Kinome-Wide Screening with Small Interfering RNA Identified Polo-like Kinase 1 as a Key Regulator of Proliferation in Oral Cancer Cells

SLC12A8 mediates TKI resistance in EGFR-mutant lung cancer via PDK1/AKT axis

PURPOSE

Epidermal growth factor receptor (EGFR) mutation is a prominent driver of lung cancer. Tyrosine kinase inhibitors (TKIs) have shown efficacy in treating EGFR-mutant lung cancer, but the emergence of drug resistance poses a significant challenge. Recent research has highlighted solute carrier family 12 member 8 (SLC12A8) as one of the highly upregulated genes in various cancer types. However, its oncogenic function remains largely unexplored.

METHODS

343 consecutive lung cancer patients were prospectively recruited and were followed for over 10 years. SLC12A8 expression in lung cancer tissues was measured by qPCR and was associated with patient survival. The association of SLC12A8 with TKI resistance was studied in in vitro EGFR-mutant lung cancer cell line as well as in in vivo xenograft tumor model. High-throughput kinome screening was employed to investigate SLC12A8-mediated oncogenic signaling pathway in lung cancer.

RESULTS

SLC12A8 is a predictive biomarker of poor prognosis in lung cancer, particularly in patients with EGFR mutations. SLC12A8 overexpression diminishes the effectiveness of TKIs in EGFR-mutant lung cancer, resulting in treatment failure and disease progression. More importantly, SLC12A8-induced TKI resistance is mediated by the PDK1/AKT signaling axis, while silencing SLC12A8 expression inhibits oncogenic PDK1/AKT signaling, restoring TKI sensitivity in lung cancer cells.

CONCLUSION

SLC12A8 mediates TKI resistance in EGFR-mutant lung cancer via PDK1/AKT axis. These findings not only advance our understanding of the molecular mechanisms driving TKI resistance, but also offer novel alternative strategies for the treatment of lung cancer.

Programming conformational cooperativity to regulate allosteric protein-oligonucleotide signal transduction

Conformational cooperativity is a universal molecular effect mechanism and plays a critical role in signaling pathways. However, it remains a challenge to develop artificial molecular networks regulated by conformational cooperativity, due to the difficulties in programming and controlling multiple structural interactions. Herein, we develop a cooperative strategy by programming multiple conformational signals, rather than chemical signals, to regulate protein-oligonucleotide signal transduction, taking advantage of the programmability of allosteric DNA constructs. We generate a cooperative regulation mechanism, by which increasing the loop lengths at two different structural modules induced the opposite effects manifesting as down- and up-regulation. We implement allosteric logic operations by using two different proteins. Further, in cell culture we demonstrate the feasibility of this strategy to cooperatively regulate gene expression of PLK1 to inhibit tumor cell proliferation, responding to orthogonal protein-signal stimulation. This programmable conformational cooperativity paradigm has potential applications in the related fields.

BI6727 and GSK461364A, potent PLK1 inhibitors induce G2/M arrest and apoptosis against cholangiocarcinoma cell lines

Polo-like kinase 1 (PLK1) is an essential mitotic checkpoint protein that plays a key role in cell cycle division. Overexpression of PLK1 has been associated with poor prognosis in various cancers. Cholangiocarcinoma (CCA) is a lethal bile duct cancer and the current treatments in inoperable patients have not been satisfactory. In order to develop novel targeted therapies, we investigated the efficacy of BI6727 (volasertib) and GSK461364A, polo-like kinase 1 (PLK1) inhibitors in KKU-100 and KKU-213A CCA cell lines. PLK1 expression was significantly up-regulated in CCA cases compared with normal tissues based on the results derived from GEPIA. Western blot results exhibited PLK1 protein expression in both CCA cell lines. Molecular dynamics simulations and free energy calculations based on MM/GBSA method revealed that BI6727-PLK1 and GSK461364A-PLK1 complexes were stable in an aqueous environment, and their complexation was mainly driven by Van der Waals interaction. BI6727 and GSK461364A clearly suppressed CCA cell proliferation and induced G2/M arrest, accompanied with upregulation of cyclin B1 and phosphorylated Histone H3 at Ser10 (pS10H3), specific markers of mitosis. Furthermore, both compounds triggered mitotic catastrophe followed by cell apoptosis via activation of PARP and Caspase 3, as well as downregulation of Mcl-1 anti-apoptotic protein in both CCA cell lines. In conclusion, pharmacologic PLK1 inhibition by BI6727 and GSK461364A blocked survival of CCA cells by several mechanisms. Our study provides evidence that BI6727 and GSK461364A could be alternative drugs and have potential implications at the clinical level for CCA therapy.

Identification of potential druggable targets of cell cycle with small-molecule inhibitors in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common malignant tumors worldwide and there are few crucial regulators and druggable targets for early diagnosis. Therefore, the identification of biomarkers for the early diagnosis and druggable targets of OSCC is imminent. In this study, we integrated gene set enrichment analysis, differential gene expression analysis based on the negative binomial distribution, weighted correlation network analysis, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes into analyzing the OSCC cohort downloaded from The Cancer Genome Atlas, and found that cell cycle and related biologic processes are significantly enriched. Then, we constructed the core gene network of OSCC, which showed the connection of encode human Cyclin-A2 protein, encode RAD51-associated protein 1, encode human centromere-associated protein E (CENPE), encode humans centromere protein I (CENPI) and encode polo-like kinase 1 (PLK1) to several cell cycle-related genes. Survival analysis further showed that low expression of these genes was associated with a better prognosis. Furthermore, we utilized a high-throughput virtual screening to find new CENPE and PLK1 inhibitors, and one of the CENPE inhibitor DB04517 suppressed the proliferation of OSCC cells by cell cycle arrest of cell cycle. Taken together, these candidate regulators could serve as the candidate diagnostic and prognostic biomarkers for OSCC, and specific suppression of these genes may be a potential approach to prevent and treat OSCC with the candidate inhibitors.

miR-509 inhibits cancer stemness properties in oral carcinomas via directly targeting PlK1

Background/purpose

Oral cancer is one of the common cancers worldwide. Emerging evidence has indicated that microRNAs (non-coding RNA molecules of approximately 22 nucleotides in length) are implicated in the regulation of cancer stemness. However, the functional role of microRNA-509 (miR-509) in the characteristics of oral cancer stem cells (CSCs) has not been unraveled.

Materials and methods

The expression level of miR-509 in ALDH1⁺ and sphere oral CSCs was examined by qRT-PCR. The aldehyde dehydrogenase 1 (ALDH1) activity and CD44 expression were assessed using flow cytometry. Self-renewal, transwell migration, and colony formation assays were conducted to measure the CSC phenotypes. Besides, a luciferase reporter assay was used to confirm the direct interaction between miR-509 and its target polo-like kinase 1 (plk1).

Results

We showed the expression of miR-509 was downregulated in the CSCs derived from oral cancer cells (SAS), and upregulation of miR-509 diminished the several CSCs features, including ALDH1 activity, self-renewal capacity, CD44 expression, migration, and colony-forming abilities. Moreover, the result from the luciferase reporter assay validated the direct binding of miR-509 to plk1.

Conclusion

Our results suggest that the miR-509/plk1 axis may mediate the cancer stemness in oral cancer, and targeting this axis may attenuate the progression of oral cancer.

Kinome-Wide siRNA Screening Identifies DYRK1B as a Potential Therapeutic Target for Triple-Negative Breast Cancer Cells

Simple Summary

Therapeutic target is limited for patients with triple-negative breast cancer (TNBC). Through kinome-wide siRNA (709 genes) screening, DYRK1B was identified as a potential gene essential for cell proliferation and mobility of TNBC cells, particularly in DYRK1B highly expressed TNBC cells. TNBC patients with high expression of DYRK1B had poor overall survival and disease-free survival. CCDC97 and ZNF581 were positively correlated with DYRK1B expression and might be involved in DYRK1B-mediated tumor malignancy in TNBC patients, providing DYRK1B as a potential theranostic target for TNBC.

Abstract

Aims: The selective molecules for targeted therapy of triple-negative breast cancer (TNBC) are limited. Several kinases play pivotal roles in cancer development and malignancy. The study aims to determine if any kinases confer to malignancy of TNBC cells, which could serve as a theranostic target for TNBC. Methods: Kinome siRNA library was used to screen selective genes required for the proliferation of TNBC cells. The involvement of DYRK1B in cancer malignancy was evaluated with migration, invasion assays, and spheroid culture. The expression of DYRK1B was confirmed with quantitative PCR and immunoblotting. The clinical correlation of DYRK1B in TNBC patients was examined with tissue microarray and The Cancer Genome Atlas (TCGA) database. Results: Our results showed that silencing DYRK1B significantly suppressed cell viability in DYRK1B-high expressed TNBC cells, likely by arresting the cell cycle at the G₁ phase. Nevertheless, silencing DYRK1B had marginal effects on DYRK1B-low expressed TNBC cells. Similarly, the knockdown of DYRK1B decreased tumorsphere formation and increased cell death of the tumorsphere. Moreover, inactivation of DYRK1B by either specific inhibitor or ectopic expressing catalytic mutant of DYRK1B inhibited cell viability and metastatic characteristics, including migration and invasion. In addition, DYRK1B protein expression was elevated in tumor tissues compared to that in adjacent normal tissues of TNBC patients. Further, DYRK1B gene expression was highly correlated with CCDC97 or ZNF581 genes in TNBC cells and patients. High co-expression of DYRK1B with CCDC97 or ZNF581 was significantly associated with unfavorable overall survival and disease-free survival of TNBC patients. Conclusions: our results suggest DYRK1B might be essential for promoting tumor progression and could be a theranostic target for TNBC. Silencing or inactivation of DYRK1B might be a potential targeted therapy for TNBC.

Deregulation of hsa_circ_0001971/miR-186 and hsa_circ_0001874/miR-296 signaling pathways promotes the proliferation of oral squamous carcinoma cells by synergistically activating SHP2/PLK1 signals

It has been demonstrated that circ_0001874 and circ_0001971 are potential biomarkers for the diagnosis of oral squamous carcinoma (OSCC). MiR-186 was reported to serve as a tumor suppressor in OSCC, and the down-regulation of miR-186 was reported to lead to higher expression of oncogenic factor SHP2 and the activation of growth promoting signaling. In this study, we aimed to explore the possible molecular role of circ_0001874 and circ_0001971 signaling in the pathogenesis of OSCC. RT-qPCR, Western blot, online bioinformatics tools and luciferase assay were utilized to study the molecular signaling pathways of circ_0001874 and circ_0001971. MTT assay and FCM assay were performed to investigate the synergistic effect of circ_0001971 and circ_0001874 on cell proliferation and apoptosis. By observing the effect of different miRNAs on the levels of circ_0001847 and circ_0001971, it was identified that circ_0001847 and circ_0001971 respectively sponged the expression of miR-296 and miR-186 via binding to these miRNAs. Also, SHP2 mRNA and PLK1 mRNA were respectively targeted by miR-186 and miR-296-5p. We also established two signaling pathways, i.e., circ_0001971/miR-186/SHP2 and circ_0001874/miR-296-5p/PLK1, and validated the synergistic effect of circ_0001971 and circ_0001874 via observing their positive effect on cell proliferation and negative effect on cell apoptosis. The expression of miR-186 and miR-296-5p was generally lower in saliva of OSCC patients compared with that in OLK patients, while the expression of miR-186 and miR-296-5p was specifically up-regulated in saliva of OSCC patients. In conclusion, the finding of this study demonstrated that the relative level of hsa_circ_0001971 and hsa_circ_0001874 were different in the saliva of OSCC patients and could be used as predictive biomarkers for the development of OSCC. Furthermore, oncogenic effects of hsa_circ_0001971 and hsa_circ_0001874 in the development of OSCC might be, at least partially, mediated by its downstream signaling pathways including hsa_circ_0001971/microRNA-186/SHP2 and hsa_circ_0001874/microRNA-297/PLK1.

Progression Risk Score Estimation Based on Immunostaining Data in Oral Cancer Using Unsupervised Hierarchical Clustering Analysis: A Retrospective Study in Taiwan

This study aimed to investigate whether the progression risk score (PRS) developed from cytoplasmic immunohistochemistry (IHC) biomarkers is available and applicable for assessing risk and prognosis in oral cancer patients. Participants in this retrospective case-control study were diagnosed between 2012 and 2014 and subsequently underwent surgical intervention. The specimens from surgery were stained by IHC for 16 cytoplasmic target markers. We evaluated the results of IHC staining, clinical and pathological features, progression-free survival (PFS), and overall survival (OS) of 102 oral cancer patients using a novel estimation approach with unsupervised hierarchical clustering analysis. Patients were stratified into high-risk (52) and low-risk (50) groups, according to their PRS; a metric consisting of cytoplasmic PLK1, PhosphoMet, SGK2, and SHC1 expression. Moreover, PRS could be extended for use in the Cox proportional hazard regression model to estimate survival outcomes with associated clinical parameters. Our study findings revealed that the high-risk patients had a significantly increased risk in cancer progression compared with low-risk patients (hazard ratio (HR) = 2.20, 95% confidence interval (CI) = 1.10-2.42, p = 0.026). After considering the influences of demographics, risk behaviors, and tumor characteristics, risk estimation with PRS provided distinct PFS groups for patients with oral cancer (p = 0.017, p = 0.019, and p = 0.020). Our findings support that PRS could serve as an ideal biomarker for clinical use in risk stratification and progression assessment in oral cancer.

Tribulus terrestris fruit extract inhibits autophagic flux to diminish cell proliferation and metastatic characteristics of oral cancer cells

Elevated autophagy is highly associated with cancer development and progression. Fruit extracts of several plants inhibit activity of autophagy-related protease ATG4B and autophagy activity in colorectal cancer cells. However, the effects of these plant extracts in oral cancer cells remain unclear. In this study, we found that the extracted Tribulus terrestris fruit (TT-(fr)) and Xanthium strumarium fruit had inhibitory effects on autophagy inhibition in both SAS and TW2.6 oral cancer cells. Moreover, the fruit extracts had differential effects on cell proliferation of oral cancer cells. In addition, the fruit extracts hampered cell migration and invasion of oral cancer cells, particularly in TT-(fr) extracts. Our results indicated that TT-(fr) extracts consistently inhibited autophagic flux, cell growth and metastatic characteristics of oral cancer cells, suggesting TT-(fr) might contain function ingredient to suppress oral cancer cells.

Resection Margins in Head and Neck Cancer Surgery: An Update of Residual Disease and Field Cancerization

Surgery is one of the mainstays of head and neck cancer treatment, and aims at radical resection of the tumor with 1 cm tumor-free margins to obtain locoregional control. Surgical margins are evaluated by histopathological examination of the resection specimen. It has been long an enigma that approximately 10-30% of surgically treated head and neck cancer patients develop locoregional recurrences even though the resection margins were microscopically tumor-free. However, the origins of these recurrences have been elucidated by a variety of molecular studies. Recurrences arise either from minimal residual disease, cancer cells in the surgical margins that escape detection by the pathologist when examining the specimen, or from precancerous mucosal changes that may remain unnoticed. Head and neck tumors develop in mucosal precursor changes that are sometimes visible but mostly not, fueling research into imaging modalities such as autofluorescence, to improve visualization. Mostly unnoticed, these precancerous changes may stay behind when the tumor is resected, and subsequent malignant progression will cause a local relapse. This led to a clinical trial of autofluorescence-guided surgery, of which the results were reported in 2020. This review focuses on the most recent literature of the improved diagnosis of the resection margins of surgically treated head and neck cancer patients, the pathobiological origin of recurrent disease, and relevant biomarkers to predict local relapse. Directions for further research will be discussed, including potential options for improved and personalized treatment, based on the most recently published data.

Polo-like Kinase 1 as an emerging drug target: structure, function and therapeutic implications

Polo-like kinase 1 (PLK1) is a conserved mitotic serine-threonine protein kinase, functions as a regulatory protein, and is involved in the progression of the mitotic cycle. It plays important roles in the regulation of cell division, maintenance of genome stability, in spindle assembly, mitosis, and DNA-damage response. PLK1 is consist of a N-terminal serine-threonine kinase domain, and a C-terminal Polo-box domain (regulatory site). The expression of PLK1 is controlled by transcription repressor in the G1 stage and transcription activators in the G2 stage of the cell cycle. Overexpression of PLK1 results in undermining of checkpoints causes excessive cellular division resulting in abnormal cell growth, leading to the development of cancer. Blocking the expression of PLK1 by an antibody, RNA interference, or kinase inhibitors, causes a subsequent reduction in the proliferation of tumour cells and induction of apoptosis in tumour cells without affecting the healthy cells, suggesting an attractive target for drug development. In this review, we discuss detailed information on expression, gene and protein structures, role in different diseases, and progress in the design and development of PLK1 inhibitors. We have performed an in-depth analysis of the PLK1 inhibitors and their therapeutic implications with special focus to the cancer therapeutics.

PLK1 regulates hepatic stellate cell activation and liver fibrosis through Wnt/β-catenin signalling pathway

As an outcome of chronic liver disease, liver fibrosis involves the activation of hepatic stellate cells (HSCs) caused by a variety of chronic liver injuries. It is important to explore approaches to inhibit the activation and proliferation of HSCs for the treatment of liver fibrosis. PLK1 is overexpressed in many human tumour cells and has become a popular drug target in tumour therapy. Therefore, further study of the function of PLK1 in the cell cycle is valid. In the present study, we found that PLK1 expression was elevated in primary HSCs isolated from CCl4 -induced liver fibrosis mice and LX-2 cells stimulated with TGF-β1. Knockdown of PLK1 inhibited α-SMA and Col1α1 expression and reduced the activation of HSCs in CCl4 -induced liver fibrosis mice and LX-2 cells stimulated with TGF-β1. We further showed that inhibiting the expression of PLK1 reduced the proliferation of HSCs and promoted HSCs apoptosis in vivo and in vitro. Furthermore, we found that the Wnt/β-catenin signalling pathway may be essential for PLK1-mediated HSCs activation. Together, blocking PLK1 effectively suppressed liver fibrosis by inhibiting HSC activation, which may provide a new treatment strategy for liver fibrosis.

Association of ATG4B and Phosphorylated ATG4B Proteins with Tumorigenesis and Prognosis in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is one of the major leading causes of cancer death worldwide due to the limited availability of biomarkers and therapeutic targets. Autophagy related protease 4B (ATG4B) is an essential protease for the autophagy machinery, and ATG4B phosphorylation at Ser383/392 increases its proteolytic activity. ATG4B expression and activation are crucial for cancer cell proliferation and invasion. However, the clinical relevance of ATG4B and phospho-Ser383/392-ATG4B for OSCC remains unknown, particularly in buccal mucosal SCC (BMSCC) and tongue SCC (TSCC). With a tissue microarray comprising specimens from 498 OSCC patients, including 179 BMSCC and 249 TSCC patients, we found that the protein levels of ATG4B and phospho-Ser383/392-ATG4B were elevated in the tumor tissues of BMSCC and TSCC compared with those in adjacent normal tissues. High protein levels of ATG4B were significantly associated with worse disease-specific survival (DSS) in OSCC patients, particularly in patients with tumors at advanced stages. In contrast, phospho-Ser383/392-ATG4B expression was correlated with poor disease-free survival (DFS) in TSCC patients. Moreover, ATG4B protein expression was positively correlated with phospho-Ser383/392-ATG4B expression in both BMSCC and TSCC. However, high coexpression levels of ATG4B and phospho-Ser383/392-ATG4B were associated with poor DFS only in TSCC patients, whereas they had no significant association with DSS in BMSCC and TSCC patients. In addition, silencing ATG4B with an antisense oligonucleotide (ASO) or small interfering RNA (siRNA) diminished cell proliferation of TW2.6 and SAS oral cancer cells. Further, knockdown of ATG4B reduced cell migration and invasion of oral cancer cells. Taken together, these findings suggest that ATG4B might be a biomarker for diagnosis/prognosis of OSCC and a potential therapeutic target for OSCC patients.