In silico approaches in carcinogenicity hazard assessment: case study of pregabalin, a nongenotoxic mouse carcinogen

Abstract

In silico toxicology protocols are meant to support computationally-based assessments using principles that ensure that results can be generated, recorded, communicated, archived, and then evaluated in a uniform, consistent, and reproducible manner. We investigated the availability of in silico models to predict the carcinogenic potential of pregabalin using the ten key characteristics of carcinogens as a framework for organizing mechanistic studies. Pregabalin is a single-species carcinogen producing only one type of tumor, hemangiosarcomas in mice via a nongenotoxic mechanism. The overall goal of this exercise is to test the ability of in silico models to predict nongenotoxic carcinogenicity with pregabalin as a case study. The established mode of action (MOA) of pregabalin is triggered by tissue hypoxia, leading to oxidative stress (KC5), chronic inflammation (KC6), and increased cell proliferation (KC10) of endothelial cells. Of these KCs, in silico models are available only for selected endpoints in KC5, limiting the usefulness of computational tools in prediction of pregabalin carcinogenicity. KC1 (electrophilicity), KC2 (genotoxicity), and KC8 (receptor-mediated effects), for which predictive in silico models exist, do not play a role in this mode of action. Confidence in the overall assessments is considered to be medium to high for KCs 1, 2, 5, 6, 7 (immune system effects), 8, and 10 (cell proliferation), largely due to the high-quality experimental data. In order to move away from dependence on animal data, development of reliable in silico models for prediction of oxidative stress, chronic inflammation, immunosuppression, and cell proliferation will be critical for the ability to predict nongenotoxic compound carcinogenicity.

Keywords: In silico toxicology protocol; cell proliferation; chronic inflammation; mode of action; non-genotoxic carcinogen; oxidative stress; pregabalin.

FIGURE 1

Chemical structure of pregabalin.

FIGURE 2

The in silico assessments most relevant to genotoxicity are combined with available experimental data according to the genetic toxicology in silico protocol (Hasselgren, et al., 2019). Selected models and corresponding reliability scores are shown in the figure. The details of available predictions are reported in the Supplementary Material. The reliability score (RS) of each prediction is documented in the Supplementary Material. This is used to derive the overall endpoint confidence (Myatt, et al., 2018; Johnson, et al., 2022) based on the published rules (Hasselgren, et al., 2019).

FIGURE 3

Interactions among the 10 KCs and with the Three Stages of Carcinogenesis. KC1 = is electrophilic, KC2 = is genotoxic, KC3 = alters DNA repair or causes genomic instability, KC4 = induces epigenetic alterations, KC5 = induces oxidative stress, KC6 = induces chronic inflammation, KC7 = is immunosuppressive, KC8 = modulates receptor-mediated effects, KC9 = causes immortalization, KC10 = alters cell proliferation, cell death, or nutrient supply. Specific evidence for involvement in pregabalin carcinogenicity is highlighted in red.