(P 284) VALIDATING A NOVEL MICROFLUIDIC PLATFORM AS AN EX VIVO TUMOUR MODEL FOR SARCOMA DRUG DISCOVERY

Objective:

Background:
Sarcomas are a rare and heterogeneous group of mesenchymal cancers characterized by more than 70 distinct subtypes. In the near 25–50% of sarcoma patients that develop metastatic disease, the median survival is around 15–20 months, in part due to a low response rate to traditional systemic therapies. More recently, the immune microenvironments of various sarcoma subtypes have been identified as an important factor in their growth and metastatic activity, presenting researchers with new potential targets for therapeutic drugs. However, the current cancer drug development pipeline is hindered by the limitations of preclinical models to correctly predict clinical outcomes in patients. This is partly due to the inability of cell cultures and mouse models to fully recapitulate the microenvironment of human tumours. Additionally, due to high patient-to-patient variability of sarcoma diagnoses, there is a desperate need for a new patient-specific drug-testing tool to guide the choice of therapy in the clinic. A potential solution to this problem is a tumour-on-chip platform that uses microfluidics to culture sub-millimetre micro-dissections of patient-derived tumours (MDTs). Unlike other ex vivo tissue culture methods, this microfluidic platform can keep MDTs viable for up to 15 days, which is a suitable timeline for most drug-testing assays. Furthermore, each device can house up to 32 MDTs in four different channels, allowing for high-throughput parallel testing of different treatment conditions within the same device. So far, this platform has been tested on several different cancer types, but has yet to be validated for soft-tissue sarcoma. At Mount Sinai Hospital, our research team has access to the largest sarcoma reference in Canada, with surgically resected tumours being available to us on a weekly basis. As a result, we are in a unique position to validate this platform for a variety of sarcoma subtypes.

Methods: HYPOTHESIS AND

Objectives:
It is hypothesized that the MDT-on-chip device is a representative ex vivo model of sarcoma tumours. To evaluate this hypothesis, we will: 1) assess the viability and genetic composition of sarcoma MDTs within the device over time; 2) examine the ability of MDTs to recapitulate the immune microenvironment of the source tumour.

Results: ONGOING AND UPCOMING EXPERIMENTS:
1) ONGOING: to examine how long sarcoma MDTs can be cultured in the device, samples will be stained using live/dead fluorescent dyes and imaged via confocal microscopy at several time-points over a 15-day period. The resulting z-stack images will then be analyzed to quantify the ratio of live-stained cells over total stained cells, which will serve as a measure of viability. Furthermore, whole-exome sequencing will be used to measure changes in the genomic composition of MDTs over time with respect to the source tumour. This analysis will identify how long the MDTs can be cultured in the device before experiencing genetic drift. 2) UPCOMING: an immune profile of the MDTs will be defined using immunohistochemistry and immune cell deconvolution analysis of RNA sequencing data. The relative abundance of T cells, B cells, natural killer cells, dendritic cells and macrophages will be compared to that of the source tumour to examine the ability of MDTs to recapitulate its immune microenvironment. An emphasis will be placed on tumour-associated macrophages (TAMs), as they have been identified as a major immune component of various sarcoma subtypes, and are a target-of-interest for immunotherapy development in our lab. To that effect, a functional assay will be performed on the MDTs to evaluate the phenotype of TAMs in response to stimulation at various time-points within the device.

Conclusion: SIGNIFICANCE OF STUDY:
If proven to be a representative model of the patient tumour, the MDT-on-chip platform could greatly benefit the drug discovery pipeline of sarcoma by offering a high throughput method for personalized testing in both the lab and the clinic.