have been made in clinical trials investigating the effect of these new treatment modalities and their combinations with existing therapeutic treatments in the treatment of breast cancer. Monoclonal antibodies, tyrosine kinase inhibitors, antibody–drug conjugates, PI3K/Akt/mTOR pathway inhibitors, cyclin-dependent kinase 4/6 inhibitors, anti-angiogenic drugs, PARP inhibitors are among the targeted therapies used in breast cancer treatment. In this review, we aim to present a molecular view of recently approved target agents used in breast cancer.

BCL2A1 regulates Canady Helios Cold Plasma-induced cell death in triple-negative breast cancer

Breast cancer is the leading cause of cancer death among women. Triple-negative breast cancer (TNBC) has a poor prognosis and frequently relapses early compared with other subtypes. The Cold Atmospheric Plasma (CAP) is a promising therapy for prognostically poor breast cancer such as TNBC. The Canady Helios Cold Plasma (CHCP) induces cell death in the TNBC cell line without thermal damage, however, the mechanism of cell death by CAP treatment is ambiguous and the mechanism of resistance to cell death in some subset of cells has not been addressed. We investigate the expression profile of 48 apoptotic and 35 oxidative gene markers after CHCP treatment in six different types of breast cancer cell lines including luminal A (ER+ PR+/-HER2-), luminal B (ER+PR+/-HER2+), (ER-PR-HER2+), basal-like: ER-PR-HER2- cells were tested with CHCP at different power settings and at 4 different incubation time. The expression levels of the gene markers were determined at 4 different intervals after the treatment. The protein expression of BCL2A1 was only induced after CHCP treatment in TNBC cell lines (p < 0.01), whereas the HER2-positive and ER, PR positive cell lines showed little or no expression of BCL2A1. The BCL2A1 and TNF-alpha expression levels showed a significant correlation within TNBC cell lines (p < 0.01). Silencing BCL2A1 mRNA by siRNA increased the potency of the CHCP treatment. A Combination of CHCP and CPI203, a BET bromodomain inhibitor, and a BCL2A1 antagonist increased the CHCP-induced cell death (p < 0.05). Our results revealed that BCL2A1 is a key gene for resistance during CHCP induced cell death. This resistance in TNBCs could be reversed with a combination of siRNA or BCL2A1 antagonist-CHCP therapy.

Resistance to endocrine therapy in HR + and/or HER2 + breast cancer: the most promising predictive biomarkers

Breast cancer is the most common cancer in women. It is a heterogeneous disease, encompassing different biological subtypes that differ in histological features, outcomes, clinical behaviour and different molecular subtypes. Therapy has progressed substantially over the past years with a reduction both for locoregional and systemic therapy. Endocrine therapies have considerably reduced cancer recurrence and mortality. Despite the major diagnostic and therapeutic innovations, resistance to therapy has become a main challenge, especially in metastatic breast cancer, and became a major factor limiting the use of endocrine therapeutic agents in ER positive breast cancers. Approximately 50% of patients with ER positive metastatic disease achieve a complete or partial response with endocrine therapy. However, in the remaining patients, the benefit is limited due to resistance, intrinsic or acquired, resulting in disease progression and poor outcome.Tumour heterogeneity as well as acquired genetic changes and therapeutics pressure have been involved in the endocrine therapy resistance. Nowadays, targeted sequencing of genes involved in cancer has provided insights about genomic tumour evolution throughout treatment and resistance driver mutations. Several studies have described multiple alterations in receptor tyrosine kinases, signalling pathways such as Phosphoinositide-3-kinase-protein kinase B/Akt/mTOR (PI3K/Akt/mTOR) and Mitogen-activated protein kinase (MAPK), cell cycle machinery and their implications in endocrine treatment failure.One of the current concern in cancer is personalized therapy. The focus has been the discovery of new potentially predictive biomarkers capable to identify reliably the most appropriate therapy regimen and which patients will experience disease relapse. The major concern is also to avoid overtreatment/undertreatment and development of resistance.This review focuses on the most promising predictive biomarkers of resistance in estrogen receptor-positive breast cancer and the emerging role of circulating free-DNA as a powerful tool for longitudinal monitoring of tumour molecular profile throughout treatment.

FGFR1 Overexpression Induces Cancer Cell Stemness and Enhanced Akt/Erk-ER Signaling to Promote Palbociclib Resistance in Luminal A Breast Cancer Cells

Resistance to CDK4/6 inhibitors (CDKis) is emerging as a clinical challenge. Identification of the factors contributing to CDKi resistance, with mechanistic insight, is of pivotal significance. Recent studies linked aberrant FGFR signaling to CDKi resistance. However, detailed mechanisms are less clear. Based on control and FGFR1 overexpressing luminal A cell line models, we demonstrated that FGFR1 overexpression rendered the cells resistant to palbociclib. FGFR1 overexpression abolished palbociclib-mediated cell cycle arrest, as well as the attenuated palbociclib-induced inhibition of G1/S transition regulators (pRb, E2F1, and cyclin D3) and factors that promote G2/M transition (cyclin B1, cdc2/CDK1, and cdc25). Importantly, FGFR1-induced palbociclib resistance was associated with promotion of cancer cell stemness and the upregulation of Wnt/β-catenin signaling. We found that palbociclib may function as an ER agonist in MCF-7/FGFR1 cells. Upregulation of the ER-mediated transcription in MCF-7/FGFR1 cells was associated with ERα phosphorylation and enhanced receptor tyrosine kinase signaling. The combination of palbociclib with FGFR-targeting AZD4547 resulted in remarkable synergistic effects on MCF-7/FGFR1 cells, especially for the inhibition of cancer cell stemness. Our findings of FGFR1-induced palbociclib resistance, promotion of cancer stem cells and associated molecular changes advance our mechanistic understanding of CDKi resistance, which will facilitate the development of strategies targeting CDKi resistance in breast cancer treatment.

A novel stilbene derivative (GMQ3) suppressed proliferation and induced apoptosis in lung cancer via the p38-MAPK/SIRT1 pathway

BACKGROUND

Lung cancer is the primary cause of cancer-related mortality worldwide. The anticancer effect of stilbene has been noted in various tumor types. GMQ3, which has a stilbene-mimicking skeleton, is a novel small-molecule compound with promising antitumor activity. Our results revealed that GMQ3 not only suppressed cell proliferation and cell migration of lung cancer cells but also led to G1 phase cell cycle arrest and triggered caspase-dependent apoptosis. Furthermore, investigation of the molecular mechanism showed that GMQ3 could inhibited proliferation and induced apoptosis via the p38-MAPK/SIRT1 pathway both in vitro and in vivo. Xenograft tumor mouse models showed that GMQ3 significantly inhibited tumor growth in vivo without affecting body weight. Our findings indicated that GMQ3 exerts a strong anticancer action by suppressing cell proliferation, inhibiting cell migration and inducing cell apoptosis. Moreover, the efficacy of GMQ3 was enhanced in the presence of CDK4/6 inhibitor Abemaciclib. We conclude that GMQ3 is a promising agent with potential for lung cancer.

Mechanisms of abemaciclib, a CDK4/6 inhibitor, induced apoptotic cell death in prostate cancer cells in vitro

The therapeutic effects of abemaciclib (ABE), an inhibitor of cyclin- dependent kinases (CDK) 4/6, on the proliferation of two types of prostate cancer (PC) cells were revealed. In this study, in vitro cytotoxic and apoptotic effects of ABE on metastatic castration-resistant prostate cancer (mCRPC) androgen receptor (AR) negative PC-3 and AR mutant LNCaP PC cells were analyzed with WST-1, Annexin V, cell cycle, reactive oxygen species (ROS), mitochondrial membrane potential, RT-PCR, western blot, and apoptosis protein array. ABE considerably inhibited the growth of PC cells in a dose-dependent manner (p<0.01) and caused significant apoptotic cell death through the suppression of CDK4/6-Cyclin D complex, ROS generation and depolarization of mitochondria membrane potential. However, PC-3 cells were more sensitive to ABE than LNCaP cells. Furthermore, the expression levels of several pro-apoptotic and cell cycle regulatory proteins were upregulated by ABE in especially PC-3 cells with the downregulation of apoptotic inhibitor proteins. Our results suggest that ABE inhibits PC cell growth and promotes apoptosis and thus ABE treatment may be a promising treatment strategy in especially mCRPC. Further preclinical and clinical studies should be performed to clarify the clinical use of ABE for the treatment of PC.

Small-Molecule Anti-Cancer Drugs From 2016 to 2020: Synthesis and Clinical Application

Malignant tumors have become a significant public health problem that severely threatens human health. Drug-targeting therapy is essential for tumor therapy, along with surgery and radiotherapy. Of the 378 novel drugs approved over the past five years, those for oncological therapy remains at the top (25%). These drugs are used to treat patients with various cancers by acting on corresponding targets, such as EGFR, JAK, BTK, IDH, and FLT3. This review examines anti-tumor agents approved between 2016 and 2020, classifying them according to indication (such as lung cancer, leukemia, breast cancer, and myeloma). These drugs are reviewed according to their route of administration, first-in-class designation, approval dates, and expedited review categories. Furthermore, this paper summarizes the targets and modes of action of the approved anti-tumor drugs while systematically discussing their synthetic routes for medicinal chemistry or industrial use, which will benefit next-generation drug discovery.

Advances in endocrine and targeted therapy for hormone-receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer

Nearly 70% of breast cancer (BC) is hormone-receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, and endocrine therapy is the mainstay of treatment for this subtype. However, intrinsic or acquired endocrine resistance can occur during the endocrine treatment. Based on insights of endocrine resistance mechanisms, a number of targeted therapies have been and continue to be developed. With regard to HR-positive, HER2-negative advanced BC, aromatase inhibitor (AI) is superior to tamoxifen, and fulvestrant is a better option for patients previously exposed to endocrine therapy. Targeted drugs, such as cyclin-dependent kinases (CDK) 4/6 inhibitors, mammalian target of rapamycin (mTOR) inhibitors, phosphoinositide-3-kinase (PI3K) inhibitors, and histone deacetylase (HDAC) inhibitors, play a significant role in the present and show a promising future. With the application of CDK4/6 inhibitors becoming common, mechanisms of acquired resistance to them should also be taken into consideration.

Small Molecule CDK Inhibitors for the Therapeutic Management of Cancer

Cyclin-dependent kinases (CDKs) are a group of multifunctional enzymes consisting of catalytic and regulatory subunits. The regulatory subunit, cyclin, remains dissociated under normal circumstances, and complexation of cyclin with the catalytic subunit of CDK leads to its activation for phosphorylation of protein substrates. The primary role of CDKs is in the regulation of the cell cycle. Retinoblastoma protein (Rb) is one of the widely investigated tumor suppressor protein substrates of CDK, which prevents cells from entering into cell-cycle under normal conditions. Phosphorylation of Rb by CDKs causes its inactivation and ultimately allows cells to enter a new cell cycle. Many cancers are associated with hyperactivation of CDKs as a result of mutation of the CDK genes or CDK inhibitor genes. Therefore, CDK modulators are of great interest to explore as novel therapeutic agents against cancer and led to the discovery of several CDK inhibitors to clinics. This review focuses on the current progress and development of anti-cancer CDK inhibitors from preclinical to clinical and synthetic to natural small molecules.

Development of CDK4/6 Inhibitors: A Five Years Update

The inhibition of cyclin dependent kinases 4 and 6 plays a role in aromatase inhibitor resistant metastatic breast cancer. Three dual CDK4/6 inhibitors have been approved for the breast cancer treatment that, in combination with the endocrine therapy, dramatically improved the survival outcomes both in first and later line settings. The developments of the last five years in the search for new selective CDK4/6 inhibitors with increased selectivity, treatment efficacy, and reduced adverse effects are reviewed, considering the small-molecule inhibitors and proteolysis-targeting chimeras (PROTACs) approaches, mainly pointing at structure-activity relationships, selectivity against different kinases and antiproliferative activity.

Comparison of the Inhibitory Binding Modes Between the Planar Fascaplysin and Its Nonplanar Tetrahydro-β-carboline Analogs in CDK4

Fascaplysin is a natural marine product originating from sponges, attracting widespread attention due to its potential inhibitory activities against CDK4. However, its clinical application has been largely limited because of serious adverse effects caused by planar skeleton. To reduce the serious adverse effects, 18 tetrahydro-β-carboline analogs (compounds 6a-i and 7a-i) were designed and synthesized via breaking the planarity of fascaplysin, and the biological activities of the synthesized compounds were evaluated by MTT assay and CDK4/CycD3 enzyme inhibition assay. The title compounds showed varying degrees of inhibitory activities, especially the cytotoxicity of compound 6c against HeLa cells (IC₅₀ = 1.03 ± 0.19 μM) with quite weak cytotoxicity toward the normal cells WI-38 (IC₅₀ = 311.51 ± 56.06 μM), and the kinase inhibition test indicated that compound 6c was a potential CDK4 inhibitor. In order to further compare the action mechanisms of planar and nonplanar molecules on CDK4, the studied complexes of CDK4 bound with fascaplysin and three representative compounds (compound 6a-c) with bioactivities gradient were constructed by molecular docking and further verified through molecular dynamic simulation, which identified the key residues contributing to the ligands' binding. By comparing the binding modes of the constructed systems, it could be found that the residues contributing significantly to compound 6c's binding were highly consistent with those contributing significantly to fascaplysin's binding. Through the design, synthesis of the nonplanar fascaplysin derivatives, and binding mechanism analysis, some valuable hints for the discovery of antitumor drug candidates could be provided.

Longitudinal CTCs gene expression analysis on metastatic castration-resistant prostate cancer patients treated with docetaxel reveals new potential prognosis markers

CTCs have extensively been used for the monitoring and characterization of metastatic prostate cancer, but their application in the clinic is still very scarce. Besides, the resistance mechanisms linked to prostate cancer treatment remain unclear. Liquid biopsies represent the most promising alternative due to the complexity of biopsying bone metastasis and the duration of the disease. We performed a prospective longitudinal study in CTCs from 20 castration-resistant prostate cancer patients treated with docetaxel. For that, we used CellSearch® technology and a custom gene expression panel with qRT-PCR using a CTCs negative enrichment approach. We found that CTCs showed a hybrid phenotype during the disease, where epithelial features were associated with the presence of ≥ 5 CTCs/7.5 mL of blood, while high relative expression of the gene MYCL was observed preferentially in the set of samples with < 5 CTCs/7.5 mL of blood. At baseline, patients whose CTCs had stem or hybrid features showed a later progression. After 1 cycle of docetaxel, high relative expression of ZEB1 indicated worse outcome, while KRT19 and KLK3 high expression could predisposed the patients to a worse prognosis at clinical progression. In the present work we describe biomarkers with clinical relevance for the prediction of early response or resistance in castration-resistant prostate cancer patients. Besides, we question the utility of targeted isolated CTCs and the use of a limited number of markers to define the CTCs population.

Selective inhibition of CDK4/6: A safe and effective strategy for developing anticancer drugs

The sustained cell proliferation resulting from dysregulation of the cell cycle and activation of cyclin-dependent kinases (CDKs) is a hallmark of cancer. The inhibition of CDKs is a highly promising and attractive strategy for the development of anticancer drugs. In particular, third-generation CDK inhibitors can selectively inhibit CDK4/6 and regulate the cell cycle by suppressing the G1 to S phase transition, exhibiting a perfect balance between anticancer efficacy and general toxicity. To date, three selective CDK4/6 inhibitors have received approval from the U.S. Food and Drug Administration (FDA), and 15 CDK4/6 inhibitors are in clinical trials for the treatment of cancers. In this perspective, we discuss the crucial roles of CDK4/6 in regulating the cell cycle and cancer cells, analyze the rationale for selectively inhibiting CDK4/6 for cancer treatment, review the latest advances in highly selective CDK4/6 inhibitors with different chemical scaffolds, explain the mechanisms associated with CDK4/6 inhibitor resistance and describe solutions to overcome this issue, and briefly introduce proteolysis targeting chimera (PROTAC), a new and revolutionary technique used to degrade CDK4/6.

Prosigna® breast cancer assay: histopathologic correlation, development, and assessment of size, nodal status, Ki-67 (SiNK™) index for breast cancer prognosis

The Prosigna® assay is a United States Food and Drug Administration (US-FDA) cleared molecular test for prognostic use in hormone receptor-positive stage I/II breast cancer in postmenopausal women. We analyzed histopathologic features of 79 cases with Prosigna® assay results and found a significant correlation between tumor size, grade, and Ki-67 labeling index with Prosigna® score (0-40, 41-60, and 61-100) and Prosigna® risk categories. Since the Prosigna® risk stratification is influenced by lymph node status, we designed an index that included lymph node status and the two most correlated variables (size and Ki-67 labeling index). This was termed the size, nodal, and Ki-67 (SiNK™) index and is calculated as follows: (size in mm) + (pN × 10) + (Ki-67 labeling index). The SiNK™ index was divided into ≤40 and >40 to test its prognostic significance in a well-characterized dataset of 106 ER+/HER2-negative stage I-II invasive breast cancers treated with standard multi-modality therapy with long term follow-up (average 101 months follow-up). Patients with SiNK™ ≤40 showed significantly improved distant recurrence-free survival (96% distant recurrence-free survival in SiNK™ ≤40 compared to 81% in SiNK™ >40; log-rank test p value: 0.0027). SiNK™ provides strong prognostic information in ERo+/HER2-negative breast cancers. SiNK™ index is simple to calculate using data from routine pathology reports. This should be further evaluated in larger datasets.

The lingering mysteries of metastatic recurrence in breast cancer

Despite being the hallmark of cancer that is responsible for the highest number of deaths, very little is known about the biology of metastasis. Metastatic disease typically manifests after a protracted period of undetectable disease following surgery or systemic therapy, owing to relapse or recurrence. In the case of breast cancer, metastatic relapse can occur months to decades after initial diagnosis and treatment. In this review, we provide an overview of the known key factors that influence metastatic recurrence, with the goal of highlighting the critical unanswered questions that still need to be addressed to make a difference in the mortality of breast cancer patients.

Abemaciclib, a third CDK 4/6 inhibitor for the treatment of hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced or metastatic breast cancer

INTRODUCTION

The field of metastatic luminal breast cancer (hormone receptor positive, HER-2 negative) is dynamic and evolving, harboring some of the most significant therapeutic advances in medical oncology. Over the last decade, many pivotal trials showed excellent results with drastic improvements in survival as well as the quality of life of metastatic luminal breast cancer patients.

AREAS COVERED

The successful inhibition of the cyclinD/cyclin-dependent kinases 4 and 6 (CDK4/6)-retinoblastoma protein (RB) pathway with potent CDK4/6 inhibitors improved the outcome of advanced luminal breast cancers. Abemaciclib is the third CDK 4/6 inhibitor arriving to the market after palbociclib and ribociclib. Here, we describe the biology of the CDK4/6 pathway and summarize clinical data of previously published pivotal trials emphasizing the efficacy and toxicity of abemaciclib. The aim was to define its place in the current guidelines and to make a brief comparison with other available drugs of same class in the absence of cross trials comparison.

EXPERT OPINION

As there are no available biomarkers to predict response or resistance to abemaciclib, the promising overall survival data of MONARCH-2 could possibly impact the clinician's choice to optimize treatment for endocrine-resistant metastatic breast cancer.

Understanding PD-L1 Testing in Breast Cancer: A Practical Approach

Background

Immune checkpoint inhibitors (ICI) have changed therapy strategies for cancer patients tremendously. Some approved ICI acquire testing of PD-L1 expression on tumor and/or immune cells. However, since PD-L1 testing is a comprehensive issue with various assays, antibody clones, scoring methods, and cut-offs, we aimed to summarize the recommendations and technical and histopathological issues of diagnostic PD-L1 assessment with an emphasis on invasive breast cancer (IBC).

Summary

Besides other (pre)analytical considerations, selecting the most adequate PD-L1 immunohistochemical assay/antibody clone is important. In-house assay validation, prediagnostic training, and internal and external quality assurance should be implemented. The current most relevant PD-L1 assays and scores will be explained in this review. Moreover, recommendations for PD-L1 testing in IBC are outlined.

Key Messages

Atezolizumab plus nab-paclitaxel therapy is approved for adult patients with locally advanced or metastatic triple negative breast cancer (mTNBC), if the tumor-associated immune cells express PD-L1. - This PD-L1 immune cell positivity is defined as an immune cell (IC) score, which refers to the area occupied by PD-L1 positive immune cells (lymphocytes, dendritic cells, macrophages, and granulocytes) as a percentage of the whole tumor area. The cut-off is an IC score ≥1%. In the approval study for atezolizumab in mTNBC, IC score was assessed using the Ventana PD-L1 SP142 assay. Other assays or laboratory developed tests may be used depending on country-specific drug approvals. However, harmonization studies have to show whether other PD-L1 tests are reliable and of clinical value to predict the response of breast cancer patients to ICI.

Inhibition of DNA Repair Pathways and Induction of ROS Are Potential Mechanisms of Action of the Small Molecule Inhibitor BOLD-100 in Breast Cancer

BOLD-100, a ruthenium-based complex, sodium trans-[tetrachloridobis (1H-indazole) ruthenate (III)] (also known as IT-139, NKP1339 or KP1339), is a novel small molecule drug that demonstrated a manageable safety profile at the maximum tolerated dose and modest antitumor activity in a phase I clinical trial. BOLD-100 has been reported to inhibit the upregulation of the endoplasmic reticulum stress sensing protein GRP78. However, response to BOLD-100 varies in different cancer models and the precise mechanism of action in high-response versus low-response cancer cells remains unclear. In vitro studies have indicated that BOLD-100 induces cytostatic rather than cytotoxic effects as a monotherapy. To understand BOLD-100-mediated signaling mechanism in breast cancer cells, we used estrogen receptor positive (ER+) MCF7 breast cancer cells to obtain gene-metabolite integrated models. At 100 μM, BOLD-100 significantly reduced cell proliferation and expression of genes involved in the DNA repair pathway. BOLD-100 also induced reactive oxygen species (ROS) and phosphorylation of histone H2AX, gamma-H2AX (Ser139), suggesting disruption of proper DNA surveillance. In estrogen receptor negative (ER-) breast cancer cells, combination of BOLD-100 with a PARP inhibitor, olaparib, induced significant inhibition of cell growth and xenografts and increased gamma-H2AX. Thus, BOLD-100 is a novel DNA repair pathway targeting agent and can be used with other chemotherapies in ER- breast cancer.

CDK4/6 inhibitors: a novel strategy for tumor radiosensitization

Recently, the focus of enhancing tumor radiosensitivity has shifted from chemotherapeutics to targeted therapies. Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors are a novel class of selective cell cycle therapeutics that target the cyclin D-CDK4/6 complex and induce G1 phase arrest. These agents have demonstrated favorable effects when used as monotherapy or combined with endocrine therapy and targeted inhibitors, stimulating further explorations of other combination strategies. Multiple preclinical studies have indicated that CDK4/6 inhibitors exhibit a synergistic effect with radiotherapy both in vitro and in vivo. The principal mechanisms of radiosensitization effects include inhibition of DNA damage repair, enhancement of apoptosis, and blockade of cell cycle progression, which provide the rationale for clinical use. CDK4/6 inhibitors also induce cellular senescence and promote anti-tumor immunity, which might represent potential mechanisms for radiosensitization. Several small sample clinical studies have preliminarily indicated that the combination of CDK4/6 inhibitors and radiotherapy exhibited well-tolerated toxicity and promising efficacy. However, most clinical trials in combined therapy remain in the recruitment stage. Further work is required to seek optimal radiotherapy-drug combinations. In this review, we describe the effects and underlying mechanisms of CDK4/6 inhibitors as a radiosensitizer and discuss previous clinical studies to evaluate the prospects and challenges of this combination.

E2F8 Induces Cell Proliferation and Invasion through the Epithelial-Mesenchymal Transition and Notch Signaling Pathways in Ovarian Cancer

Background: Despite the recent research implicating E2F8 (E2F Transcription Factor 8) in cancer, the role of E2F8 in the progression of ovarian cancer has remained unclear. Hence, we explored the bio-functional effects of E2F8 knockdown on ovarian cancer cell lines in vitro and in vivo. Methods: The expression of E2F8 was compared between ovarian cancer and noncancer tissues, and its association with the progression-free survival of ovarian cancer patients was analyzed. To demonstrate the function of E2F8 in cell proliferation, migration, and invasion, we employed RNA interference to suppress E2F8 expression in ovarian cancer cell lines. Finally, the effect of E2F8 knockdown was investigated in a xenograft mouse model of ovarian cancer. Results: Ovarian cancer tissue exhibited significantly higher E2F8 expression compared to that of normal ovarian tissue. Clinical data showed that E2F8 was a significant predictor of progression-free survival. Moreover, the prognosis of the ovarian cancer patients with high E2F8 expression was poorer than that of the patients with low E2F8 expression. In vitro experiments using E2F8-knockdown ovarian cancer cell lines demonstrated that E2F8 knockdown inhibited cell proliferation, migration, and tumor invasion. Additionally, E2F8 was a potent inducer and modulator of the expression of epithelial–mesenchymal transition and Notch signaling pathway-related markers. We confirmed the function of E2F8 in vivo, signifying that E2F8 knockdown was significantly correlated with reduced tumor size and weight. Conclusions: Our findings indicate that E2F8 is highly correlated with ovarian cancer progression. Hence, E2F8 can be utilized as a prognostic marker and therapeutic target against ovarian malignancy.

Regulating tumor suppressor genes: post-translational modifications

Tumor suppressor genes cooperate with each other in tumors. Three important tumor suppressor proteins, retinoblastoma (Rb), p53, phosphatase, and tensin homolog deleted on chromosome ten (PTEN) are functionally associated and they regulated by post-translational modification (PTMs) as well. PTMs include phosphorylation, SUMOylation, acetylation, and other novel modifications becoming growing appreciated. Because most of PTMs are reversible, normal cells use them as a switch to control the state of cells being the resting or proliferating, and PTMs also involve in cell survival and cell cycle, which may lead to abnormal proliferation and tumorigenesis. Although a lot of studies focus on the importance of each kind of PTM, further discoveries shows that tumor suppressor genes (TSGs) form a complex “network” by the interaction of modification. Recently, there are several promising strategies for TSGs for they change more frequently than carcinogenic genes in cancers. We here review the necessity, characteristics, and mechanisms of each kind of post-translational modification on Rb, p53, PTEN, and its influence on the precise and selective function. We also discuss the current antitumoral therapies of Rb, p53 and PTEN as predictive, prognostic, and therapeutic target in cancer.

Cardiac arrhythmia considerations of hormone cancer therapies

Breast and prostate cancers are among the most prevalent cancers worldwide. Oestradiol and progesterone are major drivers for breast cancer proliferation, and androgens for prostate cancer. Endocrine therapies are drugs that interfere with hormone-activated pathways to slow cancer progression. Multiple new breakthrough drugs improving overall survival have recently been developed within this class. As the use of these latter drugs grows, incidence of cardiac arrhythmias has emerged as an unappreciated complication. These changes are not surprising given that sex hormones alter ventricular repolarization. Testosterone shortens action potential duration and QT interval duration, while oestradiol has an opposite effect. In patients with breast cancer, selective oestrogen receptor modulators are associated with more reports for long QT and torsade de pointes (TdP) than aromatase inhibitors, likely through an oestradiol-like effect on the heart. Cyclin-dependent kinase 4/6 inhibitors, a new class of anticancer drugs used in combination with endocrine therapies in hormone receptor positive breast cancer, are also variably associated with drug-induced long QT, particularly with ribociclib. In prostate cancer, androgen deprivation therapy is associated with long QT and TdP, and possibly atrial fibrillation for abiraterone. In this review, we have summarized the clinical and preclinical data focusing on cardiac arrhythmia considerations of hormone cancer therapies.

RABL6A Is an Essential Driver of MPNSTs that Negatively Regulates the RB1 Pathway and Sensitizes Tumor Cells to CDK4/6 Inhibitors

PURPOSE

Malignant peripheral nerve sheath tumors (MPNST) are deadly sarcomas that lack effective therapies. In most MPNSTs, the retinoblastoma (RB1) tumor suppressor is disabled by hyperactivation of cyclin-dependent kinases (CDK), commonly through loss of CDK-inhibitory proteins such as p27(Kip1). RABL6A is an inhibitor of RB1 whose role in MPNSTs is unknown. To gain insight into MPNST development and establish new treatment options, we investigated RABL6A-RB1 signaling and CDK inhibitor-based therapy in MPNSTs.

EXPERIMENTAL DESIGN

We examined patient-matched MPNSTs and precursor lesions by RNA sequencing (RNA-Seq) and IHC. Molecular and biological effects of silencing RABL6A and/or p27 in MPNST lines and normal human Schwann cells were determined. Tumor-suppressive effects of CDK inhibitors were measured in MPNST cells and orthotopic tumors.

RESULTS

RABL6A was dramatically upregulated in human MPNSTs compared with precursor lesions, which correlated inversely with p27 levels. Silencing RABL6A caused MPNST cell death and G₁ arrest that coincided with p27 upregulation, CDK downregulation, and RB1 activation. The growth-suppressive effects of RABL6A loss, and its regulation of RB1, were largely rescued by p27 depletion. Importantly, reactivation of RB1 using a CDK4/6 inhibitor (palbociclib) killed MPNST cells in vitro in an RABL6A-dependent manner and suppressed MPNST growth in vivo. Low-dose combination of drugs targeting multiple RB1 kinases (CDK4/6, CDK2) had enhanced antitumorigenic activity associated with potential MPNST cell redifferentiation.

CONCLUSIONS

RABL6A is a new driver of MPNST pathogenesis that acts in part through p27-RB1 inactivation. Our results suggest RB1 targeted therapy with multiple pathway drugs may effectively treat MPNSTs.

CDK4/RB/E2Fs axis as potential therapeutic target of endometrial cancer

The increasing incidence rate and decreasing patients' five-year survival rate for endometrial cancer (EC) in recent decades highlight the necessity for further investigation of the molecular characteristics involved in cancer initiation and progression. In this study, we found that the pathways associated with mitotic cell cycle were enriched in primary EC samples versus normal endometrial samples through analyzing RNA-seq data of The Cancer Genome Atlas (TCGA). The messenger RNA (mRNA) expression of three activator E2Fs (E2F1, E2F2, and E2F3) and their target genes increased significantly in EC samples. Additionally, the high transcriptional activity of activator E2Fs was associated with poor survival, advanced clinical stage, high histologic grade, and aggressive histological type. We further demonstrated that E2Fs hyperactivation correlated with DNA hypomethylation and high cyclin-dependent kinase 4 (CDK4) expression. Moreover, abemaciclib, a selective CDK4 inhibitor, significantly inhibited the proliferation rates of human EC cell lines in vitro. And, abemaciclib also obviously inhibited EC cell growth in nude mice model. Collectively, our data suggest that the misregulation of CDK4/RB/E2Fs axis is associated with EC oncogenesis, and abemaciclib is a potential targeted drug for EC.

Potent Cell-Cycle Inhibition and Upregulation of Immune Response with Abemaciclib and Anastrozole in neoMONARCH, Phase II Neoadjuvant Study in HR+/HER2- Breast Cancer

PURPOSE

neoMONARCH assessed the biological effects of abemaciclib in combination with anastrozole in the neoadjuvant setting.

PATIENTS AND METHODS

Postmenopausal women with stage I-IIIB HR⁺/HER2^- breast cancer were randomized to a 2-week lead-in of abemaciclib, anastrozole, or abemaciclib plus anastrozole followed by 14 weeks of the combination. The primary objective evaluated change in Ki67 from baseline to 2 weeks of treatment. Additional objectives included clinical, radiologic, and pathologic responses, safety, as well as gene expression changes related to cell proliferation and immune response.

RESULTS

Abemaciclib, alone or in combination with anastrozole, achieved a significant decrease in Ki67 expression and led to potent cell-cycle arrest after 2 weeks of treatment compared with anastrozole alone. More patients in the abemaciclib-containing arms versus anastrozole alone achieved complete cell-cycle arrest (58%/68% vs. 14%, P < 0.001). At the end of treatment, following 2 weeks lead-in and 14 weeks of combination therapy, 46% of intent-to-treat patients achieved a radiologic response, with pathologic complete response observed in 4%. The most common all-grade adverse events were diarrhea (62%), constipation (44%), and nausea (42%). Abemaciclib, anastrozole, and the combination inhibited cell-cycle processes and estrogen signaling; however, combination therapy resulted in increased cytokine signaling and adaptive immune response indicative of enhanced antigen presentation and activated T-cell phenotypes.

CONCLUSIONS

Abemaciclib plus anastrozole demonstrated biological and clinical activity with generally manageable toxicities in patients with HR⁺/HER2^- early breast cancer. Abemaciclib led to potent cell-cycle arrest, and in combination with anastrozole, enhanced immune activation.

Comparison of the roles of estrogens and androgens in breast cancer and prostate cancer

Breast cancer (BC) and prostate cancer (PC) are the second most common malignant tumors in women and men in western countries, respectively. The risks of death are 14% for BC and 9% for PC. Abnormal estrogen and androgen levels are related to carcinogenesis of the breast and prostate. Estradiol stimulates cancer development in BC. The effect of estrogen on PC is concentration-dependent, and estrogen can regulate androgen production, further affecting PC. Estrogen can also increase the risk of androgen-induced PC. Androgen has dual effects on BC via different metabolic pathways, and the role of the androgen receptor (AR) in BC also depends on cell subtype and downstream target genes. Androgen and AR can stimulate both primary PC and castration-resistant PC. Understanding the mechanisms of the effects of estrogen and androgen on BC and PC may help us to improve curative BC and PC treatment strategies.

Inhibition of UBE2N-dependent CDK6 protein degradation by miR-934 promotes human bladder cancer cell growth

Because bladder cancer (BC) is one of the most common malignant cancers of the urinary system, identification of BC cell growth-associated effectors is of great significance. Cyclin-dependent kinase (CDK)6 is a member of the CDK family of cell cycle-related proteins and plays an important role in cancer cell growth. This is borne out by the fact that a CDK6 inhibitor had been approved to treat several types of cancers. Nevertheless, underlying molecular mechanisms concerning how to regulate CDK6 expression in BC remains unclear. In the present study, it was observed that miR-934 was much higher in human BCs and human BC cell lines as well. The results also revealed that miR-934 inhibition dramatically decreased human BC cell monolayer growth in vitro and xenograft tumor growth in vivo; the outcomes were accompanied by CDK6 protein down-regulation and G₀-G₁ cell cycle arrest. Moreover, overexpression of CDK6 reversed the inhibition of BC cell growth induced by miR-934. Further studies showed that miR-934 binds to a 3'-UTR of ubiquitin-conjugating enzyme 2N (ube2n) mRNA, down-regulated UBE2N protein expression; this, in turn, attenuated CDK6 protein degradation and led to CDK6 protein accumulation as well as the promotion of BC tumor growth. Collectively, this study not only establishes a novel regulatory axis of miR-934/UBE2N of CDK6 but also provides data suggesting that miR-934 and UBE2N may be potentially promising targets for therapeutic strategies against BC.-Yan, H., Ren, S., Lin, Q., Yu, Y., Chen, C., Hua, X., Jin, H., Lu, Y., Zhang, H., Xie, Q., Huang, C., Huang, H. Inhibition of UBE2N-dependent CDK6 protein degradation by miR-934 promotes human bladder cancer cell growth.

The broken cycle: E2F dysfunction in cancer

The cyclin-dependent kinase (CDK)-RB-E2F axis forms the core transcriptional machinery driving cell cycle progression, dictating the timing and fidelity of genome replication and ensuring genetic material is accurately passed through each cell division cycle. The ultimate effectors of this axis are members of a family of eight distinct E2F genes encoding transcriptional activators and repressors. E2F transcriptional activity is tightly regulated throughout the cell cycle via transcriptional and translational regulation, post-translational modifications, protein degradation, binding to cofactors and subcellular localization. Alterations in one or more key components of this axis (CDKs, cyclins, CDK inhibitors and the RB family of proteins) occur in virtually all cancers and result in heightened oncogenic E2F activity, leading to uncontrolled proliferation. In this Review, we discuss the activities of E2F proteins with an emphasis on the newest atypical E2F family members, the specific and redundant functions of E2F proteins, how misexpression of E2F transcriptional targets promotes cancer and both current and developing therapeutic strategies being used to target this oncogenic pathway.

Allosteric Small-Molecule Serine/Threonine Kinase Inhibitors

Deregulation of protein kinase activity has been linked to many diseases ranging from cancer to AIDS and neurodegenerative diseases. Not surprisingly, drugging the human kinome - the complete set of kinases encoded by the human genome - has been one of the major drug discovery pipelines. Majority of the approved clinical kinase inhibitors target the ATP binding site of kinases. However, the remarkable sequence and structural similarity of ATP binding pockets of kinases make selective inhibition of kinases a daunting task. To circumvent these issues, allosteric inhibitors that target sites other than the orthosteric ATP binding pocket have been developed. The structural diversity of the allosteric sites allows these inhibitors to have higher selectivity, lower toxicity and improved physiochemical properties and overcome drug resistance associated with the use of conventional kinase inhibitors. In this chapter, we will focus on the allosteric inhibitors of selected serine/threonine kinases, outline the benefits of using these inhibitors and discuss the challenges and future opportunities.

Peptides/Proteins Encoded by Non-coding RNA: A Novel Resource Bank for Drug Targets and Biomarkers

Non-coding RNAs (ncRNAs) are defined as RNA molecules that do not encode proteins, but recent evidence has proven that peptides/proteins encoded by ncRNAs do indeed exist and usually contain less than 100 amino acids. These peptides/proteins play an important role in regulating tumor energy metabolism, epithelial to mesenchymal transition of cancer cells, the stability of the c-Myc oncoprotein, and the ubiquitination and degradation of proliferating cell nuclear antigen (PCNA). These peptides/proteins represent promising drug targets for fighting against tumor growth or biomarkers for predicting the prognosis of cancer patients. In this review, we summarize the characteristics of peptides/proteins that have recently been identified as putative ncRNA translation products and their outlook for small molecule peptide drugs, drug targets, and biomarkers.

Inhibitors targeting CDK4/6, PARP and PI3K in breast cancer: a review

Breast cancer is the global leading cause of cancer-related death in women and it represents a major health burden worldwide. One of the promising breast cancer therapeutic avenues is through small molecule inhibitors (SMIs) which have undergone rapid progress with successful clinical trials. Recently, three emerging and vital groups of proteins are targeted by SMIs for breast cancer treatment, namely cyclin-dependent kinase 4 and 6 (CDK4/6), poly (adenosine diphosphate-ribose) polymerase (PARP) and phosphoinositide 3-kinase (PI3K). Several of these inhibitors have been approved for the treatment of breast cancer patients or progressed into late-stage clinical trials. Thus, modeling from these successful clinical trials, as well as their limitations, is pivotal for future development and trials of other inhibitors or therapeutic regimens targeting breast cancer patients. In this review, we discuss eight recently approved or novel SMIs against CDK4/6 (palbociclib, ribociclib and abemaciclib), PARP (olaparib, veliparib and talazoparib), and PI3K (buparlisib and alpelisib). The mechanisms of action, series of clinical trials and limitations are described for each inhibitor.

A systematic review and meta-analysis of prognostic biomarkers in resectable esophageal adenocarcinomas

Targeted therapy is lagging behind in esophageal adenocarcinoma (EAC). To guide the development of new treatment strategies, we provide an overview of the prognostic biomarkers in resectable EAC treated with curative intent. The Medline, Cochrane and EMBASE databases were systematically searched, focusing on overall survival (OS). The quality of the studies was assessed using a scoring system ranging from 0-7 points based on modified REMARK criteria. To evaluate all identified prognostic biomarkers, the hallmarks of cancer were adapted to fit all biomarkers based on their biological function in EAC, resulting in the features angiogenesis, cell adhesion and extra-cellular matrix remodeling, cell cycle, immune, invasion and metastasis, proliferation, and self-renewal. Pooled hazard ratios (HR) and 95% confidence intervals (CI) were derived by random effects meta-analyses performed on each hallmarks of cancer feature. Of the 3298 unique articles identified, 84 were included, with a mean quality of 5.9 points (range 3.5-7). The hallmarks of cancer feature 'immune' was most significantly associated with worse OS (HR 1.88, (95%CI 1.20-2.93)). Of the 82 unique prognostic biomarkers identified, meta-analyses showed prominent biomarkers, including COX-2, PAK-1, p14ARF, PD-L1, MET, LC3B, IGFBP7 and LGR5, associated to each hallmark of cancer.

An insight into the emerging role of cyclin-dependent kinase inhibitors as potential therapeutic agents for the treatment of advanced cancers

Cancer denotes a pathological manifestation that is characterized by hyperproliferation of cells. It has anticipated that a better understanding of disease pathogenesis and the role of cell-cycle regulators may provide an opportunity to develop an effective cancer therapeutic agents. Specifically, the cyclin-dependent kinases (CDKs) which regulate the transition of cell-cycle through different phases; have been identified as fundamental targets for therapeutic advances. It is an evident from experimental studies that several events leading to tumor growth occur by exacerbation of CDK4/CDK6 in G1-phase of cell division cycle. Additionally, the characteristics of S- and G2/M-phase regulated by CDK1/CDK2 are pivotal events that may lead to abrupt the cell division. Although, previously reported CDK inhibitors have shown remarkable results in pre-clinical studies, but have not yielded appreciable clinical results yet. Therefore, the development of clinically potent CDK inhibitors has remained to be a challenging task. However, continuous efforts has led to the development of some novel CDKs inhibitors that have emerged as a potent strategy for the treatment of advanced cancers. In this article, we have summarized the role of CDKs in cell-cycle regulation and tumorigenesis and recent advances in the development of CDKs inhibitors as a promising therapy for the treatment of advanced cancer. In addition, we have also performed a comparison of crystallographic studies to get valuable insight into the interaction mode differences of inhibitors, binding to CDK isoforms with apparently similar binding sites. The knowledge of ligand-specific recognition towards a particular CDK isoform may be applied as a key tool in future for the designing of isoform-specific inhibitors.