Pharmacodynamic Models of Differential Bortezomib Signaling Across Several Cell Lines of Multiple Myeloma

Cytotoxic and Apoptotic Effects of Pinostilbene and Bortezomib Combination Treatment on Human Multiple Myeloma Cells

Multiple myeloma (MM) is a cancer of plasma cells in the bone marrow characterized by bone lesions, hypercalcemia, anemia, and renal failure. Bortezomib (BTZ), a common treatment for MM, is a proteasome inhibitor that induces apoptosis in MM cells. However, high doses of BTZ can be very toxic, signifying a need for a synergistic drug combination to improve treatment efficacy. Resveratrol (RES), a phenolic compound found in grapes, has been shown to inhibit MM cell growth. We sought to identify a synergistic combination of BTZ with a RES derivative and analyze the effects on reducing viability and inducing apoptosis in human MM cells. BTZ as well as RES and its derivatives pinostilbene (PIN) and piceatannol (PIC) decreased MM cell viability in a dose- and time-dependent manner and increased expression of cleaved proapoptotic proteins poly(ADP-ribose) polymerase 1 (PARP1) and caspase-3 in a dose-dependent manner. The combination of 5 nM BTZ and 5 μM PIN was identified to have synergistic cytotoxic effects in MM RPMI 8226 cells. MM RPMI 8226 cells treated with this combination for 24 h showed increased cleaved PARP1 and caspase-3 expression and higher percentages of apoptotic cells versus cells treated with the individual compounds alone. The treatment also showed increased apoptosis induction in MM RPMI 8226 cells co-cultured with human bone marrow stromal HS-5 cells in a Transwell model used to mimic the bone marrow microenvironment. Expression of oxidative stress defense proteins (catalase, thioredoxin, and superoxide dismutase) in RPMI 8226 cells were reduced after 24 h treatment, and cytotoxic effects of the treatment were ameliorated by antioxidant N-acetylcysteine (NAC), suggesting the treatment impacts antioxidant levels in RPMI 8226 cells. Our results suggest that this combination of BTZ and PIN decreases MM cell viability synergistically by inducing apoptosis and oxidative stress in MM cells.

Cluster Gauss-Newton and CellNOpt Parameter Estimation in a Small Protein Signaling Network of Vorinostat and Bortezomib Pharmacodynamics

Ordinary differential equation (ODE)-based models of signal transduction pathways often contain parameters that are unidentifiable or unmeasurable by experimental data, and calibrating such models to data remains challenging. Here, two efficient parameter estimation methods, cluster Gauss-Newton (CGN) and CellNOpt (CNO), were applied to fit a signaling network model of U266 multiple myeloma cells to the activity dynamics of key proteins in response to vorinostat and/or bortezomib. A logic-based network model was constructed and transformed to 17 ODEs with 79 parameters estimated within broad ranges of biologically plausible values. The top 10% best-fit parameters by both methods had high uncertainties with CV > 50% for the majority of parameters. The root mean square and prediction errors were comparable without statistically significant differences between the two methods. Despite uncertain parameter estimation, protein dynamics after the sequential combination of bortezomib and vorinostat was predicted with reasonable accuracy and precision. Global sensitivity analyses of partial rank correlation coefficients and Sobol sensitivity demonstrated that apoptosis induction was most sensitive to parameters governing the activity of the proteasome-JNK-caspase-8 axis. Simulations revealed that the greatest magnitude of pharmacodynamic drug interactions between bortezomib and vorinostat occurred at caspase-9, AKT, and Bcl-2. Two sequential combinations were explored in silico, and the outcome matched qualitatively with an empirical evaluation of the pharmacodynamic interaction based on cell viability. Overall, the CGN and CNO algorithms performed similarly for this ODE-based network model calibration, and the calibrated model provided meaningful insights into cellular signaling mechanisms in response to pharmacological perturbations.

A quantitative systems pharmacological approach identified activation of JNK signaling pathway as a promising treatment strategy for refractory HER2 positive breast cancer

HER2-positive breast cancer (BC) is a rapidly growing and aggressive BC subtype that predominantly affects younger women. Despite improvements in patient outcomes with anti-HER2 therapy, primary and/or acquired resistance remain a major clinical challenge. Here, we sought to use a quantitative systems pharmacological (QSP) approach to evaluate the efficacy of lapatinib (LAP), abemaciclib (ABE) and 5-fluorouracil (5-FU) mono- and combination therapies in JIMT-1 cells, a HER2+ BC cell line exhibiting intrinsic resistance to trastuzumab. Concentration-response relationships and temporal profiles of cellular viability were assessed upon exposure to single agents and their combinations. To quantify the nature and intensity of drug-drug interactions, pharmacodynamic cellular response models were generated, to characterize single agent and combination time course data. Temporal changes in cell-cycle phase distributions, intracellular protein signaling, and JIMT-1 cellular viability were quantified, and a systems-based protein signaling network model was developed, integrating  protein dynamics to drive the observed changes in cell viability. Global sensitivity analyses for each treatment arm were performed, to identify the most influential parameters governing cellular responses. Our QSP model was able to adequately characterize protein dynamic and cellular viability trends following single and combination drug exposure. Moreover, the model and subsequent sensitivity analyses suggest that the  activation of the stress pathway, through pJNK, has the greatest impact over the observed declines of JIMT-1 cell viability in vitro. These findings suggest that dual HER2 and CDK 4/6 inhibition may be a promising novel treatment strategy for refractory HER2+ BC, however, proof-of-concept in vivo studies are needed to further evaluate the combined use of these therapies.

Modeling Corticosteroid Pharmacokinetics and Pharmacodynamics, Part III: Estrous Cycle and Estrogen Receptor-Dependent Antagonism of Glucocorticoid-Induced Leucine Zipper (GILZ) Enhancement by Corticosteroids

Our previous report examined the pharmacokinetics (PK) of methylprednisolone (MPL) and adrenal suppression after a 50 mg/kg IM bolus in male and female rats, and we described in detail the development of a minimal physiologically based pharmacokinetic/pharmacodynamic (mPBPK/PD) model. In continuation of such assessments, we investigated sex differences in genomic MPL responses (PD). Message expression of the glucocorticoid-induced leucine zipper (GILZ) was chosen as a multitissue biomarker of glucocorticoid receptor (GR)-mediated drug response. Potential time-dependent interplay between sex hormone and glucocorticoid signaling in vivo was assessed by comparing the enhancement of GILZ by MPL in the uterus [high estrogen receptor (ER) density] and in liver (lower ER density) from male and female rats dosed within the proestrus (high estradiol/progesterone) and estrus (low estradiol/progesterone) phases of the rodent estrous cycle. An expanded-systems PD model of MPL considering circadian rhythms, multireceptor (ER and GR) control, and estrous variations delineated the determinants controlling receptor/gene-mediated steroid responses. Hepatic GILZ response was ∼3-fold greater in females, regardless of estrous stage, compared with males, driven predominantly by increased MPL exposure in females and a negligible influence of estrogen interaction. In contrast, GILZ response in the uterus during proestrus in females was 60% of that observed in estrus-phased females, despite no PK or receptor differences, providing in vivo support to the hypothesis of estrogen-mediated antagonism of glucocorticoid signaling. The developed model offers a mechanistic platform to assess the determinants of sex and tissue specificity in corticosteroid actions and, in turn, reveals a unique PD drug-hormone interaction occurring in vivo. SIGNIFICANCE STATEMENT: Mechanisms relating to sex-based pharmacodynamic variability in genomic responses to corticosteroids have been unclear. Using combined experimental and systems pharmacology modeling approaches, sex differences in both pharmacokinetic and pharmacodynamic mechanisms controlling the enhancement of a sensitive corticosteroid-regulated biomarker, the glucocorticoid-induced leucine zipper (GILZ), were clarified in vivo. The multiscale minimal physiologically based pharmacokinetics/pharmacodynamic model successfully captured the experimental observations and quantitatively discerned the roles of the rodent estrous cycle (hormonal variation) and tissue specificity in mediating the antagonistic coregulation of GILZ gene synthesis. These findings collectively support the hypothesis that estrogens antagonize pharmacodynamic signaling of genomic corticosteroid actions in vivo in a time- and estrogen receptor-dependent manner.