The effect of antimicrotubule agents on signal transduction pathways of apoptosis: a review

PURPOSE

Microtubules are important cytoskeletal components involved in many cellular events. Antimicrotubule agents including polymerizing agents (paclitaxel and docetaxel) and depolymerizing drugs (vincristine, vinorelbine, and estramustine phosphate) are widely used either alone or in combination with other anticancer drugs. These antimicrotubule agents are promoters of apoptosis in cancer cells. In this review, we discuss the role of bcl-2 family genes in the regulation of apoptosis, and summarize effects of microtubule targeting agents on apoptotic signal transduction pathways.

CONCLUSION

Disruption of microtubule structure by antimicrotubule drugs results in induction of tumor suppressor gene p53 and inhibitor of cyclin-dependent kinases, p21WAF1/CIP1 (p21), and activation/inactivation of several protein kinases including Ras/Raf, PKC/PKA I/II, MAP kinases, and p34cdc2. These protein kinases are associated directly or indirectly with phosphorylation of bcl-2. Phosphorylation of bcl-2 and the elevations of p53 and p21 lead to apoptosis. New pathways of antitumor agents could be directed at this p53, p21 and bcl-2/bax function, and may enhance the effect of existing agents.

Anti-tumor effect of angiogenesis inhibitor TNP-470 on the human nasopharyngeal carcinoma cell line NPC/HK1

The efficacy and targeting cells of angiogenesis inhibitor TNP-470 on human squamous cell nasopharyngeal carcinoma (NPC) were investigated. The colorimetric MTT assay was used to evaluate the IC50 values of NPC/HK1 cells and human dermal microvascular endothelial cells (HDMEC) for TNP-470. An NPC human tumor model was built by tumor-bearing nude mice using the NPC cell line of NPC/HK1. TNP-470 (30 mg/kg s.c.) was injected every other day. The results showed that the IC50 of NPC/HK1 cells for TNP-470 was 3.8 times higher than that of HDMEC. A significant difference in tumor volume between control and treatment groups was found after 7 days of treatment and increased thereafter. At the end of the treatment, tumor volume was 773.7 +/- 287.1 mm3 (n = 8) in the control group versus 454.5 +/- 132.8 mm3 (n = 8) in the treatment group (p = 0. 013); the ratio of the mean tumor volume in treated animals to that of control animals was 0.587, resulting a 41.3% decrease in tumor growth. The necrotic area was larger in the treatment group. Physical toxicity did not result from the treatment. These studies suggest that angiogenesis inhibitor TNP-470 is effective in the treatment of squamous cell NPC without obvious toxicity.

Phosphorylation/dephosphorylation of androgen receptor as a determinant of androgen agonistic or antagonistic activity

Protein phosphorylation/dephosphorylation is an important posttranslational modification that plays a critical role in signal transduction. The androgen receptor (AR) is under such control. We demonstrate that androgen receptor phosphorylation determines whether or not AR ligands perform as agonists or antagonists in LNCaP cells. Androgen receptor ligands (such as dihydrotestosterone and beta-estradiol) stimulate receptor expression and phosphorylation and, as a result, they act as agonists or partial agonists. In contrast, agents such as bicalutamide and estramustine inhibit the receptor phosphorylation and act as antagonists. This model is supported by gene expression and transactivation assays. Significant increases in levels of both mRNA and protein of prostate-specific antigen (PSA), a natural AR target gene, occur following the treatment of LNCaP cells with DHT, beta-estradiol, or hydroxyflutamide. In contrast, exposure of LNCaP cells to bicalutamide or estramustine results in a sharp decrease of PSA expression. Agonistic or antagonistic effect of these compounds on PSA expression parallels the level of phosphorylated, but not dephosphorylated androgen receptors. These agonistic or antagonistic effects are also observed in HeLa cells transfected with wild-type AR expression plasmid (pAR0) and AR-driven luciferase expression plasmid GRE-tk-LUC in the presence of different groups of AR blockers. Our data indicate that the functional status of androgen receptors is strongly correlated with the phosphorylation status of the receptors, and that the phosphorylated androgen receptor is the form of the receptor transcriptionally active in regulation. Thus the androgen receptor phosphorylation/dephosphorylation may serve as a new molecular target for screening androgen antagonists for the treatment of prostate cancer.

Androgen antagonistic effect of estramustine phosphate (EMP) metabolites on wild-type and mutated androgen receptor

Estramustine phosphate is used frequently, alone or in combination with other antitumor agents, for the treatment of hormone-refractory prostate cancer. Estramustine phosphate is metabolically activated in vivo, and its metabolites, estramustine, estromustine, estrone, and beta-estradiol inhibit the assembly of microtubules [for review see: Kreis W, In: Concepts, Mechanisms, and New Targets for Chemotherapy (Ed. Muggia FM), pp. 163-184. Kluwer Academic Publishers, Boston, 1995]. We investigated, by displacement of [3H]methyltrienolone in the presence of 2.5 mM of triamcinolone acetonide, the binding of estramustine phosphate and its metabolites, estramustine, estromustine, estrone, and beta-estradiol, as well as other antiandrogen agents including alpha-estradiol, bicalutamide, and hydroxyflutamide, to the mutated androgen receptor (m-AR) in LNCaP cells and to the wild-type androgen receptor in wild-type AR cDNA expression plasmid (w-pAR0) cDNA-transfected HeLa cells. Analogous to the antiandrogens, bicalutamide and hydroxyflutamide, binding of estramustine phosphate metabolites to the androgen receptor was observed. The EC50 values (in microM) were: estramustine phosphate, > 10; estramustine, 3.129 +/- 0.312; estromustine; 2.612 +/- 0.584; estrone, 0.800 +/- 0.090; alpha-estradiol, 1.051 +/- 0.096; beta-estradiol, 0.523 +/- 0.028; bicalutamide, 4.920 +/- 0.361; and hydroxyflutamide, 0.254 +/- 0.012. The transactivation assay demonstrated that, analogous to bicalutamide, estramustine could not induce luciferase activity in either w-pAR0 or m-pARL transfected HeLa cells. In contrast, a strong induction of the reporter activity by dihydrotestosterone was observed. Down-regulation of prostate-specific antigen (PSA) expression, an AR-target gene, by estramustine and bicalutamide was accompanied by the blockade of the mutated androgen receptor. Exposure of LNCaP cells to estramustine for 24 hr caused transcriptional inhibition of PSA in a concentration-dependent manner. The levels of PSA mRNA decreased 56 and 90% when LNCaP cells were treated with 5 and 10 microM of estramustine, respectively (IC50 = 10.97 +/- 1.68 microM). Binding of hydroxyflutamide to m-AR in LNCaP cells resulted in a concentration-dependent stimulation of PSA expression, suggesting that hydroxyflutamide acted as an agonist of the m-AR. Our data indicate that estramustine phosphate metabolites perform as androgen antagonists of AR, an additional mechanism involved in the therapeutic effect of estramustine phosphate in patients with prostate cancer.

Down-regulation of prostate-specific antigen expression by finasteride through inhibition of complex formation between androgen receptor and steroid receptor-binding consensus in the promoter of the PSA gene in LNCaP cells

As a specific competitive inhibitor of 5alpha-reductase, an intracellular enzyme that converts testosterone to dihydrotestosterone, finasteride is being extensively used for the treatment of benign prostatic hyperplasia and in experimental settings for prostate cancer. In this study, we showed that finasteride markedly inhibited prostate-specific antigen (PSA) secretion and expression. The promoter of the PSA gene contains several well-known cis-regulatory elements. Among them, steroid receptor-binding consensus (SRBC) has been identified as a functional androgen-responsive element. Our previous study showed that PSA was not only present in conditioned medium of the PSA-positive LNCaP cells but was also detectable in small amounts in PSA-negative cell lines, PC-3 and DU-145 (L. G. Wang et al., Oncol. Rep., 3: 911-917, 1996). A strong correlation between binding of nuclear factors to SRBC and the level of PSA present in the conditioned medium and cell extracts was found in these three cell lines, whereas no such correlation with binding was obtained using Sp1 oligonucleotide as a probe. Binding of LNCaP cell nuclear proteins to SRBC was diminished when the cells were exposed to 25 microM finasteride, at which concentration 50% of both PSA mRNA and protein were inhibited. As a major component of DNA-protein complexes, the level of androgen receptor was dramatically decreased in the cells treated with finasteride. Our data indicate that inhibition of complex formation between SRBC and nuclear proteins due to the remarkable decrease in the level of androgen receptor plays a key role in the down-regulation of PSA gene expression by finasteride in LNCaP cells.

Induction of differentiation and down-regulation of c-myb gene expression in ML-1 human myeloblastic leukemia cells by the clinically effective anti-leukemia agent meisoindigo

Meisoindigo, a second generation derivative of indirubin, is an effective chemotherapeutic agent with very low toxicity used in the treatment of chronic myeloid leukemia. To determine the nature of this activity, the effect of a nontoxic concentration (0.72 micrograms/mL) of this compound on ML-1 human myeloblastic leukemic cells was examined. At such a concentration, differentiation induction was found to be the most pronounced drug effect. During the 3-day drug incubation period, the viable cell number remained essentially constant, with approximately 48% of the cells demonstrating a mature phenotype with increased acid phosphatase activity and nitroblue tetrazolium dye reduction. As observed with other DNA-specific agents, induction of ML-1 differentiation by meisoindigo was accompanied by the down-regulation of c-myb gene expression. These data suggest that induction of leukemic cell differentiation associated with decreased c-myb expression may be one of the mechanisms of the antitumor action of meisoindigo.

Evidence that lipid peroxidation products bind to DNA in liver cells

Three lines of evidence are presented indicating the association of lipid peroxidation products with DNA in liver cells, labeled with [3H]arachidonic acid, in the presence of Fe(2+)-DTPA: (1) the nuclear DNA isolated from treated cells had higher radioactivity, compared to controls and the radioactivity increased with longer incubation times, (2) lipid-DNA adducts with a characteristic fluorescence spectrum were formed during the incubation with Fe(2+)-DTPA; (3) the association of peroxidation products with DNA could be inhibited by vitamin E and BHT. Compared with control DNA, purified lipid-DNA adducts showed a decrease of hyperchromicity and melting point, and partial resistance to hydrolysis by DNase I. On the other hand, the repair test shows that the lipid-DNA adducts in cells were not repaired by 4 h after removal of Fe(2+)-DTPA. A decrease in cell viability and in the activity of O6-alkylguanine acceptor protein was also observed with increasing incubation time. These data suggest that the lipid-DNA association, an oxidative DNA damage, occurs in cells treated by Fe(2+)-DTPA and could result in cytotoxicity if not repaired.

Activation of casein kinase II in ML-1 human myeloblastic leukemia cells requires IGF-1 and transferrin

Casein kinase II (CK II), a key enzyme involved in the regulation of cell growth, has been variously reported to be activated by diverse mitogens, including insulin-like growth factor 1 (IGF-1) and epidermal growth factor (EGF). Activation of the enzyme is generally carried out in the presence of serum, and we examined the question whether serum components participate in the activation process. We demonstrated previously that ML-1 cells require IGF-1 plus transferrin (TF) for growth and transforming growth factor beta or tumor necrosis factor alpha plus TF for differentiation. We now found that CK II is activated only when the cells are exposed to both IGF-1 and TF or when TF is replaced in this combination with relatively high levels of iron salts. Induction of differentiation with TGF-beta and TF did not result in CK II activation. These results show that CK II activation in ML-1 cells requires the application of both components of the growth signal, IGF-1 and TF, demonstrating that the growth factor alone is incapable of enhancing the activity of the enzyme.

Regulation of c-myb expression in ML-1 human myeloblastic leukemia cells by c-ets-1 protein

C-myb and c-ets-1 have variously been demonstrated to function as protooncogenes. Using a human leukemic cell line, ML-1, we have examined the mechanism by which these genes participate in establishing the sustained proliferation mode that is characteristic of the transformed cell. In the absence of serum, ML-1 cells were found to require IGF-1 and transferrin (TF) for growth and TGF-beta or TNF-alpha plus TF for differentiation. Upon administration of the growth factors, c-myb expression increased within 60 min, whereas after addition of the differentiation factors c-myb expression ceased completely within 3 hr. A correlation was found to exist between the level of c-ets-1 protein in the cells, the extent to which that protein is bound to intron I of the myb gene and the amount of c-myb mRNA that is expressed. Upon administration of growth factors, a sizable increase in the intracellular, and particularly, in the intranuclear level of c-ets-1 protein was observed, whereas a pronounced decrease in the level of this protein occurred after exposure to the differentiation factors. These data demonstrated that the level at which an oncogene-specified transcription factor is expressed can affect the expression of other target oncogenes involved in the regulation of cell proliferation. Stimulated expression of such transcription factor can then lead to the continuous proliferation cycle characteristic of the cancer cell.

Differential binding of nuclear c-ets-1 protein to an intron I fragment of the c-myb gene in growth versus differentiation

For growth, ML-1 human myeloblastic leukemia cells require insulin-like growth factor 1 together with transferrin, whereas for differentiation they depend upon transforming growth factor beta in combination with transferrin. As shown in this study, growth stimulation is accompanied by c-myb expression, whereas initiation of differentiation results in the cessation of c-myb expression through premature termination of transcription in the first intron of the myb gene. Growth factor-stimulated c-myb elongation was found to correlate with an elevated level of nuclear c-ets-1 protein and with increased binding of this protein to an 18-base pair sequence in intron 1 of the c-myb gene containing the putative regulatory element PEA 3. In contrast, differentiation factor-initiated ML-1 cell maturation was accompanied by a very low level of nuclear c-ets-1 protein, by the inability to detect binding of the protein to the 18-base pair sequence, and by the cessation of c-myb expression. These results show a correlation to exist between c-ets-1 binding to intron 1 of the c-myb gene and c-myb expression. The mechanism underlying this correlation is under further study.

Formalin induced FOS-like immunoreactive neurons in the trigeminal spinal caudal subnucleus project to contralateral parabrachial nucleus in the rat

By combining the retrograde-labeling method of injecting Fluoro-Gold (FG) into the parabrachial nucleus (PB) and the immunocytochemical staining of the FOS-like immunoreactive neurons (FLNs) in the trigeminal spinal caudal subnucleus (TSCS) induced by s.c. formalin injection into the perioral region in the rat, it was demonstrated that there are FLNs, FG-labeled neurons and neurons containing both FOS-like immunoreactivity and FG fluorescence in the TSCS. The three kinds of labeled neurons are distributed mainly in laminae I, II and V of the TSCS and there are also some neurons containing both FOS-like immunoreactivity and FG distributed in the adjacent ventrolateral reticular formation. The retrograde-labeling of FG- and double-labeled neurons showed contralateral predominance. In addition, we found that there are retrogradely labeled neurons in bilateral nuclei of the solitary tract with a contralateral predominance. The results suggest that FOS-like immunoreactivity might serve as an indicator for the nociceptive response after formalin injection into the trigeminal region and that the PB might be an important relay station for the further processing of the nociceptive information relayed from the trigeminal afferents. As the PB is known as a relay structure for visceral sensory pathway, it is proposed that there might be viscero-somatic convergence in this nucleus.

Prenatal ontogeny of substance P-like immunoreactivity in the nucleus tractus solitarii and dorsal motor nucleus of the vagus nerve of the human fetus: an immunocytochemical study

By using immunocytochemical method, the prenatal ontogeny of substance P-like immunoreactivity (SP-LI) was demonstrated in the dorsal motor nucleus of the vagus nerve (nX) and the nucleus tractus solitarii (nTS) of the human fetus at fetal age (menstruation age) of 11.5 weeks to 40 weeks. The time of initial appearance of SP-LI in the human brainstem nTS was between the fetal age 11.5 weeks and 16 weeks. At fetal age 16 weeks, the nTS showed moderate density of SP-LI fibers and terminals in subnucleus dorsalis of the nTS and nX. While the fetus grew, the density of SP-LI in the human fetus brainstem nTS and nX increased gradually from fetal age 16 weeks to 40 weeks. According to the Nissl staining, at fetal age 23 weeks, the nTS of human fetus can be subdivided into dorsal, medial, dorsolateral, ventrolateral, ventral and gelatinosus subnuclei. The cytoarchitectonic subdivisions of human fetus nTS is in good agreement with the results obtained by immunocytochemical staining. These findings indicated that substance P (SP) might play an important role in the development of human brainstem nX, nTS, their related cranial nerves, and in their functional establishment during the prenatal period.

Prenatal ontogeny of substance P-like immunoreactivity in the parabrachial nucleus of the human fetus--an immunocytochemical study

Using an immunocytochemical method, the prenatal ontogeny of substance P-like immunoreactivity (SP-LI) was demonstrated in the parabrachial nucleus (PB) of human fetus, fetal age (menstruation age) 11.5 to 40 weeks. The time of initial appearance of SP-LI in the human brainstem PB was between fetal age 11.5 weeks and 16 weeks. While the fetus grew, the density of SP-LI fibers and terminals in the human fetus brainstem PB increased constantly from fetal age 16 weeks to 40 weeks. These findings indicate that substance P (SP) might play an important role in the human parabrachial nucleus development and in its functional establishment during the prenatal period.

Prenatal ontogeny of substance P-like immunoreactivity in the trigeminal spinal caudal subnucleus of the human fetus--an immunocytochemical study

Using an immunocytochemical method, the prenatal ontogeny of substance P-like immunoreactivity (SP-LI) was demonstrated in the trigeminal spinal caudal subnucleus (TSCS) of human fetus, fetal age (menstruation age) 11.5-40 weeks. The time of initial appearance of SP-LI in the human brainstem TSCS was between the fetal age 11.5 weeks and 16 weeks. While the fetus grew, the density of SPLI fibers and terminals in the human fetus brainstem TSCS increased constantly from fetal age 16 weeks to 40 weeks. These findings indicated that substance P (SP) might play an important role in the human trigeminal nerve system development and in its functional establishment during the prenatal period.

Determination of DNA topoisomerase II activity from L1210 cells--a target for screening antitumor agents

DNA topoisomerase II was isolated from mouse leukemia L1210 cells and the activity was determined by using P4 phage knotted DNA and pBR 322 DNA as the substrates. Based on these results, a method for screening antitumor agents by using DNA topoisomerase II as a target was established. The experiments showed that DNA topoisomerase II catalyzed pBR 322 DNA breaking and relaxing which were reversible and dependent on ATP. The activity was increased 2-4 times in the presence of ATP 1 mmol.L-1. In contrast with type II enzyme, the activity of DNA topoisomerase I was completely inhibited in the presence of ATP 1 mmol.L-1 and had full activity in the absence of ATP. Type II enzyme also showed the unknotting activity by using p4 phage knotted DNA as a substrate. DNA cleavage and relaxing reaction induced by type II enzyme increased 5-fold in the presence of Doxorubicin (Dox) 1 microgram.ml-1 or daunorubicin (Dau). Etoposide (Eto) and aclarubicin B (Acl B) also stimulated the reaction at 100 micrograms.ml-1. The cleavage reaction resulted from topoisomerase II was inhibited by other agents, such as frankincense extracts, terpenic compounds (BC series).

Optical fringe reduction technique for FM laser spectroscopy

A simple and effective fringe reduction technique for FM 200 250 laser spectroscopy is discussed. A factor of 20 fringe reduction was observed in two-tone FM spectroscopy of water vapor. Theoretical simulations are compared to the exere perimental results.

Inactivation of O6-alkylguanine-DNA alkyltransferase in HeLa cells by cisplatin

Inactivation of O6-alkylguanine-DNA alkyltransferase (O6-AGT) in HeLa CCL2 cells by cisplatin was studied. HeLa CCL2 cells treated with cisplatin showed a dose-dependent decline in O6-AGT activity. After cisplatin was removed and replaced with fresh medium, the transferase level began to rise slowly. By 72 h slightly more than 80% of the activity was recovered. It seems that the activity of the alkyltransferase can be inactivated by platinated DNA adducts. The data suggest that the O6-platinum-guanine formation and the O6-alkyltransferase depletion are not responsible for cytotoxicity but may result in a base substitution mutation in mammalian cells.

O6-methylguanine-DNA methyltransferase in lymphocytes of the elderly with and without Alzheimer's disease

Deficiency in DNA repair has been linked to aging, mutagenesis, carcinogenesis and several types of primary neuronal degeneration. O6-Methylguanine-DNA methyltransferase is a key enzyme in the repair of DNA alkylation damage that removes a methyl group from the O6 position of methylguanine. This study was carried out to determine whether there were any changes in the activity of this enzyme in lymphocytes of patients with Alzheimer's disease (AD) as compared to lymphocytes of age-matched non-demented elderly. The transferase activity in lymphocytes from 19 elderly patients with AD (mean 87.7 fmole/100 micrograms protein +/- SD 44.7) was not statistically different from that in 19 age/sex-matched controls (mean 91.3 fmole/100 micrograms protein +/- SD 40.0). There was no significant trend with age in transferase activity and the activity levels in the elderly subjects studied were the same as those reported previously for younger individuals by this laboratory. It is concluded that a reduction in O6-methylguanine-DNA methyltransferase activity is unlikely to be involved in the etiology or the pathogenesis of AD.

DNA-protein, DNA interstrand cross-links induced by camphoramine chloroacetic platinum in vitro

Effects of camphoramine chloroacetic platinum (CCP) on DNA migration and transcription, DNA-protein and DNA interstrand cross-links induced by CCP were investigated by using agarose gel electrophoresis, alkaline elution and enzymatic techniques, respectively. Chromosome break down and migration alteration of DNa modified by CCP were observed. Plasmid pAR 436 DNA transcription was also blocked when the DNA was treated with CCP. The cross-links took place 8 h after HeLa cells were exposed to CCP 10 mumol/L and higher number of cross-links were obtained after treatment with the agent 20 mumol/L. The number of cross-links was also found to be decreased when the cell lysis was digested with proteinase K. These results suggest that CCP can also induce DNA-protein cross links. Enzymatic studies indicated that CCP preferentially attacks guanine in DNA and restriction enzymes are unable to cleave G-platinated at interval of one base to the restriction sequence.

Comparison of approaches to modulation spectroscopy with GaAIAs semiconductor lasers: application to water vapor

Four different forms of modulation spectroscopy were used to study water vapor absorption around 816 nm using GaAIAs semiconductor lasers. They are wavelength modulation at 1 kHz and 100 MHz, single-tone frequency modulation (FM) at 1 GHz, and two-tone FM at I GHz +/- 10 MHz. Extrapolating from measurements on a 1.4% absorption we find that two-tone frequency modulation is sensitive to an absorption of 2.4 x 10(-6). This is at least an order of magnitude more sensitive than single-tone FM and wavelength modulation.

Application of hydroelastic waves of the Chinese traditional medicine solution to the traumatotherapy

We have used hydroelastic waves to treat the closed trauma of the soft tissue. The Shu Huo Jiu (S. H. J.) which is the Chinese traditional medicine alcohol, was used as the fluid medium for generating the pressure waves. The biomechanical model was established and analysed. Both animal and human tests have been made. A practical system was designed, constructed and clinically tested to treat the closed trauma, such as the bruise, contusion, sprain etc.. This system was found to be effective.