Nonlinear modelling of cancer: bridging the gap between cells and tumours

Despite major scientific, medical and technological advances over the last few decades, a cure for cancer remains elusive. The disease initiation is complex, and including initiation and avascular growth, onset of hypoxia and acidosis due to accumulation of cells beyond normal physiological conditions, inducement of angiogenesis from the surrounding vasculature, tumour vascularization and further growth, and invasion of surrounding tissue and metastasis. Although the focus historically has been to study these events through experimental and clinical observations, mathematical modelling and simulation that enable analysis at multiple time and spatial scales have also complemented these efforts. Here, we provide an overview of this multiscale modelling focusing on the growth phase of tumours and bypassing the initial stage of tumourigenesis. While we briefly review discrete modelling, our focus is on the continuum approach. We limit the scope further by considering models of tumour progression that do not distinguish tumour cells by their age. We also do not consider immune system interactions nor do we describe models of therapy. We do discuss hybrid-modelling frameworks, where the tumour tissue is modelled using both discrete (cell-scale) and continuum (tumour-scale) elements, thus connecting the micrometre to the centimetre tumour scale. We review recent examples that incorporate experimental data into model parameters. We show that recent mathematical modelling predicts that transport limitations of cell nutrients, oxygen and growth factors may result in cell death that leads to morphological instability, providing a mechanism for invasion via tumour fingering and fragmentation. These conditions induce selection pressure for cell survivability, and may lead to additional genetic mutations. Mathematical modelling further shows that parameters that control the tumour mass shape also control its ability to invade. Thus, tumour morphology may serve as a predictor of invasiveness and treatment prognosis.

Azimuthal charged-particle correlations and possible local strong parity violation

Parity-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the system's orbital momentum axis. We investigate a three-particle azimuthal correlator which is a P even observable, but directly sensitive to the charge separation effect. We report measurements of charged hadrons near center-of-mass rapidity with this observable in Au + Au and Cu + Cu collisions at square root of s(NN) = 200 GeV using the STAR detector. A signal consistent with several expectations from the theory is detected. We discuss possible contributions from other effects that are not related to parity violation.

Growth of long range forward-backward multiplicity correlations with centrality in Au + Au collisions at square root of sNN = 200 GeV

Forward-backward multiplicity correlation strengths have been measured with the STAR detector for Au + Au and p + p collisions at square root of s(NN) = 200 GeV. Strong short- and long-range correlations (LRC) are seen in central Au + Au collisions. The magnitude of these correlations decrease with decreasing centrality until only short-range correlations are observed in peripheral Au + Au collisions. Both the dual parton model (DPM) and the color glass condensate (CGC) predict the existence of the long-range correlations. In the DPM, the fluctuation in the number of elementary (parton) inelastic collisions produces the LRC. In the CGC, longitudinal color flux tubes generate the LRC. The data are in qualitative agreement with the predictions of the DPM and indicate the presence of multiple parton interactions.

K/pi Fluctuations at relativistic energies

We report K/pi fluctuations from Au + Au collisions at sqrt[s(NN)]= 19.6, 62.4, 130, and 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. K/pi fluctuations in central collisions show little dependence on incident energy and are on the same order as those from NA49 at the Super Proton Synchrotron in central Pb + Pb collisions at sqrt[s(NN)]=12.3 and 17.3 GeV. We report results for the collision centrality dependence of K/pi fluctuations and results for charge-separated fluctuations. We observe that the K/pi fluctuations scale with the charged particle multiplicity density.

RUS skeletal maturity of children in Beijing

BACKGROUND

RUS (radius-ulna-short bones) maturity of children has been estimated in two provinces in China, but not in the capital. In order to obtain a clearer picture of skeletal maturity in China, it is indispensable to include children from Beijing in the study.

AIM

The aims of this study were three-fold: (1) to establish RUS skeletal maturity of children in Beijing, (2) to compare RUS skeletal maturity in Beijing with the Tanner-Whitehouse 3 (TW3) standard and the Tokyo standard, and (3) to examine regional variation in skeletal maturity in China.

METHODS

Hand and wrist radiographs of 631 boys and 642 girls, aged 6-18, were obtained in Beijing in 1997, and their RUS skeletal maturity was estimated using the TW3 method.

RESULTS

RUS maturity of the Beijing children was very similar to the TW3 standard until the age of 10 years in the girls, and the age of 12 years in the boys. The girls attained full maturity at 15 years of age, matching the TW3 and Tokyo standards, while the boys reached full maturity at the age of 16 years, as in Tokyo boys, but 1 year earlier than the TW3 standards. Beijing children showed progressively more rapid bone maturation than the Harbin and Changsha children, and attained full maturation 1 year earlier, in both girls and boys.

CONCLUSION

The RUS maturity of the Beijing children was comparable with that of Tokyo children, except for the boys between 11 and 13 years. Variability of the RUS maturation among the Chinese children was greater than that found among the TW3, Tokyo and Beijing children.

In vitro analysis of cidofovir and genetically engineered TK expression as potential approaches for the intervention of ColoAd1-based treatment of cancer

We have generated a novel oncolytic Adenovirus (Ad), ColoAd1, with significantly increased potency ( approximately 100-fold) relative to its parent viruses, Ad11p and Ad3, or to the clinically tested oncolytic Ad, ONYX-015. Although this agent has a significant increase in its therapeutic window relative to ONYX-015 or its parent viruses, its ability to intervene and control virotherapy in treated patient is an important safety consideration for a novel biological therapy, such as ColoAd1. As there are no approved treatments for Ad infections, we sought to define whether antivirals being used to experimentally treat Ad infections (cidofovir (CDV), ribavirin) had any activity against ColoAd1. In addition, we incorporated a well-described pro-drug converting enzyme, the herpes simplex virus-thymidine kinase (HSV-TK) gene, into the viral genome to test whether the expression of this enzyme directly from the virus could be exploited as a safety valve for arresting the viral infection in the presence of the pro-drug, ganciclovir. Both the antiviral drug, CDV, and the incorporation of the pro-drug-converting TK enzyme were validated as effective approaches to controlling ColoAd1 infection, and this represents an important advancement in the development of ColoAd1 as an anticancer treatment.

Testing for HIV and sexually transmissible infections within a mainly online sample of gay men who engage in group sex

INTRODUCTION

Group sex among gay men has been associated with other HIV risk behaviours. Gay men who engage in group sex may be at increased risk of infection with HIV and other sexually transmitted infections (STI).

METHODS

The Three or More Study (TOMS) of group sex among gay men utilised an anonymous, self-completed survey about participants' most recent occasion of group sex with other men and in-depth interviews with a small number of these survey participants. The 436 men who reported having engaged in group sex within the previous month were included in these analyses.

RESULTS

Among 436 men who engaged in group sex within the previous month, 32.5% reported unprotected anal intercourse (UAI) with non-regular, mostly HIV non-seroconcordant partners at this recent group sex encounter (GSE) and the majority reported other sex practices that are risk factors for STI other than HIV. Over one-third reported having been tested for HIV or other STI since their last GSE; those who had engaged in UAI at the GSE were more likely to have been tested (p = 0.008). Men who had a doctor with whom they were able to discuss their group sex activities had received a broader range of STI tests (p = 0.003).

CONCLUSION

Sex practices that risk the transmission of STI were common within this high-risk sample, whereas awareness of risk and the need for testing was high but not universal. Frank discussion with doctors of patients' group sex behaviour also enhanced decisions about adequate testing. Gay men in group sex networks are an appropriate priority for sexual health screening.

Anal human papillomavirus genotype diversity and co-infection in a community-based sample of homosexual men

OBJECTIVES

To determine the prevalence and risk factors for anal human papillomavirus (HPV) infection in community-based cohorts of homosexual men in Sydney, Australia.

METHODS

A cross-sectional study in consecutively presenting participants in the positive Health and Health in Men cohorts in 2005. HPV testing was performed on anal PreservCyt specimens collected from 316 homosexual men (193 HIV-negative, 123 HIV-positive) using the Digene Hybrid Capture 2 (HC-2) assay for detection of low-risk (LR) and high-risk (HR) genotypes. HPV genotype testing was also performed on a subset of 133 men (93 HIV-negative, 36 HIV-positive) using Roche Linear Array (LA) assay.

RESULTS

HC-2 detected HPV infection in 79% of men (LR 55%, HR 69%). HIV-positive men were more likely than HIV-negative men to have LR-HPV (OR 3.5, 95% CI 2.1 to 5.7) and HR-HPV (OR 5.5, 95% CI 3.0 to 10.2). LA detected HPV infection in 95% of men (LR 85%, HR 77%). HIV-positive men had a mean of 7.1 HPV types compared to 4.2 in HIV-negative men; the difference was significant for both LR-HPV (p<0.001) and HR-HPV (p<0.001). HPV-16 was detected in 36% of HIV-positive and 27% of HIV-negative men. There was no consistent trend in HPV prevalence with increasing age. HR-HPV detection was associated with anal bleeding for HIV-positive men and anal warts for HIV-negative men.

CONCLUSIONS

Anal HPV infection was nearly universal in this community-based sample of homosexual men. A wide variety of HPV genotypes were detected, and co-infection with multiple genotypes was common. Anal HPV infection is more prevalent and more diverse in HIV-positive than HIV-negative homosexual men.

Observation of two-source interference in the photoproduction reaction AuAu --> AuAurho0

In ultraperipheral relativistic heavy-ion collisions, a photon from the electromagnetic field of one nucleus can fluctuate to a quark-antiquark pair and scatter from the other nucleus, emerging as a rho{0}. The rho{0} production occurs in two well-separated (median impact parameters of 20 and 40 F for the cases considered here) nuclei, so the system forms a two-source interferometer. At low transverse momenta, the two amplitudes interfere destructively, suppressing rho{0} production. Since the rho{0} decays before the production amplitudes from the two sources can overlap, the two-pion system can only be described with an entangled nonlocal wave function, and is thus an example of the Einstein-Podolsky-Rosen paradox. We observe this suppression in 200 GeV per nucleon-pair gold-gold collisions. The interference is 87%+/-5%(stat.)+/-8%(syst.) of the expected level. This translates into a limit on decoherence due to wave function collapse or other factors of 23% at the 90% confidence level.

Indications of conical emission of charged hadrons at the BNL relativistic heavy ion collider

Three-particle azimuthal correlation measurements with a high transverse momentum trigger particle are reported for pp, d+Au, and Au+Au collisions at sqrt[s_{NN}]=200 GeV by the STAR experiment. Dijet structures are observed in pp, d+Au and peripheral Au+Au collisions. An additional structure is observed in central Au+Au data, signaling conical emission of correlated charged hadrons. The conical emission angle is found to be theta=1.37+/-0.02(stat)-0.07+0.06(syst), independent of p_{ perpendicular}.

System-size independence of directed flow measured at the BNL relativistic heavy-ion collider

We measure directed flow (v_{1}) for charged particles in Au+Au and Cu+Cu collisions at sqrt[s_{NN}]=200 and 62.4 GeV, as a function of pseudorapidity (eta), transverse momentum (p_{t}), and collision centrality, based on data from the STAR experiment. We find that the directed flow depends on the incident energy but, contrary to all available model implementations, not on the size of the colliding system at a given centrality. We extend the validity of the limiting fragmentation concept to v_{1} in different collision systems, and investigate possible explanations for the observed sign change in v_{1}(p_{t}).

Forward neutral-pion transverse single-spin asymmetries in p + p collisions at sqrt[s] = 200 GeV

We report precision measurements of the Feynman x (xF) dependence, and first measurements of the transverse momentum (pT) dependence, of transverse single-spin asymmetries for the production of pi0 mesons from polarized proton collisions at sqrt[s] = 200 GeV. The xF dependence of the results is in fair agreement with perturbative QCD model calculations that identify orbital motion of quarks and gluons within the proton as the origin of the spin effects. Results for the pT dependence at fixed xF are not consistent with these same perturbative QCD-based calculations.

Growth inhibition of an established A431 xenograft tumor by a full-length anti-EGFR antibody following gene delivery by AAV

Therapeutic monoclonal antibodies continue to achieve clinical success for the treatment of many different diseases, particularly cancer. However, the production and purification of antibodies continues to be a time and labor-intensive process with considerable technical challenges. Gene-based delivery of antibodies may address this, via direct production within the host that achieves therapeutic levels. In this report, we validate the feasibility that gene-based delivery is a viable approach for efficacious delivery of antibodies in the preclinical and, presumably, clinical setting. We demonstrate high and sustained in vivo expression of the murine antihuman epidermal growth factor receptor antibody 14E1 following intramuscular delivery by adeno-associated virus (AAV) 2/1. Incorporating the Furin/2A technology for monocistronic expression of both heavy and light chains, we achieved sustained serum levels of full-length 14E1 peaking over 1 mg ml(-1) in athymic nude mice. In the A431 xenograft tumor model, 14E1 was capable of significantly inhibiting tumor growth and prolonging survival when AAV was administered prior to tumor challenge. Furthermore, 14E1 demonstrated significant antitumor efficacy against well-established tumors (approximately 400 mm(3)) when AAV was administered up to 20 days after tumor challenge. Here we demonstrate for the first time growth inhibition of a well-established tumor by a full-length antibody following delivery by AAV.