The rb pathway and cancer therapeutics

The retinoblastoma gene, Rb, was originally identified as the tumor suppressor gene mutated in a rare childhood cancer called retinoblastoma (reviewed in [1]). Subsequent studies showed that Rb functions in a pathway that is often functionally inactivated in a large majority of human cancers. Interestingly, recent studies showed that in certain types of cancers, Rb function is actually required for cancer development. The intimate link between the Rb pathway and cancer development suggests that the status of Rb activity can potentially be used to develop targeted therapy. However, a prerequisite will be to understand the role of Rb and its interaction with other signaling pathways in cancer development. In this review, we will discuss the roles of Rb in proliferation, apoptosis and differentiation by reviewing the recent findings in both mammalian systems and different model organisms. In addition, we will discuss strategies that can be employed that specifically target cancer cells based on the status of the Rb pathway.

Suppression of p53 activity by Siva1

The tumor suppressor p53 induces potent anti-proliferative responses in stressed cells; in unstressed cells this ability of p53 is restrained by Hdm2. Expression of Hdm2 is also induced by p53, thereby establishing feedback inhibition. Regulation of the p53-Hdm2 interaction and the feedback inhibition of p53 are not well understood. Here, we show that the p53-Hdm2 interaction in unstressed cells is promoted by Siva1, which, like Hdm2, is the product of a p53 target gene. Siva1 binds to both p53 and Hdm2 through distinct regions and enhances Hdm2-mediated p53 ubiquitination and degradation. Siva1 strongly inhibits p53-mediated gene expression and apoptosis. In xenograft mouse models, downregulation of Siva1 markedly inhibits tumor formation because of the activation of p53. On DNA damage, the interactions of Siva1 with both p53 and Hdm2 are diminished. The function of Siva1 seems to be related to its ability to form a homo-oligomer as the oligomerization defective splicing variant Siva2 fails to de-stabilize p53. These results identify Siva1 as an important adaptor promoting p53 degradation through Hdm2. Siva1 may be part of the negative feedback loop that inhibits p53 activity at the end of a non-lethal stress response.

Function and regulation of aflJ in the accumulation of aflatoxin early pathway intermediate in Aspergillus flavus

aflJ resides within the aflatoxin biosynthetic gene cluster adjacent to the pathway regulatory gene aflR and is involved in aflatoxin production, but its function is unknown. Over-expression of aflJ in the aflatoxin-producing strain 86-10 resulted in increased aflatoxin. In an effort to study the function and regulation of aflJ, strain 649-1 lacking the entire biosynthetic cluster was transformed with either reporter constructs, expression constructs, or cosmid clones and analysed for gene expression or metabolite accumulation. Over-expression of aflJ did not result in elevated transcription of ver-1, omtA or aflR. To determine if over-expression of aflJ leads to an increase in early pathway intermediates, strain 649-1 was transformed with cosmid 5E6 and either gpdA::aflJ alone, gpdA::aflR alone, or aflJ and aflR together. Cosmid 5E6 contains the genes pksA, nor-1, fas-1, and fas-2, which are required for the biosynthesis of the early pathway intermediate averantin. 649-1 transformants containing 5E6 alone produced no detectable averantin. In contrast, 5E6 transformants with gpdA::aflR produced averantin, but only half as much as those transformants containing both aflR and aflJ. Northern blot analysis showed that 5E6 transformants containing both aflR and aflJ had five times more pksA transcripts and four times more nor-1 transcripts than 5E6 transformants containing gpdA::aflR alone. Further, aflJ transcription was regulated by aflR. Over-expression of aflR resulted in elevated aflJ transcription. aflJ appears to modulate the regulation of early genes in aflatoxin biosynthesis.

A comparative study on Pb2+, Zn2+ and Cd2+ sorption onto zirconium phosphate supported by a cation exchanger

In the present study, a novel hybrid sorbent ZrP-001 was prepared by loading zirconium phosphate (ZrP) onto a strongly acidic cation exchanger D-001. Sorption behavior of Pb(2+), Zn(2+), and Cd(2+) onto ZrP-001 was experimentally examined by comparing with the host exchanger D-001. ZrP-001 was characterized by scanning electron micrograph (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), pH-titration and pore size distribution analysis. Sorption of the heavy metals onto ZrP-001 was found to be pH-dependent due to the ion exchange mechanism. Compared to D-001, a smaller pore size of ZrP-001 due to the ZrP dispersion consequently resulted in a lower sorption rate. Competitive effect of Ca(2+) on sorption of heavy metals onto ZrP-001 and D-001 was compared to elucidate sorption preference of the hybrid sorbent towards heavy metals. More favorable sorption of ZrP-001 than D-001 was observed for all the three metals and their sorption preference onto ZrP-001 followed the order Pb(2+)>>Zn(2+) approximately Cd(2+). Fixed-bed sorption results and its efficient regeneration property further demonstrated that ZrP-001 is a potential candidate for removing heavy metals from contaminated water.

Progesterone and 17beta-estradiol, but not follicle stimulating hormone, alter the sex ratio of murine embryos fertilized in vitro

The objective was to determine the effects of adding progesterone, 17beta-estradiol (17beta-E2), and FSH during in vitro fertilization on development and sex ratio of murine embryos. Progesterone (33-330 pg/mL), 17beta-estradiol (17beta-E2); 10-70 pg/mL), and FSH (0.01-0.05 IU/mL), were added to human tubal fluid (HTF); this medium (with or without hormones) was used to pre-incubate sperm (2h) and to co-incubate sperm and oocytes (6h). Thereafter, the ova were washed and incubated in mM16 medium and embryo sex was determined (by PCR) on Day 4 (insemination=Day 0). There was no effect (P>0.05) of hormone treatments on rates of cleavage (6 h after cessation of co-incubation with sperm). The only significant effects of added hormones on development were a decrease in the rate of development to at least the morula stage in 165 pg/mL progesterone (0.46+/-0.03 vs. 0.54+/-0.05 in the control, mean+/-S.D.; P<0.05) and a decrease in the blastocyst rate in 0.03 IU/mL FSH (0.34+/-0.00 vs. 0.42+/-0.04 in the control, P<0.05). However, the ratio of male to female embryos was 1.61 and 2.90 following the addition of 99 pg/mL progesterone and 70 pg/mL 17beta-E2, respectively; both of these ratios were different (P<0.01) than in the control group (1.20). In contrast, the addition of FSH to the medium had no significant effect on this ratio (range, 0.78-1.02). We concluded that the addition of progesterone and estradiol to the media during in vitro fertilization did not enhance embryonic development, but significantly increased the proportion of male murine embryos.

Defective response to Toll-like receptor 3 and 4 ligands by activated monocytes in chronic hepatitis C virus infection

Toll-like receptors (TLR) have a critical role in innate immunity against pathogens. We investigated the cytokine response to TLR stimulation in peripheral blood cells of subjects infected with hepatitis C virus (HCV) and/or human immunodeficiency virus (HIV) in the Women Interagency HIV Study (WIHS) cohort. Interleukin (IL)-6 in response to TLR3 and TLR4 ligands such as polyinosinic-polycytidylic acid and lipopolysaccharide was significantly compromised in HCV-infected women. High spontaneous secretion of IL-6 suggested pre-existing cell activation as a factor mediating reduced responses to TLR3 and TLR4 stimulation. To a lesser extent, tumour necrosis factor-alpha and IL-1beta responses to TLR stimulation were also compromised. Monocytes, but not B cells or NK cells, were identified as the cell population spontaneously secreting cytokines and also as the cells responding to TLR stimulation. These results highlight a functional defect in antigen-presenting cells of women with HCV infection or co-infection. In women with existing HIV co-infection, decreased cytokine function of antigen-presenting cells suggests another mechanism contributing to immune dysfunction in addition to the HIV-associated CD4 defect.

Effect of alvimopan (ALV) on gastrointestinal (GI) recovery, length of hospital stay (LOS), and postoperative ileus (POI)-related morbidity in patients (PTS) undergoing bowel resection (BR) for colon or rectal cancer (CRC)

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Background: POI, an interruption of bowel motility, occurs universally after BR and is exacerbated by exogenous opioid analgesia. ALV, a peripherally acting mu-opioid receptor (PAM-OR) antagonist, accelerated GI recovery after BR in multicenter, randomized phase III efficacy trials. CRC is the most common reason for BR in the US, and in the ALV trials CRC was the primary reason for BR for 723 of 1,409 (51%) PTS. This abstract examines GI recovery, LOS, POI-related morbidity, and safety in only this subset of PTS. Methods: This pooled ad hoc analysis assessed the subset of PTS in phase III ALV trials who underwent BR via laparotomy because of CRC and received ALV 12 mg or placebo (PLA) (N = 723). All PTS were scheduled for postoperative intravenous patient-controlled opioid analgesia and received oral ALV or PLA preoperatively and BID postoperatively until hospital discharge or for = 7 postoperative days. Efficacy endpoints included GI-2 recovery (first bowel movement and tolerance of solid food) and postoperative LOS (calendar day after surgery to hospital discharge order written). Treatment effect on GI-2 recovery was analyzed using Cox proportional hazards models, and magnitude of effect was expressed with Kaplan-Meier means. POI-related morbidity included nasogastric tube insertion or complications of POI resulting in prolonged hospital stay or readmission. Safety was monitored by adverse event reports. Conclusions: ALV significantly accelerated GI recovery, reduced postoperative LOS, and reduced the proportion of PTS with POI-related morbidity compared with PLA in PTS undergoing BR for CRC. ALV was well tolerated with a lower incidence of nausea and vomiting in the ALV group than in the PLA group.

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No significant financial relationships to disclose.

Highly effective removal of heavy metals by polymer-based zirconium phosphate: A case study of lead ion

Zirconium phosphate (ZrP) has recently been demonstrated as an excellent sorbent for heavy metals due to its high selectivity, high thermal stability, and absolute insolubility in water. However, it cannot be readily adopted in fixed beds or any other flowthrough system due to the excessive pressure drop and poor mechanical strength resulting from its fine submicrometer particle sizes. In the present study a hybrid sorbent, i.e., polymer-supported ZrP, was prepared by dispersing ZrP within a strongly acidic cation exchanger D-001 and used for enhanced lead removal from contaminated waters. D-001 was selected as a host material for sorbent preparation mainly because of the Donnan membrane effect resulting from the nondiffusible negatively charged sulfonic acid group on the exchanger surface, which would enhance permeation of the targeted metal ions. The hybrid sorbent (hereafter denoted ZrP-001) was characterized using a nitrogen adsorption technique, scanning electron microscope (SEM), and X-ray diffraction (XRD). Lead sorption onto ZrP-001 was found to be pH dependent due to the ion-exchange mechanism, and its sorption kinetics onto ZrP-001 followed the pseudo-first-order model. Compared to D-001, ZrP-001 exhibited more favorable lead sorption particularly in terms of high selectivity, as indicated by its substantially larger distribution coefficients when other competing cations Na(+), Ca(2+), and Mg(2+) coexisted at a high level in solution. Fixed-bed column runs showed that lead sorption on ZrP-001 resulted in a conspicuous decrease of this toxic metal from 40 mg/L to below 0.05 mg/L. By comparison with D-001 and ZrP-CP (ZrP dispersion within a neutrally charged polymer CP), enhanced removal efficiency of ZrP-001 resulted from the Donnan membrane effect of the host material D-001. Moreover, its feasible regeneration by diluted acid solution and negligible ZrP loss during operation also helps ZrP-001 to be a potential candidate for lead removal from water. Thus, all the results suggested that ZrP-001 offers excellent potential for lead removal from contaminated water.

Nuclear reprogramming in embryos generated by the transfer of yak (Bos grunniens) nuclei into bovine oocytes and comparison with bovine–bovine SCNT and bovine IVF embryos

Although inter-species SCNT may be useful for increasing and preserving populations of endangered species, there are many reports that inter-species nuclear transfer embryos only develop to the blastocyst stage. In this study, yak-bovine SCNT blastocysts were successfully implanted in the surrogate bovine uterus but failed to develop to term or aborted. To clarify the reasons, we examined yak-bovine SCNT blastocyst development, total cell number, inner cell mass (ICM) number, trophoblast (TE) cell number and relative gene expression in yak fibroblast cells and yak-bovine SCNT embryos at various stages. The potential for development of yak-bovine SCNT embryos to blastocysts was 30+/-5.7% (mean+/-S.E.M.); the total cell number was 85.3+/-16.3, fewer than in IVF bovine embryos (106.2+/-18.2) but within the reported range (60-300). The yak-bovine SCNT blastocysts had a lower ratio of TE cells to total cells (43.9+/-8.7%) than bovine IVF embryos (59.4+/-3.4%; P<0.05) or bovine-bovine SCNT (69.5+/-5.4%; P<0.05). Also, several yak-bovine SCNT embryos had abnormal initiation of expression of both Mash2 and IL6. However, expression of vimentin, collagen, Cx43 and PSMC3 were normal in yak fibroblast cells and yak-bovine SCNT embryos. In conclusion, we inferred that the normal allocation of ICM and TE cells in yak-bovine SCNT embryos and embryo-specific gene reprogramming may be important for successful inter-species animal cloning.

Modeling synergistic adsorption of phenol/aniline mixtures in the aqueous phase onto porous polymer adsorbents

The adsorption equilibria of phenol and aniline on nonpolar polymer adsorbents (NDA-100, XAD-4, NDA-16 and NDA-1800) were investigated in single- and binary-solute adsorption systems at 313 K. The results showed that all the adsorption isotherms of phenol and aniline on these adsorbents can be well fitted by Freundlich and Langmuir equations, and the experimental uptake of phenol and aniline in all binary-component systems is obviously higher than predicted by the extended Langmuir model, arising presumably from the synergistic effect caused by the laterally acid-base interaction between the adsorbed phenol and aniline molecules. A new model (MELM) was developed to quantitatively describe the synergistic adsorption behavior of phenol/aniline equimolar mixtures in the binary-solute systems and showed a marked improvement in correlating the binary-solute adsorption of phenol and aniline by comparison with the widely used extended Langmuir model. The newly developed model confirms that the synergistic coefficient of one adsorbate is linearly correlated with the adsorbed amount of the other, and the larger average pore size of adsorbent results in the greater synergistic effect of phenol/aniline equimolar mixtures adsorption.

Retinoblastoma family genes

The retinoblastoma gene Rb was the first tumor suppressor gene cloned, and it is well known as a negative regulator of the cell cycle through its ability to bind the transcription factor E2F and repress transcription of genes required for S phase. Although over 100 other proteins have been reported to interact with Rb, in most cases these interactions are much less well characterized. Therefore, this review will primarily focus on Rb and E2F interactions. In addition to cell cycle regulation, studies of Rb and E2F proteins in animal models have revealed important roles for these proteins in apoptosis and differentiation. Recent screens of Rb/E2F target genes have identified new targets in all these areas. In addition, the mechanisms determining how different subsets of target genes are regulated under different conditions have only begun to be addressed and offer exciting possibilities for future research.