Atypical function of a centrosomal module in WNT signalling drives contextual cancer cell motility

Elucidating the Functional Mechanism of PTK7 in Cancer Development through Spatial Assembly Analysis Using Super Resolution Imaging

Protein tyrosine kinase-7 (PTK7) has been reported as a vital participant in the Wnt signaling pathway, influencing tumorigenesis and metastasis. However, their specific roles in the mechanisms underlying cancer development and progression remain elusive. Here, using direct stochastic optical reconstruction microscopy (dSTORM) with aptamer-probe labeling, we first revealed that a weakening clustering distribution of PTK7 on the basal membranes happened as cellular migration increased during cancer progression. This correspondence was further supported by a diminished aggregated state of PTK7 caused by direct enhancement of cell migration. By comparing the alterations in PTK7 distribution with activation or inhibition of specific Wnt signaling pathway, we speculated that PTK7 could modulate cell migration by participating in the interplay between canonical Wnt (in MCF7 cells) and noncanonical Wnt signals (in MDA-MB-231 cells). Furthermore, we discovered that the spatial distribution morphology of PTK7 was also subject to the hydrolysis ability and activation state of the related hydrolase Matrix metallopeptidase14 (MMP14). This function-related specific assembly of PTK7 reveals a clear relationship between PTK7 and cancer. Meanwhile, potential molecular interactions predicted by the apparent assembly morphology can promote a deep understanding of the functional mechanism of PTK7 in cancer progress.

Independent prognostic value of CLDN6 in bladder cancer based on M2 macrophages related signature

M2 macrophages are associated with the prognosis of bladder cancer. CLDN6 has been linked to immune infiltration and is crucial for predicting the prognosis in multi-tumor. The effect of CLDN6 on M2 macrophages in bladder cancer remains elusive. Here, we compared a total of 40 machine learning algorithms, then selected optimal algorithm to develop M2 macrophages-related signature (MMRS) based on the identified M2 macrophages related module. MMRS predicted the prognosis better than other models and associated to immunotherapy response. CLDN6, as an important variable in MMRS, was an independent factor for poor prognosis. We found that CLDN6 was highly expressed and affected immune infiltration, immunotherapy response, and M2 macrophages polarization. Meanwhile, CLDN6 promoted the growth of bladder cancer and enhanced the carcinogenic effect by inducing polarization of M2 macrophages. In total, CLDN6 is an independent risk factor in MMRS to predict the prognosis of bladder cancer.

Therapeutic potential of targeting polo-like kinase 4

Polo-like kinase 4 (PLK4), a highly conserved serine/threonine kinase, masterfully regulates centriole duplication in a spatiotemporal manner to ensure the fidelity of centrosome duplication and proper mitosis. Abnormal expression of PLK4 contributes to genomic instability and associates with a poor prognosis in cancer. Inhibition of PLK4 is demonstrated to exhibit significant efficacy against various types of human cancers, further highlighting its potential as a promising therapeutic target for cancer treatment. As such, numerous small-molecule inhibitors with distinct chemical scaffolds targeting PLK4 have been extensively investigated for the treatment of different human cancers, with several undergoing clinical evaluation (e.g., CFI-400945). Here, we review the structure, distribution, and biological functions of PLK4, encapsulate its intricate regulatory mechanisms of expression, and highlighting its multifaceted roles in cancer development and metastasis. Moreover, the recent advancements of PLK4 inhibitors in patent or literature are summarized, and their therapeutic potential as monotherapies or combination therapies with other anticancer agents are also discussed.

Proximity Mapping of Ciliary Proteins by BioID

The primary cilium is a highly conserved microtubule-based organelle present in most vertebrate cell types. Mutations in ciliary protein genes can lead to dysfunctional or absent cilia and are the cause of a large group of heterogeneous diseases known as ciliopathies. ARL13B is a member of the ARF family of regulatory GTPases and is highly enriched on the ciliary membrane. The absence of ARL13B disrupts cilia architecture and mutations have been linked to several diseases; yet there remain major gaps in our understanding of the role that ARL13B plays in primary cilia function. Here, we demonstrate how in cellulo proximity-dependent biotinylation (BioID) can be used to generate a comprehensive protein proximity map of ciliary proteins by performing BioID on N- and C-terminally BirA*-tagged ARL13B. This method can theoretically provide insight into any cilia protein, identifying key interactors that play a critical role in ciliary biology.

Dishevelled segment polarity protein 2 promotes gastric cancer progression through Wnt/β-catenin pathway

Dishevelled family proteins (DVL1-3), key scaffold proteins, act on canonical and non-canonical Wnt/β-catenin signaling pathway. DVL has been implicated in various tumor progression. However, its role and underlying mechanisms in gastric cancer (GC) remain unclear. The aim of this study was to investigate the role of DVL in GC development using cell lines and 209 GC specimens. We analyzed three orthologs of DVL in GC tissues and paired adjacent non-tumor tissues, and only DVL2 is highly expressed in GC tissues. We also analyzed clinicopathological data on DVL2 expression in gastric cancer specimens. In immunohistochemistry, DVL2 expression was up-regulated in GC tissues compared with paired adjacent non-tumor tissues (153/209, 73.2%). DVL2 expression level was significantly correlated with many clinicopathological parameters such as T stage (P < 0.001) and N stage (P < 0.001). Survival analysis showed that the overall survival (OS) of patients with high expression of DVL2 was significantly shorter than those with low expression. Multivariate Cox regression analysis revealed that DVL2 expression was an important and independent prognostic factor for gastric cancer patients (P = 0.011, HR=1.78, 95%CI (1.14-2.79). Depletion of endogenous DVL2 using short hairpin RNA (shRNA) inhibited GC cell proliferation, migration, and invasion. The abnormal activation of Wnt/β-catenin signaling pathway is mainly achieved through the abnormal expression of DVL2. DVL2 is highly expressed in gastric cancer tissues, which may be a new independent risk factor for the prognosis of gastric cancer patients. In gastric cancer, DVL2 overexpression plays a crucial role in the occurrence and development of gastric cancer, so it may become a new, effective and complementary therapeutic target for gastric cancer.

The prognostic value of DAAM2 in lower grade glioma, liver cancer, and breast cancer

PURPOSE

Dishevelled-associated activator of morphogenesis 2 (DAAM2) is a formin protein and has a potential role in the tumor metastasis. The prognostic value of DAAM2 in pan-cancer is investigated in this study.

METHODS

TCGA and GTEx database were downloaded to perform bioinformatics analysis and ROC curves. Then we explored protein-protein interaction and GO-KEGG enrichment to figure out the protein pathways associated with DAAM2 and studied DAAM2-related immune infiltration and methylation. Fifteen pairs of BRCA clinical samples were enrolled to determine the expression and distribution of DAAM2 in BRCA sections by immunohistochemistry. Finally, BRCA cells were transfected with siRNA targeting DAAM2 and subsequently subject to cell proliferation, migration, and invasion assays.

RESULTS

DAAM2 was closely related to the diagnosis and clinical characteristics of lower grade glioma (LGG), liver hepatocellular carcinoma (LIHC), and breast cancer (BRCA). Survival curve analysis demonstrated DAAM2 served as a potential prognostic indicator of LGG and LIHC (P = 0.0029 and P = 0.025, respectively). DAAM2 was mainly participated in signaling pathways mediating cytoskeleton regulation and tumor development. The correlation of DAAM2 with tumor-infiltrating immune cells (TIICs) and methylation levels was conducive to the prediction of novel biomarkers of pan-carcinoma. DAAM2 was highly expressed in BRCA tissues than that in paracancerous tissues. The proliferation, invasion, and migration of BRCA cells were inhibited by DAAM2 siRNA.

CONCLUSION

DAAM2 had a specific value in foretelling the prognosis of LGG, LIHC, and BRCA. High expression level of DAAM2 has longer survival rates in LGG and LIHC. The knockdown of DAAM2 retards the proliferation, invasion, and migration of BRCA cells. This study provides a novel sight of DAAM2 into the exploration of a potential biomarker in pan-cancer.

Moonlighting at the Poles: Non-Canonical Functions of Centrosomes

Centrosomes are best known as the microtubule organizing centers (MTOCs) of eukaryotic cells. In addition to their classic role in chromosome segregation, centrosomes play diverse roles unrelated to their MTOC activity during cell proliferation and quiescence. Metazoan centrosomes and their functional doppelgängers from lower eukaryotes, the spindle pole bodies (SPBs), act as important structural platforms that orchestrate signaling events essential for cell cycle progression, cellular responses to DNA damage, sensory reception and cell homeostasis. Here, we provide a critical overview of the unconventional and often overlooked roles of centrosomes/SPBs in the life cycle of eukaryotic cells.

Lipid-associated macrophages in the tumor-adipose microenvironment facilitate breast cancer progression

The tumor-adipose microenvironment (TAME) is a universal microecosystem, that is characterized by the dysfunction of lipid metabolism, such as excessive free fatty acids (FFAs). Macrophages are the most abundant immune cell type within TAME, although their diversity in the TAME is not clear. We first reveal that infiltration of M2-like macrophages in the TAME is associated with poor survival in breast cancer. To explore lipid-associated alterations in the TAME, we also detected the levels of FFAs transporters including fatty acid binding proteins (FABPs) and fatty acid transport protein 1 (FATP1). The results indicated that expression of fatty acid transporters in the TAME is tightly linked to the function of macrophages and predicts survival in breast cancer. To explore the impact of FFAs transporters on the function of macrophages, we performed single-cell RNA sequencing (scRNA-seq) and spatial transcriptomics. Consequently, we identified a special subpopulation of macrophages defined as lipid-associated macrophages (LAMs), highly expressed macrophage markers (CD163, SPP1 and C1QC), genes involved in lipid metabolism (FABP3, FABP4, FABP5, LPL and LIPA) and some lipid receptors (LGALS3 and TREM2). Functionally, LAMs were characterized by a canonical functional signature of M2-like macrophages, lipid accumulation and enhancing phagocytosis, and they were mostly distributed in tumor-adipose junctional regions. Finally, the allograft cancer mouse models confirmed that LAMs depletion in the TAME synergizes the antitumorigenic effects of anti-PD1 therapy. In summary, we defined a novel subtype of macrophages in the TAME, that has unique features and clinical outcomes.

TEC kinase stabilizes PLK4 to promote liver cancer metastasis

Aberrated PLK4 expression has been reported in different malignancies and causes centrosome amplification, aneuploidy, and genomic instability. However, the mechanism by which PLK4 is regulated in carcinogenesis remains not fully characterised. Here, we showed that PLK4 was overexpressed in human HCC and overexpression of PLK4 predicted poorer patient prognosis. Unexpectedly, we found that induced expression of PLK4 promotes, but knockdown of PLK4 inhibits, HCC cell migration and invasion. Mechanistically, we found that TEC tyrosine kinase, which also promotes HCC cell migration, stabilizes PLK4 by phosphorylation. TEC directly phosphorylates PLK4 at tyrosine 86 residue, which not only stabilizes the protein but also enhances PLK4-mediated HCC cell invasion. Further investigation by transcriptome sequencing indicated that PLK4 promotes the phosphorylation of focal adhesion kinase to regulate the focal adhesion pathway in HCC cell migration. Taken together, our results demonstrated that PLK4 plays an important role in HCC metastasis and revealed for the first time the mechanism by which PLK4 promotes HCC metastasis via TEC phosphorylation.

Modelling the Functions of Polo-Like Kinases in Mice and Their Applications as Cancer Targets with a Special Focus on Ovarian Cancer

Polo-like kinases (PLKs) belong to a five-membered family of highly conserved serine/threonine kinases (PLK1-5) that play differentiated and essential roles as key mitotic kinases and cell cycle regulators and with this in proliferation and cellular growth. Besides, evidence is accumulating for complex and vital non-mitotic functions of PLKs. Dysregulation of PLKs is widely associated with tumorigenesis and by this, PLKs have gained increasing significance as attractive targets in cancer with diagnostic, prognostic and therapeutic potential. PLK1 has proved to have strong clinical relevance as it was found to be over-expressed in different cancer types and linked to poor patient prognosis. Targeting the diverse functions of PLKs (tumor suppressor, oncogenic) are currently at the center of numerous investigations in particular with the inhibition of PLK1 and PLK4, respectively in multiple cancer trials. Functions of PLKs and the effects of their inhibition have been extensively studied in cancer cell culture models but information is rare on how these drugs affect benign tissues and organs. As a step further towards clinical application as cancer targets, mouse models therefore play a central role. Modelling PLK function in animal models, e.g., by gene disruption or by treatment with small molecule PLK inhibitors offers promising possibilities to unveil the biological significance of PLKs in cancer maintenance and progression and give important information on PLKs' applicability as cancer targets. In this review we aim at summarizing the approaches of modelling PLK function in mice so far with a special glimpse on the significance of PLKs in ovarian cancer and of orthotopic cancer models used in this fatal malignancy.

Disheveled-associated activator of morphogenesis 2 promotes invasion of colorectal cancer by activating PAK1 and promoting MMP7 expression

BACKGROUND

Disheveled-associated activator of morphogenesis (DAAM) family, including DAAM1 and DAAM2, is key regulators in Wnt signaling pathway. Although the oncogenic role of Wnt signaling pathway in colorectal cancer (CRC) was investigated in several lines, the expression and function of DAAM in CRC are still obscure.

OBJECTIVE

To investigate the expression and function of DAAM in CRC.

METHODS

DAAM1 and DAAM2 expression in high grade dysplasia (HGD), CRCs and corresponding adjacent tissues were detected with qRT-PCR and immunohistochemistry (IHC). The prognostic significance of DAAM1/2 were estimated with univariate and multivariate analyses. Moreover, the correlations between clinicopathological factors and DAAM were evaluated with the χ² test. With experiments in vitro, we investigated the function of DAAM2 in CRC cell proliferation and invasion, and investigated the underlying mechanism of how DAAM2 facilitated CRC invasion.

RESULTS

DAAM2, instead of DAAM1, was substantially up-regulated in CRCs compared with paired adjacent normal tissues and HGDs. The ratio of high DAAM1 and DAAM2 expression accounted for 44.83% and 46.31%, respectively. High DAAM2, instead of DAAM1, was a risk factor indicating an unfavorable prognosis of CRC. In multivariate analysis, high DAAM2 was identified as an independent prognostic biomarker of CRC predicting poor prognosis. With experiments in vitro, DAAM2 promoted invasion of CRC cells via activating PAK1 and promoting the expression of MMP7, suggesting an essential role of DAAM2 in CRC invasion.

CONCLUSIONS

High expression of DAAM2, instead of DAAM1, indicated an unfavorable prognosis of CRC independently, which suggested that detecting DAAM2 can help define the high-risk patients. DAAM2 activated PAK1 and promoted MMP7 expression and facilitated the invasion of CRC cells, indicating that DAAM2 may be a potential drug target of CRC.

Use of the Polo-like kinase 4 (PLK4) inhibitor centrinone to investigate intracellular signalling networks using SILAC-based phosphoproteomics

Polo-like kinase 4 (PLK4) is the master regulator of centriole duplication in metazoan organisms. Catalytic activity and protein turnover of PLK4 are tightly coupled in human cells, since changes in PLK4 concentration and catalysis have profound effects on centriole duplication and supernumerary centrosomes, which are associated with aneuploidy and cancer. Recently, PLK4 has been targeted with a variety of small molecule kinase inhibitors exemplified by centrinone, which rapidly induces inhibitory effects on PLK4 and leads to on-target centrosome depletion. Despite this, relatively few PLK4 substrates have been identified unequivocally in human cells, and PLK4 signalling outside centriolar networks remains poorly characterised. We report an unbiased mass spectrometry (MS)-based quantitative analysis of cellular protein phosphorylation in stable PLK4-expressing U2OS human cells exposed to centrinone. PLK4 phosphorylation was itself sensitive to brief exposure to the compound, resulting in PLK4 stabilisation. Analysing asynchronous cell populations, we report hundreds of centrinone-regulated cellular phosphoproteins, including centrosomal and cell cycle proteins and a variety of likely 'non-canonical' substrates. Surprisingly, sequence interrogation of ∼300 significantly down-regulated phosphoproteins reveals an extensive network of centrinone-sensitive [Ser/Thr]Pro phosphorylation sequence motifs, which based on our analysis might be either direct or indirect targets of PLK4. In addition, we confirm that NMYC and PTPN12 are PLK4 substrates, both in vitro and in human cells. Our findings suggest that PLK4 catalytic output directly controls the phosphorylation of a diverse set of cellular proteins, including Pro-directed targets that are likely to be important in PLK4-mediated cell signalling.

The actin regulator profilin 1 is functionally associated with the mammalian centrosome

The actin regulator profilin 1 recently shown to control microtubule elongation at the cell periphery is found to interact with the γ-tubulin ring complex and tune centrosomal microtubule nucleation.

Profilin 1 is a crucial actin regulator, interacting with monomeric actin and several actin-binding proteins controlling actin polymerization. Recently, it has become evident that this profilin isoform associates with microtubules via formins and interferes with microtubule elongation at the cell periphery. Recruitment of microtubule-associated profilin upon extensive actin polymerizations, for example, at the cell edge, enhances microtubule growth, indicating that profilin contributes to the coordination of actin and microtubule organization. Here, we provide further evidence for the profilin-microtubule connection by demonstrating that it also functions in centrosomes where it impacts on microtubule nucleation.

Centriole Number and the Accumulation of Microtubules Modulate the Timing of Apical Insertion during Radial Intercalation

Centrioles are microtubule (MT)-based structures that provide important functions during cell migration, cell division, and cell signaling [1]. Modulating centriole number in 3D cell cultures has been shown to influence protrusive behavior [2-5]. Here, we address in vivo the role of centrioles and the accumulation of MTs on the protrusive behavior required during the initiation of radial intercalation. Radial intercalation is an important developmental process whereby cells undergo polarized movements and interdigitate into a more superficial layer [6, 7]. It is commonly employed during metamorphic events, such as the tissue thinning coupled with expansion or during the introduction of different cell types into an epithelium. During radial intercalation, cells emerge from a basal layer by undergoing a process of apical migration, apical insertion, and expansion [8]. In Xenopus skin, multiciliated cells (MCCs), which contain ∼150 centrioles, and ionocytes (ICs), which contain two centrioles, differentiate during the same developmental window, but MCCs complete intercalation prior to ICs. Here, we utilize this difference in timing to create a quantifiable assay for insertion and find that the timing of insertion is modulated by changes in centriole number and the accumulation of acetylated MTs. Additionally, centrioles align between the nucleus and the leading edge creating an axis of migration with apically oriented (+) ends. Using the MT (-) end protein CAMSAP1 fused to the apically positioned Par6 protein, we have artificially reversed the orientation of MTs and find that the accumulation of MTs in either orientation is sufficient to promote apical insertion.

Effect of endostatin on Wnt pathway of stem-like cells in bladder cancer in tumor microenvironment

Wnt/β-catenin signaling pathway modulates miscellaneous biological events in cells including gene expression, cell growth, apoptosis, metabolism and transition. The aim of this study was to investigate the effect of endostatin on Wnt signaling pathway of stem-like cells in bladder cancer in tumor microenvironment. The qRT-PCR assay and western blot were conducted to evaluate related factors expressions of Wnt signaling pathway in both bladder cancer 5637 cells and stem cells. Loss of function assays were carried out to detect the influence of endostatin on the proliferation, migration, cell proliferation and apoptosis of bladder cancer cells. We demonstrated that endostatin triggered the degradation of β-catenin, a key mediator of Wnt signaling. The activation of the endostatin blocked β-catenin function and inhibited cell growth and migration of bladder cancer. In order to verify that the Wnt/β-catenin signaling pathway was inhibited by endostain in 5637 bladder cancer cells and stem cells, the Wnt/β-catenin signaling pathway-associated molecules, including DKK1, LRP5, TCF4, β-catenin, cyclin D1, and c-Myc, were evaluated in 5637 bladder cancer cells and stem cells. The western blotting results showed that expressions of these molecules were remarkably increased in the 5637 bladder cancer cells and stem cells compared to the control group. In summary, our study demonstrated that endostatin inhibited angiogenesis. The downregulation of the Wnt/β-catenin pathway may be engaged in the suppression of angiogenesis by endostatin in bladder cancer cells and cancer stem cells.

Direct interaction between CEP85 and STIL mediates PLK4-driven directed cell migration

PLK4 has emerged as a prime target for cancer therapeutics, and its overexpression is frequently observed in various types of human cancer. Recent studies have further revealed an unexpected oncogenic activity of PLK4 in regulating cancer cell migration and invasion. However, the molecular basis behind the role of PLK4 in these processes still remains only partly understood. Our previous work has demonstrated that an intact CEP85-STIL binding interface is necessary for robust PLK4 activation and centriole duplication. Here, we show that CEP85 and STIL are also required for directional cancer cell migration. Mutational and functional analyses reveal that the interactions between CEP85, STIL and PLK4 are essential for effective directional cell motility. Mechanistically, we show that PLK4 can drive the recruitment of CEP85 and STIL to the leading edge of cells to promote protrusive activity, and that downregulation of CEP85 and STIL leads to a reduction in ARP2 (also known as ACTR2) phosphorylation and reorganization of the actin cytoskeleton, which in turn impairs cell migration. Collectively, our studies provide molecular insight into the important role of the CEP85-STIL complex in modulating PLK4-driven cancer cell migration.This article has an associated First Person interview with the first author of the paper.

Wnt Signaling: Paths for Cancer Progression

The Wnt signaling pathways are well known for having several pivotal roles during embryonic development. However, the same developmental signaling pathways also present key roles in cancer initiation and progression. In this chapter, several issues regarding the roles of both canonical and non-canonical Wnt signaling pathways in cancer will be explored, mainly concerning their role in the maintenance of cancer stemness, in the metabolism reprograming of cancer cells and in the modulation of the tumor microenvironment. The role of Wnt signaling cascades in the response of cancer cells to anti-cancer treatments will be also discussed, as well as its potential therapeutic targeting during cancer treatment. Collectively, increasing evidence has been supporting pivotal roles of Wnt signaling in several features of cancer biology, however; a lot is still to be elucidated.

A cis-eQTL genetic variant in PLK4 confers high risk of hepatocellular carcinoma

Purpose

The overexpression and knockdown of PLK4 were both reported to generate aneuploidy. Thus, we aimed to investigate whether genetic variants in PLK4 contribute to the development of hepatocellular carcinoma (HCC).

Methods

We evaluated associations of common variants in PLK4 and its promoter for the risk of HCC in our association study (1300 cases and 1344 controls). The genotype‐tissue expression (GTEx) and The cancer genome atlas (TCGA) databases were used to quantify the expression of PLK4. Cell proliferation and migration affected by PLK4 in HCC were assessed in vitro. Drug susceptibility testing (DST) model was used to assess the sensibility of PLK4‐activated HCC to CFI‐400945, a small molecule inhibitor of PLK4.

Results

Herein, we found a significant association between rs3811741, located in the PLK4 intron, and liver cancer risk (OR = 1.26, P = 9.81 × 10⁻⁵). Although PLK4 expressed at lower levels in somatic tissues compared to the testis, the risk allele A of rs3811741 was associated with increased PLK4 expression in liver cancer tissues. Additionally, PLK4 high expression was remarkably associated with shortened survival of HCC (HR = 1.97, P = .001). Furthermore, overexpression of PLK4 promoted, while knockdown of PLK4 suppressed cancer cell proliferation, migration, and invasion. DST model demonstrated that CFI‐400945 can effectively suppress rampant proliferation of HCC with highly expressed PLK4.

Conclusion

Taken together, our study demonstrated that PLK4 is a susceptibility gene and plays an oncogenic role in HCC. Furthermore, we identified that PLK4 sensitives HCC to CFI‐400945, which may be an ideal therapy target for HCC.