Modeling breast cancer tumor morphology to predict drug response

Abstract

Proc Amer Assoc Cancer Res, Volume 46, 20055961 Previous investigators demonstrated that acquired drug resistance could be detected only in three-dimensional spheroids, rather than in monolayer cultures (Kobayashi et al. , 1993). Further, the resistant phenotype was associated with a distinct spheroid morphology. Treated spheroids were more compact than drug-naïve spheroids. These data suggest that intercellular interactions among constituents of solid tumors may have a profound impact on drug response, leading to the hypothesis that treatment response may be related to tumor morphology. We therefore set out to determine if tumor morphology in three-dimensional culture versus monolayer affected MCF-7 in vitro drug response. We compared the MDR-1 positive doxorubicin-resistant (DoxR) cell line with the Dox-sensitive wildtype strain. Our group has developed an in silico model of tumor growth, and a second objective of our study was to incorporate spheroid morphology into this model. We evaluated three-dimensional growth characteristics and P-glycoprotein expression in the DoxR and Dox-sensitive cell lines. P-Glycoprotein expression was assessed with immunohistochemistry using JSB-1 antibody. Morphology was evaluated with phase contrast microscopy. In vitro drug response to doxorubicin was determined by hemocytometer trypan blue cell counts. For in silico modeling we used a multi-scale and multi-dimensional tumor simulator to model tumor morphological characteristics that were predictive of drug response. Model parameters were extended to include in vitro tumor morphology and P-glycoprotein expression. Three-dimensional spheroids of MCF-7 DoxR cells were found to have a more compact morphology than MCF-7 Dox-sensitive cells. P-Glycoprotein staining was observed in DoxR spheroids and monolayers, while Dox-sensitive cells lacked P-glycoprotein expression. For both drug-resistant and drug-sensitive cell lines, viability was approximately two-fold greater in spheroids as compared to monolayer culture when treated with 4μM doxorubicin. In silico simulations of tumor growth were able to predict higher drug resistance in compact versus diffuse spheroids. Compactness was measured as the ratio of surface area to volume. We developed an iterative translational technique to model tumor growth and response to therapy to answer the question of how morphology and structure of tissue may affect drug response. The three-dimensional morphology of MCF-7 in vitro culture…