Characterization of Autocrine Growth Factors, Their Receptors and Extracellular Matrix Present in Three-Dimensional Cultures of DU 145 Human Prostate Carcinoma Cells Grown in Simulated Microgravity

Abstract

This study provides insight into mechanisms regulating growth of androgen-independent prostatic tumors. To this end, we characterized select regulatory and matrix proteins in aggregates of DU 145 human prostate carcinoma cells grown in simulated microgravity within the high aspect rotating-wall vessel (HARV), spinner flask and Transwell insert. For HARV cultures, three-dimensional growth and doubling times were three and 1.5 times greater, respectively, than for Transwell cultures. By day 17, the ratio of staining intensity for the HARV to that for the Transwell was 0.15 for epidermal growth factor (EGF), 0.52 for EGF receptor, 1.2 for transforming growth factor β1 (TGF-β1), 0.17 for TGF-β receptor, 3.7 for collagen IV and 2.4 for laminin. Spinner-flask cultures had doubling times identical to HARV cultures but less three-dimensional growth. Their staining intensities often resembled those for Transwell cultures. Changes in three-dimensional growth and turbulence most likely contributed to differences in culture performance. Probably, these differences were mediated in part through EGF and TGF-β1 autocrine loops and cell–matrix interactions. We discuss the possibility of the HARV culture being the least aggressive in this study. Also discussed is the analogy of HARV cultures behaving as a differentiated solid tumor; and Transwell cultures as an aggressive, invading tumor margin.