**8. Applications: cell culture in drug discovery and screening**

#### **8.1 Drug candidate identification**

Often the rate-limiting step in preclinical drug discovery is the target identification and validation step. 3D cell cultures have the potential to discover the *Overview of Primary Cell Culture Models in Preclinical Research of Prostate and Bladder Cancer DOI: http://dx.doi.org/10.5772/intechopen.99493*

molecular perturbations governing carcinogenesis and to accelerate target identification and validation, given that the gene expression patterns found in 3D models are relative to in vivo, when compared to 2D monolayer models [81]. For instance, a study reported that CXCR7 (C-X-C chemokine receptor type 7) and CXCR4 (C-X-C chemokine receptor type 4) were co-expressed in LNCaP, DU145 and PC3 cell lines in 2D culture. A marked up-regulation of both receptors was observed in PC3 cells when cultured in 3D using Matrigel suggesting that inhibition of CXCR7/CXCR4 may assist in controlling prostate tumor growth and subsequent progression [82].
