Dose-dependent Growth Arrest Research Articles

The H2Valdien derivatives regulate the epithelial-mesenchymal transition of hepatoma carcinoma cells through the Hedgehog signaling pathway.

This research delves into the influence of H2Valdien derivatives on the proliferation, migration, and apoptosis induction in hepatoma carcinoma cells (HepG2, Huh-7, and SMMC-7721), with a specific emphasis on inhibiting epithelial-mesenchymal transition (EMT) through modulation of the Hedgehog (Hh) signaling pathway. Utilizing the cell counting kit-8 method, flow cytometry, TUNEL assay, wound healing, and transwell assays, we observed a dose-dependent growth arrest and apoptosis induction in HepG2, Huh-7, and SMMC-7721 cells. Notably, H2Valdien derivatives exhibited a capacity to reduce migration and invasion, impacting the expression of EMT-associated proteins such as N-cadherin, vimentin, and E-cadherin. Mechanistically, these derivatives demonstrated the inhibition of the Hh signaling pathway by inactivating Sonic Hh (Shh) and smoothened proteins. This study underscores the robust antiproliferative and apoptosis-inducing effects of H2Valdien derivatives on hepatoma carcinoma cells and elucidates their regulatory role in EMT through modulation of the Hh signaling pathway, providing valuable insights for potential therapeutic interventions.

Synthesis and biological assessment of indole derivatives containing penta-heterocycles scaffold as novel anticancer agents towards A549 and K562 cells

Herein, a new series of 2-chloro-N-(5-(2-oxoindolin-3-yl)-4H-pyrazol-3-yl) acetamide derivatives containing 1,3,4-thiadiazole (10a–i) and 4H-1,2,4-triazol-4-amine (11a–r) moiety was designed, synthesised as novel anticancer agents. The antiproliferative activity values indicated that compound 10 b stood as the most potent derivative with IC50 values of 12.0 nM and 10 nM against A549 and K562 cells, respectively. Mechanism investigation and docking studies of 10 b indicated that it possessed good apoptosis characteristic and dose-dependent growth arrest of A549 and K562 cells, blocked cell cycle into G2/M phase. Interestingly, 10 b suppressed the growth of A549 and K562 cells via modulation of EGFR and p53-MDM2 mediated pathway.

The mammalian target of rapamycin protein expression in human granulosa cell tumors

Objective:To investigate the role of mammalian target of rapamycin (mTOR) in human granulosa cell ovarian tumors and the therapeutic effect of rapamycin in COV434 mitotic granulosa cell lines.Material and Methods:A retrospective evaluation of the medical records and pathologic sections of patients with granulosa cell ovarian carcinoma was performed. mTOR and p-mTOR expression was immunohistochemically investigated. A COV434 cell culture were treated with 0.5, 1, 2, and 5 μM rapamycin. Real-time growth curve analysis via xCELLigence system and apoptotic cell analysis via YO-PRO™-1 Iodide were performed to assess the therapeutic effect of rapamycin on cancer cells.Results:A total of twenty patients were evaluated. mTOR staining was detected in 18 (90%) patients. Mild, moderate, intense, and very intense staining was observed in three (15%), eight (40%), six (30%), and one (5%) sample, respectively. The mean mTOR staining ratio was 59±41%. P-mTOR staining was observed in two (10%) patients. One (5%) patient had 5% staining, and one (5%) patient had 100% staining for p-mTOR. Both of the latter patients had very intense staining. Rapamycin caused a dose-dependent growth arrest and induced apoptosis in COV434 mitotic granulosa cells. The real-time growth curves of the cells treated with these drugs were distinguished by a marked reduced slope after exposure for several hours, indicating a rapid onset of apoptosis. Live/dead cell analysis with YO-PRO-1 staining showed that rapamycin induced apoptosis in 24% of the cells when used at 1 μM concentration, whereas the rate increased to 61% and 72% when the cells were treated with 2 μM and 5 μM rapamycin, respectively.Conclusion:mTOR expression is observed in various degrees in 90%, and p-mTOR expression is observed in only 10% of patients with granulosa cell ovarian carcinoma. Rapamycin caused a dose-dependent growth arrest and apoptosis in COV434 mitotic granulosa cells.

Bioreduction of toxicity influenced by bioactive molecules secreted under metal stress by Azotobacter chroococcum.

Heavy metal pollution destruct soil microbial compositions and functions, plant's performance and subsequently human health. Culturable microbes among many metal abatement strategies are considered inexpensive, viable and environmentally safe. In this study, nitrogen fixing bacterial strain CAZ3 recovered from chilli rhizosphere tolerated 100, 1000 and 1200 µg mL-1 of cadmium, chromium and nickel, respectively and was identified as Azotobacter chroococcum by 16S rDNA sequence analysis. Under metal stress, cellular morphology of A. chroococcum observed under SEM was found distorted and shrinkage of cells was noticed when grown with 50 µg mL-1 of Cd (cell size 1.7 µm) and 100 of µg mL-1 Ni (cell size 1.3 µm) compared to untreated control (cell size 1.8 µm). In the presence of 100 µg mL-1 of Cr, cells became elongated and measured 1.9 µm in size. Location of metals inside the cells was revealed by EDX. A dose dependent growth arrest and consequently the death of A. chroococcum cells was revealed under CLSM. A. chroococcum CAZ3 secreted 320, 353 and 133 µg EPS mL-1 when grown with 100 µg mL-1 each of Cd, Cr and Ni, respectively. The EDX revealed the presence of 0.4, 0.07 and 0.24% of Cd, Cr and Ni, respectively within EPS extracted from metal treated cells. Moreover, a dark brown pigment (melanin) secreted by A. chroococcum cells under metal pressure displayed tremendous metal chelating activity. The EDX spectra of melanin extracted from metal treated cells of A. chroococcum CAZ3 displayed 0.53, 0.22 and 0.12% accumulation of Cd, Cr and Ni, respectively. The FT-IR spectra of EPS and melanin demonstrated stretching vibrations and variations in surface functional groups of bacterial cells. The C-H stretching of CH3 in fatty acids and CH2 groups, stretching of N-H bond of proteins and O-H bond of hydroxyl groups caused the shifting of peaks in the EPS spectra. Similar stretching vibrations were recorded in metal treated melanin which involved CHO, alkyl, carboxylate and alkene groups resulting in significant peak shifts. Nuclear magnetic resonance (NMR) spectrum of EPS extracted from A. chroococcum CAZ3 revealed apparent peak signals at 4.717, 9.497, 9.369 and 9.242 ppm. However, 1H NMR peaks were poorly resolved due largely to the impurity/viscosity of the EPS. The entrapment of metals by EPS and melanin was confirmed by EDX. Also, the induction and excretion of variable amounts of metallothioneins (MTs) by A. chroococcum under metal pressure was interesting. Conclusively, the present findings establish- (i) cellular damage due to Cd, Cr and Ni and (ii) role of EPS, melanin and MTs in adsorption/complexation and concurrently the removal of heavy metals. Considering these, A. chroococcum can be promoted as a promising candidate for supplying N efficiently to plants and protecting plants from metal toxicity while growing under metal stressed environment.

FORMULATION AND DEVELOPMENT OF KETOROLAC TROMETHAMINE OPHTHALMIC SOLUTION

An acetic acid derivative ketorolac tromethmine has found its applicability in both gram positive and gram negative bacterial ocular infection and used commonly associated with multiple doses. Ophthalmic medication stored in multiple dose containers is required by the U.S. Food and Drug Administration to contain a preservative so that patients are provided with microbe free medication. Benzalkonium chloride in concentrations from 0.1% to 0.0001% induced dose-dependent growth arrest and conjunctiva epithelial cell death, either delayed or immediately after administration. In such case, a preservative Benzalkonium chloride must be used within reasonable bound. Benzalkonium chloride can provide more help than harm. Hence the present study focusing on to formulate a formulation for ketorolac tromethmine (0.5%) ophthalmic solution using different concentration of Benzalkonium chloride as preservative. Keywords: Ketorolac tromethamine, Ophthalmic, benzalkonium chloride, conjunctiva

Synergistic antitumor activity of gemcitabine combined with triptolide in pancreatic cancer cells.

Pancreatic cancer is a fatal human malignancy associated with an exceptionally poor prognosis. Novel therapeutic strategies are urgently required to treat this disease. In addition to immunosuppressive activity, triptolide possesses strong antitumor activity and synergistically enhances the antitumor activities of conventional chemotherapeutic drugs in preclinical models of pancreatic cancer. The present study investigated the antitumor effects of triptolide in pancreatic cancer cells, either in combination with gemcitabine, or alone. The pancreatic cancer BxPC-3 and PANC-1 cell lines were treated with triptolide, which resulted in time- and dose-dependent growth arrest. When incorporated into a sequential schedule, triptolide synergistically increased gemcitabine-induced cell growth inhibition and apoptosis, in addition to the cooperative regulation of B-cell lymphoma 2 family proteins and loss of mitochondrial membrane potential. Furthermore, triptolide enhanced gemcitabine-induced S phase arrest and DNA double-strand breaks, possibly through checkpoint kinase 1 suppression. The results of the present study suggest that triptolide has therapeutic potential for the treatment of pancreatic cancer, particularly when administered in combination with gemcitabine.

Abstract 2296: An isoform of BARD1, associated with many types of cancer, is a driver of oncogenesis by inducing telomere aberrations in vitro and in vivo

Abstract BARD1 has tumor suppressor functions by binding to BRCA1 and to p53 via RING finger and ankyrin repeats, respectively. The BARD1-BRCA1 heterodimer has E3 ligase activity, and the BARD1-p53 interaction promotes apoptosis. The expression of N-terminally truncated RING-less BARD1 isoforms, however, was correlated with poor prognosis in various cancers. We performed overexpression experiments with various isoforms of BARD1 and found that BARD1δ, lacking RING and ANK regions, induces cell cycle arrest, multipolar mitotic spindles, genomic instability, and telomere aberrations. Co-localization studies and interaction assays in HeLa, MCF7, or HEK 293 cells, using tagged BARD1δ and full length (FL) BARD1, showed that the BRCT domains, present in BARD1δ and FL BARD1, interact with centrosome binding proteins and telomere binding proteins. BARD1δ overexpressing cells showed multipolar spindles and telomere alterations. Similar telomere alterations were observed in cells with reduced expression of FL BARD1 by siRNA. This is consistent with the observed distinct telomeric abnormalities in blood cells of patients with a BARD1 germline mutation that causes translation of a truncated protein lacking the BRCT domains. CRE-inducible BARD1δ transgenic mice showed dose-dependent growth arrest and tumor formation in various organs. These in vitro and in vivo observations suggest that BARD1δ plays a significant role in tumorigenesis by inducing genomic and telomere instability. Citation Format: Maxim Pilyugin, Pierre-Alain Andre, Magdalena Ratajska, Irmgard Irminger-Finger. An isoform of BARD1, associated with many types of cancer, is a driver of oncogenesis by inducing telomere aberrations in vitro and in vivo. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2296. doi:10.1158/1538-7445.AM2015-2296

Identification Of The Ki-1 Antigen (CD30) As a Novel Marker and Potential Therapeutic Target In Neoplastic Mast Cells In Advanced Systemic Mastocytosis

Systemic mastocytosis (SM) is a hematologic neoplasm characterized by abnormal expansion and accumulation of neoplastic mast cells (MC) in various organs, including the bone marrow, skin, liver, spleen and gastrointestinal tract. In a majority of all patients, the transforming KIT mutation D816V is detectable. The clinical picture and prognosis in SM vary, depending on the variant of SM and the presence of an associated hematologic non-MC-lineage disease (AHNMD). The WHO classification discriminates between indolent SM (ISM), SM-AHNMD, aggressive SM (ASM) and MC leukemia (MCL). Recent data suggest that neoplastic MC in ASM and MCL express substantial amounts of cytoplasmic Ki-1 (CD30), a lymphoid antigen otherwise expressed in neoplastic cells in anaplastic large cell lymphoma and Hodgkin lymphoma, where CD30 serves as a therapy target. In the present study, we examined the expression of CD30 in various human MC-lines (HMC-1, MCPV) and primary neoplastic MC in patients with ISM (n=20) and advanced SM (ASM/MCL; n=10) and asked whether CD30 may serve as potential therapeutic target in SM. We found that CD30 is expressed abundantly in the cytoplasm of neoplastic MC in ASM and MCL in almost all patients, whereas in a majority of patients with ISM, MC expressed only low amounts or did not express cytoplasmic CD30. As assessed by flow cytometry, neoplastic MC in SM were also found to express cell surface CD30. In contrast to cytoplasmic expression, no clear correlation was found between the type of SM and CD30 surface expression on MC. Notably, MC expressed surface CD30 in 8/9 ISM patients and in 2/6 ASM/MCL patients. The immature human RAS-transformed MCL line MCPV (KIT D816V negative) also expressed cell surface CD30, whereas the MCL line HMC-1.1 (lacking KIT D816V) expressed only low levels, and the HMC-1.2 subclone (KIT D816V+) was found to stain CD30 negative. To examine whether CD30 may serve as a therapy target in SM, we applied brentuximab vedotin (provided by Millennium: The Takeda Oncology Company, Cambridge, MA, USA), which is an antibody-drug conjugate consisting of a chimeric anti-CD30 antibody and the microtuble inhibitor monomethyl auristatin E (MMAE). Brentuximab vedotin has recently been described to induce dose-dependent growth arrest in human CD30+ lymphoblastic cell lines. In the present study, brentuximab vedotin was found to inhibit the proliferation of MCPV and HMC-1 cells in a dose-dependent manner, with lower IC50 values found in CD30+ MCPV and HMC-1.1 cells (5 µg/ml) than in CD30− HMC-1.2 cells (10 µg/ml). As assessed by AnnexinV/PI staining and staining for active-caspase-3, brentuximab vedotin also induced dose-dependent apoptosis in CD30+ MCPV and HMC-1.1 cells, but did not induce substantial apoptosis in CD30− HMC-1.2 cells. Brentuximab vedotin was also found to induce growth inhibition and apoptosis in the CD30+ canine-mastocytoma cell line C2. We next examined the effects of brentuximab vedotin on in vitro survival (apoptosis) of primary neoplastic MC in patients with CD30− SM (n=3) and in patients with CD30+ SM (n=3). In these experiments, brentuximab vedotin was found to induce dose-dependent apoptosis at pharmacologically relevant concentrations in neoplastic MC in patients with CD30+ SM, whereas no effects were seen in patients with CD30− SM (Figure). Finally, we examined the effects of a drug combination consisting of brentuximab vedotin and the KIT D816V targeting drug PKC412 (midostaurin). We found that both drugs synergize with each other in inhibiting the in vitro proliferation of CD30+ MCPV cells. In conclusion, our data provide evidence that the target-antigen CD30 is expressed on the surface of neoplastic MC in patients with indolent and advanced SM. In addition, our data show that the CD30-targeting antibody brentuximab vedotin induces growth arrest and apoptosis in neoplastic MC and synergizes with midostaurin in inhibiting the growth of CD30+ neoplastic MC. Whether these effects also occur in vivo in patients with advanced mastocytosis remains to be determined in clinical trials. [Display omitted] Neoplastic MC from patients with CD30− SM (n=3, grey bars) and CD30+ SM (n=3, black bars) were incubated in control medium (Co) or in various concentrations of brentuximab vedotin (37°C). After 96 hours, the percentage of AnnexinV+ viable DAPI-negative MC was determined by flow cytometry. Results represent the mean±S.D. of 3 independent experiments. Asterisk: p<0.05 compared to control. Disclosures:Sotlar:Nanostring: Honoraria; Novartis: Consultancy. Reiter:Novartis: Consultancy, Honoraria. Horny:Novartis: Consultancy, Honoraria. Valent:Novartis: Consultancy, Honoraria, Research Funding.

Modelling The Influence Of Diet On APL Identifies Insulin-Growth Factor 1 As A Central Mediator and Provides A Mechanistic Rationale For Therapeutic Weight Loss

BackgroundWe (Breccia et al, Blood 2012) recently reported that risk and prognosis of Acute Promyelocytic Leukemia (APL) is strongly affected by an elevated body mass index (BMI). In our cohort, overweight/obese patients had a 3-fold higher cumulative incidence of relapse at 5 years (31,6% vs 11.2%, p=0.029) and BMI was found to be an independent prognostic factor at multivariate analysis. As the prevalence of overweight/obesity increases in the Western world, it becomes imperative to understand which molecular mechanisms mediate the interaction between systemic metabolism and APL, and cancer in general. Importantly, it remains to be proven that dietary interventions aimed at weight loss can provide any clinical benefit for cancer patients. Mouse models of leukemia provide a tractable system to address such questions experimentally. MethodsWe employed the well-established Cathepsin G/PML-RARa knockin (PRKI) mouse model to reproduce and investigate the effect of diet-induced obesity (DIO) and caloric restriction (CR) on APL. ResultsDIO strongly accelerated the time to leukemic death in PRKI mice, with a median survival of 282 days vs 332 days in standard diet (SD)-fed mice (HR=2.7, p=0.006), and brought penetrance of leukemia from 61% in SD to 100%. To test the idea that weight loss can be used for therapeutic purpose, we transplanted secondary APLs into mice fed either SD or 30% CR. CR dramatically improved survival (median 23.5 vs 16 days in SD, HR=5.5, p=0.0021), with a small group of mice surviving for extended time (>30 days) with reduced disease burden. CR leads to >50% drop in circulating levels of insulin-like growth factor 1 (IGF1). In vitro, APL cell lines were particularly sensitive to IGF1, which even at low doses (1 ng/ml) increased cell proliferation and triggered full activation of the downstream cascade, engaging all main components of the AKT/FOXO, mTOR and ERK pathways. IGF1 receptor inhibition by antibody or small molecules led to dose-dependent growth arrest, suggesting a potential therapeutic target. Restoration of IGF1 in leukemic CR mice accelerated time to death, partially reversing the beneficial effect of CR and showing that systemic IGF1 reduction is at least in part responsible for the therapeutic effect of CR. On the other hand, treatment with IGF1 receptor inhibitors led to small and non-significant improvement in mortality, with important metabolic toxicity characterized by hyperglycemia and hyperinsulinemia. Because of the ubiquitous expression of the Igf1r, receptor blockade through pharmacological means is unlikely to be effective due to a narrow therapeutic range. ConclusionWe describe what, to our knowledge, is the first experimental system to model the effects of systemic metabolic alterations on spontaneous myeloid leukemia. We show that weight gain through increased fat intake acts as a strong promoter in leukemogenesis; we identify the IGF1 pathway as a central mediator between metabolism and leukemia, and provide a molecular rationale for promoting IGF1-reducing dietary interventions with therapeutic scope. Disclosures:No relevant conflicts of interest to declare.

Panobinostat Synergistically Enhances the Cytotoxic Effects of Cisplatin, Doxorubicin or Etoposide on High-Risk Neuroblastoma Cells

High-risk neuroblastoma remains a therapeutic challenge with a long-term survival rate of less than 40%. Therefore, new agents are urgently needed to overcome chemotherapy resistance so as to improve the treatment outcome of this deadly disease. Histone deacetylase (HDAC) inhibitors (HDACIs) represent a novel class of anticancer drugs. Recent studies demonstrated that HDACIs can down-regulate the CHK1 pathway by which cancer cells can develop resistance to conventional chemotherapy drugs. This prompted our hypothesis that combining HDACIs with DNA damaging chemotherapeutic drugs for treating neuroblastoma would result in enhanced anti-tumor activities of these drugs. Treatment of high-risk neuroblastoma cell lines with a novel pan-HDACI, panobinostat (LBH589), resulted in dose-dependent growth arrest and apoptosis in 4 high-risk neuroblastoma cell lines. Further, the combination of panobinostat with cisplatin, doxorubicin, or etoposide resulted in highly synergistic antitumor interactions in the high-risk neuroblastoma cell lines, independent of the sequence of drug administration. This was accompanied by cooperative induction of apoptosis. Furthermore, panobinostat treatment resulted in substantial down-regulation of CHK1 and its downstream pathway and abrogation of the G2 cell cycle checkpoint. Synergistic antitumor interactions were also observed when the DNA damaging agents were combined with a CHK1-specific inhibitor, LY2603618. Contrary to panobinostat treatment, LY2603618 treatments neither resulted in abrogation of the G2 cell cycle checkpoint nor enhanced cisplatin, doxorubicin, or etoposide-induced apoptosis in the high-risk neuroblastoma cells. Surprisingly, LY2603618 treatments caused substantial down-regulation of total CDK1. Despite this discrepancy between panobinostat and LY2603618, our results indicate that suppression of the CHK1 pathway by panobinostat is at least partially responsible for the synergistic antitumor interactions between panobinostat and the DNA damaging agents in high-risk neuroblastoma cells. The results of this study provide a rationale for clinical evaluation of the combination of panobinostat and cisplatin, doxorubicin, or etoposide for treating children with high-risk neuroblastoma.

Class I and Class II Histone Deacetylases Are Potential Therapeutic Targets for Treating Pancreatic Cancer

BackgroundPancreatic cancer is a highly malignant disease with an extremely poor prognosis. Histone deacetylase inhibitors (HDACIs) have shown promising antitumor activities against preclinical models of pancreatic cancer, either alone or in combination with chemotherapeutic agents. In this study, we sought to identify clinically relevant histone deacetylases (HDACs) to guide the selection of HDAC inhibitors (HDACIs) tailored to the treatment of pancreatic cancer.MethodologyHDAC expression in seven pancreatic cancer cell lines and normal human pancreatic ductal epithelial cells was determined by Western blotting. Antitumor interactions between class I- and class II-selective HDACIs were determined by MTT assays and standard isobologram/CompuSyn software analyses. The effects of HDACIs on cell death, apoptosis and cell cycle progression, and histone H4, alpha-tubulin, p21, and γH2AX levels were determined by colony formation assays, flow cytometry analysis, and Western blotting, respectively.ResultsThe majority of classes I and II HDACs were detected in the pancreatic cancer cell lines, albeit at variable levels. Treatments with MGCD0103 (a class I-selective HDACI) resulted in dose-dependent growth arrest, cell death/apoptosis, and cell cycle arrest in G2/M phase, accompanied by induction of p21 and DNA double-strand breaks (DSBs). In contrast, MC1568 (a class IIa-selective HDACI) or Tubastatin A (a HDAC6-selective inhibitor) showed minimal effects. When combined simultaneously, MC1568 significantly enhanced MGCD0103-induced growth arrest, cell death/apoptosis, and G2/M cell cycle arrest, while Tubastatin A only synergistically enhanced MGCD0103-induced growth arrest. Although MC1568 or Tubastatin A alone had no obvious effects on DNA DSBs and p21 expression, their combination with MGCD0103 resulted in cooperative induction of p21 in the cells.ConclusionOur results suggest that classes I and II HDACs are potential therapeutic targets for treating pancreatic cancer. Accordingly, treating pancreatic cancer with pan-HDACIs may be more beneficial than class- or isoform-selective inhibitors.

Destabilization of ERBB2 Transcripts by Targeting 3′ Untranslated Region Messenger RNA Associated HuR and Histone Deacetylase-6

In addition to repressing ERBB2 promoter function, histone deacetylase (HDAC) inhibitors induce the accelerated decay of mature ERBB2 transcripts; the mechanism mediating this transcript destabilization is unknown but depends on the 3' untranslated region (UTR) of ERBB2 mRNA. Using ERBB2-overexpressing human breast cancer cells (SKBR3), the mRNA stability factor HuR was shown to support ERBB2 transcript integrity, bind and endogenously associate with a conserved U-rich element within the ERBB2 transcript 3' UTR, coimmunoprecipitate with RNA-associated HDAC activity, and colocalize with HDAC6. HDAC6 also coimmunoprecipitates with HuR in an RNA-dependent manner and within 6 hours of exposure to a pan-HDAC inhibitor dose, that does not significantly alter cytosolic HuR levels or HuR binding to ERBB2 mRNA. Cellular ERBB2 transcript levels decline while remaining physically associated with HDAC6. Knockdown of HDAC6 protein by small interfering RNA partially suppressed the ERBB2 transcript decay induced by either pan-HDAC or HDAC6-selective enzymatic inhibitors. Three novel hydroxamates, ST71, ST17, and ST80 were synthesized and shown to inhibit HDAC6 with 14-fold to 31-fold greater selectivity over their binding and inhibition of HDAC1. Unlike more potent pan-HDAC inhibitors, these HDAC6-selective inhibitors produced dose-dependent growth arrest of ERBB2-overexpressing breast cancer cells by accelerating the decay of mature ERBB2 mRNA without repressing ERBB2 promoter function. In sum, these findings point to the therapeutic potential of HuR and HDAC6-selective inhibitors, contrasting ERBB2 stability effects induced by HDAC6 enzymatic inhibition and HDAC6 protein knockdown, and show that ERBB2 transcript stability mechanisms include exploitable targets for the development of novel anticancer therapies.

Growth inhibition and differentiation of human breast cancer cells by the PAFR antagonist WEB-2086

WEB-2086 – an antagonist of platelet-activating factor receptor (PAFR) with known anti-inflammatory, antiangiogenic and antileukaemic properties – also proved to inhibit the proliferation in human solid tumour cell lines of different histology, and with much higher efficacy than in normal fibroblasts. A detailed analysis of WEB-2086 anticancer activity was then performed focusing on breast adenocarcinoma MCF-7 and MDA-MB-231 cells. WEB-2086-treated cells, either expressing (MCF-7) or unexpressing (MDA-MB-231) the oestrogen receptor (ER)α, underwent a dose-dependent growth arrest (IC50=0.65±0.09 and 0.41±0.07 mM, respectively) and accumulation in G0–G1 phase. WEB-2086 also induced morphological and functional changes typical of mature mammary phenotype including (i) cell enlargement and massive neutral lipid deposition (best accomplished in MCF-7 cells); (ii) decrease in motility and active cathepsin D levels (mainly observed in highly invasive MDA-MB-231 cells). The expression of ERα was neither increased nor reactivated in treated MCF-7 or MDA-MB-231 cells, respectively. WEB-2086-induced differentiation in breast cancer cells involved the upregulation of PTEN, a key tumour suppressor protein opposing tumorigenesis, and was apparently independent of p53, PAFR, peripheral benzodiazepine receptor and ERα status. Overall, WEB-2086 can be proposed as an effective antiproliferative and differentiative agent with interesting translational opportunities to treat breast cancers in support to conventional chemotherapy.

Inhibition of Phosphotyrosine Phosphatase 1B Causes Resistance in BCR-ABL-Positive Leukemia Cells to the ABL Kinase Inhibitor STI571

Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of BCR-ABL-mediated transformation in vitro and in vivo. To investigate whether PTP1B modulates the biological effects of the abl kinase inhibitor STI571 in BCR-ABL-positive cells, we transfected Philadelphia chromosome-positive (Ph+) chronic myeloid leukemia cell-derived K562 cells with either wild-type PTP1B (K562/PTP1B), a substrate-trapping dominant-negative mutant PTP1B (K562/D181A), or empty vector (K562/mock). Cells were cultured with or without STI571 and analyzed for its effects on proliferation, differentiation, and apoptosis. In both K562/mock and K562/PTP1B cells, 0.25 to 1 mumol/L STI571 induced dose-dependent growth arrest and apoptosis, as measured by a decrease of cell proliferation and an increase of Annexin V-positive cells and/or of cells in the sub-G(1) apoptotic phase. Western blot analysis showed increased protein levels of activated caspase-3 and caspase-8 and induction of poly(ADP-ribose) polymerase cleavage. Low concentrations of STI571 promoted erythroid differentiation of these cells. Conversely, K562/D181A cells displayed significantly lower PTP1B-specific tyrosine phosphatase activity and were significantly less sensitive to STI571-induced growth arrest, apoptosis, and erythroid differentiation. Pharmacologic inhibition of PTP1B activity in wild-type K562 cells, using bis(N,N-dimethylhydroxamido)hydroxooxovanadate, attenuated STI571-induced apoptosis. Lastly, comparison of the STI571-sensitive Ph+ acute lymphoblastic leukemia cell line SupB15 with a STI571-resistant subline revealed significantly decreased PTP1B activity and enhanced BCR-ABL phosphorylation in the STI571-resistant SupB15 cells. In conclusion, functional PTP1B is involved in STI571-induced growth and cell cycle arrest, apoptosis, and differentiation, and attenuation of PTP1B function may contribute to resistance towards STI571.

ZD1839 (Gefitinib, ‘Iressa’), an epidermal growth factor receptor-tyrosine kinase inhibitor, enhances the anti-cancer effects of TRAIL in human esophageal squamous cell carcinoma

The EGF (epidermal growth factor) receptor-tyrosine kinase inhibitor ZD1839 (Gefitinib, ‘Iressa’) blocks the cell signaling pathways involved in cell proliferation, survival, and angiogenesis in various cancer cells. TNF-related death apoptosis inducing ligand (TRAIL) acts as an anticancer agent. We investigated the antitumor effects of ZD1839 alone or in combination with TRAIL against human esophageal squamous cell cancer (ESCC) lines. Although all ESCC cells expressed EGF receptor at a protein level, the effect of ZD1839 on cell growth did not correlate with the level of EGFR expression and phosphorylation of EGF receptor protein in ESCC lines. ZD1839 caused a dose-dependent growth arrest at G 0–G 1 phase associated with increased p27 expression. As TE8 cells are resistant to TRAIL, we tested whether ZD1839 combined with TRAIL induced apoptosis of TE8 cells via the inhibition of EGF receptor signaling by ZD1839. ZD1839 inhibited the phosphorylation of Akt, and enhanced TRAIL-induced apoptosis via activation of caspase-3 and caspase-9, and inactivation of Bcl-xL. Our results indicated that ZD1839 has anti-cancer properties against human esophageal cancer cells. ZD1839 also augmented the anti-cancer activity of TRAIL, even in TRAIL-resistant tumors. These results suggest that treatment with ZD1839 and TRAIL may have potential in the treatment of ESCC patients.

Phenylbutyrate inhibits growth of cervical carcinoma cells independent of HPV type and copy number.

Inhibitors of histone deacetylase, such as sodium butyrate, block proliferation of cervical carcinoma cells by inhibiting the G1 to S transition of the cell cycle. The derivative phenylbutyrate (PB), characterized by its higher pharmacological half-life, and its metabolite phenylacetate (PA) were tested for their growth-inhibitory function on cervical cancer cells differing in their HPV type, copy number, and integration sites. Using flow cytometric and Western blot analyses, we show that a 24-h incubation period with PB, but not with PA, was already sufficient to cause a dose-dependent growth arrest by increasing the G1 fraction with a concomitant drop in the S-phase. Consistent with the cell cycle block, only PB, but not PA, induced the cyclin-dependent kinase inhibitors p21(CIP1) and p27(KIP1). The inhibitory effect was not the result of a non-specific cytotoxic effect of PB, since cessation of cellular growth was already completely reversible 5 h after drug removal. Due to its broad growth inhibitory properties on different cervical carcinoma cells in vitro, and its low toxic profile demonstrated in preceding clinical studies, PB may serve as an effective drug in handling pre-cancerous lesions and cervical cancer in patients.

Constitutive activation of STAT transcription factors in acute myelogenous leukemia

Hematopoietic growth factors (HGF) are essential for proliferation and differentiation of hematopoietic precursors and activate a distinct set of JAK-STAT (Janus kinases-signal transducers and activators of transcription) proteins. Previous results from our group have shown a strong expression of JAK-STAT proteins in primary acute myelogenous leukemia (AML) blasts and AML cell lines. Here, we asked whether a constitutive activation of the JAK-STAT pathway might be involved in the pathogenesis of AML. We could demonstrate a constitutive activation of STAT1, 3 and 5 by immunoprecipitation of the tyrosine phosphorylated proteins in different human AML cell lines. Three patterns of STAT activation were found: (I) activation of only STAT1, (II) activation of STAT1 in combination with STAT3, and (III) activation of STAT1, 3 and 5. Furthermore, STAT1 and 3 formed stable heterodimers only in cell lines with constitutive STAT3 activation. In all cell lines analyzed, tyrosine phosphorylation of the four known Janus kinases could not be detected, although JAK1 was stably associated with STAT3. To further analyze whether a constitutive activation of tyrosine kinases might contribute to the autonomous growth of AML blasts, inhibitor studies were performed. The tyrphostin AG490, an inhibitor of the JAK-STAT pathway, but not A1, an inactive tyrphostin induced a time- and dose-dependent growth arrest without overt morphological signs of differentiation in AML cell lines. Our results show that STAT transcription factors are constitutively activated in human AML cell lines and might contribute to the autonomous proliferation of AML blasts. Inhibition of this pathway might be of interest for the establishment of more specific antileukemic strategies.

Constitutive activation of STAT transcription factors in acute myelogenous leukemia

Abstract: Hematopoietic growth factors (HGF) are essential for proliferation and differentiation of hematopoietic precursors and activate a distinct set of JAK-STAT (Janus kinases-signal transducers and activators of transcription) proteins. Previous results from our group have shown a strong expression of JAK-STAT proteins in primary acute myelogenous leukemia (AML) blasts and AML cell lines. Here, we asked whether a constitutive activation of the JAK-STAT pathway might be involved in the pathogenesis of AML. We could demonstrate a constitutive activation of STAT1, 3 and 5 by immunoprecipitation of the tyrosine phosphorylated proteins in different human AML cell lines. Three patterns of STAT activation were found: (I) activation of only STAT1, (II) activation of STAT1 in combination with STAT3, and (III) activation of STAT1, 3 and 5. Furthermore, STAT1 and 3 formed stable heterodimers only in cell lines with constitutive STAT3 activation. In all cell lines analyzed, tyrosine phosphorylation of the four known Janus kinases could not be detected, although JAK1 was stably associated with STAT3. To further analyze whether a constitutive activation of tyrosine kinases might contribute to the autonomous growth of AML blasts, inhibitor studies were performed. The tyrphostin AG490, an inhibitor of the JAK-STAT pathway, but not A1, an inactive tyrphostin induced a time- and dose-dependent growth arrest without overt morphological signs of differentiation in AML cell lines. Our results show that STAT transcription factors are constitutively activated in human AML cell lines and might contribute to the autonomous proliferation of AML blasts. Inhibition of this pathway might be of interest for the establishment of more specific antileukemic strategies.

Mitogen-activated protein kinases control p27/Kip1 expression and growth of human melanoma cells.

The mitogen-activated protein kinases (MAPKs) extracellular signal-regulated protein kinase (ERK)1 and ERK2, involved in regulating cell growth and differentiation, are constitutively active in A375 and WM239 human melanoma cells. Using PD098059, an inhibitor of MAPK kinase (MEK), we investigated the role of persistently activated ERK1/2 in cell growth. The inhibition of MAPK activity induced a dose-dependent growth arrest in G(0)/G(1) phase. Correspondingly, we observed the up-regulation of the cyclin-dependent kinase (Cdk) inhibitor p27/Kip1 and hypophosphorylation of the retinoblastoma protein. Further studies showed that PD098059 treatment significantly decreased Cdk2 kinase activity, most probably owing to an augmented level of p27/Kip1 associated with cyclin E-Cdk2 complexes. The accumulation of p27/Kip1 protein in A375 cells was attributed to its increased stability. Our findings suggest that constitutively active ERK1/2 kinases contribute to the growth of melanoma cells by negative regulation of the p27/Kip1 inhibitor.

Mitogen-activated protein kinases control p27/Kip1 expression and growth of human melanoma cells

The mitogen-activated protein kinases (MAPKs) extracellular signal-regulated protein kinase (ERK)1 and ERK2, involved in regulating cell growth and differentiation, are constitutively active in A375 and WM239 human melanoma cells. Using PD098059, an inhibitor of MAPK kinase (MEK), we investigated the role of persistently activated ERK1/2 in cell growth. The inhibition of MAPK activity induced a dose-dependent growth arrest in G0/G1 phase. Correspondingly, we observed the up-regulation of the cyclin-dependent kinase (Cdk) inhibitor p27/Kip1 and hypophosphorylation of the retinoblastoma protein. Further studies showed that PD098059 treatment significantly decreased Cdk2 kinase activity, most probably owing to an augmented level of p27/Kip1 associated with cyclin E–Cdk2 complexes. The accumulation of p27/Kip1 protein in A375 cells was attributed to its increased stability. Our findings suggest that constitutively active ERK1/2 kinases contribute to the growth of melanoma cells by negative regulation of the p27/Kip1 inhibitor.