Abstract 5834: Serum induces differentiation in aggressive MYCN-amplified neuroblastoma patient-derived xenograft cells
Authors: Persson Camilla U. , Stedingk Kristoffer von , Bexell Daniel , Merselius My , Gisselsson David , Beckman Siv , Mohlin Sofie , Påhlman Sven , Wigerup Caroline 
Published: July 2017

Abstract
Background: Cancer cell lines have traditionally been established in serum-containing medium though it has been questioned whether serum-grown cell lines faithfully represent the tumors they are derived from. Potential serum-induced differentiation of in vitro cultured cells could partly explain why xenografted cell lines often lack invasive growth and robust metastasis. Direct implantation of patient tumor material into mice, i.e. patient derived xenografts (PDXs), has shown to more closely mimic the original tumor growth pattern. By isolating cells from neuroblastoma PDXs and culturing the PDX cells under serum-free conditions, we expect to preserve a less differentiated phenotype, enabling us to use PDX cells as a source for identifying potential neuroblastoma stem-like cells. Moreover, to facilitate future drug screening, we investigated conditions that would allow us to grow neuroblastoma PDX cells adherently, without compromising their tumorigenic or metastatic capacity.
Materials & Methods: PDX cells were cultured in stem cell medium or serum-containing medium for up to 7 days. IHC, RT-qPCR and WB were used to investigate the expression of sympathetic neuronal differentiation markers. For monolayer culture, cells were grown on laminin.
Results: PDX cells can routinely be established as neurospheres in serum-free medium with retained tumorigenic and metastatic capacity. Addition of serum induces loss of sphere formation, adherent growth and a robust increase in sympathetic differentiation markers, both at mRNA and protein level. Serum-cultured cells also show a decreased cell proliferation (without increased apoptotic rate, as determined by sub-G0/G1 analyses). The serum-induced differentiation was not irreversible since transferring serum-grown cells back to serum-free medium resulted in a phenotypic switch, with recovered proliferation and decreased expression of differentiation markers. Growing cells on laminin achieved adherent culture of PDX cells. This resulted only in slight morphological differentiation but did not affect growth rate or the cells tumorigenic and metastatic capacity.
Conclusion: Culturing neuroblastoma PDX cells in serum-containing medium results in a more differentiated phenotype. Thus, avoiding serum appears to be a key strategy in order to preserve the phenotypic origin of these cells. The phenotypic effects of serum on tumor cells have largely been overlooked and might be a general effect on tumor cells explaining why serum-established cell lines do not metastasize and grow invasively.
Citation Format: Camilla U. Persson, Kristoffer von Stedingk, Daniel Bexell, My Merselius, David Gisselsson, Siv Beckman, Sofie Mohlin, Sven Påhlman, Caroline Wigerup. Serum induces differentiation in aggressive MYCN-amplified neuroblastoma patient-derived xenograft cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5834. doi:10.1158/1538-7445.AM2017-5834