Potent Apoptosis Research Articles

Abstract 342: S63845, a novel BH3 mimetic Mcl-1 inhibitor synergizes with midostaurin to induce potent apoptosis in acute myeloid leukemia cells carrying FLT3-ITD mutations

Abstract Myeloid cell leukemia 1 (Mcl-1) is one of the key anti-apoptotic Bcl-2 family proteins that binds and neutralizes pro-apoptotic BIM, BAX and BAK at the mitochondrial outer membrane, preventing cytochrome c release and caspase activation. Selective upregulation of Mcl-1 functionally contributes to resistance of acute myeloid leukemias (AML) with FMS-like tyrosine kinase-3-internal tandem duplications (FLT3-ITD) to chemotherapy (Kasper S. et al. 2012, Blood Cancer J. 2:e60, doi:10.1038/bcj.2012.5). Here we show that a novel Mcl-1 inhibitor S63845 (Kotschy A. et al. 2016, Nature 538, 477-482), has synergistic proapoptotic activity in combination with FLT3-ITD kinase inhibitor midostaurin in pre-clinical models of AML. Our studies demonstrate that S63845 has potent single agent activity in AML cell lines and primary AML samples harboring FLT3-ITD with IC50 values in low nanomolar range. Co-targeting of Mcl-1 and FLT3-ITD with S63845 and midostaurin, respectively, significantly increased apoptosis in FLT3-ITD cells with caspase-3 activation and PARP cleavage occurring rapidly within 6 hours of treatment. Consistent with markedly reduced cell growth and viability, analysis of drug combinations efficacy using Bliss independence model revealed strong synergistic interactions between S63845 and midostaurin in FLT3-ITD cell lines and primary AML samples. Midostaurin caused de-phosphorylation of FLT3-ITD and its downstream targets such as STAT5, AKT and MAPK. This was accompanied by significant downregulation of MAPK-mediated phosphorylation of Mcl-1 at Thr163 required for Mcl-1 stability. Consequently, midostaurin reduced Mcl-1 protein levels, with no major changes in antiapoptotic Bcl-2 or Bcl-XL. Importantly, midostaurin increased expression of pro-apoptotic Bim, which could in turn bind and negate residual Mcl-1 pro-survival activity. Elevated Bim was sustained upon S63845 co-treatment, suggesting that Bim plays functional role in midostaurin/S63845-mediated lethality. Dynamic BH3 profiling showed that midostaurin primed FLT3-ITD cells to Mcl-1 and Bcl-2 inhibitors and facilitated general apoptosis priming in response to Bim peptide. Importantly, given that Mcl-1 is a major contributing factor to resistance of AML to Bcl-2 selective BH3-mimetic venetoclax, S63845/midostaurin treatment induced cell death in venetoclax-resistant FLT3-ITD mutants. In summary, S63845/midostaurin is highly synergistic in FLT3-ITD mutated AML cells including those resistant to venetoclax. In vivo experiments of tolerability and efficacy are ongoing and will be reported. Citation Format: Anna Skwarska, Qi Zhang, Shelley M. Herbrich, Natalia Baran, Ensar Halilovic, Peter Ruvolo, Vivian Ruvolo, Erick Morris, Andrew Wei, Donia Moujalled, Michael Andreff, Marina Konopleva. S63845, a novel BH3 mimetic Mcl-1 inhibitor synergizes with midostaurin to induce potent apoptosis in acute myeloid leukemia cells carrying FLT3-ITD mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 342.

Targeting the IGF1R/PI3K/AKT Pathway Sensitizes Ewing Sarcoma to BET Bromodomain Inhibitors.

Inhibitors of the bromodomain and extra-terminal domain (BET) family proteins modulate EWS-FLI1 activities in Ewing sarcoma. However, the efficacy of BET inhibitors as a monotherapy was moderate and transient in preclinical models. The objective of this study was to identify the mechanisms mediating intrinsic resistance to BET inhibitors and develop more effective combination treatments for Ewing sarcoma. Using a panel of Ewing sarcoma cell lines and patient-derived xenograft lines (PDX), we demonstrated that IGF1R inhibitors synergistically increased sensitivities to BET inhibitors and induced potent apoptosis when combined with BET inhibitors. Constitutively activated AKT significantly protected Ewing sarcoma cells against BET inhibitors, suggesting that IGF1R regulates responsiveness to BET inhibitors mainly through the PI3K/AKT pathway. Although two Ewing sarcoma cell lines were resistant to IGF1R inhibitors, they retained synergistic response to a combination of BET inhibitors and mTOR inhibitors, suggesting that BET proteins, when IGF1R is not functional, cross-talk with its downstream molecules. Furthermore, the combination of a BET inhibitor and an IGF1R inhibitor induced potent and durable response in xenograft tumors, whereas either agent alone was less effective. Taken together, our results suggest that IGF1R and the downstream PI3K/AKT/mTOR kinase cascade mediate intrinsic resistance to BET inhibitors in Ewing sarcoma. These results provide the proof-of-concept for combining BET inhibitors with agents targeting the IGF1R pathway for treating advanced Ewing sarcoma.

CircPRKCI-miR-545/589-E2F7 axis dysregulation mediates hydrogen peroxide-induced neuronal cell injury

Excessive oxidative stress induces significant injury and cytotoxicity to neuronal cells. The current study tested expression and the potential function of the circular RNA PRKCI (circPRKCI) in oxidative stress-injured neuronal cells. In cultured SH-SY5Y neuronal cells, hydrogen peroxide (H2O2) downregulated circPRKCI expression, causing accumulation of miR-545 and miR-589, but reduction of their target, the transcription factor E2F7. Importantly, ectopic overexpression of circPRKCI in SH-SY5Y cells significantly attenuated H2O2-induced cytotoxicity. Conversely, siRNA-mediated knockdown of circPRKCI induced SH-SY5Y cell death and apoptosis. Further studies demonstrated that H2O2-induced cytotoxicity in SH-SY5Y cells was inhibited by miR-545/589 inhibitors, but mimicked by miR-545/589 mimics. Importantly, CRISPR/Cas9-mediated knockout (KO) of E2F7 induced potent SH-SY5Y cell death and apoptosis. Furthermore, transfection of circPRKCI siRNA or miR-545/589 mimics were ineffective in E2F7 KO cells. In the primary human neurons, H2O2 stimulation similarly induced circPRKCI downregulation, miR-545/589 accumulation and E2F7 reduction. Moreover, H2O2-induced death and apoptosis in the primary neurons were significantly inhibited by circPRKCI overexpression or miR-545/589 inhibitors. Taken together, our results show that dysregulation of circPRKCI-miR-545/589-E2F7 axis mediated H2O2-induced neuronal cell injury. Targeting this novel cascade could be a fine strategy to protect neurons from oxidative stress.

Design, synthesis, anticancer evaluation, molecular docking and cell cycle analysis of 3-methyl-4,7-dihydropyrazolo[1,5-a]pyrimidine derivatives as potent histone lysine demethylases (KDM) inhibitors and apoptosis inducers

A novel series of pyrazolo[1,5-a]pyrimidines were synthesized and proved by their spectral and elemental analysis, some elected of the newly synthesized compounds were examined for their cytotoxic activity employing MTT assay on two cancer cell lines (Breast and Hela cancers). Compounds 5, 7e and 7i showed the higher cytotoxicity against two cancer cell lines with (IC50 = 13.91 ± 1.4 and 22.37 ± 1.8 μM/L), (IC50 = 6.56 ± 0.5 and 8.72 ± 0.9 μM/L) and (IC50 = 4.17 ± 0.2 and 5.57 ± 0.4 μM/L) for two cancer cell lines breast and hela respectively, using doxorubicin as a reference drug. The most potent cytotoxic active compounds 5, 7e and 7i presented inhibitory activity against KDM (histone lysine demethylases) with IC50 = 4.05, 1.91 and 2.31 μM, respectively. The most potent KDM inhibitor 7e (IC50 = 1.91 μM) showed to cause cell cycle arrest at G2/M phase by 4 folds than control and induce total apoptotic effect by 10 folds more than control. In silico studies performed on the more potent cytotoxic active compounds 5, 7e and 7i included lipinisk's rule of five. Moreover, molecular docking study was utilized to explore the binding mode of the most active compounds to the target enzyme (PDB-ID: 5IVE). Also, some bioinformatics studies were carried out for compounds 7e and 7i using Swiss ADME (Swiss Institute of bioinformatics 2018).

Methylglyoxal in combination with 5-Fluorouracil elicits improved chemosensitivity in breast cancer through apoptosis and cell cycle inhibition

The anti-carcinogenic effect of Methylglyoxal (MG) is well established. It generally targets malignant cells by affecting glycolysis and mitochondrial respiration with minimum or no toxicity to normal cells. In an initial study we have reported that MG can synergistically act with 5-Fluorouracil (5-FU) to decreases the number of MCF-7 breast cancer cells (Ghosh S, Pal A, Ray M, 2017). This finding prompted us to study the combination effect of MG and 5-FU extensively in both in vitro and in vivo. Induction of cell apoptosis and cell cycle arrest was systematically studied to reveal the mechanisms of synergy between 5-FU and MG. Our present study revealed that MG can synergistically act with 5-FU and can cause cell death via apoptosis and generated reactive oxygen species (ROS) in MCF-7 cells. Combination of 5-FU and MG resulted in more potent apoptosis induction as revealed by fluorescence microscopy using Hoechst 33342. In comparison to single drug treatment, the co-treatment also increased the number of cells in G0/G1 phase by downregulating the expression of CDK4 and CDK6 as compared to single drug treatment. Levels of Caspase 9 and poly (ADP-ribose) polymerase (PARP) were higher in combination treatment as compared to single drug treatment. These results clearly showed that 5-FU is more effective at lower doses in presence of MG in MCF-7 cells. In case of in vivo studies treatment of EAC (Ehrlich Ascites Carcinoma) bearing mice with MG in combination with 5-FU at various doses, demonstrated the same synergistic effect of MG with 5-FU. The combination study also exhibited tumor regression in BALB/c mouse 4T1 breast tumor model as well. We also clearly demonstrated that MG can decrease the cytotoxic side effects of 5-FU as indicated with acute and chronic toxicity studies and other biochemical analyses of blood and histological studies. Taken together, our results revealed that MG could be a potential candidate for combination therapy to reduce the toxicity burden of 5-FU without any toxic impact on host cells.

Synthesis, and evaluation of in vitro and in vivo anticancer activity of 14-substituted oridonin analogs: A novel and potent cell cycle arrest and apoptosis inducer through the p53-MDM2 pathway

A series of novel oridonin derivatives bearing various substituents on the 14-OH position were designed and synthesised. Their antitumour activity was evaluated in vitro against three human cancer cell lines (HCT116, BEL7402, and MCF7). Most tested derivatives showed improved anti-proliferative activity compared to the lead compound oridonin and the positive control drug 5-fluorouracil (5-Fu). Among them, compound C7 (IC50 = 0.16 μM) exhibited the most potent anti-proliferative activity against HCT116 cells; it was about 43- and 155-fold more efficacious than that of oridonin (IC50 = 6.84 μM) and 5-Fu (IC50 = 24.80 μM) in HCT116 cancer cells. Interestingly, the IC50 value of compound C7 in L02 normal cells was 23.6-fold higher than that in HCT116 cells; it exhibited better selective anti-proliferative activity and specificity than oridonin and 5-Fu. Furthermore, compound C7 possibly induced cell cycle arrest and apoptosis by regulating the p53-MDM2 signalling pathway. Notably, C7 displayed more significant suppression of tumour growth than oridonin in colon tumour xenograft models where the tumour growth inhibition rate was 85.82%. Therefore, compound C7 could be a potential lead compound for the development of a novel antitumour agent.

O-GlcNAc Transferase Inhibition Differentially Affects Breast Cancer Subtypes

Post-translational modification of intracellular proteins with a single N-acetylglucosamine sugar (O-GlcNAcylation) regulates signaling, proliferation, metabolism and protein stability. In breast cancer, expression of the enzyme that catalyzes O-GlcNAcylation – O-GlcNAc-transferase (OGT), and the extent of protein O-GlcNAcylation, are upregulated in tumor tissue, and correlate with cancer progression. Here we compare the significance of O-GlcNAcylation in a panel of breast cancer cells of different phenotypes. We find a greater dependency on OGT among triple-negative breast cancer (TNBC) cell lines, which respond to OGT inhibition by undergoing cell cycle arrest and apoptosis. Searching for the cause of this response, we evaluate the changes in the proteome that occur after OGT inhibition or knock-down, employing a reverse-phase protein array (RPPA). We identify transcriptional repressor - hairy and enhancer of split-1 (HES1) - as a mediator of the OGT inhibition response in the TNBC cells. Inhibition of OGT as well as the loss of HES1 results in potent cytotoxicity and apoptosis. The study raises a possibility of using OGT inhibition to potentiate DNA damage in the TNBC cells.

Flavokawain B targets protein neddylation for enhancing the anti-prostate cancer effect of Bortezomib via Skp2 degradation

BackgroundFlavokawain B (FKB) has been identified from kava root extracts as a potent apoptosis inducer for inhibiting the growth of various cancer cell lines, including prostate cancer. However, the molecular targets of FKB in prostate cancer cells remain unknown.MethodsAn in vitro NEDD8 Initiation Conjugation Assay was used to evaluate the neddylation inhibitory activity of FKB. Molecular docking and a cellular thermal shift assay were performed to assess the direct interaction between FKB and the NEDD8 activating enzyme (NAE) complex. Protein neddylation, ubiqutination, stability and expression in cells were assessed with immunoprecipitation and Western blotting methods using specific antibodies. Deletion and site specific mutants and siRNAs were used to evaluate deep mechanisms by which FKB induces Skp2 degradation. Cell growth inhibition and apoptosis induction were measured by MTT, ELISA and Western blotting methods.ResultsFKB inhibits NEDD8 conjugations to both Cullin1 and Ubc12 in prostate cancer cell lines and Ubc12 neddylation in an in vitro assay. Molecular docking study and a cellular thermal shift assay reveal that FKB interacts with the regulatory subunit (i.e. APP-BP1) of the NAE. In addition, FKB causes Skp2 degradation in an ubiquitin and proteasome dependent manner. Overexpression of dominant-negative cullin1 (1–452), K720R mutant (the neddylation site) Cullin1 or the F-box deleted Skp2 that losses its binding to the Skp1/Cullin1 complex causes the resistance to FKB-induced Skp2 degradation, whereas siRNA knock-down of Cdh1, a known E3 ligase of Skp2 for targeted degradation, didn’t attenuate the effect of FKB on Skp2 degradation. These results suggest that degradation of Skp2 by FKB is involved in a functional Cullin1. Furthermore, proteasome inhibitors Bortezomib and MG132 transcriptionally down-regulate the expression of Skp2, and their combinations with FKB result in enhanced inhibitory effects on the growth of prostate cancer cell lines via synergistic down-regulation of Skp2 and up-regulation of p27/Kip1 and p21/WAF1 protein expression. FKB also selectively inhibits the growth of RB deficient cells with high expression of Skp2.ConclusionThese findings provide a rationale for further investigating combination of FKB and Bortezomib for treatment of RB deficient, castration-resistant prostate cancer.

Design, synthesis, molecular docking and biological activity evaluation of some novel indole derivatives as potent anticancer active agents and apoptosis inducers

Reaction of 5-morphilinosulfonylisatin (1) with acetophenones (2a–e) afforded 3-hydroxy-3-substituted-2-oxoindoles 3a-e, when treated with acetic acid the expected 3-phenacylidene-2-oxoindoles 4a-d and 4-hydroxy-5′-(morpholinosulfonyl) spiro [chromene-2, 3′-indolin]-2′-one 6 were obtained. Isatin derivative (1) was stirred with cyano derivatives to produce the arylidines (7a-c), while under reflux condition, it gave pyrrolo[2,3–b]indoles (8, 9). Moreover, istain (1) reacted with pyrazolo-5-one or 3-substituted phenol in presence of malononitrile to afford spiroxindole derivatives (10a,b) and (11a,b). Also, compounds (10a,b) and (11a,b) were obtained through cyclization of (7a) with pyrazolo-5-one or 3-substituted phenol. The obtained compounds were identified by IR, 1H NMR, 13C NMR and elemental analysis. Anticancer activity against three cancer cell lines (HepG-2, HCT-116 and MCF-7) were evaluated using sulforhodamine B assay method. Compounds 4b, 4c, 7a, 7c and 9 showed broad spectrum anticancer activity on the three tested cell lines with IC50 values less than 10 µM. Cell cycle analysis was performed for the most promising derivatives, compounds 4b and 7c arrested HepG-2 cells at G2-M phase, while compounds 7a and 9 accumulated cells at G0-G1 phase, all of them induced apoptosis at priG1 phase in the range of (11.32–19.17%). Additionally compounds 4b, 7a and 9 showed more potent activity against EGFR than Lapatinib, their IC50 values are from 0.019 to 0.026 µM while IC50 of Lapatinib is 0.028 µM. Molecular docking studies were conducted to investigate the binding mode, amino acid interactions and free binding energy of these potent derivatives.

MicroRNA-34a and E4orf4 synergistically promote apoptosis in Hela cells

RNA interference (RNAi) mediated by microRNA (miRNA) is widely utilized to induce apoptosis and further inhibit the proliferation of cancer cells. MiroRNA-34a (miR-34a) is one of the most potent apoptosis inducers by targeting survivin, which is associated with cancer initiation and progression. To further induce apoptosis and inhibit proliferation in Hela cells, the cytokine E4orf4 is included. One of the advantages of E4orf4 is that it can induce apoptosis independent of p53, which is especially useful for p53-mutant cancers. In our study, we successfully constructed a vector co-expressing miR-34a and E4orf4. The vector was transfected into Hela cells and the proliferation, metastasis and apoptosis of Hela cells were evaluated. We further compared the combined use of miR-34a and E4orf4 with pri-miR-34a in the potency of apoptosis induction. It is concluded that miR-34a and E4orf4 have a synergistic impact on Hela cell proliferation, metastasis and apoptosis, providing an efficient tool for further cervical cancer gene therapy.

Aurora kinase and FGFR3 inhibition results in significant apoptosis in molecular subgroups of multiple myeloma

Aberrant expression of proteins involved in cell division is a constant feature in multiple myeloma (MM), especially in high-risk disease. Increasingly, therapy of myeloma is moving towards individualization based on underlying genetic abnormalities. Aurora kinases are important mediators of cell cycle and are up regulated in MM. Functional loss of Aurora kinases results in genetic instability and dysregulated division leading to cellular aneuploidy and growth arrest. We investigated the role of Aurora kinase inhibition in MM, using a small molecule inhibitor A1014907. Low nanomolar A1014907 concentrations induced aneuploidy in MM cell lines independent of underlying cytogenetic abnormalities by inhibiting Aurora Kinases. However, A1014907 induced more pronounced and dose dependent apoptosis in cell lines with t(4;14) translocation. Translocation t(4;14) is observed in about 15% of patients with MM leading to constitutive activation of FGFR3 in two-thirds of these patients. Further investigation of the mechanism of action of A1014907 revealed potent FGFR3 pathway inhibition only in the sensitive cell lines. Thus, our results show that aurora kinase inhibition causes cell cycle arrest and aneuploidy with minimal apoptosis whereas inhibiting both aurora kinase and FGFR3 activity induced potent apoptosis in MM cells. These results support clinical evaluation of A1014907 in MM patients with t(4;14) translocation and/or FGFR3 expression.

G1 phase cell cycle arrest in NSCLC in response to LZ-106, an analog of enoxacin, is orchestrated through ROS overproduction in a P53-dependent manner.

LZ-106, a newly synthetized analog of quinolone, has been shown to be highly effective in non-small cell lung cancer (NSCLC) in both cultured cells and xenograft mouse model with low toxicity, yet the molecular mechanisms still require exploration. Here, we substantiated the involvement of P53 activation in intracellular reactive oxygen species (ROS) generation upon LZ-106 treatment and related P53 to the ROS-induced viability inhibition and apoptosis, which was exhibited in the previous research. P53 was shown to play an indispensable role in the elevated levels of intracellular ROS in LZ-106-treated NSCLC cells through ROS detection. We further identified the anti-proliferation effect of LZ-106 in NSCLC cells through G1 phase cell cycle arrest by cell cycle analysis, with the expression analysis of the key proteins, and discovered that the cell cycle arrest effect is also mediated by induction of ROS in a P53-dependent manner. In addition, the tumor suppression effect exhibited in vivo was demonstrated to be similar to that in vitro, which requires the participation of P53. Thus, LZ-106 is a potent antitumor drug possessing potent proliferation inhibition and apoptosis induction ability through the P53-dependent ROS modulation both in vitro and in vivo.

Abstract 5236: ARV-110: An androgen receptor PROTAC degrader for prostate cancer

Abstract The Androgen Receptor (AR) remains the principal driver of castration-resistant prostate cancer during the transition from a localized to metastatic disease. Most patients initially respond to inhibitors of the AR pathway, but the response is often short-lived. The majority of patients progressing on enzalutamide or abiraterone exhibit genetic alterations in the AR locus, either in the form of amplifications or point mutations in the AR gene. Given these mechanisms of resistance, our goal is to eliminate the AR protein using the PROteolysis TArgeting Chimera (PROTAC) technology. Here we report an orally bioavailable small molecule ARV-110 that leads to ubiquitination and degradation of AR. ARV-110 completely degrades AR in all cell lines tested, with an observed 50% degradation concentration (DC50) < 1 nM. PROTAC-mediated AR degradation suppresses the expression of the AR-target genes PSA and FKBP5, inhibits AR-dependent cell proliferation, and induces potent apoptosis in VCaP cells. ARV-110 degrades clinically relevant mutant AR proteins and retains activity in a high androgen environment. In mouse xenograft studies, greater than 90% AR degradation is observed at a 1 mg/kg PO QD dose. Significant inhibition of tumor growth and AR signaling can be achieved in both an intact and castrate setting. Further, ARV-110 demonstrates in vivo efficacy and reduction of oncogenic Erg protein in a long term, castrate, enzalutamide-resistant VCaP tumor model. DMPK and exploratory toxicology studies show robust oral, dose proportional drug exposure in rodent and non-rodent species. In summary, we report preclinical data on ARV-110, an orally bioavailable androgen receptor PROTAC degrader that demonstrates efficacy in enzalutamide-resistant prostate cancer. Citation Format: Taavi Neklesa, Lawrence B. Snyder, Ryan R. Willard, Nicholas Vitale, Kanak Raina, Jennifer Pizzano, Deborah Gordon, Mark Bookbinder, Jennifer Macaluso, Hanqing Dong, Zheng Liu, Caterina Ferraro, Gan Wang, Jing Wang, Craig M. Crews, John Houston, Andrew P. Crew, Ian Taylor. ARV-110: An androgen receptor PROTAC degrader for prostate cancer [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 5236.

HDAC and Ku70 axis- an effective target for apoptosis induction by a new 2-cyano-3-oxo-1,9-dien glycyrrhetinic acid analogue

Methyl 2-cyano-3,12-dioxo-18β-olean-1,9(11)-dien-30-oate (CDODO-Me, 10d) derived from glycyrrhetinic acid and methyl-2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO-Me) derived from oleanoic acid are potent apoptosis inducers developed to clinical trials. Both compounds have high affinity for reduced glutathione (GSH), which needs to be overcome to improve their target selectivity. We generated a new 10d analogue methyl 2-cyano-3-oxo-18β-olean-1,9(11), 12-trien-30-oate (COOTO, 10e), which retains high apoptosis inducing ability, while displaying decreased affinity for GSH, and explored the acting targets. We found that it induces Noxa level, reduces c-Flip level and causes Bax/Bak activation. Silencing of either Noxa or Bak significantly attenuated apoptosis induction of 10e. We linked these events due to targeting HDAC3/HDAC6 and Ku70 axis. 10e treatment reduced the levels of HDAC3 and HDAC6 with increased DNA damage/repair marker gamma-H2AX (γ-H2AX) and acetylated Ku70. c-Flip dissociates from acetylated Ku70 undergoing degradation, while Bax dissociates from acetylated Ku70 undergoing activation. Silencing of either HDAC3 or HDAC6 enhanced 10e-induced apoptosis. We reveal a new action cascade of this category of compounds that involves targeting of HADC3/6 proteins and Ku70 acetylation.

Pyran-2-one derivatives from Croton crassifolius as potent apoptosis inducers in HepG2 cells via p53-mediated Ras/Raf/ERK pathway

Chemical investigation of the roots of Croton crassifolius led to the isolation of five pyran-2-one derivatives, including two brand new compounds (1–2), one new natural product (3) and two known compounds (4–5). Their structures and absolute configurations were established by spectroscopic analyses as well as comparison between the calculated optical rotation (OR) values with the experimental data. Interestingly, the new compound 1 showed an unusual negative chemical shift at H-11. It is well known that negative chemical shift values of 1H NMR spectrum are extremely rare in natural products. Such a negative chemical shift of 1H NMR spectrum was reproduced by density functional theory (DFT) calculations and explained by the shielding effect from the pyran-2-one ring over the hydrogen atom in the 3D conformations. Then, MTT assay was applied to evaluate the cytotoxicity of the isolated compounds (1–5) against two liver cancer cell lines (HepG2 and MHCC97H). The results suggested that compound 1 displayed the highest cytotoxicity with an IC50 value of 9.8 μM against HepG2 cells. Moreover, there was no obvious cytotoxicity of compounds 1–5 on normal liver cell line LO2. Furthermore, the mechanism of apoptosis induction in compound 1-treated HepG2 cells was investigated. The results showed that compound 1 could induce apoptosis via p53-mediated Ras/Raf/ERK suppression in HepG2 cells.

Design, in silico prioritization and biological profiling of apoptosis-inducing lactams amenable by the Castagnoli-Cushman reaction

Five lactam chemotypes amenable by the Castagnoli-Cushman reaction of imines and cyclic anhydrides have been investigated for their ability to activate p53 tumor suppressing transcription factor thus induce apoptosis in p53+ cancer cells. A virtual library of 1.07 million chemically diverse compounds based on these scaffolds was subjected to in silico screening first. The compounds displaying high docking score were visually prioritized to identify the best-fitting compounds, i. e. the ones which adequately mimic the interactions of clinical candidate inhibitor Nutlin-3a. These 38 compounds were synthesized and tested for apoptosis induction in p53+ H116 cancer cells to identify 9 potent apoptosis-inducers (two of them exceeding the activity of Nutlin-3a) which belonged to four different chemotypes. The activation of p53 involved in the proapoptotic activity observed was supported by effective induction of EGFP expression in human osteocarcinoma U2OS-pLV reporter cell line. Moreover, the two most potent apoptosis inducers displayed antiproliferative profile identical to several known advanced p53 activators: they inhibited the growth of p53+/+ HCT116 cells in much lower concentration range compared to p53−/− HCT116 cells.

13. Kajjali as a potent anti-leukemic and apoptosis inducing ayurvedic drug in chronic myeloid leukemic cells; K562 cell line

13. Kajjali as a potent anti-leukemic and apoptosis inducing ayurvedic drug in chronic myeloid leukemic cells; K562 cell line

An oral androgen receptor PROTAC degrader for prostate cancer.

381 Background: The Androgen Receptor (AR) remains the principal driver of castration-resistant prostate cancer during the transition from a localized to metastatic disease. Most patients initially respond to inhibitors of the AR pathway, but the response is often short-lived. The majority of patients progressing on enzalutamide or abiraterone exhibit genetic alterations in the AR locus, either in the form of amplifications or point mutations in the AR gene. Given these mechanisms of resistance, our goal is to eliminate the AR protein using the PROteolysis TArgeting Chimera (PROTAC) technology. Methods: Here we report an orally bioavailable small molecule AR PROTAC that leads to ubiquitination and degradation of AR. This molecule has been characterized in in vitro degradation and functional assays, DMPK, toxicology and preclinical efficacy studies. Results: This AR PROTAC completely degrades AR in all cell lines tested, with an observed 50% degradation concentration (DC50) < 1 nM. PROTAC-mediated AR degradation suppresses the expression of the AR-target gene PSA, inhibits AR-dependent cell proliferation, and induces potent apoptosis in VCaP cells. The AR PROTAC degrades all clinically relevant mutant AR proteins and retains activity in a high androgen environment. In mouse xenograft studies, greater than 90% AR degradation is observed at a 1 mg/kg PO QD dose. Significant inhibition of tumor growth and AR signaling can be achieved in both an intact and castrate setting. Further, the AR PROTAC demonstrates in vivo efficacy and reduction of oncogenic Erg protein in a long term, castrate, enzalutamide-resistant VCaP tumor model. DMPK and exploratory toxicology studies show robust oral, dose proportional drug exposure in rodent and non-rodent species. Conclusions: In summary, we report preclinical data on an orally bioavailable AR PROTAC degrader that demonstrates efficacy in enzalutamide-resistant prostate cancer.

Structure-dependent induction of apoptosis by hepatotoxic pyrrolizidine alkaloids in the human hepatoma cell line HepaRG: Single versus repeated exposure

Pyrrolizidine alkaloids (PA) are secondary plant compounds. PA intoxication in humans causes severe acute and chronic hepatotoxicity. However, the molecular mechanisms of PA hepatotoxicity in humans are not well understood yet.Therefore, we investigated cell death parameters in human HepaRG cells following either single (24 h) or repeated dose treatment (14 d) with structurally different PA of the retronecine (echimidine, senecionine), heliotridine (heliotrine), and otonecine type (senkirkine). After 24 h of exposure only retronecine-type PA were cytotoxic in HepaRG cells and induced apoptosis indicated by a loss of membrane asymmetry, disruption of the mitochondrial membrane potential, and increased pro-caspase and PARP cleavage. In contrast, after 14 d all four PA exerted the aforementioned effects. Furthermore, the apoptotic events caspase 3, 8 and 9 activation as well as nuclear condensation and DNA fragmentation were only detected for the retronecine-type PA after single exposure (6 h).Overall, our studies revealed a time- and structure-dependent apoptosis after PA exposure, suggesting that retronecine-type PA seem to be more potent apoptosis inducers than heliotridine- or otonecine-type PA. Furthermore, our results suggest that PA-induced apoptosis in HepaRG cells occur most probably by involving both, the extrinsic death receptor pathway as well as the intrinsic mitochondrial pathway.

TGF-β transactivates EGFR and facilitates breast cancer migration and invasion through canonical Smad3 and ERK/Sp1 signaling pathways.

Transforming growth factor‐beta (TGF‐β) functions as a potent proliferation inhibitor and apoptosis inducer in the early stages of breast cancer, yet promotes cancer aggressiveness in the advanced stages. The dual effect of TGF‐β on cancer development is known as TGF‐β paradox, and the remarkable functional conversion of TGF‐β is a pivotal and controversial phenomenon that has been widely investigated for decades. This phenomenon may be attributed to the cross talk between TGF‐β signaling and other pathways, including EGF receptor (EGFR) signaling during cancer progression. However, the underlying mechanism by which TGF‐β shifts its role from a tumor suppressor to a cancer promoter remains elusive. In this study, TGF‐β is positively correlated with EGFR expression in breast cancer tissues, and a functional linkage is observed between TGF‐β signaling and EGFR transactivation in breast cancer cell lines. TGF‐β promotes the migration and invasion abilities of breast cancer cells, along with the increase in EGFR expression. EGFR is also essential for TGF‐β‐induced enhancement of these abilities of breast cancer cells. Canonical Smad3 signaling and ERK/Sp1 signaling pathways mediate TGF‐β‐induced EGFR upregulation. Hence, our study provided insights into a novel mechanism by which TGF‐β supports breast cancer progression.