Microtubule affinity-regulating kinase 2 is associated with DNA damage response and cisplatin resistance in non-small cell lung cancer

Role of MARK2 in the nervous system and cancer

Microtubule-Affinity Regulating Kinase 2 (MARK2), a member of the serine/threonine protein kinase family, phosphorylates microtubule-associated proteins, playing a crucial role in cancer and neurodegenerative diseases. This kinase regulates multiple signaling pathways, including the WNT, PI3K/AKT/mTOR (PAM), and NF-κB pathways, potentially linking it to cancer and the nervous system. As a crucial regulator of the PI3K/AKT/mTOR pathway, the loss of MARK2 inhibits the growth and metastasis of cancer cells. MARK2 is involved in the excessive phosphorylation of tau, thus influencing neurodegeneration. Therefore, MARK2 emerges as a promising drug target for the treatment of cancer and neurodegenerative diseases. Despite its significance, the development of inhibitors for MARK2 remains limited. In this review, we aim to present detailed information on the structural features of MARK2 and its role in various signaling pathways associated with cancer and neurodegenerative diseases. Additionally, we further characterize the therapeutic potential of MARK2 in neurodegenerative diseases and cancer, and hope to facilitate basic research on MARK2 and the development of inhibitors targeting MARK2.

Molecular mechanisms underlying the regulation of tumour suppressor genes in lung cancer

Tumour suppressor genes play a cardinal role in the development of a large array of human cancers, including lung cancer, which is one of the most frequently diagnosed cancers worldwide. Therefore, extensive studies have been committed to deciphering the underlying mechanisms of alterations of tumour suppressor genes in governing tumourigenesis, as well as resistance to cancer therapies. In spite of the encouraging clinical outcomes demonstrated by lung cancer patients on initial treatment, the subsequent unresponsiveness to first-line treatments manifested by virtually all the patients is inherently a contentious issue. In light of the aforementioned concerns, this review compiles the current knowledge on the molecular mechanisms of some of the tumour suppressor genes implicated in lung cancer that are either frequently mutated and/or are located on the chromosomal arms having high LOH rates (1p, 3p, 9p, 10q, 13q, and 17p). Our study identifies specific genomic loci prone to LOH, revealing a recurrent pattern in lung cancer cases. These loci, including 3p14.2 (FHIT), 9p21.3 (p16INK4a), 10q23 (PTEN), 17p13 (TP53), exhibit a higher susceptibility to LOH due to environmental factors such as exposure to DNA-damaging agents (carcinogens in cigarette smoke) and genetic factors such as chromosomal instability, genetic mutations, DNA replication errors, and genetic predisposition. Furthermore, this review summarizes the current treatment landscape and advancements for lung cancers, including the challenges and endeavours to overcome it. This review envisages inspired researchers to embark on a journey of discovery to add to the list of what was known in hopes of prompting the development of effective therapeutic strategies for lung cancer.

Anaplastic Kaposi Sarcoma: A Clinicopathologic and Molecular Genetic Analysis

Kaposi sarcoma (KS) is a human herpesvirus 8 (HHV8)-associated vascular proliferation that most often involves the skin. Rarely, KS shows marked nuclear atypia or pleomorphism; such examples are known as "anaplastic" KS. This poorly characterized variant often pursues an aggressive course; little is known of its genetic landscape. This study evaluated the clinicopathologic and genomic features of anaplastic KS. We identified 9 anaplastic KS cases from 7 patients and 8 conventional KS cases, including a matched conventional KS and primary metastasis anaplastic KS pair from a single patient (anaplastic KS diagnosed 9 years after conventional KS). All patients with anaplastic KS were men, aged 51 to 82 years, who had locally aggressive tumors predominantly affecting the soft tissue and bone of the lower extremities (5/7 patients). Four patients were known to be HIV positive (all on antiretrovirals), 2 were HIV negative, and 1 was of unknown HIV status. The tumors showed angiosarcoma-like or pleomorphic spindle cell sarcoma morphology. Plasma cell-rich chronic inflammation and hemosiderin deposition were commonly present. Single-nucleotide polymorphism-based chromosomal microarray analysis showed the anaplastic KS cohort to demonstrate highly recurrent whole chromosome (chr) gains of chr 7, 11, 19, and 21, which primarily affected olfactory and G protein-coupled receptor signaling and losses of chr6_q and chrY. Compared with conventional KS, anaplastic KS cases showed significantly more total copy number alterations and more frequent gains of chr7 and chr11_q13.1 (MARK2, RELA, and ESRRA, including high copy number gain in 1 case). Pathway analysis demonstrated that these gains preferentially affected genes that facilitate cyclin-dependent cell signaling. Furthermore, anaplastic KS cases were phylogenetically distinct from conventional KS cases, including the patient-matched primary metastasis anaplastic KS pair and conventional KS. Our study is the first to demonstrate that a more complex genome and distinct copy number alterations distinguish anaplastic KS from conventional KS. Gains of chr7 and chr11_q13.1 appear central to biological transformation.

Proteogenomic Markers of Chemotherapy Resistance and Response in Triple-Negative Breast Cancer

Microscaled proteogenomics was deployed to probe the molecular basis for differential response to neoadjuvant carboplatin and docetaxel combination chemotherapy for triple-negative breast cancer (TNBC). Proteomic analyses of pretreatment patient biopsies uniquely revealed metabolic pathways, including oxidative phosphorylation, adipogenesis, and fatty acid metabolism, that were associated with resistance. Both proteomics and transcriptomics revealed that sensitivity was marked by elevation of DNA repair, E2F targets, G2-M checkpoint, interferon-gamma signaling, and immune-checkpoint components. Proteogenomic analyses of somatic copy-number aberrations identified a resistance-associated 19q13.31-33 deletion where LIG1, POLD1, and XRCC1 are located. In orthogonal datasets, LIG1 (DNA ligase I) gene deletion and/or low mRNA expression levels were associated with lack of pathologic complete response, higher chromosomal instability index (CIN), and poor prognosis in TNBC, as well as carboplatin-selective resistance in TNBC preclinical models. Hemizygous loss of LIG1 was also associated with higher CIN and poor prognosis in other cancer types, demonstrating broader clinical implications.

SIGNIFICANCE

Proteogenomic analysis of triple-negative breast tumors revealed a complex landscape of chemotherapy response associations, including a 19q13.31-33 somatic deletion encoding genes serving lagging-strand DNA synthesis (LIG1, POLD1, and XRCC1), that correlate with lack of pathologic response, carboplatin-selective resistance, and, in pan-cancer studies, poor prognosis and CIN. This article is highlighted in the In This Issue feature, p. 2483.

Integrated proteomics and phosphoproteomics revealed druggable kinases in neoadjuvant chemotherapy resistant tongue cancer

Tongue squamous cell carcinoma is an aggressive oral cancer with a high incidence of metastasis and poor prognosis. Most of the oral cavity cancer patients present in clinics with locally advanced unresectable tumors. Neoadjuvant treatment is beneficial for these individuals as it reduces the tumor size aiding complete resection. However, patients develop therapy resistance to the drug regimen. In this study, we explored the differential expression of proteins and altered phosphorylation in the neoadjuvant chemotherapy resistant tongue cancer patients. We integrated the proteomic and phosphoproteomic profiles of resistant (n = 4) and sensitive cohorts (n = 4) and demonstrated the differential expression and phosphorylation of proteins in the primary tissue of the respective subject groups. We observed differential and extensive phosphorylation of keratins such as KRT10 and KRT1 between the two cohorts. Furthermore, our study revealed a kinase signature associated with neoadjuvant chemotherapy resistance. Kinases such as MAPK1, AKT1, and MAPK3 are predicted to regulate the resistance in non-responders. Pathway analysis showed enrichment of Rho GTPase signaling and hyperphosphosphorylation of proteins involved in cell motility, invasion, and drug resistance. Targeting the kinases could help with the clinical management of neoadjuvant chemotherapy-resistant tongue cancer.

MARK2 regulates chemotherapeutic responses through class IIa HDAC-YAP axis in pancreatic cancer

Despite paclitaxel's wide use in cancer treatment, patient response rate is still low and drug resistance is a major clinical obstacle. Through a Phos-tag-based kinome-wide screen, we identified MARK2 as a critical regulator for paclitaxel chemosensitivity in PDAC. We show that MARK2 is phosphorylated by CDK1 in response to antitubulin chemotherapeutics and in unperturbed mitosis. Phosphorylation is essential for MARK2 in regulating mitotic progression and paclitaxel cytotoxicity in PDAC cells. Mechanistically, our findings also suggest that MARK2 controls paclitaxel chemosensitivity by regulating class IIa HDACs. MARK2 directly phosphorylates HDAC4 specifically during antitubulin treatment. Phosphorylated HDAC4 promotes YAP activation and controls expression of YAP target genes induced by paclitaxel. Importantly, combination of HDAC inhibition and paclitaxel overcomes chemoresistance in organoid culture and preclinical PDAC animal models. The expression levels of MARK2, HDACs, and YAP are upregulated and positively correlated in PDAC patients. Inhibition of MARK2 or class IIa HDACs potentiates paclitaxel cytotoxicity by inducing mitotic abnormalities in PDAC cells. Together, our findings identify the MARK2-HDAC axis as a druggable target for overcoming chemoresistance in PDAC.

Kinase Activity of PAR1b, Which Mediates Nuclear Translocation of the BRCA1 Tumor Suppressor, Is Potentiated by Nucleic Acid-Mediated PAR1b Multimerization

PAR1b is a cytoplasmic serine/threonine kinase that controls cell polarity and cell-cell interaction by regulating microtubule stability while mediating cytoplasmic-to-nuclear translocation of BRCA1. PAR1b is also a cellular target of the CagA protein of Helicobacter pylori, which leads to chronic infection causatively associated with the development of gastric cancer. The CagA-PAR1b interaction inactivates the kinase activity of PAR1b and thereby dampens PAR1b-mediated BRCA1 phosphorylation, which reduces the level of nuclear BRCA1 and thereby leads to BRCAness and BRCAness-associated genome instability underlying gastric carcinogenesis. While PAR1b can multimerize within the cells, little is known about the mechanism and functional role of PAR1b multimerization. We found in the present study that PAR1b was multimerized in vitro by binding with nucleic acids (both single- and double-stranded DNA/RNA) via the spacer region in a manner independent of nucleic-acid sequences, which markedly potentiated the kinase activity of PAR1b. Consistent with these in vitro observations, cytoplasmic introduction of double-stranded DNA or expression of single-stranded RNA increased the PAR1b kinase activity in the cells. These findings indicate that the cytoplasmic DNA/RNA contribute to nuclear accumulation of BRCA1 by constitutively activating/potentiating cytoplasmic PAR1b kinase activity, which is subverted in gastric epithelial cells upon delivery of H. pylori CagA oncoprotein.

MARK2 potentiate aerobic glycolysis-mediated cell growth in breast cancer through regulating mTOR/HIF-1α and p53 pathways

The microtubule-affinity regulating kinases (MARKs) family plays a crucial role in regulating breast cancer development and progression. However, its precise function and the relevant molecular mechanism in breast cancer have not yet been elucidated. In this study, analysis of The Cancer Genome Atlas (TCGA) data revealed that MARK2 expression was markedly upregulated in breast cancer tissues, and high expression of MARK2 was correlated with poor survival. Functional assays showed that MARK2 deletion or inhibition suppressed aerobic glycolysis and cell growth as well as induced cell cycle arrest and apoptosis in breast cancer cells. Mechanistically, MARK2 stimulates mTOR-mediated hypoxia-inducible factor 1 alpha (HIF-1α) transcription activity and represses p53-transcription activity in breast cancer cells. TCGA data revealed that MARK2 expression was positively correlated with mTOR, Raptor, S6K1, glucose transporter 1, lactate dehydrogenase, HIF-1α, and 4E-BP1 expression, whereas negatively correlated with p53, p21, and Bax in breast cancer tissue. Conclusively, our study demonstrated that MARK2 promotes breast cancer aerobic glycolysis and cell proliferation, and inhibits apoptosis, in part, through regulating mTOR/HIF-1α and p53 signaling pathways. Overall, these findings point to the potential of targeting MARK2 for breast cancer treatment.

The metabolic stress-activated checkpoint LKB1-MARK3 axis acts as a tumor suppressor in high-grade serous ovarian carcinoma

High-grade serous ovarian carcinoma (HGSOC) is the most aggressive gynecological malignancy, resulting in approximately 70% of ovarian cancer deaths. However, it is still unclear how genetic dysregulations and biological processes generate the malignant subtype of HGSOC. Here we show that expression levels of microtubule affinity-regulating kinase 3 (MARK3) are downregulated in HGSOC, and that its downregulation significantly correlates with poor prognosis in HGSOC patients. MARK3 overexpression suppresses cell proliferation and angiogenesis of ovarian cancer cells. The LKB1-MARK3 axis is activated by metabolic stress, which leads to the phosphorylation of CDC25B and CDC25C, followed by induction of G2/M phase arrest. RNA-seq and ATAC-seq analyses indicate that MARK3 attenuates cell cycle progression and angiogenesis partly through downregulation of AP-1 and Hippo signaling target genes. The synthetic lethal therapy using metabolic stress inducers may be a promising therapeutic choice to treat the LKB1-MARK3 axis-dysregulated HGSOCs.

Machino et al discover that low expression of microtubule affinity-regulating kinase 3 (MARK3) correlates with poor prognosis in high-grade serous ovarian carcinoma (HGSOC) patients. They find that the LKB1-MARK3 axis is activated by metabolic stress to block the cell cycle at the G2/M checkpoint, and characterise other MARK3 regulated pathways through RNA and ATAC sequencing.

Rab11-FIP1/RCP Functions as a Major Signalling Hub in the Oncogenic Roles of Mutant p53 in Cancer

Rab11-FIP1 is a Rab effector protein that is involved in endosomal recycling and trafficking of various molecules throughout the endocytic compartments of the cell. The consequence of this can be increased secretion or increased membrane expression of those molecules. In general, expression of Rab11-FIP1 coincides with more tumourigenic and metastatic cell behaviour. Rab11-FIP1 can work in concert with oncogenes such as mutant p53, but has also been speculated to be an oncogene in its own right. In this perspective, we will discuss and speculate upon our observations that mutant p53 promotes Rab11-FIP1 function to not only promote invasive behaviour, but also chemoresistance by regulating a multitude of different proteins.

Long non-coding RNA ABHD11-AS1 facilitates the progression of cervical cancer by competitively binding to miR-330-5p and upregulating MARK2

Cervical cancer (CC) is among the most prevalent gynecological malignancies. Participation of long non-coding RNA (lncRNA) in modulating biological behaviors of CC cells has been confirmed. However, the function of lncRNA ABHD11 antisense RNA 1 (ABHD11-AS1) in CC is still unclear. RT-qPCR and Western blot were performed for measuring RNA and protein levels. Functional assays were done to evaluate ABHD11-AS1 influences on cell proliferation, apoptosis, invasion and migration. After the verification of ABHD11-AS1 distribution in CC cells, mechanism assays were conducted to study the interaction of relative RNAs. ABHD11-AS1 expression was abnormally high in CC cells. In vitro experiments showed ABHD11-AS1 downregulation restrained CC cell malignant phenotypes. In vivo experiments proved ABHD11-AS1 knockdown impeded tumor growth. Moreover, miR-330-5p was corroborated to bind with ABHD11-AS1 in CC cells and microtubule affinity regulating kinase 2 (MARK2) was confirmed to be targeted by miR-330-5p. MiR-330-5p inhibition or MARK2 overexpression could countervail the suppressive effect of ABHD11-AS1 knockdown on CC cell malignant behaviors. We found that ABHD11-AS1 facilitated CC tumorigenesis through competitively sequestering miR-330-5p to upregulate MARK2, indicating ABHD11-AS1 as a potential biomarker in CC.

Generation of Two Paclitaxel-Resistant High-Grade Serous Carcinoma Cell Lines With Increased Expression of P-Glycoprotein

Debulking surgery followed by chemotherapy are the standard of care for high-grade serous carcinoma. After an initial good response to treatment, the majority of patients relapse with a chemoresistant profile, leading to a poor overall survival. Chemotherapy regimens used in high-grade serous carcinomas are based in a combination of classical chemotherapeutic drugs, namely, Carboplatin and Paclitaxel. The mechanisms underlying drug resistance and new drug discovery are crucial to improve patients’ survival. To uncover the molecular mechanisms of chemoresistance and test drugs capable of overcoming this resistant profile, it is fundamental to use good cellular models capable of mimicking the chemoresistant disease. Herein, we established two high-grade serous carcinoma cell lines with intrinsic resistance to Carboplatin and induced Paclitaxel resistance (OVCAR8 PTX R C and OVCAR8 PTX R P) derived from the OVCAR8 cell line. These two chemoresistant cell line variants acquired an enhanced resistance to Paclitaxel-induced cell death by increasing the drug efflux capacity, and this resistance was stable in long-term culture and following freeze/thaw cycles. The mechanism underlying Paclitaxel resistance resides in a significant increase in P-glycoprotein expression and, when this drug efflux pump was blocked with Verapamil, cells re-acquired Paclitaxel sensitivity. We generated two high-grade serous carcinoma cell lines, with a double-chemoresistant (Carboplatin and Paclitaxel) phenotype that mimics the majority of tumor recurrences in ovarian cancer context. This robust tool is suitable for preliminary drug testing towards the development of therapeutic strategies to overcome chemoresistance.

A proteogenomic portrait of lung squamous cell carcinoma

Lung squamous cell carcinoma (LSCC) remains a leading cause of cancer death with few therapeutic options. We characterized the proteogenomic landscape of LSCC, providing a deeper exposition of LSCC biology with potential therapeutic implications. We identify NSD3 as an alternative driver in FGFR1-amplified tumors and low-p63 tumors overexpressing the therapeutic target survivin. SOX2 is considered undruggable, but our analyses provide rationale for exploring chromatin modifiers such as LSD1 and EZH2 to target SOX2-overexpressing tumors. Our data support complex regulation of metabolic pathways by crosstalk between post-translational modifications including ubiquitylation. Numerous immune-related proteogenomic observations suggest directions for further investigation. Proteogenomic dissection of CDKN2A mutations argue for more nuanced assessment of RB1 protein expression and phosphorylation before declaring CDK4/6 inhibition unsuccessful. Finally, triangulation between LSCC, LUAD, and HNSCC identified both unique and common therapeutic vulnerabilities. These observations and proteogenomics data resources may guide research into the biology and treatment of LSCC.

PRKAR1A and Thyroid Tumors

Simple Summary

In 2021 it is estimated that there will be 44,280 new cases of thyroid cancer in the United States and the incidence rate is higher in women than in men by almost 3 times. Well-differentiated thyroid cancer is the most common subtype of thyroid cancer and includes follicular (FTC) and papillary (PTC) carcinomas. Over the last decade, researchers have been able to better understand the molecular mechanisms involved in thyroid carcinogenesis, identifying genes including but not limited to RAS, BRAF, PAX8/PPARγ chromosomal rearrangements and others, as well as several tumor genes involved in major signaling pathways regulating cell cycle, differentiation, growth, or proliferation. Patients with Carney complex (CNC) have increased incidence of thyroid tumors, including cancer, yet little is known about this association. CNC is a familial multiple neoplasia and lentiginosis syndrome cause by inactivating mutations in the PRKAR1A gene which encodes the regulatory subunit type 1α of protein kinase A. This work summarizes what we know today about PRKAR1A defects in humans and mice and their role in thyroid tumor development, as the first such review on this issue.

Abstract

Thyroid cancer is the most common type of endocrine malignancy and the incidence is rapidly increasing. Follicular (FTC) and papillary thyroid (PTC) carcinomas comprise the well-differentiated subtype and they are the two most common thyroid carcinomas. Multiple molecular genetic and epigenetic alterations have been identified in various types of thyroid tumors over the years. Point mutations in BRAF, RAS as well as RET/PTC and PAX8/PPARγ chromosomal rearrangements are common. Thyroid cancer, including both FTC and PTC, has been observed in patients with Carney Complex (CNC), a syndrome that is inherited in an autosomal dominant manner and predisposes to various tumors. CNC is caused by inactivating mutations in the tumor-suppressor gene encoding the cyclic AMP (cAMP)-dependent protein kinase A (PKA) type 1α regulatory subunit (PRKAR1A) mapped in chromosome 17 (17q22–24). Growth of the thyroid is driven by the TSH/cAMP/PKA signaling pathway and it has been shown in mouse models that PKA activation through genetic ablation of the regulatory subunit Prkar1a can cause FTC. In this review, we provide an overview of the molecular mechanisms contributing to thyroid tumorigenesis associated with inactivation of the RRKAR1A gene.

The cell polarity kinase Par1b/MARK2 activation selects specific NF-kB transcripts via phosphorylation of core mediator Med17/TRAP80

Par1b/MARK2 is a Ser/Thr kinase with pleiotropic effects that participates in the generation of apico-basal polarity in Caenorhabditis elegans. It is phosphorylated by atypical PKC(ι/λ) in Thr595 and inhibited. Because previous work showed a decrease in atypical protein kinase C (aPKC) activity under proinflammatory conditions, we analyzed the hypothesis that the resulting decrease in Thr595-MARK2 with increased kinase activity may also participate in innate immunity. We confirmed that pT595-MARK2 was decreased under inflammatory stimulation. The increase in MARK2 activity was verified by Par3 delocalization and rescue with a specific inhibitor. MARK2 overexpression significantly enhanced the transcriptional activity of NF-kB for a subset of transcripts. It also resulted in phosphorylation of a single band (∼Mr 80,000) coimmunoprecipitating with RelA, identified as Med17. In vitro phosphorylation showed direct phosphorylation of Med17 in Ser152 by recombinant MARK2. Expression of S152D-Med17 mimicked the effect of MARK2 activation on downstream transcriptional regulation, which was antagonized by S152A-Med17. The decrease in pThr595 phosphorylation was validated in aPKC-deficient mouse jejunal mucosae. The transcriptional effects were confirmed in transcriptome analysis and transcript enrichment determinations in cells expressing S152D-Med17. We conclude that theMARK2-Med17 axis represents a novel form of cross-talk between polarity signaling and transcriptional regulation including, but not restricted to, innate immunity responses.

Cross-resistance of cisplatin selected cells to anti-microtubule agents: Role of general survival mechanisms

Although the first line of therapy for epithelial ovarian cancer typically consists of taxane-platinum combination therapy, many patients develop a platinum-resistant tumor within a year. Several previous studies have looked at this cross-resistance between cisplatin and anti-microtubule drugs, but their findings have been somewhat conflicting. Here, we developed cisplatin-resistant cell lines that are resistant to low and high levels of cisplatin and explored the effects of three anti-microtubule drugs (paclitaxel, vincristine, and colchicine) on the parental and cisplatin-resistant cells. We found that cells resistant to lower levels of cisplatin were no more resistant to anti-microtubule drugs than parental cells, while cells that were resistant to higher levels of cisplatin had a subpopulation of cells that were cross-resistant to anti-microtubule drugs, clarifying discrepancies within the field. We then isolated this subpopulation by applying selective pressure with anti-microtubule drugs and performed RNA sequencing and gene set enrichment analysis to identify resistance mechanisms. This subpopulation was found to express increased levels of pro-survival TNF/NFκB signaling, among other enriched pathways, suggesting that cross-resistance was due to more general survival mechanisms found in the cisplatin-selected cells.

MARK2 enhances cisplatin resistance via PI3K/AKT/NF-κB signaling pathway in osteosarcoma cells

Osteosarcoma is the most common primary bone malignancy found in children and young adults. Chemotherapy resistance, especially to cisplatin, presents a major clinical challenge in the treatment and prognosis of osteosarcoma. New biomarkers and mechanisms of cisplatin resistance in osteosarcoma are urgently needed due to poor survival outcomes and currently inadequate treatments. In this study, we investigate the role and potential mechanisms of microtubule-affinity regulating kinase2 (MARK2) during osteosarcoma cisplatin resistance. Gene Expression Omnibus dataset analyses indicated that high MARK2 expression was associated with poor prognosis and may positively correlate with chemoresistance. Moreover, we showed that MARK2 was significantly upregulated in osteosarcoma cells compared with normal cells. The overexpression and inhibition of MARK2 promoted and suppressed, respectively, cisplatin resistance in osteosarcoma cells in vitro and in vivo. Mechanistically, MARK2 overexpression enhanced P-glycoprotein expression and decreased cell apoptosis through PI3K/AKT/NF-κB signaling pathway activation, resulting in cisplatin resistance. Our results suggest that high MARK2 expression can enhance cisplatin resistance in osteosarcoma cells, supporting the potential of MARK2 as a new therapeutic target and biomarker for predicting cisplatin resistance in osteosarcoma.

The inhibition of MARK2 suppresses cisplatin resistance of osteosarcoma stem cells by regulating DNA damage and repair

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MARK2 plays an important role in the chemoresistance mechanism of osteosarcoma stem cells.

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Down-regulation of MARK2 in CD133+ MG-63 and MNNG/HOS cells inhibits the expression of DNA-PKcs by inhibiting the activity of the PI3K/Akt/mTOR pathway.

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New clues for the osteosarcoma chemotherapy strategy.

Objective

This study aims to explore the role of MARK2 in chemotherapeutic resistance and potential mechanism within cisplatin resistance models of CD133⁺ MG-63 and MNNG/HOS cells.

Methods

CD133⁻ and CD133⁺ MG-63 and MNNG/HOS cells were differentiated and obtained by MACS(Magnetic bead sorting). Cell activity was determined by CCK-8 assay. siRNA was employed to down regulate the Microtubule Affinity Regulated Kinase 2 (MARK2) expression. Immunofluorescence detection and RT-qPCR were used to measure the expressions of MARK2 and DNA-PKcs at both protein and mRNA levels. Western blot was applied to test the levels of MARK2, γH2AX (S139), DNA-PKcs, Phospho-PI3 Kinase p85 (Tyr458), Akt, phospho-Akt (T308) antibodies, mTOR, phospho-mTOR (Ser2448).

Results

Compared with CD133⁻ MG-63 cells, CD133⁺ MG-63 cells showed significantly strong cisplatin resistance, with high levels of MARK2, DNA-PKcs and potent DNA damage repair ability (p<0.05). Down regulation of MARK2 reduced the cisplatin resistance of CD133⁺ MG-63 cells, with deceasing expression of DNA-PKcs (p<0.05). PI3K/Akt/mTOR pathway was potentially activated in CD133⁺ MG-63 cells, and involved in the cisplatin resistance of MG-63 cells. The similar results were observed in CD133⁺ MNNG/HOS cells. The reduction of MARK2 retarded the activity of PI3K/Akt/mTOR pathway and further impeded the cisplatin resistance in CD133⁺ MG-63 and MNNG/HOS cell.

Conclusion

Our data suggested that MARK2 was related to cisplatin resistance in CD133⁺ MG-63 and MNNG/HOS cells. The decrease of MARK2 restricted the cisplatin resistance of CD133⁺ MG-63 and MNNG/HOS cells by down regulating the expression of DNA dependent protein kinase catalytic subunit (DNA-PKcs) and inhibiting activity of PI3K/Akt/mTOR signaling pathway, which provides new clues for the osteosarcoma chemotherapy strategy.

PCC0208017, a novel small-molecule inhibitor of MARK3/MARK4, suppresses glioma progression in vitro and in vivo

Gliomas are the most common primary intracranial neoplasms among all brain malignancies, and the microtubule affinity regulating kinases (MARKs) have become potential drug targets for glioma. Here, we report a novel dual small-molecule inhibitor of MARK3 and MARK4, designated as PCC0208017. In vitro, PCC0208017 strongly inhibited kinase activity against MARK3 and MARK4, and strongly reduced proliferation in three glioma cell lines. This compound attenuated glioma cell migration, glioma cell invasion, and angiogenesis. Molecular mechanism studies revealed that PCC0208017 decreased the phosphorylation of Tau, disrupted microtubule dynamics, and induced a G2/M phase cell cycle arrest. In an in vivo glioma model, PCC0208017 showed robust anti-tumor activity, blood–brain barrier permeability, and a good oral pharmacokinetic profile. Molecular docking studies showed that PCC0208017 exhibited high binding affinity to MARK3 and MARK4. Taken together, our study describes for the first time that PCC0208017, a novel MARK3/MARK4 inhibitor, might be a promising lead compound for treatment of glioma.

PKA Activates AMPK Through LKB1 Signaling in Follicular Thyroid Cancer

Thyroid cancer affects about one percent of the population, and has seen rising incidence in recent years. Follicular thyroid cancer (FTC) comprises 10-15% of all thyroid cancers. Although FTC is often localized, it can behave aggressively with hematogenous metastasis, leading to an increased risk of cancer death. We previously described a mouse model for FTC caused by tissue-specific ablation of the Protein Kinase A (PKA) regulatory subunit Prkar1a, either by itself or in combination with knockout of Pten. Loss of Prkar1a causes enhanced activity of PKA, whereas ablation of Pten causes activation of Akt signaling. At the molecular level, these genetic manipulations caused activation of mTOR signaling, which was also observed in human FTC cases. To understand the mechanism by which PKA activates mTOR, we began by studying intracellular kinases known to modulate mTOR function. Although AMP-activated kinase (AMPK) has been characterized as a negative regulator of mTOR activity, our tumor model exhibited activation of both AMPK and mTOR. To understand the mechanism by which AMPK was turned on, we next studied kinases known to cause its phosphorylation. In this paper, we report that PKA leads to AMPK activation through the LKB1 kinase. Although LKB1 has traditionally been considered a tumor suppressor, our data indicates that it may have a complex role in the thyroid gland, where its activation appears to be frequently associated with follicular thyroid carcinoma in both mice and humans.

miR-17-92 and miR-106b-25 clusters regulate beta cell mitotic checkpoint and insulin secretion in mice

AIMS/HYPOTHESIS

Adult beta cells in the pancreas are the sole source of insulin in the body. Beta cell loss or increased demand for insulin impose metabolic challenges because adult beta cells are generally quiescent and infrequently re-enter the cell division cycle. The aim of this study is to test the hypothesis that a family of proto-oncogene microRNAs that includes miR-17-92 and miR-106b-25 clusters regulates beta cell proliferation or function in the adult endocrine pancreas.

METHODS

To elucidate the role of miR-17-92 and miR-106b-25 clusters in beta cells, we used a conditional miR-17-92/miR-106b-25 knockout mouse model. We employed metabolic assays in vivo and ex vivo, together with advanced microscopy of pancreatic sections, bioinformatics, mass spectrometry and next generation sequencing, to examine potential targets of miR-17-92/miR-106b-25, by which they might regulate beta cell proliferation and function.

RESULTS

We demonstrate that miR-17-92/miR-106b-25 regulate the adult beta cell mitotic checkpoint and that miR-17-92/miR-106b-25 deficiency results in reduction in beta cell mass in vivo. Furthermore, we reveal a critical role for miR-17-92/miR-106b-25 in glucose homeostasis and in controlling insulin secretion. We identify protein kinase A as a new relevant molecular pathway downstream of miR-17-92/miR-106b-25 in control of adult beta cell division and glucose homeostasis.

CONCLUSIONS/INTERPRETATION

The study contributes to the understanding of proto-oncogene miRNAs in the normal, untransformed endocrine pancreas and illustrates new genetic means for regulation of beta cell mitosis and function by non-coding RNAs.

DATA AVAILABILITY

Sequencing data that support the findings of this study have been deposited in GEO with the accession code GSE126516.

Inhibition of polarity-regulating kinase PAR1b contributes to Helicobacter pylori inflicted DNA Double Strand Breaks in gastric cells

The serine/threonine kinase Par1 is a core component of the machinery that sets up polarity in the embryo and regulates cell fate decisions but its role in the homeostasis of adult tissues is poorly understood. Inhibition of Par1 by the bacterium Helicobacter pylori (H. pylori) represents the only established pathology that affects Par1 function in an adult epithelium. Thus, during chronic H. pylori infection of the gastric mucosa Par1 is one of the targets of the non-obligate H.pylori cytotoxic protein and oncogene CagA, which stimulates inflammation and triggers morphological changes, both believed to contribute to the gastric cancer risk imposed by H. pylori infection. Based on Par1's role in cell polarity, it has been speculated that Par1 inhibition affects epithelial polarity. Here we report the unexpected finding that CagA-mediated Par1-inhibition promotes the generation of DNA Double Strand Breaks in primary gastric epithelial cells, which likely contributes to the reported accumulation of mutations in chronically infected mucosal cells. Abbreviations: AGS: human gastric adenocarcinoma cell line; CM: CagA Multimerization (and Par1 binding) domain; H. pylori: Helicobacter pylori; DSB: Double Strand Break; HGECs: human (primary) gastric epithelial cells; IB: immunoblot; IF: immunofluorescence; MOI: Multiplicity of Infection; ROS: reactive oxygen species; Par1: Partitioning Defective 1 kinase; WT: wild type.

Quantitative assessment of gene promoter methylation in non-small cell lung cancer using methylation-sensitive high-resolution melting

DNA methylation is closely associated with aberrant epigenetic changes. Previous studies have identified various genes associated with non-small cell lung cancer (NSCLC), but the precise combination responsible for its etiology is still debated. The aim of the present study was to select a new set of NSCLC-related genes using methylation-sensitive high-resolution melting. The promoter methylation status of six selected genes, consisting of protocadherin γ subfamily B, 6 (PCDHGB6), homeobox A9 (HOXA9), O₆-methylguanine-DNA methyltransferase (MGMT), microRNA (miR)-126, suppressor of cytokine signaling 3 (SOCS3) and Ras association domain family member 5, also termed NORE1A, was evaluated in 54 NSCLC patients. From these samples, genome-wide DNA was extracted and bisulfite conversion was performed along with fluorogenic quantitative polymerase chain reaction to detect methylation values of the six selected promoters. The present results revealed frequent methylation on PCDHGB6, HOXA9 and miR-126, which contrasted with infrequent methylation on MGMT. The results indicated no methylation on either SOCS3 or NORE1A. The sensitivity and specificity of the methylation assessment were 85.2 and 81.5%, respectively, and the analysis results were validated by pyrosequencing. Furthermore, minute comparison of the association between DNA methylation and clinical features was performed. Overall, these results may provide potential information for the development of better clinical diagnostics and more targeted and effective therapies for NSCLC.

Microtubule affinity-regulating kinases are potential druggable targets for Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that affects normal functions of the brain. Currently, AD is one of the leading causes of death in developed countries and the only one of the top ten diseases without a means to prevent, cure, or significantly slow down its progression. Therefore, newer therapeutic concepts are urgently needed to improve survival and the quality of life of AD patients. Microtubule affinity-regulating kinases (MARKs) regulate tau-microtubule binding and play a crucial role in neurons. However, their role in hyperphosphorylation of tau makes them potential druggable target for AD therapy. Despite the relevance of MARKs in AD pathogenesis, only a few small molecules are known to have anti-MARK activity and not much has been done to progress these compounds into therapeutic candidates. But given the diverse role of MARKs, the specificity of novel inhibitors is imperative for their successful translation from bench to bedside. In this regard, a recent co-crystal structure of MARK4 in association with a pyrazolopyrimidine-based inhibitor offers a potential scaffold for the development of more specific MARK inhibitors. In this manuscript, we review the biological role of MARKs in health and disease, and draw attention to the largely unexplored area of MARK inhibitors for AD.

A data mining approach for identifying pathway-gene biomarkers for predicting clinical outcome: A case study of erlotinib and sorafenib

A novel data mining procedure is proposed for identifying potential pathway-gene biomarkers from preclinical drug sensitivity data for predicting clinical responses to erlotinib or sorafenib. The analysis applies linear ridge regression modeling to generate a small (N~1000) set of baseline gene expressions that jointly yield quality predictions of preclinical drug sensitivity data and clinical responses. Standard clustering of the pathway-gene combinations from gene set enrichment analysis of this initial gene set, according to their shared appearance in molecular function pathways, yields a reduced (N~300) set of potential pathway-gene biomarkers. A modified method for quantifying pathway fitness is used to determine smaller numbers of over and under expressed genes that correspond with favorable and unfavorable clinical responses. Detailed literature-based evidence is provided in support of the roles of these under and over expressed genes in compound efficacy. RandomForest analysis of potential pathway-gene biomarkers finds average treatment prediction errors of 10% and 22%, respectively, for patients receiving erlotinib or sorafenib that had a favorable clinical response. Higher errors were found for both compounds when predicting an unfavorable clinical response. Collectively these results suggest complementary roles for biomarker genes and biomarker pathways when predicting clinical responses from preclinical data.

Regulation of Cell Polarity by PAR-1/MARK Kinase

PAR-1/MARK kinases are conserved serine/threonine kinases that are essential regulators of cell polarity. PAR-1/MARK kinases localize and function in opposition to the anterior PAR proteins to control the asymmetric distribution of factors in a wide variety polarized cells. In this review, we discuss the mechanisms that control the localization and activity of PAR-1/MARK kinases, including their antagonistic interactions with the anterior PAR proteins. We focus on the role PAR-1 plays in the asymmetric division of the Caenorhabditis elegans zygote, in the establishment of the anterior/posterior axis in the Drosophila oocyte and in the control of microtubule dynamics in mammalian neurons. In addition to conserved aspects of PAR-1 biology, we highlight the unique ways in which PAR-1 acts in these distinct cell types to orchestrate their polarization. Finally, we review the connections between disruptions in PAR-1/MARK function and Alzheimer's disease and cancer.

Baicalin attenuates DDP (cisplatin) resistance in lung cancer by downregulating MARK2 and p-Akt

DDP (cisplatin) resistance in lung cancer has been widely reported. Baicalin is a flavone glycoside found in genus Scutellaria. However, the effects of baicalin on DDP resistance in lung cancer are unclear. The aim of present study was to investigate effects of combination of baicalin and DDP on proliferation and invasion of human lung cancer cells, and explore possible mechanisms. MTT assay was utilized to evaluate effects of baicalin and DDP on the proliferation of A549 and A549/DPP (DPP-resistant) human lung cancer cells. The probability sum method was used to determine effects of the drug combination. Transwell invasion assay was utilized to detect tumor cell invasion. The mRNA expression of MARK2 in A549 and A549/DPP cells was detected by qPCR. Protein expression of MARK2, p-Akt and Akt was detected by western blot analysis. Baicalin and DPP when used alone inhibited the proliferation of A549 and A549/DDP cells in a dose-dependent manner at 24 and 48 h. For A549 cells, baicalin (8 µg/ml) antagonized DDP (1, 2, 4 and 8 µg/ml) at 24 h. For A549/DDP cells, baicalin and DDP were additive when the concentration of DDP was 4 µg/ml at 24 h. Effects of baicalin and DDP on proliferation inhibition were additive and synergistic when concentrations of DDP were 8 and 4 µg/ml, respectively, at 48 h for both A549 and A549/DDP cells. When baicalin (8 µg/ml) and DDP (4 µg/ml) were combined, the inhibitory rate of tumor cell invasion increased markedly compared to DPP or baicalin alone groups in both A549 and A549/DDP cells. A549/DDP cells had significantly higher MARK2 mRNA levels and protein expression of MARK2 and p-Akt. Baicalin decreased MARK2 mRNA and protein expression of MARK2 and p-Akt in A549/DDP cells dose-dependently. In conclusion, baicalin and DDP were synergistic at inhibiting proliferation and invasion of human lung cancer cells at appropriate dosages and incubation time in the presence or absence of DDP resistance. The attenuation of DDP resistance was associated with downregulation of MARK2 and p-Akt.

Predictors of chemotherapy efficacy in non-small-cell lung cancer: a challenging landscape

BACKGROUND

Conventional cytotoxic chemotherapy (CCC) is the backbone of non-small-cell lung cancer (NSCLC) treatment since decades and still represents a key element of the therapeutic armamentarium. Contrary to molecularly targeted therapies and immune therapies, for which predictive biomarkers of activity have been actively looked for and developed in parallel to the drug development process ('companion biomarkers'), no patient selection biomarker is currently available for CCC, precluding customizing treatment.

MATERIALS AND METHODS

We reviewed preclinical and clinical studies that assessed potential predictive biomarkers of CCC used in NSCLC (platinum, antimetabolites, topoisomerase inhibitors, and spindle poisons). Biomarker evaluation method, analytical validity, and robustness are described and challenged for each biomarker.

RESULTS

The best-validated predictive biomarkers for efficacy are currently ERCC1, RRM1, and TS for platinum agents, gemcitabine and pemetrexed, respectively. Other potential biomarkers include hENT1 for gemcitabine, class III β-tubulin for spindle poisons, TOP2A expression and CEP17 duplication (mostly studied for predicting anthracyclines efficacy) whose applicability concerning etoposide would deserve further evaluation. However, none of these biomarkers has till now been validated prospectively in an appropriately designed and powered randomised trial, and none of them is currently ready for implementation in routine clinical practice.

CONCLUSION

The search for predictive biomarkers to CCC has been proven challenging. If a plethora of biomarkers have been evaluated either in the preclinical or in the clinical setting, none of them is ready for clinical implementation yet. Considering that most mechanisms of resistance or sensitivity to CCC are multifactorial, a combinatorial approach might be relevant and further efforts are required.

Combination of gambogic acid with cisplatin enhances the antitumor effects on cisplatin-resistant lung cancer cells by downregulating MRP2 and LRP expression

Cisplatin resistance is a main clinical problem of lung cancer therapy. Gambogic acid (GA) could prohibit the proliferation of a variety of human cancer cells. However, the effects of GA on cisplatin-resistant lung cancer are still unclear. The objective of the present study was to find out the antitumor effects of GA on cisplatin-resistant human lung cancer A549/DDP cells and further explore its underlying mechanisms. Cell Counting Kit-8 assay was used to observe the impacts of GA and/or cisplatin on the proliferation of lung cancer cells; flow cytometry was used to detect the effects of GA on cell cycle and apoptosis; Western blot was used to examine the effects of GA on the expression of lung resistance protein (LRP) and multidrug resistance-associated protein 2 (MRP2) protein in A549/DDP cells. Our results showed that GA dose- and time-dependently prohibited the proliferation and induced significant cell apoptosis in A549 and A549/DDP cells. GA also induced G0/G1 arrest in both A549/DDP and A549 cells. Moreover, GA upregulated protein expression level of cleaved caspase-3 and Bax and downregulated protein expression level of pro-caspase-9 and Bcl-2 in time- and dose-dependent way in A549/DDP cells. GA combined with cisplatin enhanced the cells apoptotic rate and reduced the cisplatin resistance index in A549/DDP cells. In addition, GA reduced the MRP2 and LRP protein expression level in A549/DDP cells. GA inhibits the proliferation, induces cell cycle arrest and apoptosis in A549/DDP cells. Combination of GA with cisplatin enhances the antitumor effects on cisplatin-resistant lung cancer cells by downregulating MRP2 and LRP expression.

Evidence of cancer-promoting roles for AMPK and related kinases

The discovery that the 5'AMP-activated protein kinase (AMPK) serves to link the tumour suppressors LKB1 and the tuberous sclerosis complex and functions to slow macromolecular synthesis through attenuation of the mechanistic target of rapamycin complex 1 revealed a role for AMPK in tumour suppression. On the other hand, the well-recognized role of AMPK in maintaining ATP homeostasis, through suppression of anabolism and promotion of catabolism, as well as the role of AMPK in neutralizing reactive oxygen species, via maintenance of NADPH-dependent reductive capacity, point to tumour-protective roles in the context of metabolic stress, which is a key feature of many solid tumours. A growing number of studies thus suggest a duality of functions for AMPK that are either pro- or anti-cancer, depending upon context. Importantly, AMPK is composed of three subunits, and multiple isoforms exist for all three, allowing for different permutations to assemble and the potential for specific AMPK complexes to regulate distinct cellular processes. Moreover, certain subunits of the AMPK complex are frequently overexpressed in a spectrum of human cancer types, suggesting an outright oncogenic function for specific AMPK complexes. Adding complexity to this picture, the catalytic AMPK alpha subunits belong to a family of 14 kinases that can all be activated by LKB1 and studies are beginning to reveal a similar duality of roles in cancer for other members of the AMPK-related kinase family.

Gene expression analysis of microtubule affinity-regulating kinase 2 in non-small cell lung cancer

Lung cancer is the leading cause of cancer death worldwide, and has a five-year survival rate of 18% [1]. MARK2 is a serine/threonine-protein kinase, and is a key component in the phosphorylation of microtubule-associated proteins [2], [3]. A recent study published by Hubaux et al. found that microtubule affinity-regulating kinase 2 (MARK2) showed highly frequent DNA and RNA level disruption in lung cancer cell lines and independent non-small cell lung cancer (NSCLC) cohorts [4]. These alterations result in the acquisition of oncogenic properties in cell lines, such as increased viability and anchorage-independent growth. Furthermore, a microarray-based transcriptome analysis of three short hairpin RNA (shRNA)-mediated MARK2 knockdown lung adenocarcinoma cell lines (GEO#: GSE57966) revealed an association between MARK2 gene expression and cell cycle activation and DNA damage response. Here, we present a detailed description of transcriptome analysis to support the described role of MARK2 in promoting a malignant phenotype.