All-human microphysical model of metastasis therapy

Abstract

The vast majority of cancer mortalities result from distant metastases. The metastatic microenvironment provides unique protection to ectopic tumors as the primary tumors often respond to specific agents. Although significant interventional progress has been made on primary tumors, the lack of relevant accessible model in vitro systems in which to study metastases has plagued metastatic therapeutic development - particularly among micrometastases. A real-time, all-human model of metastatic seeding and cancer cells that recapitulate metastatic growth and can be probed in real time by a variety of measures and challenges would provide a critical window into the pathophysiology of metastasis and pharmacology of metastatic tumor resistance. To achieve this we are advancing our microscale bioreactor that incorporates human hepatocytes, human nonparenchymal liver cells, and human breast cancer cells to mimic the hepatic niche in three dimensions with functional tissue. This bioreactor is instrumented with oxygen sensors, micropumps capable of generating diurnally varying profiles of nutrients and hormones, while enabling real-time sampling. Since the liver is a major metastatic site for a wide variety of carcinomas and other tumors, this bioreactor uniquely allows us to more accurately recreate the human metastatic microenvironment and probe the paracrine effects between the liver parenchyma and metastatic cells. Further, as the liver is the principal site of xenobiotic metabolism, this reactor will help us investigate the chemotherapeutic response within a metabolically challenged liver microenvironment. This model is anticipated to yield markers of metastatic behavior and pharmacologic metabolism that will enable better clinical monitoring, and will guide the design of clinical studies to understand drug efficacy and safety in cancer therapeutics. This highly instrumented bioreactor format, hosting a growing tumor within a microenvironment and monitoring its responses, is readily transferable to other organs, giving this work impact beyond the liver.

Liver metastases: Microenvironments andex-vivomodels

“…In response to these limitations, bioengineers and cell biologists have joined forces to develop a new generation of tissue-engineered biomimetic systems (106–110). These systems are quickly becoming an attractive alternative and/or complement to the traditional 2D and murine models.…”

“…Desirable features include: (i) inclusion of all resident hepatic cells necessary for liver functioning (hepatocytes and the various NPCs), (ii) controllable flow to provide the physiologically relevant perfusion shear stimulation, oxygenation, nutrients replenishment, waste product removal and extended culture periods, (iii) scaffolding or matrices that support a 3D multicellular microenvironment by encouraging cell self-organization and generation of macroscopic tissue morphology, and (iv) the ability to be assayed for a variety of real-time mechanistic readouts (e.g. genomic, phenotypic, mass spectroscopy, cell biochemical, and media secretion-based assays) (106–108, 110, 113, 114). The technologies and fabrication techniques are developing fast (107, 115), and although each system described below captures many of the features of liver (Table 1), it is unlikely that a single ex vivo model of liver will meet all the requirements for all applications of liver biology in research and industry.…”

“…The system is limited in terms of imaging capabilities as the optical windows of earlier (118) were traded for enhanced throughput, with only endpoint analyses presently permitted. Importantly for this discussion, this MPS is the only one fully validated for the study of metastatic behavior (110, 116, 119). …”

Modelling the metastatic cascade by in vitro microfluidic platforms

“…The effluent samples during the incubation and the cells themselves after the completion of the experiment are analyzed for the presence of particular marker proteins (soluble aspartate transaminase and alanine aminotransferase, P450 cytochromes, desmin etc). This platform was also adopted for screening for the chemotherapeutic response for micrometastases treatment (Wheeler et al, 2013).…”

Tissue-engineered models of human tumors for cancer research

“…Recently, a human model of breast cancer metastasis into liver was established by engineering liver tumor organoids from human hepatocytes and human nonparenchymal liver cells [47]. The microfluidic platform maintained viability of tumor organoids by using micropumps coupled to oxygen sensors to generate diurnal profiles of nutrients and hormones.…”