PCTAIRE1 phosphorylates p27 and regulates mitosis in cancer cells

CDK16 as a potential prognostic biomarker correlated with an immunosuppressive tumor microenvironment and benefits in enhancing the effectiveness of immunotherapy in human cancers

BACKGROUND

Cyclin-Dependent Kinase 16 (CDK16) plays significant biological roles in various diseases. Nonetheless, its function in different cancer types and its relationship with the Tumor Immune Microenvironment (TIME) are still not well-understood.

METHODS

We analyzed the expression profile, genetic alterations, clinical features, and prognostic value of CDK16 in pan-cancer using data from The Cancer Genome Atlas, Genotype-Tissue Expression databases, and in vitro experiments. Additionally, the TIMER2 and ImmuCellAI databases were utilized to assess the correlation between CDK16 expression and immune cell infiltration levels. Finally, we examined the correlation between CDK16 and the response to immunotherapy using collected immunotherapy data.

RESULTS

CDK16 is notably overexpressed in pan-cancer and is a risk factor for poor prognosis in various cancers. Our findings reveal that CDK16 regulates not only cell cycle-related functions to promote cell proliferation but also the autoimmunity-related functions of the innate and adaptive immune systems, along with other immune-related signaling pathways. Moreover, CDK16 overexpression contributes to an immunosuppressive tumor microenvironment, extensively suppressing immune-related features such as the expression of immune-related genes and pathways, as well as the count of immune-infiltrating cells. Our analysis indicated that individuals with low CDK16 expression showed higher response rates to immune checkpoint inhibitors and longer overall survival compared to those with high CDK16 expression.

CONCLUSIONS

This study establishes CDK16 as a potential biomarker for predicting poor prognosis in a wide range of cancers. Its role in shaping the immunosuppressive tumor microenvironment and influencing the efficacy of immunotherapy highlights the urgent need for developing targeted therapies against CDK16, offering new avenues for cancer treatment and management.

Cyclin-dependent kinases: Masters of the eukaryotic universe

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

Development of o-aminobenzamide salt derivatives for improving water solubility and anti-undifferentiated gastric cancer

Background: Gastric cancer is one of the cancers with wide incidence, difficult treatment and high mortality in the world, especially in Asia and Africa. In our previous work, a novel o-aminobenzamide analogue F8 was identified as an early preclinical candidate for treatment of undifferentiated gastric cancer (IC₅₀ of 0.26 μM for HGC-27). However, the poor water solubility of compound F8 prevents its further progress in preclinical studies. Aim: To improve the water solubility and drug-likeness of F8 via salt formation. Method: Different acids and F8 were reacted to obtain different salt forms. Physicochemical property screening, pharmacokinetic property research, and antitumor biological activity evaluation in vitro and in vivo were used to obtain the optimal salt form with the best druggability. Results: our continuous efforts have finally confirmed F8·2HCl as the optimal salt form with maintained in vitro antitumor activity, improved water solubility and pharmacokinetic properties. Importantly, the F8·2HCl displayed superior in vivo antitumor efficacy (TGI of 70.1% in 75 mg/kg) in HGC-27 xenograft model. The further immunohistochemical analysis revealed that F8·2HCl exerts an antitumor effect through the regulation of cell cycle-related protein (CDK2 and p21), apoptosis-related protein Cleaved Caspase-3, proliferation marker Ki67, and cell adhesion molecule E-cadherin. In addition, F8·2HCl showed acceptable safety in the in vivo acute toxicity assay. Conclusion: Salting is an effective means to improve the drug-like properties of compound F8, and F8·2HCl can serve as a promising therapeutic agent against undifferentiated gastric cancer.

PCTAIRE Protein Kinase 1 (PCTK1) Suppresses Proliferation, Stemness, and Chemoresistance in Colorectal Cancer through the BMPR1B-Smad1/5/8 Signaling Pathway

Colorectal cancer (CRC) is the third most common cancer and a leading cause of cancer-related mortality worldwide. Even with advances in therapy, CRC mortality remains high. Therefore, there is an urgent need to develop effective therapeutics for CRC. PCTAIRE protein kinase 1 (PCTK1) is an atypical member of the cyclin-dependent kinase (CDK) family, and the function of PCTK1 in CRC is poorly understood. In this study, we found that patients with elevated PCTK1 levels had a better overall survival rate in CRC based on the TCGA dataset. Functional analysis also showed that PCTK1 suppressed cancer stemness and cell proliferation by using PCTK1 knockdown (PCTK1-KD) or knockout (PCTK1-KO) and PCTK1 overexpression (PCTK1-over) CRC cell lines. Furthermore, overexpression of PCTK1 decreased xenograft tumor growth and knockout of PCTK1 significantly increased in vivo tumor growth. Moreover, knockout of PCTK1 was observed to increase the resistance of CRC cells to both irinotecan (CPT-11) alone and in combination with 5-fluorouracil (5-FU). Additionally, the fold change of the anti-apoptotic molecules (Bcl-2 and Bcl-xL) and the proapoptotic molecules (Bax, c-PARP, p53, and c-caspase3) was reflected in the chemoresistance of PCTK1-KO CRC cells. PCTK1 signaling in the regulation of cancer progression and chemoresponse was analyzed using RNA sequencing and gene set enrichment analysis (GSEA). Furthermore, PCTK1 and Bone Morphogenetic Protein Receptor Type 1B (BMPR1B) in CRC tumors were negatively correlated in CRC patients from the Timer2.0 and cBioPortal database. We also found that BMPR1B was negatively correlated with PCTK1 in CRC cells, and BMPR1B expression was upregulated in PCTK1-KO cells and xenograft tumor tissues. Finally, BMPR1B-KD partially reversed cell proliferation, cancer stemness, and chemoresistance in PCTK1-KO cells. Moreover, the nuclear translocation of Smad1/5/8, a downstream molecule of BMPR1B, was increased in PCTK1-KO cells. Pharmacological inhibition of Smad1/5/8 also suppressed the malignant progression of CRC. Taken together, our results indicated that PCTK1 suppresses proliferation and cancer stemness and increases the chemoresponse of CRC through the BMPR1B-Smad1/5/8 signaling pathway.

Eribulin inhibits growth of cutaneous squamous cell carcinoma cell lines and a novel patient-derived xenograft

Advanced cutaneous squamous cell carcinoma (cSCC) is treated with chemotherapy and/or radiotherapy, but these typically fail to achieve satisfactory clinical outcomes. There have been no preclinical studies to evaluate the effectiveness of eribulin against cSCC. Here, we examine the effects of eribulin using cSCC cell lines and a novel cSCC patient-derived xenograft (PDX) model. In the cSCC cell lines (A431 and DJM-1 cells), eribulin was found to inhibit tumor cell proliferation in vitro as assessed by cell ATP levels. DNA content analysis by fluorescence-activated cell sorting (FACS) showed that eribulin induced G2/M cell cycle arrest and apoptosis. In xenograft models of cSCC cell lines, the administration of eribulin suppressed tumor growth in vivo. We also developed a cSCC patient-derived xenograft (PDX) which reproduces the histological and genetic characteristics of a primary tumor. Pathogenic mutations in TP53 and ARID2 were detected in the patient's metastatic tumor and in the PDX tumor. The cSCC-PDX responded well to the administration of eribulin and cisplatin. In conclusion, the present study shows the promising antineoplastic effects of eribulin in cSCC. Also, we established a novel cSCC-PDX model that preserves the patient's tumor. This PDX could assist researchers who are exploring innovative therapies for cSCC.

The roles, molecular interactions, and therapeutic value of CDK16 in human cancers

Cyclin-dependent kinase 16 (CDK16) is an orphan "cyclin-dependent kinase" (CDK) involved in the cell cycle, vesicle trafficking, spindle orientation, skeletal myogenesis, neurite outgrowth, secretory cargo transport, spermatogenesis, glucose transportation, cell apoptosis, cell growth and proliferation, metastasis, and autophagy. Human CDK16 is located on chromosome Xp11.3 and is related to X-linked congenital diseases. CDK16 is commonly expressed in mammalian tissues and may act as an oncoprotein. It is a PCTAIRE kinase in which Cyclin Y or its homologue, Cyclin Y-like 1, regulates activity by binding to the N- and C- terminal regions of CDK16. CDK16 plays a vital role in various cancers, including lung cancer, prostate cancer, breast cancer, malignant melanoma, and hepatocellular carcinoma. CDK16 is a promising biomarker for cancer diagnosis and prognosis. In this review, we summarized and discussed the roles and mechanisms of CDK16 in human cancers.

Baicalin Blocks Colon Cancer Cell Cycle and Inhibits Cell Proliferation through miR-139-3p Upregulation by Targeting CDK16

Baicalin was reported to facilitate the apoptosis of colon cells and inhibit tumor growth in vivo. This study aimed to explore the specific mechanism and function of baicalin on colon cells. Relative mRNA levels were tested via qPCR. Cell proliferation, viability, and cell cycle phases were evaluated using MTT, colony formation, and flow cytometry assays, respectively. The interaction between miR-139-3p and cyclin-dependent kinase 16 (CDK16) was measured via a dual-luciferase reporter assay. Immunohistochemistry was used to count the positivity cells in tumor tissues collected from treated xenografted tumor mice. The results showed that baicalin increased miR-139-3p expression while also decreasing CDK16 levels, blocking the cell cycle, and inhibiting cell proliferation in colon cancer cells. miR-139-3p silencing or CDK16 overexpression abolished the inhibitory effects of baicalin on colon cancer proliferation. miR-139-3p directly targeted and interacted with CDK16 at the cellular level. The protective functions of miR-139-3p knockdown on tumor cells were abrogated by silencing CDK16. The combination of baicalin treatment and CDK16 knockdown further inhibited tumor growth of xenografted tumor mice compared with the groups injected with only sh-CDK16 or baicalin in vivo. In conclusion, baicalin inhibited colon cancer growth by modulating the miR-139-3p/CDK16 axis.

PCTAIRE1 promotes mitotic progression and resistance against antimitotic and apoptotic signals

PCTAIRE1 (also known as CDK16) is a serine-threonine kinase implicated in physiological processes like neuronal development, vesicle trafficking, spermatogenesis and cell proliferation. However, its exact role in cell division remains unclear. In this study, using a library screening approach, we identified PCTAIRE1 among several candidates that resisted mitotic arrest and mitotic cell death induced by polyomavirus small T (PolST) expression in mammalian cells. Our study showed that PCTAIRE1 is a mitotic kinase that localizes at centrosomes during G2 and at spindle poles as the cells enter mitosis, and then at the midbody during cytokinesis. We also report that PCTAIRE1 protein levels fluctuate through the cell cycle and reach their peak at mitosis, during which there is an increase in PCTAIRE1 phosphorylation as well. Interestingly, knockdown of PCTAIRE1 resulted in aberrant mitosis by interfering with spindle assembly and chromosome segregation. Further, we found that PCTAIRE1 promotes resistance of cancer cells to antimitotic drugs, and this underscores the significance of PCTAIRE1 as a potential drug target for overcoming chemotherapeutic resistance. Taken together, these studies establish PCTAIRE1 as a critical mediator of mitotic progression and highlight its role in chemotherapeutic resistance. This article has an associated First Person interview with the first author of the paper.

CDK15 promotes colorectal cancer progression via phosphorylating PAK4 and regulating β-catenin/ MEK-ERK signaling pathway

Colorectal cancer (CRC) is the third most diagnosed cancer and the second leading cause of cancer-related deaths. However, there are few effective therapeutic targets for CRC patients. Here, we found that CDK15 was highly expressed in human CRC and negatively correlated with patient prognosis and overall survival in tissue microarray. Knockdown of CDK15 suppressed cell proliferation and anchorage-independent growth of CRC cells and inhibited tumor growth in cell line-derived xenograft (CDX) model. Importantly, knockout of CDK15 in mice retarded AOM/DSS-induced tumorigenesis and CDK15 silencing by lentivirus significantly suppressed tumor progression in patient-derived xenograft (PDX) model. Mechanistically, CDK15 could bind PAK4 and phosphorylate PAK4 at S291 site. Phosphorylation of PAK4 at the S291 residue promoted cell proliferation and anchorage-independent growth through β-catenin/c-Myc, MEK/ERK signaling pathway in CRC. Moreover, inhibition of PAK4 reversed the tumorigenic function of CDK15 in CRC cells and pharmacological targeting PAK4 suppressed tumor growth in PDX models. Thus, our data reveal the pivotal role of CDK15 in CRC progression and demonstrate CDK15 promotes CRC tumorigenesis by phosphorylating PAK4. Hence, the CDK15-PAK4 axis may serve as a novel therapeutic target for CRC.

Monoclonal antibodies to activated CDK4: use to investigate normal and cancerous cell cycle regulation and involvement of phosphorylations of p21 and p27

Cyclin-dependent kinase 4 (CDK4) is a master integrator that couples mitogenic/oncogenic signaling with the cell division cycle. It is deregulated in most cancers and inhibitors of CDK4 have become standard of care drugs for metastatic estrogen-receptor positive breast cancers and are being evaluated in a variety of other cancers. We previously characterized the T-loop phosphorylation at T172 of CDK4 as the highly regulated step that determines the activity of cyclin D-CDK4 complexes. Moreover we demonstrated that the highly variable detection of T172-phosphorylated CDK4 signals the presence or absence of the active CDK4 targeted by the CDK4/6 inhibitory drugs, which predicts the tumor cell sensitivity to these drugs including palbociclib. To date, the phosphorylation of CDK4 has been very poorly studied because only few biochemical techniques and reagents are available for it. In addition, the available ones including 2D-IEF separation of CDK4 modified forms are considered too tedious. The present report describes the generation, selection and characterization of the first monoclonal antibodies that specifically recognize the active CDK4 phosphorylated on its T172 residue. One key to this success was the immunization with a long phosphopeptide corresponding to the complete activation segment of CDK4. These monoclonal antibodies specifically recognize T172-phosphorylated CDK4 in a variety of assays, including western blotting, immunoprecipitation and, as a capture antibody, a sensitive ELISA from cell lysates. The specific immunoprecipitation of T172-phosphorylated CDK4 allowed to clarify the involvement of phosphorylations of co-immunoprecipitated p21 and p27, showing a privileged interaction of T172-phosphorylated CDK4 with S130-phosphorylated p21 and S10-phosphorylated p27.

Abbreviations: 2D: two-dimensional; CAK: CDK-activating kinase; CDK: cyclin-dependent kinase; HAT: Hypoxanthine-Aminopterin-Thymidine; FBS: fetal bovine serum; IP: immunoprecipitation; ID: immunodetection; mAb: monoclonal antibody; PAGE: polyacrylamide gel electrophoresis; PBS: phosphate buffer saline; pRb: retinoblastoma susceptibility protein; SDS: sodium dodecyl sulfate; DTT: dithiotreitol; TET: tetracyclin repressor; Avi: Avi tag; TEV: tobacco etch virus cleavage site; EGFP: enhanced green fluorescent protein; BirA: bifunctional protein biotin ligase BirA; IRES: internal ribosome entry site; HIS: poly-HIS purification tag; DELFIA: dissociation-enhanced lanthanide fluorescent immunoassay; 3-MBPP1: 1-(1,1-dimethylethyl)-3[(3-methylphenyl) methyl]-1H-pyrazolo[3,4-d] pyrimidin-4-amine; BSA: bovine serum albumin; ECL: Enhanced chemiluminescence

Cyclin-dependent kinase 4/6 inhibitors suppress tumor growth in extramammary Paget's disease

Extramammary Paget's disease (EMPD) is a rare adnexal neoplasm commonly seen in the genital areas among the senior population. The prognosis of advanced EMPD is not favorable; thus, the development of potential treatments has long been sought. Cyclin-dependent kinase (CDK) 4/6 inhibitors such as abemaciclib and palbociclib have been proven effective against metastatic breast cancer; however, no studies have addressed CDK4/6 inhibitors as an EMPD treatment. We herein examine the efficacy of CDK4/6 inhibitors against an EMPD patient-derived xenograft (PDX) model. Abemaciclib (50 mg/kg/day) or palbociclib (120 mg/kg/day) was given orally to tumor-bearing NOD/Scid mice over a 3-week period. We also investigated the protein expression levels of CDK4/6 and cyclin D1 through immunohistochemical staining using EMPD clinical samples. Treatment with abemaciclib or palbociclib as a single agent was found to significantly suppress tumor growth in EMPD-PDX. The Ki-67-positive ratio of the treated EMPD-PDX tumors was significantly lower than that of the nontreated tumors. Clinically, the expression levels of CDK4 and cyclin D1 were significantly higher in the EMPD tumor cells than in the normal epidermis. Our results suggest that CDK4/6 inhibitors could be novel and potent therapeutics for the treatment of EMPD.

Lung cancer cells expressing a shortened CDK16 3'UTR escape senescence through impaired miR-485-5p targeting

Inducing senescence in cancer cells is an emerging strategy for cancer therapy. The dysregulation and mutation of genes encoding cyclin‐dependent kinases (CDKs) have been implicated in various human cancers. However, whether CDK can induce cancer cell senescence remains poorly understood. We observed that CDK16 expression was high in multiple cancer types, including lung cancer, whereas various replicative senescence models displayed low CDK16 expression. CDK16 knockdown caused senescence‐associated phenotypes in lung cancer cell lines. Interestingly, the CDK16 3′ UTR was shortened in cancer and lengthened in senescence models, which was regulated by alternative polyadenylation (APA). The longer 3′UTR [using the distal polyA (pA) site] generated less protein than the shorter one (using the proximal pA site). Since microRNAs (miRNAs) usually bind to the 3′UTR of target genes to suppress their expression, we investigated whether miRNAs targeting the region between the shortened and longer 3′UTR are responsible for the reduced expression. We found that miR‐485‐5p targeted the 3′UTR between the distal and proximal pA site and caused senescence‐associated phenotypes by reducing protein production from the longer CDK16 transcript. Of note, CDK16 knockdown led to a reduced expression of MYC proto‐oncogene, bHLH transcription factor (MYC) and CD274 molecule (PD‐L1), which in turn enhanced the tumor‐suppressive effects of senescent cancer cells. The present study discovered that CDK16, whose expression is under the regulation of APA and miR‐485‐5p, is a potential target for prosenescence therapy for lung cancer.

Stimulation of phospholipase Cβ1 by Gαq promotes the assembly of stress granule proteins

[Figure: see text].

Loss of FAM83H promotes cell migration and invasion in cutaneous squamous cell carcinoma via impaired keratin distribution

BACKGROUNDS

FAM83H is essential for amelogenesis, but recent reports implicate that FAM83H is involved in the tumorigenesis. We previously clarified that TRIM29 binds to FAM83H to regulate keratin distribution and squamous cell migration. However, little is known about FAM83H in normal/malignant skin keratinocytes.

OBJECTIVE

To investigate the expression of FAM83H in cutaneous squamous cell carcinoma (SCC) and its physiological function.

METHODS

Immunohistochemical analysis and RT-PCR of human SCC tissues were performed. Next, we examined the effect of FAM83H knockdown/overexpression in SCC cell lines using cell proliferation, migration, and invasion assay. To investigate the molecular mechanism, immunoprecipitation of FAM83H was examined. Further, Immunofluorescence staining was performed. Finally, we examined the correlation between the expressions of FAM83H and the keratin distribution.

RESULTS

FAM83H expression was lower in SCC lesions than in normal epidermis and correlated with differentiation grade. The mRNA expression levels of FAM83H in SCC tumors were also lower than in normal epidermis. The knockdown of FAM83H enhanced SCC cell migration and invasion, whereas the overexpression of FAM83H led to decreases in both. Furthermore, the knockdown of FAM83H enhanced the cancer cell metastasis in vivo. FAM83H formed a complex with TRIM29 and keratins. The knockdown of FAM83H altered keratin distribution and solubility. Clinically, the loss of FAM83H correlates with an altered keratin distribution.

CONCLUSION

Our findings reveal a critical function for FAM83H in regulating keratin distribution, as well as in the migration/invasion of cutaneous SCC, suggesting that FAM83H could be a crucial molecule in the tumorigenesis of cutaneous SCC.

Regulation of PCTAIRE1 protein stability by AKT1, LKB1 and BRCA1

PCTAIRE1, also known as CDK16, is a cyclin-dependent kinase that is regulated by cyclin Y. It is a member of the serine-threonine family of kinases and its functions have primarily been implicated in cellular processes like vesicular transport, neuronal growth and development, myogenesis, spermatogenesis and cell proliferation. However, as extensive studies on PCTAIRE1 have not yet been conducted, the signaling pathways for this kinase involved in governing many cellular processes are yet to be elucidated in detail. Here, we report the association of PCTAIRE1 with important cellular proteins involved in major cell signaling pathways, especially cell proliferation. In particular, here we show that PCTAIRE1 interacts with AKT1, a key player of the PI3K signaling pathway that is responsible for promoting cell survival and proliferation. Our studies show that PCTAIRE1 is a substrate of AKT1 that gets stabilized by it. Further, we show that PCTAIRE1 also interacts with and is degraded by LKB1, a kinase that is known to suppress cellular proliferation and also regulate cellular energy metabolism. Moreover, our results show that PCTAIRE1 is also degraded by BRCA1, a well-known tumor suppressor. Together, our studies highlight the regulation of PCTAIRE1 by key players of the major cell signaling pathways involved in regulating cell proliferation, and therefore, provide crucial links that could be explored further to elucidate the mechanistic role of PCTAIRE1 in cell proliferation and tumorigenesis.

Vandetanib inhibits cell growth in EGFR-expressing cutaneous squamous cell carcinoma

Advanced cutaneous squamous cell carcinoma (SCC) responds poorly to chemotherapy, leading to significant morbidity or death. Overexpression of epidermal growth factor receptor (EGFR) is frequently observed in advanced cutaneous SCC. Vandetanib is a multiple tyrosine kinase targeting vascular endothelial growth factor receptor-2 (VEGFR2), EGFR, and the rearranged during transfection (RET) proto-oncogene. Vandetanib has been reported to inhibit tumor growth in head and neck SCC. However, the efficacy of vandetanib against cutaneous SCC has not been thoroughly investigated. The aim of this study is to evaluate the efficacy of vandetanib against cutaneous SCC in vitro and in vivo. Vandetanib is found to inhibit the proliferation of cutaneous SCC cells as assessed by cell viability and clonogenic assay. Cell death analysis indicates that vandetanib induces cell death in SCC cells but not in normal human keratinocytes or fibroblasts. The in vivo anti-tumor effect of vandetanib is shown in xenograft tumor models using A431 SCC cells. Mechanistically, vandetanib suppresses the phosphorylation of EGFR in SCC cells. Clinically, EGFR expression levels are elevated in cutaneous SCC specimens, relative to normal epidermis. In conclusion, we identified vandetanib as a novel therapeutic option for cutaneous SCC, especially in tumors with high EGFR expression.

Extramammary Paget's disease patient-derived xenografts harboring ERBB2 S310F mutation show sensitivity to HER2-targeted therapies

Although the prognosis of advanced extramammary Paget's disease (EMPD) is poor, there have been no preclinical research models for the development of novel therapeutics. This study aims to establish a preclinical research model for EMPD. We transplanted EMPD tissue into immunodeficient NOD/Scid mice. Histopathological and genetic analyses using a comprehensive cancer panel were performed. For in vivo preclinical treatments, trastuzumab, lapatinib, docetaxel, or eribulin were administered to patient-derived xenograft (PDX) models. Tissue transplanted from the EMPD patient was enlarged in NOD/Scid mice and was transplanted into further generations. Both the transplantation of PDX into nu/nu mice and the reanimation of the cryopreserved xenografted tumors in NOD/Scid mice were successful. We also established an EMPD-PDX-derived primary cell culture. Histopathologically, the xenografted tumors were positive for CK7, which was consistent with the patient's tumors. Genetically, the pathogenic mutation ERBB2 S310F was detected in the patient's tumors (primary intraepidermal lesion, metastatic lymph node) and was observed in the xenografted tumors even after continued passages. The xenografted tumors responded well to trastuzumab and lapatinib therapy. Also, cytotoxic agents (docetaxel and eribulin) were effective against the xenografted tumors. This PDX model (EMPD-PDX-H1) could be a powerful tool for the research and development of EMPD treatments.

Loss of dynamin-related protein 1 (Drp1) does not affect epidermal development or UVB-induced apoptosis but does accelerate UVB-induced carcinogenesis

BACKGROUND

Mitochondrial morphology is controlled by fission and fusion. Dynamin-related protein 1 (Drp1, dynamin-1-like protein (Dnml1)) regulates mitochondrial fission, which is associated with cell division and apoptosis. We previously reported that DRP1 is indispensable for cell growth in cutaneous squamous cell carcinoma. However, little is known about Drp1 in normal epidermis/keratinocytes.

OBJECTIVES

We investigated the function of Drp1 in normal epidermis/keratinocytes.

METHODS

Epidermis-specific Drp1 knockout (EKO) mice were analyzed.

RESULTS

Epidermal development in the EKO mice were indistinguishable from those in the wild-type (WT) mice. Ultrastructural analysis and immunohistochemistry revealed that the mitochondria of keratinocytes in the EKO mice were neither elongated nor constricted. Drp1 knockdown did not diminish the cell growth of normal human keratinocytes. Both in vivo and in vitro, UVB-induced apoptosis in the EKO epidermis and keratinocytes did not differ from that in the WT mice. In chronic UVB-irradiation, the loss of Drp1 sensitized the epidermis to the development of skin tumors. Clinically, DRP1 is expressed more highly in sun-exposed skin than in non-exposed skin in individuals under age 40, but not in those over age 60.

CONCLUSION

EKO mice demonstrate that Drp1 is dispensable for the development and apoptosis of the epidermis. Drp1 plays critical roles in malignant tumors; thus, the molecular machinery of mitochondrial dynamics involving Drp1 could be a novel therapeutic target for malignant keratinocytic lesions. On the other hand, the anti-tumorigenic role of Drp1 in chronic UVB-induced carcinogenesis need to be further investigated.

Transcriptomic Analysis in Liquid Biopsy Identifies Circulating PCTAIRE-1 mRNA as a Biomarker in NSCLC

BACKGROUND/AIM

Circulating mRNA can be a useful source of cancer biomarkers. We took advantage of direct transcriptomic analysis in plasma RNA to identify novel mRNA markers for non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

Plasma RNA from NSCLC patients and healthy individuals was profiled with cDNA-mediated annealing, selection, extension and ligation (DASL) microarrays. The microarray results were further validated in plasma RNA.

RESULTS

Through RNA profiling and online database mining, four gene transcripts were filtered as candidate markers of NSCLC. After validation, the PCTAIRE-1 transcript was identified as a circulating mRNA marker. The diagnostic potential of PCTAIRE-1 was evaluated by receiver operating characteristic curve analysis, which gave a sensitivity and specificity of 60% and 85%, respectively. In addition, high plasma PCTK1 levels were also correlated with poor progression-free survival (p=0.008).

CONCLUSION

Circulating mRNA can be profiled with the DASL assay. From the profile, PCTAIRE-1 RNA in the plasma we discovered as a novel diagnostic/prognostic biomarker and an indicator of poor survival in NSCLC patients.

AMPK-dependent activation of the Cyclin Y/CDK16 complex controls autophagy

The AMP-activated protein kinase (AMPK) is a master sensor of the cellular energy status that is crucial for the adaptive response to limited energy availability. AMPK is implicated in the regulation of many cellular processes, including autophagy. However, the precise mechanisms by which AMPK controls these processes and the identities of relevant substrates are not fully understood. Using protein microarrays, we identify Cyclin Y as an AMPK substrate that is phosphorylated at Serine 326 (S326) both in vitro and in cells. Phosphorylation of Cyclin Y at S326 promotes its interaction with the Cyclin-dependent kinase 16 (CDK16), thereby stimulating its catalytic activity. When expressed in cells, Cyclin Y/CDK16 is sufficient to promote autophagy. Moreover, Cyclin Y/CDK16 is necessary for efficient AMPK-dependent activation of autophagy. This functional interaction is mediated by AMPK phosphorylating S326 of Cyclin Y. Collectively, we define Cyclin Y/CDK16 as downstream effector of AMPK for inducing autophagy.

The role of phospholipase Cβ on the plasma membrane and in the cytosol: How modular domains enable novel functions

Phospholipase Cβ (PLCβ) is a signaling enzyme activated by G proteins to generate calcium signals. The catalytic core of PLCβ is surrounded by modular domains that mediate the interaction of the enzyme with known protein partners on the plasma membrane. The C-terminal region PLCβ contains a novel coiled-coil domain that is required for Gαq binding and activation. Recent work has shown that this domain also binds a number of cytosolic proteins that regulate protein translation, and that these proteins compete with Gαq for PLCβ binding. The ability of PLCβ to shuttle between the cytosol to impact protein translation and the plasma membrane to mediate calcium signals puts PLCβ in a central role in cell function.

Phosphoregulation of the oncogenic protein regulator of cytokinesis 1 (PRC1) by the atypical CDK16/CCNY complex

CDK16 (also known as PCTAIRE1 or PCTK1) is an atypical member of the cyclin-dependent kinase (CDK) family that forms an active complex with cyclin Y (CCNY). Although both proteins have been recently implicated in cancer pathogenesis, it is still unclear how the CDK16/CCNY complex exerts its biological activity. To understand the CDK16/CCNY network, we used complementary proteomic approaches to identify potential substrates of this complex. We identified several candidates implicating the CDK16/CCNY complex in cytoskeletal dynamics, and we focused on the microtubule-associated protein regulator of cytokinesis (PRC1), an essential protein for cell division that organizes antiparallel microtubules and whose deregulation may drive genomic instability in cancer. Using analog-sensitive (AS) CDK16 generated by CRISPR-Cas9 mutagenesis in 293T cells, we found that specific inhibition of CDK16 induces PRC1 dephosphorylation at Thr481 and delocalization to the nucleus during interphase. The observation that CDK16 inhibition and PRC1 downregulation exhibit epistatic effects on cell viability confirms that these proteins can act through a single pathway. In conclusion, we identified PRC1 as the first substrate of the CDK16/CCNY complex and demonstrated that the proliferative function of CDK16 is mediated by PRC1 phosphorylation. As CDK16 is emerging as a critical node in cancer, our study reveals novel potential therapeutic targets.

Studying the activity of proteins that work together to control cell division is revealing several that might be suitable targets for new drugs to fight cancer. Researchers led by Josep Clotet and Mariana Ribeiro at the International University of Catalonia, Barcelona, Spain, investigated the activities of the complex formed between two proteins, CDK16 and CCNY. CDK16 is an enzyme that modifies other molecules by adding phosphate groups (PO₄) to them. CCNY is a protein that controls the activity of CDK16 and other proteins. Previous research has suggested a role for the complex in the development of cancer, but the mechanism has been unclear. The researchers found that the CDK16/CCNY complex activates proteins that control the network of microtubules in cells known as the cytoskeleton. One of these proteins, PRC1, is essential for cell division.

Identification of novel PCTAIRE-1/CDK16 substrates using a chemical genetic screen

PCTAIRE-1 (also known as cyclin-dependent protein kinase (CDK) 16), is a Ser/Thr kinase that has been implicated in many cellular processes, including cell cycle, spermatogenesis, neurite outgrowth, and vesicle trafficking. Most recently, it has been proposed as a novel X-linked intellectual disability (XLID) gene, where loss-of-function mutations have been identified in human patients. The precise molecular mechanisms that regulate PCTAIRE-1 remained largely obscure, and only a few cellular targets/substrates have been proposed with no clear functional significance. We and others recently showed that cyclin Y binds and activates PCTAIRE-1 via phosphorylation and 14-3-3 binding. In order to understand the physiological role that PCTAIRE-1 plays in brain, we have performed a chemical genetic screen in vitro using an engineered PCTAIRE-1/cyclin Y complex and mouse brain extracts. Our screen has identified potential PCTAIRE-1 substrates (AP2-Associated Kinase 1 (AAK1), dynamin 1, and synaptojanin 1) in brain that have been shown to regulate crucial steps of receptor endocytosis, and are involved in control of neuronal synaptic transmission. Furthermore, mass spectrometry and protein sequence analyses have identified potential PCTAIRE-1 regulated phosphorylation sites on AAK1 and we validated their PCTAIRE-1 dependence in a cellular study and/or brain tissue lysates. Our results shed light onto the missing link between PCTAIRE-1 regulation and proposed physiological functions, and provide a basis upon which to further study PCTAIRE-1 function in vivo and its potential role in neuronal/brain disorders.

Loss of TRIM29 Alters Keratin Distribution to Promote Cell Invasion in Squamous Cell Carcinoma

: TRIM29 (tripartite motif-containing protein 29) is a TRIM family protein that has been implicated in breast, colorectal, and pancreatic cancers. However, its role in stratified squamous epithelial cells and tumors has not been elucidated. Here, we investigate the expression of TRIM29 in cutaneous head and neck squamous cell carcinomas (SCC) and its functions in the tumorigenesis of such cancers. TRIM29 expression was lower in malignant SCC lesions than in adjacent normal epithelial tissue or benign tumors. Lower expression of TRIM29 was associated with higher SCC invasiveness. Primary tumors of cutaneous SCC showed aberrant hypermethylation of TRIM29. Depletion of TRIM29 increased cancer cell migration and invasion; conversely, overexpression of TRIM29 suppressed these. Comprehensive proteomics and immunoprecipitation analyses identified keratins and keratin-interacting protein FAM83H as TRIM29 interactors. Knockdown of TRIM29 led to ectopic keratin localization of keratinocytes. In primary tumors, lower TRIM29 expression correlated with the altered expression of keratins. Our findings reveal an unexpected role for TRIM29 in regulating the distribution of keratins, as well as in the migration and invasion of SCC. They also suggest that the TRIM29-keratin axis could serve as a diagnostic and prognostic marker in stratified epithelial tumors and may provide a target for SCC therapeutics. SIGNIFICANCE: These findings identify TRIM29 as a novel diagnostic and prognostic marker in stratified epithelial tissues.

Novel Therapeutic Targets in Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (SCC) is one of the common cancers in Caucasians, accounting for 20–30% of cutaneous malignancies. The risk of metastasis is low in most patients; however, aggressive SCC is associated with very high mortality and morbidity. Although cutaneous SCC can be treated with surgical removal, radiation and chemotherapy singly or in combination, the prognosis of patients with metastatic SCC is poor. Recently, the usage of immune checkpoint blockades has come under consideration. To develop effective therapies that are less toxic than existing ones, it is crucial to achieve a detailed characterization of the molecular mechanisms that are involved in cutaneous SCC pathogenesis and to identify new drug targets. Recent studies have identified novel molecules that are associated with SCC carcinogenesis and progression. This review focuses on recent advances in molecular studies involving SCC tumor development, as well as in new therapeutics that have become available to clinicians.

CDK16 Phosphorylates and Degrades p53 to Promote Radioresistance and Predicts Prognosis in Lung Cancer

Rationale: Radioresistance is considered the main cause of local relapse in lung cancer. However, the molecular mechanisms of radioresistance remain poorly understood. This study investigates the role of CDK16 in radioresistance of human lung cancer cells.

Methods: The expression levels of CDK16 were determined by immunohistochemistry in lung cancer tissues and adjacent normal lung tissues. Immunoprecipitation assay and GST pulldown were utilized to detect the protein-protein interaction. The phosphorylation of p53 was evaluated by in vitro kinase assay. Poly-ubiquitination of p53 was examined by in vivo ubiquitination assay. Cell growth and apoptosis, ROS levels and DNA damage response were measured for functional analyses.

Results: We showed that CDK16 is frequently overexpressed in lung cancer cells and tissues, and high levels of CDK16 are correlated with lymph node stage and poor prognosis in lung cancer patients. Furthermore, we provided evidence that CDK16 binds to and phosphorylates p53 at Ser315 site to inhibit transcriptional activity of p53. Moreover, we uncovered that this phosphorylation modification accelerates p53 degradation via the ubiquitin/proteasome pathway. Importantly, we demonstrated that CDK16 promotes radioresistance by suppressing apoptosis and ROS production as well as inhibiting DNA damage response in lung cancer cells in a p53-dependent manner.

Conclusion: Our findings suggest that CDK16 negatively modulates p53 signaling pathway to promote radioresistance, and therefore represents a promising therapeutic target for lung cancer radiotherapy.

miR-129-3p controls centrosome number in metastatic prostate cancer cells by repressing CP110

The centrosome plays a key role in cancer invasion and metastasis. However, it is unclear how abnormal centrosome numbers are regulated when prostate cancer (PCa) cells become metastatic. CP110 was previously described for its contribution of centrosome amplification (CA) and early development of aggressive cell behaviour. However its regulation in metastatic cells remains unclear. Here we identified miR-129-3p as a novel metastatic microRNA. CP110 was identified as its target protein. In PCa cells that have metastatic capacity, CP110 expression was repressed by miR-129-3p. High miR-129-3p expression levels increased cell invasion, while increasing CP110 levels decreased cell invasion. Overexpression of CP110 in metastatic PCa cells resulted in a decrease in the number of metastasis. In tissues of PCa patients, low CP110 and high miR-129-3p expression levels correlated with metastasis, but not with the expression of genes related to EMT. Furthermore, overexpression of CP110 in metastatic PCa cells resulted in excessive-CA (E-CA), and a change in F-actin distribution which is in agreement with their reduced metastatic capacity. Our data demonstrate that miR-129-3p functions as a CA gatekeeper in metastatic PCa cells by maintaining pro-metastatic centrosome amplification (CA) and preventing anti-metastatic E-CA.

Dabrafenib inhibits the growth of BRAF-WT cancers through CDK16 and NEK9 inhibition

Although the BRAF inhibitors dabrafenib and vemurafenib have both proven successful against BRAF-mutant melanoma, there seem to be differences in their mechanisms of action. Here, we show that dabrafenib is more effective at inhibiting the growth of NRAS-mutant and KRAS-mutant cancer cell lines than vemurafenib. Using mass spectrometry-based chemical proteomics, we identified NEK9 and CDK16 as unique targets of dabrafenib. Both NEK9 and CDK16 were highly expressed in specimens of advanced melanoma, with high expression of both proteins correlating with a worse overall survival. A role for NEK9 in the growth of NRAS- and KRAS-mutant cell lines was suggested by siRNA studies in which silencing was associated with decreased proliferation, cell cycle arrest associated with increased p21 expression, inhibition of phospho-CHK1, decreased CDK4 expression, and the initiation of a senescence response. Inhibition of CDK4 but not CHK1 recapitulated the effects of NEK9 silencing, indicating this to be the likely mechanism of growth inhibition. We next turned our attention to CDK16 and found that its knockdown inhibited the phosphorylation of the Rb protein at S780 and increased expression of p27. Both of these effects were phenocopied in NRAS- and KRAS-mutant cancer cells by dabrafenib, but not vemurafenib. Combined silencing of NEK9 and CDK16 was associated with enhanced inhibition of melanoma cell proliferation. In summary, we have identified dabrafenib as a potent inhibitor of NEK9 and CDK16, and our studies suggest that inhibition of these kinases may have activity against cancers that do not harbor BRAF mutations.

Drp1 regulates mitochondrial morphology and cell proliferation in cutaneous squamous cell carcinoma

BACKGROUND

Dynamin-related protein 1 (Drp1) mediates mitochondrial fission. Recently, several studies have shown that Drp1 plays an important role in some cancers. However, little is known about Drp1 in cutaneous squamous cell carcinoma (SCC).

OBJECTIVE

To investigate the role of Drp1 in the tumorigenesis of cutaneous SCCs.

METHODS AND RESULTS

We investigated cell proliferation, cell cycle, mitochondrial morphology, and MAPK signaling pathway using cutaneous SCC A431 and DJM1 cells that were transfected with shRNA vectors targeting Drp1. The Drp1 gene-knockdown SCC cells showed lower cell proliferation than scramble-control cells, as assessed by direct cell counting and clonogenic assays. DNA content analysis showed Drp1 knockdown to cause G2/M arrest. Morphologically, the depletion of Drp1 resulted in an elongated, hyper-fused mitochondrial network. The MEK inhibitor PD325901 suppressed cell proliferation, as well as inhibiting the phosphorylation of ERK^1/2 and Drp1^Ser616. Also, PD325901 caused the dysregulation of the mitochondrial network. In tumor xenografts of DJM1 cells, the knockdown of Drp1 suppressed tumor growth in vivo, and clinically, the expression levels of Drp1 were higher in cutaneous SCCs than in normal epidermis, and correlated positively with the advanced clinical stages.

CONCLUSION

Our results reveal a crucial function for Drp1 in regulating tumor growth, mitochondrial morphology, and cell cycle in cutaneous SCC, suggesting that Drp1 could be a novel target for skin tumor therapies.

Melanoma antigen A12 regulates cell cycle via tumor suppressor p21 expression

Melanoma-associated antigen family A (MAGE-A) is a family of cancer/testis antigens that are expressed in malignant tumors but not in normal tissues other than the testes. MAGE-A12 is a MAGE-A family gene whose tumorigenic function in cancer cells remains unclear. Searches of the Oncomine and NextBio databases revealed that malignant tumors show up-regulation of MAGE-A12 mRNA relative to corresponding normal tissue. In PPC1 primary prostatic carcinoma cells and in HCT116 colorectal cancer cells (wild type and p53-depleted), MAGE-A12 gene knockdown using siRNA or shRNA diminishes cancer cell proliferation as assessed by cellular ATP levels, cell counting, and clonogenic assays. FACS analyses of annexin V-PI staining and DNA content show that MAGE-A12 knockdown causes G2/M arrest and apoptosis. In tumor xenografts of HCT116 cells, conditional knockdown of MAGE-A12 suppresses tumor growth. The depletion of MAGE-A12 leads to the accumulation of tumor suppressor p21 in PPC1, HCT116, and p53-depleted HCT116 cells. Conversely, CDKN1A knockdown partially rescues the viability of PPC1 cells transfected with siRNA targeting MAGE-A12, while p21 overexpression leads to proliferation arrest in PPC-1 cells. Furthermore, exogenous MAGE-A12 expression promotes the ubiquitination of p21. Our findings reveal that MAGE-A12 plays crucial roles in p21 stability and tumor growth, suggesting that MAGE-A12 could provide a novel target for cancer treatment.

Role of downregulated miR-133a-3p expression in bladder cancer: a bioinformatics study

It has been discovered that miR-133a-3p acts as a tumor suppressor in bladder cancer (BC). Nevertheless, the function of miR-133a-3p in BC remains unclarified. Thus, we carried out this study to validate the expression of miR-133a-3p in BC and provide insights into the molecular mechanism underlying it. To assess the expression of miR-133a-3p in BC, we searched eligible studies from literature and Gene expression Omnibus (GEO) to perform a meta-analysis. We also plotted the summary receiver operating characteristic (SROC) curve to evaluate the diagnostic ability of miR-133a-3p in BC. Additionally, the potential target genes of miR-133a-3p were acquired from 14 online software programs and GEO database. Protein-protein interaction (PPI) network was created to identify the hub genes. Then, Gene Ontology (GO) functional annotation analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were carried out to investigate the regulatory network of the target genes. From the meta-analysis, miR-133a-3p was remarkably downregulated in BC tissues compared with that in non-cancer tissues (standard mean difference =−3.84, 95% confidence interval =−6.99–0.29). Moreover, results from SROC suggested that miR-133a-3p exhibited the ability to diagnose BC (area under curve =0.8418). As for the bioinformatics study, 488 genes were chosen as the potential targets of miR-133a-3p in BC, among which 10 genes were defined as hub genes (all degrees >5). Further GO and KEGG pathway analysis indicated that the target genes of miR-133a-3p aggregated in specific biological process and pathways. In conclusion, miR-133a-3p possessed great diagnostic potential with its downregulation in BC, and miR-133a-3p might serve as a novel biomarker for BC.

Up-regulation of CDK16 by multiple mechanisms in hepatocellular carcinoma promotes tumor progression

Background

Hepatocellular carcinoma (HCC) remains difficult to cure due to lack of effective treatment and the molecular mechanisms are complex and not completely understood. In this study, We investigated the role of CDK16 in tumor progression of HCC.

Methods

We interrogated the expression level of CDK16 by polymerase chain reaction and immunohistochemistry(IHC) and studied its clinical significance. The functional role of CDK16 on HCC was studied via gain and loss of function in vitro and in vivo. Luciferase reporter assay and Chromatin immunoprecipitation(ChIP) assay were performed to investigate the transcriptional and post-transcriptional mechanisms involved in the regulation of CDK16.

Results

CDK16 expression was significantly up-regulated in HCC and higher expression of CDK16 was positively correlated with aggressive clinicopathological phenotype and poorer survival rates. Functionally, knockdown of CDK16 suppressed proliferation in vitro and in vivo. Inactivation of CDK16 also induced apoptosis and cell cycle arrest. Most importantly, CDK16 promoted epithelial mesenchymal transition and tumor invasion by activating β-catenin signaling. In addition, We identified E2F1 as a positive transcriptional regulator of CDK16. Moreover, down regulation of miR-125b-5p enhanced CDK16 expression at post-transcriptional level.

Conclusion

We provided the first evidence that CDK16 is an bona fide oncogene in HCC, and multiple activating mechanisms at transcriptional and posttranscriptional levels together contributes to CDK16 up-regulation in HCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0569-2) contains supplementary material, which is available to authorized users.

Targeting Cyclin-Dependent Kinases in Ovarian Cancer

Ovarian cancer is the most common gynecological malignancy in the United States, and prognosis is generally poor because the disease is often diagnosed at an advanced stage. Cyclin-dependent kinases (CDKs) are a family of serine/threonine kinases whose activity is regulated by CDK inhibitors (CKIs) and cyclins. Generally, cyclins and CKIs promote and inhibit CDK activation, respectively. Since cancer commonly involves dysregulation of cell cycle, cyclins and CDKs have been targeted in a variety of tumors using small molecules, peptides, immunotherapy, and CKIs. In this review we discuss the significance of cell cycle dysregulation in ovarian cancer as well as recent advances targeting CDKs in ovarian cancer and potential future directions. Although many of the studies assessing CDK-targeting therapies in ovarian cancer are at an early preclinical stage, there is significant evidence that targeting CDKs, particularly in combination with traditional platinum-based drugs, could have significant efficacy in ovarian cancer. Nevertheless, before these agents can be investigated in humans, additional preclinical development is needed, including using in vivo tumor models and additional studies into their mechanism of action.

Structure and inhibitor specificity of the PCTAIRE-family kinase CDK16

CDK16 (also known as PCTAIRE1 or PCTK1) is an atypical member of the cyclin-dependent kinase (CDK) family that has emerged as a key regulator of neurite outgrowth, vesicle trafficking and cancer cell proliferation. CDK16 is activated through binding to cyclin Y via a phosphorylation-dependent 14-3-3 interaction and has a unique consensus substrate phosphorylation motif compared with conventional CDKs. To elucidate the structure and inhibitor-binding properties of this atypical CDK, we screened the CDK16 kinase domain against different inhibitor libraries and determined the co-structures of identified hits. We discovered that the ATP-binding pocket of CDK16 can accommodate both type I and type II kinase inhibitors. The most potent CDK16 inhibitors revealed by cell-free and cell-based assays were the multitargeted cancer drugs dabrafenib and rebastinib. An inactive DFG-out binding conformation was confirmed by the first crystal structures of CDK16 in separate complexes with the inhibitors indirubin E804 and rebastinib, respectively. The structures revealed considerable conformational plasticity, suggesting that the isolated CDK16 kinase domain was relatively unstable in the absence of a cyclin partner. The unusual structural features and chemical scaffolds identified here hold promise for the development of more selective CDK16 inhibitors and provide opportunity to better characterise the role of CDK16 and its related CDK family members in various physiological and pathological contexts.

Lipid Nanoparticle-mediated siRNA Transfer Against PCTAIRE1/PCTK1/Cdk16 Inhibits In Vivo Cancer Growth

PCTAIRE1/CDK16/PCTK1 plays critical roles in cancer cell proliferation and antiapoptosis. To advance our previously published in vitro results with PCTAIRE1 silencing, we examined the in vivo therapeutic potential of this approach by using small interfering RNA (siRNA) encapsulated by lipid nanoparticles. Therapy experiments of PCTAIRE1 siRNA were performed using human HCT116 colorectal cancer cells and human A2058 melanoma cells. A single dose of PCTAIRE1 siRNA-lipid nanoparticles was found to be highly effective in reducing in vivo PCTAIRE1 expression for up to 4 days as assayed by immunoblotting. Therapy experiments were started 4 days after subcutaneous injection of cancer cells. Treatment with PCTAIRE1 siRNA-lipid nanoparticles (0.5 mg/kg RNA, twice a week) reduced tumor volume and weight significantly compared with the scramble-control group. Histopathological analysis (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) showed increased apoptosis of tumor cells treated with PCTAIRE1-siRNA. Overall, our results demonstrate that siRNA treatment targeting PCTAIRE1 is effective in vivo, suggesting that PCTAIRE1 siRNA-lipid nanoparticles might be a novel therapeutic approach against cancer cells.

miR-33a is downregulated in melanoma cells and modulates cell proliferation by targeting PCTAIRE1

MicroRNA-33a (miR-33a) was previously identified as a lipid regulator that controls the cellular balance between cholesterol and fatty acid metabolism. However, its role in tumor progression is largely unknown. The present study identified that miR-33a acts as a tumor suppressor in melanoma cells. The present study revealed that miR-33a was downregulated in melanoma cells compared with melanocytes. Overexpression of miR-33a suppressed the colony formation of human melanoma SK-MEL-1 and WM-115 cells. Furthermore, a bromodeoxyuridine incorporation assay and anaphase analysis revealed that miR-33a inhibits melanoma cell proliferation. miR-33a overexpression inhibited p27 phosphorylation and upregulated p27 expression. Additionally, the present study demonstrated that PCTAIRE1 was a direct target of miR-33a; miR-33a overexpression suppressed the luciferase activity of a reporter construct containing a 3′-untranslated region of PCTAIRE1 and downregulated PCTAIRE1 in melanoma cells. An overexpression of PCTAIRE1 reversed the miR-33a-induced p27 accumulation and tumor suppressive effects. In summary, the present findings offer novel mechanistic insights into miR-33a and its downstream target in melanoma cells.

Proteomic Analysis of the Mammalian Katanin Family of Microtubule-severing Enzymes Defines Katanin p80 subunit B-like 1 (KATNBL1) as a Regulator of Mammalian Katanin Microtubule-severing

The Katanin family of microtubule-severing enzymes is critical for remodeling microtubule-based structures that influence cell division, motility, morphogenesis and signaling. Katanin is composed of a catalytic p60 subunit (A subunit, KATNA1) and a regulatory p80 subunit (B subunit, KATNB1). The mammalian genome also encodes two additional A-like subunits (KATNAL1 and KATNAL2) and one additional B-like subunit (KATNBL1) that have remained poorly characterized. To better understand the factors and mechanisms controlling mammalian microtubule-severing, we have taken a mass proteomic approach to define the protein interaction module for each mammalian Katanin subunit and to generate the mammalian Katanin family interaction network (Katan-ome). Further, we have analyzed the function of the KATNBL1 subunit and determined that it associates with KATNA1 and KATNAL1, it localizes to the spindle poles only during mitosis and it regulates Katanin A subunit microtubule-severing activity in vitro. Interestingly, during interphase, KATNBL1 is sequestered in the nucleus through an N-terminal nuclear localization signal. Finally KATNB1 was able to compete the interaction of KATNBL1 with KATNA1 and KATNAL1. These data indicate that KATNBL1 functions as a regulator of Katanin A subunit microtubule-severing activity during mitosis and that it likely coordinates with KATNB1 to perform this function.

PCTAIRE1-knockdown sensitizes cancer cells to TNF family cytokines

While PCTAIRE1/PCTK1/Cdk16 is overexpressed in malignant cells and is crucial in tumorigenesis, its function in apoptosis remains unclear. Here we investigated the role of PCTAIRE1 in apoptosis, especially in the extrinsic cell death pathway. Gene-knockdown of PCTAIRE1 sensitized prostate cancer PPC1 and Du145 cells, and breast cancer MDA-MB-468 cells to TNF-family cytokines, including TNF-related apoptosis-inducing ligand (TRAIL). Meanwhile, PCTAIRE1-knockdown did not sensitize non-malignant cells, including diploid fibroblasts IMR-90 and the immortalized prostate epithelial cell line 267B1. PCTAIRE1-knockdown did not up-regulate death receptor expression on the cell surface or affect caspase-8, FADD and FLIP expression levels. PCTAIRE1-knockdown did promote caspase-8 cleavage and RIPK1 degradation, while RIPK1 mRNA knockdown sensitized PPC1 cells to TNF-family cytokines. Furthermore, the kinase inhibitor SNS-032, which inhibits PCTAIRE1 kinase activity, sensitized PPC1 cells to TRAIL-induced apoptosis. Together these results suggest that PCTAIRE1 contributes to the resistance of cancer cell lines to apoptosis induced by TNF-family cytokines, which implies that PCTAIRE1 inhibitors could have synergistic effects with TNF-family cytokines for cytodestruction of cancer cells.

RNA interference screening identifies a novel role for PCTK1/CDK16 in medulloblastoma with c-Myc amplification

Medulloblastoma (MB) is the most common malignant brain tumor in children and is associated with a poor outcome. cMYC amplification characterizes a subgroup of MB with very poor prognosis. However, there exist so far no targeted therapies for the subgroup of MB with cMYC amplification. Here we used kinome-wide RNA interference screening to identify novel kinases that may be targeted to inhibit the proliferation of c-Myc-overexpressing MB. The RNAi screen identified a set of 5 genes that could be targeted to selectively impair the proliferation of c-Myc-overexpressing MB cell lines: AKAP12 (A-kinase anchor protein), CSNK1α1 (casein kinase 1, alpha 1), EPHA7 (EPH receptor A7) and PCTK1 (PCTAIRE protein kinase 1). When using RNAi and a pharmacological inhibitor selective for PCTK1, we could show that this kinase plays a crucial role in the proliferation of MB cell lines and the activation of the mammalian target of rapamycin (mTOR) pathway. In addition, pharmacological PCTK1 inhibition reduced the expression levels of c-Myc. Finally, targeting PCTK1 selectively impaired the tumor growth of c-Myc-overexpressing MB cells in vivo. Together our data uncover a novel and crucial role for PCTK1 in the proliferation and survival of MB characterized by cMYC amplification.

PCTAIRE1 regulates p27 stability, apoptosis and tumor growth in malignant melanoma

PCTAIRE1 is a cyclin-dependent kinase family protein that has been implicated in spermatogenesis. Although we recently revealed the function of PCTAIRE1 in tumorigenesis of epithelial carcinoma cells, its tumorigenic function in melanoma remains unclear. Interrogation of the Oncomine database revealed that malignant melanoma showed up-regulation of PCTAIRE1 mRNA compared to normal skin and benign melanocytic nevus tissues. In the melanoma cell lines A2058 and SK-MEL-28, PCTAIRE1 gene knockdown using siRNA or shRNA diminished melanoma cell proliferation as assessed by cellular ATP levels, cell counting and clonogenic assays. Moreover, FACS analyses of annexin V-PI staining and DNA content showed that PCTAIRE1 knockdown caused apoptosis in A2058 cells. In contrast, PCTAIRE1 does not appear to be involved in the proliferation of immortalized human keratinocyte HaCaT cells. Depletion of PCTAIRE1 by siRNA/shRNA led to p27 accumulation in melanoma cells but not HaCaT cells. In tumor xenografts of melanoma A2058 cells, conditional knockdown of PCTAIRE1 restored p27 protein expression and suppressed tumor growth. Our findings reveal a crucial role for PCTAIRE1 in regulating p27 protein levels and tumor growth in melanoma cells, suggesting that PCTAIRE1 could provide a target for melanoma treatment.