Phosphorylation of Caldesmon by PFTAIRE1 kinase promotes actin binding and formation of stress fibers

Cytoplasmic Localization Isoform of Cyclin Y Enhanced the Metastatic Ability of Lung Cancer via Regulating Tropomyosin 4

Cyclin Y (CCNY) is a novel cyclin and highly conserved in metazoan species. Previous studies from our and other laboratory indicate that CCNY play a crucial role in tumor progression. There are two CCNY isoform which has different subcellular distributions, with cytoplasmic isoform (CCNYc) and membrane distribution isoform (CCNYm). However, the expression and function of CCNY isoforms is still unclear. We firstly found CCNYc was expressed in natural lung cancer tissue and cells through the subcellular distribution. Co-IP and immunofluorescence showed that both CCNYm and CCNYc could interact with PFTK1. Further studies illustrated that CCNYc but not CCNYm enhanced cell migration and invasion activity both in vivo and vitro. The function of CCNYc could be inhibited by suppression of PFTK1 expression. In addition, our data indicated that tropomyosin 4 (TPM4), a kind of actin-binding proteins, was down-regulated by suppression of CCNY. F-actin assembly could be controlled by CCNYc as well as PFTK1 and TPM4. As a result, CCNY was mainly expressed in lung cancer. CCNYc could promote cell motility and invasion. It indicated that CCNYc/PFTK1 complex could promote cell metastasis by regulating the formation of F-actin via TPM4.

Downregulation of PFTK1 Inhibits Migration and Invasion of Non-Small Cell Lung Cancer

Background

PFTK1, a novel cyclin-dependent kinase, plays pivotal roles in tumorigenesis. Cell motility and invasiveness could be enhanced by PFTK1 in various tumors. However, the function of PFTK1 in NSCLC metastasis remains unclear. In this study, the potential role of PFTK1 in NSCLC metastasis was determined.

Materials and Methods

In this study, the potential function of PFTK1 in lung cancer patients was analyzed with the Kaplan–Meier plotter database. RNA interference-mediated knockdown of PFTK1 was established in two NSCLC cell lines (H1299 and 95C) to explore the role of PFTK1 in NSCLC. The efficacy of downregulation of PFTK1 was examined by Western blot and immunofluorescence. The role of PFTK1 in cell migration and invasion ability was detected by wound healing and transwell assays. The protein levels in lung cancer cells were determined by Western blot. Immunofluorescence analysis was used to evaluate the structure of filamentous actin.

Results

Overexpression of PFTK1 was associated with the poor survival prognosis in NSCLC patients. PFTK1 knockdown cells were constructed successfully. Suppression of PFTK1 significantly inhibited the cell migration and invasion in H1299 and 95C cells. Notably, after PFTK1 downregulation, the epithelial–mesenchymal transition (EMT) markers vimentin, ZEB1 and β-catenin were obviously decreased. Additionally, immunofluorescence analysis indicated that PFTK1 downregulation remarkably induced filamentous actin depolymerization.

Conclusion

In summary, PFTK1 could significantly promote lung cancer metastasis through changing EMT progress and modulating intracellular cytoskeleton F-actin expression. Taken together, our findings indicated that PFTK1 might serve as a novel therapeutic target for the inhibition of NSCLC progression.

Reorganization of the Vimentin Network in Smooth Muscle

Vimentin intermediate filaments (IFs) link to desmosomes (intercellular junctions) on the membrane and dense bodies in the cytoplasm, which provides a structural base for intercellular and intracellular force transmission in smooth muscle. There is evidence to suggest that the vimentin framework plays an important role in mediating smooth muscle mechanical properties such as tension and contractile responses. Contractile activation induces vimentin phosphorylation at Ser-56 and vimentin network reorientation, facilitating contractile force transmission among and within smooth muscle cells. p21-activated kinase 1 and polo-like kinase 1 catalyze vimentin phosphorylation at Ser-56, whereas type 1 protein phosphatase dephosphorylates vimentin at this residue. Vimentin filaments are also involved in other cell functions including migration and nuclear positioning. This review recapitulates our current knowledge how the vimentin network modulates mechanical and biological properties of smooth muscle.

The Dynamic Actin Cytoskeleton in Smooth Muscle

Smooth muscle contraction requires both myosin activation and actin cytoskeletal remodeling. Actin cytoskeletal reorganization facilitates smooth muscle contraction by promoting force transmission between the contractile unit and the extracellular matrix (ECM), and by enhancing intercellular mechanical transduction. Myosin may be viewed to serve as an "engine" for smooth muscle contraction whereas the actin cytoskeleton may function as a "transmission system" in smooth muscle. The actin cytoskeleton in smooth muscle also undergoes restructuring upon activation with growth factors or the ECM, which controls smooth muscle cell proliferation and migration. Abnormal smooth muscle contraction, cell proliferation, and motility contribute to the development of vascular and pulmonary diseases. A number of actin-regulatory proteins including protein kinases have been discovered to orchestrate actin dynamics in smooth muscle. In particular, Abelson tyrosine kinase (c-Abl) is an important molecule that controls actin dynamics, contraction, growth, and motility in smooth muscle. Moreover, c-Abl coordinates the regulation of blood pressure and contributes to the pathogenesis of airway hyperresponsiveness and vascular/airway remodeling in vivo. Thus, c-Abl may be a novel pharmacological target for the development of new therapy to treat smooth muscle diseases such as hypertension and asthma.

The roles and regulation of the actin cytoskeleton, intermediate filaments and microtubules in smooth muscle cell migration

Smooth muscle cell migration has been implicated in the development of respiratory and cardiovascular systems; and airway/vascular remodeling. Cell migration is a polarized cellular process involving a protrusive cell front and a retracting trailing rear. There are three cytoskeletal systems in mammalian cells: the actin cytoskeleton, the intermediate filament network, and microtubules; all of which regulate all or part of the migrated process. The dynamic actin cytoskeleton spatially and temporally regulates protrusion, adhesions, contraction, and retraction from the cell front to the rear. c-Abl tyrosine kinase plays a critical role in regulating actin dynamics and migration of airway smooth muscle cells and nonmuscle cells. Recent studies suggest that intermediate filaments undergo reorganization during migration, which coordinates focal adhesion dynamics, cell contraction, and nucleus rigidity. In particular, vimentin intermediate filaments undergo phosphorylation and reorientation in smooth muscle cells, which may regulate cell contraction and focal adhesion assembly/disassembly. Motile cells are characterized by a front-rear polarization of the microtubule framework, which regulates all essential processes leading to cell migration through its role in cell mechanics, intracellular trafficking, and signaling. This review recapitulates our current knowledge how the three cytoskeletal systems spatially and temporally modulate the migratory properties of cells. We also summarize the potential role of migration-associated biomolecules in lung and vascular diseases.

PFTK1 regulates cell proliferation, migration and invasion in epithelial ovarian cancer

PFTK1, also named Cyclin-Dependent Kinase 14 (CDK14), is a member of the cell division cycle 2 (CDC2)-related protein kinase family. It is a serine/threonine-protein kinase involved in the regulation of cell cycle progression and cell proliferation. In this study, we investigated the role of PFTK1 in epithelial ovarian cancer (EOC) development. The expression of PFTK1 was detected by Western blot and immunohistochemistry staining, both of which demonstrated that PFTK1 was overexpressed in EOC tissues and cells. Statistical analysis showed the expression of PFTK1 was associated with multiple clinicopathological factors, including tumor grade, FIGO stage, lymph node metastatis, Ki-67 expression and predicted a poor prognosis of EOC patients. With in vitro studies we found that PFTK1 expression was decreased in serum-starved ovarian cancer cells, and progressively increased after serum-re-feeding. Knocking PFTK1 down by small interfering RNA (siRNA) significantly inhibited ovarian cancer cell proliferation, migration and invasion. Taken together, our study suggested that PFTK1 played an important role in ovarian cancer development.

PFTK1 Promotes Gastric Cancer Progression by Regulating Proliferation, Migration and Invasion

PFTK1, also known as PFTAIRE1, CDK14, is a novel member of Cdc2-related serine/threonine protein kinases. Recent studies show that PFTK1 is highly expressed in several malignant tumors such as hepatocellular carcinoma, esophageal cancer, breast cancer, and involved in regulation of cell cycle, tumors proliferation, migration, and invasion that further influence the prognosis of tumors. However, the expression and physiological significance of PFTK1 in gastric cancer remain unclear. In this study, we analyzed the expression and clinical significance of PFTK1 by Western blot in 8 paired fresh gastric cancer tissues, nontumorous gastric mucosal tissues and immunohistochemistry on 161 paraffinembedded slices. High PFTK1 expression was correlated with the tumor grade, lymph node invasion as well as Ki-67. Through Cell Counting Kit (CCK)-8 assay, flow cytometry, colony formation, wound healing and transwell assays, the vitro studies demonstrated that PFTK1 overexpression promoted proliferation, migration and invasion of gastric cancer cells, while PFTK1 knockdown led to the opposite results. Our findings for the first time supported that PFTK1 might play an important role in the regulation of gastric cancer proliferation, migration and would provide a novel promising therapeutic strategy against human gastric cancer.

Revelation of fibroblast protein commonalities and differences and their possible roles in wound healing and tumourigenesis using co-culture models of cells

BACKGROUND INFORMATION

The in vitro co-culture models of communication between normal fibroblasts and epithelial cells, such as keratinocytes or squamous cell carcinoma cells of FaDu line representing wound healing or cancer development, were established by non-direct contact between the cells and utilised in this study to examine epithelia-induced changes in overall fibroblast proteome patterns.

RESULTS

We were able to select the proteins co-regulated in both models in order to evaluate possible molecular commonalities between wound healing and tumour development. Amongst the most pronounced were the proteins implemented in contractile activity and formation of actin cytoskeleton such as caldesmon, calponin-2, myosin regulatory light-chain 12A and cofilin-1, which were expressed independently of the presence of α-smooth muscle actin. Additionally, proteins altered differently highlighted functional and cellular phenotypes during transition of fibroblasts towards myofibroblasts or cancer-associated fibroblasts. Results showed coordinated regulation of cytoskeleton proteins selective for wound healing which were lost in tumourigenesis model. Vimentin bridged this group of proteins with other regulated proteins in human fibroblasts involved in protein or RNA processing and metabolic regulation.

CONCLUSIONS

The findings provide strong support for crucial role of stromal microenvironment in wound healing and tumourigenesis. In particular, epithelia-induced protein changes in fibroblasts offer new potential targets which may lead to novel tailored cancer therapeutic strategies.

Quantitative proteomic analysis in HCV-induced HCC reveals sets of proteins with potential significance for racial disparity

Background

The incidence and mortality of hepatitis C virus (HCV)-induced hepatocellular carcinoma (HCC) is higher in African Americans (AA) than other racial/ethnic groups in the U.S., but the reasons for this disparity are unknown. There is an urgent need for the discovery of novel molecular signatures for HCV disease progression to understand the underlying biological basis for this cancer rate disparity to improve the clinical outcome.

Methods

We performed differential proteomics with isobaric labeling tags for relative and absolute quantitation (iTRAQ) and MS/MS analysis to identify proteins differentially expressed in cirrhotic (CIR) and HCC as compared to normal tissues of Caucasian American (CA) patients. The raw data were analyzed using the ProteinPilot v3.0. Searches were performed against all known sequences populating the Swiss-Prot, Refseq, and TrEMBL databases. Quality control analyses were accomplished using pairwise correlation plots, boxplots, principal component analysis, and unsupervised hierarchical clustering. Supervised analysis was carried out to identify differentially expressed proteins. Candidates were validated in independent cohorts of CA and AA tissues by qRT-PCR or Western blotting.

Results

A total of 238 unique proteins were identified. Of those, around 15% were differentially expressed between normal, CIR & HCC groups. Target validation demonstrates racially distinct alteration in the expression of certain proteins. For example, the mRNA expression levels of transferrin (TF) were 2 and18-fold higher in CIR and HCC in AA as compared to CA. Similarly; the expression of Apolipoprotein A1 (APOA1) was 7-fold higher in HCC of AA. This increase was mirrored in the protein expression levels. Interestingly, the level of hepatocyte nuclear factor4α (HNF4α) protein was down regulated in AA, whereas repression of transcription is seen more in CA compared to AA. These data suggest that racial disparities in HCC could be a consequence of differential dysregulation of HNF4α transcriptional activity.

Conclusion

This study identifies novel molecular signatures in HCV-induced HCC using iTRAQ-based tissue proteomics. The proteins identified will further enhance a molecular explanation to the biochemical mechanism(s) that may play a role in HCC racial disparities.

Deregulations in the cyclin-dependent kinase-9-related pathway in cancer: implications for drug discovery and development

The CDK9-related pathway is an important regulator of mammalian cell biology and is also involved in the replication cycle of several viruses, including the human immunodeficiency virus type 1. CDK9 is present in two isoforms termed CDK9-42 and CDK9-55 that bind noncovalently type T cyclins and cyclin K. This association forms a heterodimer, where CDK9 carries the enzymatic site and the cyclin partner functions as a regulatory subunit. This heterodimer is the main component of the positive transcription elongation factor b, which stabilizes RNA elongation via phosphorylation of the RNA pol II carboxyl terminal domain. Abnormal activities in the CDK9-related pathway were observed in human malignancies and cardiac hypertrophies. Thus, the elucidation of the CDK9 pathway deregulations may provide useful insights into the pathogenesis and progression of human malignancies, cardiac hypertrophy, AIDS and other viral-related maladies. These studies may lead to the improvement of kinase inhibitors for the treatment of the previously mentioned pathological conditions. This review describes the CDK9-related pathway deregulations in malignancies and the development of kinase inhibitors in cancer therapy, which can be classified into three categories: antagonists that block the ATP binding site of the catalytic domain, allosteric inhibitors, and small molecules that disrupt protein-protein interactions.

α1 -Adrenergic receptor-induced cytoskeletal organization and cell motility in CCL39 fibroblasts requires phospholipase D1

The role of phospholipase D (PLD) in cytoskeletal reorganization, ERK activation, and migration is well established. Both isoforms of PLD (PLD1 and PLD2) can independently activate stress fiber formation and increase ERK phosphorylation. However, the isoform's specificity, upstream activators, and downstream targets of PLD that coordinate this process are less well understood. This study explores the role of α(1) -adrenergic receptor stimulation and its effect on PLD activity. We demonstrate that PLD1 activators, RhoA, and PKCα are critical for stress fiber formation and ERK activation, and enhance the production of phosphatidic acid (PA) upon phenylephrine addition. Ectopic expression of dominant negative PLD1 and not PLD2 blocks ERK activation, inhibits stress fiber formation, and reduces cell motility in CCL39 fibroblasts. Furthermore, we demonstrate the mechanism for PLD1 activation of ERK involves Ras. This work indicates that PLD1 plays a novel role mediating growth factor and cell motility events in α(1) -adrenergic receptor-activated cells.

Overexpression of PFTK1 predicts resistance to chemotherapy in patients with oesophageal squamous cell carcinoma

Background:

Recently, PFTK1 was identified as a member of the cyclin-dependent kinase family; however, its expression and clinical significance in oesophageal squamous cell carcinoma (ESCC) have not been evaluated.

Methods:

PFTK1 expression was initially examined by expression microarray in 77 ESCC patients. Using independent samples of 223 patients, PFTK1 expression was evaluated immunohistochemically to assess the relationship between expression and various clinicopathological parameters. The association between PFTK1 and the response to chemotherapy was also investigated in pretreatment samples of 85 patients who received chemotherapy as first treatment.

Results:

Significant upregulation of PFTK1 expression was noted in ESCC compared with normal epithelium. PFTK1 expression was positive in 51.6% (115 out of 223) of the tumours, but did not correlate with any clinicopathological parameter. The 5-year overall survival rate was poorer in patients positive for PFTK1 (43.6%) than those with negative expression (66.2%, P<0.001). Uni- and multivariate analyses identified PFTK1 as an independent marker of prognosis (RR=2.428, 95% CI=1.615–3.711, P<0.001). Out of 85 biopsy samples, 40 (47.1%) tumours showed PFTK1-positive expression, and the response rate to chemotherapy was significantly lower than PFTK1-negative tumours (27.9% vs 72.1%, P<0.001).

Conclusion:

PFTK1 is not only useful as a prognostic marker, but also as a predictor of the response to chemotherapy.