HPV16 E7 Nucleotide Variants Found in Cancer-Free Subjects Affect E7 Protein Expression and Transformation

The human papillomavirus (HPV) type 16 E7 oncogene is critical to carcinogenesis and highly conserved. Previous studies identified a preponderance of non-synonymous E7 variants amongst HPV16-positive cancer-free controls compared to those with cervical cancer. To investigate the function of E7 variants, we constructed full-length HPV16 E7 genes and tested variants at positions H9R, D21N, N29S, E33K, T56I, D62N, S63F, S63P, T64M, E80K, D81N, P92L, and P92S (found only in controls); D14E, N29H (CIN2), and P6L, H51N, R77S (CIN3). We determined the steady-state level of cytoplasmic and nuclear HPV16 E7 protein. All variants from the controls showed a reduced level of steady-state E7 protein, with 7/13 variants having deficient protein levels. In contrast, 2/3 variants from the CIN3 precancer group had near-normal E7 levels. We assayed the activity of representative variants in stably transfected NIH3T3 cells. The H9R, E33K, P92L, and P92S variants found in control subjects had lower transforming activity than D14E and N29H variants (CIN2); and the R77S (CIN3) had activity only slightly reduced from wildtype E7. In addition, R77S and WT E7 caused increased migration of NIH3T3 cells in a wound-healing assay as compared with H9R, E33K, P92L, and P92S (controls) and D14E (CIN2). These data provide evidence that the E7 variants found in HPV16-positive cancer-free women are partially defective for transformation and cell migration further demonstrating the importance of fully active E7 in clinical cancer development.

Modeling the Degradation Effects of Autophagosome Tethering Compounds (ATTEC)

Autophagy is a powerful protein degradation pathway with limited specificity. Our recent study proposed and demonstrated a potential strategy to harness autophagy to selectively degrade a specific pathogenic protein using autophagosome tethering compounds (ATTEC). ATTEC interact with both the target protein and the autophagosome protein LC3, and thus tether the target protein to the autophagosomes for subsequent degradation. The concentration-dependent curve of the target protein is U-shaped, but there has been lack of both kinetic and steady-state modeling of the degradation effects of ATTEC. Here we established a simplified model describing the kinetics and steady-state level of target protein, and characterized how compounds’ properties, especially binding affinities to LC3 and to the target protein, may influence their degradation effects.

MODELLING THE EFFECTS OF HCV PLUS-STRAND RNA INFLUX INTO A CELL DURING HCV REPLICATION

This paper presents a sub-genomic Hepatitis C Virus (HCV) replication model which incorporates the rate of influx of HCV plus-strand RNA into Huh-7 cell and monitored its effects. The schematic diagram of HCV replication has been simplified. The model exhibits three equilibrium, namely: trivial equilibrium, healthy equilibrium and endemic equilibrium. Stability analysis of the model shows that the healthy equilibrium is globally asymptotically stable under certain condition. It is shown that increase in the rate of influx, increases the steady state level of total plus strand RNA, synthesized plus strand RNA, replicated plus strand RNA and NS5B in the system. Sensitivity and uncertainty analyses of the model (using the \textit{basic replication number} (${\mathcal R}_0$) as the response function) show that the top three PRCC-ranked parameters are the rate of influx, $k_0$ of HCV plus-strand RNA, the rate of production of translation complex ($T_c$) and the rate of degradation, $\mu_{p}^{cyt}$, of plus-strand RNA $R_{P}^{cyt}$. Furthermore, the distribution of $\mathcal{R}_0$ is between $[0.9999,\, 1.0008]$ with a mean of $\mathcal{R}_{0}=1.0003$.}}

Targeting Glutathione Metabolism: Partner in Crime in Anticancer Therapy

Glutathione (GSH) is the predominant low-molecular-weight antioxidant with a ubiquitous distribution inside the cell. The steady-state level of cellular GSH is dependent on the balance between synthesis, hydrolysis, recycling of glutathione disulphide (GSSG) as well as cellular extrusion of reduced, oxidized, or conjugated-forms. The augmented oxidative stress typical of cancer cells is accompanied by an increase of glutathione levels that confers them growth advantage and resistance to a number of chemotherapeutic agents. Targeting glutathione metabolism has been widely investigated for cancer treatment although GSH depletion as single therapeutic strategy has resulted largely ineffective if compared with combinatorial approaches. In this review, we circumstantiate the role of glutathione in tumour development and progression focusing on how interfering with different steps of glutathione metabolism can be exploited for therapeutic purposes. A dedicated section on synthetic lethal interactions with GSH modulators will highlight the promising option of harnessing glutathione metabolism for patient-directed therapy in cancer.

Does insulin signalling decide glucose levels in the fasting steady state?

Recent work has suggested that altered insulin signalling may not be central and as critical to the pathophysiology of type 2 diabetes as classically believed. We critically re-examine the role of insulin in glucose homeostasis using five different approaches namely (i) systematic review and meta-analysis of tissue specific insulin receptor knock-out experiments in rodents, (ii) systematic review and meta-analysis of insulin suppression and insulin enhancement experiments in rodents and humans, (iii) differentiating steady-state and post-meal state glucose levels in streptozotocin treated rats in primary experiments (iv) mathematical and theoretical considerations and (v) glucose insulin relationship in human epidemiological data. All the approaches converge on the inference that although insulin action is needed to reach a homeostatic steady-state of glucose in fasting condition, there is no evidence that insulin action determines the steady-state level of glucose. A wider scale implication of the analysis is in emphasizing the need to differentiate steady state causality from perturbed state causality or on a broader scale driver causality from navigator causality in biology. A driver cause is a factor which is necessary to attain a destination but does not by itself decide the destination. A navigator cause, on the other hand, is one which by itself may not be sufficient to drive the system to a destination but which plays a role in deciding the destination or direction. Insulin appears to be a driver but not a navigator for glucose homeostasis. All evidence suggests that insulin action is required for reaching a homeostatic steady state, but it does not determine the steady-state level of glucose.