Chk1 Protein Research Articles

Integrative data fusion for comprehensive assessment of a novel CHEK2 variant using combined genomics, imaging, and functional-structural assessments via protein informatics.

The CHEK2 gene and its encoded protein Chk2 have a well-known role in cancers, especially those related to breast cancer mediated through the BRCA1 gene. Additionally Chk2 has a crucial role in DNA repair, apoptosis and the cell cycle, which is why classification of variants of uncertain significance (VUS) is an area highly sought for a better elucidation of the "genomic effect" that results. Because it can often take years before enough clinical data is accumulated, and the costly and expensive functional analysis for individual variants presents a significant hurdle, it is important to identify other tools to help aid in clarifying the impact of specific variants on a protein's function and eventually the patient's health outcome. Here we describe a newly identified CHEK2 variant and analyze with an integrated approach combining genomics (whole exome analysis), clinical study, radiographic imaging, and protein informatics to identify and predict the functional impact of the VUS on the protein's behavior and predicted impact on the related pathways. The observed and analyzed defects in the protein were consistent with the expected clinical effect. Here, we support the use of personalized protein modeling and informatics and further our goal of developing a large-scale protein deposition archive for all protein-level VUS.

Using HSP90 Inhibitors to Target DNA Repair Proteins in AML

Acute myeloid leukemia (AML) is a disease of proliferative and abnormally differentiated myeloid cells(Döhner, Weisdorf, & Bloomfield, 2015) that is characterized by chromosomal aberrations and gene mutations that influence outcome(De Kouchkovsky & Abdul-Hay, 2016). Despite the approval of targeted therapies, induction therapy with cytarabine (Ara-C) and anthracycline has remained the standard of care for AML(Dombret & Gardin, 2016; Showel & Levis, 2014). Newer chemotherapeutics such as Sapacitabine have shown comparable clinical outcomes to Ara-C in older patients(Burnett et al., 2015). Ara-C is a nucleoside analog which incorporates during DNA replication and stalls replication(Liu et al., 2010) while Sapacitabine induces single stranded nicks in the DNA leading to double stranded breaks which are repaired by Homologous Recombination (HR)(Burnett et al., 2015; Lim & Jamieson, 2014). However, eventually patients develop resistance to chemotherapy leading to poor prognosis after relapse(Wu, Duan, Chen, & Chen, 2017). One aspect of this is due to upregulation of DNA damage repair proteins leading to increased repair of any DNA lesions primarily through HR. We therefore are interested in developing a way to target DNA repair to extend nucleoside analog therapy in AML.HSP90 is a molecular chaperone that is critical for the folding and proper function of multiple key proteins of various DNA repair pathways(Dote, Burgan, Camphausen, & Tofilon, 2006). Relevant to such repair, ATM and Chk1 become recruited to DNA double strand breaks to activate defined downstream signaling cascades that result in cell cycle arrest and DNA repair(Ceccaldi, Rondinelli, & D'Andrea, 2016). Of these,γ-H2AX acts a sensor of DNA damage and repair by forming foci at the sites of damaged DNA that get resolved upon successful repair(Sharma, Singh, & Almasan, 2012). Similarly, the Rad51 helicase plays a key role in HR repair and the presence of Rad51 foci can be used as a marker for successful HR(Gachechiladze, Škarda, Soltermann, & Joerger, 2017). To determine whether inhibiting HSP90 compromised DNA repair, we treated both AML cell lines OCI-AML3 and MV4-11 with HSP90 inhibitor, onalespib. OCI-AML3 cells show a time dependent decrease in DNA damage repair proteins Chk1 and Rad51 by western blotting. Furthermore, primary patient samples treated with onalespib for 24 and 36 hours also show a depletion of Chk1 and Rad51. We then used ionizing radiation (IR) to induce dsbreaks and induce signaling and repair(Ceccaldi et al., 2016). Using immunofluorescence, we found that in OCI-AML3 after exposure to IR there was a significant increase in number of Rad51 foci after 6 hours. The large number of γ-H2AX foci formed at .5 hour after IR decrease by 6 hours post-IR. This suggests that there is a successful HR repair occurring in this AML cell line. When OCI-AML3 cells were pretreated with onalespib, Rad51 foci are no longer present and γ-H2AX foci remained present at 6 hours suggesting unrepaired dsbreaks. Using the colony forming assay we see that there is a slight decrease in viability of OCI-AML3 cells exposed to onalespib however, in MV4-11 cells there is a steep decline which could be due to the differential expression of genes such as FLT3-ITD, a client protein of HSP90. Low doses of cytarabine or sapacitabine modestly decreased colony growth of OCI-AML3 and MV4-11 cells but exposing cells to onalespib for 24 hours sensitized the cells to both cytarabine and sapacitabine. Finally, we have also evaluated effects of onalespib in an in-vivo MOLM13 driven mouse model of AML and have shown that treatment with onalespib extended survival in this mouse model. DisclosuresMims:Abbvie Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy.

ATR/Chk1 Pathway is Activated by Oxidative Stress in Response to UVA Light in Human Xeroderma Pigmentosum Variant Cells.

The crucial role of DNA polymerase eta in protecting against sunlight-induced tumors is evidenced in Xeroderma Pigmentosum Variant (XP-V) patients, who carry mutations in this protein and present increased frequency of skin cancer. XP-V cellular phenotypes may be aggravated if proteins of DNA damage response (DDR) pathway are blocked, as widely demonstrated by experiments with UVC light and caffeine. However, little is known about the participation of DDR in XP-V cells exposed to UVA light, the wavelengths patients are mostly exposed. Here, we demonstrate the participation of ATR kinase in protecting XP-V cells after receiving low UVA doses using a specific inhibitor, with a remarkable increase in sensitivity and γH2AX signaling. Corroborating ATR participation in UVA-DDR, a significant increase in Chk1 protein phosphorylation, as well as S-phase cell cycle arrest, is also observed. Moreover, the participation of oxidative stress is supported by the antioxidant action of N-acetylcysteine (NAC), which significantly protects XP-V cells from UVA light, even in the presence of the ATR inhibitor. These findings indicate that the ATR/Chk1 pathway is activated to control UVA-induced oxidatively generated DNA damage and emphasizes the role of ATR kinase as a mediator of genomic stability in pol eta defective cells.

The Ataxia telangiectasia-mutated and Rad3-related protein kinase regulates cellular hydrogen sulfide concentrations

The ataxia telangiectasia-mutated and Rad3-related (ATR) serine/threonine kinase plays a central role in the repair of replication-associated DNA damage, the maintenance of S and G2/M-phase genomic stability, and the promotion of faithful mitotic chromosomal segregation. A number of stimuli activate ATR, including persistent single-stranded DNA at stalled replication folks, R loop formation, hypoxia, ultraviolet light, and oxidative stress, leading to ATR-mediated protein phosphorylation. Recently, hydrogen sulfide (H2S), an endogenous gasotransmitter, has been found to regulate multiple cellular processes through complex redox reactions under similar cell stress environments. Three enzymes synthesize H2S: cystathionine-β-synthase, cystathionine γ-lyase, and 3-mercaptopyruvate sulfurtransferase. Since H2S can under some conditions cause DNA damage, we hypothesized that ATR activity may regulate cellular H2S concentrations and H2S-syntheszing enzymes. Here we show that human colorectal cancer cells carrying biallelic knock-in hypomorphic ATR mutations have lower cellular H2S concentrations than do syngeneic ATR wild-type cells, and all three H2S-synthesizing enzymes show lower protein expression in the ATR hypomorphic mutant cells. Additionally, ATR serine 428 phosphorylation is altered by H2S donor and H2S synthesis enzyme inhibition, while the oxidative-stress induced phosphorylation of the ATR-regulated protein CHK1 on serine 345 is increased by H2S synthesis enzyme inhibition. Lastly, inhibition of H2S production potentiated oxidative stress-induced double-stranded DNA breaks in the ATR hypomorphic mutant compared to ATR wild-type cells. Our findings demonstrate that the ATR kinase regulates and is regulated by H2S.

Cellular Depletion of BRD8 Causes p53-Dependent Apoptosis and Induces a DNA Damage Response in Non-Stressed Cells

Regulation of the chromatin state is crucial for biological processes such as the regulation of transcription, DNA replication, and DNA damage repair. Here we show that knockdown of the BRD8 bromodomain protein – a subunit of the p400/Tip60 complex - leads to p21 induction, and concomitant cell cycle arrest in G1/S. We further demonstrate that the p53 transcriptional pathway is activated in BRD8-depleted cells, and this accounts for upregulation of not only p21 but also of pro-apoptotic genes, leading to subsequent apoptosis. Importantly, the DNA damage response (DDR) is induced upon BRD8 depletion, and DNA damage foci are detectable in BRD8-depleted cells under normal growth conditions. Consistently with an activated DDR, we find that in BRD8-depleted cells, the ATM-CHK2 DDR pathway is turned on but, CHK1 proteins levels are severely reduced and replication stress is detectable as enhanced replication protein A (RPA32) phosphorylation levels. Notably, acetylation of histone H4 at K16 (H4K16ac) is reduced in BRD8-depleted cells, suggesting that BRD8 may have a role in the recruitment and/or stabilization of the p400/Tip60 complex within chromatin, thereby facilitating DNA repair. Taken together, our results suggest that BRD8 is involved not only in p53-dependent gene suppression, but also in the maintenance of genome stability.

Melanoma LAMP-2C Modulates Tumor Growth and Autophagy.

Autophagy plays critical but diverse roles in cellular quality control and homeostasis potentially checking tumor development by removing mutated or damaged macromolecules, while conversely fostering tumor survival by supplying essential nutrients during cancer progression. This report documents a novel inhibitory role for a lysosome-associated membrane protein, LAMP-2C in modulating autophagy and melanoma cell growth in vitro and in vivo. Solid tumors such as melanomas encounter a variety of stresses in vivo including inflammatory cytokines produced by infiltrating lymphocytes directed at limiting tumor growth and spread. Here, we report that in response to the anti-tumor, pro-inflammatory cytokine interferon-gamma, melanoma cell expression of LAMP2C mRNA significantly increased. These results prompted an investigation of whether increased melanoma cell expression of LAMP-2C might represent a mechanism to control or limit human melanoma growth and survival. In this study, enhanced expression of human LAMP-2C in melanoma cells perturbed macroautophagy and chaperone-mediated autophagy in several human melanoma lines. In vitro analysis showed increasing LAMP-2C expression in a melanoma cell line, triggered reduced cellular LAMP-2A and LAMP-2B protein expression. Melanoma cells with enhanced LAMP-2C expression displayed increased cell cycle arrest, increased expression of the cell cycle regulators Chk1 and p21, and greater apoptosis and necrosis in several cell lines tested. The increased abundance of Chk1 protein in melanoma cells with increased LAMP-2C expression was not due to higher CHEK1 mRNA levels, but rather an increase in Chk1 protein abundance including Chk1 molecules phosphorylated at Ser345. Human melanoma cell xenografts with increased LAMP-2C expression, displayed reduced growth in immune compromised murine hosts. Melanomas with high LAMP-2C expression showed increased necrosis and reduced cell density upon histological analysis. These results reveal a novel role for LAMP-2C in negatively regulating melanoma growth and survival.

Chk1 inhibition as a novel therapeutic strategy in melanoma.

Melanoma patients respond poorly to chemotherapies because they acquire drug resistance. Therapies that can overcome the resistance to inhibitors of the mutated BRAF protein kinase in melanoma are urgently needed. Chk1 protein kinase is a central component of the DNA damage response and plays a crucial role in controlling cell cycle progression. Analyses indicate that low mRNA expression of Chk1 is significantly associated with good overall survival of melanoma patients. To evaluate the effectiveness of Chk1 inhibitors in melanoma therapy, we have generated BRAF inhibitor (PLX4032 or vemurafenib) resistant melanoma cell lines (A375-PLX-R and WM9-PLX-R) from A375 and WM9, respectively. We observe that AKT (protein kinase B) is constitutively activated in A375-PLX-R, but not in WM9-PLX-R cells, suggesting that these cells develop resistance to PLX4032 through different mechanisms. We show that a potent and specific inhibitor of Chk1 (PF477736) is effective in reducing cell viability and colony formation of PLX4032-resistant cells. Even more impressively, PF477736 triggers PLX4032-resistant melanoma cells to regain sensitivity to the PLX4032. Mouse xenograft studies show that treating A375-PLX-R derived tumors with combined PLX4032 and PF477736 significantly reduce tumor growth. Combined treatments with PLX4032 and PF477736 reduce the levels of total Chk1 protein and alter Chk1 phosphorylation at several sites in both PLX4032 sensitive and resistant melanoma cells. Combinatorial treatments with PLX4032 and PF477736 to melanoma cells substantially induce DNA damage and cell death. Our results suggest that Chk1 inhibitors may provide new therapy options for melanoma patients.

Suppression of ribosomal protein RPS6KB1 by Nexrutine increases sensitivity of prostate tumors to radiation

Radiation therapy (XRT) is a standard treatment for prostate cancer (PCa). Although dose escalation increases local control, toxicity hampers further escalation. Broader improvement will be possible by the addition of adjuvant therapies, which can synergize with radiation and thus improve efficacy. We have identified a natural compound (Nexrutine, Nx) that inhibits the survival and growth of PCa cells in combination with radiation. Combination studies demonstrated strong interaction between Nx and radiation both in vitro in multiple PCa cell lines and in the Transgenic adenocarcinoma of mouse prostate (TRAMP) model. Nx potentiated growth inhibitory effects of IR by down regulating ribosomal protein S6K (RPS6KB1), CyclinD1, Chk1 and HIF-1 α and prolonging G2/M checkpoint block. RPS6KB1 is upregulated in prostate cancers and its expression is correlated with tumor grade. Knockdown of RPS6KB1 in PCa cells increased their sensitivity toward radiation-induced survival inhibition. Overall, we provide scientific evidence (i) in support of Nx as an adjuvant in PCa patients receiving XRT (ii) suggesting that RPS6KB1 is an important player in Nx-mediated combinatorial benefits and emphasizes that RPS6KB1 is a novel target for PCa treatment. These data underscore the need to test the agent in additional preclinical models to validate these observations.

Abstract 4927: Plasma and CNS pharmacokinetics of the CHK-1 inhibitor prexasertib (LY-2606368) in mice bearing orthotopic group 3 medulloblastoma

Abstract Many children with brain tumors have limited treatment options and poor long-term survival. A key protein kinase involved in activating and maintaining the S and G2/M checkpoints is CHK1, which when inhibited in the absence of p53 leads to loss of DNA damage checkpoints and can enhance the activity of many DNA-damaging agents. Prexasertib (LY-2606368), a potent and selective small molecule inhibitor of CHK1 protein kinase activity in vitro (IC50 <1 nM), is currently under clinical evaluation for treatment of pediatric malignancies. To evaluate prexasertib in preclinical efficacy studies for pediatric brain tumor models, the ratio of free drug concentrations between the central nervous system (CNS) and plasma (Kpu,u) is typically computed as a surrogate to measure CNS penetration. To facilitate the prospective determination of preclinical CNS Kpu,u values, we evaluated the plasma pharmacokinetic (PK) disposition of prexasertib in a murine model of medulloblastoma. A plasma PK study was performed using CD1 nude mice orthotopically implanted with group 3 medulloblastoma to obtain initial prexasertib PK parameters. Tumor growth was assessed by bioluminescence imaging (D-Luciferin) and mice were enrolled in the study once tumors reached 1x10~8-9 photons/second. Prexasertib mesylate monohydrate was reconstituted in 20% Captisol and administered subcutaneously at a dosage of 10 mg/kg (free base). A population based study design was used in which 3 samples per mouse were obtained. Plasma samples were prepared using a liquid-liquid extraction technique, and analyzed for prexasertib using a validated LC-MS/MS method (LLOQ = 0.2 µg/L). A two-compartment PK model was fit to the prexasertib concentration-time data using nonlinear mixed effects modeling (NONMEM 7.3, ICON Development Solutions). Plasma PK parameters from this model were used with the D-optimality criterion as implemented in ADAPT (D'Argenio, 1981) to derive a limited sampling model (LSM) for use in upcoming cerebral microdialysis studies. The results of our plasma PK studies showed a Cmax, terminal half-life, and AUC in CD1 nude mice bearing group 3 medulloblastoma of 1015 µg/L, 4.5 hours, and 1773 µg*hr/L, respectively. The LSM for plasma PK that will be used in the cerebral microdialysis studies include the time points of 0.25, 6.6, and 24 hours. Now that the plasma PK and a LSM are defined, we are poised to begin cerebral microdialysis studies in CD1 nude mice bearing group 3 medulloblastoma. Citation Format: Anil Maharaj, Abigail Davis, Bo Zhong, Martine F. Roussel, Clinton F. Stewart. Plasma and CNS pharmacokinetics of the CHK-1 inhibitor prexasertib (LY-2606368) in mice bearing orthotopic group 3 medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4927.

The contribution of DNA replication stress marked by high-intensity, pan-nuclear γH2AX staining to chemosensitization by CHK1 and WEE1 inhibitors

ABSTRACTSmall molecule inhibitors of the checkpoint proteins CHK1 and WEE1 are currently in clinical development in combination with the antimetabolite gemcitabine. It is unclear, however, if there is a therapeutic advantage to CHK1 vs. WEE1 inhibition for chemosensitization. The goals of this study were to directly compare the relative efficacies of the CHK1 inhibitor MK8776 and the WEE1 inhibitor AZD1775 to sensitize pancreatic cancer cell lines to gemcitabine and to identify pharmacodynamic biomarkers predictive of chemosensitization. Cells treated with gemcitabine and either MK8776 or AZD1775 were first assessed for clonogenic survival. With the exception of the homologous recombination-defective Capan1 cells, which were relatively insensitive to MK8776, we found that these cell lines were similarly sensitized to gemcitabine by CHK1 or WEE1 inhibition. The abilities of either the CDK1/2 inhibitor roscovitine or exogenous nucleosides to prevent MK8776 or AZD1775-mediated chemosensitization, however, were both inhibitor-dependent and variable among cell lines. Given the importance of DNA replication stress to gemcitabine chemosensitization, we next assessed high-intensity, pan-nuclear γH2AX staining as a pharmacodynamic marker for sensitization. In contrast to total γH2AX, aberrant mitotic entry or sub-G1 DNA content, high-intensity γH2AX staining correlated with chemosensitization by either MK8776 or AZD1775 (R2 0.83 – 0.53). In summary, we found that MK8776 and AZD1775 sensitize to gemcitabine with similar efficacy. Furthermore, our results suggest that the effects of CHK1 and WEE1 inhibition on gemcitabine-mediated replication stress best predict chemosensitization and support the use of high-intensity or pan-nuclear γH2AX staining as a marker for therapeutic response.

P-105 - Effect of a novel biscumarin derivative on human melanoma cells: Regulation of cell survival, proliferation, migration and kinases

We have investigated the effects of a newly synthesized biscumarin derivative on cell survival, proliferation, migration and signal transduction pathways in the human metastatic melanoma cells A375. Among the modulated pathways of cell survival and tumor suppression we found highly significant effects of this novel synthetic derivative on TOR (Target of Rapamycin), Checkpoint Kinase 2 (Chk- 2), Tumor Suppressor Protein Kinase p53 ( P53), Additionally the compound was found to modulate a number of pathways of cell proliferation with varying degree of efficacy. We have shown that biscumarin derivative induced activation of Epidermal Growth Factor Receptor (EGFR), Focal Adhesion Kinase (FAK), cAMP response Element-Binding Protein (CREB), Glycogen Synthase Kinase (GSK3 α/f3) and f3 –catenin: this effect may be at thebases of observed motility inhibition of melanoma cell caused by the compound. We have shown that the biscumarin derivative diminish phosphorylation of CHK-2 protein, TOR and P53 an event that is likely be the basis of observed inhibition of melanoma cell survival and tumor growth. Inhibition of cell survival and growth possibly due to the deminish phosphorylation of the chk-2 kinase on Threonine: T68, of TOR on Serine: S2448 of P53 on Serine: S392.

Protective effect of Wuzi Yanzong recipe on testicular DNA damage and apoptosis in natural ageing rats

To study the protective effect of Wuzi Yanzong recipe on testicular DNA damage and apoptosis in natural ageing rats, SPF grade 16-month-old SD male rats were randomly divided into three groups: ageing model group, low and high dose Wuzi Yanzong recipe groups (WZ, 1， 4 g·kg⁻¹). In addition, 2-month-old SD rats were used as adult control group (10 rats in each group). The ageing model group and the adult control group were fed with normal diet for 4 months. Wuzi Yanzong groups received medicated feed for 4 months. After fasting for 12 hours, the rats were sacrificed. Then testis tissues were taken and weighed to calculate the testis index. The change of testicular tissue morphology was observed by HE staining. Expression and localization of DNA damage-associated protein ATR were observed by immunofluorescence. The expressions of DNA damage-related proteins γ-H2AX, Chk1, p-p53 and apoptosis-related proteins Bcl-2 and Bax in testes were detected by Western blot. The apoptosis of testis tissue in rats was detected by using TUNEL. The results showed that as compared with the youth control group, the protein expression levels of γ-H2AX, Chk1, p-p53 and Bax were significantly increased while Bcl-2 protein expression level was significantly decreased intestis tissues of ageing model group. Wuzi Yanzong recipe significantly decreased protein expression levels of γ-H2AX, Chk1, p-p53 and Bax and increased Bcl-2 protein expression level as well as Bcl-2/Bax ratio. Immunofluorescence results showed that Wuzi Yanzong recipe could significantly decrease the ageing-induced ATR, increase in testis tissues. TUNEL results showed that Wuzi Yanzong recipe could significantly attenuate the germ cell apoptosis in testicular tissues. All the above results suggest that Wuzi Yanzong recipe could protect the germ cell in testicular tissues of natural ageing rates from DNA damage and apoptosis, and the mechanism may be associated with regulating p53 signaling pathway.

The ATM and Rad3-Related (ATR) Protein Kinase Pathway Is Activated by Herpes Simplex Virus 1 and Required for Efficient Viral Replication.

The ATM and Rad3-related (ATR) protein kinase and its downstream effector Chk1 are key sensors and organizers of the DNA damage response (DDR) to a variety of insults. Previous studies of herpes simplex virus 1 (HSV-1) showed no evidence for activation of the ATR pathway. Here we demonstrate that both Chk1 and ATR were phosphorylated by 3 h postinfection (h.p.i.). Activation of ATR and Chk1 was observed using 4 different HSV-1 strains in multiple cell types, while a specific ATR inhibitor blocked activation. Mechanistic studies point to early viral gene expression as a key trigger for ATR activation. Both pATR and pChk1 localized to the nucleus within viral replication centers, or associated with their periphery, by 3 h.p.i. Significant levels of pATR and pChk1 were also detected in the cytoplasm, where they colocalized with ICP4 and ICP0. Proximity ligation assays confirmed that pATR and pChk1 were closely and specifically associated with ICP4 and ICP0 in both the nucleus and cytoplasm by 3 h.p.i., but not with ICP8 or ICP27, presumably in a multiprotein complex. Chemically distinct ATR and Chk1 inhibitors blocked HSV-1 replication and infectious virion production, while inhibitors of ATM, Chk2, and DNA-dependent protein kinase (DNA-PK) did not. Together our data show that HSV-1 activates the ATR pathway at early stages of infection and that ATR and Chk1 kinase activities play important roles in HSV-1 replication fitness. These findings indicate that the ATR pathway may provide insight for therapeutic approaches.IMPORTANCE Viruses have evolved complex associations with cellular DNA damage response (DDR) pathways, which sense troublesome DNA structures formed during infection. The first evidence for activation of the ATR pathway by HSV-1 is presented. ATR is activated, and its downstream target Chk1 is robustly phosphorylated, during early stages of infection. Both activated proteins are found in the nucleus associated with viral replication compartments and in the cytoplasm associated with viral proteins. We also demonstrate that both ATR and Chk1 kinase activities are important for viral replication. The findings suggest that HSV-1 activates ATR and Chk1 during early stages of infection and utilizes the enzymes to promote its own replication. The observation may be exploitable for antiviral approaches.

Effects of low-intensity ultrasound combined with low-dose carboplatin in an orthotopic hamster model of tongue cancer: A preclinical study

Low-intensity ultrasound (LIUS) combined with chemotherapy is an innovative modality for cancer treatment, but its effect on orthotopic carcinoma remains unknown. Our previous study revealed that LIUS enhanced the growth inhibitory effects of several chemotherapeutic drugs in nude mice with transplanted tumors. In the present study, we used 7,12-dimethylbenz(alpha)anthracene to induce orthotopic tongue carcinogenesis in hamsters. We used the first-line chemotherapy drug for tongue cancer, carboplatin (CBP) in combination with LIUS to investigate the synergistic effect. The results revealed that LIUS combined with low-dose CBP enhanced the inhibitory effects of CBP on tumor growth, prolonged survival, and did not increase the incidence of side-effects. It also enhanced the inherent DNA damage caused by CBP, suppressed the expression of the DNA repair proteins O6-methylguanine DNA methyltransferase (MGMT) and Chk1, and increased the expression of DNA damage-inducible protein GADD45α. Furthermore, compared with CBP alone, LIUS combined with CBP reduced the expression of cyclin D1 and cyclin B1, induced the expression of caspase-3, cleaved caspase-3, caspase-8, Bax, and Bak, and inhibited the expression of Bcl-2. Examination of clinical samples revealed that MGMT, Chk1, and Gadd45α were higher in OTSCC than in adjacent normal tissue. Hence, our results indicated that LIUS enhanced the ability of low-dose CBP to damage DNA in an orthotopic hamster model of tongue cancer, induced apoptosis, inhibited tumor growth and progression, while it did not increase the toxic side-effects of the drug, suggesting additional clinical benefits for patients treated with the combination of CBP with LIUS.

Sodium fluoride causes hepatocellular S-phase arrest by activating ATM-p53-p21 and ATR-Chk1-Cdc25A pathways in mice.

In this study, experimental pathology, flow cytometry (FCM), quantitative real-time polymerase chain reaction (qRT-PCR), and western blot (WB) were used to evaluate the effects of sodium fluoride (NaF) on hepatocellular cell cycle progression in mice. A total of 240 ICR mice were divided equally into four groups; the experimental groups received 12, 24, or 48 mg/kg NaF intragastrically for 42 days, while the control group received distilled water. Doses of NaF above 12 mg/kg increased the percentage of cells in S phase (S-phase arrest), reduced percentages of cells in G0/G1 or G2/M phase, and activated the ATM-p53-p21 and ATR-Chk1-Cdc25A pathways. Activation of these pathways was characterized by up-regulation of ATM, p53, p21, ATR, and Chk1 mRNA and protein expression, and down-regulation of Cdc25A, cyclin E, cyclin A, CDK2, CDK4, and proliferating cell nuclear antigen (PCNA) mRNA and protein expression. These results indicate that NaF caused S-phase arrest by activating the ATM-p53-p21 and ATR-Chk1-Cdc25A pathways.

The aberrant upstream pathway regulations of CDK1 protein were implicated in the proliferation and apoptosis of ovarian cancer cells

BackgroundUpregulation of Cyclin dependent kinase 1 (CDK1) protein is closely related with the prognosis of several malignant tumors. Chk1-CDC25C-CDK1 signaling and P53-P21WAF1-CDK1 signaling pathways are closely related with the cell cycle G2/M phase regulation. The present study aimed to analyze the relationship between CDK1 and the proliferation and apoptosis of ovarian cancer cells, investigate its molecular mechanism preliminarily.MethodsThe specific short-hair RNA (shRNA) plasmids and negative control plasmid of CDK1, checkpoint kinase 1 (CHK1) and p53 genes were transfected into ovarian cancer SK-OV-3 and OVCAR-3 cells respectively. The expressions of CDK1, CHK1 and p53 mRNA and CDK1, Chk1 and P53 protein were detected by sqRT-PCR and Western blot, levels of phospho-CDK1(Thr14/Tyr15), CyclinB1, phospho-Chk1(ser345), cell division cycle 25C (CDC25C), phospho-CDC25C(ser216), P21WAF1, phospho-P53(ser15), proliferating cell nuclear antigen (PCNA), Ki-67, Bcl-2, Bax, Caspase8, Cleaved-caspase3 and Cytochrome C were examined by Western blot. The cell proliferation was measured by MTT and Trypan blue exclusion assay respectively, the cell cycle phase distribution and cell apoptosis rate were detected by flow cytometry (FCM) assay.ResultsAs results of CDK1 inhibition by shRNA, the cell proliferation was repressed, the cell numbers of G2/M phase and cell apoptosis rate were increased in both SK-OV-3 and OVCAR-3 cells. After knockdown of CDK1, expressions of PCNA, Ki-67 and Bcl-2 protein were downregulated, expressions of Bax, Caspase8, Cleaved-caspase3 and Cytochrome C were upregulated. While knockdown the CHK1 and p53 by shRNA respectively, the similar effects were observed on the cell proliferation, cell cycle phase distribution and apoptosis in both SK-OV-3 and OVCAR-3 cells, as well as the expressions of the proliferation and apoptosis related proteins mentioned above. Moreover, the levels of p-CDK1(Thr14/Tyr15) were increased after either CHK1 inhibition or p53 inhibition.ConclusionsAbnormal activation of CDK1 was implicated in the proliferation and apoptosis regulation of ovarian cancer cells, which might be due to the aberrant regulations of the upstream Chk1-CDC25C and P53-P21WAF1 signaling pathway.

Abstract 5717: PKR promotes EphA2 and other proteins degradation and is predictor of survival in lung cancer

Abstract Relative expression of PKR and EphA2 was a significant predictor of survival in non-small cell lung cancer. To study the PKR-regulated protein, we evaluated expression of 149 proteins in lung cancer cells by reverse-phase protein assay (RPPA) after induction of PKR. Expression of several proteins (EphA2, IRS1, Chk1 and c-Raf and paxillin) was inhibited by PKR. In validating the downregulated proteins by western blot analysis, we observed that PKR reduced EphA2, IRS1, Chk1 and paxillin protein expression. We next investigated the involvement of the proteasomes and lysosomes in PKR-induced protein degradation. Human lung cancer H1299 and A549 cells were transfected with Ad-PKR for 48 h in the presence or absence of the proteasome inhibitor MG132 or lysosome inhibitor (3MA: 3-methyladenine). We observed that MG132 prevented PKR-induced IRS1 and Chk1 degradation, but not PKR-induced EphA2 and paxillin degradation in these cells. However, we found that 3MA prevented PKR-induced EphA2 and paxillin degradation in these cells. These data suggest that PKR is involved in proteasome as well as lysosome function. To study the involvement of autophagy pathway in PKR mediated protein degradation, we evaluated proteins which known involved in autophagy by Western blotting after induction of PKR on these cancer cells. We observed slightly decrease of LC-3, ATG5 and Beclin1 in these cancer cells after induction of PKR. Our data suggest that PKR may directly involve in in lysosome function. Citation Format: Apar Pataer, Ruping Shao, Bulent Ozpolat, Bingliang Fang, Stephen G. Swisher. PKR promotes EphA2 and other proteins degradation and is predictor of survival in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5717. doi:10.1158/1538-7445.AM2017-5717

183 Novel glycomimetics inhibit gly-ldl induced smooth muscle cell calcification via creb

Advanced glycated end-products (AGEs) are known drivers of cardiovascular complications such as vascular calcification, which is currently untreatable, and are increased in diabetic subjects in part due to oxidative stress...

Design, synthesis, characterisation, conformation and biological investigation of N-acyl r-2,c-6-bis (4-methoxyphenyl)-c-3,t-3-dimethylpiperidin-4-ones

In a wide research programme towards the study of piperidin-4-ones with efficient pharmacological effect, a new series of N-acyl r-2,c-6-bis(4-methoxyphenyl)-c-3,t-3-dimethylpiperidin-4-ones 2–5 are synthesized and characterized by IR spectra, 1H, 13C, DEPT - 135 and 2D (COSY and HSQC) NMR and mass spectra. The parent compound 1 prefers to exist in a chair conformation whereas the extracted coupling constant, chemical shifts and estimated dihedral angles show that the N-acyl piperdine-4-ones 2–5 prefer to exist in a distorted boat conformation B1 (with C2 and C5 in prow and stern positions) with coplanar orientation of NCO moiety. The existence of a fast NCO rotational equilibrium between the boat conformations B (I) and B (II) has also been observed. Anti bacterial activity of the above test compounds 1–5 is determined against pseudomonas sp. and salmonella sp. The antioxidant activities are determined by the ABTS, DPPH and superoxide assays. Furthermore, molecular docking studies have been carried out for the compounds 1–5 with target protein CHK1.

Oxoaporphine Metal Complexes (CoII, NiII, ZnII) with High Antitumor Activity by Inducing Mitochondria-Mediated Apoptosis and S-phase Arrest in HepG2

Three new oxoaporphine Co(II), Ni(II) and Zn(II) complexes 1–3 have been synthesized and fully characterized. 1–3 have similar mononuclear structures with the metal and ligand ratio of 1:2. 1–3 exhibited higher cytotoxicity than the OD ligand and cisplatin against HepG2, T-24, BEL-7404, MGC80–3 and SK-OV-3/DDP cells, with IC50 value of 0.23−4.31 μM. Interestingly, 0.5 μM 1–3 significantly caused HepG2 arrest at S-phase, which was associated with the up-regulation of p53, p21, p27, Chk1 and Chk2 proteins, and decrease in cyclin A, CDK2, Cdc25A, PCNA proteins. In addition, 1–3 induced HepG2 apoptosis via a caspase-dependent mitochondrion pathway as evidenced by p53 activation, ROS production, Bax up-regulation and Bcl-2 down-regulation, mitochondrial dysfunction, cytochrome c release, caspase activation and PARP cleavage. Furthermore, 3 inhibited tumor growth in HepG2 xenograft model, and displayed more safety profile in vivo than cisplatin.