Preclinical evaluation of cyclin dependent kinase 11 and casein kinase 2 survival kinases as RNA interference targets for triple negative breast cancer therapy

CK2α-mediated phosphorylation of GRP94 facilitates the metastatic cascade in triple-negative breast cancer

Distant metastasis is a significant hallmark affecting to the high death rate of patients with triple-negative breast cancer (TNBC). Thus, it is crucial to identify and develop new therapeutic strategies to hinder cancer metastasis. While emerging studies have hinted a pivotal role of glucose-regulated protein 94 (GRP94) in tumorigenesis, the exact biological functions and molecular mechanisms of GRP94 in modulating cancer metastasis remain to be elucidated. Our study demonstrated an increased expression of GRP94 in TNBC correlated with metastatic progression and unfavorable prognosis in patients. Functionally, we identified that GRP94 depletion significantly diminished TNBC tumorigenesis and subsequent lung metastasis. In contrast, GRP94 overexpression exacerbated the invasiveness, migration, and lung metastasis of non-TNBC cells. Mechanistically, we found that casein kinase 2 alpha (CK2α) active in advanced breast cancer phosphorylated GRP94 at a conserved serine 306 (S306) residue. This phosphorylation increased the stability of GRP94 and enhanced its interaction with LRP6, leading to activation of canonical Wnt signaling. From a therapeutic standpoint, we found that benzamidine, a novel CK2α inhibitor, effectively suppressed GRP94 phosphorylation, LRP6 stabilization, and metastasis of TNBC. Our results point to the critical role of CK2α-mediated GRP94 phosphorylation in TNBC metastasis through activation of Wnt signaling, highlighting GRP94 as a therapeutic target to impede TNBC metastasis.

lncSNHG3 drives breast cancer progression by epigenetically increasing CSNK2A1 expression level

Mounting evidence demonstrates that long noncoding RNAs (lncRNAs) have critical roles in the initiation and progression of cancer. Here, we report that small nucleolar RNA host gene 3 (SNHG3) is a key regulator of breast cancer progression. We analyzed RNA sequencing data to explore abnormally expressed lncRNAs in breast cancer. The effects of SNHG3 on breast cancer were investigated via in vitro and in vivo assays (CCK-8 assay, colony formation assay, flow cytometry assay, EdU assay, xenograft model, immunohistochemistry, and Western blot). The mechanism of SNHG3 action was explored through bioinformatics, RNA fluorescence in situ hybridization, luciferase reporter assay, RNA pull-down assay, chromatin immunoprecipitation assay and RNA immunoprecipitation assay. We found that SNHG3 expression was upregulated in breast cancer tissues and that its high expression level was associated with poor survival. We also found that high SNHG3 expression was partly induced by STAT3. Moreover, SNHG3 knockdown significantly repressed breast cancer cell growth both in vitro and in vivo. In the cytoplasm, SNHG3 facilitated the expression of Casein kinase II-A1 (CSNK2A1) by absorbing miR-485-5p and recruiting the HuR protein, participating in the malignant progression of breast cancer. Taken together, our study reveals a SNHG3-based regulatory network, which plays an oncogenic role in breast cancer and suggests that SNHG3 may serve as a potential target for the diagnosis and treatment of breast cancer.

Targeting pre-mRNA splicing in cancers: roles, inhibitors, and therapeutic opportunities

Accumulating evidence has indicated that pre-mRNA splicing plays critical roles in a variety of physiological processes, including development of multiple diseases. In particular, alternative splicing is profoundly involved in cancer progression through abnormal expression or mutation of splicing factors. Small-molecule splicing modulators have recently attracted considerable attention as a novel class of cancer therapeutics, and several splicing modulators are currently being developed for the treatment of patients with various cancers and are in the clinical trial stage. Novel molecular mechanisms modulating alternative splicing have proven to be effective for treating cancer cells resistant to conventional anticancer drugs. Furthermore, molecular mechanism-based combination strategies and patient stratification strategies for cancer treatment targeting pre-mRNA splicing must be considered for cancer therapy in the future. This review summarizes recent progress in the relationship between druggable splicing-related molecules and cancer, highlights small-molecule splicing modulators, and discusses future perspectives of splicing modulation for personalized and combination therapies in cancer treatment.

Biomarkers discovery for endometrial cancer: A graph convolutional sample network method

BACKGROUND

Endometrial carcinoma is the sixth most common cancer in women worldwide. Importantly, endometrial cancer is among the few types of cancers with patient mortality that is still increasing, which indicates that the improvement in its diagnosis and treatment is still urgent. Moreover, biomarker discovery is essential for precise classification and prognostic prediction of endometrial cancer.

METHODS

A novel graph convolutional sample network method was used to identify and validate biomarkers for the classification of endometrial cancer. The sample networks were first constructed for each sample, and the gene pairs with high frequencies were identified to construct a subtype-specific network. Putative biomarkers were then screened using the highest degrees in the subtype-specific network. Finally, simplified sample networks are constructed using the biomarkers for the graph convolutional network (GCN) training and prediction.

RESULTS

Putative biomarkers (23) were identified using the novel bioinformatics model. These biomarkers were then rationalised with functional analyses and were found to be correlated to disease survival with network entropy characterisation. These biomarkers will be helpful in future investigations of the molecular mechanisms and therapeutic targets of endometrial cancers.

CONCLUSIONS

A novel bioinformatics model combining sample network construction with GCN modelling is proposed and validated for biomarker discovery in endometrial cancer. The model can be generalized and applied to biomarker discovery in other complex diseases.

Protein kinase CK2 – diverse roles in cancer cell biology and therapeutic promise

The association of protein kinase CK2 (formerly casein kinase II or 2) with cell growth and proliferation in cells was apparent at early stages of its investigation. A cancer-specific role for CK2 remained unclear until it was determined that CK2 was also a potent suppressor of cell death (apoptosis); the latter characteristic differentiated its function in normal versus malignant cells because dysregulation of both cell growth and cell death is a universal feature of cancer cells. Over time, it became evident that CK2 exerts its influence on a diverse range of cell functions in normal as well as in transformed cells. As such, CK2 and its substrates are localized in various compartments of the cell. The dysregulation of CK2 is documented in a wide range of malignancies; notably, by increased CK2 protein and activity levels with relatively moderate change in its RNA abundance. High levels of CK2 are associated with poor prognosis in multiple cancer types, and CK2 is a target for active research and testing for cancer therapy. Aspects of CK2 cellular roles and targeting in cancer are discussed in the present review, with focus on nuclear and mitochondrial functions and prostate, breast and head and neck malignancies.

The Role of CDK Pathway Dysregulation and Its Therapeutic Potential in Soft Tissue Sarcoma

Soft tissue sarcomas (STSs) are tumors that are challenging to treat due to their pathologic and molecular heterogeneity and their tumor biology that is not yet fully understood. Recent research indicates that dysregulation of cyclin-dependent kinase (CDK) signaling pathways can be a strong driver of sarcogenesis. CDKs are enzyme forms that play a crucial role in cell-cycle control and transcription. They belong to the protein kinases group and to the serine/threonine kinases subgroup. Recently identified CDK/cyclin complexes and established CDK/cyclin complexes that regulate the cell cycle are involved in the regulation of gene expression through phosphorylation of critical components of transcription and pre-mRNA processing mechanisms. The current and continually growing body of data shows that CDKs play a decisive role in tumor development and are involved in the proliferation and growth of sarcoma cells. Since the abnormal expression or activation of large numbers of CDKs is considered to be characteristic of cancer development and progression, dysregulation of the CDK signaling pathways occurs in many subtypes of STSs. This review discusses how reversal and regulation can be achieved with new therapeutics and summarizes the current evidence from studies regarding CDK modulation for STS treatment.

Synthesis and Structure-Activity relationships of cyclin-dependent kinase 11 inhibitors based on a diaminothiazole scaffold

Cyclin-dependent kinases (CDK) are attractive targets for drug discovery due to their wide range of cellular functions. CDK11 is an understudied CDK with roles in transcription and splicing, cell cycle regulation, neuronal function, and apoptosis. In this study, we describe a medicinal chemistry campaign to identify a CDK11 inhibitor. Employing a promising but nonselective CDK11-targeting scaffold (JWD-047), extensive structure-guided medicinal chemistry modifications led to the identification of ZNL-05-044. A combination of biochemical evaluations and NanoBRET cellular assays for target engagement guided the SAR towards a 2,4-diaminothiazoles CDK11 probe with significantly improved kinome-wide selectivity over JWD-047. CDK11 inhibition with ZNL-05-044 leads to G2/M cell cycle arrest, consistent with prior work evaluating OTS964, and impacts CDK11-dependent mRNA splicing in cells. Together, ZNL-05-044 serves as a tool compound for further optimization and interrogation of the consequences of CDK11 inhibition.

Identification of key tumor stroma-associated transcriptional signatures correlated with survival prognosis and tumor progression in breast cancer

BACKGROUND

The aberrant expression of stromal gene signatures in breast cancer has been widely studied. However, the association of stromal gene signatures with tumor immunity, progression, and clinical outcomes remains lacking.

METHODS

Based on eight breast tumor stroma (BTS) transcriptomics datasets, we identified differentially expressed genes (DEGs) between BTS and normal breast stroma. Based on the DEGs, we identified dysregulated pathways and prognostic hub genes, hub oncogenes, hub protein kinases, and other key marker genes associated with breast cancer. Moreover, we compared the enrichment levels of stromal and immune signatures between breast cancer patients with bad and good clinical outcomes. We also investigated the association between tumor stroma-related genes and breast cancer progression.

RESULTS

The DEGs included 782 upregulated and 276 downregulated genes in BTS versus normal breast stroma. The pathways significantly associated with the DEGs included cytokine-cytokine receptor interaction, chemokine signaling, T cell receptor signaling, cell adhesion molecules, focal adhesion, and extracellular matrix-receptor interaction. Protein-protein interaction network analysis identified the stromal hub genes with prognostic value in breast cancer, including two oncogenes (COL1A1 and IL21R), two protein kinases encoding genes (PRKACA and CSK), and a growth factor encoding gene (PLAU). Moreover, we observed that the patients with bad clinical outcomes were less enriched in stromal and antitumor immune signatures (CD8 + T cells and tumor-infiltrating lymphocytes) but more enriched in tumor cells and immunosuppressive signatures (MDSCs and CD4 + regulatory T cells) compared with the patients with good clinical outcomes. The ratios of CD8 + /CD4 + regulatory T cells were lower in the patients with bad clinical outcomes. Furthermore, we identified the tumor stroma-related genes, including MCM4, SPECC1, IMPA2, and AGO2, which were gradually upregulated through grade I, II, and III breast cancers. In contrast, COL14A1, ESR1, SLIT2, IGF1, CH25H, PRR5L, ABCA6, CEP126, IGDCC4, LHFP, MFAP3, PCSK5, RAB37, RBMS3, SETBP1, and TSPAN11 were gradually downregulated through grade I, II, and III breast cancers. It suggests that the expression of these stromal genes has an association with the progression of breast cancers. These progression-associated genes also displayed an expression association with recurrence-free survival in breast cancer patients.

CONCLUSIONS

This study identified tumor stroma-associated biomarkers correlated with deregulated pathways, tumor immunity, tumor progression, and clinical outcomes in breast cancer. Our findings provide new insights into the pathogenesis of breast cancer.

Targeting CK2 in cancer: a valuable strategy or a waste of time?

CK2 is a protein kinase involved in several human diseases (ranging from neurological and cardiovascular diseases to autoimmune disorders, diabetes, and infections, including COVID-19), but its best-known implications are in cancer, where it is considered a pharmacological target. Several CK2 inhibitors are available and clinical trials are underway in different cancer types. Recently, the suitability of CK2 as a broad anticancer target has been questioned by the finding that a newly developed compound, named SGC-CK2-1, which is more selective than any other known CK2 inhibitor, is poorly effective in reducing cell growth in different cancer lines, prompting the conclusion that the anticancer efficacy of CX-4945, the commonly used clinical-grade CK2 inhibitor, is to be attributed to its off-target effects. Here we perform a detailed scrutiny of published studies on CK2 targeting and a more in-depth analysis of the available data on SGC-CK2-1 vs. CX-4945 efficacy, providing a different perspective about the actual reliance of cancer cells on CK2. Collectively taken, our arguments would indicate that the pretended dispensability of CK2 in cancer is far from having been proved and warn against premature conclusions, which could discourage ongoing investigations on a potentially valuable drug target.

Genetic variations of DNA bindings of FOXA1 and co-factors in breast cancer susceptibility

Identifying transcription factors (TFs) whose DNA bindings are altered by genetic variants that regulate susceptibility genes is imperative to understand transcriptional dysregulation in disease etiology. Here, we develop a statistical framework to analyze extensive ChIP-seq and GWAS data and identify 22 breast cancer risk-associated TFs. We find that, by analyzing genetic variations of TF-DNA bindings, the interaction of FOXA1 with co-factors such as ESR1 and E2F1, and the interaction of TFs with chromatin features (i.e., enhancers) play a key role in breast cancer susceptibility. Using genetic variants occupied by the 22 TFs, transcriptome-wide association analyses identify 52 previously unreported breast cancer susceptibility genes, including seven with evidence of essentiality from functional screens in breast relevant cell lines. We show that FOXA1 and co-factors form a core TF-transcriptional network regulating the susceptibility genes. Our findings provide additional insights into genetic variations of TF-DNA bindings (particularly for FOXA1) underlying breast cancer susceptibility.

The identification of transcription factors (TFs) whose binding sites are affected by risk genetic variants remains crucial. Here, the authors develop a statistical framework to analyse ChIP-seq and GWAS data, identify 22 breast cancer risk-associated TFs and a core TF-transcriptional network for FOXA1 and co-factors.

Triple negative breast cancer and non-small cell lung cancer: Clinical challenges and nano-formulation approaches

Triple negative breast cancer (TNBC) and non-small cell lung cancer (NSCLC) are amongst the most aggressive forms of solid tumors. TNBC is highlighted by absence of genetic components of progesterone receptor, HER2/neu and estrogen receptor in breast cancer. NSCLC is characterized by integration of malignant carcinoma into respiratory system. Both cancers are associated with poor median and overall survival rates with low progression free survival with high incidences of relapse. These cancers are characterized by tumor heterogeneity, genetic mutations, generation of cancer-stem cells, immune-resistance and chemoresistance. Further, these neoplasms have been reported for tumor cross-talk into second primary cancers for each other. Current chemotherapeutic regimens include usage of multiple agents in tandem to affect tumor cells through multiple mechanisms with various such combinations being clinically tested. However, lack of controlled delivery and effective temporospatial presence of chemotherapeutics has resulted in suboptimal therapeutic response. Consequently, passive targeted albumin bound paclitaxel and PEGylated liposomal doxorubicin have been clinically used and tested with newer drugs for improved therapeutic efficacy in these cancers. Active targeting of nanocarriers against surface overexpressed proteins in both neoplasms have been explored. However, use of single agent nanoparticulate formulations against both cancers have failed to elicit desired outcomes. This review aims to identify clinical unmet need in these cancers while establishing a correlation with tested nano-formulation approaches and issues with preclinical to clinical translation. Lipid and polymer-based drug-drug and drug-gene combinatorial nanocarriers delivering multiple chemotherapeutics simultaneously to desired site of action have been detailed. Finally, emerging opportunities such as pharmacological targets (immune check point and epigentic modulators) as well as gene-based modulation (siRNA/CRISPR/Cas9) and the nano-formulation challenges for effective treatment of both cancers have been explored.

CX-4945 and siRNA-Mediated Knockdown of CK2 Improves Cisplatin Response in HPV(+) and HPV(-) HNSCC Cell Lines

Head and neck squamous cell carcinoma (HNSCC) can be categorized into human papillomavirus (HPV) positive or negative disease. Elevated protein kinase CK2 level and activity have been historically observed in HNSCC cells. Previous studies on CK2 in HNSCC did not generally include consideration of HPV(+) and HPV(−) status. Here, we investigated the response of HPV(+) and HPV(−) HNSCC cells to CK2 targeting using CX-4945 or siRNA downregulation combined with cisplatin treatment. HNSCC cell lines were examined for CK2 expression levels and activity and response to CX-4945, with and without cisplatin. CK2 levels and NFκB p65-related activity were high in HPV(+) HNSCC cells relative to HPV(−) HNSCC cells. Treatment with CX-4945 decreased viability and cisplatin IC50 in all cell lines. Targeting of CK2 increased tumor suppressor protein levels for p21 and PDCD4 in most instances. Further study is needed to understand the role of CK2 in HPV(+) and HPV(−) HNSCC and to determine how incorporation of the CK2-targeted inhibitor CX-4945 could improve cisplatin response in HNSCC.

Bioinformatics identification of CCL8/21 as potential prognostic biomarkers in breast cancer microenvironment

BACKGROUND

Breast cancer (BC) is the most common malignancy among females worldwide. The tumor microenvironment usually prevents effective lymphocyte activation and infiltration, and suppresses infiltrating effector cells, leading to a failure of the host to reject the tumor. CC chemokines play a significant role in inflammation and infection.

METHODS

In our study, we analyzed the expression and survival data of CC chemokines in patients with BC using several bioinformatics analyses tools.

RESULTS

The mRNA expression of CCL2/3/4/5/7/8/11/17/19/20/22 was remarkably increased while CCL14/21/23/28 was significantly down-regulated in BC tissues compared with normal tissues. Methylation could down-regulate expression of CCL2/5/15/17/19/20/22/23/24/25/26/27 in BC. Low expression of CCL3/4/23 was found to be associated with drug resistance in BC. Results from Kaplan-Meier plotter and BC Gene-Expression Miner v4.2 (bcGenExMiner) v4.2 demonstrated that BC patients with high CCL8 and low CCL19/21/22 expression were more likely to have a worse prognosis. CCL8 expression was significantly up-regulated in BC tissues compared with normal tissues. High CCL8 expression was significantly correlated with negative PR, negative ER, positive nodal status, triple-negative BC subtype, basal-like BC subtype, triple-negative and basal-like BC subtype and high grades. CCL21 was down-regulated in BC, while high levels of CCL21 was associated with negative PR, triple-negative subtype, basal-like subtype and low tumor grade. Functional analysis demonstrated that CCL8 and CCL21 were involved in carcinogenesis, tumor immune escape and chemoresistance in BC.

CONCLUSION

Integrative bioinformatics analysis demonstrated CCL8/21 as potential prognostic biomarkers in BC microenvironment.

Evaluation of the Anticancer Activity of pH-Sensitive Polyketal Nanoparticles for Acute Myeloid Leukemia

Polyketals are a class of acid-responsive polymers that have been relatively less explored for drug delivery applications compared to polyesters. The degradation of these polymers is accelerated in an acidic medium and does not result in acidic byproducts. Their biocompatibility depends on the diol used for the synthesis. The present work aims to synthesize, characterize, and fabricate nanospheres of an aliphatic polyketal for delivery of the nucleotide analogue cytarabine toward the treatment of acute myeloid leukemia (AML). The internalization mechanism of the nanospheres was probed, and its implication on the nuclear localization and escape from the endo-lysosomal compartments were studied. The drug-loaded polyketal nanoparticles reduced the cell viability to a greater extent compared with the free drug. The effect of the drug-loaded polyketal nanoparticles on the differential gene expression of leukemic cells was investigated for the first time to understand their therapeutic implications. It was found that treatment with drug-loaded polyketal nanoparticles downregulated AML-specific genes involved in cell proliferation and recurrence compared to the free drug. The protein expression studies were performed for selected genes obtained from gene expression analysis. Biodistribution studies showed that the poly(cyclohexane-1,4-diyl acetone dimethylene ketal) (PCADK) nanoparticles exhibit prolonged circulation time. Overall, our results suggest that polyketal-based delivery of cytarabine represents a more effective alternative strategy for AML therapy.

Expression and prognostic value of transcription-associated cyclin-dependent kinases in human breast cancer

The expression and prognostic significance of transcription-associated cyclin-dependent kinases (TA-CDKs) in breast cancer have not been systematically investigated. Using Oncomine, GEPIA2, the Human Protein Atlas, the Kaplan-Meier Plotter, cBioPortal, Metascape, and DAVID 6.8, we profiled the expression of TA-CDKs in breast cancer, inferred their biological functions, and assessed their effect on prognosis. The expression of CDK7/10/13/19 mRNAs in breast cancer tissues was significantly higher than in normal breast tissues. Survival analysis of breast cancer patients revealed that increased CDK8 expression was associated with inferior overall survival (OS), higher expression of CDK7 or CDK8 was associated with inferior relapse-free survival (RFS), but higher expression of CDK13 was associated with favorable RFS and OS. In addition, a high genetic alteration rate (56%) in TA-CDKs was associated with shorter OS. On functional enrichment analysis, top GO enrichment items for TA-CDKs and their neighboring genes included cyclin-dependent protein serine/threonine kinase activity and transferase complex. The top KEGG pathways included cell cycle and mismatch repair. These results suggest that CDK7/8/13 are potential prognostic biomarkers for breast cancer patients and provide novel insight for future studies examining their usefulness as therapeutic targets.

A bird's eye view of the advanced approaches and strategies for overshadowing triple negative breast cancer

Triple negative breast cancer (TNBC) is one of the most aggressive form of breast cancer. It is characterized by the absence of estrogen, progesterone and human epidermal growth factor receptors. The main issue with TNBC is that it exhibits poor prognosis, high risk of relapse, short progression-free survival and low overall survival in patients. This is because the conventional therapy used for managing TNBC has issues pertaining to poor bioavailability, lower cellular uptake, increased off-target effects and development of resistance. To overcome such pitfalls, several other approaches are explored. In this context, the present manuscript showcases three of the most widely used approaches which are (i) nanotechnology-based approach; (ii) gene therapy approach and (iii) Phytochemical-based approach. The ultimate focus is to present and explain the insightful reports based on these approaches. Further, the review also expounds on the identified molecular targets and novel targeting ligands which are explored for managing TNBC effectively. Thus, in a nutshell, the review tries to highlight these existing treatment approaches which might inspire for future development of novel therapies with a potential of overshadowing TNBC.

Mechanisms of Resistance to Chemotherapy in Breast Cancer and Possible Targets in Drug Delivery Systems

Breast cancer (BC) is one of the most important cancers worldwide, and usually, chemotherapy can be used in an integrative approach. Usually, chemotherapy treatment is performed in association with surgery, radiation or hormone therapy, providing an increased outcome to patients. However, tumors can develop resistance to different drugs, progressing for a more aggressive phenotype. In this scenario, the use of nanocarriers could help to defeat tumor cell resistance, providing a new therapeutic perspective for patients. Thus, this systematic review aims to bring the molecular mechanisms involved in BC chemoresistance and extract from the previous literature information regarding the use of nanoparticles as potential treatment for chemoresistant breast cancer.

Synthesis, biological properties and structural study of new halogenated azolo[4,5-b]pyridines as inhibitors of CK2 kinase

The new halogenated 1H-triazolo[4,5-b]pyridines and 1H-imidazo[4,5-b]pyridines were synthesised as analogues of known CK2 inhibitors: 4,5,6,7-tetrabromo-1H-benzotriazole (TBBt) and 4,5,6,7-tetrabromo-1H-benzimidazole (TBBi). Their influence on the activity of recombinant human CK2α, CK2α' and PIM1 kinases was determined. The most active inhibitors were di- and trihalogenated 1H-triazolo[4,5-b]pyridines (4a, 5a and 10a) with IC₅₀ values 2.56, 3.82 and 3.26 μM respectively for CK2α. Furthermore, effect on viability of cancer cell lines MCF-7 (human breast adenocarcinoma) and CCRF-CEM (T lymphoblast leukemia) of all final compounds was evaluated. Finally, three crystal structures of complexes of CK2α^1-335 with inhibitors 4a, 5a and 10a were obtained. In addition, new protocol was used to obtain high-resolution crystal structures of CK2α'^Cys336Ser in complex with four inhibitors (4a, 5a, 5b, 10a).

Identification of afzelin potential targets in inhibiting triple-negative breast cancer cell migration using reverse docking

BACKGROUND

Triple-negative breast cancer (TNBC) tends to be aggressive and metastatic, characteristics attributable to its cellular migration capabilities. Afzelin is a chemical compound with anti-metastatic potentials. This study aimed to predict proteins involved in TNBC cell migration which could be inhibited by afzelin.

METHODS

The protein database was constructed from the Kyoto Encyclopedia of Genes and Genomes pathways collection which related to cell motility, then screened for druggability using SuperTarget and Therapeutic Target Database. The involvement of druggable proteins in the TNBC metastasis process was investigated through existing publications in The National Center for Biotechnology Information PubMed database. Inhibitory potential of afzelin toward target proteins was compared to the proteins' known-inhibitor, using the reverse docking method.

RESULTS

Ten proteins identified as potential targets of afzelin, with the top 3 being ERK2, KRas, and FAK, respectively. Afzelin's 3-O-rhamnoside group played a dominant role in forming hydrogen bonds with the target proteins. Further analysis with STRING suggested that afzelin might be able to inhibit chemotaxis and haptotaxis of TNBC cells.

CONCLUSIONS

Afzelin was predicted to inhibit TNBC cell motility, by targeting ERK2, KRas, and FAK activation.

Bioengineered siRNA-Based Nanoplatforms Targeting Molecular Signaling Pathways for the Treatment of Triple Negative Breast Cancer: Preclinical and Clinical Advancements

Triple negative breast cancer (TNBC) is one of the most aggressive types of breast cancer. Owing to the absenteeism of hormonal receptors expressed at the cancerous breast cells, hormonal therapies and other medications targeting human epidermal growth factor receptor 2 (HER2) are ineffective in TNBC patients, making traditional chemotherapeutic agents the only current appropriate regimen. Patients' predisposition to relapse and metastasis, chemotherapeutics' cytotoxicity and resistance and poor prognosis of TNBC necessitates researchers to investigate different novel-targeted therapeutics. The role of small interfering RNA (siRNA) in silencing the genes/proteins that are aberrantly overexpressed in carcinoma cells showed great potential as part of TNBC therapeutic regimen. However, targeting specificity, siRNA stability, and delivery efficiency cause challenges in the progression of this application clinically. Nanotechnology was highlighted as a promising approach for encapsulating and transporting siRNA with high efficiency-low toxicity profile. Advances in preclinical and clinical studies utilizing engineered siRNA-loaded nanotherapeutics for treatment of TNBC were discussed. Specific and selective targeting of diverse signaling molecules/pathways at the level of tumor proliferation and cell cycle, tumor invasion and metastasis, angiogenesis and tumor microenvironment, and chemotherapeutics' resistance demonstrated greater activity via integration of siRNA-complexed nanoparticles.

Roles of CDK/Cyclin complexes in transcription and pre-mRNA splicing: Cyclins L and CDK11 at the cross-roads of cell cycle and regulation of gene expression

Cyclin Dependent Kinases (CDKs) represent a large family of serine/threonine protein kinases that become active upon binding to a Cyclin regulatory partner. CDK/cyclin complexes recently identified, as well as "canonical" CDK/Cyclin complexes regulating cell cycle, are implicated in the regulation of gene expression via the phosphorylation of key components of the transcription and pre-mRNA processing machineries. In this review, we summarize the role of CDK/cyclin-dependent phosphorylation in the regulation of transcription and RNA splicing and highlight recent findings that indicate the involvement of CDK11/cyclin L complexes at the cross-roads of cell cycle, transcription and RNA splicing. Finally, we discuss the potential of CDK11 and Cyclins L as therapeutic targets in cancer.

Betulinic acid triggers apoptosis and inhibits migration and invasion of gastric cancer cells by impairing EMT progress

Gastric cancer (GC) is one of the most prevalent types of malignancies. Betulinic acid (BA) is a natural pentacyclic triterpene with a lupine structure. However, to the best of our knowledge, there is no research study on the anti‐tumour and anti‐metastasis effect of BA on GC. In this study, we assessed the anti‐cancer effect of BA on human GC cells in vitro and in vivo. We first investigated the cytotoxicity and anti‐proliferation effect of BA on GC cells of SNU‐16 and NCI‐N87. The results indicated that BA had significant cytotoxic and inhibitory effects on GC cells in a dose‐ and time‐dependent manner. To further study the cytotoxic action of BA on GC cells, we assessed the apoptotic induction effect of BA on SNU‐16 cells and found that BA distinctly induced apoptosis in SNU‐16 cells. In addition, BA inhibited the migratory and invasive abilities of SNU‐16 cells. Western‐blot analysis revealed that BA suppressed the migration and invasion of GC cells by impairing epithelial‐mesenchymal transition progression. Furthermore, in vivo experiments showed that BA could delay tumour growth and inhibit pulmonary metastasis, which is consistent with the results of in vitro studies. Overall, we evaluated the anti‐cancer effect of BA on human GC cells in vivo and in vitro, and the present study provides new evidence on the use of BA as a potential anti‐cancer drug for GC treatment.

Significance of the study

BA significantly suppressed proliferation and triggered apoptosis in GC cells. Additionally, BA remarkably inhibited migration and invasion of GC cells by impairing the epithelial‐mesenchymal transition signalling pathway. It is worth noting that BA drastically retarded tumour growth in the xenograft mouse model of GC. Our results indicated that BA can be considered a candidate drug for GC therapy.

Uncovering the Translational Regulatory Activity of the Tumor Suppressor BRCA1

BRCA1 inactivation is a hallmark of familial breast cancer, often associated with aggressive triple negative breast cancers. BRCA1 is a tumor suppressor with known functions in DNA repair, transcription regulation, cell cycle control, and apoptosis. In the present study, we demonstrate that BRCA1 is also a translational regulator. We previously showed that BRCA1 was implicated in translation regulation. Here, we asked whether translational control could be a novel function of BRCA1 that contributes to its tumor suppressive activity. A combination of RNA-binding protein immunoprecipitation, microarray analysis, and polysome profiling, was used to identify the mRNAs that were specifically deregulated under BRCA1 deficiency. Western blot analysis allowed us to confirm at the protein level the deregulated translation of a subset of mRNAs. A unique and dedicated cohort of patients with documented germ-line BRCA1 pathogenic variant statues was set up, and tissue microarrays with the biopsies of these patients were constructed and analyzed by immunohistochemistry for their content in each candidate protein. Here, we show that BRCA1 translationally regulates a subset of mRNAs with which it associates. These mRNAs code for proteins involved in major programs in cancer. Accordingly, the level of these key proteins is correlated with BRCA1 status in breast cancer cell lines and in patient breast tumors. ADAT2, one of these key proteins, is proposed as a predictive biomarker of efficacy of treatments recently recommended to patients with BRCA1 deficiency. This study proposes that translational control may represent a novel molecular mechanism with potential clinical impact through which BRCA1 is a tumor suppressor.

Coordinated targeting of CK2 and KIT in gastrointestinal stromal tumours

Background

Most gastrointestinal stromal tumours (GIST) are driven by activating oncogenic mutations of KIT/PDGFRA, which provide a compelling therapeutic target. Our previous studies showed that CDC37, regulated by casein kinase 2 (CK2), is a crucial HSP90 cofactor for KIT oncogenic function and a promising and more selective therapeutic target in GIST.

Methods

Biologic mechanisms of CK2-mediated CDC37 regulation were assessed in GISTs by immunoblotting, immunoprecipitations, knockdown and inactivation assays. The effects of a combination of KIT and CK2 inhibition were assessed by immunoblotting, cell viability, colony growth, cell cycle analysis, apoptosis, migration and invasiveness.

Results

CK2 overexpression was demonstrated by immunoblotting in GIST cell lines and patient biopsies. Treatment with a specific CK2 inhibitor, CX4945, leads to CDC37 dephosphorylation and inhibits KIT signalling in imatinib-sensitive and in imatinib-resistant GIST cell lines. Immunoprecipitation demonstrated that CK2 inhibition blocks KIT:HSP90:CDC37 interaction in GIST cells. Coordinated inhibition of CK2 and KIT by CX4945 (or CK2 shRNA) and imatinib, respectively, leads to increased apoptosis, anti-proliferative effects and cell cycle arrest and decreased p-AKT and p-S6 expression, migration and invasiveness in all GIST cell lines compared with either intervention alone, indicating additive effects of inhibiting these two important regulators of GIST biology.

Conclusion

Our findings suggest that combinatorial inhibition of CK2 and KIT warrants evaluation as a novel therapeutic strategy in GIST, especially in imatinib-resistant GIST.

Transcriptional activation of CBFβ by CDK11p110 is necessary to promote osteosarcoma cell proliferation

BACKGROUND

Aberrant expression of cyclin-dependent protein kinases (CDK) is a hallmark of cancer. CDK11 plays a crucial role in cancer cell growth and proliferation. However, the molecular mechanisms of CDK11 and CDK11 transcriptionally regulated genes are largely unknown.

METHODS

In this study, we performed a global transcriptional analysis using gene array technology to investigate the transcriptional role of CDK11 in osteosarcoma. The promoter luciferase assay, chromatin immunoprecipitation assay, and Gel Shift assay were used to identify direct transcriptional targets of CDK11. Clinical relevance and function of core-binding factor subunit beta (CBFβ) were further accessed in osteosarcoma.

RESULTS

We identified a transcriptional role of protein-DNA interaction for CDK11p110, but not CDK11p58, in the regulation of CBFβ expression in osteosarcoma cells. The CBFβ promoter luciferase assay, chromatin immunoprecipitation assay, and Gel Shift assay confirmed that CBFβ is a direct transcriptional target of CDK11. High expression of CBFβ is associated with poor outcome in osteosarcoma patients. Expression of CBFβ contributes to the proliferation and metastatic behavior of osteosarcoma cells.

CONCLUSIONS

These data establish CBFβ as a mediator of CDK11p110 dependent oncogenesis and suggest that targeting the CDK11- CBFβ pathway may be a promising therapeutic strategy for osteosarcoma treatment.

Fucoidan Promotes Apoptosis and Inhibits EMT of Breast Cancer Cells

Fucoidan is an active component of seaweed, and could inhibit proliferation and induce apoptotic cell death in several tumor cells. However, the function of fucoidan in breast cancer is largely unknown. In the present study, we evaluated the anti-cancer potential of fucoidan in human breast cancer MCF-7 cells. Adult Sprague-Dawley rats were randomized to receive fucoidan (200 or 400 mg/kg·body weight per day) or normal saline via gastric gavage for 3 consecutive days. Serum samples were prepared from these rats, and used for subsequent experiments to examine the potential effects in MCF-7 cells. Cell viability was determined using a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Apoptosis was examined with Hoechst33258 staining and flow cytometry. Cell migration and invasion were measured by wound scratch assay and Transwell assay, respectively. Western blot and enzyme-linked immunosorbent assay (ELISA) were used to examine the expression of secretory E-cadherin and matrix metalloproteinase-9 (MMP-9). Conditioned serum from fucoidan-treated rats significantly suppressed cell proliferation and enhanced apoptosis. Cell migration and invasion were also significantly decreased. Observed effects of conditioned serum were associated with upregulation of E-cadherin and downregulation of MMP-9. Conditioned serum of rats treated with fucoidan could inhibit the proliferation and promote apoptosis of MCF-7 cells. Cell invasion and migration were inhibited, possibly via decreased epithelial-mesenchymal transition (EMT) process. Fucoidan may be a promising therapeutic agent for human breast cancers.

CDK11 Loss Induces Cell Cycle Dysfunction and Death of BRAF and NRAS Melanoma Cells

Cyclin dependent kinase 11 (CDK11) is a protein kinase that regulates RNA transcription, pre-mRNA splicing, mitosis, and cell death. Targeting of CDK11 expression levels is effective in the experimental treatment of breast and other cancers, but these data are lacking in melanoma. To understand CDK11 function in melanoma, we evaluated protein and RNA levels of CDK11, Cyclin L1 and Cyclin L2 in benign melanocytes and BRAF- as well as NRAS-mutant melanoma cell lines. We investigated the effectiveness of reducing expression of this survival kinase using RNA interference on viability, clonal survival, and tumorsphere formation in melanoma cell lines. We examined the impact of CDK11 loss in BRAF-mutant melanoma on more than 700 genes important in cancer signaling pathways. Follow-up analysis evaluated how CDK11 loss alters cell cycle function in BRAF- and NRAS-mutant melanoma cells. We present data on CDK11, CCNL1 and CCNL2 mRNA expression in melanoma patients, including prognosis for survival. In sum, we found that CDK11 is necessary for melanoma cell survival, and a major impact of CDK11 loss in melanoma is to cause disruption of the cell cycle distribution with accumulation of G1- and loss of G2/M-phase cancer cells.

CDK11p110 plays a critical role in the tumorigenicity of esophageal squamous cell carcinoma cells and is a potential drug target

Esophageal squamous cell carcinoma (ESCC) is a serious malignancy with limited options for targeted therapy. The exploration of novel targeted therapies for combating ESCC is urgently needed. Cyclin-dependent kinases (CDKs) play important roles in the progression of cancers; however, the function of CDK11^p110 (cyclin-dependent kinase 11^p110) in ESCC is still unknown. Here, we investigated the effects and molecular mechanisms of CDK11^p110 in the proliferation and growth of ESCC by examining the expression of CDK11^p110 in ESCC tissues and by detecting phenotypic changes in ESCC cells after CDK11^p110 knockdown or overexpression in vitro and in vivo. According to the tissue microarray analysis, compared with its expression level in normal tissues, the expression level of CDK11^p110 was significantly elevated in ESCC tissues; this result was in concordance with the data in TCGA (The Cancer Genome Atlas) datasets. In addition, RNAi-mediated CDK11^p110 silencing exerted a substantial inhibitory effect on the proliferation, clonogenicity and migration ability of ESCC cells. Further study indicated that CDK11^p110 knockdown arrested ESCC cells in the G2/M phase of the cell cycle and induced cell apoptosis. Moreover, stable shRNA-mediated CDK11^p110 knockdown inhibited tumor growth in an ESCC xenograft model, and overexpression of CDK11^p110 enhanced tumor growth. In addition, the Ki67 proliferation index was closely associated with the elevation or depletion of CDK11^p110 in vivo. In summary, this study provides evidence that CDK11^p110 play a critical role in the tumorigenicity of ESCC cells, which suggests that CDK11^p110 may be a promising therapeutic target in ESCC. Abbreviations: CDKs: cyclin-dependent kinases; CDK11: Cyclin-dependent kinase 11; CDK11^p110: Cyclin-dependent kinase 11^p110, the larger isomer of cyclin-dependent kinase 11; ESCC: esophageal squamous cell carcinoma; FACS: fluorescence-activated cell sorting; FDA: the Food and Drug Administration; TCGA: The Cancer Genome Atlas; TMA: tissue microarray.

Protein Kinase CK2, a Potential Therapeutic Target in Carcinoma Management

The Protein kinase CK2 (formerly known as casein kinase 2) is a highly conserved serine/ threonine kinase overexpressed in various human carcinomas and its high expression often correlates with poor prognosis. CK2 protein is localized in the nucleus of many tumor cells and correlates with clinical features in many cases. Increased expression of CK2 in mice results in the development of various types of carcinomas (both solids and blood related tumors, such as (breast carcinoma, lymphoma, etc), which reveals its carcinogenic properties. CK2 plays essential roles in many key biological processes related to carcinoma, including cell apoptosis, DNA damage responses and cell cycle regulation. CK2 has become a potential anti-carcinoma target. Various CK2 inhibitors have been developed with anti-neoplastic properties against a variety of carcinomas. Some CK2 inhibitors have showed good results in in vitro and pre-clinical models, and have even entered in clinical trials. This article will review effects of CK2 and its inhibitors on common carcinomas in in vitro and pre-clinical studies.

Validation of a network-based strategy for the optimization of combinatorial target selection in breast cancer therapy: siRNA knockdown of network targets in MDA-MB-231 cells as an in vitro model for inhibition of tumor development

Network-based strategies provided by systems biology are attractive tools for cancer therapy. Modulation of cancer networks by anticancer drugs may alter the response of malignant cells and/or drive network re-organization into the inhibition of cancer progression. Previously, using systems biology approach and cancer signaling networks, we identified top-5 highly expressed and connected proteins (HSP90AB1, CSNK2B, TK1, YWHAB and VIM) in the invasive MDA-MB-231 breast cancer cell line. Here, we have knocked down the expression of these proteins, individually or together using siRNAs. The transfected cell lines were assessed for in vitro cell growth, colony formation, migration and invasion relative to control transfected MDA-MB-231, the non-invasive MCF-7 breast carcinoma cell line and the non-tumoral mammary epithelial cell line MCF-10A. The knockdown of the top-5 upregulated connectivity hubs successfully inhibited the in vitro proliferation, colony formation, anchorage independence, migration and invasion in MDA-MB-231 cells; with minimal effects in the control transfected MDA-MB-231 cells or MCF-7 and MCF-10A cells. The in vitro validation of bioinformatics predictions regarding optimized multi-target selection for therapy suggests that protein expression levels together with protein-protein interaction network analysis may provide an optimized combinatorial target selection for a highly effective anti-metastatic precision therapy in triple-negative breast cancer. This approach increases the ability to identify not only druggable hubs as essential targets for cancer survival, but also interactions most susceptible to synergistic drug action. The data provided in this report constitute a preliminary step toward the personalized clinical application of our strategy to optimize the therapeutic use of anti-cancer drugs.

CK2 targeted RNAi therapeutic delivered via malignant cell-directed tenfibgen nanocapsule: dose and molecular mechanisms of response in xenograft prostate tumors

CK2, a protein serine/threonine kinase, promotes cell proliferation and suppresses cell death. This essential-for-survival signal demonstrates elevated expression and activity in all cancers examined, and is considered an attractive target for cancer therapy. Here, we present data on the efficacy of a tenfibgen (TBG) coated nanocapsule which delivers its cargo of siRNA (siCK2) or single stranded RNA/DNA oligomers (RNAi-CK2) simultaneously targeting CK2α and α' catalytic subunits. Intravenous administration of TBG-siCK2 or TBG-RNAi-CK2 resulted in significant xenograft tumor reduction at low doses in PC3-LN4 and 22Rv1 models of prostate cancer. Malignant cell uptake and specificity in vivo was verified by FACS analysis and immunofluorescent detection of nanocapsules and PCR detection of released oligomers. Dose response was concordant with CK2αα' RNA transcript levels and the tumors demonstrated changes in CK2 protein and in markers of proliferation and cell death. Therapeutic response corresponded to expression levels for argonaute and GW proteins, which function in oligomer processing and translational repression. No toxicity was detected in non-tumor tissues or by serum chemistry. Tumor specific delivery of anti-CK2 RNAi via the TBG nanoencapsulation technology warrants further consideration of translational potential.

Okur-Chung neurodevelopmental syndrome: Eight additional cases with implications on phenotype and genotype expansion

Okur-Chung syndrome is a neurodevelopmental condition attributed to germline CSNK2A1 pathogenic missense variants. We present 8 unreported subjects with the above syndrome, who have recognizable dysmorphism, varying degrees of developmental delay and multisystem involvement. Together with 6 previously reported cases, we present a case series of 7 female and 7 male subjects, highlighting the recognizable facial features of the syndrome (microcephaly, hypertelorism, epicanthic fold, ptosis, arched eyebrows, low set ears, ear fold abnormality, broad nasal bridge and round face) as well as frequently occurring clinical features including neurodevelopmental delay (93%), gastrointestinal (57%), musculoskeletal (57%) and immunological (43%) abnormalities. The variants reported in this study are evolutionary conserved and absent in the normal population. We observed that the CSNK2A1 gene is relatively intolerant to missense genetic changes, and most variants are within the protein kinase domain. All except 1 variant reported in this cohort are spatially located on the binding pocket of the holoenzyme. We further provide key recommendations on the management of Okur-Chung syndrome. To conclude, this is the second case series on Okur-Chung syndrome, and an in-depth review of the phenotypic features and genomic findings of the condition with suggestions on clinical management.

Evaluation of protein kinase CK2 as a therapeutic target for squamous cell carcinoma of cats

OBJECTIVE To investigate protein kinase CK2 (CK2) expression in squamous cell carcinoma (SCC) of cats and to examine effects of CK2 downregulation on in vitro apoptosis and viability in SCC. SAMPLE Biopsy specimens of oral mucosa and testis and blood samples from clinically normal cats, biopsy specimens of oral SCC from cats, and feline SCC (SCCF1) and mammary gland carcinoma (K12) cell lines. PROCEDURES Immunohistochemical labeling for CK2α was performed on biopsy specimens. Sequences of the CK2α subunit gene and CK2α' subunit gene in feline blood and feline cancer cell lines were determined by use of PCR and reverse-transcription PCR assays followed by direct Sanger sequencing. Specific small interfering RNAs (siRNAs) were developed for feline CK2α and CK2α'. The SCCF1 cells were treated with siRNA and assessed 72 hours later for CK2α and CK2α' expression and markers of apoptosis (via western blot analysis) and for viability (via 3-[4,5-dimethylthiazol-2-yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H-tetrazolium assays). RESULTS CK2α was expressed in all feline oral mucosa samples and 7 of 8 oral SCC samples. Expression of CK2α and CK2α' was successfully downregulated in SCCF1 cells by use of siRNAs, which resulted in decreased viability and induction of apoptosis. CONCLUSIONS AND CLINICAL RELEVANCE In this study, CK2 appeared to be a promising therapeutic target for SCCs of cats. A possible treatment strategy for SCCs of cats would be RNA interference that targets CK2.

Inhibitors of cyclin-dependent kinases as cancer therapeutics

Over the past two decades there has been a great deal of interest in the development of inhibitors of the cyclin-dependent kinases (CDKs). This attention initially stemmed from observations that different CDK isoforms have key roles in cancer cell proliferation through loss of regulation of the cell cycle, a hallmark feature of cancer. CDKs have now been shown to regulate other processes, particularly various aspects of transcription. The early non-selective CDK inhibitors exhibited considerable toxicity and proved to be insufficiently active in most cancers. The lack of patient selection biomarkers and an absence of understanding of the inhibitory profile required for efficacy hampered the development of these inhibitors. However, the advent of potent isoform-selective inhibitors with accompanying biomarkers has re-ignited interest. Palbociclib, a selective CDK4/6 inhibitor, is now approved for the treatment of ER+/HER2- advanced breast cancer. Current developments in the field include the identification of potent and selective inhibitors of the transcriptional CDKs; these include tool compounds that have allowed exploration of individual CDKs as cancer targets and the determination of their potential therapeutic windows. Biomarkers that allow the selection of patients likely to respond are now being discovered. Drug resistance has emerged as a major hurdle in the clinic for most protein kinase inhibitors and resistance mechanism are beginning to be identified for CDK inhibitors. This suggests that the selective inhibitors may be best used combined with standard of care or other molecularly targeted agents now in development rather than in isolation as monotherapies.

Silencing the roadblocks to effective triple-negative breast cancer treatments by siRNA nanoparticles

Over the past decade, RNA interference (RNAi) has been ubiquitously utilized to study biological function in vitro; however, limitations were associated with its utility in vivo More recently, small interfering RNA (siRNA) nanoparticles with improved biocompatibility have gained prevalence as a potential therapeutic option for the treatment of various diseases. The adaptability of siRNA nanoparticles enables the delivery of virtually any siRNA, which is especially advantageous for therapeutic applications in heterogeneous diseases that lack unifying molecular features, such as triple-negative breast cancer (TNBC). TNBC is an aggressive subtype of breast cancer that is stratified by the lack of estrogen receptor/progesterone receptor expression and HER2 amplification. There are currently no FDA-approved targeted therapies for the treatment of TNBCs, making cytotoxic chemotherapy the only treatment option available to these patients. In this review, we outline the current status of siRNA nanoparticles in clinical trials for cancer treatment and discuss the promising preclinical approaches that have utilized siRNA nanoparticles for TNBC treatment. Next, we address TNBC subtype-specific therapeutic interventions and highlight where and how siRNA nanoparticles fit into these strategies. Lastly, we point out ongoing challenges in the field of siRNA nanoparticle research that, if addressed, would significantly improve the efficacy of siRNA nanoparticles as a therapeutic option for cancer treatment.

Androgen receptor is a potential novel prognostic marker and oncogenic target in osteosarcoma with dependence on CDK11

Osteosarcoma is the most common bone cancer in children and adolescents. Previously, we have found that cyclin-dependent kinase 11 (CDK11) signaling was essential for osteosarcoma cell growth and survival. Subsequently, CDK11 siRNA gene targeting, expression profiling, and network reconstruction of differentially expressed genes were performed between CDK11 knock down and wild type osteosarcoma cells. Reconstructed network of the differentially expressed genes pointed to the AR as key to CDK11 signaling in osteosarcoma. CDK11 increased transcriptional activation of AR gene in osteosarcoma cell lines. AR protein was highly expressed in various osteosarcoma cell lines and patient tumor tissues. Tissue microarray analysis showed that the disease-free survival rate for patients with high-expression of AR was significantly shorter than for patients with low-expression of AR. In addition, AR gene expression knockdown via siRNA greatly inhibited cell growth and viability. Similar results were found in osteosarcoma cells treated with AR inhibitor. These findings suggest that CDK11 is involved in the regulation of AR pathway and AR can be a potential novel prognostic marker and therapeutic target for osteosarcoma treatment.

CK2 Molecular Targeting-Tumor Cell-Specific Delivery of RNAi in Various Models of Cancer

Protein kinase CK2 demonstrates increased protein expression relative to non-transformed cells in the majority of cancers that have been examined. The elevated levels of CK2 are involved in promoting not only continued proliferation of cancer cells but also their resistance to cell death; thus, CK2 has emerged as a plausible target for cancer therapy. Our focus has been to target CK2 catalytic subunits at the molecular level using RNA interference (RNAi) strategies to achieve their downregulation. The delivery of oligonucleotide therapeutic agents warrants that they are protected and are delivered specifically to cancer cells. The latter is particularly important since CK2 is a ubiquitous signal that is essential for survival. To achieve these goals, we have developed a nanocapsule that has the properties of delivering an anti-CK2 RNAi therapeutic cargo, in a protected manner, specifically to cancer cells. Tenfibgen (TBG) is used as the ligand to target tenascin-C receptors, which are elevated in cancer cells. This strategy is effective for inhibiting growth and inducing death in several types of xenograft tumors, and the nanocapsule elicits no safety concerns in animals. Further investigation of this therapeutic approach for its translation is warranted.

CK2 in Cancer: Cellular and Biochemical Mechanisms and Potential Therapeutic Target

CK2 genes are overexpressed in many human cancers, and most often overexpression is associated with worse prognosis. Site-specific expression in mice leads to cancer development (e.g., breast, lymphoma) indicating the oncogenic nature of CK2. CK2 is involved in many key aspects of cancer including inhibition of apoptosis, modulation of signaling pathways, DNA damage response, and cell cycle regulation. A number of CK2 inhibitors are now available and have been shown to have activity against various cancers in vitro and in pre-clinical models. Some of these inhibitors are now undergoing exploration in clinical trials as well. In this review, we will examine some of the major cancers in which CK2 inhibition has promise based on in vitro and pre-clinical studies, the proposed cellular and signaling mechanisms of anti-cancer activity by CK2 inhibitors, and the current or recent clinical trials using CK2 inhibitors.

The roles and therapeutic potential of cyclin-dependent kinases (CDKs) in sarcoma

Uncontrolled proliferation and cell growth is the hallmark of many different malignant diseases, including sarcomas. Cyclin-dependent kinases (CDKs) are members of the serine/threonine protein kinase family and play crucial roles in tumor cell proliferation and growth by controlling cell cycle, transcription, and RNA splicing. In addition, several CDKs influence multiple targets and phosphorylate transcription factors involved in tumorigenesis. There are many examples linking dysregulated activation and expression of CDKs to tumors, and targeting CDKs in tumor cells has become a promising therapeutic strategy. More recently, the Food and Drug Administration (FDA) has approved the CDK4/6 inhibitor palbociclib for treating metastatic breast cancer. In sarcomas, high levels of CDK mRNA and protein expression have been found in most human sarcoma cells and patient tissues. Many studies have demonstrated consistent results in which inhibition of different CDKs decrease sarcoma cell growth and induce apoptosis. Therefore, CDKs comprise an attractive set of targets for novel anti-sarcoma drug development. In this review, we discuss the roles of different members of CDKs in various sarcomas and provide a pre-clinical overview of promising therapeutic potentials of targeting CDKs with a special emphasis on sarcoma.

CDK11 in TREX/THOC Regulates HIV mRNA 3' End Processing

Transcriptional cyclin-dependent kinases play important roles in eukaryotic gene expression. CDK7, CDK9 (P-TEFb), and CDK13 are also critical for HIV replication. However, the function of CDK11 remained enigmatic. In this report, we determined that CDK11 regulates the cleavage and polyadenylation (CPA) of all viral transcripts. CDK11 was found associated with the TREX/THOC, which recruited this kinase to DNA. Once at the viral genome, CDK11 phosphorylated serines at position 2 in the CTD of RNAPII, which increased levels of CPA factors at the HIV 3' end. In its absence, cleavage of viral transcripts was greatly attenuated. In contrast, higher levels of CDK11 increased the length of HIV poly(A) tails and the stability of mature viral transcripts. We conclude that CDK11 plays a critical role for the cotranscriptional processing of all HIV mRNA species.

The emerging roles and therapeutic potential of cyclin-dependent kinase 11 (CDK11) in human cancer

Overexpression and/or hyperactivation of cyclin-dependent kinases (CDKs) are common features of most cancer types. CDKs have been shown to play important roles in tumor cell proliferation and growth by controlling cell cycle, transcription, and RNA splicing. CDK4/6 inhibitor palbociclib has been recently approved by the FDA for the treatment of breast cancer. CDK11 is a serine/threonine protein kinase in the CDK family and recent studies have shown that CDK11 also plays critical roles in cancer cell growth and proliferation. A variety of genetic and epigenetic events may cause universal overexpression of CDK11 in human cancers. Inhibition of CDK11 has been shown to lead to cancer cell death and apoptosis. Significant evidence has suggested that CDK11 may be a novel and promising therapeutic target for the treatment of cancers. This review will focus on the emerging roles of CDK11 in human cancers, and provide a proof-of-principle for continued efforts toward targeting CDK11 for effective cancer treatment.

Cyclin-Dependent Kinase 11 (CDK11) Is Required for Ovarian Cancer Cell Growth In Vitro and In Vivo, and Its Inhibition Causes Apoptosis and Sensitizes Cells to Paclitaxel

Ovarian cancer is currently the most lethal gynecologic malignancy with limited treatment options. Improved targeted therapies are needed to combat ovarian cancer. Here, we report the identification of cyclin-dependent kinase 11 (CDK11) as a mediator of tumor cell growth and proliferation in ovarian cancer cells. Although CDK11 has not been implicated previously in this disease, we have found that its expression is upregulated in human ovarian cancer tissues and associated with malignant progression. Metastatic and recurrent tumors have significantly higher CDK11 expression when compared with the matched, original primary tumors. RNAi-mediated CDK11 silencing by synthetic siRNA or lentiviral shRNA decreased cell proliferation and induced apoptosis in ovarian cancer cells. Moreover, CDK11 knockdown enhances the cytotoxic effect of paclitaxel to inhibit cell growth in ovarian cancer cells. Systemic in vivo administration of CDK11 siRNA reduced the tumor growth in an ovarian cancer xenograft model. Our findings suggest that CDK11 may be a promising therapeutic target for the treatment of ovarian cancer patients. Mol Cancer Ther; 15(7); 1691-701. ©2016 AACR.

Cyclin-Dependent Kinase CRK9, Required for Spliced Leader trans Splicing of Pre-mRNA in Trypanosomes, Functions in a Complex with a New L-Type Cyclin and a Kinetoplastid-Specific Protein

In eukaryotes, cyclin-dependent kinases (CDKs) control the cell cycle and critical steps in gene expression. The lethal parasite Trypanosoma brucei, member of the phylogenetic order Kinetoplastida, possesses eleven CDKs which, due to high sequence divergence, were generically termed CDC2-related kinases (CRKs). While several CRKs have been implied in the cell cycle, CRK9 was the first trypanosome CDK shown to control the unusual mode of gene expression found in kinetoplastids. In these organisms, protein-coding genes are arranged in tandem arrays which are transcribed polycistronically. Individual mRNAs are processed from precursor RNA by spliced leader (SL) trans splicing and polyadenylation. CRK9 ablation was lethal in cultured trypanosomes, causing a block of trans splicing before the first transesterification step. Additionally, CRK9 silencing led to dephosphorylation of RNA polymerase II and to hypomethylation of the SL cap structure. Here, we tandem affinity-purified CRK9 and, among potential CRK9 substrates and modifying enzymes, discovered an unusual tripartite complex comprising CRK9, a new L-type cyclin (CYC12) and a protein, termed CRK9-associated protein (CRK9AP), that is only conserved among kinetoplastids. Silencing of either CYC12 or CRK9AP reproduced the effects of depleting CRK9, identifying these proteins as functional partners of CRK9 in vivo. While mammalian cyclin L binds to CDK11, the CRK9 complex deviates substantially from that of CDK11, requiring CRK9AP for efficient CRK9 complex formation and autophosphorylation in vitro. Interference with this unusual CDK rescued mice from lethal trypanosome infections, validating CRK9 as a potential chemotherapeutic target.

Protein Kinase CK2 Expression Predicts Relapse Survival in ERα Dependent Breast Cancer, and Modulates ERα Expression in Vitro

The heterotetrameric protein kinase CK2 has been associated with oncogenic transformation, and our previous studies have shown that it may affect estrogenic signaling. Here, we investigate the role of the protein kinase CK2 in regulating ERα (estrogen receptor α) signaling in breast cancer. We determined the correlation of CK2α expression with relapse free breast cancer patient survival utilizing Kaplan Meier Plotter (kmplot.com/analysis/) to mine breast cancer microarrays repositories. Patients were stratified according to ERα status, histological grade, and hormonal therapy. Luciferase reporter assays and flow cytometry were implemented to determine the impact of CK2 inhibition on ERE-mediated gene expression and expression of ERα protein. CK2α expression is associated with shorter relapse free survival among ERα (+) patients with grade 1 or 2 tumors, as well as among those patients receiving hormonal therapy. Biochemical inhibition of CK2 activity results in increased ER-transactivation as well as increased expression among ERα (+) and ERα (−) breast cancer cell lines. These findings suggest that CK2 may contribute to estrogen-independent cell proliferation and breast tumor progression, and may potentially serve as a biomarker and pharmacological target in breast cancer.

Casein kinases as potential therapeutic targets

INTRODUCTION

The conventional term 'casein kinase' (CK) denotes three classes of kinases - CK1, CK2 and Golgi-CK (G-CK)/Fam20C (family with sequence similarity 20, member C) - sharing the ability to phoshorylate casein in vitro, but otherwise unrelated to each other. All CKs have been reported to be implicated in human diseases, and reviews individually dealing with the druggability of CK1 and CK2 are available. Our aim is to provide a comparative analysis of the three classes of CKs as therapeutic targets.

AREAS COVERED

CK2 is the CK for which implication in neoplasia is best documented, with the survival of cancer cells often relying on its overexpression. An ample variety of cell-permeable CK2 inhibitors have been developed, with a couple of these now in clinical trials. Isoform-specific CK1 inhibitors that are expected to play a beneficial role in oncology and neurodegeneration have been also developed. In contrast, the pathogenic potential of G-CK/Fam20C is caused by its loss of function. Activators of Fam20C, notably sphingolipids and their analogs, may prove beneficial in this respect.

EXPERT OPINION

Optimization of CK2 and CK1 inhibitors will prove useful to develop new therapeutic strategies for treating cancer and neurodegenerative disorders, while the design of potent activators of G-CK/Fam20C will provide a new tool in the fields of bio-mineralization and hypophosphatemic diseases.