Tackling the tumor microenvironment – how can complex tumor models in vitro aid oncology drug development?

Introduction Identifying effective cancer drugs remains an inefficient process. Drug efficacy in traditional preclinical cancer models translates poorly into therapy in the clinic. Implementation of preclinical models that incorporate the tumor microenvironment (TME) is needed to improve selection of active drugs prior to clinical trials.Areas covered Progression of cancer results from the behavior of cancer cells in concert with the host's histopathological background. Nonetheless, complex preclinical models with a relevant microenvironment have yet to become an integral part of drug development. This review discusses existing models and provides a synopsis of active areas of cancer drug development where implementation would be of value. Their contribution to finding therapeutics in immune oncology, angiogenesis, regulated cell death and targeting tumor fibroblasts as well as optimization of drug delivery, combination therapy, and biomarkers of efficacy is considered.Expert opinion Complex tumor models in vitro (CTMIVs) that mimic the organotypic architecture of neoplastic tumors have boosted research into TME influence on traditional cytoreductive chemotherapy as well as the detection of specific TME targets. Despite advances in technical prowess, CTMIVs can only address specific aspects of cancer pathophysiology.