Designing a broad-spectrum integrative approach for cancer prevention and treatment

Targeted therapies and the consequent adoption of "personalized" oncology have achieved notable successes in some cancers; however, significant problems remain with this approach. Many targeted therapies are highly toxic, costs are extremely high, and most patients experience relapse after a few disease-free months. Relapses arise from genetic heterogeneity in tumors, which harbor therapy-resistant immortalized cells that have adopted alternate and compensatory pathways (i.e., pathways that are not reliant upon the same mechanisms as those which have been targeted). To address these limitations, an international task force of 180 scientists was assembled to explore the concept of a low-toxicity "broad-spectrum" therapeutic approach that could simultaneously target many key pathways and mechanisms. Using cancer hallmark phenotypes and the tumor microenvironment to account for the various aspects of relevant cancer biology, interdisciplinary teams reviewed each hallmark area and nominated a wide range of high-priority targets (74 in total) that could be modified to improve patient outcomes. For these targets, corresponding low-toxicity therapeutic approaches were then suggested, many of which were phytochemicals. Proposed actions on each target and all of the approaches were further reviewed for known effects on other hallmark areas and the tumor microenvironment. Potential contrary or procarcinogenic effects were found for 3.9% of the relationships between targets and hallmarks, and mixed evidence of complementary and contrary relationships was found for 7.1%. Approximately 67% of the relationships revealed potentially complementary effects, and the remainder had no known relationship. Among the approaches, 1.1% had contrary, 2.8% had mixed and 62.1% had complementary relationships. These results suggest that a broad-spectrum approach should be feasible from a safety standpoint. This novel approach has potential to be relatively inexpensive, it should help us address stages and types of cancer that lack conventional treatment, and it may reduce relapse risks. A proposed agenda for future research is offered.

Arsenic Attenuates GLI Signaling, Increasing or Decreasing its Transcriptional Program in a Context-Dependent Manner

The metalloid arsenic is a worldwide environmental toxicant, exposure to which is associated with many adverse outcomes. Arsenic is also an effective therapeutic agent in certain disease settings. Arsenic was recently shown to regulate the activity of the Hedgehog (HH) signal transduction pathway, and this regulation of HH signaling was proposed to be responsible for a subset of arsenic's biologic effects. Surprisingly, these separate reports proposed contradictory activities for arsenic, as either an agonist or antagonist of HH signaling. Here we provide in vitro and in vivo evidence that arsenic acts as a modulator of the activity of the HH effector protein glioma-associated oncogene family zinc finger (GLI), activating or inhibiting GLI activity in a context-dependent manner. This arsenic-induced modulation of HH signaling is observed in cultured cells, patients with colorectal cancer who have received arsenic-based therapy, and a mouse colorectal cancer xenograft model. Our results show that arsenic activates GLI signaling when the intrinsic GLI activity is low but inhibits signaling in the presence of high-level GLI activity. Furthermore, we show that this modulation occurs downstream of primary cilia, evidenced by experiments in suppressor of fused homolog (SUFU) deficient cells. Combining our findings with previous reports, we present an inclusive model in which arsenic plays dual roles in GLI signaling modulation: when GLIs are primarily in their repressor form, arsenic antagonizes their repression capacity, leading to low-level GLI activation, but when GLIs are primarily in their activator form, arsenic attenuates their activity.

In the war against solid tumors arsenic trioxide needs partners

In the past decade, the therapeutic potential of arsenic trioxide (ATO) in the treatment of acute promyelocytic leukemia (APL) was recognized. This encouraged other investigators to test the efficacy of ATO in the management of other hematological and solid tumor malignancies. Notably, as a single agent, arsenic trioxide did not benefit patients diagnosed with solid tumors. However, when it was combined with other agents, treatment benefit emerged. In this article, we have summarized the outcome of clinical trials that used arsenic trioxide as a single agent as well as in combination settings in patients diagnosed with solid tumors. We have also reviewed possible additional mechanisms by which ATO may be useful as a chemosensitizer in combination therapy. We hope that our review will encourage clinical investigators to rationally combine ATO with additional chemotherapeutic agents in treating patients diagnosed with solid tumors.

Achyranthes aspera (Apamarg) leaf extract inhibits human pancreatic tumor growth in athymic mice by apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Achyranthes aspera (Family Amaranthacea) is used for cancer therapy by ayurvedic medical practitioners in India. However, due to the non formal nature of its use, there are no systematic studies validating its medicinal properties. Thus, it's utility as an anti cancer agent remains anecdotal. Earlier, we demonstrated A. aspera to exhibit time and dose-dependent preferential cytotoxicity to cultured human pancreatic cancer cells. In this report we validate in vivo anti tumor properties of A. aspera.

MATERIALS AND METHODS

The in vivo anti tumor activity of leaf extract (LE) was tested by intraperitoneal (IP) injections into athymic mice harboring human pancreatic tumor subcutaneous xenograft. Toxicity was monitored by recording changes in behavioral, histological, hematological and body weight parameters.

RESULTS

Dosing LE to athymic mice by I.P. injection for 32 days showed no adverse reactions in treated mice. Compared to the control set, IP administration of LE to tumor bearing mice significantly reduced both tumor weight and volume. Gene expression analysis using Real time PCR methods revealed that LE significantly induced caspase-3 mRNA (p<0.001) and suppressed expression of the pro survival kinase Akt-1 (p<0.05). TUNEL assay and immunohistochemistry confirmed apoptosis induction by activation of caspase-3 and inhibiting Akt phosphorylation in treated sets. These results are in agreement with RT PCR data.

CONCLUSION

Taken together, these data suggest A. aspera to have potent anti cancer property.

The presence of three repeats in the 5' UTR region of thymidylate synthase (TS) is associated with increased TS mRNA expression in cultured human cancer cell lines in vitro

Thymidylate synthase (TS) gene contains 28-bp polymorphic sequence and 6-bp insert at the 5'- and 3'-untranslated region, respectively. We investigated the role of these two polymorphic traits on TS mRNA expression in nine different cultured human cancer cell lines in vitro. Three cell lines each were 2R/2R, 2R/3R and 3R/3R genotypes. Six of the nine cell lines tested homozygous for the presence of 6-bp insert (+6/+6) and the rest three lacked this insert (-6/-6). TS expression analyses associated homozygous three repeats (3R/3R) to higher TS expression.

Anti-proliferative and anti-cancer properties of Achyranthes aspera: specific inhibitory activity against pancreatic cancer cells

AIMS OF THE STUDY

Achyranthes aspera (Family: Amaranthacea) is a medicinal plant used as an anti-cancer agent in ayurveda, a traditional system of medicine practiced in subcontinental India. The aim of the study was to systematically investigate the anti-proliferative properties of Achyranthes aspera leaves extracted in methanol (LE) on human cancer cells in vitro.

MATERIALS AND METHODS

We tested time, dose dependent and specific anti-proliferative activity of LE by clonogenic cell survival assay on human cancer and normal epithelial cell lines in vitro. We further investigated its effect on the expression of metastatic and angiogenic genes by real time polymerase chain reaction. On silica gel column, we carried out initial fractionation analysis.

RESULTS

LE exhibited time and dose dependent cytotoxicity on several tumor cells. Compared to cancer cells of colon, breast, lung and prostate origin, pancreatic cancer cells were significantly more sensitive to LE. Preliminary mechanistic studies suggested that LE selectively suppressed the transcription of metalloproteases (MMP-1 and -2), inhibitors of MMPs (TIMP-2) and angiogenic factors (VEGF-A and VEGF-B). Fractionation of LE on methanol equilibrated silica gel column resolved into three fractions of which fraction (F 3) was found to be enriched with anti-proliferative activity.

CONCLUSION

Methanolic extract of Achyranthes aspera contains potent anti-proliferative compound with specific activity against pancreatic cancer. Further studies are needed to confirm the in vivo anti-tumorigenicity and subsequent chemical characterization of the active molecule(s).

Chronic exposure of colorectal cancer cells in culture to fluoropyrimidine analogs induces thymidylate synthase and suppresses p53. A molecular explanation for the mechanism of 5-FU resistance

Resistance to chemotherapy is a major issue in treating malignant diseases. 5-Fluorouracil (5-FU) is the drug of choice in managing colorectal cancer (CRC) patients. However, 5-FU resistance leads to eventual treatment failure. Therefore, delaying or reversing the onset of 5-FU resistance will benefit these terminally ill patient populations. A metabolite of 5-FU irreversibly binds thymidylate synthase (TS) thus inhibiting its activity. Many studies demonstrated that these resistant patients had an increased intratumoral TS level. We used TS-siRNA to reduce TS and resensitize HT29FU CRC cells back to this uracil analogue. We exposed the CRC cell line HT29 to an increasing concentration of 5-FU or 5-fluorouridine (FUR) and established a derivative cell line (HT29FU and HT29FUR). Using real-time polymerase chain reaction (PCR) and Western immunodetection assays, we analyzed the expression of TS and p53 mRNA and protein in control and experimental groups. Cytotoxicity to 5-FU was determined by reduction of 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT assay) or trypan blue dye exclusion assay. The HT29FU and HT29FUR cells have a distinct morphology: they are generally asteroid shaped. The half maximal inhibitory concentration (IC(50)) values for the resistant cell line for 5-FU is over 148 microM compared to 5 microM for the sensitive parental cell line. The resistant cell lines expressed more of TS and less of p53. TS-siRNA suppressed TS only. Other pathways were not significantly altered. It also marginally (20%) re-sensitized resistant cells to 5-FU. Restoration of partial sensitivity to 5-FU by TS-siRNA reiterates the primacy of the DNA synthesis pathway in 5-FU mode of action. We speculate that the short half-life of the transiently transfected siRNA may contribute to the marginal restoration of sensitivity. By integrating TS-siRNA expression vector into the genome and regulating its expression, we may be able to reverse 5-FU resistance and make the cells as sensitive as the parental cell line.

Arsenic trioxide/ascorbic acid therapy in patients with refractory metastatic colorectal carcinoma: a clinical experience

Arsenic trioxide (As2O3) has demonstrated effectiveness in treating acute promyelocytic leukemia (APL). Therefore the FDA has approved it to treat APL. In patients with refractory metastatic colorectal carcinoma (CRC), we assessed the efficacy and toxicity of As2O3/AA (ascorbic acid) as the outcome of this trial. Five patients with refractory metastatic CRC who failed all previous standard chemotherapy were enrolled in this study. They were treated with 0.25 mg/kg body weight/day As2O3 and 1000 mg/day of ascorbic acid for 5 days a week for 5 weeks. Each treatment cycle extended for 7 weeks with 5 weeks of treatment and 2 weeks of rest. All the patients developed moderate to severe toxic side effects to arsenic trioxide/AA therapy and therefore the study was discontinued. No CR (complete remission) or PR (partial remission) was observed. CT scans demonstrated stable or progressive disease. Three of the five patients died within 2 to 5 months after cessation of the therapy. None of the deaths could be related to this clinical trial. Two years of follow-up study showed that two patients were alive with stable disease. Under the current treatment regimen all patients developed moderate to severe side effects with no clinically measurable activity. As an alternate, efforts may be made to reduce the dose and arsenic trioxide may be combined with other standard regimen in reversing the chemo resistance.

Mapping and molecular characterization of novel monoclonal antibodies to conformational epitopes on NH2 and COOH termini of mammalian tryptophanyl-tRNA synthetase reveal link of the epitopes to aggregation and Alzheimer's disease

Tryptophanyl-tRNA synthetase (TrpRS) is an interferon-induced phosphoprotein with autoantigenic and cytokine activities detected in addition to its canonical function in tRNA aminoacylation. The availability of monoclonal antibodies (mAbs) specific for TrpRS is important for development of tools for TrpRS monitoring. A molecular characterization of two mAbs raised in mice, using purified, enzymatically active bovine TrpRS as the inoculating antigen, is presented in this report. These IgG1 antibodies are specific for bovine, human and rabbit but not E. coli TrpRS. Immunoreactivity and specificity of mAbs were verified with purified recombinant hTrpRS expressed in E. coli and TrpRS-derived synthetic peptides. One of the mAbs, 9D7 is able to disaggregate fibrils formed by Ser32-Tyr50 TrpRS-peptide. Epitope mapping revealed that disaggregation ability correlates with binding of 9D7 to this peptide in ELISA and immunocytochemistry. This epitope covers a significant part of N-terminal extension that suggested to be proteolytically deleted in vivo from the full-length TrpRS whereas remaining COOH-fragment possesses a cytokine activity. For epitope mapping of mAb 6C10, the affinity selected phage-displayed peptides were used as a database for prediction of conformational discontinuous epitopes within hTrpRS crystal structure. Using computer algorithm, this epitope is attributed to COOH-terminal residues Asp409-Met425. In immunoblotting, the 6C10 mAb reacts preferably with (i) oligomer than monomer, and (ii) bound than free TrpRS forms. The hTrpRS expression was shown to correlate with growth rates of neuroblastoma and pancreatic cancer cells. Immunohistochemically both mAbs revealed extracellular plaque-like aggregates in hippocampus of Alzheimer's disease brain.

A comparative study of variation in codon 33 of the rpoS gene in Escherichia coli K12 stocks: implications for the synthesis of sigma(s)

The Escherichia coli rpoS gene encodes an RNA polymerase sigma factor (sigma S or sigma(S)) required for the expression of stationary-phase genes. In the first published rpoS sequence from E. coli K-12 codon 33 is given as CAG. However, several subsequent independent studies found the amber codon TAG at this position ( rpoSAm). Besides this amber codon, other codons such as TAT have also been found at this location in rpoS. Comparative genome analysis now leads us to propose TAG as the parental codon 33 in rpoS in E. coli K-12. Five different stocks of the strain W3110, which differ in the levels of sigma(S) protein they express, were investigated. We sequenced the rpoS gene from these, and found a T at nucleotide position 97 in four out of the five stocks and a G at position 99 in three out of the five. W1485, a parental strain of W3110, and W3350, a derivative of W3110, are also rpoSAm mutants. Such rpoSAm mutants would be expected to show no RpoS activity. The retention of partial or intermediate sigma(S) activity by suppressor-free rpoSAm mutants is therefore puzzling. We propose that a functional, N-terminally truncated, sigma(S) (Delta1-53sigma(S)) can be translated from a Secondary Translation Initiation Region (STIR) located downstream of the amber codon 33. It has recently been reported that a fragment of RpoS (Delta1-53sigma(S)) that lacks the first 53 amino acids is functional when synthesized in vivo. Taken together, our results support the hypothesis that the original codon 33 of the rpoS gene in E. coli K-12 strains is the amber codon TAG.

In vitro properties of RpoS (sigma(S)) mutants of Escherichia coli with postulated N-terminal subregion 1.1 or C-terminal region 4 deleted

Derivatives of the stationary-phase sigma factor sigma(S) of Escherichia coli lacking either of two conserved domains, the postulated N-terminal subregion 1.1 or the C-terminal region 4, were shown to be competent in vitro for transcription initiation from several sigma(S)-dependent promoters on supercoiled DNA templates. Unlike wild-type sigma(S), however, the deletion derivatives were inactive on relaxed templates. The anomalous slow electrophoretic mobility of sigma(S) on denaturing gels was corrected by deletion of subregion 1.1, suggesting that this domain in sigma(S) may be structurally and functionally analogous to subregion 1.1 of sigma(70), substitutions in which have previously been shown to rectify the anomalous electrophoretic migration of sigma(70) (V. Gopal and D. Chatterji, Eur. J. Biochem. 244:614-618, 1997).

Escherichia coli RNase M is a multiply altered form of RNase I

RNase M, an enzyme previously purified to homogeneity from Escherichia coli, was suggested to be the RNase responsible for mRNA degradation in this bacterium. Although related to the endoribonuclease, RNase I, its distinct properties led to the conclusion that RNase M was a second, low molecular mass, broad specificity endoribonuclease present in E. coli. However, based on sequence analysis, southern hybridization, and enzyme activity, we show that RNase M is, in fact, a multiply altered form of RNase I. In addition to three amino acid substitutions that confer the properties of RNase M on the mutated RNase I, the protein is synthesized from an rna gene that contains a UGA nonsense codon at position 5, apparently as a result of a low level of readthrough. We also suggest that RNase M is just one of several previously described endoribonuclease activities that are actually manifestations of RNase I.

Report on a patient with paroxysmal cold hemoglobinuria

Antibodies against the human blood group P antigen (anti-P alloantibodies) agglutinate phenotype P1 and P2 erythrocytes treated with papain at 4 degrees C but not phenotype PK and p erythrocytes. This condition is referred to as an autoimmune disease of paroxysmal cold hemoglobinuria (PCH), and the anti-P specificity is found in the cold hemagglutinins. Serum from a patient suspected to be suffering from PCH by the cold auto-agglutination properties was tested for anti-P specificity, using papain-treated O blood group erythrocytes. The serum-mediated hemagglutination and the serum and complement-mediated immunohemolysis were inhibited by globoside (P antigen GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc-ceramide) and Forssman glycosphingolipid (GalNAc alpha 1-3GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc-ceramide). Therefore, we concluded that she had PCH. She was completely cured 6 months later.

Analysis of transfer RNA during the early embryogenesis of the freshwater teleost, Heteropneustes fossilis

Total RNA as well as transfer RNA were quantified from mature ova apart from four different embryonic stages namely mid-cleavage, early gastrula, mid-gastrula and organogenesis of the freshwater teleost Heteropneustes fossilis. Total RNA as well as transfer RNA quantity follow a similar variation pattern, being maximum during mid-gastrulation. When analysed by total amino acid acceptance capacity, transfer RNA shows its maximum activity during mid-gastrulation. This coincides with the higher ratio of tRNA to total RNA at this stage. The relative aminoacylation capacity for Ser, Gly, Asn and Thr are found to be higher (9-34%) compared to that for other amino acids. Total tRNA, resolved into three peaks upon HPLC fractionation, shows a high cumulative peak area during mid-gastrulation and organogenesis. These results indicate a switch over of maternal to embryonic translation machinery during gastrulation.

Transfer RNA analysis during the reproductive cycle of a freshwater teleost, H. fossilis

Transfer RNA was analyzed qualitatively as well as quantitatively from ovaries of the fresh water teleost Heteropneustes fossilis for twelve months. The tRNA samples were found to be pure and devoid of any high molecular weight RNA or DNA contaminations. The quantity of tRNA as well as its biological activity, assayed by in vitro aminoacylation using homologous aminoacyl tRNA synthetases, were found to be higher during resting and preparatory (pre-vitellogenic) phases, i.e. from November to March, as compared to vitellogenic and spawning phases of the fish, i.e. from April to October. The highest tRNA pool and its activity was found in the month of February, which coincides with the early preparatory phase. The results indicate that the accumulation of active tRNA starts in the resting phase. Such an accumulation of tRNA may be a part of the enrichment of mature eggs with complete translational machinery before ovulation in order to cope with the high rate of protein synthesis after fertilization.