Although several epidemiologic studies show an association between arsenic exposure and prostate cancer, it is still unknown whether human prostate epithelial cells are directly susceptible to arsenic-induced transformation. This study was designed to determine whether the nontumorigenic human prostate epithelial cell line RWPE-1 could be malignantly transformed in vitro by arsenite. RWPE-1 cells were continuously exposed to 5 micro M arsenite and monitored for signs of transformation, assessed as changes in matrix metalloproteinase-9 levels. After 29 weeks of exposure, the arsenite-exposed RWPE-1 cells (referred to as CAsE-PE) showed a marked increase in matrix metalloproteinase-9 secretion, a common finding in prostate malignancies. Malignant transformation was confirmed when CAsE-PE cells produced aggressive undifferentiated malignant epithelial tumors in nude mice. The tumors stained positive for human prostate-specific antigen, confirming their origin. These results are the first report of arsenite-induced malignant transformation of a human epithelial cell line and provide an important in vitro model for studying the mechanisms underlying arsenic-induced carcinogenesis in humans.

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Altered estrogen signaling may play a role in induction of HCC by arsenic exposure in utero. Specifically, overexpression of ER-alpha, potentially through promoter region hypomethylation, in livers of such mice may be linked to the hepatocarcinogenicity of arsenic.

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Metallothionein (MT) is a low-molecular-weight, sulfhydryl-rich, metal-binding protein that can protect against the toxicity of cadmium, mercury, and copper. However, the role of MT in arsenic (As)-induced toxicity is less certain. To better define the ability of MT to modify As toxicity, MT-I/II knockout (MT-null) mice and the corresponding wild-type mice (WT) were exposed to arsenite [As(III)] or arsenate [As(V)] either through the drinking water for 48 weeks, or through repeated sc injections (5 days/week) for 15 weeks. Chronic As exposure increased tissue MT concentrations (2-5-fold) in the WT but not in MT-null mice. Arsenic by both routes produced damage to the liver (fatty infiltration, inflammation, and focal necrosis) and kidney (tubular cell vacuolization, inflammatory cell infiltration, and interstitial fibrosis) in both MT-null and WT mice. However, in MT-null mice, the pathological lesions were more frequent and severe when compared to WT mice. This was confirmed biochemically, in that, at the higher oral doses of As, blood urea nitrogen (BUN) levels were increased more in MT-null mice (60%) than in WT mice (30%). Chronic As exposures produced 2-10 fold elevation of serum interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha levels, with greater increases seen by repeated injections than by oral exposure, and again, MT-null mice had higher serum cytokines than WT mice after As exposure. Repeated As injections also decreased hepatic glutathione (GSH) by 35%, but GSH-peroxidase and GSH-reductase were minimally affected. MT-null mice were more sensitive than WT mice to the effect of GSH depletion by As(V). Hepatic caspase-3 activity was increased (2-3-fold) in both WT and MT-null mice, indicative of apoptotic cell death. In summary, chronic inorganic As exposure produced injuries to multiple organs, and MT-null mice are generally more susceptible than WT mice to As-induced toxicity regardless of route of exposure, suggesting that MT could be a cellular factor in protecting against chronic As toxicity.

Defining an appropriate and efficient assessment of drug‐induced corrected QT interval (QTc) prolongation (a surrogate marker of torsades de pointes arrhythmia) remains a concern of drug developers and regulators worldwide. In use for over 15 years, the nonclinical International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) S7B and clinical ICH E14 guidances describe three core assays (S7B: in vitro hERG current & in vivo QTc studies; E14: thorough QT study) that are used to assess the potential of drugs to cause delayed ventricular repolarization. Incorporating these assays during nonclinical or human testing of novel compounds has led to a low prevalence of QTc‐prolonging drugs in clinical trials and no new drugs having been removed from the marketplace due to unexpected QTc prolongation. Despite this success, nonclinical evaluations of delayed repolarization still minimally influence ICH E14‐based strategies for assessing clinical QTc prolongation and defining proarrhythmic risk. In particular, the value of ICH S7B‐based “double‐negative” nonclinical findings (low risk for hERG block and in vivo QTc prolongation at relevant clinical exposures) is underappreciated. These nonclinical data have additional value in assessing the risk of clinical QTc prolongation when clinical evaluations are limited by heart rate changes, low drug exposures, or high‐dose safety considerations. The time has come to meaningfully merge nonclinical and clinical data to enable a more comprehensive, but flexible, clinical risk assessment strategy for QTc monitoring discussed in updated ICH E14 Questions and Answers. Implementing a fully integrated nonclinical/clinical risk assessment for compounds with double‐negative nonclinical findings in the context of a low prevalence of clinical QTc prolongation would relieve the burden of unnecessary clinical QTc studies and streamline drug development.

PEGylation (the covalent binding of one or more polyethylene glycol molecules to another molecule) is a technology frequently used to improve the half-life and other pharmaceutical or pharmacological properties of proteins, peptides, and aptamers. To date, 11 PEGylated biopharmaceuticals have been approved and there is indication that many more are in nonclinical or clinical development. Adverse effects seen with those in toxicology studies are mostly related to the active part of the drug molecule and not to polyethylene glycol (PEG). In 5 of the 11 approved and 10 of the 17 PEGylated biopharmaceuticals in a 2013 industry survey presented here, cellular vacuolation is histologically observed in toxicology studies in certain organs and tissues. No other effects attributed to PEG alone have been reported. Importantly, vacuolation, which occurs mainly in phagocytes, has not been linked with changes in organ function in these toxicology studies. This article was authored through collaborative efforts of industry toxicologists/nonclinical scientists to address the nonclinical safety of large PEG molecules (>10 kilo Dalton) in PEGylated biopharmaceuticals. The impact of the PEG molecule on overall nonclinical safety assessments of PEGylated biopharmaceuticals is discussed, and toxicological information from a 2013 industry survey on PEGylated biopharmaceuticals under development is summarized. Results will contribute to the database of toxicological information publicly available for PEG and PEGylated biopharmaceuticals.

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