Growth Potential Of Cancer Cells Research Articles

Inhibition of cancer progression by a novel trans-stilbene derivative through disruption of microtubule dynamics, driving G2/M arrest, and p53-dependent apoptosis

Resveratrol, a trans-stilbene polyphenolic compound and its synthetic analogs are widely used bioactive molecules due to their remarkable chemo-preventive potential. Here, we have identified a novel synthetic trans-stilbene compound, Z-DAN-11 ((Z)-3-(3, 4-dimethoxyphenyl)-2-(3, 4, 5-trimethoxyphenyl) acrylonitrile) which shows remarkable efficacy in blocking tumor growth and progression both in vitro and in vivo. Z-DAN-11 inhibits proliferation of cancer cells in vitro through microtubule depolymerization that induced G2/M arrest and consequently leads to apoptotic cell death. More importantly, Z-DAN-11 shows limited cytotoxicity to normal cells as compared to cancer cells. Quite interestingly, we have found that Z-DAN-11-mediated ROS production helps in dramatic alteration in the mitochondrial redox status which critically contributes to the apoptosis. Mechanistic studies reveal that Z-DAN-11 induces the expression of pro-apoptotic proteins and decreases anti-apoptotic protein expression that decisively helps in the activation of caspase 8, caspase 9, and caspase 3, leading to cleavage of PARP1 and cell death via intrinsic and extrinsic pathways of apoptosis. Moreover, Z-DAN-11-mediated apoptosis of cancer cells is through a partial p53-dependent pathway, since both HCT116 p53−/− cells as well as p53-silenced cells (siRNA) were able to block apoptosis partially but significantly. Importantly, Z-DAN-11 also imparts its anti-tumorigenic effect by inhibiting clonogenic property and anchorage-independent growth potential of cancer cells at concentrations at least 10 times lower than that required for inducing apoptosis. Finally, in vivo study with immuno-competent syngeneic mice shows Z-DAN-11 to be able to impede tumor progression without any adverse side-effects. Hence, we identified a novel, synthetic trans-stilbene derivative with anti-tumorigenic potential which might tremendously help in devising potential therapeutic strategy against cancer.

Abstract IA8: Novel insights into synthetic lethal interactions in cancer: Common nodes in protein synthesis control and nucleotide metabolism

Abstract Our research is centered on understanding the molecular mechanisms by which impairments in accurate control of mRNA translation, cell growth, and overall cellular protein synthesis rates lead to cancer and human disease. We have uncovered that a common denominator of multiple oncogenic pathways (i.e. PI3K-AKT-mTOR, Ras, Myc) is their ability to directly control the core translation machinery of a cell, resulting in intrinsic regulation of the cancer cell gene expression program. Our work delineates how the “cancer translatome” can reprogram gene expression at the post-transcription level, by controlling the translation of specific subsets of mRNAs through unique cis-acting elements, during distinct steps of cancer progression. The immediate impact of these studies has been the design of a new generation of compounds to target the aberrant translation machinery, presently in clinical trials. I will discuss our most recent findings revealing that oncogenic pathways have evolved self-sustaining circuitries that couple two fundamental cellular processes, protein synthesis and metabolism, to sustain the unchecked growth potential of cancer cells. By employing an unbiased metabolomics approach combined with mouse genetics, our findings unveil a critical feed-forward mechanism by which Myc's ability to elevate the protein synthesis capacity of cancer cells directly reprograms nucleotide biosynthesis pathways as a mechanism to sustain tumor growth and survival. I will further discuss how both PI3K-AKT-mTOR and Myc converge on phosphorylation of 4EBP1, a master regulator of protein synthesis control, setting the stage for a unique therapeutic approach to render Myc druggable in the clinic. Together, our findings reveal that targeting either hyperactivation of protein synthesis or nucleotide production represents a novel and unexpected synthetic lethal mechanism for eradicating cancer but not normal cells. Citation Format: Davide Ruggero. Novel insights into synthetic lethal interactions in cancer: Common nodes in protein synthesis control and nucleotide metabolism. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr IA8.

2D-QSAR of purine-scaffold novel class of Hsp90 binders that inhibit the proliferation of cancer cells

The chaperone heat shock protein 90 (Hsp90) is an emerging target for designing anticancer agent due to its important roles in maintaining transformation and modulating the survival and growth potential of cancer cells. Quantitative structure–activity relationship (QSAR) studies have been carried out in a series of purine derivatives with Hsp90 inhibitory activities. The two-diemensional (2D) QSAR studies revealed that the activity is positively influenced by the presence of a halo substituent in the trimethoxyphenyl moiety and by electronic parameter (field effect) of the 9-N substituent where the contribution of the steric parameter (MR) is negative. The best QSAR model with good correlation coefficient (r 2 = 0.738), of high statistical significance (>99.9%) well explained the variance in activity.

Potent siRNA Inhibitors of Ribonucleotide Reductase Subunit RRM2 Reduce Cell Proliferation In vitro and In vivo

Ribonucleotide reductase (RR) is a therapeutic target for DNA replication-dependent diseases such as cancer. Here, a potent small interfering RNA (siRNA) duplex against the M2 subunit of RR (RRM2) is developed and shown to reduce the growth potential of cancer cells both in vitro and in vivo. Three anti-RRM2 siRNAs were identified via computational methods, and the potency of these and additional "tiling" duplexes was analyzed in cultured cells via cotransfections using a RRM2-luciferase fusion construct. Knockdown of RRM2 by the best duplex candidates was confirmed directly by Western blotting. The effect of potent duplexes on cell growth was investigated by a real-time cell electronic sensing assay. Finally, duplex performance was tested in vivo in luciferase-expressing cells via whole animal bioluminescence imaging. Moderate anti-RRM2 effects are observed from the three duplexes identified by computational methods. However, the tiling experiments yielded an extremely potent duplex (siR2B+5). This duplex achieves significant knockdown of RRM2 protein in cultured cells and has pronounced antiproliferative activity. S.c. tumors of cells that had been transfected with siR2B+5 preinjection grew slower than those of control cells. An anti-RRM2 siRNA duplex is identified that exhibits significant antiproliferative activity in cancer cells of varying human type and species (mouse, rat, monkey); these findings suggest that this duplex is a promising candidate for therapeutic development.

Emerging Hsp90 Inhibitors: From Discovery to Clinic

Hsp90 is a chaperone with important roles in maintaining transformation and in elevating the survival and growth potential of cancer cells. Activation of signaling pathways mediated by Hsp90 protein clients is necessary for cell proliferation, regulation of cell cycle progression and apoptosis. Additionally, gain-of-function mutations responsible for transformation often require Hsp90 for the maintenance of their folded, functionally active conformations. These characteristics promise Hsp90 as an important target in cancer therapy and prompt for the identification, development and clinical translation of small molecule inhibitors of the chaperone. This review intends to update the reader on the status of several existing and emerging classes of direct inhibitors of Hsp90 ATPase activity.

Evaluation of 8-Arylsulfanyl, 8-Arylsulfoxyl, and 8-Arylsulfonyl Adenine Derivatives as Inhibitors of the Heat Shock Protein 90

Hsp90 is a chaperone protein with important roles in maintaining transformation and in elevating the survival and growth potential of cancer cells. Currently there is an increasing interest in developing inhibitors of this protein as anticancer therapeutics. One of such inhibitors, the purine-scaffold class, has been reported to be potent and selective against Hsp90 both in vitro and in vivo models of cancer. Here, a series of 8-arylsulfanyl, -sulfoxyl, and -sulfonyl adenine members of the purine class was synthesized and evaluated as inhibitors of the chaperone. The structure-activity relationship and selectivity for tumor Hsp90 of compounds within the series is presented. Our results suggest that 8-arylsulfanyl adenine derivatives are good inhibitors of chaperone activity, whereas oxidation of the sulfides to sulfoxides or sulfones leads to compounds of decreased activity. The study identifies derivative 11v as the most potent Hsp90 inhibitor of the purine-scaffold series published to date (EC(50) = 30 nM), and also as the compound of this class with highest selectivity for tumor vs normal cell Hsp90 (700 to 3000-fold). Most rewardingly, this work has allowed for the identification of Hsp90 inhibitors with selective affinities for Hsp90-client protein complexes, derivatives that may represent useful pharmacological tools in dissecting Hsp90-regulated processes.

Caspase-3 inhibits the growth of breast cancer cells independent of protease activity.

In this study, the MCF-7 breast cancer cells that lack caspase-3 were transfected with a wild type (WT) or mutant caspase-3 cDNA. Expression of the WT, but not of the mutant, caspase-3 was associated with increased caspase activity and susceptibility to staurosporine (STS)-induced apoptosis. Both derivatives displayed inhibition of cell growth compared with vector control cells. Growth inhibition was associated with increased expression of the cyclin dependent kinase (CDK) inhibitor p27Kip1 in the WT, but not in the mutant caspase-3 expressing cells. Cyclin D1 expression level was not affected by caspase-3 expression. Phosphorylation of the Akt protein was decreased in both WT and mutant caspase transfected cells, although Akt expression level remained unchanged. These results suggest that caspase-3 might have biological functions independent of its protease activity and that its loss might contribute to tumor development by increasing the growth potential of cancer cells.

Growth reduction in glioma cells after treatment with tetradecylthioacetic acid: changes in fatty acid metabolism and oxidative status

During aerobic metabolism, a small amount of partially reduced oxygen is produced, yielding reactive oxygen species (ROS). Peroxisomes and mitochondria are major contributors to cellular ROS production, which is normally balanced by consumption by antioxidants. The fatty acid analogue tetradecylthioacetic acid (TTA) promotes mitochondrial and peroxisomal proliferation, and may induce oxidative stress and change the growth potential of cancer cells. In the present study, we found that TTA reduced [ 3H]thymidine incorporation in the glioma cell lines BT4Cn (rat), D54Mg (human), and GaMg (human) in a dose- and time-dependent manner. The 50% inhibitory TTA doses were approximately 125 μM for BT4Cn and D54Mg cells and 40 μM for GaMg cells after 4 days. α-Tochopherol counteracted this inhibition in GaMg cells. TTA enhanced the oxidation of [1- 14C]palmitic acid, which could be explained by stimulation of enzymes involved in peroxisomal (fatty acyl-CoA oxidase) and/or mitochondrial (carnitine palmitoyltransferase) fatty acid oxidation. The glutathione content and the activities of glutathione peroxidase, glutathione reductase, and glutathione S-transferase were differentially affected. Increased malondialdehyde (MDA) production was seen in TTA-treated GaMg and D54Mg cells, but not in BT4Cn cells, in vitro. In BT4Cn tumor tissue from TTA-treated rats, MDA was increased while the α-tocopherol content tended to decrease. TTA increased the level of cytosolic cytochrome c in BT4Cn cells, which suggests induction of apoptotic cascades. Although several mechanisms are likely to be involved in the TTA-mediated effects on growth, we propose that modulation of cellular redox conditions caused by changes in fatty acid metabolism may be of vital importance.